JPH06338076A - Optical pickup - Google Patents

Abstract

PURPOSE:To provide a small sized optical pickup to satisfactorily perform recording and reproducing information on an optical disk by converting reflected light from the optical disk into two diffraction light beams diffracted in different directions at either angle of (2n+1) and pi/4, where (n) is an integer, to the polarizing direction of linear deflection from a light emitting element, having the same diffraction angle. CONSTITUTION:Return convergent light 15 converged by an objective lens 10 after reflecting on the disk 11 is converted by a hologram 8 into 1st and 2nd return diffracted light beams 16 and 17 having the same diffraction angle and diffracting in the opposite directions having angles of 45 deg. and 225 deg. to the polarizing direction of a semiconductor laser chip 2. Since the diffracting directions of these diffracted light beams 16 and 17 are different from each other by 180 deg., irrespective of the presence of a change of the polarization state due to the Kerr effect, the polarization state as to polarization separating parts 18 and 19 respectively of both diffracted light beams 16 and 17 is the same, so that an RF signal, a focus error signal and a tracking error signal can be obtained by this sensor shape and this circuit configuration.

Description

【発明の詳細な説明】Detailed Description of the Invention

【０００１】[0001]

【産業上の利用分野】本発明は、光ディスクへの情報の
記録または再生を行う光ピックアップに関するものであ
る。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical pickup for recording or reproducing information on an optical disc.

【０００２】[0002]

【従来の技術】従来、レーザ光を利用して情報の記録や
再生を行う光ディスク装置の小型化が望まれており、光
学部品点数の削減等により光ピックアップの小型化及び
軽量化の試みが行われている。光ピックアップの小型・
軽量化は、装置全体の小型化だけでなく、アクセス時間
の短縮などの性能向上に有利となる。近年、光ピックア
ップの小型・軽量化の手段としてホログラム光学素子の
利用が挙げられており、一部実用化に供している。その
一例として特開昭６２−１４６４４４号公報等があり、
透明で細長な光案内体による複数の内部反射でレーザ光
を集光用ホログラムレンズまで導くとともに光ディスク
盤からの反射光を光案内体による複数の内部反射で光検
出器まで導くもの等がある。2. Description of the Related Art Conventionally, there has been a demand for miniaturization of an optical disc device which records and reproduces information by using a laser beam, and attempts have been made to miniaturize and reduce the weight of an optical pickup by reducing the number of optical components. It is being appreciated. Compact optical pickup
The reduction in weight is advantageous not only for downsizing the entire apparatus but also for improving performance such as shortening access time. In recent years, the use of hologram optical elements has been mentioned as a means for reducing the size and weight of optical pickups, and some of them have been put to practical use. As one example thereof, there is JP-A-62-146444,
There is a method in which a laser beam is guided to a converging hologram lens by a plurality of internal reflections by a transparent and elongated light guide body, and a reflected light from an optical disk board is guided to a photodetector by a plurality of internal reflections by the light guide body.

【０００３】[0003]

【発明が解決しようとする課題】しかし、上記従来の構
成では以下のような問題点があった。However, the above-mentioned conventional configuration has the following problems.

【０００４】（１）レーザ光を光ディスクの情報保持面
に集光するためのホログラムレンズ、往復路分離用の偏
光ビームスプリッタ、非点収差を得るためのゾーンプレ
ートが別々に構成されているため必要な光路長が長くな
り、素子の小型化が困難である。(1) Necessary because the hologram lens for condensing the laser light on the information holding surface of the optical disk, the polarization beam splitter for separating the reciprocating path, and the zone plate for obtaining the astigmatism are separately configured. Since the optical path length is long, it is difficult to miniaturize the device.

【０００５】（２）レーザの出力ビームが非球面リフレ
クタに到達するまでに、凹面リフレクタなど数回の内面
反射を繰り返しているため、レーザ光の偏光状態が直線
偏光から楕円偏光へ変化し、読み出した光磁気信号のＳ
／Ｎ比が劣化する。(2) Since the output beam of the laser repeatedly undergoes several internal reflections such as a concave reflector before it reaches the aspherical reflector, the polarization state of the laser light changes from linearly polarized light to elliptically polarized light, and reading is performed. S of the magneto-optical signal
/ N ratio deteriorates.

【０００６】（３）同様に読み出された光磁気信号を含
んだ復路の光路に数個の平面鏡があり、前項（２）と同
じように、反射によるレーザ光の偏光状態が変化し、光
磁気信号のＳ／Ｎ比が大きく劣化する。(3) Similarly, there are several plane mirrors in the return optical path containing the read magneto-optical signal, and the polarization state of the laser light due to reflection changes as in (2) above, and The S / N ratio of the magnetic signal is greatly deteriorated.

【０００７】（４）不完全偏光ビームスプリッタを形成
する場合、まず基体の上面に不完全偏光ビームスプリッ
タ用の膜をコーティングし、しかる後に外皮部分を形成
しなければならないため、形成プロセスが複雑である。(4) When forming an incompletely polarized beam splitter, the film for the incompletely polarized beam splitter must first be coated on the upper surface of the substrate, and then the outer skin portion must be formed, which complicates the forming process. is there.

【０００８】（５）凹面リフレクタ、平面鏡の面の傾き
方向がそれぞれ異なるため、各面間の位置関係、傾き角
の管理が困難である。(5) Since the tilt directions of the concave reflector and the plane mirror are different, it is difficult to control the positional relationship between the surfaces and the tilt angle.

【０００９】（６）素子構成が複雑で安価に生産できな
い。(6) The element structure is complicated and cannot be manufactured at low cost.

【００１０】[0010]

