JPH1097753A - Optical head, tilt detector and optical information processor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stabilize a servo characteristics, write-in operation and erase the operation by preventing a phase shift of a tracking error signal. SOLUTION: A photodetector 150 is divided into detection areas 201-208 by division lines 301-304. An overlapped area 200 is provided on first and +1st diffracted light diffracted by a groove on an optical disk. Then, an adder 405 receives outputs of the adders 401-404, and outputs an information regenerative signal RF of total sum of signals s1-s8 answering to light received light quantities from the area 201-208. Further, a differential operation circuit 406 receives the outputs of the adders 401, 404 to output their differential signal TE. When a tilt occurs on the disk 111 the direction orthogonally intersecting with the tangent of the optical disk groove, an offtrack amount for a track center when the tilt occurs is suppressed by taking the signal TE from the signals s1, s2, s5, s8 of the outside of the area 200 of +1st, -1st diffracted light, and by correcting this to zero, the shift in the symmetry of the tracking error signal is suppressed to 2/3 of usual.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical head device for recording / reproducing or erasing information on an information storage medium such as an optical disk or an optical card, an optical information processing device, and a condensing optical system in the device. The present invention relates to a tilt detection device that detects an angle between a light beam and an information storage medium.

[0002]

2. Description of the Related Art As a high-density, large-capacity information storage medium,
An optical disk or an optical card is used. In an optical memory technology using an optical disk or an optical card, applications thereof such as a digital audio disk, a video disk, a document file disk, and a data file are expanding. In this optical memory technology, information is recorded and reproduced with high precision and reliability on an optical disk via a light beam that is narrowed down minutely. This recording / reproducing operation depends solely on the optical system.

The basic functions of an optical head device, which is a main part of the optical system, include (1) light focusing for forming a diffraction-limited minute spot, (2) focus control and tracking control of the optical system, and information. Signal reproduction is broadly divided into (3) erasing and writing of information signals by concentration of light.

[0004] These functions are realized by a combination of various optical systems and a photoelectric conversion detection type photodetector according to the purpose and application.

As a first conventional example, an example of a conventional optical head device will be described.

As a conventional example of an optical head device, a configuration and an operation in a case where an astigmatism method is used for focusing and a push-pull method and a phase difference method are used for tracking will be described. FIG. 42 is a schematic diagram of an optical system of the optical head device.

FIG. 42 schematically shows the optical system of the optical head device according to the first embodiment.

Light emitted from a semiconductor laser 101 as a light source is reflected by a parallel plate beam splitter 102 and becomes parallel light by a collimator lens 103 which is a part of a condensing optical system. This light is further condensed by an objective lens 104 which is a part of a condensing optical system, and condensed on an information layer 108 of an optical disk 105 which is an information storage medium. The actuator 107 moves the objective lens 104 and the holding means 106 in accordance with the runout and eccentricity of the optical disk 105.

[0009] Diffraction by the information layer 108 of the optical disc 105
The reflected light 108a that has been reflected passes through the objective lens 104 again and becomes parallel light. The reflected light 108a that has become this parallel light
Becomes convergent light again by the collimator lens 103. When the converged reflected light 108a passes through the parallel plate beam splitter 102, astigmatism is given. The convergent light provided with astigmatism is received by the photodetector 150. Focus point F0 of light emitted from objective lens 104
The optical system is arranged so that the detection surface of the photodetector 150 is located at the position of the circle of least confusion of the convergent light given astigmatism when the light beam coincides with the information layer 108 of the optical disk 105.

FIG. 43A shows a conventional pattern of a detection area of the photodetector 150 and a cross-sectional shape of the reflected light 108a by the photodetector 150. The photodetector 150 includes four detection areas 251 to 254. Signals obtained according to the amounts of light received from the detection areas 251 to 254 are s1 to s, respectively.
4 is assumed. Although an arithmetic circuit as a tracking error signal generating means is not shown, a tracking error signal is generated as the tracking error signal TE1 by the following equation: TE1 = (s1 + s4)-(s2 + s3) (Equation 1).

Also, a tracking error signal T of the phase difference method is used.
E2 is obtained by comparing the phase of the sum signal of s1 and s3 with the phase of the sum signal of s2 and s4.

The focus error signal FE in the astigmatism method is obtained from FE = (s1 + s3)-(s2 + s4) (Equation 2).

When the information layer 108 of the optical disk 105 moves away from the objective lens 104 from the focal point F0 of the light emitted from the objective lens 104, the cross-sectional shape of the reflected light 108a by the photodetector 150 is as shown in FIG. It takes shape. Conversely, when the information layer 108 of the optical disk 105 approaches the objective lens 104 from the focal point F0 of the objective lens 104, the cross-sectional shape of the reflected light 108a by the photodetector 150 becomes as shown in FIG. 43c.

The RF signal, which is an information reproduction signal, is a sum of signals obtained from all regions, and is obtained from RF = s1 + s2 + s3 + s4 (Equation 3).

In the conventional optical head device shown in the first conventional example, (1) a tracking error signal is generated by a differential signal in an area simply divided into two by a dividing line passing through a point corresponding to the center of the opening. ing. In this configuration, when an aberration occurs due to the inclination between the objective lens and the optical disk (when tilt occurs), or when the objective lens moves in a direction perpendicular to the track with respect to the optical axis following the eccentricity of the optical disk (object lens) However, there is a problem that off-track occurs and tracking control does not operate stably.

(2) Further, when scanning the position where the focal point of the light emitted from the objective lens is shifted from the track on which the information to be reproduced is recorded, a dividing line passing through a point corresponding to the center of the opening is used. When a reproduced signal is generated by the differential signals in the divided areas, there is a problem that a sufficient margin for disturbance or the like cannot be obtained.

Also, there is provided a tilt detecting device for detecting a relative tilt amount between a beam condensed by a condensing optical system in an optical information device and an information storage medium in order to accurately read and write information on the information storage medium. Various configurations have been proposed.

Next, an example of a tilt detecting device will be described as a second conventional example.

FIG. 44 is a block diagram showing an example of a conventional inclination detecting device.

A linearly polarized divergent beam 70 emitted from a semiconductor laser 101 as a light source is
03, is converted into parallel light, and then the polarization beam splitter 1
It is incident on 30. All the beams 70 incident on the polarization beam splitter 130 pass through the polarization beam splitter 130, pass through the 波長 wavelength plate 122, are converted into circularly polarized beams, and are condensed on the information storage medium 105 by the objective lens 104. Is done.

FIG. 45 shows the configuration of the information storage medium 105. Gn-1, Gn, Gn + 1,... Are guide grooves. Information is recorded as a mark or space on the guide groove. Therefore, the track Tn for recording information is
-1, Tn, Tn + 1,... Coincide with the guide grooves.
Gp is the interval between adjacent guide grooves, tp is the interval between adjacent tracks, and Gp and tp are equal. The beam 70 reflected and diffracted by the information storage medium 105 passes through the objective lens 104 again, passes through the quarter-wave plate 122, and is a linearly polarized beam having a direction different from that when emitted from the light source 101 by 90 degrees. Is converted to The beam 70 transmitted through the 波長 wavelength plate 122 is totally reflected by the polarization beam splitter 130, and then converted into a convergent beam by the detection lens 133. Convergent beam 70 converted by detection lens 133
Are transmitted through the parallel plate 134 and received by the photodetector 158. When the beam 70 passes through the parallel plate 134, the astigmatism is reduced to detect the focus error signal.
Is given to The beam 70 received by the photodetector 158 is converted into an electric signal corresponding to the light amount.

In this specification, the optical disk is a ROM
In the case of a disc, a mark means a pit, a space means a plane portion, and when an optical disc is a phase change storage medium, a mark means an amorphous portion, a space means a crystal portion, or conversely, The mark means a crystal part, and the space means an amorphous part. Alternatively, when the optical disk is a magnetic storage medium, the mark may mean upward magnetization and the space may mean downward magnetization, or conversely, the mark may mean downward magnetization and the space may mean upward magnetization. Further, when the optical disk is a magnetic storage medium, the mark may mean rightward magnetization, the space may mean leftward magnetization, or conversely, the mark may mean leftward magnetization and the space may mean rightward magnetization. When the optical disk is a write-once optical disk such as a CD-R, the mark means a dye-modified area and the space means a non-modified area.

The focus error signal and the tracking error signal are applied to focus control and tracking control actuators 107, respectively, so that the beam 70 emitted from the light source 101 is focused on a desired position on the information storage medium 105. The position of the objective lens 104 is controlled.
Since the method of generating the focus error signal and the tracking error signal is a well-known method, the description is omitted here.

The electric signal output from the photodetector 158 is input to a signal processing unit 703.

FIG. 46 shows the structure of the signal processing unit 703.
The photodetector 158 has four light receiving sections 158A, 158B, 1
58C and 158D. Light receiving units 158A to 158D
Are converted by the current-to-voltage converters 855 to 858, respectively. Current-to-voltage converter 855
The signal output from 858 is subjected to a differential operation by the operation unit 871. The signal output from the arithmetic unit 871 is supplied to a terminal 814
Output from The signal output from the terminal 814 is the inclination detection signal.

In the conventional tilt detecting device as shown in the second conventional example, when the tilt is detected by utilizing the fact that the beam reflected by the information storage medium is shaken at the opening of the objective lens 104, the objective lens is used. The higher the numerical aperture of 104, the lower the detection sensitivity. In recent years, in order to record a large amount of information on an information storage medium, a configuration has been proposed in which the numerical aperture of the condensing optical system is 0.6 and the thickness of the substrate of the information storage medium is 0.6 mm. Even if the angle formed between the beam focused by the objective lens and the information storage medium changes by only about 0.5 degrees, the jitter characteristic of the read information changes significantly.
Therefore, when introducing a tilt servo for correcting a change in the angle formed between the beam focused by the objective lens and the information storage medium, the tilt detection device needs to detect with an accuracy of 0.5 degrees or less. However, in the conventional tilt detection device, when the numerical aperture of the objective lens is 0.6, for example, even if the tilt is 0.5 degrees, the signal change is only about 2%, and the tilt is 0.5 degrees or less. However, there is a problem that it is difficult to detect with high accuracy.

Further, as a third conventional example, another example of an optical head device will be described.

FIG. 47 is a configuration diagram showing an example of a conventional optical head device.

A linearly polarized divergent beam 70 emitted from a semiconductor laser 101 as a light source is
03, is converted into parallel light, and then the polarization beam splitter 1
It is incident on 30. All the beams 70 incident on the polarization beam splitter 130 pass through the polarization beam splitter 130, pass through the 波長 wavelength plate 122, are converted into circularly polarized beams, and are condensed on the information storage medium 105 by the objective lens 104. Is done. The beam 70 reflected and diffracted by the information storage medium 105 passes through the objective lens 104 again, and
The light is converted into a linearly polarized beam having a direction different from that of the light emitted from the light source 101 through the 波長 wavelength plate 122 by 90 degrees. The beam 70 transmitted through the 波長 wavelength plate 122 is totally reflected by the polarization beam splitter 130, and then converted into a convergent beam by the detection lens 133. Detection lens 133
The convergent beam 70 converted by the above is transmitted through the parallel flat plate 134 and received by the photodetector 158. When the beam 70 passes through the parallel plate 134, astigmatism is given to the beam 70 so that a focus error signal can be detected. The beam 70 received by the photodetector 158 is converted into an electric signal corresponding to the light amount.

The electric signal output from the photodetector 158 is input to a signal processing unit 705. FIG. 48 shows the configuration of the signal processing unit 705. The light detector 158 includes four light receiving sections 158A, 158B, 158C, and 158D. The signals output from the light receiving units 158A to 158D are subjected to current / voltage conversion by current / voltage conversion units 851 to 854, respectively.
The signals output from the current / voltage converters 851 and 854 are output by an adder 891, and the signals output from the current / voltage converters 852 and 853 are output by an adder 892.
The signal output from the output unit 853 is an addition unit 893, and the signal output from the current / voltage conversion units 852 and 854 is an addition unit 893.
4 respectively. The signals output from the adders 891 and 892 are output from the arithmetic unit 871 to the adders 893 and 89.
The signals output from 4 are subjected to differential operation by the operation unit 872, respectively. The signal output from the arithmetic unit 871 is connected to the terminal 8
11, the signal output from the operation unit 872 is
2 respectively. The signal output from the terminal 811 is a tracking error signal, and the signal output from the terminal 812 is a focus error signal. The method of generating the focus error signal is a method well known as the astigmatism method, and the method of generating the tracking error signal is a method well known as the push-pull method. The focus error signal and the tracking error signal are respectively applied to focus control and tracking control actuators 107, and the objective lens 104 is focused so that the beam 70 emitted from the light source 101 is focused on a desired position on the information storage medium 105. Control the position of.

FIG. 49 shows a configuration on the information storage medium 105. Gn-1, Gn, Gn + 1,... Are guide grooves that enable detection of a tracking error signal. Information is recorded as marks or spaces on and between the guide grooves. Assuming that the distance between adjacent guide grooves is Gp and the distance between adjacent tracks is tp, the relationship is Gp = 2 · tp.

[0032]

In an optical head device as shown in the third conventional example, in order to record a large amount of information on an information storage medium, a wavelength .lambda.
Is 650 nm, the numerical aperture NA of the objective lens 104 is 0.6, the thickness t of the substrate of the information storage medium 105 is 0.6 mm, the period Gp of the guide groove is 1.48 μm, In the optical condition where the period tp is 0.74 μm, when the beam 70 condensed by the objective lens 104 and the information storage medium 105 have a regular angle, the beam 70 condensed by the objective lens 104 When the center is irradiated, the tracking error signal crosses zero.
However, when the beam 70 condensed by the objective lens 104 and the information storage medium 105 are inclined from a regular angle,
When the beam 70 condensed by the objective lens 104 irradiates the center of the guide groove, the tracking error signal does not cross zero. At this time, an offset hardly occurs in the tracking error signal, but a phase shift occurs. This phase shift causes off-track. For example, an off-track of 0.1 μm occurs at an inclination of about 0.5 degrees. When off-track occurs, the information storage medium 105
There has been a problem that the information recorded on the information storage medium 105 cannot be read accurately, or the information recorded on the adjacent track is erased when the information is recorded on the information storage medium 105.

An object of the present invention is to provide a stable servo characteristic, a low error rate at the time of reproducing information, a stable writing operation and an erasing operation at the time of information writing and erasing, and a track operation at the time of information writing. An object of the present invention is to provide an optical head device that stably forms a mark at the center.

Another object of the present invention is to provide a tilt detecting device capable of accurately detecting a tilt of 0.5 degrees or less, and an optical information processing capable of stably recording and reproducing information even on an information storage medium having a large warp. It is to provide a device.

[0035]

According to the present invention, there is provided an optical head device comprising: a laser light source for emitting a coherent beam or a quasi-monochromatic beam; and an information storage medium having a track on which at least one mark and at least one space are arranged. A condensing optical system for condensing a beam emitted from the light source, and receiving light reflected by the information storage medium;
A photodetector having a plurality of detection regions for outputting a signal corresponding to the amount of received reflected light, and a tracking error for receiving a signal output from the photodetector and generating a tracking error signal based on the received signal Signal generating means, wherein the tracking error signal generating means comprises:
And the second signal amplitude is the absolute value of the difference between the first signal level and the second signal level, and the second signal amplitude is An absolute value of a difference between the first signal level and the third signal level, wherein the first signal level is a tracking error obtained when light emitted from the light source is applied to the center of the track. Signal value, the second signal level is the maximum value of the tracking error signal when the light emitted from the light source is scanned in a direction perpendicular to the track,
The third signal level is a minimum value of a tracking error signal when the light emitted from the light source is scanned in a direction orthogonal to the track, thereby achieving the above object.

According to another optical head device of the present invention, a laser light source emitting a coherent beam or a quasi-monochromatic beam and an information storage medium having a track in which at least one mark and at least one space are arranged are emitted from the light source. A condensing optical system for condensing the received beam, a photodetector having a plurality of detection regions for receiving reflected light reflected by the information storage medium and outputting a signal corresponding to the amount of the received reflected light; And a tracking error signal generating means for receiving a signal output from the photodetector and generating a tracking error signal based on the received signal, wherein the tracking error signal generating means overlaps the tracking error signal. When the component of the signal obtained from the region is reduced, the overlapping region is formed when the aperture of the condensing optical system is a circle having a radius of 1. An area where two circles each having a radius of 1 centered on two points separated by λ / (NA · Gp) in a direction orthogonal to the track from the center of the aperture of the light-collecting optical system, where λ is , The wavelength of light emitted from the light source, the NA is the numerical aperture of the light-collecting optical system, and the Gp is the distance from the center of a track to the center of an adjacent track in the information storage medium. Yes,
When the aperture of the condensing optical system is a circle having a radius of 1, λ /
(NA · Gp) has a relationship of λ / (NA · Gp) <1, whereby the above object can be achieved.

According to the optical head device of the present invention, a laser light source emitting a coherent beam or a quasi-monochromatic beam and an information storage medium having a track in which at least one mark and at least one space are arranged are emitted from the light source. A condensing optical system for condensing a beam, a photodetector having a plurality of detection regions for receiving reflected light reflected by the information storage medium and outputting a signal corresponding to the amount of the received reflected light, Receiving a signal output from the photodetector, based on the received signal, a tracking error signal generating means for generating a tracking error signal, and dividing the overlapping region of the reflected light and its neighboring region and receiving the divided light by the photodetector The condensing optical system is provided when the opening of the condensing optical system is a circle having a radius of 1. An area where two circles each having a radius of 1 centered on two points separated by λ / (NA · Gp) in a direction orthogonal to the track from the center of the opening, and the λ is emitted from the light source. NA is the numerical aperture of the light-collecting optical system, Gp is the distance from the center of a track to the center of an adjacent track in the information storage medium, and λ / (NA・ G
p) has a relationship of λ / (NA · Gp) <1, whereby the above object can be achieved. Note that the neighboring area means an area that is separated from the overlapping area by a predetermined distance.

[0038] The tracking error signal generating means may generate a tracking error signal using a signal obtained from a detection area that receives light in an area not including the overlapping area in the reflected light.

The division means has at least two division lines substantially parallel to the track, and the at least two division lines are arranged so as to sandwich the overlapping area of the reflected light therebetween, and the tracking error The signal generation unit may generate a tracking error signal by calculating a signal obtained from a detection area that receives reflected light incident on an area outside the at least two division lines.

[0040] The tracking error signal generating means may correct the tracking error signal by using a signal obtained from a detection area for receiving light in the overlapping area and the vicinity area of the reflected light.

The dividing means has N dividing lines substantially parallel to a tangent line of the track, wherein N is an odd number of 3 or more, and two of the N dividing lines are The overlapped area of the reflected light is disposed between
(N−2) division lines excluding the two division lines are arranged between the two division lines, and the tracking error signal generation unit is located outside the two division lines, and A tracking error signal is generated using a signal obtained from a detection area that receives the reflected light incident on the first area and the second area that do not include the overlapping area, and an even number between the two division lines is generated. The polarity of the signal obtained from the detection region receiving the reflected light incident on the number of regions is alternately inverted to generate a correction signal for adding the signal obtained from the detection region,
The correction signal may be added or subtracted from the tracking error signal.

The dividing means has N dividing lines substantially parallel to a tangent line of the track, N is an odd number of 3 or more, and two of the N dividing lines are The overlapped area of the reflected light is disposed between
The (N−2) division lines except for the two division lines are arranged between the two division lines, and the tracking error signal generation unit outputs an even number of division lines interposed between the two division lines. A signal obtained from the detection area that receives the reflected light incident on the area is multiplied by a predetermined value, the polarity of the signal multiplied by the predetermined value is alternately inverted, and the signal whose polarity is alternately inverted is added. A correction signal may be generated, and the correction signal may be added or subtracted from the tracking error signal.

The division means may be a hologram element.

[0044] The dividing means may be integrated with the condensing optical system.

[0045] The dividing means may be a dividing line of the photodetector.

Still another optical head device of the present invention provides a laser light source for emitting a coherent beam or a quasi-monochromatic beam, and an information storage medium having a track on which at least one mark and at least one space are arranged. A light-condensing optical system for condensing the emitted light, and a light detection device having a plurality of detection regions for receiving reflected light reflected by the information storage medium and outputting a signal corresponding to the amount of the received reflected light And a tracking error signal generating means for receiving a signal output from the photodetector and generating a tracking error signal based on the received signal. A light-reducing means for lowering the transmittance of the condensing optics, wherein the overlapping area is formed by forming the condensing optical system with an opening having a circle having a radius of 1. Is a region where two circles each having a radius of 1 centered on two points separated by λ / (NA · Gp) in the direction perpendicular to the track from the center of the opening of the light source. NA is the numerical aperture of the light-collecting optical system, Gp is the distance from the track center to the adjacent track center in the information storage medium, and λ / (NA · Gp)
Has a relationship of λ / (NA · Gp) <1, whereby the above object can be achieved.

The dimming means may be integrated with the condensing optical system.

[0048] The light reducing means may be a hologram element.

Another optical head device of the present invention is a laser light source that emits a coherent beam or a quasi-monochromatic beam, receives a beam emitted from the light source, and converts the received beam into a first beam and a second beam. An optical element for splitting, a condensing optical system for receiving the first beam and the second beam, and converging the first beam and the second beam into a minute spot on an information storage medium; A beam splitter that receives the beam reflected and diffracted by the storage medium, splits the received beam, and a photodetector that receives the beam split by the beam splitter and outputs a signal corresponding to the amount of the received beam. A signal processing unit that receives a signal output from the photodetector and calculates the received signal, based on the signal output from the signal processing unit, A drive unit for performing relative positioning between the optical optical system and the information storage medium, wherein the first beam is effectively combined with the second beam when the light is focused by the focusing optical system. The apparatus further includes tracking error signal generating means for generating a tracking error signal using a beam having a different numerical aperture and a small effective numerical aperture when condensed by the condensing optical system. Can be achieved.

The information storage medium has a mark or a predetermined groove for enabling detection of a tracking error signal, and the period of the mark or the predetermined groove for enabling detection of the tracking error signal on the information storage medium is represented by Gp. When the wavelength of the beam emitted from the light source is λ, and the numerical aperture of the condensing optical system on the information storage medium side is NA,
The first beam generated by the optical element has a relationship of Gp> λ / NA, the second beam generated by the optical element has a relationship of Gp <λ / NA, and the tracking error signal generation The means generates a tracking error signal from the second beam, thereby achieving the above object. The period of a groove means the distance from the center of a certain groove to the center of a groove adjacent to the groove.

