JP2004272947A - Optical pickup head device and optical information device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce fluctuation in TE signal amplitude and symmetry when using an optical storage medium having a plurality of information recording surfaces. <P>SOLUTION: An optical storage medium is irradiated with three beams, and a light is received by a photodetecting means. The photodetecting means has a plurality of photodetectors, a signal outputted from each photodetector is subjected to differential calculation, and a tracking error signal is generated by a push-pull method. When a direction in which the three beams are arrayed on the photodetecting means is made an X direction, and a direction orthogonal to the X direction is made a Y direction, the three beams on the photodetecting means are made smaller in size in the X direction than in the Y direction. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an optical pickup head device for recording, reproducing, or erasing information on an optical storage medium for recording information with marks and spaces, and an optical information device.
[0002]
[Prior art]
As a high-density and large-capacity storage medium, a high-density and large-capacity optical disk called a DVD has recently been put to practical use, and is widely used as an information medium capable of handling a large amount of information such as a moving image.
[0003]
FIG. 14 is a diagram showing a configuration of a general optical system used in an optical pickup in an optical disc system as an optical information device capable of recording and reproducing. In the conventional configuration, an optical storage medium is irradiated with three beams to detect a tracking error signal (for example, see Patent Document 1).
[0004]
The light source 1 such as a semiconductor laser emits a linearly polarized divergent beam 70 having a wavelength λ of 405 nm. The divergent beam 70 emitted from the light source 1 is converted into parallel light by the collimating lens 53 having a focal length f1 of 15 mm, and then enters the diffraction grating 58. The beam 70 incident on the diffraction grating 58 is split into three beams of 0-order and ± 1st-order diffracted light. The 0th-order diffracted light becomes a main beam 70a for recording / reproducing information, and the ± 1st-order diffracted light becomes two sub-beams 70b and 70c for a differential push-pull (hereinafter referred to as DPP) method for detecting a TE signal. The ratio of the diffraction efficiency of the zero-order diffracted light 70a of the diffraction grating 58 to the diffraction efficiency of one first-order diffracted light 70b or 70c is usually set to 10: 1 to 20: 1 in order to avoid unnecessary recording by the sub-beam. Here, it is 20: 1. The three beams 70a to 70c generated by the diffraction grating 58 pass through the polarizing beam splitter 52, pass through the quarter-wave plate 54, are converted into circularly polarized light, and then have an objective lens with a focal length f2 of 2 mm. The light is converted into a convergent beam at 56, passes through the transparent substrate 41a of the optical storage medium 41, and is focused on the information recording surface 41c. The optical storage medium 41 has two information recording surfaces 41b and 41c. Here, a state where the beam 70 condensed by the objective lens 56 is focused on the information recording surface 41c is shown. I have. The optical storage medium 41 is composed of a transparent substrate 41a and information recording surfaces 41b and 41c. The distance d2 from the light incident surface of the optical storage medium 41 to the information recording surface 41c is 100 μm, and the distance d1 between the information recording surfaces 41b and 41c. Is 25 μm. Although not shown here, the period tp of the track formed on the information recording surfaces 41b and 41c is 0.32 μm. The aperture of the objective lens 56 is limited by the aperture 55, and the numerical aperture NA is 0.85. The thickness of the transparent substrate 41a is 0.1 mm, and the refractive index n is 1.62. The equivalent reflectance of the information recording surfaces 41b and 41c is about 4 to 8%, respectively. Here, assuming that the amount of light of the beam incident on the optical storage medium 41 is 1, the equivalent reflectivity of the beam when the light exits the optical storage medium 41 again after being reflected by the information recording surface 41b or 41c is described. The light amount is shown. The information recording surface 41c absorbs or reflects most of the light amount of the incident beam, but the information recording surface 41b transmits about 50% of the light amount of the incident beam to make the beam reach the information recording surface 41c. Then, the remaining 50% of the light amount is absorbed or reflected.
[0005]
FIG. 15 shows the relationship between the beam and the track on the information recording surface 41c. On the information recording surfaces 41b and 41c of the optical storage medium 41, continuous grooves serving as tracks are formed, and Tn-1, Tn, and Tn + 1 are tracks, respectively. Information is recorded on the groove. The track pitch tp is 0.32 μm. When the main beam 70a is positioned above the track Tn, the beams are arranged such that the sub beam 70b is positioned between the tracks Tn-1 and Tn, and the sub beam 70c is positioned between the tracks Tn and Tn + 1. That is, the interval L between the main beam and the sub beam in the direction orthogonal to the track is 0.16 μm.
[0006]
The beam 70 reflected by the information recording surface 41 c passes through the objective lens 56, the quarter-wave plate 54, is converted into linearly polarized light that differs from the outward path by 90 degrees, and is reflected by the polarization beam splitter 52. The beam 70 reflected by the polarization beam splitter 52 passes through a condenser lens 59 having a focal length f3 of 30 mm, is converted into convergent light, and enters the photodetector 30 via a cylindrical lens 57. When the beam 70 passes through the cylindrical lens 57, astigmatism is imparted.
[0007]
FIG. 16 schematically shows the relationship between the photodetector and the beam. The photodetector 30 has eight light receiving sections 30a to 30h. The light receiving sections 30a to 30d receive the beam 70a, the light receiving sections 30e to 30f receive the beam 70b, and the light receiving sections 30g to 30h receive the beam 70c. The light receiving units 30a to 30h output current signals I30a to I30h corresponding to the amounts of received light, respectively. A focus error (hereinafter referred to as FE) signal is obtained by the astigmatism method using the signals I30a to I30d output from the photodetector 30, that is, by the calculation of (I30a + I30c)-(I30b + I30d). Further, the TE signal is obtained by the DPP method, that is, by the calculation of {(I30a + I30d)-(I30b + I30c)}-C. {(I30e + I30g)-(I30f + I30h)}. Here, C is a coefficient determined by the ratio of the diffraction efficiencies of the zero-order diffracted light of the diffraction grating 58 and one first-order diffracted light. After the FE signal and the TE signal are amplified and phase-compensated to desired levels, the signals are supplied to actuators 91 and 92 for moving the objective lens 56 to perform focus and tracking control. The information (hereinafter referred to as RF) signal recorded on the information recording surface 41c is obtained by the calculation of I30a + I30b + I30c + I30d.
