JP2011165314A - Optical pickup head and information recording/ reproducing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical pickup head in which offset is not generated in a TE signal even during tracking with an objective lens when a two-layered disk is used. <P>SOLUTION: The optical pickup device includes a light source 1, a diffraction means 58 for generating a plurality of diffracted beams, a converging means for focusing the diffracted beams onto an optical storage medium, a beam branching means 52 for branching the plurality of beams 70a, 70b, and 70c reflected on the optical storage medium 41, and an optical detecting means 32 for outputting a signal corresponding to the amount of light of the received beams, and has a relationship: 10ηs≥ηm, wherein ηm denotes diffraction efficiency of 0-order diffracted light in the diffracted light generated by the diffraction means 58 and ηs denotes diffraction efficiency of the first or higher order diffracted light. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an optical pickup head and an information recording / reproducing apparatus used in an apparatus for recording, reproducing or erasing information on an optical storage medium.

  Optical memory technology using an optical storage medium having a pit-like pattern, which is a high-density and large-capacity storage medium, is expanding its application to digital audio disks, video disks, document file disks, and data files. In recent years, a high-density and large-capacity optical storage medium called a DVD has been put into practical use, and has been attracting attention as an information medium that can handle a large amount of information such as moving images. This DVD optical storage medium is recorded or reproduced using a so-called red semiconductor laser that emits laser light having a wavelength of around 650 nm.

  A conventional optical pickup head in an optical disc system capable of recording / reproducing will be described with reference to FIG.

A semiconductor laser light source 101 as a light source emits a linearly polarized divergent beam 700 having a wavelength λ ₂ of 650 nm. A divergent beam 700 emitted from the semiconductor laser light source 2 is incident on a diffraction grating 510 and separated into three beams of zero-order and ± first-order diffracted light. The 0th-order diffracted light is a main beam 700a for recording / reproducing information, and the ± 1st-order diffracted lights are sub-beams 700b and 700c, and a differential push-pull for stably detecting a tracking error (hereinafter referred to as TE) signal. (Hereinafter referred to as DPP) method. The ratio of the diffraction efficiency of the zero-order diffracted light and the one-order first-order diffracted light is usually set to 12: 1 to 20: 1, and here is 20: 1. By doing so, it is possible to prevent the sub beams 700b and 700c from affecting the main beam 700a and to avoid unnecessary recording on the optical storage medium 410.

  The three beams of the main beam 700a and the sub beams 700b and 700c generated by the diffraction grating 510 are transmitted through the polarization beam splitter 520 and converted into parallel light by the collimator lens 530 having a focal length of 15 mm. The parallel light passes through the quarter-wave plate 540 and is converted into circularly polarized light, and then converted into a convergent beam by the objective lens 560 having a focal length of 3 mm. The aperture of the objective lens 560 is limited by the aperture 550, and the numerical aperture NA is 0.6.

  The optical storage medium 410 includes a transparent substrate 410a and an information recording surface 410b, and the thickness of the transparent substrate 410a is 0.6 mm. The convergent beam from the objective lens 560 passes through the transparent substrate 410a and is condensed on the information recording surface 410b.

FIG. 23 is a diagram showing the relationship between tracks and beams on an optical storage medium. It is a figure explaining the relationship between the beam and track | truck on the information recording surface 410b. As shown in FIG. 23, the optical recording medium 410 is formed with the upper information recording surface and tracks that are a plurality of continuous grooves. The track T _m−1 , the track T _m , and the track T _{m + 1} are arranged in order, and the track pitch P that is the distance between the track T _m−1 and the track T _{m and} between the track T _m and the track T _{m + 1. 2} is 0.74 μm. When the main beam 700a is positioned on the track T _m, the sub-beams 700b, so as to be located between the respective 700c track T _m and the track T between the _m-1 and track T _m and T _{m + 1,} beam arrangement Has been. Therefore, the interval L ₂ between the main beam 700a and the sub beams 700b and 700c in the direction orthogonal to the track T _m is 0.37 μm.

  After the main beam 700a and the sub beams 700b and 700c collected on the information recording surface 410b are reflected and transmitted through the objective lens 560 and the quarter-wave plate 540 and converted into linearly polarized light different from the forward path by 90 degrees. Then, the light passes through the collimating lens 530 and is converted into convergent light. The convergent light is reflected by the polarization beam splitter 520, passes through the cylindrical lens 570, and enters the photodetector 31. Astigmatism is given to the main beam 700a and the sub beams 700b and 700c when passing through the cylindrical lens 570.

  The photodetector 300 includes eight light receiving units 300a, 300b, 300c, 300d, 300e, 300f, 300g, and 300h. The light receiving units 300a, 300b, 300c, and 300d receive the main beam 700a, the light receiving units 300e and 300f receive the sub beam 700b, and the light receiving units 300g and 300h receive the beam 700c, respectively. The light receiving units 300a, 300b, 300c, 300d, 300e, 300f, 300g, and 300h each output a current signal corresponding to the amount of light received.

  The focus error (hereinafter referred to as FE) signal by the astigmatism method, the TE signal by the phase difference method, the TE signal by the push-pull method, and the information (hereinafter referred to as RF) signal recorded on the optical storage medium are transmitted through the main beam 700a. It is obtained using each signal output from the light receiving units 300a, 300b, 300c, and 300d that receive light. In addition, when recording / reproducing a continuous groove disc such as a DVD-RW, signals output from the light receiving units 300e, 300f, 300g, and 300h that receive the sub beam 700b and the sub beam 700c are also used together, so that a TE signal by the DPP method can be generated. can get. The FE signal and TE signal are amplified and phase compensated to a desired level, and then supplied to actuators 910 and 920 for focus and tracking control.

  In DVD, in the case of a read-only ROM disk, a two-layer disk having two information surfaces is standardized. This read-only dual-layer disc can read information without any problem using a conventional optical pickup head by detecting the TE signal by the phase difference method.

  Furthermore, at the research and development level, the development results of a recordable double-layer disc having two information recording surfaces (hereinafter referred to as a double-layer recording disc) have been actively announced. In the recordable double-layer disc, information is not written in the initial stage, and therefore the TE signal cannot be detected by the phase difference method. Therefore, the TE signal is detected by the DPP method as in the case of a single-layer recordable disc.

  A conventional optical pickup head is disclosed in, for example, Patent Document 1 and the like.

JP 2002-190125 A

  However, even if the two-layer recording disk is used in the above-described conventional optical pickup head and the TE signal is detected by the DPP method, an offset that cannot be corrected is generated in the TE signal by tracking the objective lens. There is a problem.

  This is because when information is recorded / reproduced on one information recording surface of the two layers (hereinafter, the information recording surface at this time is referred to as a condensing surface), a part of the beam focused on the condensing surface is reflected. Then, part of the light passes through the condensing surface and reaches the other information recording surface (hereinafter, the information recording surface at this time is referred to as a non-condensing surface). The beam is defocused on the non-condensing surface and is reflected by the non-condensing surface and travels toward the photodetector. The beam reflected by the non-condensing surface cannot be completely canceled when detecting the TE signal by the DPP method due to aberrations, unevenness in the amount of light in the beam, and the like. Therefore, by tracking the objective lens, the amount that cannot be offset fluctuates, and an offset that cannot be corrected is generated in the TE signal.

  As a result, off-track occurs, and when information is recorded on the optical storage medium, a part of the information recorded on the adjacent track is erased, and the information recorded on the optical storage medium cannot be read faithfully. Occurs.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide an optical pickup head in which an offset does not occur in a TE signal even when an objective lens is tracking-tracked when a two-layer disk is used. A further object of the present invention is to provide an information recording / reproducing apparatus using such an optical pickup head.

An optical pickup head according to the present invention includes a light source that emits a light beam, a diffracting unit that generates a plurality of diffracted lights from the beam emitted from the light source, and a plurality of the diffracted lights from the diffracting unit as an optical storage medium. A converging means for condensing the light, a beam branching means for branching the plurality of beams reflected by the optical storage medium on the optical storage medium, and a beam branching means. Light detecting means for receiving the branched beam and outputting a signal corresponding to the amount of light of the received beam, the optical storage medium having a plurality of information recording surfaces, and at least one of the information recording surfaces Is formed with a guide groove, information is recorded on or between the guide grooves, and the diffracted light rate of the 0th-order diffracted light generated by the diffracting means is η _m. 1st or higher order of diffracted light The diffraction efficiency is η _s and the relationship of 10 · η _s ≧ η _m is established. As a result, even if a two-layer disk is used as the optical recording medium, the tracking error signal is not offset even if the objective lens is tracking-tracked.

  Further, another optical pickup head of the present invention includes a light source that emits a light beam, a diffractive unit that generates a plurality of diffracted lights from the beam emitted from the light source, and the plurality of diffracted lights from the diffractive unit. Converging means for condensing on the optical storage medium, beam branching means for branching the plurality of beams reflected on the optical storage medium by the plurality of diffracted lights collected on the optical storage medium, and A light detecting means for receiving the beam branched by the beam branching means and outputting a signal corresponding to the light quantity of the received beam, wherein the light detecting means is a part of the collected diffracted lights. A main beam light-receiving unit that receives 0th-order diffracted light and a sub-beam light-receiving unit that receives first-order or higher-order diffracted light, and the optical storage medium has a plurality of information recording surfaces, Has a guide groove The zero-order diffracted light collected by the converging means is reflected on the non-condensing surface among the plurality of information recording surfaces and is formed on the light detecting means. All the sub-beam light receiving portions are arranged during mapping. As a result, even if a two-layer disk is used as the optical recording medium, the tracking error signal is not offset even if the objective lens is tracking-tracked.

Further, another optical pickup head of the present invention includes a light source that emits a light beam, a diffractive unit that generates a plurality of diffracted lights from the beam emitted from the light source, and the plurality of diffracted lights from the diffractive unit. Converging means for condensing on the optical storage medium, beam branching means for branching the plurality of beams reflected on the optical storage medium by the plurality of diffracted lights collected on the optical storage medium, and A light detecting means for receiving the beam branched by the beam branching means and outputting a signal corresponding to the light quantity of the received beam, wherein the light detecting means is a part of the collected diffracted lights. A main beam light-receiving unit that receives 0th-order diffracted light and a sub-beam light-receiving unit that receives first-order or higher-order diffracted light, and the optical storage medium has a plurality of information recording surfaces, and at least one of the information recording surfaces Has a guide groove Are, the diffraction efficiency of 0-order diffracted light of said generated by the diffraction means and the diffracted light is eta _m, the diffraction efficiency of the first order or higher order diffracted light and eta _s, the optical storage medium of the converging means The numerical aperture on the side, NA, the lateral magnification of the optical system in the return path from the optical storage medium to the light detection means, α, the optical distance between the two information recording surfaces of the optical storage medium, d, Assuming that one area of the sub beam receiving portion is S _{1, there} is a relationship of S ₁ ≦ 4 · π · (d · NA · α) ² · η _s / η _m .