【課題を解決するための手段】本発明は以上のような従
来例の問題点を解決すべく案出されたもので、透明な平
行平板の光ガイド部材の平面のうち、光ディスク盤側を
第１面、この第１面に対し前記光ディスク盤と反対側に
位置する面を第２面とするとき、第２面側に配置された
直線偏光を発する発光素子と、発光素子からの直線偏光
をホログラムへ導く第２面に配置された入射窓と、ｎを
整数とした場合に光ディスク盤からの反射光を発光素子
からの直線偏光の偏光方向に対して、（２ｎ＋１）π／
４のいずれかの角度を有する同一方向に回折し回折角が
異なる２つの回折光または（２ｎ＋１）π／４のいずれ
かの角度を有する異なった方向に回折し回折角が等しい
２つの回折光に変換するとともに、フォーカスエラー検
出機能、トラック信号検出機能を有する第１面に配置さ
れたトラック方向の分割線を境界としてパターンの異な
る２つの等面積の領域からなるホログラムと、ホログラ
ムにより生成される２つの復路光のＰ偏光成分を各々第
１受光センサと第２受光センサへ透過し、さらに残りＳ
偏光成分を第１面に反射する偏光分離膜をコーティング
された第２面にある復路偏光分離部と、第１面にあり復
路偏光分離部からの２つの反射光を再び第２面に反射す
る復路反射部と、第２面にあり復路反射部からの２つの
反射光を各々第３受光センサと第４受光センサに導く透
過窓から構成されていて、第１受光センサと第２受光セ
ンサの和と第３受光センサと第４受光センサの和との差
で光磁気信号を、４つの前記受光センサの内いずれか２
つの受光センサでフォーカスエラー信号を、第１受光セ
ンサと第３受光センサの和と第２受光センサと第４受光
センサの和の差でトラック信号を検出する。The present invention has been devised to solve the above-mentioned problems of the conventional example. Among the planes of the transparent parallel flat plate optical guide member, the optical disc side is the first. When the first surface is the surface opposite to the optical disk board relative to the first surface, and the second surface is the second surface, the light emitting element that emits linearly polarized light and the linearly polarized light from the light emitting element are arranged on the second surface side. An incident window arranged on the second surface for guiding the hologram, and (2n + 1) π / with respect to the polarization direction of the linearly polarized light from the light emitting element when the reflected light from the optical disc board is set to n, where n is an integer.
To two diffracted lights having different angles of diffraction of 4 and different angles of diffraction, or to two diffracted lights of different angles of (2n + 1) π / 4 and having the same diffraction angle. A hologram formed of two equal-area regions having different patterns with a dividing line in the track direction arranged on the first surface having a focus error detection function and a track signal detection function as a boundary, and 2 generated by the hologram. The P-polarized light components of the two returning light beams are transmitted to the first light receiving sensor and the second light receiving sensor, respectively, and the remaining S
A return-path polarization splitting part on the second surface coated with a polarization splitting film that reflects the polarization component on the first surface, and two reflected lights from the return-path polarization splitting part on the first surface are reflected again on the second surface. It comprises a return light reflection part and a transmission window for guiding the two reflected lights from the return light reflection part on the second surface to the third light reception sensor and the fourth light reception sensor, respectively. The sum of the sum and the sum of the third light receiving sensor and the fourth light receiving sensor is used to determine the magneto-optical signal as one of the two of the four light receiving sensors.
The focus error signal is detected by one light receiving sensor, and the track signal is detected by the difference between the sum of the first light receiving sensor and the third light receiving sensor and the sum of the second light receiving sensor and the fourth light receiving sensor.

【００１１】[0011]

【作用】本発明は上記構成により、同一領域で往復路分
離機能、フォーカスエラー検出機能、トラック情報検出
機能の３つの機能を持たせることができるとともに、ホ
ログラムにより光ディスク盤からの反射光は、直線偏光
の偏光方向に対して、ｎを整数とした場合に、（２ｎ＋
１）π／４に回折する２つの回折光になり、読み出され
た光磁気信号が第１受光センサ、第２受光センサ、第３
受光センサ、第４受光センサにそれぞれ約２５％の割合
で分光される。さらに第１受光センサと第２受光センサ
の和信号と、第３受光センサと第４受光センサの和信号
の両和信号の差動増幅により、光磁気信号以外の同位相
ノイズ成分が除去された良質なＲＦ信号を得ることがで
き、さらに発光素子からの光の波長が変動しても、４つ
の前記受光センサの内いずれか２つの受光センサにより
スポットサイズ法等の手段でフォーカスエラー信号を
得、かつ第１受光センサと第３受光センサの和信号と第
２受光センサと第４受光センサの和信号の両和信号の差
動によりプッシュプル法でトラック情報信号を安定的に
得ることができる。With the above-described structure, the present invention can have three functions of a round-trip path separating function, a focus error detecting function, and a track information detecting function in the same area, and the hologram reflects the reflected light from the optical disc board. When n is an integer with respect to the polarization direction of the polarized light, (2n +
1) Two diffracted lights that are diffracted into π / 4, and the read magneto-optical signal is the first light receiving sensor, the second light receiving sensor, and the third light receiving sensor.
The light is received by the light receiving sensor and the fourth light receiving sensor is split at a rate of about 25%. Further, in-phase noise components other than the magneto-optical signal are removed by differential amplification of both sum signals of the first light receiving sensor and the second light receiving sensor and the sum signal of the third light receiving sensor and the fourth light receiving sensor. A high quality RF signal can be obtained, and even if the wavelength of the light from the light emitting element changes, a focus error signal can be obtained by means of a spot size method or the like by using any two of the four light receiving sensors. Also, the track information signal can be stably obtained by the push-pull method by the difference between the sum signals of the first light receiving sensor and the third light receiving sensor and the sum signal of the second light receiving sensor and the fourth light receiving sensor. .

【００１２】[0012]

【実施例】以下本発明の第１実施例について、図面を参
照しながら説明する。図１（ａ）は本発明の第１実施例
における光ピックアップの平面図、図１（ｂ）は図１
（ａ）におけるＸ−Ｘ断面図である。DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to the drawings. FIG. 1A is a plan view of an optical pickup according to the first embodiment of the present invention, and FIG.
It is an XX sectional view in (a).

【００１３】まず、発光素子である半導体レーザから、
光ディスク盤に至る往路の光路について説明する。図１
（ｂ）においてセンサ基盤１上に水平にマウントされた
半導体レーザチップ２から水平に放出されたレーザ光３
は、同じくセンサ基盤１上に反射面を半導体レーザチッ
プ２に対向するようにマウントされた台形状の反射プリ
ズム４により、透明な光ガイド部材５の第２面５ｂの入
射窓６から光ガイド部材５内部に入射し拡散光７にな
る。光ガイド部材５の第１面５ａにはホログラム８が形
成されていて、拡散光７はホログラム８から光ガイド部
材５の外部に出射し拡散光９になる。拡散光９は対物レ
ンズ１０に入射し、光ディスク盤１１の情報記録層１１
ａにスポット１２として集光する往路集束光１３に変換
される。First, from the semiconductor laser which is a light emitting element,
The forward optical path to the optical disc will be described. Figure 1
Laser light 3 emitted horizontally from a semiconductor laser chip 2 mounted horizontally on the sensor substrate 1 in FIG.
Is a trapezoidal reflection prism 4 which is also mounted on the sensor substrate 1 so that its reflection surface faces the semiconductor laser chip 2, and the light guide member is guided through the incident window 6 of the second surface 5b of the transparent light guide member 5. The light enters the inside of 5 and becomes diffused light 7. A hologram 8 is formed on the first surface 5 a of the light guide member 5, and the diffused light 7 is emitted from the hologram 8 to the outside of the light guide member 5 and becomes a diffused light 9. The diffused light 9 enters the objective lens 10, and the information recording layer 11 of the optical disc board 11
It is converted into the outward-focused light 13 that is condensed as a spot 12 on a.

【００１４】次に光ディスク盤１１から受光センサに至
る復路について説明する。光ディスク盤１１の情報記録
層１１ａで反射された反射光１４は対物レンズ１０に再
び入射し復路集束光１５に変換された後、ホログラム８
に入射する。Next, the return path from the optical disk board 11 to the light receiving sensor will be described. The reflected light 14 reflected by the information recording layer 11a of the optical disk board 11 is incident on the objective lens 10 again and converted into the backward-focused light 15, and then the hologram 8
Incident on.

