JP2007234120A - Optical pickup system and optical disk device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a means of detecting a tracking error signal while reducing the influence of eccentricity and the rotation deviation of a diffraction grating for a plurality of optical disks of different track pitches. <P>SOLUTION: In the optical pickup system comprising an objective lens for irradiating the optical disk with a luminous flux from the diffraction grating having three or more regions and a photodetector for detecting the luminous flux reflected from the optical disk, the diffraction grating branches the luminous flux into three luminous fluxes of first, second and third +1st light or -1st light or six luminous fluxes of the first, second and third ±1st light, converges the second diffracted light of the diffracted light at the position of the tracking direction distance l of the optical disk to the converging position of a main luminous flux, and converges the first and third diffracted light symmetrically to the diffracted light spot at the position of a distance "o" from the diffracted light spot. Also, the phase of the push-pull signals of the first and third sub luminous fluxes to the phase of the push-pull signals of the second sub luminous flux is shifted about 180 degrees. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an optical pickup device and an optical disc device.

  As background art in this technical field, for example, there is JP-A-2005-122869. In this publication, there is a description as “to improve the quality of the tracking error signal by reducing the influence of eccentricity etc. of the disk-shaped recording medium”, and as a means for solving the problem, “a plurality of types of disk-shaped with different use wavelengths” Recording or reproducing of an information signal with respect to the recording medium 100 is enabled, and laser beams having different wavelengths emitted from the light emitting element 9 are respectively divided into a main light beam, a pair of first sub light beams, and a pair of second sub light beams. A diffraction element 10 having a plurality of regions is provided, and the spot center of the first sub-beam is formed on the recording surface of any one type of disk-shaped recording medium and spaced apart in the substantially radial direction of the disk-shaped recording medium; The distance D is approximately (2n−1), where D is the distance from the spot center of the second sub-beam, n is a natural number, and P is the track pitch of any one type of disk-shaped recording medium. × was set to be P / 2 "and is described.

  Further, as background technology in this technical field, the Nikkei Electronics October 25, 2004 issue P.I. There are 47.

JP 2005-122869 A Nikkei Electronics, October 25, 2004, p. 47

  In general, an optical pickup device detects a spot correctly on a predetermined recording track in an optical disc, so that the objective lens is displaced in the focus direction by detecting the focus error signal, and adjustment is performed in the focus direction. Is detected, and the objective lens is displaced in the radial direction of the disk-shaped recording medium to perform tracking adjustment. The position of the objective lens is controlled by these signals.

  Among these, the push-pull method is known as a tracking error signal detection method, but there is a problem that a large direct current fluctuation (hereinafter referred to as a DC offset) is likely to occur due to the displacement of the objective lens in the tracking direction.

  Therefore, a differential push-pull method that can reduce the DC offset is widely used.

  In the differential push-pull method (DPP: Differential Push Pull method), a light beam is divided into a main light beam and a sub light beam by a diffraction grating, and a spot of a main light beam in a radial direction (hereinafter referred to as a main spot) and a spot of a sub light beam (hereinafter referred to as a main light beam) The DC offset is reduced by setting the interval between the sub-spots) to a half track pitch.

  In this method, since the three spots must be arranged with respect to the track, for example, when the disc is decentered or the diffraction grating is rotated, the amplitude of the DPP signal changes, and stable tracking control is performed. Becomes difficult.

  Therefore, in Patent Document 1, a diffractive element having a plurality of regions for dividing a laser beam emitted from a light emitting element into a main light beam, a pair of first sub-light beams, and a pair of second sub-light beams is provided, and disc-shaped recording is performed. The distance between the spot center of the first sub-bundle and the spot center of the second sub-beam formed on the recording surface of the medium so as to be separated from each other in the substantially radial direction of the disk-shaped recording medium is D, and n is a natural number. By setting the distance D to be approximately (2n-1) × P / 2 where P is the track pitch of the disk-shaped recording medium, the influence of disk eccentricity and diffraction grating rotation shift is reduced. ing.

