JP2009015944A - Optical disk device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To correct aberrations by detecting aberrations caused by adjustment of an optical element or aberrations generated by an optical recording medium. <P>SOLUTION: A homodyne system is applied to an optical system, aberrations are directly detected from a signal or the value of a phase difference obtained by using the homodyne system, the optical element of a unique grating structure, and a photodetector divided into two or more, and aberrations are corrected based on the result. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an optical disc apparatus having an optical aberration detection mechanism and an aberration correction mechanism.

  In order to perform recording and reproduction at high density and high speed in the optical recording technology, the aberration of the optical system needs to be suppressed to a certain standard or less. As this standard, when the wavelength of the light source to be used is λ, it is necessary to satisfy the Marshall standard, for example, 0.07λ as a root mean square (RMS) value of aberration. However, due to the increase in the numerical aperture (NA) associated with the recent increase in the density of optical discs, aberrations that exceed this standard can easily occur even with slight optical component deviations, disc substrate tilts, and thickness deviations. It has become easier. Since the size of the spot focused by the objective lens is proportional to λ / NA, it has been studied to increase the NA in order to increase the recording density. However, in general, the sensitivity of aberration generation with respect to deviation is proportional to the power of NA. For example, astigmatism caused by the tilt of the objective lens is the square of NA, the coma caused by the tilt of the disk is the cube of NA, and the disk substrate. Spherical aberration that occurs due to the difference in thickness of the lens generates aberration proportional to the fourth power of NA. For this reason, in order to reduce the accuracy of optical component adjustment, disk tilt, substrate thickness deviation, and the like as much as possible, it is necessary to devise a technique for suppressing the generated aberration. Therefore, for example, a method of detecting and correcting spherical aberration for disc substrate thickness deviation (Japanese Patent Laid-Open No. 2001-307349), or a method of controlling an aberration correction element so that the amplitude of a reproduction signal is as large as possible (Japanese Patent Laid-Open No. 2001-307349). 2005-100483) and the like have been proposed. In addition, although it is not specified to be used in an optical disk optical system, the phase of diffracted light is changed using diffraction gratings having different grating groove directions, and 0th-order light and + 1st-order light (−1st-order light) are used. For example, a detection method using sharing interference.

JP 2001-307349 A JP 2005-100483 A JP 2002-202223 A

  The method described in Japanese Patent Laid-Open No. 2001-307349 assumes only detection of spherical aberration, and has a problem that it cannot detect aberrations such as coma and astigmatism. The method described in Japanese Patent Laid-Open No. 2005-100483 does not directly detect aberrations, but is a method for searching for a correction condition with as little signal amplitude degradation as possible and as large signal amplitude as possible. In addition to the need for mistakes, there is a problem that the differential coefficient of change near the peak becomes 0 and the detection error is large. The method using sharing interference described in Japanese Patent Application Laid-Open No. 2002-202223 has a problem that the mechanism is complicated and large in size, has a large amount of power consumption, and is difficult to mount on an optical disc apparatus.

  In view of the above problems of the prior art, the problem to be solved by the present invention is to provide a highly efficient optical disc apparatus capable of detecting and correcting an arbitrary aberration with a simple structure.

  In the present invention, a method called a homodyne light detection method is applied to the optical system of the optical disk device, and the aberration of the light beam reflected from the optical disk is detected not directly but as a phase distribution. Aberration correction is performed. The homodyne light detection method is a method studied for increasing the S / N ratio of detection signals in the field of optical communication, and is usually used for the purpose of signal amplitude amplification. However, in the present invention, it is used for detecting the phase of light.