[0008]
However, when an optical storage medium having a plurality of information recording surfaces is used, the beam is reflected on an information recording surface other than the desired information recording surface, and then enters the photodetector. The beams 71a to 71c are beams that enter the photodetector 30 when the beam 70 is reflected by the information recording surface 41b. At this time, when the beam 71a and the beam 70b or the beam 71a and the beam 70c overlap, a light and dark distribution due to interference occurs. The distribution of light and darkness due to this interference fluctuates due to fluctuations in the surface of the optical storage medium or partial thickness unevenness of the transparent substrate 41a, and affects the TE signal. Beams 70b and 70c are sub-beams, while beam 71a is the main beam. Since the sub-beams 70b and 70c have smaller light amounts than the main beam 70a, the change in brightness between the beams 71a and 70b and between the beams 71a and 70c due to interference is the largest.
[0009]
[Patent Document 1]
JP-A-3-005927 (pages 5-8, FIG. 2)
[0010]
[Problems to be solved by the invention]
FIG. 17 is a diagram showing a state when a TE signal by the DPP method obtained when the beams 70a to 70c are scanned in a direction orthogonal to the track is observed by an oscilloscope. When the TE signal is detected in the above-described conventional configuration, the amplitude and the symmetry of the TE signal fluctuate greatly. If the tracking control is performed using the TE signal, the tracking control becomes unstable, and there has been a problem that information cannot be recorded and reproduced with high reliability.
[0011]
The present invention provides an optical pickup head device and an optical information device capable of reducing the fluctuation of the TE signal amplitude and recording or reproducing information with high reliability in consideration of such problems of the conventional optical information device. The purpose is to:
[0012]
[Means for Solving the Problems]
An optical pickup head device according to the present invention includes a light source that emits a light beam, a diffractive unit that receives a beam emitted from the light source and generates a plurality of diffracted beams of 0-order and first-order and higher, and the diffractive unit. Focusing means for receiving a plurality of beams from the optical storage medium and collecting the beams on the optical storage medium; beam splitting means for receiving the plurality of beams reflected by the optical storage medium and splitting the beam; and splitting by the beam splitting means Light detecting means for receiving a plurality of beams obtained and outputting a signal corresponding to the received light amount, wherein the 0th-order diffracted light generated by the diffracting means is used as a main beam, and The two or more diffracted lights of the next order or more are defined as a first sub-beam and a second sub-beam, and the light detecting means has a plurality of light receiving sections, and the plurality of beams are substantially one virtual light on the light detecting means. Straight line When the direction of the virtual straight line is defined as a first direction and a direction orthogonal to the first direction is defined as a second direction on a surface of the light detecting unit that receives the beam, The size of the beam in the first direction is smaller than the size in the second direction, thereby achieving the above object.
[0013]
In the above-described optical pickup head device, preferably, the plurality of beams are substantially focused in a first direction on a surface of the light detection unit that receives the plurality of beams.
[0014]
Further, the main beam, the first sub-beam, and the second sub-beam are respectively received by a plurality of light-receiving units, and the plurality of light-receiving units that receive the main beam are defined as a first light-receiving unit group. A plurality of light receiving units for receiving light is a second light receiving unit group, a plurality of light receiving units for receiving the second sub-beam is a third light receiving unit group, and a size of the first light receiving unit group in a first direction is set. The height may be smaller than the size in the second direction.
[0015]
The size of the second light receiving unit group in the first direction is smaller than the size of the second light receiving unit group in the first direction, and the size of the third light receiving unit group in the first direction is larger than the size in the second direction. It may be characterized by being smaller than the above.
[0016]
Further, a light receiving unit may be provided in addition to the first to third light receiving unit groups.
[0017]
Further, a light receiving unit may be provided between the first light receiving unit group and the second light receiving unit group and between the first light receiving unit group and the third light receiving unit group.
[0018]
Further, the second light-receiving unit group or the third light-receiving unit group may include three or more light-receiving units.
[0019]
Further, the second light receiving unit group or the third light receiving unit group may include six light receiving units.
[0020]
Another optical pickup head device according to the present invention includes: a light source that emits a light beam; a diffraction unit that receives a beam emitted from the light source and generates a plurality of diffracted beams including zero-order and first-order and higher; Condensing means for receiving a plurality of beams from the diffracting means and condensing the beams on an optical storage medium; receiving a plurality of beams reflected on the optical storage medium to form a first beam group and a second beam group Beam splitting means, and light detecting means for receiving the first beam group and the second beam group and outputting a signal corresponding to the received light amount. The next-order diffracted light is used as a main beam, the two or more first-order diffracted lights generated by the diffracting means are used as a first sub-beam and a second sub-beam, and the light detecting means has a plurality of light-receiving sections, The main beam forming the beam group The beam, the first sub-beam, and the second sub-beam are arranged on substantially one virtual straight line on the light detecting means, and the direction of the virtual straight line is changed on a surface of the light detecting means which receives the beam. When the first direction is set, and the direction orthogonal to the first direction is set as the second direction, the size of the plurality of beams in the first direction is smaller than the size in the second direction. The above object is achieved.
[0021]
Preferably, in the above optical information device, the light amount of the second beam group is larger than the light amount of the first beam group.
[0022]
An optical information device according to the present invention includes a light source that emits a light beam, a light-collecting unit that receives a beam emitted from the light source and focuses the light beam on an optical storage medium, and forms a beam reflected by the optical storage medium. An optical pickup head device comprising: a beam splitter that receives and splits a beam; and a light detector that receives a beam split by the beam splitter and outputs a signal corresponding to the received light amount. And a tracking error signal generating means for generating a tracking error signal which is a signal for performing a control for irradiating a desired track with a beam in response to a signal output from the means. When recording information on the information recording surface of the information recording medium, the beam has a first power level and a second power level, 1 is lower than the second power level, and the tracking error signal generation means samples and holds the signal output from the light detection means at the timing of the first power level, and then outputs the tracking error signal. To achieve the above object.
[0023]
Another optical information device according to the present invention includes an optical pickup head device according to any one of the above, an optical storage medium, and a driving unit that changes a relative position of the optical pickup head device; An electric signal processing unit is provided, which receives a signal output from the pickup head device and performs an operation to obtain desired information, thereby achieving the above object.