  When this technique is used, the objective lens can obtain a tracking error even if it scans a position off the straight line extending in the radial direction through the center of the optical disk (hereinafter referred to as off-center). Therefore, as in Non-Patent Document 1, it is possible to realize an arrangement in which two objective lenses are arranged in the optical disk tangential direction.

  However, in the tracking method as in Patent Document 1, the amplitude of the tracking error signal changes due to disk eccentricity or rotational deviation for optical disks having different track pitches, and there is a problem that the performance of the tracking servo is lowered.

  In such a case, it is possible to cope with this by using a dedicated diffraction grating for each disk, but a plurality of diffraction gratings and an optical system for branching are required, which increases the number of parts and the resulting cost. A new problem of up occurs. One example is an optical recording / reproducing system using blue-violet laser light. There are Blu-ray Disc and HD DVD as optical recording / reproducing systems using blue-violet laser light, and it is known that the track pitch of the disc is different. In order to make these two recording / reproducing systems compatible with the tracking system as in Patent Document 1, it is necessary to mount two blue-violet lasers or to provide a special optical system such as a branch. As a result, an increase in cost is inevitable.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a new tracking system that reduces the influence of disk eccentricity and diffraction grating rotation deviation on a plurality of optical disks having different track pitches.

  In other words, the present invention aims to improve the performance of an optical pickup device and an optical disk device.

  The above object can be achieved by the invention described in the claims.

  According to the present invention, the performance of the optical pickup device and the optical disk device can be improved.

  Hereinafter, details of embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a diagram showing the positional relationship between an optical pickup device and an optical disc according to the first embodiment of the present invention, and the spot arrangement on the optical disc. (1) is a schematic layout diagram of an optical disk and an optical pickup device, and (2) is a layout of spots on the disk.

  First, (1) will be described. A normal optical disk apparatus has a function of rotating the optical disk about the spindle 10 as a central axis. Further, the optical pickup device has a function of driving on a straight line extending in the radial direction from the center of the spindle 10, and by moving to the inner and outer circumferences of the disc, it is possible to access all data in the optical disc. Yes.

  Next, (2) will be described. (2) is an enlarged view of the recording surface of the optical disk, and shows the arrangement of the light spots collected on the optical disk by the optical pickup. As shown in the figure, a track 101 is formed on a recordable optical disk such as a DVD-R. In order for the light spot to read and write information on the optical disk by moving the track as the optical disk rotates, the light spot needs to follow the track 101.

  In this embodiment, four spots of a main spot a and first, second and third diffracted light spots (hereinafter referred to as sub-spots b, c and d) are formed on the recording surface of the optical disc. The main spot a is used not only for recording and reproduction, but also for generating a tracking error signal and a focus error signal. The sub-spots b, c, and d are mainly used for generating a tracking error signal. The sub spot c is arranged at a distance l in the track direction of the optical disc with respect to the main spot on the optical disc. The sub spots b and d are arranged at a distance o from the sub spot c. Further, the tracking error signal of the sub-spot c with respect to the sub-spots b and d is approximately 180 degrees out of phase, and the light quantity ratio b: c: d is 1: 2: 1.

  By arranging the light spots in this way, it is possible to reduce the influence of the eccentricity of the disk and the rotational shift of the diffraction grating on a plurality of optical disks having different track pitches. This will be described below.

  The tracking error signal generation method of this embodiment will be described with reference to FIG. First, for the sake of simplicity, the eccentricity of the disk is not considered. FIG. 2 shows the positions of the main spot a, sub-spots b, c, and d on the optical disc and the push-pull signal detected from each spot. Assume that the time of spot arrangement on the figure is t = 0, and that the light spot moves in the radial direction of the optical disk (right in the figure) as time advances.

  When the main spot a moves in the radial direction of the optical disc from the position in the figure, a push-pull signal a as shown in the lower part of FIG. 2 can be detected along the track of the optical disc. Further, push-pull signals b and d can be detected from the sub-spots b and d. Further, from the sub-spot c, a push-pull signal c whose amplitude is approximately twice that of the push-pull signals b and d and whose phase is inverted by approximately 180 degrees can be detected.

