WO2012056827A1 - Optical pickup device - Google Patents

Optical pickup device Download PDF

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Publication number
WO2012056827A1
WO2012056827A1 PCT/JP2011/071200 JP2011071200W WO2012056827A1 WO 2012056827 A1 WO2012056827 A1 WO 2012056827A1 JP 2011071200 W JP2011071200 W JP 2011071200W WO 2012056827 A1 WO2012056827 A1 WO 2012056827A1
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Prior art keywords
light
polarized light
optical
beam splitter
polarization
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PCT/JP2011/071200
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French (fr)
Japanese (ja)
Inventor
英隆 地大
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コニカミノルタオプト株式会社
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Priority to JP2012540738A priority Critical patent/JPWO2012056827A1/en
Publication of WO2012056827A1 publication Critical patent/WO2012056827A1/en

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    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B7/12—Heads, e.g. forming of the optical beam spot or modulation of the optical beam
    • G11B7/135—Means for guiding the beam from the source to the record carrier or from the record carrier to the detector
    • G11B7/1395—Beam splitters or combiners

Definitions

  • the present invention relates to an optical pickup device that is built in an optical disc apparatus and performs recording / reproduction of an optical disc such as a BD, DVD, or CD.
  • An optical pickup device condenses laser light emitted from a semiconductor laser element, which is a light source, onto a signal recording surface of an optical disk by an objective lens, and records (writes) or erases information, or from a signal recording surface. This is a device that reproduces information by detecting reflected light (returned light) of light with a photodetector.
  • the light emitted from the light source is S-polarized light (linearly polarized light).
  • the light is incident on the polarization beam splitter and reflected almost 100%, and is collimated by the collimator lens, and is converted into a wave plate.
  • Patent Document 1 proposes that at least one of a reflection mirror and a beam splitter included in a polarization optical system is provided with a retardation plate function by a film forming member, and a wavelength plate is omitted.
  • the return light changes in polarization due to the phase difference caused by the birefringence of the optical disk and becomes elliptically polarized light.
  • a polarization beam splitter is used to separate light incident on an optical disk and signal light from the optical disk.
  • the return light affected by the birefringence of the disk is incident on the wave plate in the state of elliptical polarization, and therefore enters the polarization beam splitter as linearly polarized light that is a mixture of P and S polarizations.
  • the polarization beam splitter transmits almost 100% of the P-polarized light and reflects almost 100% of the S-polarized light, the transmittance of the return light is between 0 and 100%.
  • the transmittance here depends on the amount of birefringence of the optical disk. Accordingly, the amount of light reaching the photodetector (return path light amount) greatly depends on the amount of birefringence of the optical disk and is not stable.
  • the return light is incident on the beam splitter as elliptically polarized light having both the P-polarized component and the S-polarized component. .
  • the beam splitter also has polarization dependence, the return light transmittance still depends on the amount of birefringence of the optical disk.
  • An object of the present invention is to provide an optical pickup device with reduced influence.
  • the present invention condenses laser light emitted from a semiconductor laser element on a signal recording surface of an optical disc via a polarizing optical system, and returns light from the signal recording surface to the polarizing optical system.
  • the semiconductor laser element is disposed so as to emit light having a predetermined polarization intensity ratio, and a beam splitter and a rising mirror included in the polarization optical system
  • a film forming member for controlling the polarization intensity and phase difference of the incident light of the laser beam to convert it into circularly polarized light, and a straight line passing through the incident point of the laser beam to the optical disc and the center point of the optical disc,
  • the polarizing optical system and the optical disk are arranged so that the angle formed by the light incident on the rising mirror and the straight line projected onto the optical disk is within a range of 0 ⁇ 10 ° or 90 ⁇ 10 °, and the semiconductor laser S-polarized light to the beam
  • the laser light emitted from the semiconductor laser element is P / S polarized light separated by the beam splitter and the rising mirror, it can be converted into circularly polarized light without reducing the amount of light as much as possible.
  • the influence of birefringence of the optical disk can be reduced.
  • the film forming member is a multilayer dielectric film.
  • the beam splitter and the rising mirror can have the function of a wave plate, and the wave plate can be omitted in the polarization optical system. Therefore, the number of parts can be reduced, leading to reduction in assembly man-hours and downsizing of the optical pickup device. Furthermore, even when the optical disc has birefringence, information can be recorded / reproduced.
  • FIG. 6 is a partially enlarged view of FIG. 5.
  • FIG. 7 is a partially enlarged view of FIG. 6.
  • FIG. It is a figure which shows the transmittance
  • FIG. It is a figure which shows the intensity
  • FIG. It is a figure which shows the intensity
  • FIG. It is a figure which shows the intensity
  • FIG. It is a figure which shows the intensity
  • FIG. 1 is a plan view of a polarizing optical system and an optical disc of the optical pickup device of the present invention
  • FIG. 2 is a front view of the polarizing optical system and optical disc of the optical pickup device of the present invention.
  • the optical pickup device 10 includes a semiconductor laser element (laser diode) 11, a diffraction grating 12, a beam splitter 13, a collimator lens 14, a rising mirror 15, an objective lens 16, and a photodetector (photodetector) 17. It has.
  • the semiconductor laser element 11 is disposed so as to emit light having a predetermined polarization intensity ratio. Since this polarization intensity ratio affects the design of the film forming member described later, it is necessary to optimize the mutual relationship.
  • the diffraction grating 12 separates the laser beam emitted from the semiconductor laser element 11 into a plurality of laser beams.
  • the beam splitter 13 reflects a plurality of laser beams from the diffraction grating 12 by generating a phase difference (hereinafter referred to as a PS phase difference) between P-polarized light and S-polarized light, and returns light (reflected from the optical disk 20). Light).
  • a PS phase difference phase difference between P-polarized light and S-polarized light
  • the collimating lens 14 converts a plurality of laser beams from the beam splitter 13 into parallel light.
  • the raising mirror 15 generates parallel light from the collimating lens 14 to convert it into circularly polarized light and reflects it so as to be bent at a right angle, and then guides it to the objective lens 16 side.
  • the objective lens 16 collects the light reflected by the rising mirror 15 onto the optical disc 20.
  • the reflected light (returned light) reflected by the optical disc 20 is received by the photodetector 17.
  • the beam splitter 13 and the rising mirror 15 are laminated on a reflecting surface of a base material such as glass by vapor deposition or the like as a multilayer dielectric film (a plurality of dielectric films laminated) as a film forming member (not shown). Formed.
  • the present invention is designed to control the polarization intensity and the phase difference so as to convert it into circularly polarized light. Since the polarization intensity and the phase difference are determined by the refractive index, the film thickness, and the laminated structure of the multilayer dielectric film, they can be controlled by selecting an optimal combination thereof. For example, desired polarization intensity and phase difference can be obtained by alternately laminating SiO 2 and TiO 2 and optimizing the film thickness and the number of times of lamination.
  • the laser light emitted in the horizontal front direction from the semiconductor laser element 11 disposed in front is separated into a plurality of laser lights by the diffraction grating 12 and is orthogonally crossed by the beam splitter 13. It will be bent in the direction of horizontal right.
  • the laser light traveling in the horizontal right direction is converted into parallel light by the collimator lens 14 and then converted into circularly polarized light by being reflected by the reflecting surface of the rising mirror 15, and is bent at a right angle and vertically upward.
  • the light is condensed (irradiated) onto the signal recording surface of the optical disk 20 that is rotationally driven through the objective lens 16. Thereby, information can be written (recorded) or erased on the optical disc 20.
  • the reflected light (returned light) from the signal recording surface of the optical disc 20 travels vertically downward, passes through the objective lens 16, and is reflected at the reflecting surface of the rising mirror 15 to be bent at a right angle. Proceeding horizontally to the left, the light passes through the collimating lens 14 and the beam splitter 13 and is detected by the photodetector 17. Thereby, the information stored (recorded) on the optical disc 20 can be reproduced.
  • Optical discs 20 of various qualities are in circulation, and some of them have birefringence on the signal recording surface side.
  • the birefringence direction (axis) often extends in the radial direction from the center of the optical disc 20.
  • the object of the present invention even when the laser light emitted from the semiconductor laser element 11 is P / S polarized light separated by the beam splitter 13 and the rising mirror 15 is converted into circularly polarized light without reducing the amount of light as much as possible. And reducing the influence of birefringence of the optical disk 20).
  • the intensities of S-polarized light and P-polarized light with respect to the beam splitter 13 of the laser light emitted from the semiconductor laser element 11 are E s and E p , respectively, and the reflectance (%) of the S-polarized light and P-polarized light at the beam splitter 13.
  • R s1 and R p1 and the reflection phase difference (°), which is a value obtained by subtracting the S polarization phase from the reflected P polarization phase, is ⁇ 1, and the reflectance of S polarization and P polarization at the rising mirror 15 ( %) Are R s2 and R p2 , respectively, and a reflection phase difference (°) that is a value obtained by subtracting the S polarization phase from the P polarization phase after reflection is ⁇ 2 .
  • E s and E p cancel the intensity ratio of R s1 and R p1 generated in the beam splitter 13 as much as possible, while 1 ⁇ E p / E s ⁇ 3 in order to suppress a decrease in the amount of light on the forward path .
  • the semiconductor laser element 11 may be disposed at a predetermined rotation angle with respect to the optical axis.
  • the P / S ratio of the light traveling toward the optical disk needs to be about 1, so here 0.95 ⁇ E s R s1 R p2 / Let E p R p1 R s2 ⁇ 1.05.
  • the rising mirror 15 differs from the beam splitter 13 by 90 ° in the direction in which the light is bent, so that the polarization component is switched, E s R s1 R p2 is the P-polarized light intensity toward the optical disc, and E p R p1 R s2 is the optical disc.
  • This numerical range is based on specifications required for an optical pickup device for reading and writing of an optical disk. That is, if it is within this numerical range, there will be no problem in reading and writing of the optical disk.
  • the phase difference between the S-polarized light and the P-polarized light traveling toward the optical disc needs to be about 90 °, and therefore here 90 (2n ⁇ 1) ⁇ 10 ⁇
  • ⁇ 90 (2n ⁇ 1) +10 (n 1, 2).
  • this numerical range is based on specifications required for an optical pickup device for reading and writing of an optical disk.
  • the elliptically polarized light (the elliptic axis is the elliptical axis) with the reflected light having a P / S ratio of approximately 1. About 45 °). Therefore, an angle ⁇ formed by a straight line passing through the incident point P of the laser beam on the optical disc 20 and the center point O of the optical disc 20 and a straight line obtained by projecting the incident light on the rising mirror 15 onto the optical disc 20 is 0 ⁇ 10.
  • the polarizing optical system and the optical disc 20 are arranged so as to be within the range of 0 ° or 90 ⁇ 10 °.
  • FIG. 1 and 2 show the case where the angle ⁇ is 0 °.
  • 3 is a plan view of the polarization optical system and the optical disc of the optical pickup device when the angle ⁇ is 90 °
  • FIG. 4 is a front view of the polarization optical system and the optical disc of the optical pickup device when the angle ⁇ is 90 °. Indicates.
  • FIGS. 5 and 6 are graphs showing the transmittance of the beam splitter 13 in the return path when circularly polarized light is incident at various angles ⁇ on optical disks having various birefringence amounts. 7 and 8 are partially enlarged views of FIGS. 5 and 6, respectively.
  • the beam splitter 13 used here has a P-polarized reflectance of 74% and an S-polarized reflectance of 93%.
  • the transmittance of the beam splitter 13 is 100% when the birefringence amount of the optical disk is 0 °, that is, when the birefringence is not exhibited.
  • the transmittance of the beam splitter 13 for the return light needs to be in the range of about 100 ⁇ 25% in consideration of the elliptical polarization and the influence of the birefringence of the optical disk 20. If it is further away, reading of the optical disk 20 becomes difficult.