Further, another optical pickup head of the present invention includes a light source that emits a light beam, a diffractive unit that generates a plurality of diffracted lights from the beam emitted from the light source, and the plurality of diffracted lights from the diffractive unit. Converging means for condensing on the optical storage medium, beam branching means for branching the plurality of beams reflected on the optical storage medium by the plurality of diffracted lights collected on the optical storage medium, and A light detecting means for receiving the beam branched by the beam branching means and outputting a signal corresponding to the light quantity of the received beam, wherein the light detecting means is a part of the collected diffracted lights. A main beam light-receiving unit that receives 0th-order diffracted light and a sub-beam light-receiving unit that receives first-order or higher-order diffracted light, and the optical storage medium has a plurality of information recording surfaces, and at least one of the information recording surfaces Has a guide groove Are, the zero diffraction efficiency of diffracted light of said diffracted light generated by the diffraction means and eta _m, the diffraction efficiency of the first order or higher order diffracted light and eta _s, which is condensed by the converging means The effective reflectivity of the light collecting surface in the information recording surface where the beam is substantially focused is R _fo, and the effective reflection of the non-light collecting surface other than the light collecting surface in the plurality of information recording surfaces. The rate is R _dfo , the numerical aperture on the optical storage medium side of the converging means is NA, the lateral magnification of the return optical system from the optical storage medium to the light detection means is α, and 2 of the optical storage medium S ₁ ≦ 4 · π · (d · NA · α) ² · η _s / η _m · where d is the optical distance between the two information recording surfaces and S ₁ is the area of the sub beam receiving portion. R _fo / R _dfo relationship.

  Further, another optical pickup head of the present invention includes a light source that emits a light beam, a diffractive unit that generates a plurality of diffracted lights from the beam emitted from the light source, and the plurality of diffracted lights from the diffractive unit. Converging means for condensing on the optical storage medium, and beam branching means for branching the plurality of beams reflected by the plurality of diffracted lights collected on the optical storage medium into two. And astigmatism giving means for giving astigmatism to the first beam branched by the beam branching means, and beam division for further dividing the second beam branched by the beam branching means into two beams Means, a first light detection means for receiving a beam from the astigmatism means, and outputting a signal corresponding to the amount of light of the received beam, a beam from the beam splitting means, and the received beam The amount of light Second optical detection means for outputting the same signal, the optical storage medium has a plurality of information recording surfaces, at least one information recording surface is formed with a guide groove, and the beam splitting means is The second beam is divided in a direction parallel to the guide groove.

  The diffracting means generates 0th-order diffracted light and 1st-order diffracted light, and the first beam is composed of the 0th-order diffracted light and the 1st-order diffracted light, The first light detecting means may have four light receiving parts, and the zeroth order diffracted light and the first and higher order diffracted lights may be overlapped and received by the light receiving part.

  Each of the first light detection means and the second light detection means includes a light receiving unit that receives the plurality of the collected diffracted lights, and the 0th-order diffraction collected by the convergence means. During the mapping that the light reflected without focusing on the non-condensing surface of the plurality of information recording surfaces forms on the first light detecting means and the second light detecting means, All the light receiving portions of the one light detecting means and the second light detecting means may be arranged.

  Further, another optical pickup head of the present invention includes a light source that emits a light beam, a diffracting unit that generates 0th-order diffracted light and 1st-order or more diffracted light from the beam emitted from the light source, and the diffraction Converging means for condensing the 0th-order diffracted light from the means, the first-order or higher-order diffracted light on an optical storage medium, and the 0th-order diffracted light condensed on the optical storage medium; A beam splitting unit that splits the beam of the first-order or higher-order diffracted light reflected on the optical storage medium into two parts, and a beam split by the beam splitting unit are received, and the light quantity of the received beam A light detecting means for outputting a corresponding signal, wherein the light detecting means has a plurality of light receiving portions arranged in a line, and the optical storage medium has a plurality of information recording surfaces, and has at least one information recording surface. Guide grooves are formed on the two information recording surfaces, Over beam splitting means for splitting the beam as divided axis parallel to the axis substantially with the guide groove.

  In addition, the light receiving unit that receives the 0th-order diffracted light of one beam divided by the beam dividing unit is a light-receiving unit that receives the 0th-order diffracted light of the other beam divided by the beam dividing unit. And a light receiving unit that receives the first-order or higher-order diffracted light of the other beam divided by the beam splitting means.

  Further, the interval between the mappings formed on the light detection means by the zero-order diffracted light and the first-order or higher-order diffracted light of one of the beams divided by the beam splitting means is the beam splitting means. The two 0th-order diffracted lights divided in (1) may be wider than the interval between the maps formed on the light detection means.

  The beam splitting means may be a diffraction element.

  The beam splitting means may be a prism.

  Further, the beam may be focused at a substantially focal point on the light detection means.

  The size of the light receiving unit may be 3 to 10 times that of an Airy disk.

Further, another optical pickup head of the present invention includes a light source that emits a light beam, a diffractive unit that generates a plurality of diffracted lights from the beam emitted from the light source, and the plurality of diffracted lights from the diffractive unit. Converging means for condensing on the optical storage medium, beam branching means for branching the plurality of beams reflected on the optical storage medium by the plurality of diffracted lights collected on the optical storage medium, and Astigmatism applying means for applying astigmatism to the beam branched by the beam branching means, and receiving the beam provided with astigmatism by the astigmatism applying means, and according to the light quantity of the received beam A light detection means for outputting a signal, and the light detection means receives a main beam light receiving portion for receiving a 0th-order diffracted light among the collected diffracted lights and a first-order or higher-order diffracted light. Has a sub-beam detector The optical storage medium has a plurality of information recording surfaces, at least one of said information recording surfaces is formed with a guide groove, the astigmatism applied by the astigmatism providing means and Z _0, Of the diffracted light generated by the diffracting means, the diffraction efficiency of 0th-order diffracted light is η _m and the diffraction efficiency of 1st-order or higher diffracted light is η _s, and the beam condensed by the converging means is substantially focused. R _fo is the effective reflectivity of the condensing surface in the information recording surface connecting _Rdfo, and R _dfo is the effective reflectivity of the non-condensing surface other than the condensing surface in the plurality of information recording surfaces Where NA is the numerical aperture on the optical storage medium side of the convergence means, α is the lateral magnification of the optical system in the return path from the optical storage medium to the light detection means, and λ is the wavelength of the beam emitted by the light source. And d is the optical distance between the two information recording surfaces of the optical storage medium, When one area was _{S 1, S 1 · ηm ·} R dfo / (4 · π · d 2 · NA 2 · η s · R fo) ≦ α ≦ (Z 0/2 / Δz) 1/2 of And Δz is in the range of 3 to 10 times λ / 2 / NA ² .

Further, another optical pickup head of the present invention includes a light source that emits a light beam, a diffractive unit that generates a plurality of diffracted lights from the beam emitted from the light source, and the plurality of diffracted lights from the diffractive unit. A converging means for condensing on the optical storage medium and a beam reflected by the plurality of diffracted lights collected on the optical storage medium into two beams having different focal points. A beam splitting unit; and a light detection unit that receives the beam split by the beam splitting unit and outputs a signal corresponding to the amount of light of the received beam. A main beam light-receiving unit that receives 0th-order diffracted light and a sub-beam light-receiving unit that receives first-order or higher-order diffracted light; and the optical storage medium has a plurality of information recording surfaces, One before The information recording surface is formed with a guide groove, the beam two focal distance applied to the two beams divided by the dividing means and Z _0, of said generated by the diffraction means and the diffracted light The diffraction efficiency of the 0th-order diffracted light is η _m and the diffraction efficiency of the 1st-order or higher-order diffracted light is η _s. specific reflectance and R _fo, the effective reflectivity of the non-condensing surface other than the focus plane of the plurality of information recording surfaces as R _dfo, opening of the optical storage medium side of the converging means The number NA, the lateral magnification of the return optical system from the optical storage medium to the light detection means α, the wavelength of the beam emitted from the light source λ, and the two information recording surfaces of the optical storage medium the optical distance is d, when one area of the sub-beam light-receiving unit and the S _1, S ₁ · _{m · R dfo / (4 ·} π · d 2 · NA 2 · η s · R fo) ≦ α ≦ (Z 0/2 / Δz) has a ^1/2 relationship, and, Delta] z is lambda / 2 / The range is 3 to 10 times NA ² .

Further, another optical pickup head of the present invention includes a light source that emits a light beam, a diffractive unit that generates a plurality of diffracted lights from the beam emitted from the light source, and the plurality of diffracted lights from the diffractive unit. A converging means for condensing on the optical storage medium, and a beam dividing means for dividing the plurality of beams reflected by the plurality of diffracted lights collected on the optical storage medium into two. And a light detection means for receiving the beam divided by the beam splitting means and outputting a signal corresponding to the amount of light of the received beam, and an astigmatism in the beam in the optical path from the optical storage medium to the light detection means. An astigmatism applying unit that applies aberration, and the light detecting unit includes a main beam light receiving unit that receives 0th-order diffracted light among the collected diffracted light and first-order or higher-order diffracted light. Receiving subby The optical storage medium includes a substrate having a refractive index n and a plurality of information recording surfaces, and at least one information recording surface is formed with a guide groove, and the astigmatism applying unit Z ₀ is the astigmatic difference given by, the diffraction efficiency of the 0th-order diffracted light of the diffracted light generated by the diffracting means is η _m, and the diffraction efficiency of the 1st-order or higher diffracted light is η _s , The effective reflectance of the light condensing surface in the information recording surface where the beam condensed by the converging means is substantially focused is R _fo, and the non-light condensing surface other than the light condensing surface in the plurality of information recording surfaces. R _dfo is the effective reflectivity of the condensing surface, NA is the numerical aperture on the optical storage medium side of the convergence means, and α is the lateral magnification of the optical system in the return path from the optical storage medium to the light detection means. The wavelength of the beam emitted from the light source is λ, and the optical distance between the two information recording surfaces of the optical storage medium and d, when said one area of the sub-beam light-receiving unit and the _{S 1, S 1 · η m} · R dfo / (4 · π · d 2 · NA 2 · η s · R fo) ≦ α ≦ (Z 0 N ³ / Δt / (n ² −1) / NA ² ) ^1/2 and Δt is in the range of 5 to 30 times λ / NA ⁴ .

Further, another optical pickup head of the present invention includes a light source that emits a light beam, a diffractive unit that generates a plurality of diffracted lights from the beam emitted from the light source, and the plurality of diffracted lights from the diffractive unit. A converging means for condensing on the optical storage medium, and a first beam splitting means for dividing the beam reflected by the plurality of diffracted lights condensed on the optical storage medium into two. And a light detection means for receiving the beam divided by the first beam splitting means and outputting a signal corresponding to the amount of light of the received beam, and a beam in an optical path from the optical storage medium to the light detection means. A second beam splitting unit that splits the beam into two beams having different focal points, and the photodetecting unit receives a 0th-order diffracted light among the collected diffracted light and 1 More than The optical storage medium has a substrate having a refractive index n and a plurality of information recording surfaces, and at least one information recording surface has a guide groove formed thereon; Two focal intervals given to the two beams divided by the second beam splitting means are Z _0, and the diffraction efficiency of the 0th-order diffracted light among the diffracted lights generated by the diffracting means is η _m , The diffraction efficiency of first-order or higher-order diffracted light is η _s, and the effective reflectivity of the condensing surface of the information recording surface where the beam condensed by the converging means is substantially focused is R _fo R _dfo is an effective reflectance of a non-light-condensing surface other than the light-condensing surface, and NA is a numerical aperture on the side of the optical storage medium of the converging means. The lateral magnification of the optical system in the return path to the light detection means is α, and the wave of the beam emitted from the light source Was a lambda, the optical distance between the two information recording surface of the optical storage medium is d, when one area of the sub-beam light-receiving unit and the _{S 1, S 1 · η m} · R dfo / (4 · π · d ² · NA ² · η _s · R _fo ) ≦ α ≦ (Z ₀ · n ³ / Δt / (n ² −1) / NA ² ) ^1/2 and Δt is λ The range is 5 to 30 times greater than / NA4.