[0024]
According to the configuration of the present invention, the present invention provides an optical information recording / reproducing apparatus capable of reducing fluctuations in TE signal amplitude and reliably recording or reproducing information even when an optical storage medium having a plurality of information recording surfaces is used. The device can be realized.
[0025]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of an optical information device and an optical pickup head device of the present invention will be described with reference to the accompanying drawings. In the drawings, the same reference numerals denote the same components or those having the same action and operation.
[0026]
(Embodiment 1)
FIG. 1 shows a configuration of an optical information device as an embodiment of the present invention. The optical pickup head device 4 (or also referred to as an optical pickup) irradiates the optical storage medium 41 with laser light having a wavelength λ of 405 nm, and reproduces a signal recorded on the optical storage medium 41. The transfer controller 5 moves the optical pickup head device 4 in the radial direction of the optical storage medium 41 to record or reproduce information at an arbitrary position on the optical storage medium 41. The motor 6 that drives the optical storage medium 41 rotates the optical storage medium 41. The first control unit 7 controls the optical pickup head device 4, the transfer controller 5, and the motor 6. The amplifier 8 amplifies the signal read by the optical pickup head device 4. Reference numeral 9 denotes second control means. The output signal of the amplifier 8 is input to the second control means 9. The second control means 9 generates a servo signal such as an FE signal and a TE signal required when the optical pickup head device 4 reads the signal of the optical storage medium 41 from the signal, and converts the signal into the first control signal. Output to means 7. The signal input to the second control means 9 is an analog signal, and the second control means 9 digitizes (binarizes) the analog signal. The demodulation unit 10 analyzes the digitized signal read from the optical storage medium 41, reconstructs data such as original video and music, and outputs the reconstructed signal from the output unit 14. The detecting means 11 detects an address signal or the like from the signal output from the second control means 9 and outputs this to the system control means 12. The system control means 12 identifies the optical storage medium based on the physical format information and the optical storage medium manufacturing information (optical storage medium management information) read from the optical storage medium 41, decodes the recording / reproducing conditions and the like, and Controls the entire information device. When recording / reproducing information on / from the optical storage medium 41, the first control means 7 drives and controls the transfer controller 5 in accordance with an instruction from the system control means 12. As a result, the transfer controller 5 moves the optical pickup head device 4 to a desired position on the information recording surface 41c, and the optical pickup head device 4 records and reproduces information on the information recording surface 41c of the optical storage medium 41.
[0027]
FIG. 2 is a diagram showing an example of the configuration of the optical pickup head device according to the present invention. The light source 1 emits a linearly polarized divergent beam 70 having a wavelength λ of about 405 nm. The divergent beam 70 emitted from the light source 1 is converted into parallel light by a collimating lens 53 having a focal length f1 of 15 mm, and then enters a diffraction grating 83. The beam 70 incident on the diffraction grating 83 is split into three beams of 0-order and ± 1st-order diffracted light. The 0th-order diffracted light becomes a main beam 70a for recording / reproducing information, and the ± 1st-order diffracted lights become two sub-beams 70b and 70c for the DPP method for detecting a TE signal. The ratio of the diffraction efficiencies of the zero-order diffracted light 70a of the diffraction grating 83 and one of the first-order diffracted lights 70b or 70c is usually set to 10: 1 to 20: 1 in order to avoid unnecessary recording by the sub-beam. Here, it is 20: 1. The three beams 70a to 70c generated by the diffraction grating 83 pass through the polarizing beam splitter 52, and then enter a pair of concave lenses 81 and convex lenses 82 and transmit. The beam 70 transmitted through the convex lens 82 is transmitted through the quarter-wave plate 54 and converted into circularly polarized light, and then converted into a convergent beam by the objective lens 56 having a focal length f2 of 2 mm. The light passes through the substrate 41a and is focused on the information recording surface 41c. The optical storage medium 41 has two information recording surfaces 41b and 41c. Here, a state where the beam 70 condensed by the objective lens 56 is focused on the information recording surface 41c is shown. I have. The distance d2 from the light incident surface of the optical storage medium 41 to the information recording surface 41c is 100 μm, and the distance d1 between the information recording surfaces 41b and 41c is 25 μm. Although not shown here, the period tp of the track formed on the information recording surfaces 41b and 41c is 0.32 μm. The aperture of the objective lens 56 is limited by the aperture 55, and the numerical aperture NA is 0.85. The thickness of the transparent substrate 41a is 0.1 mm, and the refractive index n is 1.62. The equivalent reflectance of the information recording surfaces 41b and 41c is about 4 to 8%, respectively. Here, assuming that the amount of light of the beam incident on the optical storage medium 41 is 1, the equivalent reflectivity of the beam when the light exits the optical storage medium 41 again after being reflected by the information recording surface 41b or 41c is described. The light amount is shown. The information recording surface 41c absorbs or reflects most of the light amount of the incident beam, but the information recording surface 41b transmits about 50% of the light amount of the incident beam to make the beam reach the information recording surface 41c. Then, the remaining light amount of about 50% is absorbed or reflected.
[0028]
By changing the position of the concave lens 81 by the actuator 93, the amount of spherical aberration given to the beams 70a to 70c can be adjusted. The amount of spherical aberration of the beams 70a to 70c focused on the information recording surfaces 41b and 41c changes according to the distance from the surface of the optical storage medium 41 to the information recording surfaces 41b and 41c. The spherical aberration is corrected by using the concave lens 81 and the convex lens 82 so that the spherical aberration of the beam 70 condensed on 41c is reduced. By providing the concave lens 81 and the convex lens 82, information can be recorded on both of the information recording surfaces 41b and 41c in a state where the spherical aberration is small.