Here, when the push-pull signal amplitude obtained from the main spot is represented as A1, and the push-pull signal amplitude obtained from the sub-spot is represented as A2, the push-pull signal obtained from each spot can be represented by the following equation. In the following, for simplicity, the push-pull signal obtained when crossing a track is represented by a sine wave.
Push-pull signal a

Push-pull signal c

Push-pull signal b, d

  T in the equation is the time for passing between tracks, and the same push-pull signal can be detected again after time T.

  Here, when the push-pull signal a is MPP and the signal obtained by adding all the push-pull signals b, c, and d is the SPP signal, the tracking error signal (TES) is obtained by the following calculation.

  Note that k in the equation is a coefficient for correcting the light amount difference between the main spot and the sub spot. It is clear that adding all of the push-pull signals b, c, d results in 0, and the TES and MPP signals become equal by performing the calculation of [Equation 4]. The present embodiment is characterized in that the SPP signal amplitude is substantially zero even when the disk is eccentric. Since this calculation is the same as the DPP signal calculation, it is advantageous that the offset at the time of shifting the objective lens can be canceled.

  The DPP method has an advantage that the offset at the time of shifting the objective lens can be canceled, but the three spots must be arranged with respect to the track. For this reason, in addition to the eccentricity of the disk and the rotational displacement of the diffraction grating, the objective lens is used for scanning a position off the straight line extending in the radial direction through the center of the optical disk (hereinafter referred to as off-center). I can't. When off-center, the positional relationship of the three spots with respect to the track changes at the inner, middle, and outer positions, so that the DPP signal amplitude changes at the inner, middle, and outer positions. For this reason, stable control cannot be performed. This is a phenomenon caused by fluctuations in the SPP signal amplitude. This will be described using equations.

FIG. 3 shows that the track tilts with respect to the three spot arrangements of the DPP method on the basis of the track. When the angle θ is inclined with respect to the three-spot arrangement of the DPP method, it is assumed that the two sub-spots move in the radial direction by a distance m as shown in the figure. Assuming that the main spot is on the track at time t = 0, each push-pull signal of the three spots can be expressed by the following equation with respect to time t.
Push-pull signal h

Push-pull signal i

Push-pull signal j

Here, 2πm / Tp is set to M for simplicity. Further, the DPP signal when off-centered from this equation can be expressed by the following equation.
DPP signal

  In the case of off-center, the distance m changes depending on the inner circumference, middle circumference, and outer circumference position. As a result, the DPP signal amplitude changes at the inner, middle, and outer peripheral positions, and stable control cannot be performed.

  In this embodiment, it is possible to detect a stable tracking error signal by reducing the amount of change in the amplitude of the SPP signal at the inner, middle, and outer positions when off-center. A method for reducing the amount of change in the SPP signal amplitude and the TES amplitude at the inner and outer peripheral positions when the objective lens is off-center will be described below.

For example, when at least one objective lens is arranged to be off-center as shown in FIG. 4 (1), the spot on the disc on the off-center objective lens side is inclined by an angle θ with respect to the track. 4 (2). Here, if the distance between the main spot and the second sub-spot is l, the distance between the first and second sub-spots, and the second and third sub-spots are o, the push-pull signal at each spot is expressed by the following equation: It can be expressed as
Push-pull signal a

Push-pull signal c

Push-pull signal b

Push-pull signal d

Here, 2πl · sin θ / Tp and 2πo · sin θ / Tp are respectively set to L and O for simplicity. When the SPP signal and TES are calculated from these equations, they can be expressed by the following equations.
SPP signal

TES

When moving from the inner periphery to the outer periphery in an off-centered state, L in the equation changes as in the DPP method. However, by setting the sub-spot interval o to about the track interval, the SPP signal amplitude approaches 0 and only the offset component accompanying the objective lens shift is detected. By subtracting this offset component from the MPP signal, a good TES signal can be obtained. As described above, the tracking error signal detection method of this embodiment can always obtain a substantially constant TES signal regardless of whether it is off-center. Note that the first, second, and third ± first-order diffracted light may be arranged at the spot on the disk as shown in FIG. At this time, the SPP signal is calculated as shown in FIG.
SPP signal

For example, the main spots a and the first, second, and third ± first-order diffracted light sub-spots b, c, d, e, f, and g are arranged on the Blu-ray Disk disk under the following conditions. If
・ Off center 5mm
O = 0.32 μm (= Tp), L = 5 μm
-The slope of the straight line connecting the first, second, and third sub-spots on the disc is set to the slope intermediate value of the inner and outer track positions.