  • 5 to 8 show the case of circularly polarized light, and considering the difference from elliptically polarized light, it is desirable that the transmittance of the beam splitter 13 for returning light is in the range of about 100 ⁇ 20%. 7 and 8, the transmittance of the beam splitter 13 is 100 ⁇ 20% when the angle ⁇ is in the range of 0 ⁇ 10 ° or 90 ⁇ 10 °. Therefore, it can be said that the angle ⁇ within the range of 0 ⁇ 10 ° or 90 ⁇ 10 ° is one of the conditions for reducing the influence of the birefringence of the optical disc 20.
  • the object of the present invention is to reduce the amount of light as much as possible even when the laser light emitted from the semiconductor laser element 11 is P / S polarized light separated by the beam splitter 13 and the rising mirror 15. Without reducing the influence of the birefringence of the optical disc 20).
  • the beam splitter 13 and the rising mirror 15 can have the function of a wave plate, and the wave plate can be omitted in the polarization optical system. Therefore, the number of parts can be reduced, leading to reduction in assembly man-hours and downsizing of the optical pickup device. Moreover, it is possible to read / write normally even for an optical disc having birefringence.
  • R p2 ⁇ 90 and R s2 ⁇ 95 so as not to reduce the light amount as much as possible in the rising mirror 15. Further, from the viewpoint of keeping the P / S ratio of the light incident on the rising mirror 15 as close to 1 as possible, it is desirable that 0.95 ⁇ E s R s1 / E p R p1 ⁇ 1.05.
  • the film forming member of the beam splitter 13 in order from the base material side, 223.56 nm thick SiO 2 , 25.00 nm thick Ta 2 O 5 , 58.89 nm thick SiO 2 , 79.4 nm thick Ta 2 O 5 , 57.87 nm Thick SiO 2 , 25.00 nm thick Ta 2 O 5 , 30.00 nm thick SiO 2 , 25.00 nm thick Ta 2 O 5 , 89.21 nm thick SiO 2 , 42.03 nm thick Ta 2 O 5 , 288.95 nm thick SiO 2 , 178.05 nm thick Ta 2 O 5 , 44.18 nm thick SiO 2 , 190.76 nm thick Ta 2 O 5 , 246.13 nm thick SiO 2 , 223.5
  • the refractive index of SiO 2 for 550 nm light is 1.445, and the refractive index of Ta 2 O 5 is 2.225.
  • the film forming member of the rising mirror 15 in order from the base material side, 85.15 nm thick Ta 2 O 5 , 137.06 nm thick SiO 2 , 84.69 nm thick Ta 2 O 5 , 136.21 nm thick SiO 2.
  • FIG. 10 is a diagram showing the intensity of S-polarized light and P-polarized light after being reflected by the beam splitter 13. It can be seen that the P / S ratio is approximately 1, indicating elliptically polarized light.
  • FIG. 11 is a diagram showing the intensity of S-polarized light and P-polarized light after being reflected by the rising mirror 15. It can be seen that the P / S ratio is approximately 1, indicating that the light is approximately circularly polarized.
  • FIG. 12 is a diagram showing the intensity of S-polarized light and P-polarized light after being reflected by the optical disk 20. It can be seen that the P / S ratio is approximately 1, indicating elliptically polarized light. The major axis of the ellipse is 45 ° or 135 °, and the P / S ratio does not depend on the birefringence amount of the optical disc. On the other hand, the ellipticity of elliptically polarized light depends on the amount of birefringence of the optical disk 20.
  • FIG. 13 is a diagram showing the intensity of S-polarized light and P-polarized light after being reflected by the rising mirror 15 for returning light. It can be seen that the P / S ratio is approximately 1, indicating elliptically polarized light. The major axis of the ellipse is 45 ° or 135 °, and the P / S ratio does not depend on the birefringence amount of the optical disc. On the other hand, the ellipticity of elliptically polarized light depends on the amount of birefringence of the optical disk 20.
  • FIG. 14 is a diagram showing the transmittance of the return beam through the beam splitter 13.
  • the transmittance of the return light beam splitter 13 is not affected by the phase difference between the S-polarized light and the P-polarized light caused by the amount of birefringence of the optical disk because the P / S ratio of the returned light incident on the beam splitter 13 is approximately 1. It is always about 16.5%.
  • FIGS. 9 to 11 are the same in the first comparative example.
  • FIG. 15 is a diagram showing the intensity of S-polarized light and P-polarized light after being reflected by the optical disc 20. It turns out that it becomes elliptically polarized light.
  • the major axis of the ellipse is in the S or P direction, and both the P / S ratio and the ellipticity of elliptically polarized light depend on the birefringence amount of the optical disc 20.
  • FIG. 16 is a diagram showing the intensity of S-polarized light and P-polarized light after being reflected by the rising mirror 15 for returning light. It turns out that it becomes elliptically polarized light. Both the P / S ratio and the ellipticity of elliptically polarized light depend on the birefringence amount of the optical disk 20.
  • FIG. 17 is a diagram showing the transmittance of the beam splitter 13 for returning light.
  • the transmittance of the return light beam splitter 13 is affected by the phase difference between the S-polarized light and the P-polarized light caused by the amount of birefringence of the optical disk because the P / S ratio of the returned light incident on the beam splitter 13 is greatly deviated from 1. Is done.
  • the configuration of the beam splitter 13 is the same as that of the first embodiment, and the configuration of the rising mirror 15 is different from that of the first embodiment.
  • FIG. 19 is a diagram showing the intensity of S-polarized light and P-polarized light after passing through the wave plate. It can be seen that light incident on a wave plate having an axis in the 45 ° direction undergoes a phase difference between the 45 ° direction and the 135 ° direction, has a P / S ratio of approximately 1, and is substantially circularly polarized. The intensities of S-polarized light and P-polarized light after being reflected by the rising mirror 15 are the same as those in FIG.
  • FIG. 20 is a diagram showing the intensity of S-polarized light and P-polarized light after being reflected by the optical disc 20. It can be seen that the P / S ratio is approximately 1, indicating elliptically polarized light. The P / S ratio does not depend on the birefringence amount of the optical disk. On the other hand, the ellipticity of elliptically polarized light depends on the amount of birefringence of the optical disk 20.
  • FIG. 21 is a diagram showing the intensity of S-polarized light and P-polarized light after being reflected by the rising mirror 15 for returning light. It can be seen that the P / S ratio is approximately 1, indicating elliptically polarized light. The P / S ratio does not depend on the birefringence amount of the optical disk. On the other hand, the ellipticity of elliptically polarized light depends on the amount of birefringence of the optical disk 20.
  • FIG. 22 is a diagram showing the intensity of S-polarized light and P-polarized light after passing through the wave plate of the return light. It can be seen that the light incident on the wave plate undergoes a phase difference in the 45 ° direction and the 135 ° direction and is linearly polarized light. The P / S ratio depends on the birefringence amount of the optical disc 20.
  • FIG. 23 is a diagram showing the transmittance of the beam splitter 13 for returning light.
  • the transmittance of the return light beam splitter 13 is affected by the phase difference between the S-polarized light and the P-polarized light caused by the amount of birefringence of the optical disk because the P / S ratio of the returned light incident on the beam splitter 13 is greatly deviated from 1. Is done.
  • the P / S ratio of the return light incident on the beam splitter 13 is greatly deviated from 1, so that the transmittance of the beam splitter 13 is the same as that of the optical disk. It is affected by the amount of birefringence. Therefore, reading becomes impossible when the optical disc has birefringence.
  • FIG. 24 is a diagram showing the intensity of S-polarized light and P-polarized light after being reflected by the optical disc 20. It can be seen that the P / S ratio is approximately 1, indicating elliptically polarized light. The P / S ratio does not depend on the birefringence amount of the optical disk. On the other hand, the ellipticity of elliptically polarized light depends on the amount of birefringence of the optical disk 20.
  • FIG. 25 is a diagram showing the intensity of S-polarized light and P-polarized light after being reflected by the rising mirror 15 for returning light. It can be seen that the P / S ratio is approximately 1, indicating elliptically polarized light. The P / S ratio does not depend on the birefringence amount of the optical disk. On the other hand, the ellipticity of elliptically polarized light depends on the amount of birefringence of the optical disk 20.
  • FIG. 26 is a diagram showing the intensity of S-polarized light and P-polarized light after passing through the wave plate of the return light. It can be seen that the light incident on the wave plate is subjected to a phase difference in the 45 ° direction and the 135 ° direction and is elliptically polarized light having a major axis in the S or P direction. The P / S ratio depends on the birefringence amount of the optical disc 20.
  • FIG. 27 is a diagram showing the transmittance of the beam splitter 13 for returning light.
  • the transmittance of the return light beam splitter 13 is affected by the phase difference between the S-polarized light and the P-polarized light caused by the amount of birefringence of the optical disk because the P / S ratio of the returned light incident on the beam splitter 13 is greatly deviated from 1. Is done.
  • SiO 2 may be MgF 2, AL 2 O 3, etc., in place of the Ta 2 O 5, for example, Nb 2 O 5, TiO 2 , La 2 It may be a mixture of O 3 and TiO 2 or the like.
  • the optical pickup device of the present invention can be used for recording / reproduction of optical disks such as BD, DVD, and CD.

Abstract

The purpose of the invention is to provide an optical pickup device which suppresses a decrease in the amount of light, performs a conversion to circularly-polarized light, and decreases the effect of the birefringence of an optical disk. The optical pickup device has a configuration whereby a polarized light optical system and an optical disk are arranged such that the angle which is formed by a line passing through the incident point of laser light with respect to the optical disk and the center point of the optical disk, and a line on which light incident to a rising mirror is projected toward the optical disk, is within the range of 0±10° or 90±10°, and are arranged so as to fulfill a prescribed relational expression.

Description

光ピックアップ装置Optical pickup device
　本発明は、光ディスク装置に内蔵され、ＢＤ、ＤＶＤ、ＣＤなどの光ディスクの記録・再生を行う光ピックアップ装置に関する。 The present invention relates to an optical pickup device that is built in an optical disc apparatus and performs recording / reproduction of an optical disc such as a BD, DVD, or CD.
　光ピックアップ装置は、光源である半導体レーザ素子から出射されたレーザ光を対物レンズによって光ディスクの信号記録面上に集光させることで、情報の記録（書き込み）や消去を行ったり、信号記録面からの反射光（戻り光）を光検出器で検出することによって、情報の再生を行う装置である。 An optical pickup device condenses laser light emitted from a semiconductor laser element, which is a light source, onto a signal recording surface of an optical disk by an objective lens, and records (writes) or erases information, or from a signal recording surface. This is a device that reproduces information by detecting reflected light (returned light) of light with a photodetector.
　一般的な光ピックアップ装置では、光源から出射される光はＳ偏光（直線偏光）であり、その光は偏光ビームスプリッタに入射してほぼ１００％反射され、コリメータレンズで平行光にされ、波長板で円偏光にされ、立ち上げミラーで折り返され、対物レンズで集光され、光ディスクに到達する。そして、光ディスクで反射された光は、往路の逆経路を通って波長板でＰ偏光にされ、偏光ビームスプリッタに入射してほぼ１００％透過され、光検出器へ到達する。特許文献１では偏光光学系に含まれる反射ミラー及びビームスプリッタの少なくとも１つに成膜部材によって位相差板の機能を持たせ、波長板を省略することが提案されている。 In a general optical pickup device, the light emitted from the light source is S-polarized light (linearly polarized light). The light is incident on the polarization beam splitter and reflected almost 100%, and is collimated by the collimator lens, and is converted into a wave plate. To be circularly polarized, folded by a rising mirror, condensed by an objective lens, and arrives at the optical disk. Then, the light reflected by the optical disk passes through the reverse path of the forward path, is converted to P-polarized light by the wave plate, enters the polarization beam splitter, and is almost 100% transmitted, and reaches the photodetector. Patent Document 1 proposes that at least one of a reflection mirror and a beam splitter included in a polarization optical system is provided with a retardation plate function by a film forming member, and a wavelength plate is omitted.