[0029]
The beams 70a to 70c reflected by the information recording surface 41c pass through the objective lens 56, the quarter-wave plate 54, are converted into linearly polarized light different from the forward path by 90 degrees, and then pass through the convex lens 82 and the concave lens 81. Then, the light is reflected by the polarization beam splitter 52. The beams 70a to 70c reflected by the polarization beam splitter 52 are split by a beam splitter 87 into two beams 72 and 74. Although not shown here, the beams 72 and 74 are composed of three beams 72a to 72c and 74a to 74c corresponding to the beams 70a to 70c, respectively. The light amount ratio between the beam 72 and the beam 74 is set to 1: 9. The beam 72 enters the photodetector 31 via the detection lens 59 having a focal length f3 of 30 mm and the cylindrical lens 57. Astigmatism is imparted to the beam 72 when passing through the cylindrical lens 57. When the beams 70a to 70c are focused on the information recording surface 41b or 41c, the beam 72 on the photodetector 31 has a minimum circle of confusion. On the other hand, the beam 74 is incident on the photodetector 32 through a detection lens 84 having a focal length f4 of 30 mm and a cylindrical lens 85. When the beam 74 is transmitted through the cylindrical lens 85, astigmatism is also imparted. When the beams 70a to 70c are focused on the information recording surface 41b or 41c, the beam 74 on the photodetector 32 becomes a focal line. The light source 1 is modulated at a high frequency of 400 MHz by the high frequency superimposing element 86, and the beam 70 emitted from the light source 1 has a plurality of wavelengths. By making the beam 70 emitted from the light source 1 have a plurality of wavelengths, the distribution of light and dark due to interference is reduced.
[0030]
FIG. 3 schematically shows the relationship between the photodetector 31 and the beams 72a to 72c. The beams 72a to 72c are the beams 72 split by the beam splitter 87, and the photodetector 31 has four light receiving units 31a to 31d, and the light receiving units 31a to 31d receive the beam 72a. No light receiving section for receiving the beams 72b and 72c is provided. The light receiving units 31a to 31d output current signals I31a to I31d corresponding to the received light amounts, respectively. An FE signal is obtained using the signals I31a to I31d output from the photodetector 31. The method of detecting the FE signal is an astigmatism method, that is, it is obtained by the calculation of (I31a + I31c)-(I31b + I31d).
[0031]
In addition, when the TE signal is detected by the phase difference method, the timing may be generated by comparing the output timings of I31a to I31d. Since a method of generating a TE signal by a phase difference method, which is often used when using an optical storage medium having a read-only information recording surface, is generally well known, description thereof is omitted here. Since the light quantity of the beam 72 is smaller than the light quantity of the beam 74, a sufficient signal-to-noise ratio may not be obtained when the TE signal is generated by the phase difference method. In the case of an optical storage medium having a read-only information recording surface, the allowable range of the irradiated power level is wide. Therefore, by increasing the light amount of the beam 70 emitted from the light source 1, the TE signal generated by the phase difference method is increased. The signal to noise ratio can be improved.
[0032]
The optical storage medium 41 has two information recording surfaces 41b and 41c. When the beams 70a to 70c are condensed on the information recording surface 41c to record or reproduce information, the beam is also applied to the information recording surface 41b. Is reflected and then enters the photodetector 31. The beams 73a to 73c are beams that enter the photodetector 31 by the beams 70a to 70c being reflected by the information recording surface 41b. In the photodetector 31, only the main beam 72a is received by the photodetector 31. Therefore, when the beam 72a and the beam 73a overlap, the beam 72a and the beam 73b, and the beam 72a and the beam 73c overlap, a light and dark distribution due to the interference occurs. However, the light and dark distribution due to the interference is very small, and the FE signal is not adversely affected. Without this, stable focus control is possible.
[0033]
FIG. 4 schematically shows the relationship between the photodetector 32 and the beams 74a to 74c. The beams 74a to 74c are the beams 74 split by the beam splitter 87, the photodetector 32 has six light receiving portions 32a to 32f, the light receiving portions 32a to 32b output the beam 74a, and the light receiving portions 32c to 32d output. The beam 74b is received, and the light receiving units 32e to 32f receive the beam 74c. The light receiving units 32a to 32f output current signals I32a to I32f corresponding to the amounts of light received, respectively. A TE signal is obtained using the signals I32a to I32f output from the photodetector 32. The detection method of the TE signal is the DPP method, that is, it is obtained by the calculation of (I32a-I30b) -C. {(I32c + I32e)-(I32d + I32f)}. Here, C is a coefficient determined by the ratio of the diffraction efficiencies of the zero-order diffracted light of the diffraction grating 83 and one first-order diffracted light. After the FE signal and the TE signal are amplified and phase-compensated to desired levels, the signals are supplied to actuators 91 and 92 for moving the objective lens 56 to perform focus and tracking control.
[0034]
The RF signal is obtained by the calculation of I32a + I30b. In the optical information device of the present embodiment, the beam 70 is divided into a beam 72 and a beam 74, but the light amount of the beam 72 is larger than the light amount of the beam 74. When detecting a signal, the beam is received by four light receiving units, whereas in the present optical information device, the beam is received by two small light receiving units. Therefore, the signal-to-noise ratio of the RF signal obtained by the optical information device is about 3 to 6 dB better than that of the conventional optical information device, and the optical information device can reproduce information with high reliability.
[0035]
FIG. 5 shows a configuration of a signal processing unit for generating a TE signal. The signals I32a and I32b output from the light receiving units 32a and 32b are subjected to a differential operation by a differential operation unit 801. I32a-I32b, which is a signal obtained by performing a differential operation, is a so-called push-pull TE signal. In the case where the TE signal is detected by the simple push-pull method, if the tracking of the objective lens 56 is performed according to the eccentricity of the optical storage medium 41, the TE signal undergoes an offset variation corresponding to the tracking. In this signal processing unit, the signals I32c and I32e output from the light receiving units 32c and 32e are added by an adding unit 802, and the signals I32d and I32f output from the light receiving units 32d and 32f are added by an adding unit 803. Signals output from the adders 802 and 803 are subjected to a differential operation by a differential operation unit 804. The signal output from the differential operation unit 804 is input to the variable gain amplifying unit 805, and is amplified or attenuated to a desired signal strength. The amplification degree at this time is C. The signal output from the variable gain amplifying section 805 has the same fluctuation as the offset fluctuation corresponding to the tracking following of the signal output from the differential operation section 801. The differential operation unit 806 performs a differential operation by receiving the signal output from the differential operation unit 801 and the signal output from the variable gain amplifying unit 805, so that the signal output from the differential operation unit 801 is output. The offset fluctuation according to the tracking following is reduced. The signal output from the differential operation unit 806 outputs a TE signal having almost no offset fluctuation even if tracking is performed, but as it is, the reflectance of the information recording surfaces 41b and 41c of the optical storage medium 41, the optical storage medium Since the signal intensity changes in accordance with the change in the intensity of the beam applied to 41, the signal intensity is input to the division unit 808 so that the amplitude becomes constant. After the signals I32a to I32b output from the light receiving units 32a to 32b are added by the adding unit 807, the signals are input to the dividing unit 808 as signals for performing division. The signal output from the adder 807 is a signal proportional to the reflectivity of the information recording surfaces 41b and 41c of the optical storage medium 41 and the intensity of the beam applied to the optical storage medium 41, and the signal output from the divider is The result is a TE signal having the desired strength.