[0051] The first beam and the second beam may be formed coaxially with each other.

[0052] The optical element may be a polarizing filter.

The optical element may be integrated with the condensing optical system.

The tilt detecting device according to the present invention comprises a laser light source for emitting a coherent beam or a quasi-monochromatic beam, a beam received from the light source, and a condensing beam for converging the received beam to a minute spot on an information storage medium. An optical system, a beam splitter that receives a beam reflected and diffracted by the information storage medium, splits the received beam, and receives a beam split by the beam splitter, and outputs a signal corresponding to the amount of the received beam. A photodetector for outputting, a signal processing unit for receiving a signal output from the photodetector and calculating the received signal, and a focus for performing relative positioning between the condensing optical system and the information storage medium. And a drive unit for controlling tracking, wherein the photodetector has a plurality of light receiving units, The information storage medium has a first pattern area including a mark and a space and a second pattern area including a predetermined groove, and the first pattern area and the second pattern area are alternately arranged on the information storage medium. And the signal processing unit, when the beam condensed by the condensing optical system is irradiated to the first pattern region or the second pattern region, a signal obtained from the photodetector By using this, the angle formed between the beam focused by the focusing optical system and the information storage medium is detected, thereby achieving the above object.

When a beam focused by the focusing optical system irradiates a mark and a space in the first pattern area, tracking control is performed using a signal obtained from the photodetector, and the focusing is performed. When the beam focused by the optical system irradiates the second pattern area, the beam focused by the focusing optical system using the signal obtained from the photodetector and the information storage medium The angle made may be detected.

When the beam condensed by the condensing optical system irradiates the second pattern area, tracking control is performed using a signal obtained from the photodetector, and the beam is condensed by the condensing optical system. When a beam to be emitted irradiates the first pattern area, an angle formed between the beam focused by the focusing optical system and the information storage medium is detected using a signal obtained from the photodetector. May be.

A beam focused by the focusing optical system is focused by the focusing optical system using a signal obtained from the photodetector when irradiating a mark and a space in the first pattern area. The angle formed between the beam and the information storage medium may be detected.

The first pattern region or the second pattern region
When the period of the pattern area is Gp, the wavelength of the beam emitted from the light source is λ, and the numerical aperture of the condensing optical system on the information storage medium side is NA, NA> λ / Gp
May be in a relationship.

The optical information processing apparatus according to the present invention comprises: a laser light source for emitting a coherent beam or a quasi-monochromatic beam;
A condensing optical system that receives the beam emitted from the light source and converges the received beam into a minute spot on the information storage medium; and a beam that receives the beam reflected and diffracted by the information storage medium and splits the received beam. A branching element, a photodetector that receives the beam split by the beam splitting element, and outputs a signal corresponding to the light amount of the received beam, receives a signal output from the photodetector, and calculates the received signal A signal processing unit, a first drive unit for controlling focus and tracking for performing relative positioning between the condensing optical system and the information storage medium, and a beam condensed by the condensing optical system And a second drive unit capable of changing an angle formed by the information storage medium, the photodetector has a plurality of light receiving units,
The information storage medium has a pattern or a predetermined groove capable of generating a tracking error signal, and a pattern or a predetermined groove period capable of generating the tracking error signal is Gp, and a beam emitted from the light source is When the wavelength is λ and the numerical aperture of the light-collecting optical system on the information storage medium side is NA, there is a relationship of NA> λ / Gp, thereby achieving the above object.

Another optical information processing apparatus of the present invention receives a laser light source that emits a coherent beam or a quasi-monochromatic beam, receives a beam emitted from the light source, and converges the received beam onto a small spot on an information storage medium. A converging optical system, a beam splitter that receives a beam reflected and diffracted by the information storage medium, and a beam splitter that splits the received beam, and receives a beam split by the beam splitter, according to the amount of light of the received beam. And a signal processing unit that receives the signal output from the photodetector and calculates the received signal, and performs relative positioning between the condensing optical system and the information storage medium. To control focus and tracking for the first
And a second drive unit capable of changing an angle formed between the beam focused by the focusing optical system and the information storage medium, wherein the photodetector includes a plurality of light receiving units. Have
The information storage medium may include a first mark and a space.
And a second pattern region comprising a predetermined groove, wherein the first pattern region and the second pattern region are alternately arranged on an information storage medium, and the signal processing unit comprises: The beam focused by the focusing optical system is the first beam.
When irradiating the pattern area or the second pattern area, using a signal obtained from the photodetector,
The above object can be achieved by detecting an angle formed between the beam focused by the focusing optical system and the information storage medium and generating a signal for driving the second drive unit.

When the beam focused by the focusing optical system irradiates a mark in the first pattern area,
Tracking control is performed using a signal obtained from the photodetector, and when a beam condensed by the condensing optical system irradiates the second pattern area, a signal obtained from the photodetector is used. The angle formed between the beam focused by the focusing optical system and the information storage medium may be detected.

When the beam focused by the focusing optical system irradiates the second pattern area, tracking control is performed using a signal obtained from the photodetector, and the beam is focused by the focusing optical system. When a beam to be irradiated irradiates the first pattern region, an angle formed between the beam focused by the focusing optical system and the information storage medium is detected using a signal obtained from the photodetector. May be.

When a beam focused by the focusing optical system irradiates a mark and a space in the first pattern area, the beam is focused by the focusing optical system using a signal obtained from the photodetector. The angle formed between the light beam and the information storage medium may be detected.

The first pattern area or the second pattern area
When the period of the pattern area is Gp, the wavelength of the beam emitted from the light source is λ, and the numerical aperture of the condensing optical system on the information storage medium side is NA, NA> λ / Gp
May be in a relationship.

According to still another optical head device of the present invention, a light source for emitting a coherent beam or a quasi-monochromatic beam and a beam emitted from the light source for an information storage medium having a track in which marks or spaces are selectively arranged are provided. A condensing optical system for condensing, a photodetector comprising a plurality of detection areas for receiving reflected light reflected by the information storage medium and outputting a signal corresponding to the amount of the received reflected light; and A dividing unit that divides the reflected light and allows the light to be received by the photodetector, and enters each of two predetermined regions, a first region and a second region, divided by a dividing line on the dividing unit. An information reproduction signal generating means for generating a reproduction signal for reproducing information recorded on the track from a differential signal of a signal obtained according to the reflected light. Changing means for changing a range included in the first area, the second area, or both areas in accordance with a positional relationship between a converging point of light emitted from the condensing optical system and the track. In addition, the above object can be achieved.

When the cross section of the reflected light on the dividing means is a substantially circle having a radius of 1, the dividing means is substantially parallel to the tangent of the track and is separated from the center of the substantially circle by a predetermined distance d. The first region is divided into three regions by a first division line and a second division line substantially parallel to the tangent line of the track and opposite to the first division line and separated by a distance d from the center. The area A outside the first dividing line not including the center of the circle, the area B between the first dividing line and the second dividing line, the second area not including the center of the substantial circle. The area outside the dividing line 2 is defined as a region C, and the information reproduction signal generating means determines that the light converging point of the light emitted from the light condensing optical system is a first light beam separated by a predetermined distance to one side of the track. Is scanned, the area A is set as the first area and the area B is set as the first area.
And the area C as a second area to generate the reproduction signal of the information recorded on the track, wherein the information reproduction signal generation unit is configured such that the light condensing point of the light emitted from the light condensing optical system is When scanning a second position on the track opposite to the first position by a predetermined distance, the area A
And the area B may be the first area, and the area C may be the second area to generate a reproduction signal of information recorded on the track.

The cross section of the reflected light on the dividing means has a radius of 1
A first dividing line substantially parallel to the tangent to the track and separated by a predetermined distance d from the center of the substantially circle, and the first dividing line substantially parallel to the tangent to the track. A second dividing line opposite to the first dividing line by a distance d from the center and a third dividing line substantially parallel to the tangent to the track and passing through the center of the substantially circle form four regions. The area A is divided outside the first dividing line not including the center of the substantially circle, the area B is sandwiched between the first dividing line and the third dividing line, the area B is divided into the second dividing line. A region between the line and the third division line is a region C, and a region outside the second division line not including the center of the substantially circle is a region D, and light emitted from the light-collecting optical system is defined as a region D. When the light converging point scans the first position at a predetermined distance to one side of the track, the area A is moved forward. The information reproduction signal generating means generates a reproduction signal of the information recorded on the track, using the area C and the area D as the second area as a first area, and emits the reproduction signal from the focusing optical system. When the light converging point scans a second position separated by a predetermined distance on the opposite side of the track from the first position, the area A and the area B are regarded as the first area. The information reproduction signal generating means may generate a reproduction signal of information recorded on the track, with the area D being the second area.

Still another optical head device according to the present invention is a light source that emits a coherent beam or a quasi-monochromatic beam and a beam emitted from the light source to an information storage medium having a track in which marks or spaces are selectively arranged. A light collecting optical system for collecting light, a light detector comprising a plurality of detection areas for receiving reflected light reflected by the information storage medium and outputting a signal corresponding to the amount of the received reflected light, and the information storage medium A dividing unit that divides the reflected light reflected by the optical detector and allows the light to be received by the photodetector, and enters each of two regions of a predetermined first region and a second region divided by the dividing unit An information reproducing signal generating means for generating a reproducing signal for reproducing information recorded on the track from a differential signal of a signal obtained according to the reflected light. When the cross section of the reflected light on the dividing means is a substantially circle having a radius of 1, the dividing means is substantially parallel to a tangent of the track and is divided into two parts separated by a predetermined distance d from the center of the substantially circle. A line is divided into three regions, and among the three regions, a region not including the center of the substantially circle is defined as the first region, and another region not including the center of the substantially circle is defined as the second region. When the focal point of the light emitted from the focusing optical system scans a position separated by a predetermined distance from the track, the information reproduction signal generating means reproduces information recorded on the track. A signal is generated, thereby achieving the above objective.

Still another optical head device according to the present invention is a light source that emits a coherent beam or a quasi-monochromatic beam, and transmits light emitted from the light source to an information storage medium having a track in which marks or spaces are selectively arranged. A condensing optical system for condensing, a photodetector comprising a plurality of detection regions for receiving reflected light reflected by the information storage medium and outputting a signal corresponding to the amount of the received reflection, and A dividing unit that divides the reflected light and receives the light with the photodetector; and enters each of two regions of a predetermined first region and a second region divided by the dividing unit. An information reproduction signal generating means for generating a reproduction signal for reproducing information recorded on the track from a differential signal of a signal obtained in accordance with the reflected light. When the cross section of the reflected light on the dividing means is a substantially circle having a radius of 1, the dividing means is substantially parallel to a tangent of the track and is divided into two parts separated by a predetermined distance d from the center of the substantially circle. The line is divided into four regions by a first division line, a second division line, and a third division line passing through the center of the substantially circle, and the four regions do not include the center of the substantially circle. Two regions, a region outside a first dividing line, a region between the third dividing line and the second dividing line, are defined as the first region, and the first dividing line and the third And a region outside the second division line that does not include the center of the substantial circle as the second region. Focus point is
When scanning a position separated by a predetermined distance from the track, the information reproduction signal generating means generates a reproduction signal of information recorded on the track, thereby achieving the above object.

The cross section of the reflected light on the dividing means has a radius of 1
In this case, the distance d from the center of the substantial circle on the dividing means to the dividing line may be 0.1 or more and 0.3 or less.

A still further optical head device according to the present invention includes a light source for emitting a coherent beam or a quasi-monochromatic beam, and an information storage medium having a track on which marks or spaces are selectively arranged or a track having a predetermined groove. A light-condensing optical system for condensing a beam emitted from a light source, and a photodetector having a plurality of detection regions for receiving reflected light reflected by the information storage medium and outputting a signal corresponding to the amount of the received reflected light And a tracking error signal generating means for receiving a signal output from the photodetector and generating a tracking error signal based on the received signal, and dividing the reflected light reflected by the information storage medium, and dividing the light. And a dividing unit that allows reflected light to be received by the photodetector, where λ is the wavelength of light emitted from the light source,
The numerical aperture of the condensing optical system is NA, the distance from the center of a track to the center of an adjacent track in the information storage medium is Gp, and the division has a relationship of λ / (NA · Gp) ≧ 1. When the cross section of the reflected light on the means is a circle having a radius of 1, the dividing means has at least five dividing lines substantially parallel to the tangent of the track, and the cross section of the reflected light on the dividing means And a first dividing line parallel to the track passing through the center of the first dividing line and a distance of about 0.1 mm across the first dividing line.
The two dividing lines located at 1 are the second dividing line and the third dividing line, and the two dividing lines located at a distance of about 0.1 from the end of the cross section of the reflected light on the dividing means are the second dividing line and the third dividing line. A fourth division line and a fifth division line are used, and the polarity of a signal obtained in response to the reflected light incident on the six regions divided by the fifth division line from the first division line is inverted alternately. And
The apparatus further comprises a tracking error signal generating means for generating a tracking error signal by alternately adding signals having inverted polarities, thereby achieving the above object.

Still another optical head device according to the present invention is an optical head device comprising: a light source that emits a coherent beam or a quasi-monochromatic beam; and an information storage medium having a track on which marks or spaces are selectively arranged or a track including a predetermined groove. A light detection system comprising a light collection optical system for collecting light emitted from a light source, and a plurality of detection regions for receiving light reflected by the information storage medium and outputting a signal corresponding to the amount of the received light reflected. Detector, a tracking error signal generating means for receiving a signal output from the photodetector and generating a tracking error signal, splitting the light reflected by the information storage medium, and receiving the split light by the photodetector Dividing means for allowing the light emitted from the light source to have a wavelength of λ; the numerical aperture of the condensing optical system being NA; Gp is the distance from the center of the track to the center of the adjacent track, and has a relationship of λ / (NA · Gp) ≧ 1, and when the aperture of the condensing optical system is a circle having a radius of 1, When the odd number is N, the dividing means has N dividing lines substantially parallel to the tangent line of the track, and two of the N dividing lines are located at the center of the aperture of the condensing optical system. On the other hand, the other (N-2) division lines except for the two division lines are arranged at an equal interval between the two division lines, and are arranged in a range of about 0.6 in width. The tracking error signal generating means generates a tracking error signal using a signal obtained from a detection area that receives the reflected light incident on two areas outside the two division lines that do not include the center of the circle. , The tracking error signal generation means includes an even number of regions between the two division lines. Generating a correction signal obtained by alternately inverting the polarity of a signal obtained from a detection area receiving the reflected light incident on the optical disc, and adding the inverted signal of the polarity; The above object can be achieved by adding or subtracting the correction signal from the error signal.

[0073] The dividing means may be a diffraction means.

[0074] The dividing means may be a dividing line of the photodetector.

Still another optical head device according to the present invention is directed to an information storage medium having a light source that emits a coherent beam or a quasi-monochromatic beam and a track on which marks or spaces are selectively disposed or a track including a predetermined groove. A condensing optical system that condenses the beam emitted from the light source, and receives the reflected light reflected by the information storage medium,
Diffraction means for generating diffracted light, and a light detector comprising a plurality of detection areas that receive light diffracted by the diffraction means and output a signal corresponding to the received light amount, the diffraction means includes: It has a plurality of divided regions, and diffracted light of a desired order generated from a partial region group A of the plurality of regions becomes a first spherical wave, and is not included in the region group A of the plurality of regions. The diffracted light of the desired order generated from the region group B composed of the regions becomes a second spherical wave having a condensing point farther from the diffraction means than the converging point of the first spherical wave, and Focus error signal generating means for generating a focus error signal from a difference in the size of a cross section of the spherical wave and the second spherical wave on the photodetector, wherein the diffraction means is provided with a tangent to the track. Having at least one vertical dividing line, Across the line belonging to one said region group A of the two regions in contact with each other, the other belongs to the region group B, by the can achieve the object.

Still another optical head device according to the present invention provides a light source for emitting a coherent beam or a quasi-monochromatic beam, and an information storage medium having a track on which marks or spaces are selectively arranged or a track having a predetermined groove. A condensing optical system for condensing a beam emitted from a light source, a diffractive means for diffracting reflected light reflected by the information storage medium to generate diffracted light, and receiving the light diffracted by the diffractive means; A light detector comprising a plurality of detection areas for outputting a signal corresponding to the amount of light obtained, wherein the diffraction means has a plurality of divided areas, and is generated from a partial area group A of the plurality of areas. The diffracted light of the desired order is
And the diffracted light of the desired order generated from the region group B composed of the regions not included in the region group A of the plurality of regions is farther from the diffraction means than the converging point of the first spherical wave. A second spherical wave having a focal point at a position, and a focus error for generating a focus error signal from a difference in cross-sectional size on the photodetector between the first spherical wave and the second spherical wave. A signal generation unit, wherein the diffraction unit has a diffraction region in a range wider than a range corresponding to an opening of the light-collecting optical system, and is in contact with an outer periphery of the opening and is parallel to a tangent of the track. , And one of two regions that are in contact with each other across the first or second division line belong to the region group A, and the two regions The other belongs to the area group B, and Target can be achieved.

[0077] The diffraction means may be integrated with the condensing optical system.

According to the method of the present invention, the light is emitted to an information storage medium having an emission step of emitting a coherent beam or a quasi-monochromatic beam and a track in which at least one mark and at least one space are arranged. A light collecting step of collecting a beam, a light detecting step of receiving reflected light reflected by the information storage medium in a plurality of detection areas, and outputting a signal corresponding to the amount of the received reflected light; Receiving a signal output by the step, and generating a tracking error signal based on the received signal, wherein the tracking error signal generating step obtains a tracking error signal from an overlapping area from the tracking error signal. The overlapping region is formed as a circle having a radius of 1 with the aperture of the condensing optical system. At this time, λ / (NA · G
p) is an overlapping area of two circles each having a radius of 1 centered on two points separated by p), wherein λ is the wavelength of light emitted in the emission step, and NA is the condensing optics. Gp is a distance from the center of a track to the center of an adjacent track in the information storage medium, and λ / ( NA · Gp) is λ / (NA · Gp)
<1 and thereby achieve the above object.

Another method of the present invention includes an emitting step of emitting a coherent beam or a quasi-monochromatic beam, receiving a beam emitted in a laser beam generating step, and dividing the received beam into a first beam and a second beam. A focusing step of receiving the first beam and the second beam, and focusing the first beam and the second beam into a minute spot on an information storage medium; A beam reflected by the information storage medium, receives the beam diffracted, a branching step of branching the received beam, a light detection step of receiving the beam branched by the branching step, and outputting a signal corresponding to the light amount of the received beam, A signal processing step of receiving a signal output in the light detection step and calculating the received signal; and collecting light based on the signal calculated in the signal processing step. A positioning step of determining a relative position between an optical system and the information storage medium;
Is different from the second beam in the effective numerical aperture when condensed by the condensing optical system, and is a beam having a small effective numerical aperture when condensed by the condensing optical system. The method further includes a tracking error signal generating step of generating a tracking error signal by using the tracking error signal, thereby achieving the above object.

Still another method of the present invention includes an emission step of emitting a coherent beam or a quasi-monochromatic beam;
A convergence step of receiving the beam emitted in the emission step and converging the received beam into a minute spot on the information storage medium, and a branching step of receiving the beam reflected and diffracted by the information storage medium and branching the received beam And a light detecting step of receiving the beam split by the splitting step by a plurality of light receiving units and outputting a signal corresponding to the light amount of the received beam; receiving a signal output by the light detecting step; A signal processing step of calculating, a first driving step of controlling focus and tracking for performing relative positioning between the condensing optical system and the information storage medium, and condensing by the condensing optical system A second driving step capable of changing an angle formed between the beam and the information storage medium, wherein the information storage medium outputs a tracking error signal. A pattern or a predetermined groove that can generate the tracking error signal, a period of the pattern or the predetermined groove is Gp, a wavelength of a beam emitted in the emission step is λ, Assuming that the numerical aperture on the information storage medium side of the system is NA, the relationship NA> λ / Gp is established, thereby achieving the above object.

Another method of the present invention comprises an emission step for emitting a coherent beam or a quasi-monochromatic beam, and a method for collecting the beam emitted from the light source on an information storage medium having a track on which marks or spaces are selectively arranged. A light condensing step, a light detection step of receiving reflected light reflected by the information storage medium in a plurality of detection areas, and outputting a signal corresponding to the amount of the received reflected light; and a light reflected by the information storage medium. And dividing the track from a differential signal of a signal obtained according to the reflected light incident on each of two predetermined first and second regions divided by the dividing step. An information reproduction signal generation step of generating a reproduction signal for reproducing information recorded on the optical disc. Flip a changing step of changing the range included in the first region or the second region or both regions further include, by its, can achieve the above object.

Still another method of the present invention is to provide a method for emitting a coherent beam or a quasi-monochromatic beam, and an information storage medium having a track on which marks or spaces are selectively arranged or a track including a predetermined groove. A condensing step of condensing a beam emitted from the light source, receiving reflected light reflected by the information storage medium in a detection region,
A light detection step of outputting a signal corresponding to the amount of received reflected light, a tracking error signal generation step of receiving a signal output by the light detection step, and generating a tracking error signal based on the received signal; Dividing the light reflected by the information storage medium, wherein the wavelength of the light emitted by the emission step is λ, the numerical aperture of the condensing optical system is NA, and the track in the information storage medium is Gp is the distance from the center of the next track to the center of the adjacent track, and has a relationship of λ / (NA · Gp) ≧ 1, and is incident on six regions divided from the first division line to the fifth division line. Generating a tracking error signal by alternately inverting the polarity of a signal obtained in accordance with the reflected light and adding the alternately inverted signal; And further comprising the step of:
The fifth division line is substantially parallel to a tangent line of the track, and the first division line passes through the center of the cross section of the reflected light and is parallel to the track. When the cross section of the reflected light is a circle having a radius of 1, the dividing line and the third dividing line are located at a distance of about 0.1 across the first dividing line, and the fourth dividing line and the third dividing line When the cross section of the reflected light is a circle having a radius of 1,
It is located at a distance of about 0.1 from the end of the cross section of the reflected light, thereby achieving the above object.