【００１５】ホログラム８は図２のような、光ディスク
盤１１のトラック方向と同一方向の分割線Ｌを境界とし
て、各々異なるパターンを持つ２つの等面積の領域を有
し、復路集束光１５を、各々回折角が異なり且つ半導体
レーザチップ２の偏光方向に対して４５°の角度を有す
る同一方向に回折する第１復路回折光１６と第２復路回
折光１７に変換する。The hologram 8 has two equal-area regions each having a different pattern with a dividing line L in the same direction as the track direction of the optical disc 11 as a boundary, as shown in FIG. The first backward diffracted light 16 and the second backward diffracted light 17 are diffracted in the same direction having different diffraction angles and having an angle of 45 ° with respect to the polarization direction of the semiconductor laser chip 2.

【００１６】光ガイド部材５の第２面５ｂには、両復路
回折光１６，１７のＰ偏光成分を透過し、Ｓ偏光成分を
反射する復路偏光分離膜がコーティングされた第１復路
偏光分離部１８及び第２復路偏光分離部１９が形成して
ある。On the second surface 5b of the light guide member 5, there is provided a first backward polarization splitting portion coated with a backward polarization splitting film which transmits the P polarization components of both backward diffracted lights 16 and 17 and reflects the S polarization components. 18 and a second backward polarization splitting section 19 are formed.

【００１７】両偏光分離部１８，１９の偏光分離効率を
上げるため、光ガイド部材５第２面５ｂに、光ガイド部
材５の屈折率と同程度の屈折率を持つ偏光分離補助部材
２０が接合され、両偏光分離部１８，１９は同程度の屈
折率を持つ光ガイド部材５と偏光分離補助部材２０で完
全に覆われている。In order to improve the polarization separation efficiency of both the polarization separation sections 18 and 19, a polarization separation auxiliary member 20 having a refractive index similar to that of the light guide member 5 is joined to the second surface 5b of the light guide member 5. The polarization splitting portions 18 and 19 are completely covered with the light guide member 5 and the polarization splitting auxiliary member 20 having the same refractive index.

【００１８】また偏光分離補助部材２０を用いる代わり
に、光ガイド部材５と、樹脂、セラミックス等の非導電
性材質で作られたパッケージ２１で囲まれた空間２２を
光ガイド部材５の屈折率と同程度の屈折率を持つ透明樹
脂等で充填しても良い。Instead of using the polarization separation auxiliary member 20, a space 22 surrounded by the light guide member 5 and a package 21 made of a non-conductive material such as resin or ceramics is used as the refractive index of the light guide member 5. It may be filled with a transparent resin or the like having a similar refractive index.

【００１９】前述のように、図１（ａ）においてホログ
ラム８に入射する拡散光７の偏光状態を矢印で表すよう
な直線偏光２３とすると、両復路回折光１６，１７の回
折方向が、直線偏光２３の偏光方向に対して４５°に設
定してあるので、両復路偏光分離部１８，１９に入射す
る両復路回折光１６，１７は両復路偏光分離部１８，１
９に対してＰ偏光成分、Ｓ偏光成分が各々約半分とな
り、また両復路偏光分離部１８，１９が同程度の屈折率
を持つ光ガイド部材５と偏光分離補助部材２０で覆われ
ているため、両復路偏光分離部１８，１９からの第１透
過光２４及び第２透過光２５の光量は、各々第１復路回
折光１６及び第２復路回折光１７の約半分になる。両透
過光２４，２５は、各々センサ基盤１に形成された第１
受光センサ２６及び第２受光センサ２７を照射する。両
復路偏光分離部１８，１９で反射された両復路回折光１
６，１７の残りの約半分である第１反射光２８、第２反
射光２９は、各々第１面５ａの第１復路反射部３０及び
第２復路反射部３１で反射され、再び第２面５ｂへ向か
う第３反射光３２及び第４反射光３３となる。この第３
反射光３２及び第４反射光３３は、各々第２面５ｂの第
１透過窓３４及び第２透過窓３５を透過した後、各々第
３透過光３６及び第４透過光３７となり、両透過光３
６，３７は各々第３受光センサ３８及び第４受光センサ
３９を照射する。尚、第１，第２復路回折光１６，１７
は、各々両復路偏光分離部１８，１９と、第３，第４受
光センサ３８，３９間に焦点が存在するように設定され
ている。As described above, assuming that the polarization state of the diffused light 7 incident on the hologram 8 in FIG. 1 (a) is a linearly polarized light 23 represented by an arrow, the diffracting directions of the two returning diffracted lights 16 and 17 are linear. Since it is set to 45 ° with respect to the polarization direction of the polarized light 23, the double-path return diffracted lights 16 and 17 incident on the double-path return polarization splitting units 18 and 19 are converted into the double-path return polarization splitting units 18 and 1.
Since the P-polarized component and the S-polarized component are each about half that of 9, and both the return polarization splitting portions 18 and 19 are covered with the light guide member 5 and the polarization splitting auxiliary member 20 having the same refractive index. The light amounts of the first transmitted light 24 and the second transmitted light 25 from the two backward polarization splitting units 18 and 19 are about half of those of the first backward diffracted light 16 and the second backward diffracted light 17, respectively. The two transmitted lights 24 and 25 are the first lights formed on the sensor substrate 1 respectively.
The light receiving sensor 26 and the second light receiving sensor 27 are irradiated. Double return diffracted light 1 reflected by the double return polarization splitting units 18 and 19
The first reflected light 28 and the second reflected light 29, which are about half of the remaining 6 and 17, are reflected by the first return reflection portion 30 and the second return reflection portion 31 of the first surface 5a, respectively, and again the second surface. It becomes the third reflected light 32 and the fourth reflected light 33 that travel toward 5b. This third
The reflected light 32 and the fourth reflected light 33 pass through the first transmission window 34 and the second transmission window 35 of the second surface 5b, respectively, and then become the third transmission light 36 and the fourth transmission light 37, respectively. Three
Reference numerals 6 and 37 illuminate the third light receiving sensor 38 and the fourth light receiving sensor 39, respectively. The first and second backward diffracted lights 16 and 17
Are set so that there is a focal point between both the return polarization splitting units 18 and 19 and the third and fourth light receiving sensors 38 and 39.

【００２０】また両復路偏光分離部１８，１９を１つの
偏光分離部で形成したり、両復路反射部３０，３１を１
つの反射部で形成したりしても良い。Further, both the return-path polarized light separating portions 18 and 19 are formed by one polarized light-separating portion, and the both return-path reflecting portions 30 and 31 are formed into one.
It may be formed of two reflecting portions.