特開２００４－２６５５２５号公報JP 2004-265525 A
しかしながら光ディスクの品質が悪く複屈折を有する場合、円偏光で集光させても、その戻り光は光ディスクの複屈折により生じる位相差によって偏光が変化し楕円偏光となる。 However, when the quality of the optical disk is poor and it has birefringence, even if it is condensed with circularly polarized light, the return light changes in polarization due to the phase difference caused by the birefringence of the optical disk and becomes elliptically polarized light.
　一般的な光ピックアップ装置の場合、光ディスクへの入射光と光ディスクからの信号光を分離するために偏光ビームスプリッタが用いられる。光ディスクが複屈折を有する場合、ディスクの複屈折の影響を受けた戻り光は楕円偏光の状態で波長板に入射するため、Ｐ偏光とＳ偏光が混合した直線偏光となって偏光ビームスプリッタに入射する。偏光ビームスプリッタはＰ偏光をほぼ１００％透過し、Ｓ偏光をほぼ１００％反射するので、戻り光の透過率は０～１００％の間となる。ここでの透過率は、光ディスクの複屈折量に依存する。したがって、光検出器に到達する光量（復路光量）は光ディスクの複屈折量に大きく依存することになり安定しない。 In the case of a general optical pickup device, a polarization beam splitter is used to separate light incident on an optical disk and signal light from the optical disk. When the optical disk has birefringence, the return light affected by the birefringence of the disk is incident on the wave plate in the state of elliptical polarization, and therefore enters the polarization beam splitter as linearly polarized light that is a mixture of P and S polarizations. To do. Since the polarization beam splitter transmits almost 100% of the P-polarized light and reflects almost 100% of the S-polarized light, the transmittance of the return light is between 0 and 100%. The transmittance here depends on the amount of birefringence of the optical disk. Accordingly, the amount of light reaching the photodetector (return path light amount) greatly depends on the amount of birefringence of the optical disk and is not stable.
　また、特許文献１のように位相差板の機能を成膜部材で実現させる場合であっても、戻り光はＰ偏光成分、Ｓ偏光成分の両方を有した楕円偏光のままビームスプリッタに入射する。しかし、ビームスプリッタも偏光依存性を有するため、戻り光の透過率は、やはり光ディスクの複屈折量に依存する。 Further, even when the retardation plate function is realized by the film forming member as in Patent Document 1, the return light is incident on the beam splitter as elliptically polarized light having both the P-polarized component and the S-polarized component. . However, since the beam splitter also has polarization dependence, the return light transmittance still depends on the amount of birefringence of the optical disk.
　また、情報を記録する場合、多くの光量が必要であるため、ビームスプリッタの反射率を上げて光ディスクへ向かう光量を多くする必要がある。ビームスプリッタの反射率を上げる場合には反射光のＰ／Ｓ偏光分離が大きくなってしまうので、特許文献１のような構成では光ディスクに向かう光のＰ／Ｓ比を１に近づけることが難しい。したがってビームスプリッタの反射率を上げると光ディスクに向かう光が円偏光にならず、情報を記録／再生するのに必要な仕様に達しない。 Also, when recording information, since a large amount of light is required, it is necessary to increase the reflectivity of the beam splitter and increase the amount of light directed to the optical disc. When the reflectivity of the beam splitter is increased, the P / S polarization separation of the reflected light becomes large. Therefore, in the configuration as in Patent Document 1, it is difficult to make the P / S ratio of the light toward the optical disk close to 1. Therefore, when the reflectivity of the beam splitter is increased, the light directed to the optical disk does not become circularly polarized light and does not reach the specifications necessary for recording / reproducing information.
　本発明は、半導体レーザ素子から出射されたレーザ光をビームスプリッタ及び立ち上げミラーによって、Ｐ／Ｓ偏光分離した場合においても、できるだけ光量を減少させずに円偏光に変換するとともに光ディスクの複屈折の影響を低減した光ピックアップ装置を提供することを目的とする。 In the present invention, even when laser light emitted from a semiconductor laser element is P / S polarized light separated by a beam splitter and a rising mirror, it is converted into circularly polarized light without reducing the amount of light as much as possible and the birefringence of the optical disk is reduced. An object of the present invention is to provide an optical pickup device with reduced influence.
　上記目的を達成するために本発明は、半導体レーザ素子から出射されたレーザ光を偏光光学系を介して光ディスクの信号記録面に集光し、該信号記録面からの戻り光を前記偏光光学系を介して光検出器で検出する光ピックアップ装置において、前記半導体レーザ素子を所定の偏光強度比をもった光を出射するように配設し、前記偏光光学系に含まれるビームスプリッタ及び立ち上げミラーに、前記レーザ光の入射光に対して偏光強度及び位相差を制御して円偏光に変換する成膜部材を設け、光ディスクへのレーザ光の入射点と光ディスクの中心点とを通る直線と、立ち上げミラーへの入射光を光ディスクへ投影した直線とのなす角が、０±１０°又は９０±１０°の範囲内になるように、前記偏光光学系及び光ディスクを配設し、前記半導体レーザ素子から出射されたレーザ光の前記ビームスプリッタに対するＳ偏光、Ｐ偏光の強度をそれぞれＥｓ、Ｅｐとし、前記ビームスプリッタでのＳ偏光、Ｐ偏光の反射率（％）をそれぞれＲｓ１、Ｒｐ１、反射後のＰ偏光位相からＳ偏光位相を引いた値である反射位相差（°）をδ１とし、前記立ち上げミラーでのＳ偏光、Ｐ偏光の反射率（％）をそれぞれＲｓ２、Ｒｐ２、反射後のＰ偏光位相からＳ偏光位相を引いた値である反射位相差（°）をδ２とした場合、１＜Ｅｐ／Ｅｓ≦３、１＜Ｒｓ１／Ｒｐ１≦３、６０≦Ｒｓ１≦１００、０．９５≦ＥｓＲｓ１Ｒｐ２／ＥｐＲｐ１Ｒｓ２≦１．０５、９０（２ｎ－１）－１０≦｜δ１－δ２｜≦９０（２ｎ－１）＋１０　（ｎ＝１，２）を満たすことを特徴とする。 In order to achieve the above object, the present invention condenses laser light emitted from a semiconductor laser element on a signal recording surface of an optical disc via a polarizing optical system, and returns light from the signal recording surface to the polarizing optical system. In the optical pick-up apparatus for detecting with a photodetector via the semiconductor laser element, the semiconductor laser element is disposed so as to emit light having a predetermined polarization intensity ratio, and a beam splitter and a rising mirror included in the polarization optical system A film forming member for controlling the polarization intensity and phase difference of the incident light of the laser beam to convert it into circularly polarized light, and a straight line passing through the incident point of the laser beam to the optical disc and the center point of the optical disc, The polarizing optical system and the optical disk are arranged so that the angle formed by the light incident on the rising mirror and the straight line projected onto the optical disk is within a range of 0 ± 10 ° or 90 ± 10 °, and the semiconductor laser S-polarized light to the beam splitter of the laser beam emitted from the laser device, the P-polarized light intensity, respectively E s, and E p, the S-polarized light at the beam splitter, the reflectance of P-polarized light (%), respectively R s1, R p1 is a reflection phase difference (°), which is a value obtained by subtracting the S polarization phase from the reflected P polarization phase, and δ 1, and the reflectance (%) of S polarization and P polarization at the rising mirror is R When s 2 , R p2 , and the reflection phase difference (°), which is a value obtained by subtracting the S polarization phase from the reflected P polarization phase, are δ 2 , 1 <E p / E s ≦ 3, 1 <R s1 / R p1 ≦ 3, 60 ≦ R s1 ≦ 100, 0.95 ≦ E s R s1 R p2 / E p R p1 R s2 ≦ 1.05, 90 (2n−1) −10 ≦ | δ 1 −δ 2 | ≦ 90 (2n-1) +10 (n = 1, 2) is satisfied.
　この構成によると、半導体レーザ素子から出射されたレーザ光をビームスプリッタ及び立ち上げミラーによって、Ｐ／Ｓ偏光分離した場合においても、できるだけ光量を減少させずに円偏光に変換することができ、さらに、光ディスクの複屈折の影響を低減することができる。 According to this configuration, even when the laser light emitted from the semiconductor laser element is P / S polarized light separated by the beam splitter and the rising mirror, it can be converted into circularly polarized light without reducing the amount of light as much as possible. The influence of birefringence of the optical disk can be reduced.
　また上記の光ピックアップ装置において、立ち上げミラーにおいてできるだけ光量を減少させないためには、Ｒｐ２≧９０且つＲｓ２≧９５であることが望ましい。 In the above optical pickup device, it is desirable that R p2 ≧ 90 and R s2 ≧ 95 in order to reduce the amount of light as much as possible in the rising mirror.
　また上記の光ピックアップ装置において、立ち上げミラーに入射する光のＰ／Ｓ比をできるだけ１に近づけておく観点から、０．９５≦ＥｓＲｓ１／ＥｐＲｐ１≦１．０５であることが望ましい。 In the above optical pickup device, 0.95 ≦ E s R s1 / E p R p1 ≦ 1.05 from the viewpoint of keeping the P / S ratio of the light incident on the rising mirror as close to 1 as possible. Is desirable.
　また上記の光ピックアップ装置において、前記成膜部材の具体例としては、多層誘電体膜が挙げられる。 In the above optical pickup device, a specific example of the film forming member is a multilayer dielectric film.
　本発明によると、半導体レーザ素子から出射されたレーザ光をビームスプリッタ及び立ち上げミラーによって、Ｐ／Ｓ偏光分離した場合においても、できるだけ光量を減少させずに円偏光に変換することができ、さらに、光ディスクの複屈折の影響を低減することができる。その結果、ビームスプリッタ及び立ち上げミラーに波長板の機能をもたせることができ、偏光光学系において波長板を省略することができる。したがって、部品点数を削減でき、組み立て工数の削減及び光ピックアップ装置の小型化に繋がる。さらに、光ディスクが複屈折性を有する場合でも、情報を記録／再生することができる。 According to the present invention, even when laser light emitted from a semiconductor laser element is P / S polarized light separated by a beam splitter and a rising mirror, it can be converted into circularly polarized light without reducing the amount of light as much as possible. The influence of birefringence of the optical disk can be reduced. As a result, the beam splitter and the rising mirror can have the function of a wave plate, and the wave plate can be omitted in the polarization optical system. Therefore, the number of parts can be reduced, leading to reduction in assembly man-hours and downsizing of the optical pickup device. Furthermore, even when the optical disc has birefringence, information can be recorded / reproduced.