[0036]
The optical storage medium 41 has two information recording surfaces 41b and 41c. When the beams 70a to 70c are condensed on the information recording surface 41c to record or reproduce information, the beam is also applied to the information recording surface 41b. Is reflected and then enters the photodetector 32. The beams 75a to 75c are beams that enter the photodetector 32 when the beams 70a to 70c are reflected by the information recording surface 41b. Since the beam 70 is focused on the information recording surface 41c, the beam is largely defocused on the information recording surface 41b. Therefore, the beams 75a to 75c are also largely defocused on the photodetector 45. The photodetector 32 receives both the main beam 74a and the sub beams 74b and 74c. Therefore, when the beams 74b and 75a and the beams 74c and 75a overlap each other, a light and dark distribution due to the interference occurs. The light and dark distribution due to the interference is extremely small as compared with the change in the conventional optical pickup head device. . This is because when the beams 70a to 70c are focused on the information recording surface 41b or 41c, the beams 74a to 74c on the photodetector 32 are focused. That is, when the direction in which the beams 74a to 74c are arranged on a virtual straight line on the surface of the photodetector 32 is the X direction, and the direction orthogonal to the X direction is the Y direction, the size of the beams 74a to 74c in the X direction is The length is smaller than the size in the Y direction. As the size of the beams 74a to 74c in the X direction is reduced, the amount of light per unit area in the beams 74a to 74c increases, and the effect of light and dark due to the interference decreases. When the diameter of the minimum circle of confusion of the beam on the photodetector of the general optical pickup head device is 100 μm and the size of the beams 74a to 74c in the Y direction is also 100 μm, the size of the beams 74a to 74c in the X direction Is about 5 μm. Therefore, the amount of light per unit area in the beams 74a to 74c is 20 times higher than the beam of the minimum circle of confusion having the same size in the Y direction. Of course, this is the case where the focal length f4 of the detection lens 84 is 30 mm. If the focal length f4 of the detection lens 84 is shortened, the size of the focal line in the X direction is further reduced accordingly, and the beam 74a It is also possible to increase the amount of light per unit area in the range of 74c to 74c and further reduce the influence of interference. In this embodiment, the focal length f3 of the condenser lens 59 and the focal length f4 of the condenser lens 84 are set to the same 30 mm in order to reduce the types of components by using a common component. It is possible to design the optical system with arbitrary values. Further, since the light receiving portions 32a to 32f can be made smaller, the size of the photodetector 32 can be made smaller, resulting in a low-cost optical pickup head device.
[0037]
FIG. 6 is a diagram showing a state when the TE signal obtained by the optical information device according to the present embodiment is observed with an oscilloscope. Both the amplitude TEpp and the symmetry of the TE signal are very stable, and stable tracking control is possible.
[0038]
The size h1 in the X direction of the light receiving units 32a to 32b that receive the beam 74a is smaller than the size h2 in the Y direction. This is possible because the size of the beams 74a to 74c in the X direction is smaller than that in the Y direction. Although it depends on the optical design, h1 can be reduced to about 1/20 of h2. By making the sizes of the beams 74a to 74c and the light receiving portions 32a to 32f in the X direction smaller than the sizes in the Y direction, the intervals between the beams 70a to 70c on the information recording surfaces 41b and 41c of the optical storage medium 41 are reduced. The eccentricity of the optical storage medium 41 can be reduced accordingly, and the fluctuation of the amplitude of the TE signal due to the eccentricity is reduced, thereby enabling stable tracking control. In the optical information device of the present embodiment, the grating period of the diffraction grating 83 is set to be two to five times larger than the grating period of the diffraction grating 58 in the conventional optical pickup head device. When assembling the optical information device, it is necessary to adjust the setting angle of the diffraction grating so that the beams 70a to 70c are at desired positions on the optical storage medium 41. The accuracy is greatly relaxed as compared with the diffraction grating in the conventional optical pickup head device, and an optical information device with high productivity can be provided.
[0039]
The information recorded on the information recording surfaces 41b and 41c of the optical storage medium 41 can be obtained by adding signals output from the light receiving units 32a and 32b. When the size of the light receiving sections 32a and 32b in the X direction is reduced, the parasitic capacitance of the light receiving sections 32a and 32b is reduced accordingly. When the light receiving sections 32a and 32b are constituted by photodiodes, current is output from the light receiving sections 32a and 32b. When the current signals output from the light receiving units 32a and 32b are converted into voltage signals using a transimpedance amplifier or the like, noise increases due to the parasitic capacitance of the light receiving units 32a and 32b. The smaller the parasitic capacitance of the light receiving units 32a and 32b, the smaller the noise, and the optical information device of the present embodiment can reproduce the information recorded on the information recording surfaces 41b and 41c with high reliability.
[0040]
Note that the concave lens 81 and the convex lens 82 as the spherical aberration correcting means are merely examples, and any general configuration such as a liquid crystal element can be applied.
[0041]
(Embodiment 2)
FIG. 7 schematically shows the relationship between the photodetector 33 and the beams 74a to 74c as an example of another optical information device according to the present invention. By using the photodetector 33 instead of the photodetector 32 included in the optical pickup head device 401, an optical information device can be configured. The photodetector 33 has ten light receiving units 33a to 33j, and outputs signals I33a to I33j corresponding to the amounts of received light. The light receiving units 33a to 33b receive the beam 74a, the light receiving units 33c to 33f receive the beam 74b, and the light receiving units 33g to 33j receive the beam 74c. That is, the light receiving units 33c to 33f correspond to 32c to 32d in the photodetector 32, and the light receiving units 33g to 33j correspond to 32e to 32f in the photodetector 32. For the operation for obtaining the TE signal, the photodetector 32 is used. The signal output from the corresponding light receiving unit may be calculated in the same manner when the signal is used and when the photodetector 33 is used.