  Further, another optical pickup head of the present invention includes a semiconductor laser light source that emits a light beam, a diffractive means that generates a plurality of diffracted lights from the beam emitted from the semiconductor laser light source, and the plurality of the diffractive means from the diffractive means. Focusing means for focusing the diffracted light on the optical storage medium, and beam branching for branching the plurality of beams reflected on the optical storage medium by the plurality of diffracted lights collected on the optical storage medium And a light detection means for receiving a beam branched by the beam branching means and outputting a signal corresponding to the light quantity of the received beam, the optical storage medium having a plurality of information recording surfaces A guide groove is formed on at least one of the information recording surfaces, and the semiconductor laser light source is formed on a substrate disposed so as to be substantially parallel to the guide grooves formed on the information recording surface. , Les It emits spontaneous emission light from a position different from the position for emitting Zabimu.

  The substrate of the semiconductor laser light source may be made of sapphire.

  The substrate of the semiconductor laser light source may be made of gallium nitride.

Further, another optical pickup head of the present invention includes a light source that emits a light beam, a diffractive unit that generates a plurality of diffracted lights from the beam emitted from the light source, and the plurality of diffracted lights from the diffractive unit. And a converging means for condensing on the optical storage medium, and receiving the beam reflected by the plurality of diffracted lights collected on the optical storage medium on the optical storage medium, Light detecting means for outputting a signal corresponding to the light detecting means, the light detecting means receiving two main beam light receiving portions for receiving zero-order diffracted light among the collected diffracted lights and first-order or higher-order diffraction. There are four sub-beam light-receiving units that receive light, signals output from the main beam light-receiving unit are T ₁ and T _2, and signals output from the sub-beam light-receiving units are T ₃ , T ₄ , T ₅ , T _6. (T ₁ −T ₂ ) / (T ₁ The tracking error signal is detected by calculating + T ₂ ) −k [{(T ₃ −T ₄ ) + (T ₅ + T ₆ )} / (T ₁ + T ₂ )] (k is a constant).

Further, another optical pickup head of the present invention includes a light source that emits a light beam, a diffractive unit that generates a plurality of diffracted lights from the beam emitted from the light source, and the plurality of diffracted lights from the diffractive unit. Converging means for condensing on the optical storage medium, beam branching means for branching the plurality of beams reflected on the optical storage medium by the plurality of diffracted lights collected on the optical storage medium, and Light detecting means for receiving the beam branched by the beam branching means and outputting a signal corresponding to the light amount of the received beam, the light detecting means having two light receiving portions, and the optical storage medium Has a first information recording surface and a second information recording surface, a guide groove is formed in the first information recording surface, and the diffracted light condensed by the converging means is the first information recording surface. Focus on the information recording surface and focus on the second information recording surface. If you do not have a, the first information beam reflected by the recording surface is received by the light detecting means, a signal output from the two light receiving portions, and T _f1, T _f2, the first The beams reflected by the information recording surface 2 are received by the light detection means, and the signals output from the two light receiving sections are T _s1 and T _s2, and (T _f1 + T _s1 −T _f2 −T _s2). ) / (T _f1 + T _s1 + T _f2 + T _s2 ), a tracking error signal is detected, and a relationship of T _f1 + T _f2 ≧ 5 · (T _s1 + T _s2 ) is established.

  Further, a condensing means for converging a beam received by the light detecting means is provided in an optical path from the optical storage medium to the light detecting means, and the condensing means has a convex lens and a concave lens. It is good.

  The information recording / reproducing apparatus of the present invention receives the optical pickup head, a drive unit that changes a relative position between the optical storage medium and the optical pickup head, and a signal output from the optical pickup head. And an electric signal processing unit for obtaining desired information.

  According to the optical pickup head of the present invention, when a multi-layer disc having two or more layers is recorded and reproduced, there is an effect that no offset is generated in the TE signal even if the objective lens is tracking-tracked.

  Further, according to the information recording / reproducing apparatus of the present invention, when recording and reproducing a multi-layer disc having two or more layers, an information recording / reproducing apparatus in which no offset occurs in the TE signal even when the objective lens is tracking-tracked can be realized. It has the effect.

The figure which shows the structure of the optical pick-up head concerning Embodiment 1 of this invention. The figure which shows the relationship between the track | truck and beam on the optical storage medium in the optical pick-up head of this invention The figure which shows the relationship between the photodetector of the optical pick-up head concerning Embodiment 1 of this invention, and a beam. The figure which shows the relationship between the lateral magnification and light quantity ratio in the optical pick-up head concerning Embodiment 1 of this invention. The perspective view which shows the structure of the light source in the optical pick-up head concerning Embodiment 2 of this invention. FIG. 6A is a diagram illustrating a relationship between a photodetector and a beam constituting the optical pickup head according to the second embodiment of the present invention, and FIG. 6A is a diagram when the objective lens is not in a neutral position; FIG. 6B is a view when the objective lens is in a neutral position, and FIG. 6C is a view when the objective lens is displaced in the opposite direction to FIG. The figure which shows the structure of the optical pick-up head concerning Embodiment 3 of this invention. FIG. 8A is a diagram showing a relationship between a photodetector and a beam constituting an optical pickup head according to a third embodiment of the present invention, and FIG. 8A shows a photodetector on which a beam whose optical path is bent by 90 degrees is incident. FIG. 8B is a diagram showing a photodetector on which a straight beam enters. FIG. 6 is a perspective view showing a configuration of a prism that constitutes an optical pickup head according to a third embodiment of the present invention. FIG. 6 is a diagram showing a configuration of an optical pickup head according to a fourth embodiment of the present invention. Configuration diagram of a diffraction grating constituting an optical pickup head according to a fourth embodiment of the present invention. The figure which shows the relationship between the photodetector and beam which comprise the optical pick-up head concerning Embodiment 4 of this invention. FIG. 6 is a diagram showing a configuration of a prism that constitutes an optical pickup head according to a fifth embodiment of the present invention. Configuration diagram of a diffraction grating constituting an optical pickup head according to a sixth embodiment of the present invention. The figure which shows the relationship between the photodetector and beam which comprise the optical pick-up head concerning Embodiment 6 of this invention. Configuration diagram of diffraction grating constituting optical pickup head according to Embodiment 7 of the present invention The figure which shows the relationship between the photodetector and beam which comprise the optical pick-up head concerning Embodiment 7 of this invention. The figure which shows the structure of the optical pick-up head concerning Embodiment 8 of this invention. The figure which shows the structure of the hologram element which comprises the optical pick-up head concerning Embodiment 8 of this invention. The figure which shows the relationship between the photodetector which comprises the optical pick-up head concerning Embodiment 8 of this invention, and a beam. The figure which shows the structure of the information recording / reproducing apparatus concerning Embodiment 9 of this invention. The figure which shows the structure of the conventional optical pick-up head The figure which shows the relationship between the track | truck and beam on the optical storage medium in the conventional optical pick-up head

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In the drawings, the same reference numeral represents the same component or the same function and operation.

(Embodiment 1)
FIG. 1 is a diagram showing a configuration of an optical pickup head according to Embodiment 1 of the present invention.

A semiconductor laser light source 1 as a light source emits a linearly polarized divergent beam 70 having a wavelength λ ₁ of 405 nm. A divergent beam 70 emitted from the semiconductor laser light source 1 is converted into parallel light by a collimator lens 53 having a focal length f ₁ of 15 mm, and then incident on a diffraction grating 58. The divergent beam 70 includes zero-order diffracted light and ± first-order diffracted light. Separated into beams. The 0th order diffracted light is a main beam 70a for recording / reproducing information, and the ± 1st order diffracted light is subbeams 70b and 70c. The subbeams 70b and 70c are used in the DPP method for stably detecting the TE signal. It is done. The ratio of the diffraction efficiency of the zero-order diffracted light and the one-order first-order diffracted light is usually set to 12: 1 to 20: 1, and here is 20: 1. By doing so, it is possible to prevent the sub beams 70b and 70c from affecting the main beam 70a, and to avoid unnecessary recording.

The main beam 70a and the sub beams 70b and 70c generated by the diffraction grating 58 pass through the polarization beam splitter 52, pass through the quarter-wave plate 54 and converted into circularly polarized light, and then the focal length. f ₂ is converted into a convergent beam by the objective lens 56 of 2.1 mm and focused on the optical storage medium 41.

The aperture of the objective lens 56 is limited by the aperture 55, and the numerical aperture NA is 0.85. The optical storage medium 41 includes a transparent substrate 41a, two information recording surfaces, a first recording layer 41b and a second recording layer 41c. The interval α ₁ between the first recording layer 41b and the second recording layer 41c is 20 μm, the thickness of the transparent substrate 41a is 0.1 mm, and between the transparent substrate 41a and the first recording layer 41b and the first recording layer. The refractive index n of the intermediate layer located between the layer 41b and the second recording layer 41c is 1.6. Specifically, the convergent beam focused on the optical storage medium 41 passes through the transparent substrate 41a and is focused on the first recording layer 41b.

FIG. 2 shows the relationship between tracks and beams on the first recording layer 41 b of the optical storage medium 41. Each of the first recording layer 41b and the second recording layer 41c has a track composed of continuous grooves, and information is recorded on the grooves. A plurality of tracks T _n are periodically installed, and the track pitch p _1, which is the interval between each track T _n and the track T _{n−1 and} the interval between the track T _n track T _{n and the} track T _{n + 1,} is 0. 32 μm. When the main beam 70a is located on the track, the sub beams 70b and 70c are arranged so as to be located between the tracks. Therefore, the interval L between the main beam 70a and the sub beams 70b and 70c in the direction orthogonal to the track T _n is 0.16 μm.

The main beam 70a and the sub beams 70b and 70c reflected by the first recording layer 41b pass through the objective lens 56 and the quarter-wave plate 54 and are converted into linearly polarized light different from the forward path by 90 degrees, and then the polarized beam. Reflected by the splitter 52. The main beam 70 a and the sub beams 70 b and 70 c reflected by the polarization beam splitter 52 are incident on the photodetector 31 through the detection lens 59 and the cylindrical lens 57 having a focal length f ₃ of 30 mm. Astigmatism is given to the main beam 70a and the sub beams 70b and 70c when passing through the cylindrical lens 57.

FIG. 3 is a diagram schematically illustrating a relationship among the photodetector 31, the main beam 70a, and the sub beams 70b and 70c. The photodetector 31 has eight light receiving portions 31a, 31b, 31c, 31d, 31e, 31f, 31g, and 31h, and each light receiving portion 31a, 31b, 31c, 31d, 31e, 31f, 31g, and 31h receives light. Current signals I _31a , I _31b , I _31c , I _31d , I _31e , I _31f , I _31g , and I _31h corresponding to the respective light _amounts are output.

The light receiving units 31a, 31b, 31c, and 31d receive the main beam 70a, the light receiving units 31e and 31f receive the sub beam 70b, and the light receiving units 31g and 31h receive the sub beam 70c, respectively. The sizes of the light receiving portions 31a, 31b, 31c, and 31d are 60 μm × 60 μm, respectively. The size of the light receiving portions 31e, 31f, 31 g, 31h, each width W ₁ is 120 [mu] m, vertical width W ₂ is 60 [mu] m. Accordingly, the total sum of the sizes of the light receiving portions that receive the main beam 70a and the sub beams 70b and 70c is 120 μm × 120 μm.

  Each of the main beam 70a and the sub beams 70b and 70c is a beam reflected by the first recording layer 41b of the optical storage medium, and astigmatism is given by the cylindrical lens 57, but on the photodetector 32. The minimum circle of confusion is 60 μm in diameter. Therefore, the combined focal length combining the detection lens 59 and the cylindrical lens 57 is 30 mm and 29.05 mm.