角θが０°の場合の本発明の光ピックアップ装置の偏光光学系及び光ディスクの平面図である。It is a top view of the polarization optical system and optical disk of the optical pickup device of the present invention when the angle θ is 0 °. 角θが０°の場合の本発明の光ピックアップ装置の偏光光学系及び光ディスクの正面図である。It is a front view of the polarizing optical system and the optical disc of the optical pickup device of the present invention when the angle θ is 0 °. 角θが９０°の場合の本発明の光ピックアップ装置の偏光光学系及び光ディスクの平面図である。It is a top view of the polarization optical system of the optical pick-up apparatus of this invention in case angle | corner (theta) is 90 degrees, and an optical disk. 角θが９０°の場合の本発明の光ピックアップ装置の偏光光学系及び光ディスクの正面図である。It is a front view of the polarization optical system and the optical disc of the optical pickup device of the present invention when the angle θ is 90 °. 様々な複屈折量を有する光ディスクについて、様々な角θで円偏光を入射させた場合の復路におけるビームスプリッタの透過率を示すグラフである。It is a graph which shows the transmittance | permeability of the beam splitter in a return path | route at the time of making circularly polarized light incident on various angles (theta) about the optical disk which has various birefringence amounts. 様々な複屈折量を有する光ディスクについて、様々な角θで円偏光を入射させた場合の復路におけるビームスプリッタの透過率を示すグラフである。It is a graph which shows the transmittance | permeability of the beam splitter in a return path | route at the time of making circularly polarized light incident on various angles (theta) about the optical disk which has various birefringence amounts. 図５の一部拡大図である。FIG. 6 is a partially enlarged view of FIG. 5. 図６の一部拡大図である。FIG. 7 is a partially enlarged view of FIG. 6. 実施例１の半導体レーザ素子から出射されたレーザ光のビームスプリッタに対するＳ偏光、Ｐ偏光の強度を示す図である。It is a figure which shows the intensity | strength of S polarized light with respect to the beam splitter of the laser beam radiate | emitted from the semiconductor laser element of Example 1, and P polarized light. 実施例１のビームスプリッタで反射後のＳ偏光、Ｐ偏光の強度を示す図である。It is a figure which shows the intensity | strength of S polarized light and P polarized light after reflection with the beam splitter of Example 1. FIG. 実施例１の立ち上げミラーで反射後のＳ偏光、Ｐ偏光の強度を示す図である。It is a figure which shows the intensity | strength of S polarized light and P polarized light after reflection with the raising mirror of Example 1. FIG. 実施例１の光ディスクで反射後のＳ偏光、Ｐ偏光の強度を示す図である。It is a figure which shows the intensity | strength of S polarization after reflection with the optical disk of Example 1, and P polarization. 実施例１の戻り光の立ち上げミラーで反射後のＳ偏光、Ｐ偏光の強度を示す図である。It is a figure which shows the intensity | strength of S polarized light after reflecting with the raising mirror of the return light of Example 1, and P polarized light. 実施例１の戻り光のビームスプリッタの透過率を示す図である。It is a figure which shows the transmittance | permeability of the beam splitter of the return light of Example 1. FIG. 比較例１の光ディスクで反射後のＳ偏光、Ｐ偏光の強度を示す図である。It is a figure which shows the intensity | strength of S polarization after reflection with the optical disk of the comparative example 1, and P polarization. 比較例１の戻り光の立ち上げミラーで反射後のＳ偏光、Ｐ偏光の強度を示す図である。It is a figure which shows the intensity | strength of S polarized light after reflecting with the raising mirror of the return light of the comparative example 1, and P polarized light. 比較例１の戻り光のビームスプリッタの透過率を示す図である。It is a figure which shows the transmittance | permeability of the beam splitter of the return light of the comparative example 1. 比較例２の半導体レーザ素子から出射されたレーザ光のビームスプリッタに対するＳ偏光、Ｐ偏光の強度を示す図である。It is a figure which shows the intensity | strength of S polarized light with respect to the beam splitter of the laser beam radiate | emitted from the semiconductor laser element of the comparative example 2, and P polarized light. 比較例２の波長板を透過後のＳ偏光、Ｐ偏光の強度を示す図である。It is a figure which shows the intensity | strength of S polarized light and P polarized light after permeate | transmitting the wavelength plate of the comparative example 2. FIG. 比較例２の光ディスクで反射後のＳ偏光、Ｐ偏光の強度を示す図である。It is a figure which shows the intensity | strength of S polarization after reflection with the optical disk of the comparative example 2, and P polarization. 比較例２の戻り光の立ち上げミラーで反射後のＳ偏光、Ｐ偏光の強度を示す図である。It is a figure which shows the intensity | strength of S polarized light and P polarized light after reflecting with the raising mirror of the return light of the comparative example 2. FIG. 比較例２の戻り光の波長板を透過後のＳ偏光、Ｐ偏光の強度を示す図である。It is a figure which shows the intensity | strength of S polarized light after passing through the wave plate of the return light of the comparative example 2, and P polarized light. 比較例２の戻り光のビームスプリッタの透過率を示す図である。It is a figure which shows the transmittance | permeability of the beam splitter of the return light of the comparative example 2. 比較例３の光ディスクで反射後のＳ偏光、Ｐ偏光の強度を示す図である。It is a figure which shows the intensity | strength of S polarization after reflection with the optical disk of the comparative example 3, and P polarization. 比較例３の戻り光の立ち上げミラーで反射後のＳ偏光、Ｐ偏光の強度を示す図である。It is a figure which shows the intensity | strength of S polarized light and P polarized light after reflecting with the raising mirror of the return light of the comparative example 3. FIG. 比較例３の戻り光の波長板を透過後のＳ偏光、Ｐ偏光の強度を示す図である。It is a figure which shows the intensity | strength of S polarized light after passing through the wavelength plate of the return light of the comparative example 3, and P polarized light. 比較例３の戻り光のビームスプリッタの透過率を示す図である。It is a figure which shows the transmittance | permeability of the beam splitter of the return light of the comparative example 3.
　図１は、本発明の光ピックアップ装置の偏光光学系及び光ディスクの平面図、図２は、本発明の光ピックアップ装置の偏光光学系及び光ディスクの正面図である。 FIG. 1 is a plan view of a polarizing optical system and an optical disc of the optical pickup device of the present invention, and FIG. 2 is a front view of the polarizing optical system and optical disc of the optical pickup device of the present invention.
　光ピックアップ装置１０は、半導体レーザ素子（レーザダイオード）１１と、回折格子１２と、ビームスプリッタ１３と、コリメートレンズ１４と、立ち上げミラー１５と、対物レンズ１６と、光検出器（フォトディテクタ）１７とを備えている。 The optical pickup device 10 includes a semiconductor laser element (laser diode) 11, a diffraction grating 12, a beam splitter 13, a collimator lens 14, a rising mirror 15, an objective lens 16, and a photodetector (photodetector) 17. It has.
　半導体レーザ素子１１は、所定の偏光強度比をもった光を出射するように配設されている。この偏光強度比は後述する成膜部材の設計にも影響するので、相互の関係を最適化する必要がある。回折格子１２は、半導体レーザ素子１１から出射されたレーザ光を複数本のレーザ光に分離するものである。ビームスプリッタ１３は、回折格子１２からの複数本のレーザ光をＰ偏光とＳ偏光との間に位相差（以下ＰＳ位相差という）を発生させて反射するとともに、戻り光（光ディスク２０からの反射光）を透過するものである。 The semiconductor laser element 11 is disposed so as to emit light having a predetermined polarization intensity ratio. Since this polarization intensity ratio affects the design of the film forming member described later, it is necessary to optimize the mutual relationship. The diffraction grating 12 separates the laser beam emitted from the semiconductor laser element 11 into a plurality of laser beams. The beam splitter 13 reflects a plurality of laser beams from the diffraction grating 12 by generating a phase difference (hereinafter referred to as a PS phase difference) between P-polarized light and S-polarized light, and returns light (reflected from the optical disk 20). Light).
　コリメートレンズ１４は、ビームスプリッタ１３からの複数本のレーザ光を平行光に変換するものである。立ち上げミラー１５は、コリメートレンズ１４からの平行光をＰＳ位相差を発生させて円偏光に変換するとともに直角に折り曲げるように反射して、対物レンズ１６側へ導出するものである。対物レンズ１６は、立ち上げミラー１５で反射された光を光ディスク２０へ集光するものである。なお、光ディスク２０で反射された反射光（戻り光）は、光検出器１７で受光される。 The collimating lens 14 converts a plurality of laser beams from the beam splitter 13 into parallel light. The raising mirror 15 generates parallel light from the collimating lens 14 to convert it into circularly polarized light and reflects it so as to be bent at a right angle, and then guides it to the objective lens 16 side. The objective lens 16 collects the light reflected by the rising mirror 15 onto the optical disc 20. The reflected light (returned light) reflected by the optical disc 20 is received by the photodetector 17.
　ビームスプリッタ１３及び立ち上げミラー１５は、ガラスなどの母材の反射面に、成膜部材（不図示）としての多層誘電体膜（誘電体膜を複数層積層したもの）が蒸着などによって積層されて形成される。これにより、多層誘電体膜に入射して反射又は透過したレーザ光は、入射光に対して偏光強度及び位相差が変化する。そこで、本発明ではこの偏光強度及び位相差を制御して円偏光に変換するように設計する。この偏光強度及び位相差は多層誘電体膜の屈折率、膜厚、積層構造によって決まるので、それらの最適な組み合わせを選択することで制御できる。例えば、ＳｉＯ２とＴｉＯ２を交互に積層し、それぞれの膜厚と積層回数を最適化することで所望の偏光強度及び位相差を得ることができる。 The beam splitter 13 and the rising mirror 15 are laminated on a reflecting surface of a base material such as glass by vapor deposition or the like as a multilayer dielectric film (a plurality of dielectric films laminated) as a film forming member (not shown). Formed. Thereby, the polarization intensity and the phase difference of the laser light that is incident on the multilayer dielectric film and is reflected or transmitted changes with respect to the incident light. Therefore, the present invention is designed to control the polarization intensity and the phase difference so as to convert it into circularly polarized light. Since the polarization intensity and the phase difference are determined by the refractive index, the film thickness, and the laminated structure of the multilayer dielectric film, they can be controlled by selecting an optimal combination thereof. For example, desired polarization intensity and phase difference can be obtained by alternately laminating SiO 2 and TiO 2 and optimizing the film thickness and the number of times of lamination.
　このような構成の光ピックアップ装置１０において、手前に配置されている半導体レーザ素子１１から水平前方向へ出射されたレーザ光は、回折格子１２で複数のレーザ光に分離され、ビームスプリッタ１３で直角に折り曲げられて水平右方向へ進む。この水平右方向へ進むレーザ光は、コリメートレンズ１４で平行光にされた後、立ち上げミラー１５の反射面で反射されることにより円偏光に変換されるとともに直角に折り曲げられて鉛直上方向へ進み、対物レンズ１６を介して回転駆動される光ディスク２０の信号記録面へ集光（照射）される。これにより、光ディスク２０に対して情報の書き込み（記録）や消去を行うことができる。 In the optical pickup device 10 having such a configuration, the laser light emitted in the horizontal front direction from the semiconductor laser element 11 disposed in front is separated into a plurality of laser lights by the diffraction grating 12 and is orthogonally crossed by the beam splitter 13. It will be bent in the direction of horizontal right. The laser light traveling in the horizontal right direction is converted into parallel light by the collimator lens 14 and then converted into circularly polarized light by being reflected by the reflecting surface of the rising mirror 15, and is bent at a right angle and vertically upward. Then, the light is condensed (irradiated) onto the signal recording surface of the optical disk 20 that is rotationally driven through the objective lens 16. Thereby, information can be written (recorded) or erased on the optical disc 20.
　一方、この光ディスク２０の信号記録面からの反射光（戻り光）は、鉛直下方向へ進み、対物レンズ１６を透過し、立ち上げミラー１５の反射面で反射されることにより直角に折り曲げられて水平左方向へ進み、コリメートレンズ１４及びビームスプリッタ１３を透過して光検出器１７で検出される。これにより、光ディスク２０に記憶（記録）された情報の再生を行うことができる。 On the other hand, the reflected light (returned light) from the signal recording surface of the optical disc 20 travels vertically downward, passes through the objective lens 16, and is reflected at the reflecting surface of the rising mirror 15 to be bent at a right angle. Proceeding horizontally to the left, the light passes through the collimating lens 14 and the beam splitter 13 and is detected by the photodetector 17. Thereby, the information stored (recorded) on the optical disc 20 can be reproduced.
　光ディスク２０は様々な品質のものが流通しており、その中には信号記録面側に複屈折を有するものもある。その場合、複屈折の方向（軸）としては光ディスク２０の中心からそれぞれ半径方向へ伸びていることが多い。 Optical discs 20 of various qualities are in circulation, and some of them have birefringence on the signal recording surface side. In that case, the birefringence direction (axis) often extends in the radial direction from the center of the optical disc 20.