[0042]
By receiving the beams 74b to 74c with the four light receiving units 33c to 33f and 33g to 33j, the positional relationship between the photodetector 33 and the beam 74 when assembling the optical pickup head device can be easily confirmed. By the calculation of (I33c + I33d)-(I33e + I33f), the positional relationship in the Y direction between the light receiving units 33c to 33f and the beam 74b is determined by the calculation of (I33c + I33e)-(I33d + I33f). The positional relationship in the direction can be easily confirmed. The same applies to the light receiving units 33g to 33j and the beam 74c. Since the positional relationship between the photodetector 33 and the beam 74 can be easily and accurately adjusted, even if the positional relationship between the photodetector 33 and the beam 74 is deviated due to aging, the accuracy in assembling the optical information device can be improved. Since the adjustment is performed well, the effect of the change with time is less likely to occur, and the detected TE signal is less deteriorated. Therefore, the optical information device described in this embodiment is a highly reliable optical information device.
[0043]
When an RF signal is detected using the light receiving units 33a and 33b, it is preferable that the number of the light receiving units that receive the beam 74a be two from the viewpoint of maintaining a good signal-to-noise ratio. When the beam 74a is received by the four light receiving units, the signal-to-noise ratio is deteriorated by 3 dB as compared with the case where the beam 74a is received by the two light receiving units. Of course, the beam 74a may be received by four light receiving units when the signal-to-noise ratio has a margin.
[0044]
Also, since there is almost no deviation in the interval between the beams 74a to 74c, even if only one of the light receiving portions 33c to 33f and the light receiving portions 33g to 33j is used as four light receiving portions, the beams 74a to 74c and the light The positional relationship with the detector 33 can be adjusted with high accuracy.
[0045]
(Embodiment 3)
FIG. 8 schematically shows the relationship between the photodetector 34 and the beams 74a to 74c as an example of another optical information device according to the present invention. By using the photodetector 34 instead of the photodetector 32 included in the optical pickup head device 401, an optical information device can be configured. The photodetector 34 has fourteen light receiving portions 34a to 34n, and outputs signals I34a to I34n corresponding to the amounts of light received, respectively. The light receiving units 34a to 34b receive the beam 74a, the light receiving units 34c to 34h receive the beam 74b, and the light receiving units 34i to 34n receive the beam 74c. That is, the light receiving units 34c to 34h correspond to 32c to 32d in the photodetector 32, and the light receiving units 34i to 34n correspond to 32e to 32f in the photodetector 32. For the operation for obtaining the TE signal, the photodetector 32 is used. The signals output from the corresponding light receiving units may be calculated in the same manner when using the light detector and when using the photodetector 34.
[0046]
By receiving the beams 74b to 74c with the six light receiving units 34c to 34h and 34i to 34n, the positional relationship between the photodetector 34 and the beam 74 when assembling the optical pickup head device can be easily confirmed. By the calculation of (I34c + I34d + I34e)-(I34f + I34g + I34h), the positional relationship between the light receiving units 34c to 34h and the beam 74b in the Y direction is calculated by (I34c + I34f)-(I34e + I34h). The positional relationship in the direction can be easily confirmed. Here, by providing the light receiving portions 34d and 34g having the width h3 of 5 to 10 μm, the positional relationship between the condenser lens 84 and the photodetector 34 can be easily confirmed. If the distance between the condenser lens 84 and the photodetector 34 is adjusted so that the signals output from the light receiving units 34d and 34g are maximized, the TE signal is hardly affected by interference. Although not described here, the same applies to the light receiving units 34i to 34n and the beam 74c. Since the positional relationship between the photodetector 34 and the beam 74 and the positional relationship between the condenser lens 84 and the beam 74 can be easily and accurately adjusted, the positional relationship between the photodetector 34 and the beam 74, and Even if the positional relationship between the condenser lens 84 and the beam 74 is deviated, since the adjustment is performed accurately when assembling the optical information device, it is hardly affected by a change over time, and the deterioration of the detected TE signal is small. Therefore, the optical information device described in this embodiment is a highly reliable optical information device.
[0047]
(Embodiment 4)
FIG. 9 schematically shows the relationship between the photodetector 35 and the beams 74a to 74c as an example of another optical information device according to the present invention. By using the photodetector 35 instead of the photodetector 32 included in the optical pickup head device 401, an optical information device can be configured. The photodetector 35 has eight light receiving sections 35a to 35h, and outputs signals I35a to I35h corresponding to the amounts of received light. The light receiving units 35a to 35b receive the beam 74a, the light receiving units 35c to 35d receive the beam 74b, and the light receiving units 35e to 35f receive the beam 74c. That is, the light receiving units 35c to 35d correspond to 32c to 32d in the photodetector 32, and the light receiving units 35e to 35f correspond to 32e to 32f in the photodetector 32. For the operation for obtaining the TE signal, the photodetector 32 is used. The signals output from the corresponding light receiving units may be calculated in the same manner when using the light detector and when using the photodetector 35.
[0048]
By providing the light receiving unit 35g between the light receiving units 35a to 35b and 35c to 35d and the light receiving unit 35h between the light receiving units 35a to 35b and 35e to 35f, between the light receiving units 35a to 35b and 35c to 35d, In addition, the degree of electrical separation between the light receiving units 35a to 35b and 35e to 35f is increased. The width h4 of the light receiving unit 35g is selected to be about 1 to 10 μm. The same applies to the light receiving unit 35h. It is necessary to change the interval between the beams 74a to 74c on the photodetector 35 according to the width of the light receiving portions 35g and 35h. In this case, the period of the grating formed on the diffraction grating 83 and the The optical conditions such as the focal length f4 may be appropriately designed. A signal based on receiving the beam 72a by the light receiving portions 35a to 35b by increasing the degree of electrical separation between the light receiving portions 35a to 35b and 35c to 35d and between the light receiving portions 35a to 35b and 35e to 35f. Are reduced in the degree of being mixed into the signals output from the light receiving units 35c to 35f, and a more stable TE signal can be detected.