【００２１】図４を用いて更に詳細に光磁気信号検出原
理を説明する。図３において、横軸はＰ偏光成分、縦軸
はＳ偏光成分を示し、２３は前述のように、ホログラム
８に入射する直線偏光２３の偏光方向を示す。ホログラ
ム８は、偏光面には影響を与えないから、光ディスク盤
１１の情報記録層１１ａに情報が記録されていなければ
（情報記録層１１ａが磁化されていなければ）、スポッ
ト１２の反射光である両復路回折光１６，１７も直線偏
光２３と同じ偏光方向を有する。このような状態の両復
路回折光１６，１７の偏光方向を両復路偏光分離部１
８，１９（Ｐ偏光成分をほぼ１００％透過させ、Ｓ偏光
成分をほぼ１００％反射する）に対し、方位４５°（図
３）で入射するように、両復路回折光１５，１６の回折
方向を直線偏光２３の偏光方向に対して４５°に設定す
る。The principle of magneto-optical signal detection will be described in more detail with reference to FIG. In FIG. 3, the horizontal axis represents the P polarization component, the vertical axis represents the S polarization component, and 23 represents the polarization direction of the linearly polarized light 23 incident on the hologram 8, as described above. Since the hologram 8 does not affect the polarization plane, it is the reflected light of the spot 12 unless information is recorded on the information recording layer 11a of the optical disc board 11 (when the information recording layer 11a is not magnetized). Both return-path diffracted lights 16 and 17 also have the same polarization direction as the linearly polarized light 23. The polarization directions of the double return diffracted lights 16 and 17 in such a state are changed to the double return polarization splitting unit 1.
8 and 19 (almost 100% of the P-polarized component is transmitted and almost 100% of the S-polarized component is reflected) so that they are incident at an azimuth angle of 45 ° (FIG. 3), the diffracted directions of both backward-path diffracted lights 15 and 16 Is set to 45 ° with respect to the polarization direction of the linearly polarized light 23.

【００２２】直線偏光２３は、光ディスク盤１１の磁化
された情報ピットで反射すると、磁化の極性と磁化の強
さによって回転方向は±θｋの範囲で変化する（カー効
果）。いま直線偏光２３の状態からθｋ回転した状態を
直線偏光４０、−θｋ回転した状態を直線偏光４１とす
る。そして、直線偏光４０から直線偏光４１まで変調さ
れた光磁気信号を両復路偏光分離部１８，１９の偏光分
離膜に入射させると、第１受光センサ２６と第２受光セ
ンサ２７で検出するＰ偏光成分は信号４２のようにな
り、第３受光センサ３８と第４受光センサ３９で検出す
るＳ偏光成分は信号４３のようになる。When the linearly polarized light 23 is reflected by the magnetized information pits of the optical disc board 11, the rotation direction changes within the range of ± θk depending on the polarity of the magnetization and the strength of the magnetization (Kerr effect). Now, the state of θk rotation from the state of linearly polarized light 23 is referred to as linearly polarized light 40, and the state of −θk rotation is referred to as linearly polarized light 41. Then, when the magneto-optical signals modulated from the linearly polarized light 40 to the linearly polarized light 41 are made incident on the polarization separation films of both the backward polarization separation units 18 and 19, the P polarized light detected by the first light receiving sensor 26 and the second light receiving sensor 27. The component becomes like a signal 42, and the S-polarized component detected by the third light receiving sensor 38 and the fourth light receiving sensor 39 becomes like a signal 43.

【００２３】ここで、信号４２と信号４３は位相が１８
０°ずれているから、第１復路回折光１６のＰ偏光成分
と第２復路回折光１７のＰ偏光線分の和信号と、第１復
路回折光１６のＳ偏光成分と第２復路回折光１７のＳ偏
光成分の和信号との差動により、信号成分は２倍とな
り、同位相成分のノイズはキャンセルされるから、結果
的にＳ／Ｎ比が良くなる。The signal 42 and the signal 43 have a phase of 18
Since they are shifted by 0 °, the sum signal of the P-polarized component of the first backward diffracted light 16 and the P-polarized line segment of the second backward diffracted light 17, the S-polarized component of the first backward diffracted light 16, and the second backward diffracted light The signal component is doubled by the differential with the sum signal of the S-polarized component of 17, and the noise of the in-phase component is canceled, resulting in a good S / N ratio.

【００２４】なお、半導体レーザチップ２および前記の
受光センサ群２６，２７，３８，３９等が形成されてい
るセンサ基盤１への各種信号の入出力は、リードフレー
ム４４を介して行われる。また、偏光分離補助部材２０
とパッケージ２１で囲まれた空間２２は、通常窒素ガス
等の不活性ガスで充満される。Input and output of various signals to and from the sensor substrate 1 on which the semiconductor laser chip 2 and the light receiving sensor groups 26, 27, 38, 39 and the like are formed are performed via the lead frame 44. In addition, the polarization separation auxiliary member 20
The space 22 surrounded by the package 21 is normally filled with an inert gas such as nitrogen gas.

【００２５】また、本実施例では両復路回折光１６，１
７の回折方向を直線偏光２３の偏光方向に対して４５°
に設定したが、この回折方向の角度をｎを整数とした場
合に（２ｎ＋１）π／４のいずれかの方向に変更しても
差支えない。Further, in this embodiment, both backward diffracted lights 16, 1
The diffraction direction of 7 is 45 ° with respect to the polarization direction of the linearly polarized light 23.
However, when n is an integer, the angle of the diffraction direction may be changed to any of (2n + 1) π / 4.

【００２６】さらに、ホログラム８が矩形状の格子断面
を持つ場合、＋１次回折光と−１次回折光が等量発生
し、そのうち一方の回折光のみが両復路回折光１６，１
７として受光センサ群２６，２７，３８，３９を照射す
るため、受光センサ群２６，２７，３８，３９に到達す
る光量の損失が生じ、Ｓ／Ｎ比が悪化する。そこで、こ
のＳ／Ｎ比の悪化を防ぐべく、他方の回折光を受光する
受光センサ群を半導体レーザチップ２に対して受光セン
サ群２６，２７，３８，３９と反対側に設置すると良
い。Further, when the hologram 8 has a rectangular lattice cross section, the + 1st-order diffracted light and the -1st-order diffracted light are generated in equal amounts, and only one of the diffracted lights is a double return diffracted light 16, 1.
Since the light receiving sensor groups 26, 27, 38, 39 are irradiated as No. 7, a loss of the amount of light reaching the light receiving sensor groups 26, 27, 38, 39 occurs, and the S / N ratio deteriorates. Therefore, in order to prevent the deterioration of the S / N ratio, the light receiving sensor group that receives the other diffracted light may be installed on the opposite side of the semiconductor laser chip 2 from the light receiving sensor groups 26, 27, 38, 39.

【００２７】次に、図４を用いて第１受光センサ２６，
第２受光センサ２７、第３受光センサ３８および第４受
光センサ３９の形状と、信号検出原理について説明す
る。Next, referring to FIG. 4, the first light receiving sensor 26,
The shapes of the second light receiving sensor 27, the third light receiving sensor 38, and the fourth light receiving sensor 39 and the signal detection principle will be described.

【００２８】第２受光センサ２７および第４受光センサ
３９は３分割センサで、それぞれ部分２７ａ，部分２７
ｂ，部分２７ｃおよび部分３９ａ，部分３９ｂ，部分３
９ｃに分割されている。ここで、第１受光センサ２６お
よび第３受光センサ３８からの出力を、各々Ｉ（２６）
およびＩ（３８）で表し、また第２受光センサ２７の各
部分２７ａ，２７ｂ，２７ｃおよび第４受光センサ３９
の各部分３９ａ，３９ｂ，３９ｃからの出力を、それぞ
れＩ（２７ａ），Ｉ（２７ｂ），Ｉ（２７ｃ）およびＩ
（３９ａ），Ｉ（３９ｂ），Ｉ（３９ｃ）で表す。The second light-receiving sensor 27 and the fourth light-receiving sensor 39 are three-divided sensors, which are a portion 27a and a portion 27, respectively.
b, part 27c and part 39a, part 39b, part 3
It is divided into 9c. Here, the outputs from the first light receiving sensor 26 and the third light receiving sensor 38 are respectively I (26)
And I (38), and each portion 27a, 27b, 27c of the second light receiving sensor 27 and the fourth light receiving sensor 39.
The outputs from the respective parts 39a, 39b, 39c of I, 27 (a), I (27b), I (27c) and I (27c)
(39a), I (39b), and I (39c).