　ここで、本発明の目的（半導体レーザ素子１１から出射されたレーザ光をビームスプリッタ１３及び立ち上げミラー１５によって、Ｐ／Ｓ偏光分離した場合においても、できるだけ光量を減少させずに円偏光に変換するとともに、光ディスク２０の複屈折の影響を低減すること）を達成するための条件を検討する。 Here, the object of the present invention (even when the laser light emitted from the semiconductor laser element 11 is P / S polarized light separated by the beam splitter 13 and the rising mirror 15 is converted into circularly polarized light without reducing the amount of light as much as possible. And reducing the influence of birefringence of the optical disk 20).
　以下では、半導体レーザ素子１１から出射されたレーザ光のビームスプリッタ１３に対するＳ偏光、Ｐ偏光の強度をそれぞれＥｓ、Ｅｐとし、ビームスプリッタ１３でのＳ偏光、Ｐ偏光の反射率（％）をそれぞれＲｓ１、Ｒｐ１、反射後のＰ偏光位相からＳ偏光位相を引いた値である反射位相差（°）をδ１とし、立ち上げミラー１５でのＳ偏光、Ｐ偏光の反射率（％）をそれぞれＲｓ２、Ｒｐ２、反射後のＰ偏光位相からＳ偏光位相を引いた値である反射位相差（°）をδ２とする。 In the following, the intensities of S-polarized light and P-polarized light with respect to the beam splitter 13 of the laser light emitted from the semiconductor laser element 11 are E s and E p , respectively, and the reflectance (%) of the S-polarized light and P-polarized light at the beam splitter 13. R s1 and R p1 , and the reflection phase difference (°), which is a value obtained by subtracting the S polarization phase from the reflected P polarization phase, is δ 1, and the reflectance of S polarization and P polarization at the rising mirror 15 ( %) Are R s2 and R p2 , respectively, and a reflection phase difference (°) that is a value obtained by subtracting the S polarization phase from the P polarization phase after reflection is δ 2 .
　まず、ビームスプリッタ１３においてできるだけ光量を減少させないためには、高反射率を確保する必要がある。したがって、ここでは６０≦Ｒｓ１≦１００とする。そして、高反射率を確保した場合、Ｓ偏光をＰ偏光より強くするとともに、光量の減少を抑制するためにＰ／Ｓ比（偏光強度比）をある程度抑える必要がある。したがって、ここでは１＜Ｒｓ１／Ｒｐ１≦３とする。 First, in order to reduce the amount of light as much as possible in the beam splitter 13, it is necessary to ensure a high reflectance. Therefore, here, 60 ≦ R s1 ≦ 100. When a high reflectance is ensured, it is necessary to make the S-polarized light stronger than the P-polarized light and to suppress the P / S ratio (polarization intensity ratio) to some extent in order to suppress the decrease in the amount of light. Therefore, here, 1 <R s1 / R p1 ≦ 3.
　また、Ｅｓ、Ｅｐはビームスプリッタ１３で生じるＲｓ１とＲｐ１の強度比をできるだけキャンセルし、一方、往路の光量の減少を抑制するために１＜Ｅｐ／Ｅｓ≦３とする。これには、半導体レーザ素子１１を光軸に対して所定の回転角で回転させて配設すればよい。 Further, E s and E p cancel the intensity ratio of R s1 and R p1 generated in the beam splitter 13 as much as possible, while 1 <E p / E s ≦ 3 in order to suppress a decrease in the amount of light on the forward path . For this purpose, the semiconductor laser element 11 may be disposed at a predetermined rotation angle with respect to the optical axis.
　また、光ディスクに向かう光を円偏光にするための第１条件として、光ディスクに向かう光のＰ／Ｓ比を約１にする必要があるため、ここでは０．９５≦ＥｓＲｓ１Ｒｐ２／ＥｐＲｐ１Ｒｓ２≦１．０５とする。立ち上げミラー１５はビームスプリッタ１３と光を折り曲げる方向が９０°異なっているため偏光成分が入れ替わり、ＥｓＲｓ１Ｒｐ２が光ディスクに向かう光のＰ偏光強度を、ＥｐＲｐ１Ｒｓ２が光ディスクに向かう光のＳ偏光強度を表している。この数値範囲は、光ディスクの読み書きのために光ピックアップ装置に要求される仕様に基づいている。つまり、この数値範囲内であれば、光ディスクの読み書きに問題が生じない。 Further, as the first condition for making the light traveling toward the optical disk circularly polarized, the P / S ratio of the light traveling toward the optical disk needs to be about 1, so here 0.95 ≦ E s R s1 R p2 / Let E p R p1 R s2 ≦ 1.05. The rising mirror 15 differs from the beam splitter 13 by 90 ° in the direction in which the light is bent, so that the polarization component is switched, E s R s1 R p2 is the P-polarized light intensity toward the optical disc, and E p R p1 R s2 is the optical disc. Represents the S-polarized light intensity of the light traveling toward. This numerical range is based on specifications required for an optical pickup device for reading and writing of an optical disk. That is, if it is within this numerical range, there will be no problem in reading and writing of the optical disk.
　また、光ディスクに向かう光を円偏光にするための第２条件として、光ディスクに向かう光のＳ偏光とＰ偏光の位相差を約９０°にする必要があるため、ここでは９０（２ｎ－１）－１０≦｜δ１－δ２｜≦９０（２ｎ－１）＋１０　（ｎ＝１，２）とする。この数値範囲は、上述したように、光ディスクの読み書きのために光ピックアップ装置に要求される仕様に基づいている。 Further, as the second condition for making the light traveling toward the optical disc circularly polarized, the phase difference between the S-polarized light and the P-polarized light traveling toward the optical disc needs to be about 90 °, and therefore here 90 (2n−1) −10 ≦ | δ 1 −δ 2 | ≦ 90 (2n−1) +10 (n = 1, 2). As described above, this numerical range is based on specifications required for an optical pickup device for reading and writing of an optical disk.
　また、光ディスク２０の複屈折の影響を低減するための条件として、光ディスク２０への入射光が複屈折により位相差を生じても反射光のＰ／Ｓ比がほぼ１の楕円偏光（楕円軸が約４５°）となる必要がある。そこで、光ディスク２０へのレーザ光の入射点Ｐと光ディスク２０の中心点Ｏとを通る直線と、立ち上げミラー１５への入射光を光ディスク２０へ投影した直線とのなす角θが、０±１０°又は９０±１０°の範囲内になるように、偏光光学系及び光ディスク２０を配設する。 Further, as a condition for reducing the influence of the birefringence of the optical disc 20, even if the incident light to the optical disc 20 causes a phase difference due to the birefringence, the elliptically polarized light (the elliptic axis is the elliptical axis) with the reflected light having a P / S ratio of approximately 1. About 45 °). Therefore, an angle θ formed by a straight line passing through the incident point P of the laser beam on the optical disc 20 and the center point O of the optical disc 20 and a straight line obtained by projecting the incident light on the rising mirror 15 onto the optical disc 20 is 0 ± 10. The polarizing optical system and the optical disc 20 are arranged so as to be within the range of 0 ° or 90 ± 10 °.
　図１及び図２では上記の角θが０°の場合を示している。図３に、角θが９０°の場合の光ピックアップ装置の偏光光学系及び光ディスクの平面図を、図４に、角θが９０°の場合の光ピックアップ装置の偏光光学系及び光ディスクの正面図を示す。 1 and 2 show the case where the angle θ is 0 °. 3 is a plan view of the polarization optical system and the optical disc of the optical pickup device when the angle θ is 90 °, and FIG. 4 is a front view of the polarization optical system and the optical disc of the optical pickup device when the angle θ is 90 °. Indicates.
　上記の角θの範囲の根拠について図５～図８を参照して説明する。図５及び図６は、様々な複屈折量を有する光ディスクについて、様々な角θで円偏光を入射させた場合の復路におけるビームスプリッタ１３の透過率を示すグラフである。図７及び図８は、それぞれ図５及び図６の一部拡大図である。ここでのビームスプリッタ１３は、Ｐ偏光反射率が７４％、Ｓ偏光反射率が９３％のものを用いた。ビームスプリッタ１３の透過率は光ディスクの複屈折量が０°、つまり複屈折性を示さない場合を１００％とした。 The basis for the range of the angle θ will be described with reference to FIGS. FIGS. 5 and 6 are graphs showing the transmittance of the beam splitter 13 in the return path when circularly polarized light is incident at various angles θ on optical disks having various birefringence amounts. 7 and 8 are partially enlarged views of FIGS. 5 and 6, respectively. The beam splitter 13 used here has a P-polarized reflectance of 74% and an S-polarized reflectance of 93%. The transmittance of the beam splitter 13 is 100% when the birefringence amount of the optical disk is 0 °, that is, when the birefringence is not exhibited.
　戻り光のビームスプリッタ１３の透過率は、楕円偏光であることと光ディスク２０の複屈折の影響とを考慮して１００±２５％程度の範囲内である必要がある。これ以上離れると光ディスク２０の読み取りが困難になる。図５～図８は円偏光の場合を示しているので、楕円偏光との差を考慮すると、戻り光のビームスプリッタ１３の透過率は１００±２０％程度の範囲内であることが望ましい。図７、８を見ると、ビームスプリッタ１３の透過率が１００±２０％となるのは、角θが０±１０°又は９０±１０°の範囲である。よって、角θが０±１０°又は９０±１０°の範囲内であることが、光ディスク２０の複屈折の影響を低減するための条件の一つであるといえる。 The transmittance of the beam splitter 13 for the return light needs to be in the range of about 100 ± 25% in consideration of the elliptical polarization and the influence of the birefringence of the optical disk 20. If it is further away, reading of the optical disk 20 becomes difficult. 5 to 8 show the case of circularly polarized light, and considering the difference from elliptically polarized light, it is desirable that the transmittance of the beam splitter 13 for returning light is in the range of about 100 ± 20%. 7 and 8, the transmittance of the beam splitter 13 is 100 ± 20% when the angle θ is in the range of 0 ± 10 ° or 90 ± 10 °. Therefore, it can be said that the angle θ within the range of 0 ± 10 ° or 90 ± 10 ° is one of the conditions for reducing the influence of the birefringence of the optical disc 20.
　上記の条件を全て満たすことにより、本発明の目的（半導体レーザ素子１１から出射されたレーザ光をビームスプリッタ１３及び立ち上げミラー１５によって、Ｐ／Ｓ偏光分離した場合においても、できるだけ光量を減少させずに円偏光に変換するとともに、光ディスク２０の複屈折の影響を低減すること）を達成することができる。 By satisfying all the above conditions, the object of the present invention is to reduce the amount of light as much as possible even when the laser light emitted from the semiconductor laser element 11 is P / S polarized light separated by the beam splitter 13 and the rising mirror 15. Without reducing the influence of the birefringence of the optical disc 20).
　その結果、ビームスプリッタ１３及び立ち上げミラー１５に波長板の機能をもたせることができ、偏光光学系において波長板を省略することができる。したがって、部品点数を削減でき、組み立て工数の削減及び光ピックアップ装置の小型化に繋がる。また、複屈折を有する光ディスクに対しても正常に読み書きすることができる。 As a result, the beam splitter 13 and the rising mirror 15 can have the function of a wave plate, and the wave plate can be omitted in the polarization optical system. Therefore, the number of parts can be reduced, leading to reduction in assembly man-hours and downsizing of the optical pickup device. Moreover, it is possible to read / write normally even for an optical disc having birefringence.
　なお、立ち上げミラー１５においてできるだけ光量を減少させないためには、Ｒｐ２≧９０且つＲｓ２≧９５であることが望ましい。また、立ち上げミラー１５に入射する光のＰ／Ｓ比をできるだけ１に近づけておく観点から、０．９５≦ＥｓＲｓ１／ＥｐＲｐ１≦１．０５であることが望ましい。 Note that it is desirable that R p2 ≧ 90 and R s2 ≧ 95 so as not to reduce the light amount as much as possible in the rising mirror 15. Further, from the viewpoint of keeping the P / S ratio of the light incident on the rising mirror 15 as close to 1 as possible, it is desirable that 0.95 ≦ E s R s1 / E p R p1 ≦ 1.05.