[0049]
(Embodiment 5)
FIG. 10 shows a configuration of a signal processing unit for generating a TE signal as an example of another optical information device according to the present invention. By using this signal processing unit instead of the signal processing unit in the optical information device described in Embodiment 1, an optical information device can be configured. The difference between the present signal processing unit and the signal processing unit in the optical information device described in Embodiment 1 is that a sample and hold unit 809 is provided.
[0050]
FIG. 11 schematically shows the relationship between the data recorded on the information recording surface 41b or 41c and the recording power. Information is recorded on the information recording surface 41b or 41c as a mark string. Here, the mark is recorded by a multi-pulse, and the power levels used are in three stages of P1 to P3. The power level P1 is used for cooling when forming a mark, and is 0.6 mW here. This is about the same as the power level used when reproducing the information recorded on the information recording surface 41b or 41c. The power level P2 is used for erasing, and is 4.0 mW here. The power level P3 is used for forming a mark, and is 10.0 mW here. In the optical information device of the present embodiment, the signal at the timing of the power level P1 is sampled and held by the sample and hold unit 809 to generate a TE signal. This means that even if the light source 1 is modulated at a high frequency of 400 MHz by the high-frequency superimposing element 86 so that the beam 70 emitted from the light source 1 has a plurality of wavelengths, a plurality of light beams gradually increase as the power level increases. This is because it becomes difficult to have a wavelength. By generating the TE signal using the beam at the timing of the power level P1, that is, the timing when the power level is low, the influence of the distribution of light and dark due to interference can be reduced even when information is recorded, and the stable TE A signal can be obtained.
[0051]
(Embodiment 6)
FIG. 12 shows a configuration of an optical pickup head device 402 constituting an optical information device as an example of another optical information device according to the present invention. An optical information device can be formed by using the optical pickup head device 402 instead of the optical pickup head device 401 in the optical information device described in Embodiment 1. The difference between the optical pickup head device 402 and the optical pickup head device 401 in the optical information device shown in the first embodiment is that the beam splitter 88 is used instead of the beam splitter 87, and the photodetector 36 is used instead of the photodetectors 31 to 32. That is, is used. The beam splitter 88 has two reflection films 88a and 88b. The reflection film 88a splits the incident beam 70 into two beams 72 and 74. The beam 72 is a beam transmitted through the reflection film 88a, and the beam 74 is a beam reflected from the reflection film 88a. The light quantity ratio between the beams 72 and 74 is 1: 9. The beam 74 reflected by the reflection film 88a is reflected by the reflection film 88b, and the optical path is bent. The beams 72 and 74 are received by the photodetector 36 after passing through the detection lenses 59 and 84 and the cylindrical lenses 57 and 85, respectively.
[0052]
FIG. 13 schematically shows the relationship between the photodetector 36 and the beams 72a to 72c and 74a to 74c. The photodetector 36 is formed of one semiconductor substrate, has ten light receiving portions 36a to 36j, and outputs signals I36a to I36j corresponding to the amounts of light received, respectively. The light receiving units 36a to 36b receive the beam 74a, the light receiving units 36c to 36d receive the beam 74b, the light receiving units 36e to 36f receive the beam 74c, and the light receiving units 36g to 36j receive the beam 72a. That is, the light receiving units 36a to 36f correspond to the light receiving units 32a to 32f in the photodetector 32, and the light receiving units 36g to 36j correspond to the light receiving units 31a to 31d in the photodetector 31, respectively. By using the photodetector 36, the size of the optical pickup head device can be reduced as compared with the case where the photodetector 31 and the photodetector 32 are used, thereby realizing a small optical information device. can do.
[0053]
The embodiment described above is an example, and various embodiments can be adopted without departing from the spirit of the present invention. It goes without saying that various modifications can be made without departing from the spirit of the present invention, such as using an unpolarized optical system. Since it has nothing to do with the gist of the present invention, the FE signal detection method other than the astigmatism method was not described. However, the present invention has no restrictions on the FE signal detection method, and the spot size detection method, the Foucault method, and the like. All the usual FE signal detection methods such as the method can be used. The focal lengths f1 to f4 of the lens and the numerical aperture NA are not particularly limited, and the focal length may be determined as needed.
[0054]
Also, the case where the optical storage medium 41 has two information recording surfaces has been described, but it goes without saying that the same effect can be obtained even when the optical storage medium has three or more information recording surfaces. Of course, the same applies to a surface that reflects another beam, such as the surface of an optical storage medium.
[0055]
Further, the same effect of the present invention can be obtained when a TE signal is detected by using a simple push-pull method.
[0056]
【The invention's effect】
As described above, according to the present invention, even when an optical storage medium having a plurality of information recording surfaces is used, an optical information device capable of reducing fluctuations in TE signal amplitude and reliably recording or reproducing information can be provided. realizable.
[Brief description of the drawings]
FIG. 1 is a diagram showing a schematic configuration of an optical information device according to a first embodiment of the present invention;
FIG. 2 is a diagram showing a configuration of an optical pickup head device constituting the optical information device according to the first embodiment of the present invention;
FIG. 3 is a diagram showing a relationship between a track and a beam on an optical storage medium in the optical information device according to the first embodiment of the present invention.
FIG. 4 is a diagram illustrating a relationship between a light detector and a beam included in an optical pickup in the optical information device according to the first embodiment of the present invention;
FIG. 5 is a diagram illustrating a configuration of a signal processing unit included in the optical information device according to the first embodiment of the present invention.
FIG. 6 is a diagram showing a state of a TE signal obtained by the optical information device according to the first embodiment of the present invention.
FIG. 7 is a diagram illustrating a relationship between a light detector and a beam included in an optical pickup in the optical information device according to the second embodiment of the present invention;
FIG. 8 is a diagram showing a relationship between a photodetector and a beam included in an optical pickup in the optical information device according to the third embodiment of the present invention.
FIG. 9 is a diagram illustrating a relationship between a photodetector and a beam included in an optical pickup in an optical information device according to a fourth embodiment of the present invention.
FIG. 10 is a diagram showing a configuration of a signal processing unit included in an optical information device according to a fifth embodiment of the present invention.
FIG. 11 is a diagram showing a relationship between recording data and sampling timing in an optical information device according to a fifth embodiment of the present invention.
FIG. 12 is a diagram showing a configuration of an optical pickup head device constituting an optical information device according to a sixth embodiment of the present invention.