  An optical disc apparatus according to the present invention includes a light source such as a semiconductor laser, a first dividing unit that divides light emitted from the light source into first and second light beams, a unit that corrects aberration, and a component for correcting aberration. Means for performing feedback control, means for condensing and irradiating the first light flux on the optical information recording medium, means for reflecting the second light flux as reference light without condensing on the optical information recording medium, and The signal light reflected from the optical information recording medium and the reference light are again guided to the first splitting means to superimpose and interfere with the third light flux, and the signal light included in each of the split lights A second dividing unit that makes the phase relationship of the reference light different from each other, and each fourth light beam divided by the second dividing unit is divided into a plurality of mutually corresponding regions, and the light intensity for each region Is detected as an electrical signal. Means for calculating the phase difference between the signal light and the reference light in each corresponding region of the third light flux using the electrical signals of each corresponding region of all the fourth light fluxes, Control means for controlling the aberration correction means is provided.

  According to the present invention, it is possible to detect an arbitrary aberration regardless of a simple structure, and it is possible to perform good recording and reproduction by correcting the detected aberration. Further, it is possible to realize a light weight and downsizing that can be mounted on an optical disk device.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic view showing an example of an optical disc apparatus according to the present invention. The light from the semiconductor laser 101 is converted into parallel light by the collimator lens 102, transmitted through the λ / 2 plate 103, and incident on the polarizing prism 104. The polarizing prism 104 has a function of transmitting almost 100% of the P-polarized light incident on the separation surface and reflecting almost 100% of the S-polarized light. At this time, by adjusting the rotation angle around the optical axis of the λ / 2 plate, a part of the light can be reflected as the S-polarized light and the polarizing prism 104 can be reflected, and a part of the light can be transmitted as the P-polarized light. . The reflected light passes through the λ / 4 plate 105 and is converted into circularly polarized light, and is condensed on the recording film on the optical disk 108 by the objective lens 107 mounted on the two-dimensional actuator 106. The reflected light from the optical disk returns to the same optical path, is converted into parallel light by the objective lens 107, and is incident on the polarizing prism 104 as linearly polarized light whose polarization direction is rotated by 90 ° when it is first incident on the λ / 4 plate 105. To do. Then, since the polarized light is rotated, the reflected light from the optical disk 108 becomes P-polarized light, passes through the polarizing prism 104, and enters the polarizing prism 125.

  On the other hand, of the light from the semiconductor laser 101, P-polarized light transmitted through the polarizing prism 104 is converted into circularly polarized light by the λ / 4 plate 110, and the corner cube prism 112 mounted on the one-dimensional actuator 111 movable in the optical axis direction. Is incident on. The corner cube prism 112 has a shape in which a cube is cut by a plane perpendicular to a diagonal line connecting opposite vertices of the cube. When light is incident from the cut surface, the incident angle is any incident angle. However, due to the symmetry of the reflected light path, the reflected light always returns in the same direction as the incident light. Since the polarization direction of the reflected light from the corner cube prism 112 is rotated, the compensating element 130 is compensated by being attached to the corner cube ridge line. The compensated reflected light, that is, the reference light returns along the same optical path with the same optical axis, and enters the polarizing prism 104 as linearly polarized light whose polarization direction is rotated by 90 ° by the λ / 4 plate 110. Then, since the polarized light is rotated, the reflected light from the corner cube prism 112 becomes S-polarized light, reflects off the polarizing prism 104, and enters the polarizing prism 125 so as to overlap with the reflected light from the optical disk. However, the reflected light from the optical disk 108 and the reflected light from the corner cube prism 112 are linearly polarized light orthogonal to each other.

  Unlike the polarizing prism 104, the polarizing prism 125 has a function of transmitting part of the P-polarized light and reflecting almost 100% of the S-polarized light. As a result, almost 100% of the reflected light from the corner cube prism 112 is reflected, and a part of the reflected light from the disk is transmitted through the polarizing prism 125 and a part thereof is reflected. The reflected light is incident on the polarization phase converting / separating element 114 and further divided into four lights having different phase differences of interference between the two lights. The four lights having different phase differences are further divided by the diffraction grating 116 for aberration detection, and are collected and detected by the condenser lens 118 on the photodetector 115.

  Here, the polarization phase conversion / separation element 114, the diffraction grating 116 for detecting aberration, the photodetector 115, and the subsequent signal processing of the signal from the photodetector will be described in detail.