　以下、上記の光ピックアップ装置１０の実施例と、比較例とについて説明する。 Hereinafter, examples of the optical pickup device 10 and comparative examples will be described.
　実施例１では、Ｅｐ：Ｅｓ＝５：４となるように半導体レーザ素子１１を配設し、波長板は設けず、角θ＝０（°）とする。ビームスプリッタ１３の成膜部材としては、母材側から順に、223.56nm厚のＳｉＯ２、25.00nm厚のＴａ２Ｏ５、58.89nm厚のＳｉＯ２、79.4nm厚のＴａ２Ｏ５、57.87nm厚のＳｉＯ２、25.00nm厚のＴａ２Ｏ５、30.00nm厚のＳｉＯ２、25.00nm厚のＴａ２Ｏ５、89.21nm厚のＳｉＯ２、42.03nm厚のＴａ２Ｏ５、288.95nm厚のＳｉＯ２、178.05nm厚のＴａ２Ｏ５、44.18nm厚のＳｉＯ２、190.76nm厚のＴａ２Ｏ５、246.13nm厚のＳｉＯ２、146.30nm厚のＴａ２Ｏ５、271.39nm厚のＳｉＯ２、42.00nm厚のＴａ２Ｏ５、265.51nm厚のＳｉＯ２、56.58nm厚のＴａ２Ｏ５、226.48nm厚のＳｉＯ２、66.76nm厚のＴａ２Ｏ５、175.13nm厚のＳｉＯ２、76.17nm厚のＴａ２Ｏ５、156.12nm厚のＳｉＯ２、81.05nm厚のＴａ２Ｏ５、146.54nm厚のＳｉＯ２、91.43nm厚のＴａ２Ｏ５、64.04nm厚のＳｉＯ２、101.60nm厚のＴａ２Ｏ５、70.34nm厚のＳｉＯ２、25.00nm厚のＴａ２Ｏ５、256.59nm厚のＳｉＯ２、52.17nm厚のＴａ２Ｏ５、187.34nm厚のＳｉＯ２からなる３５層を積層して形成する。５５０ｎｍの光に対するＳｉＯ２の屈折率は１．４４５、同じくＴａ２Ｏ５の屈折率は２．２２５である。そして、Ｒｓ１＝９３（％）、Ｒｐ１＝７４（％）、δ１＝２１０（°）である。 In the first embodiment, the semiconductor laser element 11 is arranged so that E p : E s = 5: 4, the wave plate is not provided, and the angle θ = 0 (°). As the film forming member of the beam splitter 13, in order from the base material side, 223.56 nm thick SiO 2 , 25.00 nm thick Ta 2 O 5 , 58.89 nm thick SiO 2 , 79.4 nm thick Ta 2 O 5 , 57.87 nm Thick SiO 2 , 25.00 nm thick Ta 2 O 5 , 30.00 nm thick SiO 2 , 25.00 nm thick Ta 2 O 5 , 89.21 nm thick SiO 2 , 42.03 nm thick Ta 2 O 5 , 288.95 nm thick SiO 2 , 178.05 nm thick Ta 2 O 5 , 44.18 nm thick SiO 2 , 190.76 nm thick Ta 2 O 5 , 246.13 nm thick SiO 2 , 146.30 nm thick Ta 2 O 5 , 271.39 nm thick SiO 2 42.00 nm thick Ta 2 O 5 , 265.51 nm thick SiO 2 , 56.58 nm thick Ta 2 O 5 , 226.48 nm thick SiO 2 , 66.76 nm thick Ta 2 O 5 , 175.13 nm thick SiO 2 , 76.17 nm thick Ta 2 O 5, SiO 2 of 156.12nm thickness, Ta 2 O 5 of 81.05nm thickness, SiO 2 of 146.54nm thickness of 91.43nm thickness Ta 2 O , SiO 2 of 64.04nm thickness, 101.60Nm thickness of Ta 2 O 5, SiO 2 of 70.34nm thickness, 25.00Nm thickness of Ta 2 O 5, SiO 2 of 256.59nm thickness, Ta 2 O 5 of 52.17nm thickness, 187.34 It is formed by stacking 35 layers of SiO 2 with a thickness of nm. The refractive index of SiO 2 for 550 nm light is 1.445, and the refractive index of Ta 2 O 5 is 2.225. R s1 = 93 (%), R p1 = 74 (%), and δ 1 = 210 (°).
　また、立ち上げミラー１５の成膜部材としては、母材側から順に、85.15nm厚のＴａ２Ｏ５、137.06nm厚のＳｉＯ２、84.69nm厚のＴａ２Ｏ５、136.21nm厚のＳｉＯ２、84.78nm厚のＴａ２Ｏ５、133.91nm厚のＳｉＯ２、84.16nm厚のＴａ２Ｏ５、124.73nm厚のＳｉＯ２、76.02nm厚のＴａ２Ｏ５、85.21nm厚のＳｉＯ２、66.87nm厚のＴａ２Ｏ５、116.66nm厚のＳｉＯ２、84.77nm厚のＴａ２Ｏ５、134.24nm厚のＳｉＯ２、86.17nm厚のＴａ２Ｏ５、138.68nm厚のＳｉＯ２、86.09nm厚のＴａ２Ｏ５、139.52nm厚のＳｉＯ２、87.07nm厚のＴａ２Ｏ５、140.14nm厚のＳｉＯ２、88.33nm厚のＴａ２Ｏ５、142.28nm厚のＳｉＯ２、105.65nm厚のＴａ２Ｏ５、203.83nm厚のＳｉＯ２、104.04nm厚のＴａ２Ｏ５、143.38nm厚のＳｉＯ２、92.98nm厚のＴａ２Ｏ５、149.59nm厚のＳｉＯ２、99.64nm厚のＴａ２Ｏ５、168.28nm厚のＳｉＯ２、103.50nm厚のＴａ２Ｏ５、164.41nm厚のＳｉＯ２、102.83nm厚のＴａ２Ｏ５、182.77nm厚のＳｉＯ２、129.30nm厚のＴａ２Ｏ５、195.51nm厚のＳｉＯ２、109.00nm厚のＴａ２Ｏ５、86.39nm厚のＳｉＯ２からなる３８層を積層して形成する。そして、Ｒｓ２＝９９（％）、Ｒｐ２＝９９（％）、δ２＝－１２０（°）である。 Further, as the film forming member of the rising mirror 15, in order from the base material side, 85.15 nm thick Ta 2 O 5 , 137.06 nm thick SiO 2 , 84.69 nm thick Ta 2 O 5 , 136.21 nm thick SiO 2. 84.78 nm thick Ta 2 O 5 , 133.91 nm thick SiO 2 , 84.16 nm thick Ta 2 O 5 , 124.73 nm thick SiO 2 , 76.02 nm thick Ta 2 O 5 , 85.21 nm thick SiO 2 , 66.87 nm thick Ta 2 O 5, SiO 2 of 116.66nm thickness, 84.77Nm thickness of Ta 2 O 5, SiO 2 of 134.24nm thickness, Ta 2 O 5 of 86.17nm thickness, SiO 2 of 138.68nm thickness, 86.09Nm thickness Ta 2 O 5 , 139.52 nm thick SiO 2 , 87.07 nm thick Ta 2 O 5 , 140.14 nm thick SiO 2 , 88.33 nm thick Ta 2 O 5 , 142.28 nm thick SiO 2 , 105.65 nm thick Ta 2 O 5, SiO 2 of 203.83nm thickness, 104.04Nm thickness of Ta 2 O 5, SiO 2 of 143.38nm thickness, 92.98Nm thickness of Ta 2 O 5, of 149.59nm thickness iO 2, 99.64nm thickness of Ta 2 O 5, SiO 2 of 168.28nm thickness, 103.50Nm thickness of Ta 2 O 5, SiO 2 of 164.41nm thickness, Ta 2 O 5 of 102.83nm thickness, 182.77Nm thickness of SiO 2 , 129.30 nm thick Ta 2 O 5 , 195.51 nm thick SiO 2 , 109.00 nm thick Ta 2 O 5 , and 86.39 nm thick SiO 2 . R s2 = 99 (%), R p2 = 99 (%), and δ 2 = −120 (°).
　図９は、半導体レーザ素子１１から出射されたレーザ光のビームスプリッタ１３に対するＳ偏光、Ｐ偏光の強度（Ｅｓ、Ｅｐ）を示す図である。Ｅｐ：Ｅｓ＝５：４となっていることがわかる。 FIG. 9 is a diagram showing the intensity (E s , E p ) of S-polarized light and P-polarized light with respect to the beam splitter 13 of the laser light emitted from the semiconductor laser element 11. It can be seen that E p : E s = 5: 4.
　図１０は、ビームスプリッタ１３で反射後のＳ偏光、Ｐ偏光の強度を示す図である。Ｐ／Ｓ比はほぼ１であり、楕円偏光になっていることがわかる。 FIG. 10 is a diagram showing the intensity of S-polarized light and P-polarized light after being reflected by the beam splitter 13. It can be seen that the P / S ratio is approximately 1, indicating elliptically polarized light.
　図１１は、立ち上げミラー１５で反射後のＳ偏光、Ｐ偏光の強度を示す図である。Ｐ／Ｓ比はほぼ１であり、ほぼ円偏光になっていることがわかる。 FIG. 11 is a diagram showing the intensity of S-polarized light and P-polarized light after being reflected by the rising mirror 15. It can be seen that the P / S ratio is approximately 1, indicating that the light is approximately circularly polarized.
　図１２は、光ディスク２０で反射後のＳ偏光、Ｐ偏光の強度を示す図である。Ｐ／Ｓ比はほぼ１であり、楕円偏光になっていることがわかる。楕円の長軸は４５°又は１３５°となっており、Ｐ／Ｓ比は光ディスクの複屈折量に依存しない。一方、楕円偏光の楕円率は光ディスク２０の複屈折量に依存する。 FIG. 12 is a diagram showing the intensity of S-polarized light and P-polarized light after being reflected by the optical disk 20. It can be seen that the P / S ratio is approximately 1, indicating elliptically polarized light. The major axis of the ellipse is 45 ° or 135 °, and the P / S ratio does not depend on the birefringence amount of the optical disc. On the other hand, the ellipticity of elliptically polarized light depends on the amount of birefringence of the optical disk 20.
　図１３は、戻り光の立ち上げミラー１５で反射後のＳ偏光、Ｐ偏光の強度を示す図である。Ｐ／Ｓ比はほぼ１であり、楕円偏光になっていることがわかる。楕円の長軸は４５°又は１３５°となっており、Ｐ／Ｓ比は光ディスクの複屈折量に依存しない。一方、楕円偏光の楕円率は光ディスク２０の複屈折量に依存する。 FIG. 13 is a diagram showing the intensity of S-polarized light and P-polarized light after being reflected by the rising mirror 15 for returning light. It can be seen that the P / S ratio is approximately 1, indicating elliptically polarized light. The major axis of the ellipse is 45 ° or 135 °, and the P / S ratio does not depend on the birefringence amount of the optical disc. On the other hand, the ellipticity of elliptically polarized light depends on the amount of birefringence of the optical disk 20.
　図１４は、戻り光のビームスプリッタ１３の透過率を示す図である。戻り光のビームスプリッタ１３の透過率は、ビームスプリッタ１３に入射する戻り光のＰ／Ｓ比がほぼ１であるため、光ディスクの複屈折量によって生じるＳ偏光とＰ偏光の位相差に影響されず、常に約１６．５％となっている。 FIG. 14 is a diagram showing the transmittance of the return beam through the beam splitter 13. The transmittance of the return light beam splitter 13 is not affected by the phase difference between the S-polarized light and the P-polarized light caused by the amount of birefringence of the optical disk because the P / S ratio of the returned light incident on the beam splitter 13 is approximately 1. It is always about 16.5%.