Still another method of the present invention includes an emission step of emitting a coherent beam or a quasi-monochromatic beam;
A focusing step of focusing a beam emitted from the light source on an information storage medium having a track or a track composed of a predetermined groove in which marks or spaces are selectively arranged,
Receiving the reflected light reflected by the information storage medium in a plurality of divided areas, generating a diffracted light, receiving the light diffracted by the diffracting means, and outputting a signal corresponding to the received light amount; A light detection step including a plurality of detection regions, and a focus error signal generating step of generating a focus error signal from a difference in cross-sectional size between the first spherical wave and the second spherical wave. Is a diffracted light of a desired order generated from a partial region group A of the plurality of regions, and the second spherical wave is generated from a region not included in the region group A of the plurality of regions. A desired order of diffracted light generated from the area group B, wherein the area group A is one of two areas that are in contact with each other across at least one division line perpendicular to a tangent to the track. Group B is the other of the two regions Thus, the above object can be achieved.

[0084]

Embodiments of the present invention will be described below with reference to the drawings. Configurations indicated by the same reference numerals in the drawings perform the same operation.

(Embodiment 1) FIG. 1 schematically shows an optical system of an optical head device according to Embodiment 1.

Light emitted from a semiconductor laser 101 serving as a light source is reflected by a parallel plate beam splitter 102 and becomes parallel light by a collimator lens 103 which is a part of a condensing optical system. This light is further condensed by an objective lens 104 which is a part of a condensing optical system, and condensed on an information layer 108 of an optical disk 105 which is an information storage medium. The actuator 107 moves the objective lens 104 and the holding means 106 for holding the objective lens 104, following the surface deflection and eccentricity of the optical disk 105.

The diffraction and diffraction by the information layer 108 of the optical disk 105
The reflected light 108a that has been reflected passes through the objective lens 104 again and becomes parallel light. The reflected light 108a that has become this parallel light
Becomes convergent light again by the collimator lens 103. When the converged reflected light 108a passes through the parallel plate beam splitter 102, astigmatism is given. The convergent light provided with astigmatism is received by the photodetector 150. Focus point F0 of light emitted from objective lens 104
The optical system is arranged so that the detection surface of the photodetector 150 is located at the position of the circle of least confusion of the convergent light given astigmatism when the light beam coincides with the information layer 108 of the optical disk 105.

The distance from the center of a certain groove of the optical disk 105 as an information storage medium to the center of an adjacent groove is defined as Gp. Information is recorded either on or between the grooves, or both on and between the grooves. In this embodiment,
A sequence in which these pieces of information are recorded is called a track.
Further, let the numerical aperture of the objective lens 104 as a light condensing optical system of the optical head device be NA, and the wavelength of light emitted from the semiconductor laser 101 be λ.

In the first embodiment, a case where the condition of λ / (NA · Gp) <1 (Equation 4) is satisfied will be described.

FIG. 2 shows the detection areas 201 to 208 of the photodetector 150 of the first embodiment and the information reproduction signal generation means 450.
And the configuration of a circuit as the tracking error signal generating means 451.

The photodetector 150 is provided with dividing lines 301 to 304
Is divided into eight detection areas 201 to 208.
Under the condition of Equation 4, + diffracted by the groove of the optical disc 105
The first-order diffracted light and the -1st-order diffracted light have portions overlapping each other. In FIG. 2, the overlapping area 200, which is the overlapping portion, is shown.
Is indicated by oblique lines. The maximum value W of the width of the overlapping region 200 in the radial direction is as follows: W = 2 × (1−λ / (NA × Gp)) (Equation 5) However, the opening is a circle having a radius of 1.

The division lines 301 to 303 are
5 is a straight line parallel to the tangent to the groove. The dividing line 304 is a straight line perpendicular to the tangent to the groove of the optical disk 105. Here, the direction of the tangent to the groove is the direction optically projected on the photodetector.

When the astigmatism method is used as the focus error signal detection method, if astigmatism is given around the groove of the optical disk 105 and the direction of 45 degrees, the direction of the groove projected on the photodetector will be 90 degrees. The direction rotates. Therefore, even if the actual direction of the division line is perpendicular to the tangent direction of the groove of the optical disk 105, if the direction of the tangent line of the groove projected on the photodetector is parallel, the "partition parallel to the tangent line of the groove" Line ". Hereinafter, the same expression is used.

The dividing line 302 passes through the center of the projection of the aperture of the optical system onto the photodetector 150. Division line 301 and division line 3
No. 03 is arranged so as to sandwich the overlapping area 200. The distance d between the dividing line 301 and the dividing line 302 and the distance d between the dividing line 302 and the dividing line 303 are substantially equal to W / 2. Due to this arrangement, as shown in FIG. 2, an overlapping area 200 of the + 1st-order and -1st-order diffracted lights by the grooves of the optical disc 105 enters the detection areas 202, 203, 206, and 207 of the photodetector 150. . Signals obtained according to the amounts of light received from the detection areas 201 to 208 are referred to as s1 to s8, respectively.

Here, the focus error signal FE can be obtained by calculating FE = (s1 + s2 + s5 + s6)-(s3 + s4 + s7 + s8) (Equation 6). Note that FIG.
Does not show an arithmetic circuit for obtaining the focus error signal FE.

Hereinafter, the circuit system of the information reproduction signal generating means 450 will be described. Information reproduction signal generation means 450
Includes adders 401 to 405. The information reproduction signal generation means 450 outputs the information reproduction signal RF.
Generate a signal. An RF signal, which is an information reproduction signal, is obtained from the sum of signals obtained from all regions. As shown in FIG. 2, the adder 401 outputs a sum signal of “signal s1 + signal s8”, the adder 402 outputs a sum signal of “signal s2 + signal s7”, and the adder 403 outputs “signal s3 + signal s6”. "
Is output, and the adder 404 outputs “signal s4 + signal s
5 "is output.

The adder 405 includes adders 401 to 4
Receiving the output signal of No. 04, it outputs a sum signal which is the sum of the respective output signals. An information reproduction signal raw (RF signal) which is an output signal output from the adder 405 can be obtained by RF = s1 + s2 + s3 + s4 + s5 + s6 + s7 + s8 (Equation 7).

The tracking error signal generating means 4 will be described below.
The circuit system 51 will be described. The tracking error signal generating means 451 includes an adder 401, an adder 404,
And a differential operation circuit 406. Differential operation circuit 40
6 receives the output signals of the adders 401 and 404,
The differential signal is output. The output signal output from the differential operation circuit 406 can be obtained by TE1 = (s1 + s8)-(s4 + s5) (Equation 8). The output signal output from the differential operation circuit 406 becomes a tracking error signal TE1.

When the tilt (tilt) of the optical disk 105 occurs in a direction (radial direction) perpendicular to the tangent to the groove of the optical disk 105, the conventional optical head device has the following disadvantages in tracking control.

When a tilt occurs, the reflected light detected is shifted in the tilt direction. When the tilt of the disk is θ, the reflected light is shifted by 2θ. For example, when the numerical aperture NA is 0.6
If the tilt θ is 0.8 degrees and the opening is a substantially circle having a radius of 1, (sin 2θ) /NA=0.047, and the detected reflected light is shifted by 0.047 in the tilt direction.

When the tilt occurs, the tracking error signal value TE0 obtained when the focal point F0 of the light emitted from the objective lens 104 coincides with the center of the groove, and the tracking error obtained when the beam crosses the groove. The maximum value T of the signal
Absolute value of difference between Emax and minimum value TEmin |
The difference between both TEmax-TE0 | and | TEmin-TE0 |

FIG. 3 shows the relationship between the tracking error signal and the off-track amount. The off-track amount means a distance from the center of the track to the focal point F0.

A signal indicated by a black square is a tracking error signal when there is no aberration. The signal indicated by the solid line is a tracking error signal when a tilt occurs. In the tracking error signal indicated by the solid line, TEmax
= 0.38, TEmin = −0.42, TE0 =
-0.20, | TEmax-TE0 | = 0.58, | TEmin-T
E0 | = 0.22, and a large difference occurs.

If the tracking control is performed in this state, the focal point F0 of the light emitted from the objective lens 104 is located at a position deviated from the track center, so that accurate recording and reproduction of information cannot be performed.

The case where an offset voltage is applied to the tracking error signal in this state so that the focal point F0 is located at the center of the track will be described.

A signal indicated by a white triangle in FIG. 3 is a tracking error signal after the correction so that the off-track amount becomes zero. The offset voltage is applied so that the track center and the zero-cross point of the tracking error signal coincide. At this time, the upper amplitude and the lower amplitude with respect to the 0 level of the tracking error signal become asymmetric.

When the asymmetry is increased, the operation of tracking control becomes unstable, and accurate recording and reproduction of information cannot be performed. Thus, | TEmax-TE0 |
And the difference between | TEmin−TE0 |, the off-track amount increases. Even if an offset voltage is applied to reduce the amount of off-track, the deviation of the symmetry of the tracking error signal increases. This degree can be expressed as a deviation in symmetry of the tracking error signal when the off-track amount is corrected to zero.

The result of comparison between Embodiment 1 and the conventional optical head device regarding the deviation of the symmetry of the tracking error signal will be described below.

Assuming that the numerical aperture of the objective lens is NA = 0.6 and the wavelength of light λ = 0.66 μm, the groove interval Gp = 1.48 μm.
When reproducing the optical disk of m, if the opening is a circle having a radius of 1, the + 1st-order diffracted light and the -1st-order diffracted light have W =
It has an overlapping area with a width of 0.51.

Assuming that the substrate thickness of the optical disk is 0.6 mm,
Assuming that a tilt of 0.4 degrees occurs in the radial direction, the conventional optical head device has a tilt of about 0.0 with respect to the track center.
An off-track of 7 μm occurs. Further, when the off-track amount is corrected to 0 by adding an offset voltage, a 31% shift occurs in the TE symmetry.

Here, the symmetry of the tracking error signal is defined by (A + B) / (AB), where A is the value of the upper end of the tracking error signal and B is the value of the lower end.

In the case of the first embodiment, the tracking error signal TE1 is taken only from the outside of the overlapping area of the + 1st-order and -1st-order diffracted lights, so that the off-center with respect to the track center when a radial tilt of 0.4 degrees occurs. The track amount is suppressed to about 0.045 μm. When the off-track amount is corrected to zero, the symmetry deviation of the tracking error signal becomes 19%, which is suppressed to about ／ of the conventional example.

In the conventional optical head device, when the objective lens shift occurs, the detection spot moves on the detector, and if the off-track amount is corrected to 0, the symmetry of the tracking error signal is shifted. When the off-track amount is corrected to 0 at an objective lens shift of 150 μm, the symmetry deviation of the tracking error signal becomes 16%.

On the other hand, in Embodiment 1, when the off-track amount is corrected to 0 with the objective lens shift of 150 μm, the deviation of the symmetry of the tracking error signal can be suppressed to 3%.

As described above, in the first embodiment, even if the optical disc 105 is tilted or the like, stable tracking control can be realized while maintaining a small off-track amount. For this reason, the first embodiment can record and reproduce information with a low error rate.

Hereinafter, another example which provides the same effect as the above-described optical head device will be described with reference to FIG.

FIG. 4 shows the detection area 20 of the photodetector 151.
1, 204, 205, 208, and 209, and the configuration of circuits as information reproduction signal generation means 450 and tracking error signal generation means 451. The difference from the optical head device described above is that a photodetector 151 is used instead of the photodetector 150. The optical arrangement is similar to the arrangement shown in FIG.

The photodetector 151 is provided with the dividing lines 301 and 30.
5, 305, and 306 make five detection areas 20
1, 204, 205, 208, and 209. The dividing line 301 and the dividing line 303 are arranged so as to sandwich the overlapping region 200 of the + 1st-order diffracted light and the −1st-order diffracted light, and the detection region 209 is defined by the dividing line 301 and the dividing line 303. Light of the overlapping area 200 enters.

Detection areas 201, 204, 205, 20
8, and 209 generate signals s1, s2, s3, s4, and s5, respectively, according to the amount of received light.

A circuit system as the information reproduction signal generating means 450 will be described. The information reproduction signal generation means 450
It includes adders 401, 404, and 405. An RF signal, which is a reproduction signal of information, is transmitted in all regions 201, 20
4, 205, 208 and 209 are obtained from the sum of the signals s1, s2, s3, s4 and s5.
As shown in FIG. 4, the adder 401 outputs a sum signal of “signal s1 + signal s4”, and the adder 404 outputs “signal s2 +
A signal sum of the signal s3 "is output. The adder 405 receives the output signal of the adder 401, the output signal of the adder 404, and the signal s5 output from the detection area 209, and outputs a sum signal of the received signals.

The output signal R output from the adder 405
The F signal can be obtained by RF = s1 + s2 + s3 + s4 + s5 (Equation 9).

The tracking error signal generating means 4 will be described below.
A circuit system as 51 will be described. The tracking error signal generation means 451 includes adders 401 and 404
And a differential operation circuit 406. The differential operation circuit 406 receives output signals from the adders 401 and 404 and outputs a differential signal that is a difference between the output signals. The output signal output from the differential operation circuit 406 can be obtained by TE1 = (s1 + s4)-(s2 + s3) (Equation 10).

In this example, the same effects as in the example of FIG. 2 can be obtained with a configuration in which the number of detection areas and the number of head amplifiers are smaller than the example shown in FIG.

Hereinafter, still another example providing the same effect as that of the optical head device having the structure shown in FIG. 2 will be described with reference to FIG.

FIG. 5 shows the photodetector 152. The photodetector 152 is divided into eight regions by dividing lines 306 to 309. Dividing lines 307 and 30 perpendicular to the groove tangents
9 is arranged so as to sandwich an overlapping area 200 of the + 1st-order diffracted light from the groove and the -1st-order diffracted light from the groove. Detection areas 210 to 213 outside these two division lines 307 and 309 and not including the center of the circle receive light, and
213 generate signals s1 to s4 according to the amounts of light received.

The tracking error signal TE1 can be obtained by TE1 = (s1 + s4)-(s2 + s3) (Equation 11).

The optical head device of this example can also receive the diffracted light except for most of the overlapping region 200 of the + 1st-order diffracted light and the -1st-order diffracted light, as shown in FIGS. 2 and 4. The characteristics of the tracking error signal can be improved almost in the same manner as the optical head device having the configuration. The optical head device having the configuration shown in FIG. 5 can perform stable tracking control with a small off-track amount, and thus can record and reproduce information with a low error rate.

Referring to FIG. 6, a description will be given below of another example which provides the same effect as that of the optical head device having the structure shown in FIG.

FIG. 6 shows the photodetector 153. The photodetector 153 is divided into eight regions by dividing lines 310 to 313. Dividing lines 310 and 31 parallel to the tangent of the groove
2 is located closer to the end of the cross section of the reflected light 108a onto the photodetector 153. Areas 214 to 217 outside the dividing lines 310 and 312 and not including the center of the circle receive light,
The signals s1 to s1 are determined according to the amount of light received by the regions 214 to 217.
s4 is generated.

The tracking error signal TE1 is calculated by the above equation (1).
It is obtained by the same operation as in 1.

In this example, the overlapping area 200 of the + 1st-order diffracted light and the -1st-order diffracted light can be largely removed to receive the diffracted light, and the optical head device having the configuration shown in FIGS. In almost the same manner as described above, the characteristics of the tracking error signal can be improved. The optical head device having the configuration shown in FIG. 6 can perform stable tracking control with a small off-track amount, and thus can record and reproduce information with a low error rate.

In the first embodiment, the dividing line is an example of a straight line, but the overlapping area 200 of the + 1st-order diffracted light and the -1st-order diffracted light by the groove of the optical disk 105 is surrounded by a curve. Since the area is an area, a dividing line may be formed by a curve corresponding to the area.

(Embodiment 2) As in Embodiment 1, the case where the condition of Expression 4 is satisfied will be described.

In the second embodiment, a configuration and a method for correcting a tracking error signal from a signal obtained from an overlapping area of the + 1st-order diffracted light and the -1st-order diffracted light by the groove of the optical disc 105 will be described.

The schematic diagram of the optical system of the optical head device according to the second embodiment is the same as that shown in FIG. For this reason, the configuration and operation of the optical system of the optical head device according to the second embodiment are the same as the configuration and operation of the first embodiment, and a description of the configuration and operation will be omitted.

FIG. 7 shows the configuration of the detection areas 201 to 208 of the photodetector 150 and the circuit as the tracking error signal generation means 451 in the second embodiment. The photodetector 150 is
The image is divided into eight detection areas 201 to 208 by division lines 301 to 304. The arrangement of the dividing lines and the like are the same as in the first embodiment. The detection areas 201 to 208 receive light, and the detection areas 201 to 208 receive signals s1 to s according to the amount of light received.
8 are generated. The method of generating the focus error signal FE and the information reproduction signal is the same as in the first embodiment, and a description thereof will be omitted.

A circuit system as the tracking error signal generating means 451 will be described. The tracking error signal generating means 451 includes adders 401 to 404, 407 and 40
8 and a dynamic operation circuit 406.

As shown in FIG. 7, adder 401 outputs a sum signal of "signal s1 + signal s8", adder 402 outputs a sum signal of "signal s2 + signal s7", and
3 outputs a sum signal of “signal s3 + signal s6”, and adder 404 outputs a sum signal of “signal s4 + signal s5”.
Adder 407 receives the output of adder 401 and the output signal of adder 403, and outputs a sum signal of the output signals. Adder 408 receives the output signal of adder 402 and the output signal of adder 404, and outputs a sum signal of the output signals. The differential operation circuit 406 receives the output signal of the adder 407 and the output signal of the adder 408, and outputs a differential signal of the output signals.

The output signal of the differential operation circuit 406 is given by the following equation: TE1 = (s1 + s3 + s6 + s8)-(s2 + s4 + s5 + s7).

In the second embodiment, the central + 1st order diffracted light and −1
A method of processing a signal generated by a detection region that receives light in the overlapping region 200 of the next-order diffracted light is different from a normal push-pull method. In the second embodiment, the polarity of a part of the signal generated by the detection area that receives light in the overlapping area 200 is inverted, and the signal whose polarity is inverted and the remaining part of the signal generated by the detection area are used. To correct the tracking error signal.

According to the second embodiment, under the same conditions as in the first embodiment, when the off-track amount is corrected to 0 when a tilt of 0.4 degrees occurs in the radial direction, the deviation of the symmetry of the tracking error signal is 14%. become. This is about half that of the conventional optical head device, and the effect of suppressing radial tilt is particularly large.

As described above, in the optical head according to the second embodiment, stable tracking control can be realized while maintaining a small off-track amount even when the device optical disk 105 is tilted. As a result, recording and reproduction of information can be realized with a low error rate.

Hereinafter, still another example which provides the same effect as that of the optical head device having the structure shown in FIG. 7 will be described with reference to FIG.

FIG. 8 shows the photodetector 153. The photodetector 153 is divided into twelve detection areas 218 to 229 by division lines 315 to 320. Division line 315
And the dividing line 319 are arranged in parallel with the tangent to the groove of the optical disk so as to sandwich the overlapping area of the + 1st order diffracted light and the −1st order diffracted light from the groove. Division line 315 and division line 319
Is about the same as W in Equation 5 above. Dividing line 316
To 318 are arranged at equal intervals between the dividing line 315 and the dividing line 319. The detection areas 218 to 229 generate signals s1 to s12, respectively, according to the amount of light received.

The circuit system as the tracking error signal generating means 451 will be described. The tracking error signal generation means 451 includes adders 401 to 404 and 409 to
412 and a differential operation circuit 406.

An adder 401 outputs a sum signal of the signals s1 and s12, an adder 402 outputs a sum signal of the signals s2 and s11, and an adder 403 outputs a signal s3 and a signal s10.
And the adder 404 outputs the signal s4 and the signal s9.
, And the adder 409 outputs the signal s5 and the signal s8.
, And the adder 410 outputs a signal s6 and a signal s7.
And outputs the sum signal. The adder 411 includes an adder 401,
Upon receiving output signals output from 403 and 409, a sum signal of these output signals is output. Adder 412 receives output signals output from adders 402, 404, and 410, and outputs a sum signal of the output signals. The differential operation circuit 406 receives the output signal of the adder 411 and the output signal of the adder 412, and outputs a differential signal that is a difference between the output signals. The output signal of the differential operation circuit 406 is given by TE1 = (s1 + s3 + s5 + s8 + s10 + s12)-(s2 + s4 + s6 + s7 + s9 + s11) (Equation 13).

In the optical head device having the configuration shown in FIG. 8, the off-track amount is 0.042 μm even if the radial tilt is 0.4 °.

When the off-track amount is corrected to 0, in the optical head device having the configuration shown in FIG. 8, the symmetry deviation of the tracking error signal becomes 18%. on the other hand,
In the conventional optical head device, the deviation of the symmetry of the tracking error signal is 31%, and the optical head device having the configuration shown in FIG. It has better tracking error signal symmetry than the device.

When the off-track amount is corrected to 0 in the case where the objective lens shift is 150 μm, in the optical head device having the configuration shown in FIG. 8, the symmetry deviation of the tracking error signal becomes 8%. In the conventional optical head device, the symmetry deviation of the tracking error signal is 16%. The optical head device having the configuration shown in FIG. 8 can reduce the degree of symmetry of the tracking error signal by about half compared to the conventional optical head device.

As described above, the optical head device according to the second embodiment can realize stable tracking control while maintaining a small off-track amount even if the optical disc 105 has a tilt or the like. In the optical head device according to the second embodiment, information recording / reproduction can be realized with a low error rate.

In this embodiment, the overlapping area of the + 1st-order and -1st-order diffracted light by the track is recorded on the optical disk 10
Although it is divided into four in the direction perpendicular to the tangent line of the groove 5, it may be divided more finely, and the same effect as in this embodiment can be obtained.

Also, taking into consideration the astigmatism method as a focusing method, a dividing line 320 perpendicular to the tangent of the groove is provided. If there is no such dividing line, adders 401 to 40 are provided.
4, 409 and 410 are not required. In such a case, the effect can be obtained in the same manner as in the embodiment shown here.

(Embodiment 3) In Embodiment 3, as in Embodiments 1 and 2, a case where the condition of the above expression 4 is satisfied will be described.