  As shown in FIG. 2, the polarization phase conversion / separation element 114 does not act on one of at least two lights divided by the non-polarization diffraction grating 203 and the non-polarization diffraction grating 203, and at least the other light is circularly polarized. An angle selective polarization conversion element 204 and a polarization separation element 205 which are made of the same substrate to be converted into Of these, the angle-selective polarization conversion element 204 is formed of a uniaxial anisotropic optical material having an optical axis in the optical axis direction, and further formed integrally with the polarization separation element 205 to achieve miniaturization. .

  First, when the signal light and the reference light are incident on the non-polarized diffraction grating 203 so that the signal light polarization direction 201 and the reference light polarization direction 202 are orthogonal to each other, both the two lights have two different traveling directions regardless of the polarization direction. Separate into light. This can be easily done by blazing the non-polarized diffraction grating 203. One is a 0th-order light traveling straight, and the other is a first-order diffracted light diffracted at a predetermined diffraction angle. Next, these lights have uniaxial anisotropy in which the optical axis 206 is perpendicular to the surface of the element, and the diffraction directions of the diffracted light are substantially 45 respectively in the signal light polarization direction 201 and the reference light polarization direction 202. When entering the angle-selective polarization conversion element 204 that makes a degree, there is no phase difference in the 0th-order light traveling straight, but the tilted incident first-order diffracted light produces a phase difference, and the signal light and the reference light rotate in the rotation direction. Is converted into circularly polarized light in the reverse direction. Further, the outgoing light of the angle selective polarization conversion element 204 is made incident on the polarization separation diffraction grating 205 with the optical axis 207 oriented in the figure. The polarization separation diffraction grating can be easily realized by forming a blaze grating with an anisotropic material such as liquid crystal, lithium niobate, or quartz. That is, since the refractive index differs depending on the polarization direction, the phase distribution applied by the grating may be reversed between a certain polarization direction and a polarization direction perpendicular thereto. As a result, the first-order diffracted light and the −1st-order diffracted light can be in the polarization directions orthogonal to each other. The phase difference of interference between the signal light component and the reference light component in the four lights separated as described above can be set to 0 °, 90 °, 180 °, and 270 °.

  FIG. 3 is a diagram for explaining that the phase difference of interference of four lights becomes 0 °, 180 °, 90 °, and 270 °. In the figure, Eref is an electric field vector of reference light, and Esig is an electric field vector of signal light. 3A shows the polarization state on the linearly polarized light side in FIG. 2, and FIG. 3B shows the polarization state on the circularly polarized light side. PD1, PD2, PD3, and PD4 mean light receiving portions (not shown) on the photodetector 115 in FIG. 1 that receive light having phase differences of 0 °, 180 °, 90 °, and 270 °, respectively. 3 (a) and 3 (b) mean that the light projected on the oblique axis is a component of the light received by the corresponding light receiving unit. Since the polarization directions of the reference light and the signal light are orthogonal to each other, the projection vector to each polarization component separated by the polarization separation diffraction grating has the same direction of the arrow on the PD1 side and the reverse direction of the arrow on the PD2 side. As a result, interference occurs when the phase difference between the reference light and the signal light is 0 ° in PD1, and the phase difference is 180 ° in PD2. Next, in FIG. 3B, since both the reference light and the signal light are circularly polarized light having different rotation directions, the projection vector to the PD3 side and the projection vector to the PD4 side indicate vectors at the tip of the arrow. That is, it is shifted to the middle position instead of the end of the line segment. The phase difference at this time is 90 ° and 270 °, respectively.

  In the present invention, as will be described later, these PD1, PD2, PD3, and PD4 are further spatially divided to detect the phase distribution of the reflected light beam of the disk, that is, the aberration distribution. The following explains that the amplitude of the signal light is amplified by the amplitude of the reference light by the homodyne detection method, and the phase difference between the signal light and the reference light is obtained by calculation. The interference intensity of light incident on the photodetector is PD1 (0 °), PD2 (180 °), PD3 (90 °), and PD4 (270 °).