In addition, when information is recorded / reproduced with respect to the first recording layer 41b (condensing surface) of the optical storage medium 41, a part of the beam focused on the first recording layer 41b is reflected and a part of the first recording layer 41b is recorded in the first recording layer. It reaches the second recording layer 41c (non-condensing surface) through the layer 41b and reaches the defocused beam, and is reflected by the second recording layer 41c. Beams 71 a, 71 b, 71 c shown in FIG. 3 are beams reflected by the second recording layer 41 c (non-condensing surface), and are largely defocused on the photodetector 31. The radius r of each beam 71a, 71b, 71c on the photodetector 31 is approximately given by r≈2 · d · NA · α. d is the distance between the optical reflecting surfaces of the optical storage medium, d = d ₁ / n, α is the lateral magnification of the optical system from the optical storage medium to the photodetector, and is given by α = f ₃ / f ₂ It is done. In the first embodiment, since d ₁ = 20 μm, n = 1.60, NA = 0.85, f ₂ = 2.1 mm, and f ₃ = 30 mm, r≈300 μm.

  The beam 71a has a radius of about 300 μm on the photodetector 31, and the light receiving portions 31e, 31f, 31g, and 31h of the photodetector 31 are arranged so as to be positioned therein. With this arrangement, even if the beam reflected by the non-condensing surface on the photodetector 31 moves due to the movement of the objective lens 56 during tracking tracking, the light receiving portions 31e, 31f, 31g, and 31h. The amount of light of the beam 71a received by the laser beam hardly changes, and as a result, no offset occurs in the TE signal.

The FE signal is obtained by the astigmatism method using the signals I _31a , I _31b , I _31c , and I _31d output from the photodetector 31, that is, (I _31a + I _31c ) − (I _31b + I _31d ). Obtained by calculation. The TE signal is obtained by the DPP method, that is, by the calculation of {(I _31a + I _31d ) − (I _31b + I _31c )} − K · {(I _31e + I _31g ) − (I _31f + I _31h )}. . Here, K is a coefficient determined by the ratio of the diffraction efficiency of the 0th-order diffracted light and the diffraction efficiency of the 1st-order diffracted light of the diffraction grating 58.

  The FE signal and the TE signal are amplified and phase-compensated to a desired level, and then supplied to actuators 91 and 92 for moving the objective lens 56 for focus and tracking control.

FIG. 4 shows sub-beams incident on the light receiving unit 31e and the light receiving unit 31f when the lateral magnification α of the optical system is changed by changing the focal length f ₃ of the detection lens 59 under the optical conditions in the first embodiment. The relationship between the light quantity I _{70b of 70b} and the light quantity I _71a (hereinafter referred to as stray light) of the beam 71a reflected by the second recording layer (non-condensing surface) 41c in the main beam 70a is shown. This relationship is the same for the light quantity I _70c and the stray light quantity I _71a of the light receiving part 31g and the light receiving part 31h to which the sub beam 70c is incident. Increasing α decreases the amount of stray light I _71a , and decreasing α decreases the amount of stray light I _71a . When α is 10 times, the light _amounts of I _71a and I _70b are equal, and in the first embodiment, the lateral magnification α is set to 10 times. When the value of the stray light amount I _71a is large, it causes the offset fluctuation of the TE signal. Therefore, it is desirable to reduce the stray light amount I _71a by increasing the lateral magnification α. Substantially, if the stray light amount I _71a is equal to or less than the sub-beam light amount I _70b , there is almost no offset in the TE signal even when tracking is followed or when the optical storage medium is tilted.

Ideally, the DPP method cancels the stray light component by performing a differential operation, so an offset should not occur. However, in reality, it completely cancels out due to aberrations and unevenness in the amount of light in the beam. It may not be able to be exhausted. In consideration of realistic aberration and unevenness in the amount of light, if the stray light amount I _71a is equal to or less than the sub-beam light amount I _70b , the remaining offset amount is a few percent of the light amount incident on the light receiving unit, The amount of off-track caused by the offset is so small that it can be ignored. When the stray light amount I _71a is equal to the sub beam light amount I _70b , the area S ₁ of the light receiving portion 31e and the light receiving portion 31f that receives the sub beam 70b is approximately 4 · π · (d · NA · α) ² · η _s / equal to eta _m, the amount of stray light I71a to the amount of less than the sub-beam light amount I70b is one sub-beam 70b light receiving portions 31e and 31f area S ₁ of the receiving (or 70c) 4 · π · (d · NA · α) The area may be ² · η _s / η _m or less. Here, η _m is the diffraction efficiency of the main beam 70 a of the diffraction grating 58, and η _s is the diffraction efficiency of one sub beam 70 b of the diffraction grating 58. Therefore, the information recording / reproducing apparatus using the optical pickup according to the first embodiment can be recorded on an optical storage medium without erasing information recorded on an adjacent track even when a recordable double-layer disc is used as the medium. The recorded information can be read faithfully.

The beam 70a, 70b, and the effective reflectance R _fo of the first recording layer 41b 70c is a surface to be condensed, the second recording layer 41c of the beam 70a, 70b, 70c are reflected defocused When the effective reflectivity R _dfo of the light receiving portion ₃₂ is different, the area S ₁ of the light receiving portion 32e and the light receiving portion 32f is set to 4 · π · (d · NA · α) ² · η _s / η _m · R _fo / R _dfo If the area is as follows, the same effect can be obtained. Here, the reflectance R _41b of the first recording layer 41b, the transmittance T _41b, when the reflectance of the second recording layer 41c was R _41c, the effective reflectivity R _fo of the first recording layer 41b is , R41b, effective reflectivity R _dfo the second recording layer 41c is a _{T 41b · T 41b · R 41c} .

Further, by configuring the detection lens 59 by combining a convex lens and a concave lens, the optically equivalent focal length is long and the physical distance can be shortened. Even if the focal length f ₃ is increased, The optical pickup head does not become large. Thereby, a small optical pickup head with less offset can be realized.

  Although the first recording layer 41b is described as a condensing surface and the second recording layer 41c is described as a non-condensing surface, the second recording layer 41c is collected when information is recorded on and reproduced from the second recording layer 41c. The same effect as described above can be obtained only by the light surface and the first recording layer 41b being a non-condensing surface.

Further, when the optical storage medium 41 is a type in which information is recorded only on one of the grooves or between the grooves, when recording or erasing information, the main beam is positioned on the track. Since it is located not between tracks but between tracks, it is difficult to erase information recorded on tracks. Therefore, at this time, there is no problem even if the diffraction efficiency ratio is 10: 1. When the area S ₁ of the light receiving portion that receives one of the beams 70b or 70c is 4 · π · (d · NA · α) ² · η _s / η _m or less, when the light quantity of the sub beam 70b or 70c increases, Accordingly, the lateral magnification α of the optical system can be reduced. If the focal length f ₂ of the objective lens 56 is constant, the lateral magnification α can be reduced, so that the focal length f ₃ of the detection lens 59 can be reduced, and the size of the optical pickup head is reduced accordingly. A small information recording / reproducing apparatus can be provided. Further, when the lateral magnification α of the optical system is the same, the influence of stray light is reduced by the amount of light of the sub beam 70b or 70c, so that an optical pickup head capable of more stable tracking control is obtained.

  In addition, the optical pickup head of the present invention does not depart from the spirit, such as changing the focus detection method from the astigmatism method to the spot size detection method, or using a prism that shapes the beam in order to increase the light utilization efficiency. Various modifications can be made within the range, and there is no limitation on the wavelength of the light source and the NA of the objective lens, and it can be applied to various optical conditions.

(Embodiment 2)
The configuration of the optical pickup device according to the second embodiment of the present invention is different from the configuration and arrangement of the semiconductor laser light source in the optical pickup device of the first embodiment. Other configurations are the same as those of the optical pickup of the first embodiment. It is the same.

  In the second embodiment, a semiconductor laser that emits a beam having a wavelength of 450 nm or less is used as a light source. In such a case, a substrate constituting the light source and a track on the optical storage medium are optically parallel. It is preferable to arrange.

  Materials used to construct lasers that emit laser beams with a wavelength of 450 nm or less, such as gallium nitride and zinc selenide, have many lattice defects, and current and light are confined in the active layer due to the self-compensation effect. It becomes weak and it is easy to emit spontaneously emitted light from a place other than the light emitting point, and this spontaneously emitted light may cause offset fluctuation due to tracking tracking.

  FIG. 5 is a perspective view showing the configuration of the semiconductor laser light source in the second embodiment. A laser beam is emitted from the light emitting point 10 from the semiconductor laser light source 2 that emits the beam constituting the optical pickup head. Further, as shown in FIG. 5, in addition to the laser beam, a beam 75 which is amplified spontaneous emission light is emitted from the active layer 11 made of gallium nitride. The beam 75 is also collected and reflected on the information recording surface of the optical storage medium 41 and then enters the photodetector 31. Although not shown, the semiconductor laser light source 2 is arranged so that the substrate 12 is optically parallel to the track of the optical storage medium.

  FIG. 6 is a diagram showing the relationship between the photodetector 31 and the main beam 70a, the sub beams 70b and 70c, and the beam 75 in the second embodiment, and FIG. 6B shows the case where the objective lens 56 is in the neutral position. FIGS. 6A and 6C show the case where the objective lens 56 is not in the neutral position, and FIGS. 6A and 6C show that the moving directions of the objective lens 56 are opposite to each other.

  The beam 75 reflected by the information recording surface of the optical storage medium 41 is also incident on the photodetector 31, but the substrate 12 constituting the light source and the track on the optical storage medium are arranged optically in parallel. Therefore, as shown in FIG. 6, the beam 75 is greatly expanded and incident in the direction in which the light receiving portions 31a, 31b, 31c, 31d, 31e, 31f, 31g, and 31h are arranged. Accordingly, when the position of the objective lens 56 moves due to tracking tracking, even if the positions of the main beam 70a, the sub-beams 70b and 70c, and the beam 75 move with respect to the photodetector 32, the beam 75 moves to the photodetector 31. There is almost no change in the amount of light incident on the light receiving portions 31a, 31b, 31c, 31d, 31e, 31f, 31g, and 31h. Therefore, an optical pickup head capable of a stable tracking operation with no offset variation is obtained.

  In the second embodiment, the configuration of the optical pickup head that detects the TE signal using the three beams of the main beam 70a and the sub beams 70b and 70c has been described. However, for example, the push-pull method using one beam is used. Even with a device that detects a TE signal, the same effect can be obtained with the same configuration. The same effect can be obtained when the optical storage medium has only one information recording surface.

  Here, although sapphire is used for the substrate 12 constituting the semiconductor laser light source 2 and gallium nitride is used for the active layer, gallium nitride is used for the substrate 12 and gallium nitride with indium added to the active layer is used. Similar effects can be obtained by using a semiconductor laser made of gallium nitride, which easily generates spontaneous emission light, or a semiconductor laser light source 2 made of a group 2 and 6 compound semiconductor such as zinc selenide.

  If the substrate 12 constituting the semiconductor laser light source 2 is disposed optically in parallel with the track of the optical storage medium, the above-described effects can be obtained in the same manner, and the optical configuration of the optical pickup head is not limited. .

(Embodiment 3)
The configuration of the optical pickup head according to the third embodiment of the present invention will be described with reference to FIG.

  A beam 70 having a wavelength of 405 nm emitted from the semiconductor laser light source 1 is condensed on the optical storage medium 41 by the objective lens 56 via the collimating lens 53, the diffraction grating 58, the composite beam shaping prism 4, and the rising mirror 5. The On the optical storage medium 41, a main beam 70a, a sub beam 70b, and a sub beam 70c corresponding to recording / reproduction are condensed. The main beam 70 a and the sub beams 70 b and 70 c reflected by the optical storage medium 41 are changed in optical path by the composite beam shaping prism 4 and incident on the beam splitter 16 through the detection lens 59.