In the third embodiment, a correction signal corresponding to a disturbance is generated from a signal obtained from the overlapping area 200 of the + 1st-order diffracted light and the -1st-order diffracted light by the groove to correct the tracking error signal.

The schematic diagram of the optical system of the optical head device according to the third embodiment is the same as that shown in FIG. For this reason, the configuration and operation of the optical system of the optical head device according to the third embodiment are the same as the configuration and operation of the first embodiment, and a description of the configuration and operation will be omitted.

FIG. 9 shows the detection areas 201 to 208 of the photodetector 150 according to the third embodiment and the configuration of a circuit as the tracking error signal generation means 451.

The photodetector 150 is provided with dividing lines 301 to 304
Is divided into eight detection areas 201 to 208.
The arrangement of the dividing lines and the like are the same as in the first embodiment. The detection areas 201 to 208 output signals s1 to s according to the amount of light received.
8 are generated.

The method of generating the focus error signal FE and the information reproduction signal is the same as that of the first embodiment, and will not be described. The input signals to be input to the adders 401 to 404 and the method by which the adders 401 to 404 calculate these input signals are also the same as those in the first embodiment.

A circuit system as the tracking error signal generating means 451 of the third embodiment will be described. The tracking error signal generating means 451 includes adders 401 to 404, variable gain amplifying circuits 413 and 414, and a differential operation circuit 4.
06, 415 and 416.

The variable gain amplifying circuit 414 includes an adder 402
And outputs a signal obtained by multiplying this signal by α1. Here, α1 is a predetermined value. Further, variable gain amplifying circuit 413 receives the output signal from adder 403 and outputs a signal obtained by multiplying this signal by α2. Here, α2 is a predetermined value.

The differential operation circuit 406 receives the output signal of the adder 401 and the output signal of the adder 404, and
A differential signal obtained by subtracting the output signal of the adder 404 from the output signal of No. 1 is output.

The differential operation circuit 415 receives the output signal of the variable gain amplifying circuit 413 and the output signal of the variable gain amplifying circuit 414, and outputs a differential signal which is a difference between the output signals.

The differential operation circuit 416 includes the differential operation circuit 40
6 and the output signal of the differential operation circuit 415, and outputs a differential signal which is a difference between the output signals.

The output signal of the differential operation circuit 416 is given by the following equation: TE1 = (s1 + s8)-(s4 + s5)-{α1 · (s2 + s7) -α2 · (s3 + s6)}

The gain α1 of the variable gain amplifying circuit 414 and the gain α2 of the variable gain amplifying circuit 413 in consideration of the amount and polarity of the radial tilt and the amount and polarity of the objective lens shift.
Is determined. By changing the gains α1 and α2, | TEmax−TE0 | and | TEmin−TE0
| Can be reduced. That is, since the correction amount can be adjusted by adjusting the gain, the third embodiment has a large improvement effect that the difference can be reduced as compared with the second embodiment.

For this reason, in the third embodiment, the optical disc 1
Even if there is a tilt of 05, stable tracking control can be realized while maintaining a small off-track amount, and information recording / reproduction can be realized with a low error rate.

In the third embodiment, +
Although the overlapping region 200 of the first-order and the -1st-order diffracted light is divided into two in the direction perpendicular to the tangent to the groove of the optical disk 105, it may be divided more finely. Even in such a case,
Such an optical head device can obtain the same effects as those of the above-described third embodiment.

(Embodiment 4) In Embodiment 4, as in Embodiments 1, 2, and 3, a case where the condition of Expression 4 is satisfied will be described.

In the fourth embodiment, the optical transmittance of the region including the overlapping region of the + 1st-order diffracted light and the -1st-order diffracted light by the groove is reduced, and the characteristics of the tracking error signal are improved.

FIG. 10A is a schematic view of the optical system of the optical head device according to the fourth embodiment. The configuration of the optical system in FIG. 10A is the same as the configuration of the optical system in FIG. 1 except for the objective lens 109. Therefore, a detailed description of the configuration other than the objective lens 109 is omitted.

Hereinafter, the objective lens 109 in FIG. 10A will be described with reference to FIG. 10B.

FIG. 10B is a front view of the objective lens 109 which is a part of the condensing optical system according to the fourth embodiment. A hologram is provided in the hatched portion 110 of the objective lens 109 as a dimming unit. The light diffracted by the hologram is
Only the 0th-order light, which becomes unnecessary light and does not contribute to signal reproduction and is not diffracted, is effectively used as the information layer 108 of the optical disc 105.
Focused on top.

Detection area 2 of photodetector 150 of Embodiment 4
43 to 254 may be arranged as shown in FIG. 43a. When the detection areas 251 to 254 are arranged as shown in FIG. 43A, the tracking error signal TE1, the focus error signal FE, and the information reproduction signal RF are obtained by the above-described equations 1, 2, and 3.

The result of comparison between the fourth embodiment and the conventional optical head device regarding the deviation of the symmetry of the tracking error signal will be described below.

The transmittance T of the area 110 is 55%, and the area 11 is
The ratio of the radius of 0 to the radius of the objective lens 109 is 0.7
As a second example, when the radial tilt is corrected to 0.4 degrees and the off-track amount is corrected to 0 under the same conditions as in the first embodiment, the deviation of the symmetry of the tracking error signal is 17 in the fourth embodiment.
% In the conventional optical head device, the deviation of the symmetry of the tracking error signal is 31%. In the fourth embodiment, the deviation of the symmetry of the tracking error signal can be reduced by about 比 べ as compared with the conventional optical head device.

In the fourth embodiment, even if the optical disk 105 is tilted or the like, stable tracking control can be realized while maintaining a small off-track amount. Thus, in the fourth embodiment, recording and reproduction of information can be realized with a low error rate.

In this embodiment, the objective lens 109 is used.
Another spot may be formed by the diffracted light of the hologram provided above. In this case, the 0th-order diffracted light has a substrate thickness of 0.6 mm.
And the primary diffracted light can be used as a CD spot having a substrate thickness of 1.2 mm. By forming another spot with the diffracted light of the hologram, it is possible to achieve compatibility with the function of the bifocal lens.

In this embodiment, a hologram is provided as the light reducing means. However, a similar effect can be obtained by attaching a reflecting film having an appropriate transmittance to the objective lens or an absorbing film.

Further, as shown in FIG. 11, instead of directly attaching the dimming means to the objective lens, a similar hologram element or a filter 111 having a film is attached to the holding means 106.
Thus, the lens may be held so as not to move relative to the objective lens. Also in these cases, the same effect as the effect shown in this embodiment can be obtained.

The dimming means shown in FIG.
4 covers the surface farther from the information storage medium, but may cover the surface closer to the information storage medium. Similarly, the dimming means of FIG. 10a may cover the surface of the objective lens 109 closer to the information storage medium.

In this embodiment, the dimming means is provided integrally with the condensing optical system, but may be provided separately on the fixed optical system. FIG. 12 shows an example in which a dimming unit is provided in the optical path from the light source to the information storage medium. As shown in FIG. 12, light emitted from a semiconductor laser 101 as a light source passes through a filter 111 as a dimming unit, the amount of light near the center is reduced, and is reflected by a parallel plate beam splitter 102. In this case, +
The zero-order light in the overlapping region of the first-order diffracted light and the -1st-order diffracted light is reduced, and the influence of the overlapping region can be reduced.

FIG. 13 shows an example in which the optical system from the information storage medium to the photodetector has a dimming means. As shown in FIG. 13, a dimming region 113 is provided below the parallel plate prism 112.
May be provided. Even with this arrangement, it is possible to reduce the influence of the overlapping region of the + 1st-order diffracted light and the -1st-order diffracted light, and almost the same effect can be obtained.

In the first to fourth embodiments, the astigmatism method is used as a method for obtaining the focus error signal. However, the effect of the present invention is not limited to this, and the focus method is the Foucault method or the spot size method. It can be combined with other methods such as the method, and is not limited to the focus method.

(Embodiment 5) As in Embodiments 1 to 4, a case where the condition of Expression 4 is satisfied will be described in Embodiment 5 as well.

In the fifth embodiment, a hologram element or a step prism is used as the dividing means. As a method for obtaining the focus error signal, a spot size method is used.

FIG. 14 is a schematic view of the optical system of the optical head device according to the fifth embodiment.

The structure and operation of the fifth embodiment will be described below with reference to FIG.

Light emitted from a semiconductor laser 101 as a light source becomes parallel light by a collimator lens 103 and is reflected by a beam splitter 115. This light is converged by the objective lens 104, which is a part of the condensing optical system. The convergent light is transmitted to the information layer 1 of the optical disc 105 as an information storage medium.
08. Reflected light 1 reflected by information layer 108
08a again passes through the objective lens 104 and becomes parallel light. The parallel reflected light 108a passes through the beam splitter 115 and is converged by the detection lens 116.
The converged light 108a is diffracted by the hologram element 117, which is a dividing means. -1st order diffracted light 108b and + 1st order diffracted light 108c diffracted by hologram element 117
Is received by the photodetector 154.

FIG. 15 shows the pattern of the area division of the hologram element 117, the detection area of the photodetector 154, the -1st-order diffracted light 108b and the + 1st-order diffracted light 10b on the photodetector 154.
8c shows the shape of the cross section.

The hologram element 117 is divided into a plurality of strip-shaped areas. The symbols attached to each area are shown in FIG.
Correspond to the symbols attached to the cross sections of the -1st order diffracted light 108b and the + 1st order diffracted light 108c on the photodetector 154. -1 order diffracted light 1 originating from the area represented by uppercase letters AD
08b is -1 resulting from the area represented by lowercase letters ad.
It is focused on the side farther from the detection lens 116 than the next diffracted light 108b.

When the focal point F0 of the light emitted from the objective lens 104 coincides with the information layer 108 of the optical disk 105, the cross section of the diffracted light on the photodetector 154 marked with capital letters A to D The optical system and the hologram element 117 are designed such that the cross section of the diffracted light marked with the small letters a to d has the same size.

The detection areas 230 to 232 output signals f1 to f3 according to the amount of light received.

The focus error signal FE is obtained by FE = f1 + f3-f2 (Equation 15).

The information layer 108 of the optical disk 105 is moved from the focal point F0 of the light emitted from the objective lens 104 to the objective lens 1
When moving away from 04, the cross section of the -1st-order diffracted light 108b labeled with uppercase letters A to D becomes smaller, and the cross section of the -1st-order diffracted light 108b labeled with lowercase letters a to d becomes larger. Therefore, the signals of f1 and f3 decrease and f
2 increases, and the focus error signal FE decreases.

The information layer 108 of the optical disk 105 is moved from the focal point F0 of the light emitted from the objective lens 104 to the objective lens 1
04, the cross section of the -1st-order diffracted light 108b labeled with uppercase letters A to D becomes larger, and the lowercase letters a to
The cross section of the -1st-order diffracted light 108b marked with d is small. Therefore, the signals of f1 and f3 increase, the signal of f2 decreases, and the focus error signal FE increases.

As a result, focus control for maintaining the focal point F0 on the information layer 108 is realized.

The detection areas 233 to 236 of the photodetector 154
From t1 to t4 are signals obtained in accordance with the amount of light received from. An arithmetic circuit (not shown) as a tracking error signal generating means generates a tracking error signal TE1.

The tracking error signal TE1 is obtained by TE1 = (t1 + t4)-(t2 + t3) (Equation 16).

This substantially gives a difference in light amount between the non-hatched area and the hatched area in the hologram element 117 of FIG.

Tracking error signal TE2 of phase difference method
Are (signal t1 + signal t3) and (signal t2 + signal t4)
By comparing the phases.

An RF signal for reproducing information is expressed by the following equation (17).
RFf, or RFt of equation 18, or RFf and R
It is given by the sum of both Ft.

RFf is obtained by RFf = f1 + f2 + f3 (Equation 17).

RFt is obtained by RFt = t1 + t2 + t3 + t4 (Equation 18).

A feature of the fifth embodiment is that several regions on both sides of a dividing line passing through the center of the opening and parallel to the track are replaced in a diagonal direction. In FIG. 15, A and D,
A total of eight lines B and C, a and d, and b and c are interchanged. Thereby, the same effect as in the second embodiment can be obtained. In the fifth embodiment, when the tilt occurs 0.4 degrees in the radial direction, if the off-track amount is corrected to 0, the deviation of the symmetry of the tracking error signal becomes 14%.
The deviation of the symmetry of the tracking error signal is about の of the deviation of the symmetry of the tracking error signal of the conventional optical head device. The fifth embodiment particularly suppresses radial tilt.

In the fifth embodiment, even if the optical disc 105 is tilted, stable tracking control can be realized while maintaining a small off-track amount. Thus, in the fifth embodiment, recording and reproduction of information can be realized with a low error rate.

As another area pattern, if only a part of the central area is replaced with a diagonal as in the hologram element 118 shown in FIG. 16, the photodetector 153 shown in FIG. The same effect as the example used can be obtained. In this case, when the radial tilt is 0.4 degrees, the off-track amount is 0.042 μm. When the off-track amount is corrected to 0, the symmetry deviation of the tracking error signal is 18%.
become. When the radial tilt is 0.4 degree and the off-track amount is corrected to 0, in the conventional optical head device, the deviation of the symmetry of the tracking error signal becomes 31%. That is, in the fifth embodiment using the hologram element 118 shown in FIG. 16, the deviation of the symmetry of the tracking error signal can be significantly reduced as compared with the conventional optical head device.

The hologram element 118 shown in FIG.
In the fifth embodiment using the objective lens shift of 150 μm
, When the off-track amount is corrected to 0, the symmetry deviation of the tracking error signal becomes 8%. On the other hand, in the conventional optical head device, the objective lens shift 150
When μm is present, if the off-track amount is corrected to 0, the deviation of the symmetry of the tracking error signal becomes 16%. That is, in the fifth embodiment using the hologram element 118 shown in FIG. 16, the deviation of the symmetry of the tracking error signal can be reduced to about half as compared with the conventional optical head device.

In the fifth embodiment using the hologram element 118 shown in FIG. 16, stable tracking control can be realized while keeping a small off-track amount with respect to the tilt of the optical disk 105 and the like. Thus, the fifth embodiment using the hologram element 118 shown in FIG.
Can realize recording and reproduction of information with a low error rate.

As described above, in the fifth embodiment, by using the hologram element as the dividing means, a great effect can be realized without increasing the detection area of the photodetector from the conventional example. Therefore, it is not necessary to increase the number of head amplifiers for obtaining RF signals, and the circuit load is small.

In the fifth embodiment, an area is divided by a dividing line that passes through the center of the opening and is perpendicular to the tangent of the track to form a spherical wave having a condensing point on the side close to the collimator lens 103. The regions represented by the symbols a to d and the regions represented by the uppercase symbols A to D that form a spherical wave having a condensing point on the far side are arranged so as to be in contact with each other with the dividing line interposed therebetween. . In addition, these two types of regions are alternately arranged outside an opening which is not normally irradiated with light.

In the case where no dividing line is provided in the direction perpendicular to the track and a narrow area extending from one end of the opening to the other in a direction parallel to the track, the hologram element 117 and the objective lens
When the center of the opening 4 is shifted, the amount of light entering the area of the photodetector 154 represented by lowercase symbols a to d and the uppercase symbol A
The balance of the amount of light entering the region represented by D is lost. When the focal point F0 of the light emitted from the objective lens 104 is shifted from the position on the coasting layer 108 of the optical disk 105 and defocus occurs, ± 1st-order diffracted light and 0th-order light by the tracks of the optical disk 105 are generated. In the overlapping portion, a bright and dark stripe pattern parallel to the track is generated. The balance between the amount of light entering the region represented by lowercase symbols a to d and the amount of light entering the region represented by uppercase symbols A to D also depends on how the stripe pattern and the division of the region of the hologram element 117 overlap. Crumble.

According to the method of the fifth embodiment, such a deviation in balance is eliminated in principle.

In calculation, in the case of the conventional example in which a dividing line is not inserted perpendicularly to the tangent line of the track, the numerical aperture NA of the objective lens =
0.5, the wavelength of light λ = 0.795 µm, the diameter of the objective lens = 4 mm, and the width of each region of the hologram element is 0.2.
mm, the center of the objective lens and the center of the polarization anisotropic hologram element are shifted by 100 μm, and the focus gain changes by 3.4 dB at ± 2 μm defocus.

When the arrangement is performed as in the fifth embodiment, the focus gain changes by only 1.2 dB under the same conditions in terms of calculation. This variation is about 1/3 of the conventional example,
It has decreased significantly. As a result, the focus control can be stabilized, and becomes strong against disturbance, so that the error rate during information reproduction decreases.

If two areas are alternately provided outside the opening without dividing the track in the vertical direction, the focus gain changes only 1.8 dB under the same conditions in calculation. This variation is about 1/2 of the conventional example.
As a result, focus control can be stabilized, and the error rate during unfortunate reproduction is reduced.

Further, the pattern of the area of the hologram element as the dividing means can be freely set as compared with the pattern of the detection area of the photodetector, and the pattern of the area suitable for the purpose can be easily realized. it can.

Although the dividing means of the fifth embodiment is simply a hologram element, it is different from the polarization anisotropic hologram element by 1 /.
A combination of four-wavelength plates may be used. In this case, the light use efficiency can be increased without impairing the effects of the present invention.

In the fifth embodiment, the dividing means for realizing the invention relating to the focus control and the invention relating to the tracking control at the same time has been described. However, the invention relating to the focus control and the invention relating to the tracking control are independent. With the configuration using only the above, the effects according to the invention can be obtained independently.

As the dividing means, there is a method using a step prism or the like other than the hologram element. FIG.
FIG. 1 shows a schematic diagram of the optical system in that case. A step prism 119 is used instead of the hologram element 117 in FIG. The light separated by the step prism is received by the photodetector 154. Also in this case, the same effect as when the hologram element is used can be obtained.

(Embodiment 6) A configuration and a method for reproducing information recorded at an off-track position in a groove of an optical disk as an information storage medium will be described below.

The schematic diagram of the optical system of the optical head device according to the sixth embodiment is the same as that shown in FIG. For this reason, the configuration and operation of the optical system of the optical head device according to the fifth embodiment are the same as the configuration and operation of the sixth embodiment, and a description of the configuration and operation will be omitted.

FIG. 18 shows a detection area of the photodetector 150 according to the sixth embodiment, and a circuit configuration as the information reproduction signal generation means 450 and the tracking error signal generation means 451.

The photodetector 150 is provided with dividing lines 301 to 304
Is divided into eight detection areas 201 to 208.
The arrangement of the dividing lines and the like are the same as in the first embodiment. Signals obtained according to the amounts of light received from the detection areas 201 to 208 are referred to as s1 to s8, respectively.

[0224] The information reproduction signal generation means 450 of FIG.
As in the first embodiment, adders 401 to 404 and 4
05. Further, the information reproduction signal generating means 450 of FIG. 18 includes adders 417 and 419 and differential operation circuits 418 and 420. The tracking error signal generation means 451 includes adders 401 to 40
4, 421, and 422 and a differential operation circuit 423.

The operation of reading a pit string recorded at an off-track position will be described below with reference to FIGS. 19a, 19b and 19c.

FIG. 19A shows an optical disc in which grooves 501 and pits 502 are arranged on the optical disc. The grooves 501 and the pits 502 are recorded on the information layer 108 in FIG.

In the first address zone 504, the center of the pit row of the track 508 is off-track by a predetermined distance with respect to the track 507 passing through the center of the groove in the zones 503 and 506 in which the grooves are arranged. In the second address zone 505, the center of the pit row of the track 509 is off-track by a predetermined distance in a direction opposite to that of the track 508.

When the focal point F0 of the light emitted from the objective lens 104 is in the zone 503 or the zone 506,
When the tracking control is performed, the focal point F0 exists on the track 507, for example, at a point 510. With the rotation of the optical disk 105, the relative position with respect to the optical head device moves, and the focal point F0 is located at the point 51 on the extension of the track 507.
It moves in the order of 1, point 512, and point 513. Focus point F
While 0 is in the first address zone 504 and the second address zone 505, the tracking error signal is held.

The focus error signal FE is, as in the first embodiment, FE = (s1 + s2 + s5 + s6)-(s3 +
s4 + s7 + s8).

The tracking error signal can be obtained by the calculation of the following equation (19). In the tracking error signal generating means 451 of FIG. 18, the adder 421 receives the signal t1 output from the adder 401 and the signal t2 output from the adder 402, and outputs a signal that is the sum of the signal t1 and the signal t2. I do. Adder 422 receives signal t3 output from adder 403 and signal t4 output from adder 404, and outputs a signal that is the sum of signal t3 and signal t4. The differential operation circuit 423 receives the signal output from the adder 421 and the signal output from the adder 422, and outputs a differential signal between them. That is, the output signal TE of the differential operation circuit 423 is obtained by TE = (t1 + t2)-(t3 + t4) (Equation 19). Tracking control is performed by the tracking error signal TE.

The information reproduction signal generating means 450 shown in FIG.
The information reproduction signal RF is generated in the same manner as the information reproduction signal generation means 450 of FIG. A method for generating an information reproduction signal will be described below. The information reproduction signal generation means 450 includes an adder 401
To 405.

The adder 401 receives the signal s1 and the signal s8, and outputs a signal t1, which is the sum of the signal s1 and the signal s8. Adder 402 receives signals s2 and s7,
The signal t2 which is the sum of the signal s2 and the signal s7 is output. The adder 403 receives the signal s3 and the signal s6, and
3 and a signal t3 which is the sum of the signal s6. Adder 4
04 receives the signals s4 and s5 and outputs a signal t4 which is the sum of the signals s4 and s5. The adder 405 is
Output signals t1 to t filed from adders 401 to 404
4 and outputs a signal that is the sum of those signals. The information reproduction signal RF output from the adder 405 is given by: RF = t1 + t2 + t3 + t4 (Equation 20)

Further, the adder 417 comprises the adders 402, 4
The signals t2, t3, and t4 output from the signals 03, 404, and 404 are received, and a signal that is the sum of these signals is output. The differential operation circuit 418 receives the output signal from the adder 401 and the output signal from the adder 417, and outputs a differential signal between them. The signal RFa1 output from the differential operation circuit 418 is given by: RFa1 = t1− (t2 + t3 + t4) (Equation 21)

The adder 419 includes adders 401, 402,
And 403 output signals t1, t2 and t
3 and outputs a signal that is the sum of those signals. The differential operation circuit 420 receives the output signal from the adder 419 and the output signal from the adder 404, and outputs a differential signal between them. The signal RFa2 output from the differential operation circuit 420 is given by RFa2 = (t1 + t2 + t3) -t4 (Expression 22).