と表される。添字のsigは信号光、refは参照光を意味する。したがってこれらを用いて以下のような差動演算を行う。

It is expressed. The subscript sig means signal light, and ref means reference light. Therefore, the following differential calculation is performed using these.

さらにこれらを用いて

Furthermore, using these

のように参照光振幅により増幅された信号振幅と、参照光と信号光の位相差が求められることがわかる。従来のホモダイン検出では主に、この信号増幅効果を狙っているのであるが、本発明においては位相差を求める演算を光束内で分割して行うことにより、収差を検出するのである。

It can be seen that the signal amplitude amplified by the reference light amplitude and the phase difference between the reference light and the signal light are obtained. The conventional homodyne detection mainly aims at this signal amplification effect, but in the present invention, the aberration is detected by dividing the calculation for obtaining the phase difference in the light beam.

  Next, the aberration detection diffraction grating 116 in FIG. 1 and the photodetector 115 that receives light emitted from the aberration detection diffraction grating 116 will be described with reference to FIGS. 4, 5, 6, and 7. . First, the reason why the diffraction grating for aberration detection is made into an n-divided structure as shown in FIGS. The aberration W is obtained by using Zernike's orthogonal polynomial in polar coordinates where the radial axis coordinate normalized by the radius of the effective diameter is ρ and the radial angle is θ, with the optical axis of the light beam as the origin.

と展開することができる。右辺の第１項は定数の位相オフセット、第２項はｘ方向のチルト、第３項はｙ方向のチルト、第４項はデフォーカス、第５項は動径角０°または９０°方向の非点収差、第６項は動径角４５°方向の非点収差、第７項は動径角０°方向のコマ収差、第８項は動径角９０°方向のコマ収差、第９項は３次の球面収差であり、Ａ_nは各収差係数である。これらがいわゆる３次収差までの展開項であり、光ピックアップの収差測定としては一般にここまでの展開項数で十分である。この式を光束内の既知の異なる位置（ρ_m，θ_m）における収差測定値Ｗ_mを用いて係数Ａ_nに対する連立方程式として

And can be expanded. The first term on the right side is a constant phase offset, the second term is the tilt in the x direction, the third term is the tilt in the y direction, the fourth term is defocused, the fifth term is in the radial angle 0 ° or 90 ° direction Astigmatism, 6th term is astigmatism in radial angle 45 ° direction, 7th term is coma aberration in radial angle 0 ° direction, 8th term is coma aberration in radial angle 90 ° direction, 9th term Is a third-order spherical aberration, and _An is each aberration coefficient. These are the expansion terms up to the so-called third-order aberration, and the expansion terms up to here are generally sufficient for measuring the aberration of the optical pickup. The formula known different positions within the light beam (ρ _m, θ _m) as simultaneous equations for the coefficients A _n using an aberration measurement value W _m of

のように表すことができる。またこれを、行列を用いて示すと

It can be expressed as And this is shown using a matrix

と表される。したがってこの連立方程式はｎ＝ｍのときに、一意に未知数である収差係数を決めることができる。ｎ＞ｍのときは解が不定になり係数を決めることはできない。ｎ＜ｍのときは求める係数の数よりも収差の測定点数の方が多いので、連立方程式としては一般に解は不能であるが、誤差を含む式と解釈すれば最小２乗法などによって誤差を最小とする係数を決めることができる。したがってたとえば図４のような構造の回折格子を用いて光束を未知数９個に分割し、ｍ＝ｎ＝９として上記の連立方程式を解くことにより、３次の各収差係数を検出することができる。検出できる収差の展開項数は図５に示す回折格子のように分割数ｎを増やすことにより増やすことができる。

It is expressed. Therefore, this simultaneous equation can uniquely determine an unknown aberration coefficient when n = m. When n> m, the solution is indefinite and the coefficient cannot be determined. When n <m, the number of aberration measurement points is larger than the number of coefficients to be obtained, so it is generally impossible to solve as a simultaneous equation. However, if it is interpreted as an equation containing an error, the error is minimized by the least square method. Can be determined. Therefore, for example, by dividing the light beam into nine unknowns using a diffraction grating having a structure as shown in FIG. 4 and solving the above simultaneous equations with m = n = 9, each third-order aberration coefficient can be detected. . The number of aberration expansion terms that can be detected can be increased by increasing the number of divisions n as in the diffraction grating shown in FIG.