  The beam splitter 16 separates the incident main beam 70a and sub beams 70b and 70c into two. One of the beams separated by the beam splitter 16 travels straight through the beam splitter 16, and astigmatism is given through the cylindrical lens 18 and enters the photodetector 32 as in the conventional optical pickup device. . The other beam separated by the beam splitter 16 is a hologram element 17 whose optical path is bent by approximately 90 degrees and has two blazed regions for generating a push-pull signal. The beam is split in a direction parallel to, and enters the photodetector 33.

  As an element for splitting the beam for generating the push-pull signal into two, the roof prism 22 shown in FIG. 9 may be used in place of the hologram element 17, and a DPP signal can be obtained. .

FIG. 8 is a diagram illustrating the relationship between the photodetector and the beam according to the third embodiment. FIG. 8A shows the relationship between the photodetector 32 on which a straight beam enters and the beam. The photodetector 32 for detecting the FE signal has four light receiving portions 32a, 32b, 32c, and 32d, and outputs output signals F ₁ , F ₂ , F ₃ , and F ₄ according to the amount of light incident thereon. To do. Based on these output signals F ₁ , F ₂ , F ₃ and F ₄ , an FE signal can be obtained by the astigmatism method. Specifically, the FE signal is obtained by calculating as in Expression 1.

FE signal = (F ₁ + F ₃ ) − (F ₂ + F ₄ ) (Formula 1)
FIG. 8B shows the relationship between the beam and the photodetector 33 on which the beam whose optical path is bent 90 degrees is incident. The TE signal detection photodetector 33 has six light receiving portions 33a, 33b, 33c, 33d, 33e, and 33f. The light-receiving unit 33a and the light-receiving unit 33b are a main beam light-receiving unit 34a that receives the main beam 70a as a set, and the light-receiving unit 33c and the light-receiving unit 33d are a set that receives the sub-beam 70b as a set. The light receiving unit 33e and the light receiving unit 33f are a sub beam light receiving unit 34c that receives the sub beam 70c as a pair.

  Further, a dummy light receiving part 34g is installed between the main beam light receiving part 34a and the sub beam light receiving part 34b, and a dummy light receiving part is provided between the main beam light receiving part 34a and the sub beam light receiving part 34c. The part 34h is installed.

  In general, between each light receiving part of the photodetector, current leaked from the received light leaks, that is, crosstalk occurs between the light receiving part and the light receiving part. In particular, in the case of the tracking method using the DPP method, the crosstalk from the light receiving unit for the main beam having a large light amount to the light receiving unit for the sub beam having a small light amount cannot be ignored. Since the dummy light receiving portions 34g and 34h are provided, the leakage current from the main beam light receiving portion 34a flows into the dummy light receiving portions 34g and 34h and does not enter the sub beam light receiving portions 34b and 34c. Although not shown, the dummy light receiving unit 34g and the dummy light receiving unit 34h are connected to an appropriate potential. Thereby, the current mixed in the dummy light receiving part 34g and the dummy light receiving part 34h from the main beam light receiving part 34a does not flow again to the sub beam light receiving parts 34b and 34c. Accordingly, it is possible to reduce crosstalk between the main beam light receiving unit 34a and the sub beam light receiving units 34b and 34c, and the main beam 70a and the sub beam 70b or 70c are optically and electrically connected to each other in the photodetector 34. In addition, high isolation can be maintained. For this reason, the ratio of the light quantity of the main beam 70a mixed in the sub-beam light receiving portions 34b and 34c is small.

The light receiving sections 33a, 33b, 33c, 33d, 33e, and 33f output output signals T ₁ , T ₂ , T ₃ , T ₄ , T ₅ , and T ₆ according to the amount of light incident on them. Based on these output signals, the TE signal can be obtained by the DPP method. More specifically, the TE signal is obtained by calculating as in Expression 2. (K is a constant)
TE signal = (T ₁ −T ₂ ) −k {(T ₃ −T ₄ ) + (T ₅ −T ₆ )} (Formula 2)
However, since the signal amplitude of the TE signal changes due to a change in the reflectance of the optical storage medium, etc., in order to keep the tracking control gain constant even if the reflectance of the optical storage medium changes in practice, It is common to provide an automatic gain control (hereinafter referred to as AGC) circuit that divides by the total light quantity signal of the TE signal. That is, the push-pull signal obtained from the main beam 70a is divided by the sum signal of the signals T1 and T2 output from the light receiving unit 33a and the light receiving unit 33b that receive the main beam 70a, and the push-pull obtained from the sub beam 70b and the sub beam 70c. It is desirable to obtain a TE signal by dividing the signal by the sum signal of signals T3, T4, T5, and T6 output from the light receiving unit 33c, the light receiving unit 33d, the light receiving unit 33e, and the light receiving unit 33f that receive the sub beam. Specifically, it is desirable to obtain the TE signal by the calculation shown in Equation 3.

TE signal = (T ₁ −T ₂ ) / (T ₁ + T ₂ ) −k [{(T ₃ −T ₄ ) + (T ₅ + T ₆ )} / (T ₃ + T ₄ + T ₅ + T ₆ )] 3)
However, in consideration of recording / reproduction of the dual-layer recording disk, both the push-pull signal obtained from the main beam 70a and the push-pull signals obtained from the sub beams 70b and 70c are the light receiving unit 33a and the light receiving unit 33b that receive the main beam 70a. The TE signal may be obtained by dividing by the signals T ₁ and T ₂ output from. This is because, when information is recorded or reproduced on a two-layer recording disk, a part of the main beam 70a is reflected by another layer (non-condensing surface) that is not recorded / reproduced, and receives the sub beams 70b and 70c. , 33d, 33e, and 34f as stray light, so that the operation of the AGC becomes unstable.

The AGC is for suppressing the amplitude fluctuation of the TE signal due to the change in the reflectivity of the recording layer during recording / reproduction, but the light receiving units 33c, 33d, 33e that receive the sub-beams 70b, 70c during the two-layer recording / reproduction. , 34f, the sum signal of signals T ₃ , T ₄ , T ₅ , and T ₆ is not condensed with respect to the light amounts of the sub beams 70b and 70c reflected by the layer (condensing surface) being recorded and reproduced. Since the amount of stray light that is a part of the main beam 70a reflected by the surface is so large that it cannot be ignored, an unstable operation far from the original AGC operation is caused. As a result, the AGC operation of the TE signal by DPP Will be adversely affected. To prevent this, when using a dual-layer recording disk, AGC is performed using the sum signal of the signals output from the light receiving unit that receives the main beam for both the push-pull signal obtained from the main beam and the push-pull signal obtained from the sub beam. Therefore, it is possible to avoid the unstable operation of the AGC. Specifically, it is desirable to obtain the TE signal by the calculation shown in Equation 4.

TE signal = (T ₁ −T ₂ ) / (T ₁ + T ₂ ) −k [{(T ₃ −T ₄ ) + (T ₅ + T ₆ )} / (T ₁ + T ₂ )] (Formula 4)
As described above, in addition to detecting the TE signal by the DPP method, the TE signal may be detected by using a simple push-pull method using only the output signal based on the light amount of the main beam 70a. Further, when detecting the TE signal by a simple push-pull method, the signal is divided by the sum signal as in the detection by the DPP method. That is, the TE signal is obtained by the calculation represented by the following equation.

TE signal = (T ₁ −T ₂ ) / (T ₁ + T ₂ )
When the TE signal is obtained by this equation, the servo gain can be kept constant even if the reflectance of the information recording surface of the optical storage medium changes.

Here, T _f1 and T _f2 are signals output when the beam reflected by the light converging surface is incident on the light receiving portions 33a and 33b, and the beam reflected by the non-light condensing surface is incident on the light receiving portions 33a and 33b. When the signals output by incidence are T _s1 and T _s2 , the calculation described above is
TE signal = ( _Tf1 + _Ts1 − _Tf2 − _Ts2 ) / ( _Tf1 + _Ts1 + _Tf2 + _Ts2 )
It becomes. As can be seen from this calculation, the gain of the tracking control becomes smaller as the number of beams reflected by the non-condensing surface is incident on the light receiving portions 33a and 33b. Therefore,
T _f1 + T _f2 ≧ 5 ・ (T _s1 + T _s2 )
As a result, the change in the gain of tracking control is 20% or less, and stable tracking control with no practical problem is possible.

  Further, since the light amount of the main beam 70a is larger than the light amounts of the sub beams 70b and 70c, the simple push-pull method is less affected by stray light than the DPP method, and the lateral magnification α of the optical system can be reduced accordingly. . Therefore, a smaller optical pickup head can be provided by using a simple push-pull method for detecting the TE signal.

The information signal RF recorded in the optical storage medium 41 can be obtained by calculating the signals T ₁ and T ₂ output from the light receiving units 33a and 33b as shown in Equation 5.

RF = T ₁ + T ₂ (Formula 5)
Further, in the optical pickup device of the third embodiment, signals F ₁ , F ₂ , F ₃ , and F ₄ output from the light receiving portions 32a, 32b, 32c, and 32d of the photodetector 32 for detecting the FE signal are used. Thus, it is also possible to obtain a TE signal by a so-called phase difference method by the calculation of Expression 6.

TE signal = (F ₁ + F ₃ ) <Phase comparison> (F ₂ + F ₄ ) (Formula 6)
The <phase comparator> in Equation 6 to calculate the phase difference of the sum signal A ₂ of the signal F ₁ and phase and signal of the sum signal A ₁ of the signal F ₃ F ₂ and F _4, the polarity (signal of the phase difference A ₁ is obtained in accordance with whether A ₁ is ahead or behind A ₂ ) and the absolute value of the phase difference amount.

  That is, in the optical pickup device according to the third embodiment, in the case of an optical storage medium for recording / reproduction having a continuous groove, a TE signal is obtained by the DPP method to perform tracking control, and a pit row is formed. In the case of a read-only optical storage medium, it is possible to control the tracking by obtaining a TE signal by the phase difference method.

  In addition, even if the optical storage medium 41 has a narrow track pitch of 0.32 μm, the optical storage medium 41 is designed so that the tracking gain hardly decreases even if there is an eccentricity of several tens of μm. The distance between the main beam 70a and the sub beam 70b or the sub beam 70c on the information recording surface of the medium 41 is set to 4 μm. Therefore, the main beam 70a and the sub beams 70b and 70c on the photodetector 32 for detecting the FE signal are incident on the light receiving portions 32a, 32b, 32c, and 32d in an overlapping state. For this reason, the larger the light quantity of the sub beams 70b and 70c with respect to the main beam 70a, the lower the amplitude of the TE signal obtained by the phase difference method. For example, when the ratio of the light amount of the sub beam 70b and the sub beam 70c to the main beam 70a is 9: 1, the amplitude of the TE signal is reduced by about 10%, and there is no problem at this level. Since the light amounts of the sub beams 70b and 70c are usually set smaller than 1/9 with respect to the light amount of the main beam 70a so as not to erase the signal recorded on the optical storage medium, the optical pickup head of the third embodiment In the configuration, the TE signal by the phase difference method can be obtained without any problem. Of course, on the photodetector 34 for detecting the TE signal by the DPP method, both the main beam 70a and the sub beams 70b and 70c are condensed into a spot having a very small diameter with little aberration, and therefore the main beam 70a and the sub beam 70b. Alternatively, the sub beam 70c can be easily separated.

(Embodiment 4)
An optical pickup device according to a fourth embodiment of the present invention will be described with reference to the drawings.

  FIG. 10 is a diagram showing the configuration of the optical pickup head according to the fourth embodiment of the present invention. The difference from the optical pickup head of the first embodiment is an optical system that passes after being reflected by the polarization beam splitter 52. Specifically, the optical system includes a beam splitter 60, a hologram element 61, and a diffraction grating 62. The light detectors 35 and 36 are provided in place of the detector 32.