A graph comparing the present method and the DPP method under the above conditions is shown in FIG. In this method, the fluctuation amount of the TES signal amplitude at the inner, middle, and outer peripheral positions is suppressed to a change of about ± 2% with respect to the MPP signal amplitude. (In the DPP method, the DPP signal amplitude changes by ± 100% with respect to the MPP signal amplitude.)
Here, assuming that the fluctuation amount of the TES signal amplitude is ± 20% on the optical reproducing apparatus or the optical recording / reproducing apparatus side, a straight line connecting the first, second, and third sub-spots on the optical disc and the track The inclination θ of

It is clear that this should be satisfied. That is, if the first, second, and third sub-spot arrangements are determined, the limit value of the off-center amount is given. In FIG. 5, the main spot and all the sub-spots are arranged in a straight line. However, as long as [Equation 16] is satisfied, they may be arranged as shown in FIGS. 7 (1) and (2).
In principle, in the DPP method, it was necessary to form three beams with a diffraction grating in the optical pickup and control the diffraction grating with high precision. However, as in this embodiment, a tracking error signal that hardly depends on the rotation angle. With this detection method, it is not necessary to adjust the rotation of the diffraction grating of the diffraction grating, and an effect that a simple assembly process can be realized also in the optical pickup can be obtained.

  In Patent Document 1, a diffraction element having a plurality of regions for dividing a laser beam emitted from a light emitting element into a main light beam, a pair of first sub-light beams, and a pair of second sub-light beams is provided, and a disc-shaped recording medium The distance between the spot center of the first sub-bundle and the spot center of the second sub-beam formed on the recording surface of the disc-shaped recording medium so as to be separated from each other in the substantially radial direction is D, and n is a natural number, By setting the distance D to be approximately (2n−1) × P / 2, where P is the track pitch of the disk-shaped recording medium, a stable tracking error signal can be detected even when off-center. . However, as described above, since the spot arrangement on the disc differs depending on the track pitch as described above, for example, the Blu-ray Disc and HD DVD diffraction gratings having the same light source wavelength and different track pitch are shared. This is difficult, and it is inevitable that the cost will be increased, including the laser branching method.

  In this embodiment, a stable tracking error signal can be detected even when the same diffraction grating is used for Blu-ray Disc and HD DVD. This will be described below.

  In Patent Document 1, since the tracking method uses the track interval effectively, it is not possible to deal with disks having different track pitches. In this embodiment, in order to obtain a stable tracking error signal by reducing the sub-spot interval o to about the track pitch, for example, if the tracking error signal is designed to be stable with a Blu-ray Disc, the track is more than that. A stable tracking error signal can be obtained even for HD DVD having a large pitch. This is easily considered from the result shown in FIG. As a result, it becomes possible to use a common optical path for Blu-ray Disc and HD DVD, thereby reducing costs.

  In the second embodiment, a case where the light amount ratio of the first, second, and third diffracted light is different from that of the first embodiment will be described with reference to FIG.

When the push-pull signal amplitude ratio of the first, second, and third diffracted lights in FIG. 8A is A3: A2: A3, the push-pull signal obtained from each spot can be expressed by the following equation.
Push-pull signal a

Push-pull signal c

Push-pull signal b

Push-pull signal d

  Here, 2πl · sin θ / Tp and 2πo · sin θ / Tp are respectively set to L and O for simplicity. FIG. 8 (2) shows the calculation of push-pull signals obtained from each spot. When the signal obtained by electrically amplifying the push-pull signal c with a predetermined amplification factor k1 (2 · A3 / A2), the push-pull signal b, and the push-pull signal d are all added to the SPP signal, the SPP signal and the TES are executed. It is clear that the result is similar to Example 1. Further, as shown in FIG. 8 (3), the push-pull signal b and the push-pull signal d may be added and then amplified and added to the push-pull signal c. As in the first embodiment, first, second, and third ± first-order diffracted light may be arranged on the disk.