　このように、波長板を設けず、角θ＝０（°）とすることにより、ビームスプリッタ１３へ入射する戻り光のＰ／Ｓ比がほぼ１となるので、ビームスプリッタ１３の透過率が光ディスクの複屈折量の影響を受けずにほぼ一定となる。よって、光ディスクが複屈折を有する場合でも読み取り可能となる。なお、角θ＝９０（°）の場合も同様である。 In this way, by setting the angle θ = 0 (°) without providing the wave plate, the P / S ratio of the return light incident on the beam splitter 13 becomes approximately 1, so that the transmittance of the beam splitter 13 is the optical disc. It is almost constant without being affected by the amount of birefringence. Therefore, even when the optical disc has birefringence, reading is possible. The same applies to the angle θ = 90 (°).
比較例１Comparative Example 1
　比較例１では角θ＝４５（°）とし、その他の構成は実施例１と同様とする。したがって、図９～図１１は比較例１でも同様である。 In Comparative Example 1, the angle θ is 45 (°), and other configurations are the same as in Example 1. Therefore, FIGS. 9 to 11 are the same in the first comparative example.
　図１５は、光ディスク２０で反射後のＳ偏光、Ｐ偏光の強度を示す図である。楕円偏光になっていることがわかる。楕円の長軸はＳ又はＰ方向となっており、Ｐ／Ｓ比、楕円偏光の楕円率ともに光ディスク２０の複屈折量に依存する。 FIG. 15 is a diagram showing the intensity of S-polarized light and P-polarized light after being reflected by the optical disc 20. It turns out that it becomes elliptically polarized light. The major axis of the ellipse is in the S or P direction, and both the P / S ratio and the ellipticity of elliptically polarized light depend on the birefringence amount of the optical disc 20.
　図１６は、戻り光の立ち上げミラー１５で反射後のＳ偏光、Ｐ偏光の強度を示す図である。楕円偏光になっていることがわかる。Ｐ／Ｓ比、楕円偏光の楕円率ともに光ディスク２０の複屈折量に依存する。 FIG. 16 is a diagram showing the intensity of S-polarized light and P-polarized light after being reflected by the rising mirror 15 for returning light. It turns out that it becomes elliptically polarized light. Both the P / S ratio and the ellipticity of elliptically polarized light depend on the birefringence amount of the optical disk 20.
　図１７は、戻り光のビームスプリッタ１３の透過率を示す図である。戻り光のビームスプリッタ１３の透過率は、ビームスプリッタ１３に入射する戻り光のＰ／Ｓ比が１から大きくずれているため、光ディスクの複屈折量によって生じるＳ偏光とＰ偏光の位相差に影響される。 FIG. 17 is a diagram showing the transmittance of the beam splitter 13 for returning light. The transmittance of the return light beam splitter 13 is affected by the phase difference between the S-polarized light and the P-polarized light caused by the amount of birefringence of the optical disk because the P / S ratio of the returned light incident on the beam splitter 13 is greatly deviated from 1. Is done.
　このように、波長板を設けず、角θ＝４５（°）とすることにより、ビームスプリッタ１３へ入射する戻り光のＰ／Ｓ比が１から大きくずれるため、ビームスプリッタ１３の透過率が光ディスクの複屈折量の影響を受ける。よって、光ディスクが複屈折を有する場合に読み取り不可能となる。 In this way, by setting the angle θ = 45 (°) without providing the wave plate, the P / S ratio of the return light incident on the beam splitter 13 is greatly deviated from 1, so that the transmittance of the beam splitter 13 is the optical disc. Affected by the amount of birefringence. Therefore, reading becomes impossible when the optical disc has birefringence.
比較例２Comparative Example 2
　比較例２では、Ｅｐ：Ｅｓ＝０：１となるように半導体レーザ素子１１を配設し、ビームスプリッタ１３と立ち上げミラー１５の間に波長板を設け、角θ＝０（°）とする。ビームスプリッタ１３の構成は実施例１と同様であり、立ち上げミラー１５の構成は実施例１と異なる。 In Comparative Example 2, the semiconductor laser element 11 is arranged so that E p : E s = 0: 1, a wave plate is provided between the beam splitter 13 and the rising mirror 15, and an angle θ = 0 (°). And The configuration of the beam splitter 13 is the same as that of the first embodiment, and the configuration of the rising mirror 15 is different from that of the first embodiment.
　立ち上げミラー１５の成膜部材としては、母材側から順に、84.5nm厚のＴａ２Ｏ５、138.25nm厚のＳｉＯ２、85.07nm厚のＴａ２Ｏ５、138.79nm厚のＳｉＯ２、85.26nm厚のＴａ２Ｏ５、138.46nm厚のＳｉＯ２、85.44nm厚のＴａ２Ｏ５、135.70nm厚のＳｉＯ２、84.31nm厚のＴａ２Ｏ５、89.02nm厚のＳｉＯ２、48.50nm厚のＴａ２Ｏ５、116.78nm厚のＳｉＯ２、85.23nm厚のＴａ２Ｏ５、136.82nm厚のＳｉＯ２、85.54nm厚のＴａ２Ｏ５、138.66nm厚のＳｉＯ２、85.42nm厚のＴａ２Ｏ５、138.65nm厚のＳｉＯ２、85.32nm厚のＴａ２Ｏ５、137.24nm厚のＳｉＯ２、84.64nm厚のＴａ２Ｏ５、129.54nm厚のＳｉＯ２、74.07nm厚のＴａ２Ｏ５、305.98nm厚のＳｉＯ２、80.16nm厚のＴａ２Ｏ５、129.10nm厚のＳｉＯ２、82.66nm厚のＴａ２Ｏ５、130.43nm厚のＳｉＯ２、83.04nm厚のＴａ２Ｏ５、218.17nm厚のＳｉＯ２、108.63nm厚のＴａ２Ｏ５、124.77nm厚のＳｉＯ２、75.74nm厚のＴａ２Ｏ５、115.76nm厚のＳｉＯ２、169.33nm厚のＴａ２Ｏ５、205.04nm厚のＳｉＯ２、71.63nm厚のＴａ２Ｏ５、145.70nm厚のＳｉＯ２からなる３８層を積層して形成する。そして、Ｒｓ２＝９９（％）、Ｒｐ２＝９９（％）、δ２＝１８０（°）である。 As the film forming member of the rising mirror 15, in order from the base material side, 84.5 nm thick Ta 2 O 5 , 138.25 nm thick SiO 2 , 85.07 nm thick Ta 2 O 5 , 138.79 nm thick SiO 2 , 85.26. nm thick Ta 2 O 5, SiO 2 of 138.46nm thickness, 85.44Nm thickness of Ta 2 O 5, SiO 2 of 135.70nm thickness, Ta 2 O 5 of 84.31nm thickness, SiO 2 of 89.02nm thickness, 48.50Nm thickness Ta 2 O 5 , 116.78 nm thick SiO 2 , 85.23 nm thick Ta 2 O 5 , 136.82 nm thick SiO 2 , 85.54 nm thick Ta 2 O 5 , 138.66 nm thick SiO 2 , 85.42 nm thick Ta 2 O 5 , 138.65 nm thick SiO 2 , 85.32 nm thick Ta 2 O 5 , 137.24 nm thick SiO 2 , 84.64 nm thick Ta 2 O 5 , 129.54 nm thick SiO 2 , 74.07 nm thick Ta 2 O 5 , 305.98 nm thick SiO 2 , 80.16 nm thick Ta 2 O 5 , 129.10 nm thick SiO 2 , 82.66 nm thick Ta 2 O 5 , 130.43 nm thick SiO 2 83.04 nm thick Ta 2 O 5 , 218.17 nm thick SiO 2 , 108.63 nm thick Ta 2 O 5 , 124.77 nm thick SiO 2 , 75.74 nm thick Ta 2 O 5 , 115.76 nm thick SiO 2 , 169.33 38 layers of Ta 2 O 5 with a thickness of nm, SiO 2 with a thickness of 205.04 nm, Ta 2 O 5 with a thickness of 71.63 nm, and SiO 2 with a thickness of 145.70 nm are stacked. R s2 = 99 (%), R p2 = 99 (%), and δ 2 = 180 (°).
　図１８は、半導体レーザ素子１１から出射されたレーザ光のビームスプリッタ１３に対するＳ偏光、Ｐ偏光の強度（Ｅｓ、Ｅｐ）を示す図である。Ｅｐ：Ｅｓ＝０：１のＳ偏光となっていることがわかる。ビームスプリッタ１３で反射後のＳ偏光、Ｐ偏光の強度も図１８と同様である。 FIG. 18 is a diagram showing the intensity (E s , E p ) of S-polarized light and P-polarized light with respect to the beam splitter 13 of the laser light emitted from the semiconductor laser element 11. It can be seen that the S polarization is E p : E s = 0: 1. The intensities of S-polarized light and P-polarized light after being reflected by the beam splitter 13 are the same as those in FIG.
　図１９は、波長板を透過後のＳ偏光、Ｐ偏光の強度を示す図である。４５°方向に軸を有する波長板へ入射した光は、４５°方向と１３５°方向に位相差を受け、Ｐ／Ｓ比はほぼ１であり、ほぼ円偏光になっていることがわかる。立ち上げミラー１５で反射後のＳ偏光、Ｐ偏光の強度も図１９と同様である。 FIG. 19 is a diagram showing the intensity of S-polarized light and P-polarized light after passing through the wave plate. It can be seen that light incident on a wave plate having an axis in the 45 ° direction undergoes a phase difference between the 45 ° direction and the 135 ° direction, has a P / S ratio of approximately 1, and is substantially circularly polarized. The intensities of S-polarized light and P-polarized light after being reflected by the rising mirror 15 are the same as those in FIG.
　図２０は、光ディスク２０で反射後のＳ偏光、Ｐ偏光の強度を示す図である。Ｐ／Ｓ比はほぼ１であり、楕円偏光になっていることがわかる。Ｐ／Ｓ比は光ディスクの複屈折量に依存しない。一方、楕円偏光の楕円率は光ディスク２０の複屈折量に依存する。 FIG. 20 is a diagram showing the intensity of S-polarized light and P-polarized light after being reflected by the optical disc 20. It can be seen that the P / S ratio is approximately 1, indicating elliptically polarized light. The P / S ratio does not depend on the birefringence amount of the optical disk. On the other hand, the ellipticity of elliptically polarized light depends on the amount of birefringence of the optical disk 20.
　図２１は、戻り光の立ち上げミラー１５で反射後のＳ偏光、Ｐ偏光の強度を示す図である。Ｐ／Ｓ比はほぼ１であり、楕円偏光になっていることがわかる。Ｐ／Ｓ比は光ディスクの複屈折量に依存しない。一方、楕円偏光の楕円率は光ディスク２０の複屈折量に依存する。 FIG. 21 is a diagram showing the intensity of S-polarized light and P-polarized light after being reflected by the rising mirror 15 for returning light. It can be seen that the P / S ratio is approximately 1, indicating elliptically polarized light. The P / S ratio does not depend on the birefringence amount of the optical disk. On the other hand, the ellipticity of elliptically polarized light depends on the amount of birefringence of the optical disk 20.
　図２２は、戻り光の波長板を透過後のＳ偏光、Ｐ偏光の強度を示す図である。波長板へ入射した光は、４５°方向と１３５°方向に位相差を受け、直線偏光になっていることがわかる。Ｐ／Ｓ比は光ディスク２０の複屈折量に依存する。 FIG. 22 is a diagram showing the intensity of S-polarized light and P-polarized light after passing through the wave plate of the return light. It can be seen that the light incident on the wave plate undergoes a phase difference in the 45 ° direction and the 135 ° direction and is linearly polarized light. The P / S ratio depends on the birefringence amount of the optical disc 20.