  The main beam 70a and the sub beams 70b and 70c reflected by the polarization beam splitter 52 become a convergent beam by the detection lens 59 having a focal length f3 of 30 mm, and the beam splitter 60 transmits 10% of the incident light amount, and the remaining beam. 90% is reflected and the incident light is divided into two. The beam that has passed through the beam splitter 60 is incident on the hologram element 61 to generate ± first-order diffracted lights 72b and 72c. The ± first-order diffracted lights 72b and 72c are received by the photodetector 35. On the hologram element 61, an off-axis zone plate that allows the FE signal to be detected by the spot size detection method is recorded as a pattern.

  On the other hand, the beam reflected by the beam splitter 60 enters the diffraction grating 62 to generate two + 1st order diffracted lights, which are received by the photodetector 36. FIG. 11 is a configuration diagram of the diffraction grating 62 in the fourth embodiment. The diffraction grating 62 is formed with two types of simple grating patterns 62a and 62b, each of which has a sawtooth shape and suppresses −1st order diffracted light. The sawtooth pattern can be formed as a general blazed pattern such as formed by oblique ion beam etching or etching combined with a plurality of masks.

  A boundary line 62c between the pattern 62a and the pattern 62b has a parallel relationship with the mapping of the track on the optical storage medium 41 in the main beam 70a and the sub beams 70b and 70c. The patterns 62a and 62b have the same pitch but different sawtooth directions. The pattern 62a generates diffracted light 73a, 73b, and 73c, and the pattern 62b generates diffracted light 74a, 74b, and 74c, respectively. The diffracted beams 73a and 74a are generated from the main beam 70a, the diffracted beams 73b and 74b are generated from the sub beam 70b, and the diffracted beams 73c and 74c are generated from the sub beam 70c, respectively. Further, the diffracted lights 71d and 71e are generated from the main beam reflected by the non-condensing surface.

FIG. 12 shows the relationship between the photodetector 36 and the diffracted lights 73a, 73b, 73c, 74a, 74b, and 74c received. The photodetector 36 has six light receiving portions 36a, 36b, 36c, 36d, 36e, and 36f, and receives the diffracted lights 73a, 73b, 73c, 74a, 74b, and 74c, respectively. Therefore, the diffracted lights 73a, 73b, 73c, 74a, 74b, and 74c generated by the diffraction grating 62 are arranged so as to be focused on the surface on which the light receiving portion of the photodetector 36 is formed. An interval d ₃ (for example, an interval between 73a and 73b or an interval between 73a and 74a) between adjacent beams on the photodetector 36 is 80 μm.

  In general, the Airy disk diameter w of the focused Gaussian beam is given by w = 1.22 × light source wavelength / lens numerical aperture. In the fourth embodiment, since the main beam 70a and the sub beams 70b and 70c are divided into two by the diffraction grating 62, the diameter in the direction in which the main beam 70a and the sub beams 70b and 70c are not divided is 13 μm. The diameter is 26 μm.

  In addition, crosstalk caused when the main beam 70a is mixed into the light receiving portions 36b, 36c, 36e, and 36f that receive the sub beams 70b and 70c fluctuates when the optical storage medium is tilted or defocused, and tracking is performed. May become unstable. Further, when the beam divided into two is mixed in the other light receiving portion, the amplitude of the TE signal is lowered. In any case, by setting the distance between these beams to be three times or more the Airy disk diameter, the influence becomes negligible and stable tracking control is possible.

Further, when an optical storage medium is used for a two-layer recording disk having two information recording surfaces, the optical pickup head of Embodiment 4 also detects the light beams 74d and 74e reflected by the non-condensing surface. By making the diameter d ₅ of the detector 36 larger than the width d ₄ of each of the light receiving portions 36a, 36b, 36c of the photodetector 36, the TE can be used even when tracking tracking or tilting of the optical storage medium occurs. There is almost no offset in the signal. Thus, a highly reliable information recording / reproducing apparatus can be realized by using the optical pickup head of the fourth embodiment. Note that the sub-beams reflected by the non-condensing surface are omitted.

  Similarly to the second embodiment, the substrate constituting the light source and the track on the optical storage medium may be optically arranged in parallel, and the influence of the beam 700 which is spontaneous emission light can be removed. An optical pickup head having no offset fluctuation in the signal can be realized.

(Embodiment 5)
An optical pickup head according to a fifth embodiment of the present invention will be described with reference to the drawings.

  FIG. 13 is a configuration diagram of a prism according to the fifth embodiment of the present invention. The optical pickup head of the fifth embodiment is that a prism 63 is used instead of the diffraction grating 62 used as the beam splitting element in the optical pickup head of the fourth embodiment.

  By splitting the beam using the prism 63, unnecessary diffracted light is not generated as in the case of using the diffraction element 62. Thereby, the light utilization efficiency can be increased, the signal-to-noise ratio of the detected signal can be increased, and the information recorded on the optical storage medium can be reproduced more faithfully.

(Embodiment 6)
An optical pickup head according to a sixth embodiment of the present invention will be described with reference to the drawings. The optical pickup head of the sixth embodiment has the same configuration as that of the optical pickup head of the fourth embodiment, except that a diffraction grating 64 is used instead of the diffraction grating 62 and a light detection is used instead of the photodetector 36. The device 37 is provided.

  FIG. 14 is a configuration diagram of the diffraction grating 64 in the sixth embodiment. FIG. 15 is a diagram showing the relationship between the photodetector 37 and the beam.

  The diffraction grating 64 has two types of sawtooth pattern regions 64a and 64b. The boundary line 64c between the patterns 64a and 64b has a parallel relationship with the mapping of the track on the optical storage medium 41 in the main beam 70a and the sub beams 70b and 70c. The difference between the diffraction grating 62 of the fourth embodiment and the diffraction grating 64 of the sixth embodiment is the orientation and period of the grating. The pattern 64a generates diffracted light 75a, 75b, and 75c, and the pattern 64b generates diffracted light 76a, 76b, and 76c, respectively. The diffracted lights 75a and 76a are generated from the main beam 70a, the diffracted lights 75b and 76b are generated from the sub beam 70b, and the diffracted lights 75c and 76c are generated from the sub beam 70c, respectively.

  As shown in FIG. 15, the photodetector 37 has light receiving portions 37a, 37b, 37c, 37d, 37e, and 37f arranged in a line in order, and diffracted light 75a, 75b, 75c, 76a, 76b, and 76c. Are respectively received. The size of each of the light receiving units 37a, 37b, 37c, 37d, 37e, and 37f is the same as that of each of the light receiving units 36a, 36b, 36c, 36d, 36e, and 36f of the photodetector 36 of the fourth embodiment. Further, the diffracted lights 75 a, 75 b, 75 c, 76 a, 76 b, and 76 c generated by the diffraction grating 64 are arranged so as to be focused on the photodetector 37.

  Beams 76 d and 76 e are diffracted light generated when the main beam reflected by the non-condensing surface enters the diffraction grating 64. Here, for the sake of clarity, the sub beam reflected by the non-light-collecting surface is omitted. When the objective lens moves during tracking tracking, the images of the beams 76d and 76e reflected by the non-condensing surface on the photodetector 37 move. However, since the optical pickup head of the sixth embodiment has a structure in which the light receiving portions 37a, 37b, 37c, 37d, 37e, and 37f are arranged in a line, the beams 76d and 76e are evenly distributed to the light receiving portion. The incident light cancels out the calculation for detecting the TE signal, and no offset occurs in the TE signal. For this reason, there is almost no offset in the TE signal even when tracking follows or when the optical storage medium is tilted. Thus, a highly reliable information recording / reproducing apparatus can be realized.

(Embodiment 7)
An optical pickup head according to a seventh embodiment of the present invention will be described with reference to the drawings. The optical pickup head of the seventh embodiment has the same configuration as that of the optical pickup head of the sixth embodiment, except that a diffraction grating 65 is used instead of the diffraction grating 64 and a light detection is used instead of the photodetector 37. The device 38 is provided.

  FIG. 16 is a configuration diagram of the diffraction grating 65 in the seventh embodiment. FIG. 17 is a diagram showing the relationship between the photodetector 38 and the beam.

  The diffraction grating 65 has two types of sawtooth pattern regions 65a and 65b, similar to the diffraction grating 64 of the sixth embodiment. A boundary line 65c between the patterns 65a and 65b has a parallel relationship with the mapping of the track on the optical storage medium 41 in the beams 70a to 70c. The difference between the diffraction grating 65 and the diffraction grating 64 is the period of the grating, and the diffraction grating 65 has a saw-tooth shape that is coarser than the diffraction grating 64.

  The pattern 65a generates diffracted light 77a, 77b, 77c, and the pattern 65b generates diffracted light 78a, 78b, 78c. The diffracted beams 77a and 78a are generated using the main beam 70a, the diffracted beams 77b and 78b are generated using the sub beam 70b, and the diffracted beams 77c and 77c are generated using the sub beam 70c, respectively.

  As shown in FIG. 17, the photodetector 38 includes light receiving portions 38a, 38b, 38c, 38d, 38e, and 38f arranged in a line, and diffracted light 77a, 77b, 77c, 78a, 78b, 78c is received. The sizes of the light receiving portions 38a, 38b, 38c, 38d, 38e, and 38f are the same as the sizes of the light receiving portions 37a, 37b, 37c, 37d, 37e, and 37f of the photodetector of the sixth embodiment. Further, the diffracted lights 77 a, 77 b, 77 c, 78 a, 78 b, 78 c generated by the diffraction grating 65 are arranged so as to be focused on the photodetector 38. The diffracted light 77a is disposed between the diffracted light 78a and the diffracted light 78b, and the diffracted light 78a is disposed between the diffracted light 77a and the diffracted light 77c.

  Beams 78d and 78e are diffracted light generated when the main beam 70a reflected by the non-condensing surface enters the diffraction grating 65. Here, for the sake of clarity, the sub beam reflected by the non-light-collecting surface is omitted. When a two-layer recording disk is used as the optical storage medium, depending on the setting of the interval between the two information recording surfaces and the numerical aperture of the objective lens, a large spherical aberration is imparted to the beam reflected by the non-condensing surface. For example, when the interval between two information recording surfaces is 40 μm and the numerical aperture of the objective lens is 0.85, the beam reflected by the non-condensing surface forms a largely distorted spot on the photodetector 38, The distortion increases when the position of the objective lens is moved by tracking tracking, but since the diffracted light is arranged as described above, the offset remaining in the TE signal is greatly reduced.

  In the seventh embodiment, for example, the light receiving units that output the signals for performing the differential operation are arranged adjacent to each other such that the light receiving unit 38c and the light receiving unit 38f are adjacent to each other. Even if the beam reflected by the non-condensing surface becomes distorted by the photodetector, the adjacent light receiving portions receive light almost uniformly. For this reason, there is almost no offset in the TE signal even when tracking is followed or when the optical storage medium is tilted. By using the optical pickup head of the seventh embodiment, information recording / reproduction with higher reliability can be achieved. A device can be obtained.

  Further, the space between the main beam 70a and the sub beams 70b and 70c may be designed to be wide so that a space is provided between the light receiving portions 38a and 38e and between the light receiving portions 38d and 38c. By doing in this way, it produces | generates from the diffracted light 77a produced | generated from the main beam 70a and the sub beam 70b compared with the space | interval of the diffracted light 77a produced | generated from the main beam 70a on the photodetector 38, and the diffracted light 78a. The distance between the diffracted light 78b and the distance between the diffracted light 78a generated from the main beam 70a and the diffracted light 77c generated from the sub beam 70c is increased. Accordingly, since the distance between the main beam and the sub beam on the condensing surface is widened, the amplitude of the tracking error signal is likely to decrease due to the eccentricity of the optical storage medium, but the beam condensed on the condensing surface. When defocusing occurs, due to tolerances when assembling the optical pickup head or residual aberration of the components used, large aberrations occur in the optical path from the light reflected from the light collecting surface to the photodetector. Even when added to the beam reflected at, crosstalk mixed in the light receiving portion where the main beam receives the sub beam can be reduced. Thereby, a tracking error signal with less offset can be obtained. Moreover, since the tolerance when assembling the optical pickup head can be increased, an inexpensive optical pickup head can be provided.