  The diffraction light from the diffraction grating 116 for aberration detection in FIG. 1 is a diffraction grating having a structure in which the intensity of the + 1st order light is equal to 0 as shown in FIG. If the 0th-order light is used to obtain a reproduction signal, the light emitted from the diffraction grating 116 for detecting aberration is received by a photodetector as shown in FIG. Zero order light for obtaining a reproduction signal is detected by photodetectors 141, 143, 137, and 139 without division on the photodetector. Signals that contribute to the reproduction signal are indicated by thick lines in FIG. On the other hand, −1st order light for aberration detection is detected by n-divided photodetectors 140, 142, 136, and 138. Signals contributing to aberration detection are indicated by thin lines in FIG. PD1 (0 °), PD2 (180 °), PD3 (90 °), and PD4 (270 °) in FIG. 7 are photodetectors that receive light having different phase differences described in FIG.

  First, the reproduction signal will be described. Light is received by the light detector 141 (PD1 (0 °)), the light detector 143 (PD2 (180 °)), the light detector 137 (PD3 (90 °)), and the light detector 139 (PD4 (270 °)). Of the received light, signals from the photo detector 141 (PD1 (0 °)) and the photo detector 143 (PD2 (180 °)) are sent to the differential amplifier 121, and the photo detector 137 (PD3 (90 °)) The signal of the photodetector 139 (PD4 (270 °)) is input to the differential amplifier 122, where differential amplification is performed, and signals Sig1_RFS and Sig2_RFS are output, respectively. The output Sig1_RFS and Sig2_RFS are then input to the reproduction signal arithmetic circuit 144. The reproduction signal calculation circuit 144 calculates the square of Sig1_RFS and the square of Sig2_RFS, calculates the sum of them, and obtains the reproduction signal (RFS) by taking the square root.

Next, signals for aberration detection will be described. Photodetector 140 (PD1 (0 °)), photodetector 142 (PD2 (180 °)), photodetector 136 (PD3 (90 °)), and photodetector 138 (PD4 (270 °)) Of the received light, the signal I _{PD1_n} from the photodetector 140 (PD1 (0 °)) and the signal I _{PD2_n} from the photodetector 142 (PD2 (180 °)) are _sent to the differential amplifier 121 to the photodetector 136 ( PD3 signals I _{PD4_n} from (90 °)) signals from I _{PD3_n} photodetector 138 (PD4 (270 °)) input to the differential amplifier 122, where performs differential amplification operation, signal Sig1_n, signal Sig2_n Are output respectively. This output signal is input to the phase difference calculation circuit 120, and the phase difference calculation circuit 120 calculates the phase difference.

  The output from the phase difference calculation circuit 120 is input to the aberration calculator 127. In the aberration calculator 127, first, the output from the phase difference calculation circuit 120 is converted into a wavelength, and the value is substituted into the Zernike orthogonal polynomial shown in the equation (1) to obtain n pieces of the equation (3). Solve simultaneous equations.

Since the solution of the simultaneous equations is a aberration coefficients A _n, and feedback to the aberration correcting means on the basis of those values. For example, based on Equation (1) A ₉ (3 order spherical aberration) in a spherical aberration can be corrected by controlling the beam expander 113, also, A ₇ (0 ° direction coma), A _The actuator 106 with a lens tilt mechanism is controlled based on ₈ (90 ° direction astigmatism), and based on A ₅ (0 ° or 90 ° direction astigmatism) and A ₆ (45 ° direction astigmatism). The liquid crystal element 117 is controlled. This makes it possible to correct spherical aberration, coma and astigmatism.