The address detection circuit 424 receives the tracking error signal TE from the differential operation circuit 423, and determines whether the focal point F0 of the light emitted from the objective lens 104 is in the grooved zone 503 or zone 506, First
Is determined to be in the address zone 504 or the second address zone 505, and an identification signal as a result of the determination is output.

The control circuit 425 includes the address detection circuit 42
4 receives the identification signal, and controls the switches 426 and 427 based on the identification signal.

Switch 426 receives the signal output from differential operation circuit 418 and the signal output from differential operation circuit 420, and outputs one of them.

Switch 427 receives the signal output from adder 405 and the signal output from switch 426, and outputs one of them. Switch 427
Are used to reproduce information or addresses recorded on the information storage medium.

The control circuit 425 outputs the output signal RF of the adder 405 from the switch 427 when the focal point F0 of the light output from the objective lens 104 is in the grooved zone 503 or 506. Control the switch as follows. When the focal point F0 is in the first address zone 504, the switch 427 outputs
The switch is controlled so that the output signal RFa1 of the differential operation circuit 418 is output. Further, when the focal point F0 is in the second address zone 505, the switch 427 controls the switch so that the output signal RFa2 of the differential operation circuit 420 is output.

That is, when the light converging point F0 is located on the point 511 of the first address zone 504, as shown in FIG. 19B, the difference which is the difference outputted from the two regions sandwiching the dividing line 301 is obtained. From the motion signal, the track 507
The information recorded as a pit string on the upper side is reproduced.

Point 512 of second address zone 505
When the focal point F0 is present above, as shown in FIG. 19c, a pit row is recorded on the track 507 from the differential signal output from each of the two regions sandwiching the dividing line 303. Reproduce information.

In the following, the numerical aperture NA of the objective lens is 0.6.
And the light wavelength λ = 0.660 μm, and the groove interval Gp
= 1.48 μm, and the jitter on the optical disk in which the track 508 and the track 509 are off-track by 0.37 μm each with respect to the track 507 is as follows.
13 shows a result of comparing the optical head device of Embodiment 6 with a conventional optical head device.

The detection area is divided by the dividing line at the center of the opening,
In a conventional optical head device that reproduces information from a differential signal, which is a difference between the divided regions, a calculated jitter is 6.4%.

On the other hand, in the sixth embodiment, the opening is a circle having a radius of 1, the distance from the dividing line 302 is d, and d = 0.
When the detection area is divided by the division line 303 or the division line 301 at the position 23, and information is reproduced from the differential signal which is the difference between the divided areas, the calculated jitter is 1.8%. Becomes Embodiment 6 can improve the jitter by 4% or more compared to the conventional optical head device.

If d is 0.1 or more and d is 0.3 or less, the jitter according to the sixth embodiment is 3%
Thus, the jitter according to the sixth embodiment is less than half of the jitter due to the conventional optical head device.

As described above, in the configuration as shown in the present embodiment, the pit train at the off-track position can be reproduced with little jitter, so that the margin against disturbances and the like increases, and in such a format, It is possible to stabilize the recording and reproduction of information on an optical disk on which information such as an address is recorded.

An optical head device having a photodetector different from the photodetector shown in FIG. 18 will be described below with reference to FIG.

FIG. 20 shows the detection area 20 of the photodetector 151.
1, 204, 205, 208, and 209, an information reproduction signal generation unit 450, and a tracking error signal generation unit 451 are shown.

The information reproduction signal generation means 450 shown in FIG.
Adders 401, 404, 405, 417, and 419
And differential operation circuits 418 and 420.
Further, the tracking error signal generating means 451 of FIG.
Includes adders 401 and 404 and a differential operation circuit 423.

The adder 405 includes all the detection areas 201, 204, 205, 208, and 20 of the photodetector 151.
9 generates a signal corresponding to the amount of light received. Further, the differential operation circuit 418 calculates the differential signal ｛signal t1- (signal t2
+ Signal t3)}. Also, the differential operation circuit 420
Generates a differential signal {(signal t1 + signal t2) −signal t3}. Here, the signal t1 is generated by the adder 401, and the signal t2 is the signal s output by the region 209.
5, and the signal t3 is generated by the adder 404.

The tracking error signal is obtained by adding the signal t1 obtained by adding the signals output from the two regions on the left side of the dividing line 301 and the signal output from the two regions on the right side of the dividing line 303. It becomes a differential signal that is a difference from the signal t3.

With the above-described configuration, in the optical head device having the photodetector shown in FIG. 20, it is possible to stably record and reproduce information on and from the optical disc on which information such as an address is recorded.

An optical head device having an information reproduction signal generation means different from the information reproduction signal generation means shown in FIG. 18 will be described below with reference to FIGS. 21a, 21b and 21c.

FIG. 21A shows an optical disc in which grooves 501 and pits 502 are arranged on the optical disc. The grooves 501 and the pits 502 are recorded on the information layer 108 in FIG.

FIGS. 21b and 21c illustrate a photodetector 350
And an outline of an information reproduction signal generation means 450.

FIG. 21B shows the first address zone 504.
2 shows a circuit configuration necessary for reproducing information recorded in the information. FIG. 21 c shows the second address zone 50.
5 shows a circuit configuration necessary for reproducing the information recorded in FIG. The information reproduction signal generation means 450
Includes an adder 430 and a differential operation circuit 431 shown in FIG. 21B, and an adder 432 and a differential operation circuit 433 shown in FIG. 21C.

The differential operation circuit 431 generates a reproduction signal RFa3 based on the following equation (23), and the differential operation circuit 433 generates a reproduction signal RFa4 based on the following equation (24).

RFa3 = t1- (t3 + t4) (Expression 23) RFa4 = (t1 + t2) -t4 (Expression 24) Recorded in the first address zone 504 When reproducing information, a reproduction signal RFa3 is used. When reproducing information recorded in the second address zone 505, a reproduction signal RFa4 is used. The information reproduction signal generation means 450 outputs the reproduction signal RFa3 or the reproduction signal RFa3.
4 may be provided.

In the following, when the numerical aperture of the objective lens is NA = 0.
6, the wavelength of the light is λ = 0.660 μm, the gap between the grooves is Gp = 1.48 μm, and the track 508 and the track 509 are each 0.37 μm with respect to the track 507.
21 shows the results of comparison between the optical head device having the configuration shown in FIGS. 21b and 21c and the conventional optical head device with respect to the jitter of the optical disk off-tracking by m.

As described above, in the conventional optical head device which divides the detection area by the dividing line at the center of the aperture and reproduces information from the differential signal output from each of the divided areas, the calculation The upper jitter is 6.4%.

On the other hand, in the optical head device having the structure shown in FIGS. 21B and 21C, when the opening is a circle having a radius of 1 and the distance from the dividing line 302 is d, the dividing line 303 at the position of d = 0.23 or the dividing line When the detection area is divided by the line 301 and information is reproduced from the differential signal RFa3 or RFa4 obtained by calculating the signal output from the divided area as described above, the calculated jitter is 1.4%. FIG.
The optical head device having the configuration shown in FIG. 21C can improve the jitter by 5% or more as compared with the conventional optical head device.

As described above, even in the configuration shown in this embodiment, the pit train at the off-track position can be reproduced with a small amount of jitter. It is possible to stabilize the recording and reproduction of information on an optical disk on which information such as an address is recorded.

Hereinafter, an optical head device having information reproducing signal generating means different from the information reproducing signal generating means shown in FIGS. 18 and 20 will be described with reference to FIGS. 22a and 22b.

FIG. 22A shows an optical disc in which grooves 501 and pits 502 are arranged on the optical disc. The grooves 501 and the pits 502 are recorded on the information layer shown in FIG.

FIG. 22b schematically shows the photodetector 351 and the information reproduction signal generation means 450.

The information reproduction signal generation means 450 includes a differential operation circuit 434. The differential operation circuit 434 generates a reproduction signal RFa0 based on the following equation (25).

RFa0 = t1-t4 (Equation 25) The reproduction signal RFa0 is used as a reproduction signal in the first and second address zones 504 and 505, and information is reproduced.

In the following, when the numerical aperture of the objective lens is NA = 0.
6, the wavelength of the light is λ = 0.660 μm, the gap between the grooves is Gp = 1.48 μm, and the track 508 and the track 509 are each 0.37 μm with respect to the track 507.
22B shows the results of a comparison between the optical head device having the configuration of FIG. 22B and the conventional optical head device with respect to the jitter of the optical disk off-tracking by m.

As described above, in the conventional optical head device, the calculated jitter is 6.4%. The jitter of the optical head device having the configuration of FIG. 22B is 2.6%. The optical head device having the configuration shown in FIG. 22B can reduce the jitter by almost 4% as compared with the conventional optical head device.

As described above, even in the configuration shown in the present embodiment, the pit row at the off-track position can be reproduced with little jitter, so that the margin against disturbance and the like increases, and in such a format, It is possible to stabilize the recording and reproduction of information on an optical disk on which information such as an address is recorded.

In the optical head device having the configuration shown in FIG. 22B, the information reproduction signal generation means 450 determines whether the information being reproduced is located in the first address zone 504 or the second address zone 505. There is no need to select the output signal. Therefore, the optical head device having the configuration of FIG. 22B can be realized with a relatively simple circuit system.

Hereinafter, an optical head device having information reproducing signal generating means different from the information reproducing signal generating means shown in FIGS. 18, 20 and 22 will be described with reference to FIGS. 23a and 23b.

FIG. 23A shows an optical disc in which grooves 501 and pits 502 are arranged on the optical disc. The grooves 501 and the pits 502 are recorded on the information layer 108 in FIG.

FIG. 23B schematically shows the photodetector 352 and the information reproduction signal generation means 450.

The information reproduction signal generation means 450 includes a differential operation circuit 437 and adders 435 and 436. The differential operation circuit 437 generates the reproduction signal RFa00 based on the following equation (26).

RFa00 = (t1 + t3) − (t2 + t4) (Expression 26) RFa00 is the first and second address zones 504.
And 505 are used as reproduction signals.

As described above, in the conventional optical head device, the calculated jitter is 6.4%. The jitter of the optical head device having the configuration of FIG. 23B is 1.2%. The optical head device having the configuration of FIG. 23B can reduce the jitter close to 5% as compared with the conventional optical head device.

In the optical head device having the configuration shown in FIG. 23B, the information reproduction signal generation means 450 determines whether the information being reproduced is located in the first address zone 504 or the second address zone 505. There is no need to select the output signal. Therefore, the optical head device having the configuration of FIG. 23B can be realized with a relatively simple circuit system.

(Embodiment 7) In Embodiment 7, as in Embodiment 6, a pit row consisting of a mark and a space recorded at an off-track position with respect to a groove of an optical disk as an information storage medium is reproduced. I do.

The optical system of the optical head device of Embodiment 7 is the same as the optical system of Embodiment 5 shown in FIG. 14 except for the following points. In the optical system of the optical head device according to Embodiment 7, FIG.
Hologram element 1 instead of hologram element 117
20 is used, and instead of the photodetector 154, the photodetector 1
55 is used.

The pattern of the area division of the hologram element 120 will be described with reference to FIG. FIG. 24 shows a pattern of the area division of the hologram element 120 and the photodetector 1.
The cross-sectional shapes of the 0th-order light 108a, the -1st-order diffracted light 108b, and the + 1st-order diffracted light 108c on the 55th detection region and the photodetector 155 are shown.

The hologram element 120 is divided into a plurality of strip-shaped areas. The symbols attached to each region are the 0th-order light 108a and the -1st-order diffracted light 1 on the photodetector 154 in FIG.
08b and the symbol of the cross section of the + 1st-order diffracted light 108c. The -1st-order diffracted light 108b resulting from the region of the symbols of uppercase letters AD is generated from the region of the symbols of lowercase letters ad.
Focuses on the side farther from the detection lens 116 than the first-order diffracted light 108b. Light in the region indicated by the symbol X is not diffracted, and all become zero-order light 108a.

The -1st-order diffracted light 108b is detected in the detection area 230.
, And the + 1st-order diffracted light 108c is received in the detection regions 233 to 236. The zero-order light is received by the detection area 237. The focus error signal is generated from a signal obtained according to the amount of light received from the detection areas 230 to 232.

Signals obtained according to the amounts of light received in the detection areas 233 to 236 are denoted by t1 to t4, respectively. A signal obtained according to the amount of light received by the detector 237 is x0. The tracking error signal TE for the groove 501 of the optical disk 105 is obtained from TE = (t1 + t4)-(t2 + t3) (Equation 27).

Let β be the ratio of the diffraction efficiency of the + 1st-order diffracted light 108c diffracted in the region other than X to the 0th-order light transmitted through the X region of the hologram element 120.

The information reproduction signal RF is obtained from the following equation: RF = t1 + t2 + t3 + t4 + β · x0 (Equation 28)

An optical disk 105 having a structure as shown in FIG.
When reproducing the data, if the focal point F0 is on the track 507 of the first address zone 504, information recorded as a pit row on the track 508 is obtained by performing an operation to obtain the following equation RFa1. To play.

RFa1 = (s1 + s4) − (s2 + s3 + β × x0) (Expression 29) When the focal point F0 is on the track 507 of the second address zone 505, RFa2 of the following expression is obtained. By performing such an operation, information recorded as a pit string on the track 509 is reproduced.

RFa2 = (s1 + s4 + β · x0) − (s2 + s3) (Equation 30) With such a configuration, in the seventh embodiment, the same effect as in the sixth embodiment can be obtained. In the seventh embodiment, jitter when reproducing a pit row recorded at a position off-track with respect to the focal point F0 is reduced. Therefore, in the seventh embodiment, it is possible to stably record and reproduce information on and from an optical disc on which information such as an address is recorded in such a format.

(Embodiment 8) Embodiment 8 shows an example in which the characteristics of a TE signal are improved using a hologram element.
Focusing uses a spot size method, and tracking uses a push-pull method.

FIG. 25 is a schematic view of the optical system of the optical head device according to the eighth embodiment. Hereinafter, the configuration and operation of the optical system will be described with reference to FIG.

The linearly-polarized light 101a emitted from the semiconductor laser 101 as a light source is converted into parallel light by a collimator lens 103 as a part of a condensing optical system. The parallel light 101a enters the polarization anisotropic hologram element 121 as a dividing means. The polarization direction of the light 101 a emitted from the semiconductor laser 101 is arranged in the polarization anisotropic hologram element 121 so as not to generate diffracted light. Light 10 passing through polarization anisotropic hologram element 121
1a passes through the quarter-wave plate 122 and becomes circularly polarized light. The light 101a is further condensed by an objective lens 104 as a part of a condensing optical system, and condensed on an information layer 108 of an optical disk 105 as an information storage medium.

The holding means 106 integrally holds the polarization anisotropic hologram element 121, the quarter-wave plate 122, and the objective lens 104. The actuator 107 is a holding unit 1
06 is moved following the surface runout or eccentricity of the optical disk 105.

[0294] Diffraction by the information layer 108 of the optical disc 105
The reflected light 108a that has been reflected passes through the objective lens 104 again and becomes parallel light. The reflected light 108a that has become this parallel light
Again passes through the quarter-wave plate 122 and becomes linearly polarized light having a direction different from that of the light 101a by 90 degrees. The linearly polarized light in this direction is diffracted by the polarization anisotropic hologram element 121 to generate a -1st order diffracted light 108b and a + 1st order diffracted light 108c. The -1st order diffracted light 108b and the + 1st order diffracted light 108c are converged again by the collimator lens 103. The -1st-order diffracted light 108b that has become the convergent light is received by the photodetector 156, and the + 1st-order diffracted light 108c is received by the photodetector 157.

FIG. 26 shows a pattern of the area division of the polarization anisotropic hologram element 121 as the division means and the photodetector 1.
56 and the detection area of the photodetector 157 and -1 on the photodetector
The cross sections of the first-order diffracted light 108b and the + 1st-order diffracted light 108c are shown. The polarization anisotropic hologram element 121 is divided into a plurality of strip-shaped regions.

The -1st-order diffracted light 108b generated from the area represented by the uppercase letters A and B is focused on the side farther from the collimator lens 103 than the -1st-order diffracted light 108b generated from the area represented by the lowercase letters a and b. You.

When the focal point F0 of the light emitted from the objective lens 104 coincides with the information layer 108 of the optical disk 105, the -1st-order diffracted light 108b with uppercase letters A and B on the photodetector 156 The optical system and the hologram element 121 are designed such that the cross section of the hologram element 121 and the cross section of the -1st-order diffracted light 108b to which the symbols of the small letters a and b are attached have the same size.

Signals obtained according to the amounts of light received from the detection areas 238 to 243 are referred to as signals f1 to f6, respectively.
The focus error signal FE is obtained by an operation corresponding to Expression 31 or Expression 32.

FE = (f1 + f3 + f5)-(f2 + f4 + f6) (Formula 31) FE = f5-f2 (Formula 32) The information layer 108 of the optical disk 105 is output from the objective lens 104. When moving away from the objective lens 104 from the focal point F0 of the emitted light, the symbols -1 with capital letters A and B are attached.
The cross-section of the first-order diffracted light 108b becomes smaller, and the cross-section of the -1st-order diffracted light 108b labeled with small letters a and b becomes larger. Therefore, the signals f1, f3, and f5 decrease, the signals f2, f4, and f6 increase, and the focus error signal FE decreases.

[0300] The information layer 108 of the optical disk 105 is moved from the focal point F0 of the light emitted from the objective lens 104 to the objective lens 1
As it approaches 04, the cross section of the -1st-order diffracted light 108b labeled with uppercase letters A and B increases, and the cross section of the -1st-order diffracted light 108b labeled with lowercase letters a and b decreases. Therefore, the signals f1, f3, and f
5 increases, signals f2, f4, and f6 decrease, and focus error signal FE increases.

Thus, in the eighth embodiment, the focal point F0
Can be realized on the information layer 108.

The detection areas 244 and 245 of the photodetector 157
Generates signals t1 and t2 according to the amount of light received. The tracking error signal TE1 can be obtained by the following equation 33 by the push-pull method.

TE1 = t1-t2 (Equation 33) The tracking error signal TE1 is substantially equivalent to the light amount in the non-hatched area and the hatched area of the polarization anisotropic hologram element 121 in FIG. Means the difference.

An RF signal for reproducing information is given by RFf derived by the following equation (34), RFt derived by the following equation (35), or the sum of both RFf and RFt.

RFf = f1 + f2 + f3 + f4 + f5 + f6 (Equation 34) RFt = t1 + t2 (Equation 35) Hereinafter, the deviation of the symmetry of the tracking error signal from that of the eighth embodiment and the conventional optical head will be described. The results of comparing the devices are shown.

The optical disc has a track composed of a groove or a pit row, and the interval from the center of a certain track to the center of an adjacent track is Tp. Also, the objective lens 10
The numerical aperture of 4 is NA, and the wavelength of light is λ.

In the eighth embodiment, the case where the condition of λ / (NA · Tp) ≧ 1 (Equation 36) is satisfied will be described.

The feature of the eighth embodiment is that an opening is a circle having a radius of 1, and an area included in a range of about 0.1 each having a width passing through the center of the opening and in contact with a division line parallel to a track of the optical disk 105 therebetween. In other words, the calculation is performed by exchanging the area included in the range of about 0.1 in width that is in contact with the edge of the opening.

A parting line 3 of a polarization anisotropic hologram element
On the left side of No. 02, the strip-shaped areas A and the strip-shaped areas a are alternately adjacent to each other,
On the right side of 02, strip-shaped areas B and strip-shaped areas b are alternately adjacent to each other. In FIG. 26, a total of two regions, that is, the rectangular region A and the rectangular region b are interchanged in the region near the center. In the region at the end of the opening, the strip-shaped area A and the strip-shaped area a and the strip-shaped area B and the strip-shaped area b are interchanged.

When the replacement as shown in this embodiment was not performed, the numerical aperture of the objective lens was set to 0.5, the light wavelength λ was set to 0.795 μm, and the light amount distribution in the radial direction Assuming that the intensity at the lens end is 10%, the deviation of the symmetry of the tracking error signal generated by the objective lens shift of 500 μm with respect to the pit row having the substrate thickness of the optical disk of 1.2 mm and the track interval Tp = 1.6 μm. Is 53%, and the deviation of the symmetry of the tracking error signal generated at a radial tilt of 1.0 degree is 24%.

On the other hand, in the case of the eighth embodiment, assuming that the width of the region at the center and both ends of the opening is 0.1 of the radius of the objective lens, the pit array having the track interval Tp = 1.6 μm is The deviation of the symmetry of the tracking error signal generated at a lens shift of 500 μm is 46%, and the deviation of the symmetry of the tracking error signal generated at a radial tilt of 1.0 degree is 12%. The deviation of the symmetry of the tracking error signal generated at an objective lens shift of 500 μm is reduced by 13% compared with the conventional example, and the deviation of the symmetry of the tracking error signal generated at a radial tilt of 1.0 ° is reduced by 50%, and is greatly reduced. Decrease. Therefore, it is possible to stabilize the tracking control, to be resistant to disturbance and the like, and to reduce the error rate at the time of information reproduction and the like.

In the simple two division, the difference between the focus position where the amplitude of the information reproduction signal is maximum and the focus position where the amplitude of the tracking error signal is maximum is 1.5 to 1.5.
What was 1.0 μm was changed to 1.0 μm in this embodiment.
０．５0.5 μm, which is reduced. For this reason, the error rate at the time of information reproduction can be kept low while also achieving stable tracking control.

In the eighth embodiment, the description has been made using the polarization anisotropic hologram element as the dividing means. However, the same effect can be obtained by using a normal hologram element having no polarization anisotropy.

In the eighth embodiment, the polarization anisotropic hologram element as the splitting means is driven integrally with the objective lens. However, the splitting means is connected to the optical path of the photodetector from the focusing optical system. Anywhere. in this case,
As the objective lens moves following the eccentricity of the track of the optical disc, the positional relationship between the dividing means and the aperture of the objective lens moves. However, if the pattern of the hologram element shown in the eighth embodiment is used, this movement is caused. Deterioration of the tracking error signal can be suppressed.