  Note that the diffraction grating and the prism for splitting the beam in Embodiments 3 to 7 described above into two can be manufactured at low cost by resin molding. Further, the optical storage medium need not be limited to a disk shape, and may have various shapes such as a card shape depending on applications. Furthermore, the optical pickup head of the present invention can be applied without problems to an optical storage medium having three or more information recording layers.

(Embodiment 8)
An optical pickup head according to an eighth embodiment of the present invention will be described with reference to the drawings.

  FIG. 18 is a diagram showing a configuration of an optical pickup head according to the eighth embodiment of the present invention. In the following, the reflected light from the optical storage medium is divided into an inner beam and an outer beam by the hologram element, and a spherical aberration error (hereinafter referred to as SAE) signal is obtained from the first-order diffracted light of the hologram element. A method for obtaining an RF signal from 0th-order diffracted light will be described.

  The beam emitted from the semiconductor laser light source 1 is converted into parallel light by the collimator lens 53, and 0th-order and ± 1st-order diffracted light is generated by the diffraction grating 58 to be divided into three beams. The beam passes through the combined lens 104 serving as a spherical aberration correcting unit composed of a concave lens and a convex lens, the wavefront is converted, and the light is condensed on the information storage medium 41 by the objective lens 56. The three beams focused on the optical storage medium 41 are reflected and diffracted by the optical storage medium 41, pass through the objective lens 56, the combined lens 104 and the quarter-wave plate 54 again, and are reflected by the beam splitter 52. .

  The three beams reflected by the beam splitter 52 pass through the hologram element 108 as a branching means, and are branched into first-order diffracted light and zero-order diffracted light. Since the ratio of the diffraction efficiency of the 0th-order diffracted light after passing through the hologram element 108 and one 1st-order diffracted light is 20: 1, the S / N of the RF signal is good. The three beams, which are zero-order diffracted light passing through the hologram element 108, are collected by the detection lens 59, given astigmatism in the direction of 45 degrees to the track by the cylindrical lens 57, and received by the photodetector 39. . The signal output from the photodetector 39 is input to the RF signal / FE signal / TE signal generation circuit 201.

  The RF signal generated and output by the RF signal / FE signal / TE signal generation circuit 201 is used to reproduce information recorded on the optical storage medium, and the FE signal and the TE signal are input to the control / drive circuit 204. Is done. The control / drive circuit 204 drives the actuators 91 and 92 of the objective lens 56 based on the input FE signal and TE signal.

  On the other hand, the + 1st order light and the −1st order light of the main beam diffracted by the hologram element 108 are also collected by the detection lens 59 and given astigmatism in the 45 degree direction to the track by the cylindrical lens 57, and the photodetector 39 receives light.

  A signal output from the photodetector 39 by these lights is input to the SAE signal generation circuit 202, and the SAE signal generation circuit 202 outputs an SAE signal based on the signal. The SAE signal is amplified and phase compensated by the control / drive circuit 203, and then supplied to the actuator 93. The actuator 93 changes the distance between the concave lens and the convex lens of the combined lens 104 as spherical aberration correcting means. The spherical aberration of the beam focused on the optical storage medium 41 is controlled to be minimum. The hologram element 108 and the SAE signal generation circuit 202 constitute spherical aberration detection means.

FIG. 19 is a diagram illustrating a configuration of the hologram element 108. Different diffraction grating is fabricated with each of the outer circle of the region 109 and the radius R ₁ of the inner circle area 110 the radius R ₁ lattice spacing. A projection view of the beam reflected / diffracted by the optical storage medium 41 and passed through the objective lens 56 onto the hologram element 108 corresponds to a circle having a radius _Rb (a broken line circle in FIG. 19). If R ₁ / R _b is about 0.75, the area of the beam covering the outer region and the area of the inner region are substantially equal, and the signal intensity is also substantially equal. At this time, the detection sensitivity that is the degree of change of the SAE signal with respect to spherical aberration due to the thickness error of the optical storage medium 41 becomes the highest. Therefore, R ₁ / R _b is optimally around 0.75.

  FIG. 20 shows the relationship between the photodetector 39 and the beam in the eighth embodiment. FIG. 20 also shows detailed arrangement examples of the arrangement of the respective light receiving portions and the RF signal / TE signal / FE signal generation circuit, SAE signal generation circuit, and the like. The photodetector 39 includes a main beam light receiving portion 153 including light receiving portions 153a, 153b, 153c, and 153d, a sub beam light receiving portion 152 including light receiving portions 152a, 152b, 154a, and 154b, and light receiving portions 151a, 151b, and 151c. , 151d, 151e, 151f, 155a, 155b, 155c, 155d, 155e, and 155f, the SAE signal light receiving portion 151 is roughly divided into three light receiving portions. Of the main beam, the 0th order light transmitted through the hologram element 108 is the beam 121, and among the sub beams, the 0th order light transmitted through the hologram element 108 is the beams 124a and 124b. The diffracted beam of + 1st order light is 122a, the beam of −1st order light is 122b, the beam of + 1st order light diffracted by the region 110 is 123a, and the beam of −1st order light is 123b. The light receiving units 153a, 153b, 153c, and 153d receive the beam 121 and output a current signal corresponding to the amount of light.

  The current-voltage conversion circuit 241 converts the current signal into a voltage signal and outputs the voltage signal. The adder 228 adds signals output from the light receiving unit 153a and the light receiving unit 153c arranged at the diagonal of the square light receiving unit. The adder 229 adds the signals output from the light receiving units 153b and 153d arranged at different diagonals of the square-shaped light receiving unit.

  The differential circuit 230 outputs a difference signal between the signal output from the adder 228 and the signal output from the adder 229, that is, an FE signal. The phase difference TE generation circuit 231 receives the output signals of the adder 228 and the adder 229, compares the phases of these signals, and outputs a phase difference TE signal. The adder 232 adds signals output from the light receiving units 153a and 153b arranged on one side of the rice field-shaped light receiving unit, and the adder 233 is arranged on another side of the rice field-shaped light receiving unit. The signals output from the light receiving units 153c and 153d are added. The differential circuit 234 outputs a difference signal between the signal output from the adder 232 and the signal output from the adder 233, that is, a TE signal (PP-TE) by a push-pull method.

  The adder 235 outputs a sum signal of the signals from the adder 232 and the adder 233, that is, an RF signal for reproducing information recorded on the optical storage medium. In addition, the light receiving units 152a and 152b and the light receiving units 154a and 154b receive the sub beams 124a and 124b, and output current signals corresponding to the light amounts. The current-voltage conversion circuit 240 receives the current signal and outputs a voltage signal. The differential circuit 236 outputs a difference signal between the sum signal of the light receiving unit 152a and the light receiving unit 154a and the sum signal of the light receiving unit 152b and the light receiving unit 154b, that is, a sub beam TE signal (SUB-TE).

  The differential circuit 237 receives the output signals of the differential circuit 234 and the differential circuit 236 and outputs the difference signal. This is the TE signal TEDPP by the DPP method. The adders 228, 229, 232, 233, 235, the differential circuits 230, 234, 236, 237 and the phase difference TE generation circuit 231 constitute an RF signal / FE signal / TE signal generation circuit 201. The light receiving units 151a, 151b, 151c, 151d, 151e, and 151f receive the beams 122a and 123a and output current signals corresponding to the received light amounts. The light receiving units 155a, 155b, 155c, 155d, 155e, and 155f receive the beams 122b and 123b and output a current signal corresponding to the amount of light received. The current-voltage conversion circuit 240 receives the current signal and outputs a voltage signal. The adder 221 adds signals output from the light receiving units 151b, 151d, and 151f and the light receiving units 155a, 155c, and 155e. The adder 222 adds signals output from the light receiving units 151a, 151c, and 151e and the light receiving units 155b, 155d, and 155f. The differential circuit 223 receives the signal output from the adder 221 and the signal output from the adder 222, and outputs a difference signal thereof. This is the SAE signal. The two adders 221 and 222 and the differential circuit 223 constitute the SAE signal generation circuit 202. On the other hand, the adder 224 adds signals output from the light receiving units 151a, 151b, and 151c and the light receiving units 155d, 155e, and 155f. The adder 225 adds signals output from the light receiving units 151d, 151e, and 151f and the light receiving units 155a, 155b, and 155c. The differential circuit 226 receives the signal output from the adder 224 and the signal output from the adder 225, and outputs a difference signal thereof. This is a rotation error (hereinafter referred to as “rotation error”) indicating the rotational deviation between the beams 122a and 122b, the beams 123a and 123b, the light receiving portions 151a, 151b, 151c, 151d, 151e, and 151f and the light receiving portions 155a, 155b, 155c, 155d, 155e, and 155f. ROT) signal. The ROT signal is used to adjust the rotation direction angle of the hologram element 108 that generates a spherical aberration beam and the photodetector 39 during head adjustment. If this value is adjusted to be zero, the hologram element 108 is correctly set in the photodetector 39.

  When detecting the TE signal and the SAE signal by the DPP method, as shown in FIG. 20, the sub-beams 124a and 124b for the DPP method and the beams 122a, 122b, 123a and 123b for detecting the SAE signal on the photodetector 39. Are arranged in a direction substantially orthogonal to the main beam 121. As a result, interference between the DPP method sub-beams 124a and 124b and the SAE signal detection beams 122a, 122b, 123a, and 123b can be minimized. Although an example in which the sub-beam is used in the DPP method is shown here, an effect of minimizing interference can be obtained by using this arrangement even if the sub-beam is used for tracking in the three-beam method.

  Furthermore, by detecting the light in the inner peripheral area and the light in the outer peripheral area side by side, the two outside the light receiving part for detecting the light in the inner peripheral area and the two inside the light receiving part for detecting the light in the outer peripheral area are shared. can do. As a result, the number of light receiving portions can be reduced, so that the light receiving portions can be simplified and downsized. Therefore, the optical head device can be reduced in size.

The spread of the reflected light at the non-condensing surface of the 0th-order light of the main beam is substantially circular, and the radius R _s is the optical distance between the two layers of the disk d, and the information storage medium side of the condensing optical system Is represented by R _s = 2 · d · NA · α, where NA is the numerical aperture of NA and α is the lateral magnification of the return path from the condensing optical system to the detector.

The light reflected by the non-condensing surface has uneven light intensity depending on the location, and if this light changes its position on the photodetector due to lens shift, disc tilt, etc., an error is given to the SAE signal. Since this unevenness is about several percent of the total amount of light, if the amount of light reflected on the non-condensing surface is substantially the same as the amount of light on the condensing surface for original detection, the influence on the SAE signal is also affected. A few percent. Therefore, the area S ₂ of the light receiving portion of the photodetector for obtaining the SAE signal is S ₂ = 2PD _x · PD _y , and S ₂ ≤π · R _s · R _s · η _s / η _m is satisfied. That is, S ₂ ≦ 4 · π · (d · NA · α) ² · η _s / η _m .

Here, η _s is the amount of light used for SAE detection, and η _m is the amount of 0th-order light of the main beam. In the optical system in which this relational expression is satisfied, even if there is reflected light from the non-condensing surface, the error of the SAE signal is small, and information on the condensing surface can be read and recorded correctly. The stray light amount can be reduced as the lateral magnification α is increased, as in the case of detecting the TE signal.