  In the third embodiment, an optical pickup for generating tracking error signals according to the first and second embodiments will be described. As an example, an optical pickup compatible with DVD-R recording and reproduction will be described. Of course, the present embodiment is not limited to the DVD-R, and can be applied to all recordable optical disks having tracks.

  FIG. 9 shows a schematic configuration of the optical pickup device. A one-dot chain line in the figure indicates an optical path of the light beam. Usually, a semiconductor laser having a wavelength of 660 nm band is used for recording or reproduction of an optical disk of DVD. The light beam emitted from the semiconductor laser 50 enters the diffraction grating 51. The diffraction grating 51 splits the light beam into four or seven. The branched light beam reflects from the beam splitter 52 and is converted into parallel light by the collimator lens 53. These light beams are reflected by the rising mirror 55, pass through the ¼λ plate, and then condensed on the disk by the objective lens 57. Four or seven light spots are formed on the disk, and the reflected light of each spot passes through the objective lens 57, 1 / 4λ plate, collimator lens 53, beam splitter 52, and detection lens 58 and becomes a photodetector. Incident. Astigmatism is given to the light beam by the detection lens, and a focus error signal can be detected. It is possible to control the position of the light spot using a focus error signal and a tracking error signal obtained from a light beam incident on the photodetector.

  In the fourth embodiment, another optical system configuration of the optical pickup device using this embodiment will be described. Here, a compatible pickup for Blu-ray disc and HD DVD will be described.

  FIG. 10 is a diagram showing a schematic configuration of the optical pickup device. A 405 nm band semiconductor laser is used for recording or reproduction of Blu-ray disc and HD DVD. The one-dot chain line in the figure is the optical path of the light beam for Blu-ray disc, and the two-dot chain line is the optical path of the light beam for HD DVD. The one-dot chain line and the two-dot chain line are separated but are actually the same optical path. The beam expander in the figure is used not only to change the optical system magnification but also to correct spherical aberration due to the thickness of the cover layer by changing the divergence and convergence state of the light beam.

  First, a Blu-ray disc optical system will be described. The light beam emitted from the semiconductor laser 60 enters the diffraction grating 61 and is branched into four or seven light beams. The branched light beam reflects from the beam splitter 62, is converted into parallel light by the collimator lens 63, and enters the beam expander 65. The light beam that has passed through the beam expander 65 is reflected by the rising mirror 67, passes through the ¼λ plate, and is then condensed on the disk by the objective lens 68. Four or seven light spots are formed on the disc, and the reflected light from each spot passes through the objective lens 67, 1 / 4λ plate, beam expander 65, collimating lens 63, beam splitter 62, and detection lens 72. The light passes through and enters the photodetector 73. Astigmatism is given to the light beam by the detection lens 72, and a focus error signal can be detected. The position of the light spot can be controlled using a focus error signal and a tracking error signal obtained from the light beam incident on the photodetector 72.

  Next, the HD DVD optical system will be described. Similarly to the Blu-ray disc optical system, the light is branched into four or seven by the diffraction grating 61, reflected by the beam splitter 52, and converted into parallel light by the collimator lens 63. This light beam passes through the beam expander 65, is reflected by the rising mirror 69, passes through the ¼λ plate, and is then condensed on the disk by the objective lens 71. Four or seven light spots are formed on the disc, and reflected light from each spot is converted into objective lens 71, 1 / 4λ plate, beam expander 65, collimator lens 63, beam splitter 62, detection lens 72, And is incident on the photodetector 73. Astigmatism is given to the light beam by the detection lens 72, and the position of the light spot can be controlled using the focus error signal and the tracking error signal.