  Note that the phase value obtained by the calculation here is the phase difference between the signal light and the reference light. That is, in FIG. 1, the aberration generated in the optical system from the semiconductor laser to the polarization beam splitter 104 occurs in both the signal light and the reference light, but this cannot be detected. On the contrary, what can be detected is an aberration that is mixed after the signal light is separated from the reference light by the beam splitter, but this is caused by astigmatism caused by misalignment of the objective lens and disc substrate thickness deviation. Major aberrations such as spherical aberration are included. However, the coma due to the disk tilt is an odd function with respect to the origin, and is canceled by the round-trip optical path and cannot be detected.

  As described above, in the embodiment, the aberration coefficient is obtained by calculation and then used as a drive signal for the aberration correction element. However, it is not always essential to obtain the aberration coefficient. For example, if a region where the phase of the liquid crystal aberration correction element can be varied independently is divided so as to correspond to the divided region of the light flux as shown in the diffraction elements 131 and 153 in FIGS. The value can be used as it is as a drive signal for the divided region of the liquid crystal aberration correction element. In this case, an arithmetic circuit for the aberration coefficient is not necessary, and the cost of the optical disk apparatus using the present invention can be reduced.

  Although defocus and coma aberration can be detected by the focus error signal and tracking error signal, it is possible to correct defocus and coma aberration by controlling the two-dimensional actuator 106 in accordance with the result from the aberration calculator 127. It is. When performing aberration correction, there is a method in which correction is performed using the raw aberration value obtained from the aberration calculator 127, but in addition to a method using a reproduction signal, jitter, or the like as in the conventional aberration correction method. Correction may be performed.

  Next, calculation of the focus error signal and the tracking error signal will be described. Returning to FIG. 1, the light transmitted through the polarizing prism 125 is condensed by the condenser lens 133, is given astigmatism by the cylindrical lens 119, enters the quadrant photodetector 128, and is signal-calculated from the output signal. The circuit 129 outputs a focus error signal (FES) and a tracking error signal (TES). This calculation process is simply shown in FIG. Although details of the quadrant photodetector 128 are omitted in FIG. 1, the calculation method of the focus error signal FES and the tracking error signal TES is similar to the reproduction signal calculation method described above. In other words, quadrant photodetector (PD (N = 1) (0 °)), quadrant photodetector (PD (N = 2) (180 °)), quadrant photodetector (PD (N = 3)) (90 °)) The light received by the quadrant photodetector (PD (N = 4) (270 °)) is initially left of FIG. 8 with respect to the four signals from each quadrant photodetector. The focus error signal FES and the tracking error signal TES are calculated by adding and subtracting as shown in FIG.

  Thereafter, the FES1 and FES2 signals are input to the differential amplifier 134, the FES3 and FES4 signals are input to the differential amplifier 123, the TES1 and TES2 signals are input to the differential amplifier 124, and the TES3 and TES4 signals are input to the differential amplifier 126. Then, differential amplification operation is performed to obtain Sig1_FES from the differential amplifier 134, Sig2_FES from the differential amplifier 123, Sig1_TES from the differential amplifier 124, and Sig2_TES from the differential amplifier 126. After that, Sig1_FES and Sig2_FES are input to the signal arithmetic circuit 145, and Sig1_TES and Sig2_TES are input to the signal arithmetic circuit 146. The signal arithmetic circuit 145 calculates the square of Sig1_FES and the square of Sig2_FES, and then sums them. By taking the square root, the focus error signal FES is calculated, and the signal calculation circuit 146 calculates the square of Sig1_TES and the square of Sig2_TES, and after taking the sum thereof, the tracking error signal TES is obtained by taking the square root.