(Embodiment 9) A schematic diagram of an optical system of an optical head device according to Embodiment 9 is shown in FIG. 25, and the configuration and operation are the same as those in Embodiment 8, so that the description is omitted. . However, a polarization anisotropic hologram element 123 shown in FIG. 27 is used instead of the polarization anisotropic hologram element 121 as the dividing means.

In the ninth embodiment, a method for correcting a deviation of the symmetry of the tracking error signal will be described.

The polarization anisotropic hologram element 123 is shown in FIG.
7. The opening is a circle having a radius of 1 and has a width of about 0.6 around a dividing line passing through the center of the opening and parallel to the track.
Are alternately distributed, and the difference between the amount of light entering the shaded region and the amount of light entering the region without hatching is defined as a tracking error signal. In FIG. 27, four regions at the center of the opening are distributed.

Numerical aperture NA = 0.5, light wavelength λ = 0.7
It is assumed that 95 μm and the diameter of the objective lens = 4 mm, and that the light quantity distribution in the radial direction has an intensity of 10% at the end of the objective lens with respect to the center. In the conventional example in which the distribution is not performed, the deviation of the symmetry of the tracking error signal generated at an objective lens shift of 500 μm with respect to a pit row having a track interval Tp = 1.6 μm is 53%, and the radial tilt is 1.0 degree. The deviation in symmetry of the generated tracking error signal is 24%.

On the other hand, in another example of the ninth embodiment, it is assumed that the area alternately arranged at the center of the opening is an area having a width of 1.2 mm, which includes six areas having a width of 0.2 mm. When the objective lens shift is 500 μm, the deviation of the symmetry of the tracking error signal generated is 45%, and the deviation of the symmetry of the tracking error signal generated at a radial tilt of 1.0 degree is 14%. The deviation of the symmetry of the tracking error signal generated at an objective lens shift of 500 μm is reduced by about 15% of the conventional example, and the deviation of the symmetry of the tracking error signal generated at a radial tilt of 1.0 ° is reduced by about 42%. Yes, greatly reduced.

Regarding the objective lens shift, Embodiment 8
The effect is a little larger than the example. As described above, the tracking control can be stabilized, and it becomes strong against disturbance, so that the error rate at the time of information reproduction or the like decreases.

Although the ninth embodiment has been described using the polarization anisotropic hologram element as the dividing means, the same effect can be obtained by using a normal hologram element having no polarization anisotropy.

In the description of the first to ninth embodiments, an optical disk is assumed as an information storage medium.
Similar effects can be obtained with an optical card or the like.

In the description of the first to ninth embodiments described above, an infinite system using a collimator lens and an objective lens is used as the light-collecting optical system. However, the collimator lens is omitted, and the collimator uses only the objective lens. The effect of the present invention is not impaired even with a finite system configuration having the role of a lens.

(Embodiment 10) FIG. 28 is a configuration diagram showing an example of the tilt detection device of the present invention. Linearly polarized divergent beam 70 emitted from a semiconductor laser 101 as a light source
Is converted into parallel light by the collimator lens 103,
The light enters a polarization beam splitter 130 as a beam splitting element. All of the beams 70 incident on the polarizing beam splitter 130 pass through the polarizing beam splitter 130, pass through the quarter-wave plate 122, are converted into circularly polarized beams, and are stored in the objective lens 104 as a condensing optical system. The light is focused on the medium 105. The beam 70 reflected and diffracted by the information storage medium 105 passes through the objective lens 104 again, then passes through the quarter-wave plate 122 and passes through the light source 101.
Is converted into a beam of linearly polarized light in a direction different from that when emitted from The beam 70 transmitted through the 波長 wavelength plate 122 is reflected by the polarization beam splitter 130 and then enters the beam splitter 132. The beam 70 incident on the beam splitter 132 is divided into two beams 70
A, 70B and the beam 70B is
Is received at. On the other hand, the beam 70A is
At 3 it is converted to a convergent beam. The convergent beam 70A converted by the detection lens 133 passes through the parallel flat plate 134 and is received by the photodetector 158. When the beam 70A passes through the parallel plate 134, astigmatism for detecting a focus error signal is given to the beam 70A.
The beam 70A received by the photodetector 158 and the beam 70B received by the photodetector 159 are converted into electric signals corresponding to the light amounts. The electric signals output from the photodetectors 158 and 159 are input to the signal processing unit 700 in FIG.

FIG. 29 shows the structure of the signal processing section 700. The light detector 158 has four light receiving units 158A to 158
8D, and the photodetector 159 has two light-receiving portions 159A to 159A.
159B. Light receiving section 158A and light receiving section 158
The signal output from C is current-to-voltage converted by current-to-voltage converter 854, and the signal output from light-receiving unit 158B and light-receiving unit 158D is current-to-voltage converted by current-to-voltage converter 853, and the signal output from light-receiving unit 159A. Is subjected to current-to-voltage conversion by the current-to-voltage converter 852, and the signal output from the light receiving unit 159B is subjected to current-to-voltage conversion by the current-to-voltage converter 851. The signals output from the current-voltage converters 853 and 854 are subjected to a differential operation by an operation unit 874. The signal output from the arithmetic unit 874 is output from the terminal 811 and the output signal is a focus error signal.

On the other hand, current / voltage converters 851 and 852
The signal output from is subjected to a differential operation by the operation unit 871. The signal output from the arithmetic unit 871 is output from the terminal 812, and the output signal becomes a tracking error signal. The method of detecting the focus error signal is called an astigmatism method, and the method of detecting the tracking error signal is a known technique called a push-pull method.

The focus error signal and the tracking error signal are applied to a drive unit for focus control and an actuator 107 as a drive unit for tracking control, respectively. The relative position between the information storage medium 105 and the optical system is controlled so that the beam 70 emitted from the light source 101 is focused on a desired position on the information storage medium 105.

The signals output from current-voltage converters 851 and 852 are further added by adder 891.
The signal output from adder 891 is input to sample and hold units 821 and 822. In the sample and hold units 821 and 822, sampling and holding are performed at the timing of the signals Sa1 and Sa2 generated by the trigger signal generation unit 801. The signals output from the sample-and-hold units 821 and 822 are subjected to a differential operation by the operation
3 and becomes an inclination detection signal.

FIG. 30 shows the relationship between the pattern on the information storage medium 105 and the timing of the timing signal generated by the trigger signal generation unit 801. FIG.
In the formula, x represents a direction perpendicular to the track on which information is recorded, y represents a direction parallel to the track on which information is recorded, and z represents a direction perpendicular to x and y, respectively.

The information storage medium 105 has a first pattern area composed of a mark and a space and a second pattern area composed of a guide groove, and has a first pattern area and a second pattern area. Are alternately arranged in the y direction. In the second pattern area, Gn-1, Gn,
And Gn + 1 indicate guide grooves, respectively.

Gp is the distance between adjacent guide grooves. The data is recorded on or between the guide grooves in the second pattern area. Tn-2,... Tn + 2 indicate tracks on which information is recorded. In order to increase the capacity that can be recorded on the information storage medium 105, information can be recorded not only on the guide grooves but also between the guide grooves. Assuming that the interval between adjacent tracks is tp, the intervals Gp and tp
Has a relationship of Gp = 2 · tp. Here, Gp =
1.48 μm, the wavelength λ of the beam 70 emitted from the light source 101 is 650 nm, and the numerical aperture NA of the objective lens 104 is 0.6.

In the first pattern area, the mark 54 is located at a position different from the center position of the guide groove by ± Gp / 4 in the x direction.
1 and 542 are formed. Timings Sa1 and Sa2 included in the timing signal generated by the trigger signal generation unit 801 correspond to the positions of the marks 541 and 542 formed in the first pattern area, respectively. The tracking error signal is generated using a signal obtained from the photodetector 159 when the beam 70 condensed by the objective lens 104 irradiates the second pattern area. When the signal output from the terminal 812 is a tracking error signal, if the angle between the beam 70 condensed by the objective lens 104 and the information storage medium 105 is tilted, the output from the terminal 813 depends on the tilt angle. The signal to be changed changes.

FIG. 31a is a diagram schematically showing a part of the track of FIG. A and B in FIG. 31a refer to the trajectory of the focused beam. When the focused beam passes along the trajectory A, the waveform of the signal output from the adder 891 in FIG. 29 is shown in FIG. 31B, and the waveform of the signal output from the calculator 872 in FIG. 29 is shown in FIG. 31C. When the focused beam passes through the locus B, the adder 891 in FIG.
31d is shown in FIG. 31d, and the waveform of the signal output from the arithmetic unit 872 in FIG. 29 is shown in FIG. 31e.

In FIG. 31b, since the output signal from the adder 891 at the timing Sa1 and the timing Sa2 are equal, the output signal of the arithmetic unit 872 after the timing Sa2 becomes 0 as shown in FIG. 31c. On the other hand, FIG.
Since the value of the output signal from the adding unit 891 at the timing Sa1 differs from that at the timing Sa2, the value of the output signal of the calculating unit 872 after the timing Sa2 is different from 0 as shown in FIG. 31e.

FIG. 32 shows the relationship between the inclination of the angle formed by the beam 70 condensed by the objective lens 104 and the information storage medium 105 and the inclination detection signal obtained from the terminal 813, where Gp is 1.48 μm and 0.83 μm. The case at the time of is shown. 32, when the optical axis of the beam 70 condensed by the objective lens 104 is parallel to the z direction, that is, the optical axis of the beam 70 condensed by the objective lens 104 is orthogonal to the information storage medium 105. Corresponds to the state.

In both cases where Gp is 1.48 μm and 0.83 μm, a tilt signal can be detected in a range where the tilt angle is 1 degree or less, and the sensitivity is five times or more that of a conventional tilt detection device. This is because the inclination detection device of the present invention
This is based on the principle that the pattern of the pattern 05 and the phase of the beam diffracted by the guide groove change. G
When p is 1.48 μm, the detection sensitivity is as follows: Gp is 0.83
It is higher than the detection sensitivity at μm. This is because the principle of the present invention is that the detection sensitivity is increased by overlapping the ± 1st-order diffracted lights of the beam diffracted by the pattern and the guide groove in the information storage medium 105. The conditions under which the ± first-order diffracted lights overlap are expressed by the relationship of NA> λ / Gp. That is, when the optical system has a relationship of NA> λ / Gp, the tilt detection sensitivity increases.

By using the tilt detecting device of the present invention, the tilt of the angle formed between the information storage medium and the beam condensed by the condensing optical system can be detected more accurately than in the conventional tilt detecting device. In addition, tilt detection can be performed by using a photodetector that detects a tracking error signal, that is, there is no need to provide a new component as a detector to detect tilt, and an inexpensive and small tilt detector is provided. .

In this embodiment, the signal output from the terminal 812 is the tracking error signal, and the signal output from the terminal 813 is the inclination detection signal.
3 can be used as a tracking error signal and a signal output from a terminal 812 can be used as a tilt detection signal. In particular, even when the information storage medium 105 and the beam 70 condensed by the objective lens 104 are inclined, in an optical head device that does not include a drive unit that corrects the inclination, a signal output from the terminal 813 is used as a tracking error signal. Thereby, the beam 7 condensed by the objective lens 104
Even when 0 and the information storage medium 105 are inclined, the deviation between the position of the guide groove and the position of the track is small, and the compatibility when using a plurality of different optical head devices and information storage media is enhanced.

The tilt detection signal is used as a control signal for the drive unit 135 for driving the optical system as shown in FIG. 28, so that the information storage medium 105 and the beam 70 condensed by the objective lens 104 have a desired angle. , It is possible to realize an optical head device capable of stably reading information from the information storage medium 105 having many warpages. In addition, by controlling the beam intensity when recording information on the information storage medium 105 according to the tilt detection signal, it is possible to record information satisfactorily even on an information storage medium with a large amount of warpage. Become.

Here, the embodiment in which the photodetector 158 for detecting the focus error signal and the tracking error signal and the photodetector 159 for obtaining the tilt detection signal are separately shown, but the optical system shown in FIG. Can be used without any problem.

(Embodiment 11) FIG. 33 shows the configuration of a signal processing section 701 in a tilt detection apparatus according to another embodiment of the present invention. The signal processing unit 701 is described in, for example, Embodiment 10.
29 can be used in place of the signal processing unit 700 shown in FIG. 29 to configure a tilt detection device. The signal processing unit 701 is different from the signal processing unit 700 in that a sample and hold unit 823, a variable gain amplifying unit 831, and a calculation unit 873 are provided, and a timing signal output from a trigger signal generation unit 812. The sample and hold unit 823 includes a trigger signal generation unit 812
The sample-and-hold operation is performed using the timing signal having the timing of Sa3 output from the device. The timing of Sa3, as shown in FIG.
Is a position corresponding to a space in the first pattern area. The signal sampled by the sample-and-hold unit 823 is proportional to the offset generated in the tracking error signal when the objective lens moves in an optical system that drives the objective lens for tracking control as shown in FIG. Signal. For example, the signal output from the sample and hold unit is
The signal input to the variable gain amplifier 831 and the input signal is adjusted to a desired level. The signal output from the variable gain amplifying unit 831 is subjected to a differential operation by the operation unit 873 with the signal output from the operation unit 871. The signal output from the arithmetic unit 873 is output from a terminal 812. Arithmetic unit 8
By performing a differential operation on the signal output from the variable gain amplifying section 831 and the signal output from the arithmetic section 871 at 73, the offset generated in the tracking error signal is removed even if the objective lens is moved by tracking control. Therefore, a stable tracking operation can be performed, and a tilt signal can be accurately detected.

(Embodiment 12) FIG. 34 shows a configuration of an information storage medium in a tilt detection device according to another embodiment of the present invention.
And the configuration of the signal processing unit 702 is shown in FIG. The configuration of the information storage medium shown in the embodiment of the present invention is the embodiment 10
The difference from the configuration of the information storage medium shown by is that a plurality of marks 541 and 542 in the first pattern area are provided. The timings at which the sample-and-hold units 824 to 827 in the signal processing unit 702 sample the signals output from the adder 891 are Sa4 to Sa7, respectively,
41, 542 and a mirror portion between the marks. The signal having the sampling timing is generated by the trigger signal generation unit 803. Sample and hold section 8
Signals output from 24 and 825 are subjected to a differential operation in an operation unit 875, and signals output from sample and hold units 826 and 827 are subjected to a differential operation in an operation unit 876. The signals output from the operation units 875 and 876 are subjected to differential operation by the operation unit 872. The signal output from the arithmetic unit 872 is
The signal is output from the terminal 813 and becomes a tilt detection signal.

The tilt detection device using the information storage medium described in this embodiment can obtain a tilt signal with higher sensitivity than the tilt detection device described in Embodiment 10.

(Embodiment 13) FIG. 36 is a structural view showing an example of the optical head device of the present invention. The semiconductor laser 101 as a light source emits a beam 70 having a wavelength λ of 650 nm. The divergent beam 70 of linearly polarized light emitted from the semiconductor laser 101 is converted into parallel light by the collimator lens 103, and then enters a beam splitter 136 as a beam splitter. The beam splitter 136 is a half mirror whose optical characteristics do not depend on the polarization direction of the incident beam. Beam 7 incident on beam splitter 136
0 indicates that the beam having the intensity of １ ／ is the beam splitter 136.
Through. The beam 70 transmitted through the beam splitter 136 enters the polarizing filter 137.

FIG. 37 shows the structure of the polarizing filter 137. The polarizing filter 137 has two regions 137A,
137B. The region 137A has a characteristic that a beam polarized in the x direction is transmitted by 100% but a beam polarized in the y direction is not transmitted at all. The area 137B is
Both the beam polarized in the x direction and the beam polarized in the y direction are 1
It has the property of transmitting 00%. Here, the x direction is a radial direction of the information storage medium 105, and is a direction orthogonal to a track on which information is recorded. The y direction is a direction parallel to a track for recording information on the information storage medium 105,
It is orthogonal to the radial direction of the information storage medium 105. The z direction is
This is a direction perpendicular to both the radial direction and the track direction of the information storage medium 105, and is a direction parallel to the optical axis of the beam 70. In FIG. 37, reference numeral 70R denotes a mapping of the aperture of the objective lens 104. 70S represents the size of the area 137B. 70S is smaller than 70R, and the effective numerical aperture NA of the objective lens 104 for the beam polarized in the y direction.
Becomes smaller. Here, the effective numerical aperture NA of the objective lens 104 for the beam polarized in the x direction is 0.6,
The effective numerical aperture NA of the objective lens 104 for the beam polarized in the y direction is set to 0.4. Objective lens 10
The beam whose effective numerical aperture of No. 4 is 0.6 is the first beam, and the beam whose effective numerical aperture of the objective lens 104 is 0.4 is the second beam. As the beam polarized in the x direction and the y direction, a laser oscillating in both the TE mode and the TM mode may be used for the semiconductor laser 101, or a laser oscillating only in one of the TE and TM modes may be used as a light source. This can be realized by arranging the polarization direction of 101 slightly shifted from the x direction or y direction. Of course, the light source 101
May be incident on a wave plate to form a circular or elliptically polarized beam. In this embodiment, the polarization direction of the semiconductor laser 101 is slightly shifted from the x direction.

The beam 70 transmitted through the polarizing filter 137
Is incident on an objective lens 104 as a condensing optical system, and the beam 70 incident on the objective lens 104 is condensed on an information storage medium 105. The beam 70 reflected and diffracted by the information storage medium 105 passes through the objective lens 104 again and then passes through the polarizing filter 137. Polarizing filter 1
The beam 70 transmitted through the beam splitter 37 is incident on the beam splitter 136, and the beam having the intensity of が is changed to the beam splitter 13.
It is reflected at 6. The beam 70 reflected by the beam splitter 136 enters the polarization beam splitter 130. The polarizing beam splitter 130 has a characteristic of transmitting almost 100% of a beam polarized in the x direction and reflecting almost 100% of a beam polarized in the y direction. As for the beam 70 incident on the polarization beam splitter 130, the first beam passes through the polarization beam splitter 130 to become a beam 70A, and the second beam is the polarization beam splitter 1
The light is reflected at 30 and becomes a beam 70B. Beam 70B is received by photodetector 159. On the other hand, the beam 70A is converted into a convergent beam by the detection lens 133. The convergent beam 70 converted by the detection lens 133 is converted into a parallel plate 134
, And is received by the photodetector 158. Beam 7
When 0A is transmitted through the parallel plate 134, astigmatism is applied to the beam 70A so that a focus error signal can be detected. Beam 7 received by photodetector 158
0A, the beam 70B received by the photodetector 159 is converted into an electric signal corresponding to each light amount. The electric signals output from the photodetectors 158 and 159 are input to the signal processing unit 704.

FIG. 38 shows the structure of the signal processing unit 704. The light detector 158 has four light receiving sections 158A to 158.
D, the photodetector 159 has two light receiving sections 159A to 159B.
Consists of The signals output from the light receiving sections 158A and 158C are output from the current / voltage conversion section 854, and the signals output from the light receiving sections 158B and 158D are output from the current / voltage conversion section 8
At 53, the signal output from the light receiving unit 159A is subjected to current / voltage conversion by the current / voltage conversion unit 852, and the signal output from the light receiving unit 159B is subjected to current / voltage conversion by the current / voltage conversion unit 851. The signals output from the current-voltage converters 853 and 854 are subjected to a differential operation by the operation unit 872. The signal output from the arithmetic unit 872 is output from the terminal 812 and becomes a focus error signal. On the other hand, the current-voltage converters 851, 85
The signal output from 2 is subjected to a differential operation by an operation unit 871. The signal output from the arithmetic unit 871 is output from the terminal 811 and becomes a tracking error signal. The focus error signal and the tracking error signal are respectively applied to a drive unit for focus control and an actuator 107 as a drive unit for tracking control, and the beam 70 emitted from the light source 101 is focused on a desired position on the information storage medium 105. The relative position of the information storage medium 105 and the optical system is controlled so that

The information recorded in the information storage medium 105 is
It is obtained by adding the signals output from the current-voltage converters 853 and 854.

A guide groove for enabling detection of a tracking error signal is formed on the information storage medium 105, and its period Gp is 1.48 μm. In the optical head device of the present invention, the effective numerical aperture NA of the objective lens 104 with respect to the first beam for reading out the information recorded on the information storage medium 105 is 0.6, and the second numerical value for detecting the tracking error signal is used. By setting the effective numerical aperture NA of the objective lens 104 to the beam to 0.4, the objective lens 1
Even if the beam 70 converged at 04 and the information storage medium 105 are inclined from a regular angle, almost no phase shift occurs in the tracking error signal. Therefore, almost no off-track occurs. By applying the optical head device of the present invention, compatibility with different optical head devices and information storage media can be improved. Objective lens 104
The phenomenon in which a phase shift occurs in the tracking error signal when the beam 70 condensed in the above and the information storage medium 105 inclines from a regular angle becomes remarkable when the relationship of Gp> λ / NA is satisfied. Therefore, in the optical head device of the present invention, the effective numerical aperture NA of the objective lens 104 for the second beam for detecting the tracking error signal is Gp <Gp <
By giving a relationship of λ / NA, a good tracking error signal is obtained.

In the optical head device of the present invention, the objective lens 1
Two beams having different numerical apertures NA of 04 are generated so as to have exactly the same optical axis under any conditions by utilizing the difference in polarization. Therefore,
In the optical head device of the present invention, two beams are irradiated on the information storage medium 105, but the adjustment when assembling the optical head device is not complicated as compared with the conventional optical head device.

Since the optical head device of the present invention is not subject to any restrictions on the method of detecting a focus error signal, for example, the focus error signal may be detected using the second beam. At that time, a wavefront that allows detection of a focus error signal such as astigmatism may be given to the second beam. At this time, since the effective numerical aperture NA of the objective lens 21 of the second beam is smaller than that of the first beam, the wavefront aberration is also reduced. Therefore, when the focus error signal is detected by using the second beam, the beam condensed by the objective lens 43 on the information storage medium 43 is higher than when the focus error signal is detected by using the first beam. Since noise mixed into the focus error signal when traversing the track is reduced, more stable focus control can be realized.