【００２９】まず、各種信号の内ＲＦ信号（Ｒ．Ｆ．）
について説明する。前述のようにこのＲＦ信号は、両復
路回折光１６，１７の各々Ｐ偏光成分の和信号とＳ偏光
成分の和信号の差動により得られるから、図４の回路図
の回路構成からわかるように以下の（数１）により得ら
れる。First, an RF signal (RF) of various signals
Will be described. As described above, this RF signal is obtained by the difference between the sum signal of the P-polarized components and the sum signal of the S-polarized components of both the backward diffracted lights 16 and 17, so that it can be understood from the circuit configuration of the circuit diagram of FIG. Is obtained by the following (Equation 1).

【００３０】[0030]

【数１】 [Equation 1]

【００３１】次にフォーカスエラー信号Ｆ．Ｅ．につい
て説明する。フォーカスエラー信号Ｆ．Ｅ．は図４の回
路図の回路構成からわかるように以下の（数２）により
得られる。Next, the focus error signal F. E. Will be described. Focus error signal F. E. Can be obtained by the following (Equation 2), as can be seen from the circuit configuration of the circuit diagram of FIG.

【００３２】[0032]

【数２】 [Equation 2]

【００３３】いま光ディスク盤１１の情報記録層１１ａ
に、対物レンズ１０のスポット１２が正確に合焦してお
り、この合焦状態における第２受光センサ２７および第
４受光センサ３９上のレーザ光の照射形状をそれぞれ４
５ａ，４６ａとすると、フォーカスエラー信号Ｆ．Ｅ．
が次の（数３）を満すようにレーザ光の照射強度分布
と、受光センサの位置関係が調整されている。Now the information recording layer 11a of the optical disc board 11
In addition, the spot 12 of the objective lens 10 is accurately focused, and the irradiation shape of the laser light on the second light receiving sensor 27 and the fourth light receiving sensor 39 in this focused state is 4 respectively.
5a and 46a, the focus error signal F. E.
The irradiation light intensity distribution of the laser beam and the positional relationship of the light receiving sensor are adjusted so that the following (Equation 3) is satisfied.

【００３４】[0034]

【数３】 [Equation 3]

【００３５】次に、光ディスク盤１１と対物レンズ１０
との間の距離が合焦状態から近接した場合、第２受光セ
ンサ２７および第４受光センサ３９上のレーザ光の照射
形状はそれぞれ形状４５ｃ，形状４６ｃとなり、フォー
カスエラー信号Ｆ．Ｅ．は（数４）の様に変化する。Next, the optical disk board 11 and the objective lens 10
When the distance between the focus error signal F. and the distance from the focus state is close to the focus state, the second light receiving sensor 27 and the fourth light receiving sensor 39 are irradiated with the laser light having shapes 45c and 46c, respectively. E. Changes like (Equation 4).

【００３６】[0036]

【数４】 [Equation 4]

【００３７】逆に、光ディスク盤１１と対物レンズ１０
との間の距離が合焦状態から離れた場合、第２受光セン
サ２７および第４受光センサ３９上のレーザ光の照射形
状は形状４５ｂ，形状４６ｂとなり、フォーカスエラー
信号Ｆ．Ｅ．は（数５）の様に変化する。On the contrary, the optical disk 11 and the objective lens 10
When the distance between the focus error signal F. and the distance from the focus state is away from the focused state, the laser light irradiation shapes on the second light receiving sensor 27 and the fourth light receiving sensor 39 are the shapes 45b and 46b. E. Changes like (Equation 5).

【００３８】[0038]

【数５】 [Equation 5]

【００３９】以上のようなフォーカスエラー検出方式は
スポットサイズ法として知られている。The focus error detection method described above is known as the spot size method.

【００４０】このように第２復路回折光１７の焦点が第
２復路偏光分離部１９と第４受光センサ３９との間に存
在するように設定することで、従来よく用いられている
非点収差法でフォーカスエラーを検出する場合におけ
る、非点収差発生用の複雑なホログラムパターンが不必
要であり、ホログラム８が回折のみの非常にシンプルな
パターンとなる。As described above, by setting the focal point of the second backward-path diffracted light 17 to be between the second backward-polarization splitting section 19 and the fourth light-receiving sensor 39, astigmatism which is often used conventionally. When a focus error is detected by the method, a complicated hologram pattern for generating astigmatism is unnecessary, and the hologram 8 is a very simple pattern of diffraction only.

【００４１】次にトラッキングエラー信号Ｔ．Ｅ．につ
いて説明する。上述したように、ホログラム８のパター
ンの異なる２つの等面積の領域の境界Ｌがトラック方向
と同一方向であるため、光ディスク盤１１からの反射光
が含んでいるトラック情報は、ホログラム８によりスポ
ット１２のトラック方向の中心線で分割される左右のト
ラック情報の２つに分けられ、その２つのトラック情報
は第１復路回折光１６と第２復路回折光１７とに分離さ
れる。さらに、第１復路回折光１６と第２復路回折光１
７についてのホログラム８の各々の領域の第１復路回折
光１６と第２復路回折光１７についての回折効率が同等
になるようにホログラム８は形成されている。従ってト
ラッキングエラー（Ｔ．Ｅ．）は図４の回路図の回路構
成よりわかるように以下の（数６）により得られる。Next, the tracking error signal T. E. Will be described. As described above, since the boundary L between the two areas of the same area having different patterns of the hologram 8 is in the same direction as the track direction, the track information contained in the reflected light from the optical disc board 11 is spotted by the hologram 8 as a spot 12. Is divided into two pieces of left and right track information divided by the center line in the track direction of, and the two pieces of track information are separated into a first backward diffracted light 16 and a second backward diffracted light 17. Further, the first backward diffracted light 16 and the second backward diffracted light 1
The hologram 8 is formed so that the diffraction efficiency of the first backward diffracted light 16 and the second backward diffracted light 17 of each region of the hologram 8 of No. 7 becomes equal. Therefore, the tracking error (TE) is obtained by the following (Equation 6), as can be seen from the circuit configuration of the circuit diagram of FIG.