  The focus error signal FES is fed back to the focus drive terminal of the two-dimensional actuator 106 on which the objective lens 107 is mounted, and the focus position is controlled in a closed loop. Further, the same signal is fed back to the one-dimensional actuator 111 on which the corner cube prism 112 is mounted, and the corner cube prism 112 is also driven in conjunction with the objective lens 107. Thereby, the optical path difference between the signal light reflected from the optical disk 108 and the reference light reflected from the corner cube prism 112 can be kept substantially zero. Since the coherence length of a normal semiconductor laser is several tens of μm, the adjustment accuracy of the optical path difference only needs to be within this range. The tracking error signal TES is fed back to the tracking drive terminal of the two-dimensional actuator equipped with the objective lens 107, and is subjected to closed loop control.

  The present invention can be expected to be applied not only in the field of optical recording technology but also in a wide range of industries using optical elements.

1 is a schematic diagram showing an example of an optical disc apparatus according to the present invention. Explanatory drawing of a polarization phase conversion separation element. Explanatory drawing of a phase difference. Explanatory drawing of the diffraction grating and photodetector used for an aberration detection. Explanatory drawing of the diffraction grating and photodetector used for an aberration detection. FIG. 3 is a structural diagram of a diffraction grating used for aberration detection in the z direction. Explanatory drawing of a photodetector and an arithmetic circuit system. Explanatory drawing of a photodetector and an arithmetic circuit system.

Explanation of symbols

101: Semiconductor laser, 102: Collimating lens, 103: λ / 2 plate, 104: Polarizing prism, 105: λ / 4 plate, 106: Two-dimensional actuator, 107: Objective lens, 108: Optical disk, 109: Spindle motor, 110 : Λ / 4 plate, 111: one-dimensional actuator, 112: corner prism, 113: beam expander, 114: polarization phase conversion / separation element, 115: photodetector, 116: diffraction grating, 117: liquid crystal element, 118: collection Optical lens, 119: Cylindrical lens, 120: Phase difference calculation circuit, 121-124: Differential amplifier, 125: Polarizing prism (S-polarized reflectance 100%), 126: Differential amplifier, 127: Aberration calculator, 128: Light Detector: 129: signal operation circuit, 130: compensation element, 131: diffraction grating, 132: light detection 133: Condensing lens 134: Differential amplifier 135-143: Photo detector 144: Reproduction signal arithmetic circuit 145: Signal arithmetic circuit 146: Signal arithmetic circuit 147-150: Adder 151, 152 : Calculator, 153: diffraction grating, 154: photodetector, 201: polarization direction of signal light, 202: polarization direction of reference light, 203: non-polarization diffraction grating, 204: angle selective polarization conversion element, 205: polarization separation diffraction Grating, 206, 207: Optical axis

Claims (4)

A light source;
First splitting means for splitting the light emitted from the light source into first and second light fluxes;
Means for condensing and irradiating the first light flux on an optical information recording medium;
Aberration correcting means for correcting the aberration of the first luminous flux;
Means for reflecting the second light flux as reference light;
The signal light reflected from the optical information recording medium and the reference light are again guided to the first splitting unit to superimpose and interfere with the third light flux, and the signal included in each split light Second splitting means for making the phase relationship between the light and the reference light different from each other;
Detecting means for dividing each fourth light beam divided by the second dividing means into a plurality of mutually corresponding areas and detecting the light intensity as an electric signal for each area;
Calculating means for obtaining a phase difference between the signal light and the reference light in each corresponding region of the third light beam by using an electrical signal of each corresponding region of all the fourth light beams;
An optical disc apparatus comprising: a control unit that controls the aberration correction unit using a calculation result of the calculation unit.   2. The optical disc apparatus according to claim 1, wherein the aberration correction unit uses the calculation result of the phase difference of the third light beam corresponding to each divided region of the fourth light beam. An optical disc apparatus that corrects aberrations in a corresponding area.   The optical disk device according to claim 1, wherein the arithmetic means calculates the phase difference of the third light flux, and independently obtains spherical aberration, coma in two directions, and astigmatism in two directions, An optical disc apparatus characterized by controlling the control means in accordance with this value.   2. The optical disc apparatus according to claim 1, wherein the number of divisions detected by dividing the fourth light flux into regions is 9 or more.

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