　図２３は、戻り光のビームスプリッタ１３の透過率を示す図である。戻り光のビームスプリッタ１３の透過率は、ビームスプリッタ１３に入射する戻り光のＰ／Ｓ比が１から大きくずれているため、光ディスクの複屈折量によって生じるＳ偏光とＰ偏光の位相差に影響される。 FIG. 23 is a diagram showing the transmittance of the beam splitter 13 for returning light. The transmittance of the return light beam splitter 13 is affected by the phase difference between the S-polarized light and the P-polarized light caused by the amount of birefringence of the optical disk because the P / S ratio of the returned light incident on the beam splitter 13 is greatly deviated from 1. Is done.
　このように、波長板を設け、角θ＝０（°）とすることにより、ビームスプリッタ１３へ入射する戻り光のＰ／Ｓ比が１から大きくずれるため、ビームスプリッタ１３の透過率が光ディスクの複屈折量の影響を受ける。よって、光ディスクが複屈折を有する場合に読み取り不可能となる。 In this way, by providing the wave plate and setting the angle θ = 0 (°), the P / S ratio of the return light incident on the beam splitter 13 is greatly deviated from 1, so that the transmittance of the beam splitter 13 is the same as that of the optical disk. It is affected by the amount of birefringence. Therefore, reading becomes impossible when the optical disc has birefringence.
比較例３Comparative Example 3
　比較例３は、比較例２において角θ＝４５（°）としたものである。したがって、図１８、図１９は比較例３でも同様である。 Comparative Example 3 is the same as Comparative Example 2 except that the angle θ = 45 (°). Accordingly, FIGS. 18 and 19 are the same in the third comparative example.
　図２４は、光ディスク２０で反射後のＳ偏光、Ｐ偏光の強度を示す図である。Ｐ／Ｓ比はほぼ１であり、楕円偏光になっていることがわかる。Ｐ／Ｓ比は光ディスクの複屈折量に依存しない。一方、楕円偏光の楕円率は光ディスク２０の複屈折量に依存する。 FIG. 24 is a diagram showing the intensity of S-polarized light and P-polarized light after being reflected by the optical disc 20. It can be seen that the P / S ratio is approximately 1, indicating elliptically polarized light. The P / S ratio does not depend on the birefringence amount of the optical disk. On the other hand, the ellipticity of elliptically polarized light depends on the amount of birefringence of the optical disk 20.
　図２５は、戻り光の立ち上げミラー１５で反射後のＳ偏光、Ｐ偏光の強度を示す図である。Ｐ／Ｓ比はほぼ１であり、楕円偏光になっていることがわかる。Ｐ／Ｓ比は光ディスクの複屈折量に依存しない。一方、楕円偏光の楕円率は光ディスク２０の複屈折量に依存する。 FIG. 25 is a diagram showing the intensity of S-polarized light and P-polarized light after being reflected by the rising mirror 15 for returning light. It can be seen that the P / S ratio is approximately 1, indicating elliptically polarized light. The P / S ratio does not depend on the birefringence amount of the optical disk. On the other hand, the ellipticity of elliptically polarized light depends on the amount of birefringence of the optical disk 20.
　図２６は、戻り光の波長板を透過後のＳ偏光、Ｐ偏光の強度を示す図である。波長板へ入射した光は、４５°方向と１３５°方向に位相差を受け、Ｓ又はＰ方向に長軸を有する楕円偏光になっていることがわかる。Ｐ／Ｓ比は光ディスク２０の複屈折量に依存する。 FIG. 26 is a diagram showing the intensity of S-polarized light and P-polarized light after passing through the wave plate of the return light. It can be seen that the light incident on the wave plate is subjected to a phase difference in the 45 ° direction and the 135 ° direction and is elliptically polarized light having a major axis in the S or P direction. The P / S ratio depends on the birefringence amount of the optical disc 20.
　図２７は、戻り光のビームスプリッタ１３の透過率を示す図である。戻り光のビームスプリッタ１３の透過率は、ビームスプリッタ１３に入射する戻り光のＰ／Ｓ比が１から大きくずれているため、光ディスクの複屈折量によって生じるＳ偏光とＰ偏光の位相差に影響される。 FIG. 27 is a diagram showing the transmittance of the beam splitter 13 for returning light. The transmittance of the return light beam splitter 13 is affected by the phase difference between the S-polarized light and the P-polarized light caused by the amount of birefringence of the optical disk because the P / S ratio of the returned light incident on the beam splitter 13 is greatly deviated from 1. Is done.
　このように、波長板を設け、角θ＝４５（°）とすることにより、ビームスプリッタ１３へ入射する戻り光のＰ／Ｓ比が１から大きくずれるため、ビームスプリッタ１３の透過率が光ディスクの複屈折量の影響を受ける。よって、光ディスクが複屈折を有する場合に読み取り不可能となる。 In this way, by providing the wave plate and setting the angle θ = 45 (°), the P / S ratio of the return light incident on the beam splitter 13 is greatly deviated from 1, so that the transmittance of the beam splitter 13 is the same as that of the optical disk. It is affected by the amount of birefringence. Therefore, reading becomes impossible when the optical disc has birefringence.
　なお、多層誘電体膜として、ＳｉＯ２に替えて、例えば、ＭｇＦ２、ＡＬ２Ｏ３等であってもよく、Ｔａ２Ｏ５に替えて、例えば、Ｎｂ２Ｏ５、ＴｉＯ２、Ｌａ２Ｏ３とＴｉＯ２の混合物等であってもよい。 Incidentally, as a multilayer dielectric film, in place of SiO 2, for example, may be MgF 2, AL 2 O 3, etc., in place of the Ta 2 O 5, for example, Nb 2 O 5, TiO 2 , La 2 It may be a mixture of O 3 and TiO 2 or the like.
　本発明の光ピックアップ装置は、ＢＤ、ＤＶＤ、ＣＤなどの光ディスクの記録・再生に利用することができる。 The optical pickup device of the present invention can be used for recording / reproduction of optical disks such as BD, DVD, and CD.
　　　１０　　光ピックアップ装置
　　　１１　　半導体レーザ素子
　　　１３　　ビームスプリッタ
　　　１５　　立ち上げミラー
　　　１７　　光検出器
　　　２０　　光ディスク DESCRIPTION OF SYMBOLS 10 Optical pick-up apparatus 11 Semiconductor laser element 13 Beam splitter 15 Rising mirror 17 Photo detector 20 Optical disk

Claims (4)

  1. 　半導体レーザ素子から出射されたレーザ光を偏光光学系を介して光ディスクの信号記録面に集光し、該信号記録面からの戻り光を前記偏光光学系を介して光検出器で検出する光ピックアップ装置において、
    　前記半導体レーザ素子を所定の偏光強度比をもった光を出射するように配設し、
    　前記偏光光学系に含まれるビームスプリッタ及び立ち上げミラーに、前記レーザ光の入射光に対して偏光強度及び位相差を制御して円偏光に変換する成膜部材を設け、
    　光ディスクへのレーザ光の入射点と光ディスクの中心点とを通る直線と、立ち上げミラーへの入射光を光ディスクへ投影した直線とのなす角が、０±１０°又は９０±１０°の範囲内になるように、前記偏光光学系及び光ディスクを配設し、
    　前記半導体レーザ素子から出射されたレーザ光の前記ビームスプリッタに対するＳ偏光、Ｐ偏光の強度をそれぞれＥｓ、Ｅｐとし、
    　前記ビームスプリッタでのＳ偏光、Ｐ偏光の反射率（％）をそれぞれＲｓ１、Ｒｐ１、反射後のＰ偏光位相からＳ偏光位相を引いた値である反射位相差（°）をδ１とし、
    　前記立ち上げミラーでのＳ偏光、Ｐ偏光の反射率（％）をそれぞれＲｓ２、Ｒｐ２、反射後のＰ偏光位相からＳ偏光位相を引いた値である反射位相差（°）をδ２とした場合、
    　１＜Ｅｐ／Ｅｓ≦３、
    　１＜Ｒｓ１／Ｒｐ１≦３、
    　６０≦Ｒｓ１≦１００、
    　０．９５≦ＥｓＲｓ１Ｒｐ２／ＥｐＲｐ１Ｒｓ２≦１．０５、
    　９０（２ｎ－１）－１０≦｜δ１－δ２｜≦９０（２ｎ－１）＋１０　（ｎ＝１，２）
    　を満たすことを特徴とする光ピックアップ装置。     An optical pickup that condenses laser light emitted from a semiconductor laser element on a signal recording surface of an optical disc through a polarization optical system and detects return light from the signal recording surface by a photodetector through the polarization optical system. In the device
    The semiconductor laser element is disposed so as to emit light having a predetermined polarization intensity ratio,
    The beam splitter and the rising mirror included in the polarization optical system are provided with a film forming member that converts the polarization intensity and phase difference of the incident light of the laser light into circularly polarized light,
    An angle formed by a straight line passing through the incident point of the laser beam on the optical disc and the central point of the optical disc and a straight line obtained by projecting the incident light on the rising mirror onto the optical disc is within a range of 0 ± 10 ° or 90 ± 10 °. The polarizing optical system and the optical disk are arranged so that
    Intensities of S-polarized light and P-polarized light with respect to the beam splitter of the laser light emitted from the semiconductor laser element are denoted as E s and E p , respectively.
    The reflectance (%) of S-polarized light and P-polarized light at the beam splitter is R s1 and R p1 , respectively, and the reflection phase difference (°) that is a value obtained by subtracting the S-polarized phase from the reflected P-polarized phase is δ 1. ,
    The reflectance (%) of S-polarized light and P-polarized light at the rising mirror is R s2 and R p2 , respectively, and the reflection phase difference (°) that is a value obtained by subtracting the S-polarized phase from the reflected P-polarized phase is δ 2. If
    1 <E p / E s ≦ 3,
    1 <R s1 / R p1 ≦ 3,
    60 ≦ R s1 ≦ 100,
    0.95 ≦ E s R s1 R p2 / E p R p1 R s2 ≦ 1.05,
    90 (2n-1) -10 ≦ | δ 1 −δ 2 | ≦ 90 (2n−1) +10 (n = 1, 2)
    An optical pickup device satisfying the requirements.
  2. 　Ｒｐ２≧９０且つＲｓ２≧９５であることを特徴とする請求項１記載の光ピックアップ装置。 2. The optical pickup device according to claim 1, wherein R p2 ≧ 90 and R s2 ≧ 95.
  3. 　０．９５≦ＥｓＲｓ１／ＥｐＲｐ１≦１．０５であることを特徴とする請求項２記載の光ピックアップ装置。 The optical pickup device according to claim 2, wherein 0.95 ≦ E s R s1 / E p R p1 ≦ 1.05.
  4. 　前記成膜部材は多層誘電体膜であることを特徴とする請求項１～３の何れかに記載の光ピックアップ装置。 4. The optical pickup apparatus according to claim 1, wherein the film forming member is a multilayer dielectric film.
PCT/JP2011/071200 2010-10-27 2011-09-16 Optical pickup device WO2012056827A1 (en)

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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH01137435A (en) * 1987-11-25 1989-05-30 Toshiba Corp Optical head
JPH03228232A (en) * 1990-01-31 1991-10-09 Sanyo Electric Co Ltd Optical pickup device
JPH07249233A (en) * 1994-03-11 1995-09-26 Pioneer Electron Corp Optical pickup
JP2002230818A (en) * 2001-02-02 2002-08-16 Sankyo Seiki Mfg Co Ltd Optical head device

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH01137435A (en) * 1987-11-25 1989-05-30 Toshiba Corp Optical head
JPH03228232A (en) * 1990-01-31 1991-10-09 Sanyo Electric Co Ltd Optical pickup device
JPH07249233A (en) * 1994-03-11 1995-09-26 Pioneer Electron Corp Optical pickup
JP2002230818A (en) * 2001-02-02 2002-08-16 Sankyo Seiki Mfg Co Ltd Optical head device

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