【００４２】[0042]

【数６】 [Equation 6]

【００４３】スポット１２がトラック中心を照射してい
る場合、ホログラム８の２つの領域に入射する復路集束
光１５の光量は等しいため、第１復路回折光１６と第２
復路回折光１７の光量は等しく、両復路回折光１６，１
７の各々の光量である第１受光センサ２６の信号と第３
受光センサ３８の信号の和信号及び第２受光センサ２７
の信号と第４受光センサ３９の和信号とが等しくなるた
め、トラッキングエラー信号Ｔ．Ｅ．は以下の（数７）
のようになる。When the spot 12 irradiates the center of the track, the amounts of the backward-focused light 15 incident on the two regions of the hologram 8 are equal, so that the first backward-diffracted light 16 and the second backward-focused light 16 are incident.
The amounts of the backward diffracted light 17 are equal, and both backward diffracted lights 16 and 1
The signal of the first light receiving sensor 26 and the third
Sum signal of signals from the light receiving sensor 38 and the second light receiving sensor 27
Signal becomes equal to the sum signal of the fourth light receiving sensor 39, the tracking error signal T. E. Is the following (Equation 7)
become that way.

【００４４】[0044]

【数７】 [Equation 7]

【００４５】また、光ディスク盤１１のスポット１２が
トラック中心からトラックに対して９０°方向に偏心し
た場合は、ホログラム８に入射する復路集束光１５の光
量がホログラム８の２つの領域で異なるため、第１復路
回折光１６の光量である第１受光センサ２６の信号と第
３受光センサ３８の信号の和信号と、第２復路回折光１
７の光量である第２受光センサ２７の信号と第４受光セ
ンサ３９の信号の和信号は等しくなくなり、トラッキン
グエラー信号Ｔ．Ｅ．は以下の（数８）あるいは（数
９）のようになる。When the spot 12 of the optical disk 11 is decentered from the track center in the direction of 90 ° with respect to the track, the amount of the backward-focused light 15 entering the hologram 8 is different between the two regions of the hologram 8. The sum signal of the signal of the first light receiving sensor 26 and the signal of the third light receiving sensor 38, which is the light amount of the first backward diffracted light 16, and the second backward diffracted light 1
7, the sum signal of the signals of the second light receiving sensor 27 and the signal of the fourth light receiving sensor 39, which are the light amount of No. 7, is not equal to each other, and the tracking error signal T. E. Is as shown in (Equation 8) or (Equation 9) below.

【００４６】[0046]

【数８】 [Equation 8]

【００４７】[0047]

【数９】 [Equation 9]

【００４８】このトラッキングエラー検出方法はプッシ
ュプル法として知られている。このように、ホログラム
８をトラック方向と同一方向の分割線Ｌを境界として、
パターンの異なる２つの等面積の領域に分け、ホログラ
ム８の２つの領域の各々両復路回折光１６，１７に対す
る回折効率が同等になるように設定することでトラッキ
ングエラー信号Ｔ．Ｅ．を得ることができる。This tracking error detecting method is known as a push-pull method. Thus, with the hologram 8 as a boundary with the dividing line L in the same direction as the track direction,
By dividing the two areas of the hologram 8 having different equal areas and setting the diffraction efficiencies of the two areas of the hologram 8 for both the backward diffracted lights 16 and 17 to be equal, the tracking error signal T. E. Can be obtained.

【００４９】次に、半導体レーザチップ２からの光の波
長が変動した場合のフォーカスエラー信号及びトラッキ
ングエラー信号について図５を参照しながら説明する。Next, the focus error signal and the tracking error signal when the wavelength of the light from the semiconductor laser chip 2 changes will be described with reference to FIG.

【００５０】両復路回折光１６，１７の回折角θdif は
以下の（数１０）で表される。The diffraction angle θdif of the two backward diffracted lights 16 and 17 is expressed by the following (Equation 10).

【００５１】[0051]

【数１０】 [Equation 10]

【００５２】但し、θinc は入射角、λは波長、Λはホ
ログラムの格子間隔である。（数１０）からわかるよう
に両復路回折光１６，１７の回折角は格子間隔が波長に
より変動し、受光センサ群２６，２７，３８，３９上の
レーザ光の照射位置は波長変動により回折方向にずれ
る。Where θ inc is the incident angle, λ is the wavelength, and Λ is the hologram lattice spacing. As can be seen from (Equation 10), the diffraction angle of both the backward diffracted lights 16 and 17 varies with the grating spacing depending on the wavelength, and the irradiation position of the laser light on the light receiving sensor groups 26, 27, 38 and 39 is diffracted by the wavelength variation. It shifts.

【００５３】いま半導体レーザチップ２からのレーザ光
３の波長が設定値のときの第１受光センサ２６、第２受
光センサ２７、第３受光センサ３８および第４受光セン
サ３９上のレーザ光の照射形状及び位置を、図５に示す
ように、それぞれ形状４７ａ，形状４８ａ，形状４９
ａ，形状５０ａとすると、レーザ光３の波長が設定値よ
り大きいときには（数１０）からわかるように、回折角
は大きくなり第１受光センサ２６、第２受光センサ２
７、第３受光センサ３８および第４受光センサ３９上の
レーザ光の照射形状及び位置は、それぞれ形状４７ｂ，
形状４８ｂ，形状４９ｂ，形状５０ｂとなる。またレー
ザ光３の波長が設定値より小さいときには、（数１０）
からわかるように、回折角は小さくなり第１受光センサ
２６、第２受光センサ２７、第３受光センサ３８および
第４受光センサ３９上のレーザ光の照射形状及び位置
は、それぞれ形状４７ｃ，形状４８ｃ，形状４９ｃ，形
状５０ｃとなる。Irradiation of laser light on the first light receiving sensor 26, the second light receiving sensor 27, the third light receiving sensor 38, and the fourth light receiving sensor 39 when the wavelength of the laser light 3 from the semiconductor laser chip 2 is the set value. As shown in FIG. 5, the shape and the position are the shape 47a, the shape 48a, and the shape 49, respectively.
a and the shape 50a, when the wavelength of the laser light 3 is larger than the set value, the diffraction angle becomes large, as can be seen from (Equation 10), and the first light receiving sensor 26 and the second light receiving sensor 2
7, the irradiation shape and the position of the laser light on the third light receiving sensor 38 and the fourth light receiving sensor 39 are the shapes 47b,
Shape 48b, shape 49b, and shape 50b are obtained. When the wavelength of the laser beam 3 is smaller than the set value, (Equation 10)
As can be seen from the above, the diffraction angle becomes small, and the irradiation shapes and positions of the laser light on the first light receiving sensor 26, the second light receiving sensor 27, the third light receiving sensor 38, and the fourth light receiving sensor 39 are the shape 47c and the shape 48c, respectively. , Shape 49c and shape 50c.

【００５４】フォーカスエラー信号は、前述のように第
２受光センサ２７と第４受光センサ３９上のレーザ光の
照射形状で検出するが、図５からわかるようにレーザ光
３の波長が変動して両受光センサ２７，３９の照射位置
が変動しても、両受光センサ２７，３９上のレーザ光の
照射形状は変化せず、（数２）によりフォーカスエラー
信号Ｆ．Ｅ．を検出することができる。The focus error signal is detected by the irradiation shape of the laser light on the second light receiving sensor 27 and the fourth light receiving sensor 39 as described above. However, as can be seen from FIG. 5, the wavelength of the laser light 3 changes. Even if the irradiation positions of both light receiving sensors 27 and 39 change, the irradiation shape of the laser light on both light receiving sensors 27 and 39 does not change, and the focus error signal F. E. Can be detected.