As described above, a compatible pickup of Blu-ray disc and HD DVD can be manufactured, and the number of parts can be reduced as much as possible. Thereby, the effect of leading to cost reduction can be obtained.
Needless to say, for example, a CD / DVD optical system may be formed in this optical system.

  In the fifth embodiment, still another optical system configuration of the optical pickup device using this embodiment will be described.

  FIG. 11 is a diagram showing a schematic configuration of the optical pickup device. A semiconductor laser 80 in the drawing is an element capable of emitting laser light for Blu-ray disc, HD DVD, DVD, and CD. Similar to the sixth embodiment, it is possible to realize compatibility of Blu-ray disc and HD DVD. Needless to say, compatibility with DVDs and CDs is also possible by using a beam expander.

  As described above, a compatible pickup for Blu-ray disc, HD DVD, DVD, and CD can be manufactured, and the number of parts can be reduced without limit. Thereby, the effect of leading to cost reduction can be obtained.

  In the sixth embodiment, a detailed description will be given of the diffraction gratings mounted in the first to fifth embodiments that branch the light beam emitted from the laser. 12A and 12B are diagrams showing a schematic configuration of the diffraction grating. As shown in this figure, the irradiation surface of the light beam incident on the diffraction grating is divided into three regions in a strip shape in a predetermined direction. With such a configuration, the main light beam can be branched into first, second, and third diffracted lights. Further, the distance between spots of diffracted light on the disk can be changed by changing the grating pitch of the three regions.

  In FIG. 12A, a region where the phase of the push-pull signal is added 180 degrees is formed in the central region of the region divided into three. This region has a configuration in which the relative positions of the lattice grooves are different by 180 degrees at the approximate center in the radial direction. Therefore, the portion where the 0th order light and the + 1st order light diffracted by the track on the disk interfere with each other is 180 degrees. Similarly, the interference part of the 0th-order light and the −1st-order light is 180 degrees different from each other, and as a result, the push-pull signal differs from the other two areas by 180 degrees. In this way, the light beam for detecting the tracking error signal of this embodiment can be branched. Note that, as shown in FIG. 11B, regions where the phase of the push-pull signal is added by 180 degrees may be formed in the regions at both ends of the region divided into three.

  In the seventh embodiment, an optical reproducing apparatus equipped with the optical pickup device 170 will be described. FIG. 13 shows a schematic configuration of the optical reproducing apparatus. The optical pickup device 170 is provided with a mechanism that can be driven along the radial direction of the optical disc 100, and is position-controlled in accordance with an access control signal from the access control circuit 172.

  A predetermined laser driving current is supplied from the laser lighting circuit 177 to the semiconductor laser in the optical pickup device 170, and laser light is emitted from the semiconductor laser with a predetermined light amount according to reproduction. The laser lighting circuit 177 can be incorporated in the optical pickup device 170.

  The signal output from the photodetector in the optical pickup device 70 is sent to the servo signal generation circuit 174 and the information signal reproduction circuit 175. The servo signal generation circuit 174 generates a servo signal such as a focus error signal, a tracking error signal, and a tilt control signal based on the signal from the photodetector. Based on the servo signal generation circuit 174, the actuator drive circuit 173 passes through the servo signal generation circuit 174. The position of the objective lens is controlled by driving the actuator.

  In the information signal reproducing device 175, the information signal recorded on the optical disc 100 is reproduced based on the signal from the photodetector.

  Some of the signals obtained by the servo signal generation circuit 174 and the information signal reproduction circuit 175 are sent to the control circuit 176. The control circuit 176 is connected to a spindle motor drive circuit 171, an access control circuit 172, a servo signal generation circuit 174, a laser lighting circuit 77, and the like, and controls the rotation of the spindle motor 160 that rotates the optical disc 100, the access direction and the access position. Control, servo control of the objective lens, control of the amount of light emitted from the semiconductor laser in the optical pickup device 70, and the like are performed.