On the other hand, when the astigmatic difference (distance between the front focal line and the rear focal line) of the beam condensed by the combination of the detection lens and the cylindrical lens is Z ₀ and the refractive index of the substrate or the intermediate layer is n, the FE signal The detection range Δz with respect to the displacement of the optical storage medium is
_{Δz = Z 0/2 / α} 2
The detection range Δt for the SAE signal substrate or intermediate layer thickness error is:
Δt = Z ₀ · n ³ / α ² / (n ² −1) / NA ²
Are given respectively. When the lateral magnification α is increased, both Δz and Δt are decreased. Therefore, when the lateral magnification α is excessively increased, the detection range of the FE signal or the SAE signal becomes narrow, and the focus servo and the spherical aberration correction servo become unstable. End up. Accordingly, when the desired detection range is Δz and Δt, the lateral magnification α is obtained when the TE signal and SAE signal by the DPP method are detected using the same detection lens and cylindrical lens.
S ₁ · η _m · R _dfo / (4 · π · d ² · NA ² · η _s · R _fo ) ≦ α ≦ (Z ₀ · n ³ / Δt / (n ² −1) / NA ² ) ^{1 / 2}
When the TE signal and the FE signal by the DPP method are detected using the same detection lens and cylindrical lens,
_{S 1 · η m · R dfo} / (4 · π · d 2 · NA 2 · η s · R fo) ≦ α ≦ (Z 0/2 / Δz) 1/2
If the above equation is satisfied, the servo operation for controlling the focus, tracking, and spherical aberration correction is stably performed.

Here, when the wavelength of the light source is λ, Δz is 3 to 10 times λ / 2 / NA ² , and Δt is 5 to 30 times λ / NA ⁴ .

  Note that the SAE signal detection method in the optical pickup head of the eighth embodiment is not subject to any restrictions, and various methods such as any method described in Japanese Patent Laid-Open No. 2002-190125 are used. Needless to say, you can.

In addition, here, the configuration in which astigmatism is imparted to the beam has been described, but other FE signal detection methods such as a spot sizzle detection method can be applied. In the spot size detection method, the focal distance between the two beams is equivalent to the astigmatic difference in the astigmatism method, and the focal distance between the two beams may be designed as Z ₀ .

  It can also be used in an optical storage medium having three or more recording layers.

  When the optical storage medium has three or more recording layers, the sum of the amounts of light incident on the light-receiving portions that receive the sub-beams after the main beam is reflected by the respective non-condensing surfaces (number of recording layers-1). Should have the above-described relationship with respect to the light quantity of the sub beam.

(Embodiment 9)
An information recording / reproducing apparatus according to Embodiment 9 of the present invention will be described with reference to the drawings. FIG. 21 is a diagram showing a configuration of an information recording / reproducing apparatus optical pickup head according to the ninth embodiment. The information recording / reproducing apparatus includes an optical pickup head 80, an optical recording medium driving unit 81, an optical pickup head driving unit 82, an electric circuit 83, and a power supply unit 84. As the optical pickup head 80, the optical pickup head described in the first to eighth embodiments may be used.

  The optical recording medium drive unit 81 rotates the recording medium 41. A signal corresponding to the positional relationship between the optical pickup head 80 and the recording medium 41 is sent to the electric circuit unit 83. The electric circuit unit 83 amplifies or calculates a signal corresponding to this positional relationship, and finely moves the optical pickup head 80 or an objective lens (not shown) in the optical pickup head 80 based on the amplified or calculated signal.

  The optical pickup head 80 reads information recorded on the recording medium 41 and sends the signal to the electric circuit unit 83. The electric circuit unit 83 demodulates the information recorded on the recording medium 41 from the transmitted signal. Actuators 91 and 92 drive the objective lens in the optical pickup head. The signal and the optical pickup head drive unit 82 or actuators 91 and 92 perform focus servo and tracking servo on the recording medium 41 to read, write, or erase information. Power is supplied from the power supply unit 84 such as a power supply or an external power supply to the electric circuit unit 83, the optical pickup head drive unit 82, the optical recording medium drive unit 81, and the actuators 91 and 92. Note that a connection terminal for a power supply or an external power supply may be provided in each drive circuit.

DESCRIPTION OF SYMBOLS 1, 2, Semiconductor laser light source 4, 22, 63 Prism 5 Mirror 10 Light emitting point 11 Active layer 12 Substrate 16, 60 Beam splitter 17, 61, 108 Hologram element 18, 57 Cylindrical lens 31, 32, 33, 36, 37, 38 39 Photo detectors 31a to 31h, 32a to 32d, 33a to 33f, 36a to 36f, 37a to 37f, 38a to 38f, 151a to 151f, 152a to 152b, 153a to 153d, 154a to 154b, 155a to 155f 34a, 153 Main beam light receiving unit 34b, 34c, 154 Sub beam light receiving unit 34g, 34h Dummy light receiving unit 41 Optical storage medium 41a Transparent substrate 41b, 41c Information recording surface 52 Polarizing beam splitter 53 Collimating lens 54 Wavelength plate 55 Aperture 56 Objective Len 58, 62, 64, 65 Diffraction grating 59 Detection lens 62a, 62b, 64a, 64b, 65a, 65b Pattern 62c, 64c, 65c Dividing line 70, 71a, 71b, 71c, 75, 121, 122a, 122b, 123a, 123b beam 70a main beam 70b, 70c sub beam 72b, 72c, 73a, 73b, 73c, 74a, 74b, 74c, 71d, 71e, 76d, 76e, 78d, 78e diffracted light 80 optical pickup head 81 recording medium drive unit 82 optical pickup Head drive unit 83 Electric circuit 84 Power supply unit 91, 92 Actuator 104 Lens 108 Hologram element 109, 110 Region 151 SAE signal light receiving unit 201 RF signal / FE signal / TE signal generation circuit 202 SAE signal generation circuit 203, 04 Control / Drive Circuit 211 ROT Signal Generation Circuit 212 Rotation Adjustment Mechanism 221, 222, 224, 225, 228, 229, 232, 233 Adder 223, 226, 230, 234, 235, 236, 237 Differential Circuit 231 Phase Difference TE generation circuit 240, 241 Current-voltage conversion circuit

Claims (6)

A light source that emits a light beam;
Diffracting means for generating a plurality of diffracted lights from the beam emitted from the light source;
Converging means for condensing the plurality of diffracted lights from the diffracting means on an optical storage medium;
Beam branching means for branching the plurality of beams reflected on the optical storage medium by the plurality of diffracted lights collected on the optical storage medium;
Astigmatism giving means for giving astigmatism to the beam branched by the beam branching means;
Photodetection means for receiving a beam to which astigmatism is imparted by the astigmatism imparting means and outputting a signal corresponding to the amount of light of the received beam;
The light detection means includes a main beam light receiving unit that receives 0th-order diffracted light of the collected diffracted light and a sub-beam light receiving unit that receives 1st-order or higher diffracted light,
The optical storage medium has a plurality of information recording surfaces, and at least one information recording surface is formed with a guide groove,
Astigmatism given by the astigmatism giving means is Z ₀ ,
Of the diffracted light generated by the diffracting means, the diffraction efficiency of 0th-order diffracted light is η _m and the diffraction efficiency of 1st-order or higher diffracted light is η _s ,
The effective reflectance of the light condensing surface in the information recording surface where the beam condensed by the converging means is substantially focused is R _fo, and the non-light condensing surface other than the light condensing surface in the plurality of information recording surfaces. Let R _dfo be the effective reflectivity of the condensing surface,
The numerical aperture on the optical storage medium side of the convergence means is NA, the lateral magnification of the optical system in the return path from the optical storage medium to the light detection means is α, the wavelength of the beam emitted from the light source is λ, S ₁ · η _m · R _dfo / (4 · π · d ²⁾ where d is the optical distance between the two information recording surfaces of the optical storage medium and S ₁ is the area of one of the sub-beam receiving portions. _{^{· NA 2 · η s · R}} fo) ≦ α ≦ (Z 0/2 / Δz) has a ^1/2 relationship, and it Delta] z is 3 to 10 times the range of λ / ² / NA 2 An optical pickup head characterized by A light source that emits a light beam;
Diffracting means for generating a plurality of diffracted lights from the beam emitted from the light source;
Converging means for condensing the plurality of diffracted lights from the diffracting means on an optical storage medium;
Beam branching means for branching the plurality of beams reflected by the plurality of diffracted lights collected on the optical storage medium into two;
Astigmatism giving means for giving astigmatism to the first beam branched by the beam branching means;
Beam splitting means for splitting the second beam split by the beam splitting means into two beams;
First light detecting means for receiving a beam from the astigmatism means and outputting a signal corresponding to the amount of light of the received beam;
Second light detection means for receiving a beam from the beam splitting means and outputting a signal corresponding to the amount of light of the received beam;
The optical storage medium has a plurality of information recording surfaces, and at least one information recording surface is formed with a guide groove,
The optical pickup head, wherein the beam splitting unit splits the second beam in a direction parallel to the guide groove. A light source that emits a light beam;
Diffracting means for generating a plurality of diffracted lights from the beam emitted from the light source;
Converging means for condensing the plurality of diffracted lights from the diffracting means on an optical storage medium;
A plurality of diffracted lights collected on the optical storage medium receive a beam reflected on the optical storage medium, and light detection means for outputting a signal corresponding to the amount of the received beam,
The light detection means includes two main beam light receiving units that receive 0th-order diffracted light of the condensed diffracted light and four sub-beam light receiving units that receive 1st-order or higher diffracted light,
When the signals output from the main beam receiver are T ₁ and T ₂ and the signals output from the sub beam receiver are T ₃ , T ₄ , T ₅ and T ₆ ,
Tracking by calculation of (T ₁ −T ₂ ) / (T ₁ + T ₂ ) −k [{(T ₃ −T ₄ ) + (T ₅ + T ₆ )} / (T ₁ + T ₂ )] (k is a constant) An optical pickup head that detects an error signal. A light source that emits a light beam;
Diffracting means for generating a plurality of diffracted lights from the beam emitted from the light source;
Converging means for condensing the plurality of diffracted lights from the diffracting means on an optical storage medium;
Beam branching means for branching the plurality of beams reflected on the optical storage medium by the plurality of diffracted lights collected on the optical storage medium;
Photodetection means for receiving the beam branched by the beam branching means and outputting a signal according to the light amount of the received beam;
The light detection means has two light receiving parts,
The optical storage medium has a first information recording surface and a second information recording surface, and a guide groove is formed on the first information recording surface,
When the diffracted light collected by the converging means is focused on the first information recording surface and is not focused on the second information recording surface,
The signals reflected by the first information recording surface are received by the light detection means, and the signals output from the two light receiving units are T _f1 and T _f2 ,
Signals reflected by the second information recording surface are received by the light detection means, and signals output from the two light receiving units are T _s1 and T _s2 ,
The tracking error signal is detected by the calculation of (T _f1 + T _s1 −T _f2 −T _s2 ) / (T _f1 + T _s1 + T _f2 + T _s2 ), and the relationship of T _f1 + T _f2 ≧ 5 · (T _s1 + T _s2 ) Optical pickup head. Condensing means for converging the beam received by the light detection means in the optical path from the optical storage medium to the light detection means,
5. The optical pickup head according to claim 1, wherein the condensing means has a convex lens and a concave lens. An optical pickup head according to any one of claims 1 to 5, and a drive unit that changes a relative position between the optical storage medium and the optical pickup head,
An information recording / reproducing apparatus comprising: an electric signal processing unit that receives a signal output from the optical pickup head and performs calculation to obtain desired information.

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