FIG. 13 is a diagram showing a relationship between a light detector and a beam constituting an optical pickup in the optical information device according to the sixth embodiment of the present invention.
FIG. 14 is a diagram showing a configuration of an optical pickup head device constituting a conventional optical information device.
FIG. 15 is a diagram showing a relationship between a track and a beam on an optical storage medium in a conventional optical information device.
FIG. 16 is a diagram showing a relationship between a light detector and a beam constituting an optical pickup in a conventional optical information device.
FIG. 17 is a diagram showing a state of a TE signal obtained by a conventional optical information device.
[Explanation of symbols]
1 light source
4,401-402 Optical pickup
5 Transfer controller
6 motor
7 First control means
8 Amplifier
9 Second control means
10 Demodulation means
11 Detecting means
12 System control means
14 Output means
30-36 light detector
30a to 30h, 31a to 31d, 32a to 32f, 33a to 33j, 34a to 34n, 35a to 35h, 36a to 36j
41 Optical storage media
41 Transparent substrate
41b, 41c Information recording surface
52 Polarizing beam splitter
53 collimating lens
54 Quarter Wave Plate
55 aperture
56 Objective lens
57,85 cylindrical lens
58,83 diffraction grating
59,84 Condensing lens
70, 70a to 70c, 71a to 71c, 72, 72a to 72c, 73a to 73c, 74, 74a to 74c, 75a to 75c Beam
81 concave lens
82 convex lens
86 High frequency superposition element
87,88 beam splitter
91-93 Actuator
801, 804, 806 differential operation unit
802, 803, 807, 813 Adder
805, 810, 812 Variable gain amplifier
808 Division unit
809 Sample and hold section

Claims (12)

A light source that emits a light beam; diffraction means for receiving a beam emitted from the light source to generate a plurality of diffracted beams of zero-order and first-order or more; and optical storage for receiving a plurality of beams from the diffraction means Focusing means for focusing on a medium; beam splitting means for splitting a beam by receiving a plurality of beams reflected by the optical storage medium; receiving a plurality of beams split by the beam splitting means; Light detecting means for outputting a signal corresponding to the amount of light, wherein the zero-order diffracted light generated by the diffracting means is used as a main beam, and two or more first-order diffracted lights generated by the diffracting means are used as first beams. And a second sub-beam, wherein the light detecting means has a plurality of light receiving sections, and the plurality of beams are arranged substantially on one virtual straight line on the light detecting means. Receiving the beam When the direction of the virtual straight line is the first direction and the direction orthogonal to the first direction is the second direction, the magnitude of the plurality of beams in the first direction is An optical pickup head device having a size smaller than the size in the second direction. 2. The optical pickup head device according to claim 1, wherein the plurality of beams are substantially focused in a first direction on a surface of the light detection unit that receives the plurality of beams. 3. The main beam, the first sub beam, and the second sub beam are respectively received by a plurality of light receiving units, and the plurality of light receiving units that receive the main beam are a first light receiving unit group, and the first sub beam is received. The plurality of light receiving units is a second light receiving unit group, the plurality of light receiving units for receiving the second sub-beam is a third light receiving unit group, and the size of the first light receiving unit group in the first direction is 3. The optical pickup head device according to claim 1, wherein the size is smaller than the size in the second direction. The size of the second light receiving unit group in the first direction is smaller than the size of the second light receiving unit group, and the size of the third light receiving unit group in the first direction is larger than the size in the second direction. The optical pickup head device according to claim 3, wherein the optical pickup head device is small. The optical pickup head device according to claim 1, further comprising a light receiving unit in addition to the first to third light receiving unit groups. The light receiving unit is provided between the first light receiving unit group and the second light receiving unit group and between the first light receiving unit group and the third light receiving unit group, respectively. Item 6. The optical pickup head device according to item 5. The optical pickup head device according to any one of claims 1 to 6, wherein the second light receiving unit group or the third light receiving unit group includes three or more light receiving units. The optical pickup head device according to claim 7, wherein the second light receiving unit group or the third light receiving unit group comprises six light receiving units. A light source that emits a light beam, diffraction means for receiving a beam emitted from the light source to generate a plurality of diffracted beams of zero-order and first-order or more, and optical storage for receiving a plurality of beams from the diffraction means Focusing means for focusing on a medium; beam splitting means for receiving a plurality of beams reflected by the optical storage medium and splitting the beam into a first beam group and a second beam group; Light detecting means for receiving a beam group and a second beam group and outputting a signal corresponding to the received light amount, wherein the 0th-order diffracted light generated by the diffracting means is used as a main beam, and The two or more first-order diffracted lights are defined as a first sub-beam and a second sub-beam, and the photodetector has a plurality of light-receiving units, and the main beam and the first sub-beam constitute the second beam group. Sub-beam and second sub-beam On the light detecting means, they are arranged substantially on one virtual straight line, and on the surface of the light detecting means which receives the beam, the direction of the virtual straight line is a first direction; The size of the plurality of beams in the first direction is smaller than the size in the second direction when the direction orthogonal to the second direction is set as the second direction. The optical pickup head device according to claim 9, wherein the light amount of the second beam group is larger than the light amount of the first beam group. A light source for emitting a light beam, a light condensing means for receiving the beam emitted from the light source and condensing the light beam on an optical storage medium, and a beam splitting means for receiving the beam reflected by the optical storage medium and splitting the beam An optical pickup head device comprising: a light detection unit that receives a beam split by the beam splitting unit and outputs a signal corresponding to the received light amount; and receives a signal output from the light detection unit. A tracking error signal generating means for generating a tracking error signal which is a signal for performing control to irradiate a desired track with a beam, wherein the optical storage medium has a plurality of information recording surfaces on which information is recorded. When recording information on the information recording surface of the information recording medium, the beam has a first power level and a second power level, and the first power level is the second power level. And the tracking error signal generating means generates a tracking error signal after sampling and holding the signal output from the light detecting means at the timing of the first power level. Optical information device. An optical pickup head device according to any one of claims 1 to 10, an optical storage medium, a drive unit for changing a relative position of the optical pickup head device, and an output from the optical pickup head device. An optical information device comprising: an electrical signal processing unit that receives a signal and performs an operation to obtain desired information.

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