In the eighth embodiment, an optical recording / reproducing apparatus equipped with an optical pickup 170 will be described. FIG. 14 is a schematic configuration of an optical recording / reproducing apparatus. This apparatus is different from the optical information recording / reproducing apparatus shown in FIG. 12 in that an information signal recording circuit 178 is provided between the control circuit 176 and the laser lighting circuit 177, and a recording control signal from the information signal recording circuit 78 is provided. Based on the above, the lighting control of the laser lighting circuit 177 is performed, and a function of writing desired information to the optical disc 100 is added.

  By adopting the configuration as described above, for example, a plurality of optical discs having the same wavelength and different track pitches as light sources such as Blu-ray Disc and HD DVD are affected by disc eccentricity and diffraction grating rotation deviation. It becomes possible to reduce. Even when the objective lens is off-center, a good tracking error signal can be obtained.

FIG. 3 is a diagram illustrating an optical pickup, an optical disc, and a light spot arrangement on the optical disc in Embodiment 1. It is a figure explaining the tracking error signal of Example 1. FIG. It is a figure explaining the tracking error signal of Example 1. FIG. It is a figure explaining the tracking error signal of Example 1. FIG. It is a figure explaining the tracking error signal of Example 1. FIG. It is a figure explaining the tracking error signal of Example 1. FIG. It is a figure explaining the tracking error signal of Example 1. FIG. It is a figure explaining the tracking error signal of Example 2. FIG. 6 is a diagram illustrating an optical pickup in Embodiment 3. FIG. FIG. 10 is a diagram illustrating an optical pickup according to a fourth embodiment. FIG. 10 is a diagram illustrating an optical pickup according to a fifth embodiment. It is a figure explaining the branch grating | lattice in Example 6. FIG. FIG. 10 is a diagram illustrating an optical reproducing device according to a seventh embodiment. FIG. 10 is a diagram for explaining an optical recording / reproducing apparatus in Example 8.

Explanation of symbols

1: optical pickup device, 2: objective lens, 3: objective lens, 10: spindle, 50: semiconductor laser, 51: diffraction grating, 52: beam splitter, 53: collimating lens, 54: front monitor, 55: rising mirror 57: objective lens, 58: detection lens, 59: photodetector, 60: semiconductor laser, 61: diffraction grating, 62: beam splitter, 63: collimating lens, 64: front monitor, 65: beam expander, 66: Rise mirror, 68: objective lens, 69: rise mirror, 71: objective lens, 72: detection lens, 73: photodetector, 80: semiconductor laser, 81: diffraction grating, 82: beam splitter, 83: collimating lens 84: Front monitor, 85: Beam expander, 86: Raising mirror, 88: Objective 89: Raising mirror, 91: Objective lens, 92: Detection lens, 93: Optical detector, 100: Optical disc, 101: Track, 170: Optical pickup device, 171: Spindle motor, 172: Access control, 173: Actuator drive circuit, 174: Servo signal generation circuit, 175: Information signal reproduction circuit, 176: Control circuit, 177: Laser lighting circuit, 178: Information recording circuit, a: Main light spot of this embodiment, b: This embodiment First + 1st order or -first order diffracted light spot, c: second + 1st order or -1st order diffracted light spot of this embodiment, d: third + 1st order or -1st order of this embodiment Diffracted light spot, e: first −1st order or + 1st order diffracted light spot of this embodiment, f: second −1st order or + 1st order diffracted light spot of this embodiment, g Third -1-order or +1 order diffracted light spot of the present embodiment, h: main light spot h DPP-type, i: sub-light spot i of the DPP type, j: sub-light spot j DPP-type

Claims (12)