In this embodiment, the beam splitter 136 is a half mirror. However, the optical head device of the present invention is not affected by the reflectance and transmittance characteristics of the beam splitter 136. 70 to 90
% And the reflectance may be 30 to 10%. When the beam splitter 136 is a half mirror, the signals output from the photodetectors 158 and 159 become maximum, and thus are suitable for a read-only optical head device. On the other hand, beam splitter 1
When the transmittance of 36 is 70% to 90%, the amount of light on the outward path from the semiconductor laser 101 to the information storage medium 105 increases, which is suitable for an optical head device for recording and reproduction.

In the present embodiment, the information storage medium 10 is used as a pattern for enabling detection of the tracking error signal.
Although a continuous guide groove is formed on the reference numeral 5, a discrete mark or a guide groove may be formed as a pattern enabling detection of a tracking error signal. In the case of an information storage medium in which discrete marks or guide grooves are formed, a sample and hold unit may be provided on the input side of the arithmetic unit 871 of the signal processing unit 704.

(Embodiment 14) FIG. 39 shows a configuration of an optical head device according to another embodiment of the present invention. In the present embodiment, focus and tracking control is performed by driving the objective lens 104 with an actuator as a driving unit. 107 is an actuator for focus control and tracking control. Further, the objective lens 104 and the polarizing filter 137 are integrally driven by the actuator 107. The beam 70 reflected and diffracted by the information storage medium 105 and then reflected by the beam splitter 136 is condensed by the detection lens 133. The beam 70 converted into a convergent beam by the detection lens 133
Enters the hologram element 138. From the hologram element 138, the 0th-order diffracted light 70C and the two first-order diffracted lights 70C
D and 70E are generated, and each of the beams 70C to 70E is received by the photodetector 160.

FIG. 40 schematically shows a pattern formed on the hologram element 138. Hologram element 1
In 38, an off-axis Fresnel zone plate is formed as a pattern. When the beam 70 condensed by the objective lens 104 is focused on the information storage medium 105, the first-order diffracted light 7 generated from the hologram element 138
0D is the first-order diffracted light 70 nearer to the photodetector 160.
E has a focal point on the back side of the photodetector 160. The hologram element 138 has a polarization dependency on the diffraction efficiency. For a beam polarized in the x direction, the diffraction efficiency of the 0th-order diffracted light is 0% and the diffraction efficiency of the ± 1st-order diffracted light is 4%.
0%, for a beam polarized in the y direction, the diffraction efficiency of the 0th-order diffracted light is 100%, and the diffraction efficiency of the ± 1st-order diffracted light is 0%.
It is designed to be. The pattern on the hologram element 138 is produced by proton exchange of lithium niobate.

FIG. 41 shows the relationship between the light receiving section of the photodetector 160 and the beams 70C to 70E. The photodetector 160 has light receiving units 160A to 160H. The beam 70C is received by the light receiving units 160A to 160B, and the beam 70D
Are received by the light receiving units 160C to 160E, and the beam 70E is received by the light receiving units 160F to 160H. In the optical head device of the present embodiment, the signal processing unit can use the signal processing unit 704 described in the thirteenth embodiment as it is. The signal output from the light receiving unit 160A is sent to the current / voltage converting unit 852, the signal output from the light receiving unit 160B is sent to the current / voltage converting unit 851, and the light receiving units 160D, 160F, 16
The signal output from 0H may be input to the current-voltage conversion unit 854, and the signal output from the light receiving units 160C, 160E, and 160G may be input to the current-voltage conversion unit 853. The method of detecting a focus error signal described in the present embodiment is a method called a spot size detection method, and this method is well known as in the case of the astigmatism method.

In the embodiment of the present invention, the objective lens 104
The center of the objective lens 104 and the center of the polarizing filter 137 can always be matched by driving the actuator and the polarizing filter 137 integrally. At this time, the second beam is condensed on the information storage medium 105 with little aberration, and even if the beam 70 condensed by the objective lens 104 and the information storage medium 105 are tilted, a phase shift or offset is generated. A small tracking error signal can be obtained.

Also, by using the hologram element 138, a focus error signal, a tracking error signal, and an information signal recorded on the information storage medium 105 can be detected from one photodetector 160, so that an inexpensive optical head device can be used. Becomes

[0359]

As described above, according to the optical head device of the present invention, mainly the following effects can be obtained.

(1) Even when an objective lens shift or a radial tilt occurs, the tracking error signal value TE0 obtained when light is applied to the center of the track and the tracking error signal obtained when the track is traversed. Absolute values | TEmax−TE0 | and | TEmin−TE0 | of the respective differences between the maximum value TEmax and the minimum value TEmin of
Can be reduced. At this time, even if the off-track amount is corrected to 0, a deviation in symmetry of the tracking error signal can be suppressed, so that stable tracking control can be realized.

(2) Even if a position deviated from the track is scanned at the focal point, information recorded on the track can be reproduced stably with a low error rate.

(3) Since a gain variation of the focus error signal can be suppressed, stable focus control can be realized.

As described above, the error rate can be suppressed to a small value at the time of reproducing the information, and the writing operation and the erasing operation can be stably performed at the time of writing and erasing the information. An optical information processing device that enhances compatibility with respect to.

Further, according to the tilt detection device of the present invention, a tilt signal can be detected accurately even when the tilt angle of the beam focused by the information storage medium and the focusing optical system is 1 degree or less.

Further, by using the optical information processing apparatus of the present invention, it is possible to stably record and reproduce information even on an information storage medium with a lot of warpage.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of an optical system of an optical head device according to an embodiment of the present invention.

FIG. 2 is a configuration diagram of a detection area of an optical detector, an information reproduction signal generation unit, and a circuit as a tracking error signal generation unit according to an embodiment of the present invention.

FIG. 3 is a diagram showing a tracking error signal when a radial tilt exists, a positional relationship between tracks, and a tracking error signal when an off-track amount is corrected to zero.

FIG. 4 is a configuration diagram of a circuit as another detection area, an information reproduction signal generation unit, and a tracking error signal generation unit of the photodetector according to the embodiment of the present invention.

FIG. 5 is a plan view showing still another detection area of the photodetector showing one embodiment of the present invention.

FIG. 6 is a plan view showing another detection area of the photodetector according to the embodiment of the present invention.

FIG. 7 is a configuration diagram of a detection area of a photodetector and a circuit as a tracking error signal generation unit according to an embodiment of the present invention.

FIG. 8 is a configuration diagram of a detection region of a photodetector and a circuit as a tracking error signal generation unit according to an embodiment of the present invention.

FIG. 9 is a configuration diagram of a detection region of a photodetector and a circuit as a tracking error signal generation unit according to an embodiment of the present invention.

FIG. 10a is a schematic diagram of an optical system of an optical head device according to an embodiment of the present invention.

FIG. 10b is a front view of the objective lens showing one embodiment of the present invention.

FIG. 11 is a schematic view of an optical system using another dimming means of the optical head device according to the embodiment of the present invention.

FIG. 12 is a schematic diagram of an optical system using an optical head device according to an embodiment of the present invention and another dimming unit.

FIG. 13 is a schematic diagram of an optical system using another dimming means of the optical head device showing one embodiment of the present invention.

FIG. 14 is a schematic diagram of an optical system of an optical head device according to an embodiment of the present invention.

FIG. 15 is a plan view showing the relationship between the area arrangement of the hologram element, the area division of the photodetector, and the cross section of the diffracted light on the photodetector, showing one embodiment of the present invention.

FIG. 16 is a front view showing another region arrangement of the hologram element showing one embodiment of the present invention.

FIG. 17 is a schematic view of an example of another optical system of the optical head device showing one embodiment of the present invention.

FIG. 18 is a configuration diagram of a detection region of a photodetector, a circuit as a tracking error signal generation unit, and a circuit as an information reproduction signal generation unit according to an embodiment of the present invention.

FIG. 19a is a layout diagram of tracks on an optical disc.

FIG. 19b is a schematic diagram of a circuit as an information reproduction signal generating means when reproducing off-track information according to an embodiment of the present invention.

FIG. 19c is a schematic diagram of a circuit as an information reproduction signal generating means when reproducing off-track information, showing an embodiment of the present invention.

FIG. 20 is a configuration diagram of a detection region of another photodetector, a circuit as a tracking error signal generation unit, and a circuit as an information reproduction signal generation unit, showing one embodiment of the present invention.

FIG. 21a is a layout diagram of tracks on an optical disc.

FIG. 21b is a schematic diagram of another example of a circuit as an information reproduction signal generating means when reproducing off-track information according to an embodiment of the present invention.

FIG. 21c is a schematic diagram of another example of a circuit as an information reproduction signal generating means when reproducing off-track information, according to an embodiment of the present invention.

FIG. 22a is a layout diagram of tracks on an optical disc.

FIG. 22b is a schematic diagram of another example of a circuit as an information reproduction signal generating means when reproducing off-track information, according to an embodiment of the present invention.

FIG. 23a is a layout diagram of tracks on an optical disc.

FIG. 23b is a schematic diagram of another example of the circuit as the information reproduction signal generation means when reproducing the information that has been off-track;

FIG. 24 is a plan view showing the relationship between the area arrangement of the hologram element, the area division of the photodetector, and the cross section of the diffracted light on the photodetector, showing one embodiment of the present invention.

FIG. 25 is a schematic diagram of an optical system of an optical head device according to an embodiment of the present invention.

FIG. 26 is a plan view showing the relationship between the area arrangement of the hologram element, the area division of the photodetector, and the cross section of the diffracted light on the photodetector, showing one embodiment of the present invention.

FIG. 27 is a front view showing another region arrangement of the hologram element showing one embodiment of the present invention.

FIG. 28 is a configuration diagram of a tilt detection device showing one embodiment of the present invention.

FIG. 29 is a configuration diagram of a signal processing unit in a tilt detection device according to an embodiment of the present invention.

FIG. 30 is a configuration diagram of an information storage medium used in a tilt detection device according to an embodiment of the present invention.

FIG. 31a is a diagram schematically showing a part of the track of FIG. 30;

31B is a diagram illustrating a waveform of a signal output from the adding unit 891 in FIG. 29 when a focused beam passes along a locus A in FIG. 31A.

31C is a diagram illustrating a waveform of a signal output from the calculation unit 872 in FIG. 29 when a focused beam passes along a locus A in FIG. 31A.

31D is a diagram illustrating a waveform of a signal output from the adding unit 891 in FIG. 29 when a focused beam passes along a locus B in FIG. 31A.

31e is a diagram illustrating a waveform of a signal output from the calculation unit 872 in FIG. 29 when a focused beam passes along a locus B in FIG. 31a.

FIG. 32 is a diagram illustrating characteristics of a tilt detection signal obtained from a tilt detection device according to an embodiment of the present invention.

FIG. 33 is a configuration diagram of a signal processing unit in a tilt detection device according to an embodiment of the present invention.

FIG. 34 is a configuration diagram of an information storage medium used in a tilt detection device according to an embodiment of the present invention.

FIG. 35 is a configuration diagram of a signal processing unit in a tilt detection device according to an embodiment of the present invention.

FIG. 36 is a configuration diagram of an optical head device showing one embodiment of the present invention.

FIG. 37 is a configuration diagram of a polarizing filter in an optical head device according to an embodiment of the present invention.

FIG. 38 is a configuration diagram of a signal processing unit in an optical head device according to an embodiment of the present invention.

FIG. 39 is a configuration diagram of an optical head device showing one embodiment of the present invention.

FIG. 40 is a configuration diagram of a hologram element in an optical head device according to an embodiment of the present invention.

FIG. 41 is a diagram showing the relationship between a photodetector and a beam in an optical head device according to an embodiment of the present invention.

FIG. 42 is a schematic view of an optical system of an optical head device showing a conventional example.

FIG. 43a shows an embodiment of the present invention and a conventional example in which the detection area of the photodetector and the information layer on the photodetector when the focal point of light emitted from the objective lens coincides with the information layer. FIG. 4 is a plan view showing a cross section of reflected light of FIG.

FIG. 43B shows an embodiment of the present invention and a detection area of a light detector according to a conventional example and an information layer on the light detector when the information layer moves away from a focal point of light emitted from an objective lens. FIG. 4 is a plan view showing a cross section of reflected light of FIG.

FIG. 43c shows an embodiment of the present invention and an information layer on the photodetector when approaching the information layer from the focal point of light emitted from the objective lens and the detection area of the photodetector showing the conventional example. FIG. 4 is a plan view showing a cross section of reflected light of FIG.

FIG. 44 is a configuration diagram of a conventional inclination detection device.

FIG. 45 is a configuration diagram of an information storage medium used in a conventional inclination detection device.

FIG. 46 is a configuration diagram of a signal processing unit in a conventional inclination detection device.

FIG. 47 is a configuration diagram of a conventional optical head device.

FIG. 48 is a configuration diagram of a signal processing unit in a conventional optical head device.

FIG. 49 is a configuration diagram of an information storage medium used in a conventional optical head device.

[Explanation of symbols]

 Reference Signs List 101 semiconductor laser 102 parallel plate beam splitter 103 collimator lens 104 objective lens 105 optical disk 106 holding means 107 actuator 108 information layer 108a reflected light

 ──────────────────────────────────────────────────の Continuing on the front page (72) Kenichi Kasumi, 1006 Kadoma Kadoma, Osaka Prefecture, Matsushita Electric Industrial Co., Ltd.

Claims (49)