【００５５】またトラッキングエラー信号Ｔ．Ｅ．は、
前述のように第１受光センサ２６の信号と第３受光セン
サ３８の信号の和信号と第２受光センサ２７の信号と第
４受光センサ３９の信号の和信号との差動で検出する
が、図５からわかるようにレーザ光３の波長が変動して
も各受光センサの信号と変化しないため（数６）により
トラッキングエラー信号Ｔ．Ｅ．を検出することができ
る。Further, the tracking error signal T. E. Is
As described above, it is detected by the differential of the sum signal of the signals of the first light receiving sensor 26 and the third light receiving sensor 38, the signal of the second light receiving sensor 27, and the signal of the fourth light receiving sensor 39. As can be seen from FIG. 5, even if the wavelength of the laser beam 3 fluctuates, it does not change from the signal of each light receiving sensor. E. Can be detected.

【００５６】以上のように半導体レーザチップ２からの
レーザ光３の波長が変動しても、その変動に影響される
ことなく各種信号を検出することができる。As described above, even if the wavelength of the laser beam 3 from the semiconductor laser chip 2 fluctuates, various signals can be detected without being affected by the fluctuation.

【００５７】本実施例では第２受光センサ２７と第４受
光センサ３９を３分割センサにし、第２受光センサ２７
と第４受光センサ３９によりフォーカスエラーを検出し
たが、第１復路回折光１６の焦点が、第１偏光分離部１
８と第３受光センサ３８との間に存在するようにし、か
つ第１受光センサ２６と第３受光センサ３８を３分割セ
ンサにして、第１受光センサ２６と第３受光センサ３８
によりフォーカスエラーを検出しても良い。In this embodiment, the second light receiving sensor 27 and the fourth light receiving sensor 39 are three-divided sensors, and the second light receiving sensor 27
Although the focus error is detected by the fourth light receiving sensor 39, the focus of the first backward diffracted light 16 is
8 and the third light receiving sensor 38, and the first light receiving sensor 26 and the third light receiving sensor 38 are divided into three sensors, and the first light receiving sensor 26 and the third light receiving sensor 38
The focus error may be detected by.

【００５８】以下本発明の第２実施例について、図面を
参照しながら説明する。図６（ａ）は本発明の第２実施
例における光ピックアップの平面図、図６（ｂ）は図６
（ａ）におけるＸ−Ｘ断面図である。The second embodiment of the present invention will be described below with reference to the drawings. FIG. 6A is a plan view of an optical pickup according to the second embodiment of the present invention, and FIG.
It is an XX sectional view in (a).

【００５９】本実施例では、ホログラム８は、図７に示
すように、光ディスク盤１１のトラック方向と同一方向
の中心軸を境界Ｌとして、各々異なるパターンを持つ２
つの領域を有し、第１受光センサ２６および第３受光セ
ンサ３８は、半導体レーザチップ２に対して、第２受光
センサ２７および第４受光センサ３９と反対方向に設置
されている。In this embodiment, as shown in FIG. 7, the hologram 8 has two different patterns with the central axis in the same direction as the track direction of the optical disc 11 as the boundary L.
The first light receiving sensor 26 and the third light receiving sensor 38 have two regions, and are arranged in the direction opposite to the second light receiving sensor 27 and the fourth light receiving sensor 39 with respect to the semiconductor laser chip 2.

【００６０】光ディスク盤１１で反射され対物レンズ１
０で集光される復路集束光１５は、ホログラム８によっ
て回折角が同一で且つ半導体レーザチップ２の偏光方向
に対して４５°と２２５°の角度を有する反対方向に回
折する第１復路回折光１６と第２復路回折光１７に変換
される。Objective lens 1 reflected by the optical disk board 11
The backward-focused light 15 converged at 0 is the first backward-diffracted light that has the same diffraction angle by the hologram 8 and is diffracted in the opposite directions having angles of 45 ° and 225 ° with respect to the polarization direction of the semiconductor laser chip 2. 16 and the second backward diffracted light 17.

【００６１】両復路回折光１６，１７は各々第１偏光分
離部１８と第２偏光分離部１９によりＰ偏光成分とＳ偏
光成分に分離され、両復路回折光１６，１７のＰ偏光成
分である第１透過光と第２透過光は各々第１受光センサ
２６と第３受光センサ３８を照射し、Ｓ偏光成分である
第３透過光３６と第４透過光３７は、第２受光センサ２
７と第４受光センサ３９を照射する。Both return-path diffracted lights 16 and 17 are separated into a P-polarized component and an S-polarized component by the first polarization separation section 18 and the second polarization separation section 19, respectively, and are P-polarized components of the both return-path diffracted light 16 and 17, respectively. The first transmitted light and the second transmitted light irradiate the first light receiving sensor 26 and the third light receiving sensor 38, respectively, and the third transmitted light 36 and the fourth transmitted light 37, which are S-polarized components, are emitted from the second light receiving sensor 2 respectively.
7 and the fourth light receiving sensor 39 are irradiated.

【００６２】第１復路回折光１６と第２復路回折光１７
の回折方向は、１８０°異なるため、カー効果による偏
光状態の変化の有無に関わらず、第１復路回折光１６と
第２復路回折光１７の各々両偏光分離部１８，１９に対
する偏光状態は同一であり、図４に示す本発明第１実施
例のセンサ形状と回路構成でＲＦ信号、フォーカスエラ
ー信号Ｆ．Ｅ．、トラッキングエラー信号Ｔ．Ｅ．を得
ることができる。First return diffracted light 16 and second return diffracted light 17
Of the first backward diffracted light 16 and the second backward diffracted light 17 have the same polarization state with respect to both polarization splitting portions 18 and 19 regardless of whether the polarization state changes due to the Kerr effect. In the sensor shape and circuit configuration of the first embodiment of the present invention shown in FIG. E. , Tracking error signal T. E. Can be obtained.

【００６３】また、前述のようにホログラム８が矩形状
の格子断面を持つ場合、＋１次回折光と−１次回折光が
等量発生するが、そのうち一方の回折光のみが第１復路
回折光１６として第１受光センサ２６及び第３受光セン
サ３８を第２復路回折光１７として第２受光センサ２７
と第４受光センサ３９を照射するが、他方の回折光が迷
光として反対方向の受光センサを照射しＳ／Ｎ比が悪化
する可能性がある。このＳ／Ｎ比の悪化を防ぐため、ホ
ログラム８の格子断面形状を鋸歯状にすることにより、
＋１次回折光または−１次回折光のとちらか一方の回折
光の発生を抑制することができる。When the hologram 8 has a rectangular grating cross section as described above, the + 1st order diffracted light and the −1st order diffracted light are generated in equal amounts, but only one of them is the first backward diffracted light 16. The first light receiving sensor 26 and the third light receiving sensor 38 are used as the second backward diffraction light 17 and the second light receiving sensor 27.
The fourth light receiving sensor 39 is irradiated, but the other diffracted light may be irradiated as stray light to the light receiving sensor in the opposite direction, and the S / N ratio may be deteriorated. In order to prevent the deterioration of the S / N ratio, the hologram 8 has a sawtooth-shaped grating cross section,
It is possible to suppress the generation of either one of the + 1st-order diffracted light and the -1st-order diffracted light.