A semiconductor laser;
A diffraction grating having three regions through which a main light beam emitted from the semiconductor laser is transmitted;
An objective lens for condensing the main luminous flux on an optical disc;
A photodetector for detecting a main luminous flux and diffracted light reflected from the optical disc;
With
The diffraction grating branches the main light beam into three light beams of first, second, and third + 1st order light, or the diffraction grating splits the main light beam into first, second, and third −1st order light beams. Branches into three luminous fluxes of light,
Optical pickup device. A semiconductor laser;
A diffraction grating having three regions through which a main light beam emitted from the semiconductor laser is transmitted;
An objective lens for condensing the main luminous flux on an optical disc;
A photodetector for detecting a main luminous flux and diffracted light reflected from the optical disc;
With
The diffraction grating branches the main light beam into six light beams of first, second, and third ± first-order light,
Optical pickup device. The optical pickup device according to claim 1, wherein
The diffraction grating has a first region, a second region, and a third region, and the first diffracted light, the second diffracted light, and the third diffracted light are branched from each region,
The phase of the push-pull signal detected from the first and third diffracted lights is approximately 180 degrees different from the phase of the push-pull signal detected from the second diffracted light.
Optical pickup device. The optical pickup device according to claim 3,
The second diffracted light is condensed at a position in the track direction distance l with respect to the condensing position of the main light beam on the optical disc, and the second diffracted light is collected at a distance o from the condensing position of the second diffracted light. Condensing the first diffracted light and the third diffracted light;
Optical pickup device. The optical pickup device according to claim 4,
When the track interval on the optical disk is Tp and the coefficient for correcting the light quantity ratio between the main light flux and the three diffracted lights is k, the first, second and third diffracted lights are condensed on the optical disk. The slope θ between the straight line connecting the position and the track satisfies the following formula (| k (1-cos (2πo · sin θ / Tp)) · cos (2πl · sin θ / Tp) | <0.20).
Optical pickup device The optical pickup device according to any one of claims 3 to 5,
The photodetector has a detector for detecting the reflected light of the main light beam from the optical disk and at least one detection region for receiving the reflected light of the first, second and third diffracted lights from the optical disk. Each detection area includes at least two light receiving surfaces divided along a predetermined direction corresponding to the radial direction of the disk, and a difference between signals detected independently from the light receiving surface for each detection area. Detect tracking error signal by push-pull method from
Optical pickup device. The optical pickup device according to any one of claims 3 to 6,
The light quantity ratio of the first, second, and third diffracted lights branched from the diffraction grating is 1: 2: 1, and the first, second, and third diffracted lights detected from the detector are pushed. After all the pull signals are added, the signal is amplified with a predetermined amplification factor k, and the tracking error signal is detected by subtracting from the push-pull signal of the main luminous flux.
Optical pickup device. The optical pickup device according to any one of claims 3 to 7,
Two or more recording / reproducing systems having different track intervals of an optical disk by one single wavelength semiconductor laser and the diffraction grating are mounted with two or more diffraction gratings according to the smallest track interval. Corresponding to the recording and playback method tracking of
Optical pickup device. The optical pickup device according to any one of claims 3 to 7,
By mounting the diffraction grating in accordance with the smallest track interval on the two or more recording / reproducing systems in which the track interval of the optical disk is different by the semiconductor laser capable of oscillating a plurality of wavelengths and the diffraction grating. Supports tracking of two or more recording and playback methods,
Optical pickup device. An optical pickup device according to any one of claims 3 to 9,
A laser lighting circuit for driving the semiconductor laser in the optical pickup device;
A servo signal generation circuit that generates a focus error signal and a tracking error signal using a signal detected from the photodetector in the optical pickup device;
An information signal reproducing circuit for reproducing an information signal recorded on the optical disc;
Equipped with,
Optical disk device. A diffraction grating that splits a light beam into a plurality of beams,
The diffraction grating divides the irradiation surface of the light beam incident on the diffraction grating into three regions in a strip shape in the track direction of the optical disc, and each of the three regions is formed with grating grooves having different intervals, Two regions are formed in the central region of the three regions in a direction perpendicular to the rotation of the optical disc, and the two regions have a phase difference of 180 degrees in each region on the boundary line.
Diffraction grating. A diffraction grating that splits a light beam into a plurality of beams,
The diffraction grating divides the irradiation surface of the light beam incident on the diffraction grating into three regions in a strip shape in the track direction of the optical disc, and each of the three regions is formed with grating grooves having different intervals, Of the three areas, two areas are formed in the radial direction of the optical disk at both end areas, and the two areas divided in the radial direction of the optical disk have a phase of 180 degrees in the lattice groove of each area on the boundary line. Different,
Diffraction grating.

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