[Claims] 1. A laser beam source for emitting a coherent beam or a quasi-monochromatic beam, and a collector for focusing a beam emitted from the light source on an information storage medium having a track on which at least one mark and at least one space are arranged. An optical optical system, a photodetector having a plurality of detection regions for receiving reflected light reflected by the information storage medium and outputting a signal corresponding to the amount of the received reflected light, and a photodetector output from the photodetector. And a tracking error signal generating means for generating a tracking error signal based on the received signal, the tracking error signal generating means reducing a difference between the first signal amplitude and the second signal amplitude, The first signal amplitude is an absolute value of a difference between a first signal level and a second signal level, and the second signal amplitude is an absolute value of the difference between the first signal level and a third signal level. The first signal level is a value of a tracking error signal obtained when the light emitted from the light source is applied to the center of the track, and the second signal level is the second signal level. The signal level is the maximum value of the tracking error signal when the light emitted from the light source is scanned in a direction orthogonal to the track, and the third signal level is the light emitted from the light source. An optical head device which is a minimum value of a tracking error signal when scanning is performed in a direction orthogonal to a track. 2. A laser beam source for emitting a coherent beam or a quasi-monochromatic beam, and a focusing device for focusing a beam emitted from the light source on an information storage medium having a track on which at least one mark and at least one space are arranged. An optical optical system, a photodetector having a plurality of detection regions for receiving reflected light reflected by the information storage medium and outputting a signal corresponding to the amount of the received reflected light, and a photodetector output from the photodetector. And a tracking error signal generating means for generating a tracking error signal based on the received signal. The tracking error signal generating means converts a component of a signal obtained from the overlapping area from the tracking error signal. The overlapping area is defined such that, when the opening of the light-collecting optical system is a circle having a radius of 1, the track is positioned from the center of the opening of the light-collecting optical system. A region where two circles each having a radius of 1 centered on two points separated by λ / (NA · Gp) in the orthogonal direction, respectively, where λ is the wavelength of light emitted from the light source; The NA is the numerical aperture of the light-collecting optical system, the Gp is the distance from the center of a track to the center of an adjacent track in the information storage medium, and the aperture of the light-collecting optical system is Λ / (N
A · Gp) is an optical head device having a relationship of λ / (NA · Gp) <1. 3. A laser beam source for emitting a coherent beam or a quasi-monochromatic beam, and a collector for focusing a beam emitted from the light source on an information storage medium having a track in which at least one mark and at least one space are arranged. An optical optical system, a photodetector having a plurality of detection regions for receiving reflected light reflected by the information storage medium and outputting a signal corresponding to the amount of the received reflected light, and a photodetector output from the photodetector. And a tracking error signal generating means for generating a tracking error signal based on the received signal, and it is possible to divide an overlapping area of the reflected light and an area in the vicinity thereof and receive the divided light by the photodetector. Dividing means, wherein the overlapping area is orthogonal to the track from the center of the opening of the light-collecting optical system when the opening of the light-collecting optical system is a circle having a radius of 1. Is an overlapping area of two circles each having a radius of 1 centered on two points separated by λ / (NA · Gp) in the direction, and λ is the wavelength of light emitted from the light source; Is the numerical aperture of the converging optical system, Gp is the distance from the center of the track to the center of the adjacent track in the information storage medium, and λ / (NA · Gp) is λ / (NA Gp) An optical head device having a relationship of <1. 4. The tracking error signal generating means,
4. The optical head device according to claim 3, wherein a tracking error signal is generated using a signal obtained from a detection region that receives light in a region not including the overlapping region in the reflected light. 5. 5. The dividing means has at least two dividing lines substantially parallel to a track, and the at least two dividing lines are arranged so as to sandwich the overlapping area of the reflected light therebetween. The tracking error signal generating means includes the at least two
5. The optical head device according to claim 4, wherein a tracking error signal is generated by calculating a signal obtained from a detection region that receives reflected light incident on a region outside the division line. 6. The tracking error signal generating means,
4. The optical head device according to claim 3, wherein a tracking error signal is corrected by using a signal obtained from a detection area that receives light in the overlap area and the vicinity area of the reflected light. 7. The dividing means has N dividing lines substantially parallel to a tangent of the track, N is an odd number of 3 or more, and two of the N dividing lines are And (N-2) dividing lines excluding the two dividing lines are disposed between the two dividing lines, with the overlapping region of the reflected light interposed therebetween. The error signal generation means uses a signal obtained from a detection area that receives the reflected light incident on the first area and the second area that are located outside the two division lines and that do not include the overlap area. A tracking error signal is generated, and the polarity of a signal obtained from a detection area that receives the reflected light incident on an even number of areas sandwiched between the two division lines is alternately inverted. Generating a correction signal for adding the obtained signals; and performing the correction from the tracking error signal. 7. The optical head device according to claim 6, wherein the signal is added or subtracted. 8. The dividing means has N dividing lines substantially parallel to a tangent line of the track, where N is an odd number of 3 or more, and two of the N dividing lines. Are arranged so as to sandwich the overlapping area of the reflected light therebetween, and (N-2) dividing lines excluding the two dividing lines are arranged between the two dividing lines, The error signal generation means multiplies a signal obtained from a detection area receiving the reflected light incident on an even number of areas sandwiched between the two division lines by a predetermined value, and multiplies the signal multiplied by the predetermined value. 7. The optical head device according to claim 6, wherein a correction signal is generated by alternately inverting the polarities of the signals, and a signal having the alternately inverted polarity is added, and the correction signal is added or subtracted from the tracking error signal. 9. The optical head device according to claim 3, wherein said dividing means is a hologram element. 10. The optical head device according to claim 3, wherein the dividing unit is integrated with the light collecting optical system. 11. The optical head device according to claim 3, wherein the division unit is a division line of the photodetector. 12. A laser beam source for emitting a coherent beam or a quasi-monochromatic beam, and a collector for condensing light emitted from the light source on an information storage medium having a track in which at least one mark and at least one space are arranged. An optical optical system, a photodetector having a plurality of detection areas for receiving reflected light reflected by the information storage medium and outputting a signal corresponding to the amount of the received reflected light, and an output from the photodetector. And a tracking error signal generating means for generating a tracking error signal based on the received signal, provided in an optical path, and comprising a dimming means for reducing the transmittance of light in the overlapping area and in the vicinity thereof. Further, when the aperture of the light-collecting optical system is a circle having a radius of 1, the overlap region is formed in a direction orthogonal to the track from the center of the light-opening optical system. An area where two circles each having a radius of 1 centered on two points separated by (NA · Gp), respectively, are overlapped, λ is the wavelength of light emitted from the light source, and NA is the collection point. Gp is the distance from the track center to the adjacent track center in the information storage medium, and λ / (NA · Gp) is λ / (NA · Gp) <1. An optical head device having a relationship. 13. The optical head device according to claim 12, wherein said dimming means is integrated with said condensing optical system. 14. The optical head device according to claim 12, wherein the light reducing means is a hologram element. 15. A laser light source that emits a coherent beam or a quasi-monochromatic beam, an optical element that receives a beam emitted from the light source, splits the received beam into a first beam and a second beam, A condensing optical system that receives one beam and the second beam and converges the first beam and the second beam into a minute spot on an information storage medium; a beam reflected and diffracted by the information storage medium And a beam splitter for splitting the received beam; a photodetector for receiving the beam split by the beam splitter and outputting a signal corresponding to the amount of the received beam; and a photodetector output from the photodetector. A signal processing unit for receiving the received signal and calculating the received signal; and a relative position between the condensing optical system and the information storage medium based on the signal output from the signal processing unit. A driving unit for determining the first beam, wherein the first beam and the second beam have different effective numerical apertures when condensed by the condensing optical system; An optical head device further comprising a tracking error signal generating means for generating a tracking error signal using a beam having a small effective numerical aperture at the time of performing. 16. The information storage medium has a mark or a predetermined groove for enabling detection of a tracking error signal, and sets a period of the mark or the predetermined groove for enabling detection of the tracking error signal on the information storage medium. Gp, the wavelength of the beam emitted from the light source is λ, and the numerical aperture on the information storage medium side of the focusing optical system is NA, the first beam generated by the optical element is Gp> λ. / N
A, the second beam generated by the optical element has a relationship of Gp <λ / NA, and the tracking error signal generating means generates a tracking error signal from the second beam. The optical head device according to claim 15. 17. The optical head device according to claim 15, wherein the first beam and the second beam are formed coaxially with each other. 18. The optical head device according to claim 15, wherein the optical element is a polarizing filter. 19. The optical head device according to claim 15, wherein the optical element is integrated with the light-collecting optical system. 20. A laser light source that emits a coherent beam or a quasi-monochromatic beam, a condensing optical system that receives a beam emitted from the light source, and converges the received beam to a minute spot on an information storage medium; A beam splitter that receives the beam reflected and diffracted by the storage medium and splits the received beam; a photodetector that receives the beam split by the beam splitter and outputs a signal corresponding to the amount of the received beam; A signal processing unit that receives a signal output from the photodetector and calculates the received signal; and performs focus and tracking control to perform relative positioning between the condensing optical system and the information storage medium. A tilt detector including a drive unit, wherein the photodetector has a plurality of light receiving units, and the information storage medium has a mark and a space. A first pattern region comprising a first pattern region and a second pattern region comprising a predetermined groove, wherein the first pattern region and the second pattern region are alternately arranged on an information storage medium; The unit uses a signal obtained from the photodetector when the beam focused by the focusing optical system is irradiated on the first pattern area or the second pattern area,
A tilt detecting device for detecting an angle formed between the beam focused by the focusing optical system and the information storage medium; 21. When a beam focused by the focusing optical system irradiates a mark and a space in the first pattern area, tracking control is performed using a signal obtained from the photodetector, When the beam focused by the focusing optical system irradiates the second pattern area, the beam focused by the focusing optical system using the signal obtained from the photodetector and the information storage medium 21. The tilt detection device according to claim 20, wherein the angle detection device detects an angle between the inclination angle and the angle. 22. When a beam focused by the focusing optical system irradiates the second pattern area, tracking control is performed using a signal obtained from the photodetector, and the focusing optical system is controlled. When the beam condensed by irradiates the first pattern area, the angle formed between the beam condensed by the condensing optical system using the signal obtained from the photodetector and the information storage medium 21. The tilt detection device according to claim 20, wherein the inclination is detected. 23. A beam collected by the light-collecting optical system using a signal obtained from the photodetector when the beam focused on the mark and space in the first pattern area is irradiated. 21. The tilt detecting device according to claim 20, wherein an angle formed between the light beam and the information storage medium is detected. 24. A period of the first pattern area or the second pattern area is Gp, a wavelength of a beam emitted from the light source is λ, and an opening of the light-collecting optical system on the information storage medium side. 24. The tilt detection device according to claim 20, wherein, when the number is represented by NA, NA> λ / Gp. 25. A laser light source that emits a coherent beam or a quasi-monochromatic beam, a condensing optical system that receives a beam emitted from the light source, and converges the received beam to a minute spot on an information storage medium; A beam splitter that receives the beam reflected and diffracted by the storage medium and splits the received beam; a photodetector that receives the beam split by the beam splitter and outputs a signal corresponding to the amount of the received beam; A signal processing unit that receives a signal output from the photodetector and calculates the received signal; and performs focus and tracking control to perform relative positioning between the condensing optical system and the information storage medium. A first drive unit, a second drive unit capable of changing an angle formed between the beam focused by the focusing optical system and the information storage medium, Wherein the photodetector has a plurality of light receiving sections, and the information storage medium has a pattern or a predetermined groove capable of generating a tracking error signal, and a pattern or a pattern capable of generating the tracking error signal. When the period of the predetermined groove is Gp, the wavelength of the beam emitted from the light source is λ, and the numerical aperture of the focusing optical system on the information storage medium side is NA, the relationship of NA> λ / Gp is satisfied. An optical information processing device. 26. A laser light source that emits a coherent beam or a quasi-monochromatic beam, a condensing optical system that receives a beam emitted from the light source, and converges the received beam to a minute spot on an information storage medium; A beam splitter that receives the beam reflected and diffracted by the storage medium and splits the received beam; a photodetector that receives the beam split by the beam splitter and outputs a signal corresponding to the amount of the received beam; A signal processing unit that receives a signal output from the photodetector and calculates the received signal; and controls focus and tracking to perform relative positioning between the condensing optical system and the information storage medium. A first drive unit, a second drive unit capable of changing an angle formed between the beam focused by the focusing optical system and the information storage medium, Wherein the photodetector has a plurality of light receiving portions, and the information storage medium has a first pattern region comprising a mark and a space and a second pattern region comprising a predetermined groove; The pattern area and the second pattern area are alternately arranged on the information storage medium, and the signal processing unit is configured to transmit the beam focused by the focusing optical system to the first pattern area or the second pattern. When the area is illuminated, using the signal obtained from the photodetector,
An optical information processing apparatus for detecting an angle between a beam focused by the focusing optical system and the information storage medium and generating a signal for driving the second drive unit. 27. When a beam focused by the focusing optical system irradiates a mark in the first pattern area, tracking control is performed using a signal obtained from the photodetector, When the beam focused by the optical system irradiates the second pattern area, the signal focused by the focusing optical system and the information storage medium are used by using a signal obtained from the photodetector. 27. The optical information processing device according to claim 26, wherein the angle formed by the optical information processing device is detected. 28. When a beam focused by the focusing optical system irradiates the second pattern area, tracking control is performed using a signal obtained from the photodetector, When the beam condensed by irradiates the first pattern area, the angle formed between the beam condensed by the condensing optical system and the information storage medium using a signal obtained from the photodetector. 27. The optical information processing apparatus according to claim 26, wherein the optical information processing apparatus detects an error. 29. When a beam focused by the focusing optical system irradiates a mark and a space in the first pattern area, the focusing optical system uses a signal obtained from the photodetector. 27. The optical information processing apparatus according to claim 26, wherein an angle formed between the beam condensed by the information storage medium and the information storage medium is detected. 30. A period of the first pattern area or the second pattern area is defined as Gp, a wavelength of a beam emitted from the light source is defined as λ, and an opening of the focusing optical system on the information storage medium side. When the number is NA, NA> λ /
The optical information processing device according to any one of claims 26 to 29, wherein the optical information processing device has a relationship of Gp. 31. A light source that emits a coherent beam or a quasi-monochromatic beam, a focusing optical system that focuses a beam emitted from the light source on an information storage medium having a track where marks or spaces are selectively arranged, A photodetector comprising a plurality of detection regions for receiving reflected light reflected by the information storage medium and outputting a signal corresponding to the amount of the received reflected light; splitting the light reflected by the information storage medium; A dividing unit for allowing light to be received by the detector, and a dividing unit which is obtained in accordance with the reflected light incident on each of two predetermined regions divided by a dividing line on the dividing unit, a first region and a second region An information reproduction signal generating means for generating a reproduction signal for reproducing information recorded on the track from a differential signal of the signal; point An optical head apparatus further comprising a changing means for changing the range included in the first region or the second region or both regions in accordance with the positional relationship between said track. 32. When a cross section of the reflected light on the dividing means is a substantially circle having a radius of 1, the dividing means is substantially parallel to a tangent of the track and is a predetermined distance d from the center of the substantially circle. A separated first dividing line and a second dividing line substantially parallel to a tangent to the track and opposite to the first dividing line and separated from the center by a distance d.
Are divided into three regions by the dividing line, and the outside of the first dividing line not including the center of the substantially circle is the region A, and the region sandwiched between the first dividing line and the second dividing line. Is defined as a region B, and a region outside the second dividing line that does not include the center of the substantially circle is defined as a region C. When scanning a first position at a predetermined distance to one side of the track, information recorded on the track is defined as area A as the first area, area B and area C as the second area. Wherein the information reproduction signal generation means separates the focal point of the light emitted from the focusing optical system by a predetermined distance on the opposite side of the track from the first position. When scanning the second position, the area A and the area B are set as the first area, and the area C is set as the second area. The optical head device according to claim 31 for generating a reproduction signal of information recorded on the track. 33. When the cross section of the reflected light on the dividing means is a substantially circle having a radius of 1, the dividing means is substantially parallel to a tangent of the track and is separated from a center of the substantially circle by a predetermined distance d. And the first dividing line substantially parallel to the tangent to the track and
A second dividing line opposite to the center by a distance d from the center, and a third dividing line substantially parallel to the tangent to the track and passing through the center of the substantially circle. A region A outside the first dividing line that does not include the center of the substantially circle, a region B between the first dividing line and the third dividing line, and the second dividing line And a region sandwiched between the third division line and a region C, and a region outside the second division line that does not include the center of the substantial circle as a region D. When the light-converging point scans a first position at a predetermined distance to one side of the track, the area A is regarded as the first area, and the area C and the area D are scanned.
As the second area, the information reproduction signal generation means includes:
A reproduction signal of information recorded on the track is generated, and a light condensing point of light emitted from the light condensing optical system is separated by a predetermined distance on a side opposite to the first position on the track. 2
When the position A is scanned, the area A and the area B are set as the first area, and the area D is set as the second area. 32. The optical head device according to claim 31, wherein: 34. A light source for emitting a coherent beam or a quasi-monochromatic beam, a focusing optical system for focusing a beam emitted from the light source on an information storage medium having a track on which marks or spaces are selectively arranged, A photodetector comprising a plurality of detection regions for receiving reflected light reflected by the information storage medium and outputting a signal corresponding to the amount of the received reflected light; and dividing the reflected light reflected by the information storage medium. Dividing means for allowing light to be received by the photodetector, and a dividing means which is obtained in accordance with the reflected light incident on each of two predetermined first and second areas divided by the dividing means. An information reproduction signal generating means for generating a reproduction signal for reproducing information recorded on the track from a differential signal of the signal, wherein a cross section of the reflected light on the division means has a radius of Abbreviation of 1 The dividing means is divided into three regions by two dividing lines substantially parallel to the tangent line of the track and separated by a predetermined distance d from the center of the substantial circle. A region not including the center of the circle is defined as the first region, another region not including the center of the substantially circle is defined as the second region, and a light-collecting point of light emitted from the light-collecting optical system is An optical head device for generating a reproduction signal of information recorded on the track when scanning a position separated by a predetermined distance from the track; 35. A light source for emitting a coherent beam or a quasi-monochromatic beam, a condensing optical system for condensing light emitted from the light source on an information storage medium having a track on which marks or spaces are selectively arranged, A photodetector comprising a plurality of detection areas for receiving reflected light reflected by the information storage medium and outputting a signal corresponding to the amount of received reflection, dividing the reflected light reflected by the information storage medium, Dividing means for allowing light to be received by the photodetector; and a predetermined first area and a second area divided by the dividing means.
Information reproduction signal generation means for generating a reproduction signal for reproducing information recorded on the track from a differential signal of a signal obtained according to the reflected light incident on each of the two areas In the optical head device, when the cross section of the reflected light on the dividing means is a substantially circle having a radius of 1, the dividing means is substantially parallel to a tangent to the track and is a predetermined distance d from the center of the substantially circle. Two separate dividing lines first
Are divided into four regions by a dividing line, a second dividing line, and a third dividing line passing through the center of the substantial circle, and the first region which does not include the center of the substantial circle out of the four regions. Two regions, a region outside the dividing line, the third dividing line, and a region sandwiched by the second dividing line, are defined as the first region, and the first dividing line and the third dividing line And a region outside the second parting line that does not include the center of the substantially circle as the second region, and a light condensing point of light emitted from the light condensing optical system. An optical head device wherein, when scanning a position separated by a predetermined distance from the track, the information reproduction signal generation means generates a reproduction signal of information recorded on the track. 36. When the cross section of the reflected light on the dividing means is a substantially circle having a radius of 1, the distance d from the center of the substantially circle on the dividing means to the dividing line is 0.1 or more. 36. The optical head device according to claim 31, wherein the number is 3 or less. 37. A light source emitting a coherent beam or a quasi-monochromatic beam, and a beam emitted from the light source condensed on an information storage medium having a track on which marks or spaces are selectively arranged or a track comprising a predetermined groove. A light collecting optical system, a light detector having a plurality of detection areas for receiving reflected light reflected by the information storage medium and outputting a signal corresponding to the amount of the received reflected light, and an output from the light detector. And a tracking error signal generating means for generating a tracking error signal based on the received signal, dividing the reflected light reflected by the information storage medium, and receiving the divided reflected light by the photodetector. Splitting means for enabling the light source, the wavelength of the light emitted from the light source is λ, the numerical aperture of the condensing optical system is NA, Gp is the distance from the center of the track to the center of the adjacent track, and has a relationship of λ / (NA · Gp) ≧ 1, and the cross section of the reflected light on the dividing means is a circle having a radius of 1. The dividing means has at least five dividing lines substantially parallel to a tangent of the track, a first dividing line passing through the center of the cross section of the reflected light on the dividing means and parallel to the track; Two division lines located at a distance of about 0.1 across the first division line are defined as a second division line and a third division line, and the distance from the end of the cross section of the reflected light on the division means is approximately 0.1
Are divided into a fourth dividing line and a fifth dividing line, and the first dividing line is divided by the fifth dividing line.
And a tracking error signal generating means for generating a tracking error signal by alternately inverting the polarity of a signal obtained in response to the reflected light incident on one of the regions and adding the signals having the alternately inverted polarity. Optical head device. 38. A light source emitting a coherent beam or a quasi-monochromatic beam, and a light emitted from the light source condensed on an information storage medium having a track on which marks or spaces are selectively arranged or a track having a predetermined groove. A light collecting optical system, a light detector comprising a plurality of detection areas for receiving reflected light reflected by the information storage medium, and outputting a signal corresponding to the amount of the received reflected light; and an output from the light detector. Tracking error signal generating means for receiving a signal to be generated and generating a tracking error signal, and splitting means for splitting the light reflected by the information storage medium and enabling the split light to be received by the photodetector, Λ is the wavelength of light emitted from the light source, NA is the numerical aperture of the light-collecting optical system, and the distance from the center of a track to the center of an adjacent track in the information storage medium is Gp, λ / (NA · Gp) ≧ 1, and when the aperture of the light-collecting optical system is a circle having a radius of 1, an odd number of 3 or more is N, It has N dividing lines that are substantially parallel to the tangent, and two of the N dividing lines are arranged in a range of about 0.6 with respect to the center of the aperture of the condensing optical system, The other (N-2) dividing lines except the two dividing lines are arranged at equal intervals between the two dividing lines, and the tracking error signal generating means includes the center of the circle. Generating a tracking error signal using a signal obtained from a detection area that receives the reflected light incident on two areas outside the two non-divided lines; The polarity of the signal obtained from the detection area that receives the reflected light incident on the even number of areas sandwiched by the dividing lines is changed. Inverted, and generates a correction signal obtained by adding the signal inverted alternately polarity, the tracking error signal generating means, the optical head device for adding or subtracting the correction signal from the tracking error signal. 39. The optical head device according to claim 37, wherein the division unit is a diffraction unit. 40. The optical head device according to claim 37, wherein said dividing means is a dividing line of said photodetector. 41. A light source for emitting a coherent beam or a quasi-monochromatic beam, and a beam emitted from the light source condensed on an information storage medium having a track on which marks or spaces are selectively arranged or a track comprising a predetermined groove. A condensing optical system that receives the light reflected by the information storage medium and generates a diffracted light; receives the light diffracted by the diffractive means, and outputs a signal corresponding to the received light amount And a photodetector comprising a plurality of detection regions. The diffraction means has a plurality of divided regions, and diffracted light of a desired order generated from a region group A of a part of the plurality of regions is provided. Diffracted light of a desired order, which becomes a first spherical wave and is generated from a region group B composed of regions that are not included in the region group A of the plurality of regions, is transmitted from the converging point of the first spherical wave to the diffraction means. Far from A focus error signal for generating a focus error signal from a difference in the size of a cross section on the photodetector between the first spherical wave and the second spherical wave. Further comprising generating means, wherein the diffracting means comprises at least one beam perpendicular to a tangent of the track.
An optical head device having two division lines, wherein one of two regions which are in contact with each other across the division line belongs to the region group A and the other belongs to the region group B. 42. A beam emitted from the light source is condensed on an information storage medium having a light source for emitting a coherent beam or a quasi-monochromatic beam, and a track on which marks or spaces are selectively arranged or a track comprising a predetermined groove. A diffractive light diffracting the light reflected by the information storage medium to generate a diffracted light; receiving the light diffracted by the diffractive means and outputting a signal corresponding to the received light amount A photodetector comprising a plurality of detection regions, the diffraction means having a plurality of divided regions, and diffracted light of a desired order generated from a partial region group A of the plurality of regions, A diffracted light of a desired order generated from a region group B composed of regions that are not included in the region group A of the plurality of regions is converted from the converging point of the first spherical wave by the diffraction means. Focus at a far position A focus error signal generation for generating a focus error signal from a difference in the size of a cross section of the first spherical wave and the second spherical wave on the photodetector. The diffraction means has a diffraction area in a range wider than a range corresponding to the opening of the light-collecting optical system, and is provided in contact with an outer periphery of the opening and parallel to a tangent line of the track.
And two regions that are in contact with each other across the first division line or the second division line belong to the region group A, and the two regions The other is an optical head device belonging to the area group B. 43. The optical head device according to claim 39, wherein said diffracting means is integrated with said condensing optical system. 44. An emission step of emitting a coherent beam or a quasi-monochromatic beam, and focusing the beam emitted by the emission step on an information storage medium having a track in which at least one mark and at least one space are arranged. A light-condensing step of receiving light reflected by the information storage medium in a plurality of detection areas, and outputting a signal corresponding to the amount of the received reflected light; And a tracking error signal generating step of generating a tracking error signal based on the received signal, wherein the tracking error signal generating step includes a component of a signal obtained from the overlapping area from the tracking error signal. The overlapping region is formed when the opening of the condensing optical system is a circle having a radius of 1; Is a region where two circles each having a radius of 1 centered on two points separated by λ / (NA · Gp) from the center of the track in a direction perpendicular to the track, and the λ is emitted by the emission step. NA is the numerical aperture of the light-collecting optical system; Gp is the distance from the center of a track to the center of an adjacent track in the information storage medium; When the aperture of the system is a circle having a radius of 1, λ / (N
A · Gp) is a method having a relationship of λ / (NA · Gp) <1. 45. An emission step of emitting a coherent beam or a quasi-monochromatic beam, a splitting step of receiving a beam emitted in a laser beam generation step, and splitting the received beam into a first beam and a second beam. A step of receiving the first beam and the second beam and focusing the first beam and the second beam into a minute spot on an information storage medium; A branching step of receiving the diffracted beam and branching the received beam; a light detection step of receiving the beam branched by the branching step and outputting a signal corresponding to the amount of the received beam; and outputting in the light detection step A signal processing step of receiving the received signal and calculating the received signal; and a relative position between the condensing optical system and the information storage medium based on the signal calculated by the signal processing step. The first beam is different from the second beam in an effective numerical aperture when condensed by the condensing optical system. A method further comprising a tracking error signal generating step of generating a tracking error signal using a beam having a small effective numerical aperture when focused. 46. An emission step of emitting a coherent beam or a quasi-monochromatic beam, a convergence step of receiving the beam emitted in the emission step, and converging the received beam to a minute spot on an information storage medium; A branching step of receiving the beam reflected and diffracted by the storage medium and branching the received beam; and a light receiving the beams branched by the branching step by a plurality of light receiving units and outputting a signal corresponding to the amount of the received beam. A detection step; a signal processing step of receiving a signal output in the light detection step and calculating the received signal; and a focus and tracking control for performing relative positioning between the condensing optical system and the information storage medium. A first drive step of performing the following, and a second drive step capable of changing an angle formed between the beam focused by the focusing optical system and the information storage medium. The information storage medium has a pattern or a predetermined groove capable of generating a tracking error signal, and the pattern or the period of the predetermined groove capable of generating the tracking error signal is defined as Gp. Where λ is the wavelength of the beam emitted in the emission step and NA is the numerical aperture of the light-collecting optical system on the information storage medium side, NA> λ / Gp
In the relationship. 47. An emitting step of emitting a coherent beam or a quasi-monochromatic beam, and a focusing step of focusing a beam emitted from the light source on an information storage medium having a track on which marks or spaces are selectively arranged. A light detection step of receiving reflected light reflected by the information storage medium in a plurality of detection areas and outputting a signal corresponding to the amount of the received reflected light; and a dividing step of dividing light reflected by the information storage medium. A predetermined first area and a second area divided by the dividing step;
An information reproduction signal generating step of generating a reproduction signal for reproducing information recorded on the track from a differential signal of a signal obtained according to the reflected light incident on each of the two areas of the area, A method further including a changing step of changing a range included in the first area, the second area, or both areas according to a positional relationship between the light-collecting point condensed by the light-condensing step and the track. . 48. An emission step of emitting a coherent beam or a quasi-monochromatic beam, and a step of selectively emitting a beam emitted from the light source to an information storage medium having a track on which marks or spaces are arranged or a track having a predetermined groove. A light-collecting step of condensing light, reflected light reflected by the information storage medium is received by a detection region,
A light detection step of outputting a signal corresponding to the amount of the received reflected light; a tracking error signal generation step of receiving a signal output by the light detection step and generating a tracking error signal based on the received signal; A division step of dividing the light reflected by the information storage medium, wherein λ is a wavelength of light emitted in the emission step, NA is a numerical aperture of the light-collecting optical system, and a track in the information storage medium. Gp is the distance from the center of the next track to the center of the adjacent track, and has a relationship of λ / (NA · Gp) ≧ 1, and is incident on six regions divided by the fifth division line from the first division line A tracking error signal generating step of generating a tracking error signal by alternately inverting the polarity of a signal obtained in accordance with the reflected light and adding the signals of which the polarity is alternately inverted. And wherein the first to fifth division lines are substantially parallel to a tangent line of the track, and the first division line passes through the center of the cross section of the reflected light and connects to the track. The second division line and the third division line are located at a distance of about 0.1 across the first division line when the cross section of the reflected light is a circle having a radius of 1. A method in which the fourth division line and the fifth division line are located at a distance of about 0.1 from an end of the cross section of the reflected light when the cross section of the reflected light is a circle having a radius of 1. 49. An emitting step of emitting a coherent beam or a quasi-monochromatic beam, and a step of selectively emitting a beam emitted from the light source to an information storage medium having a track on which marks or spaces are arranged or a track having a predetermined groove. A light-condensing step of condensing light; a diffraction step of receiving reflected light reflected by the information storage medium in a plurality of divided regions to generate diffracted light; and receiving light diffracted by the diffraction means. A light detection step including a plurality of detection areas for outputting a signal corresponding to the amount of light, and a focus error signal generation for generating a focus error signal from a difference in cross-sectional size between the first spherical wave and the second spherical wave. The first spherical wave is diffracted light of a desired order generated from a partial area group A of the plurality of areas, and the second spherical wave is an area of the plurality of areas. group A is a diffracted light of a desired order generated from a region group B composed of regions not included in A, and the region group A has at least one beam perpendicular to a tangent to the track.
A method in which one of two regions which are in contact with each other across a book dividing line, and the region group B is the other of the two regions.