【００６４】また、このＳ／Ｎ比の悪化を防ぐため他方
の回折光を受光する受光センサ群を、半導体レーザチッ
プ２に対して受光センサ群２６，２７，３８，３９と反
対側に設置しても良い。In order to prevent the deterioration of the S / N ratio, the light receiving sensor group for receiving the other diffracted light is installed on the opposite side of the semiconductor laser chip 2 from the light receiving sensor groups 26, 27, 38, 39. May be.

【００６５】なお本実施例では、両復路回折光１６，１
７の回折方向を直線偏光２３の偏光方向に対して各々４
５°と２２５°に設定したが、この回折方向の角度は、
ｎを整数とした場合に、（２ｎ＋１）π／４のいずれか
の方向としても差支えない。In the present embodiment, both backward diffracted lights 16, 1
The diffraction direction of 7 is 4 with respect to the polarization direction of the linearly polarized light 23.
I set it to 5 ° and 225 °, but the angle of this diffraction direction is
When n is an integer, it does not matter whether the direction is (2n + 1) π / 4.

【００６６】また本実施例では、両復路回折光１６，１
７の回折方向を各々４５°と２２５°として１８０°異
なるように設定したが、例えば４５°と１３５°または
４５°と３１５°のように回折角を９０°または２７０
°異なるように設定しても良い。回折角を９０°または
２７０°異ならせることで、±１次回折光の内、両復路
回折光１６，１７と異なる他方の回折光が迷光として受
光センサに漏れ込むことを防ぐことができ、Ｓ／Ｎ比の
悪化を防ぐことができ、また本発明第１実施例と同様、
ホログラム８が矩形状の格子断面を持つ場合、＋１次回
折光と−１次回折光が等量発生し、そのうち一方の回折
光のみが両復路回折光１６，１７として受光センサ群２
６，２７，３８，３９を照射するため、受光センサ群２
６，２７，３８，３９に到達する光量の損失が生じるこ
とによるＳ／Ｎ比の悪化を防ぐべく、他方の回折光を受
光する受光センサ群を半導体レーザチップ２に対して受
光センサ群２６，２７，３８，３９と反対側に設置して
も良い。Further, in this embodiment, both return path diffracted lights 16 and 1
The diffraction directions of No. 7 are set to 45 ° and 225 °, respectively, and are set to be different by 180 °, but the diffraction angles are 90 ° or 270 such as 45 ° and 135 ° or 45 ° and 315 °.
° Different settings may be used. By making the diffraction angles different by 90 ° or 270 °, it is possible to prevent the other diffracted light, which is different from both the backward diffracted lights 16 and 17, of the ± first-order diffracted lights from leaking into the light receiving sensor as stray light. It is possible to prevent the deterioration of the N ratio, and like the first embodiment of the present invention,
When the hologram 8 has a rectangular grating cross section, the + 1st-order diffracted light and the −1st-order diffracted light are generated in equal amounts, and only one of the diffracted lights is the double-returned diffracted light 16 and 17 as the light receiving sensor group 2
6, 27, 38, 39 to irradiate the light receiving sensor group 2
In order to prevent the S / N ratio from deteriorating due to the loss of the amount of light reaching 6, 27, 38, 39, the other light receiving sensor group for receiving the diffracted light is provided to the semiconductor laser chip 2 with respect to the light receiving sensor group 26, You may install on the opposite side to 27,38,39.

【００６７】しかし、回折角を９０°または２７０°異
なる場合のＲＦ信号の検出は、本実施例とは異なる。図
３を用いて両復路回折光１６，１７の回折方向が９０°
あるいは２７０°異なる場合のＲＦ信号の検出について
説明する。カー効果により第１復路回折光１６の偏光状
態が直線偏光２３の状態からθｋ回転して直線偏光４０
に変調されたとする。この場合、第２復路回折光１７
は、第１復路回折光１６と回折方向が９０°あるいは２
７０°異なるため、その偏光状態は直線偏光２３の状態
から−θｋ回転した直線偏光４１に変調される。従っ
て、第２復路回折光１７のＰ偏光成分は、第１復路回折
光１６のＰ偏光成分と等しく、第２復路回折光１７のＳ
偏光成分は、第１復路回折光１６のＰ偏光成分と等しく
なる。従ってＲＦ信号は、第１復路回折光１６のＰ偏光
線分の信号と第２復路回折光１７のＳ偏光成分の信号の
和信号と第１復路回折光１６のＳ偏光線分の信号と第２
復路回折光１７のＰ偏光成分の信号の和信号との差動つ
まり以下の（数１１）により得られる。However, the detection of the RF signal when the diffraction angle differs by 90 ° or 270 ° is different from that of this embodiment. As shown in FIG. 3, the diffraction directions of the backward diffracted lights 16 and 17 are 90 °.
Alternatively, detection of an RF signal when the difference is 270 ° will be described. Due to the Kerr effect, the polarization state of the first backward diffracted light 16 is rotated by θk from the state of the linearly polarized light 23 and the linearly polarized light 40
Suppose it is modulated to. In this case, the second backward diffracted light 17
Is 90 ° or 2 in the direction of diffraction with the first backward diffracted light 16
Since the difference is 70 °, the polarization state is modulated from the state of the linearly polarized light 23 to the linearly polarized light 41 rotated by −θk. Therefore, the P-polarized component of the second backward diffracted light 17 is equal to the P-polarized component of the first backward diffracted light 16, and the S of the second backward diffracted light 17 is S.
The polarization component becomes equal to the P polarization component of the first backward diffracted light 16. Therefore, the RF signal is the sum of the signal of the P-polarized line component of the first backward diffracted light 16 and the signal of the S-polarized component of the second backward diffracted light 17, and the signal of the S-polarized line segment of the first backward diffracted light 16 and Two
It is obtained by the differential with the sum signal of the signals of the P-polarized component of the backward diffracted light 17, that is, the following (Equation 11).

【００６８】[0068]

【数１１】 [Equation 11]

【００６９】以下に本発明の別のフォーカスエラー信号
の検出について、図８を参照しながら説明する。The detection of another focus error signal according to the present invention will be described below with reference to FIG.

【００７０】前述の第２実施例において、第３受光セン
サ３８と第４受光センサ３９を３分割センサにし、さら
に、第３透過光３６の焦点５１が第３受光センサ３８に
対して上流に第４透過光３７の焦点５２が第４受光セン
サ３９に対して下流に在り、かつ第３透過光３６の第３
受光センサ３８上の照射形状と第４透過光３７の第４受
光センサ３９上の照射形状が同一になるようにホログラ
ム８を形成する。光ディスク盤１１からの復路集束光１
５の偏光状態がカー効果で変化しても、前述のように第
１復路回折光１６と第２復路回折光１７のＳ偏光成分は
同等であるから前述のスポットサイズ法でフォーカスエ
ラーを検出することができる。In the above-described second embodiment, the third light receiving sensor 38 and the fourth light receiving sensor 39 are divided into three sensors, and the focus 51 of the third transmitted light 36 is located upstream of the third light receiving sensor 38. The focal point 52 of the fourth transmitted light 37 is located downstream of the fourth light receiving sensor 39, and the third transmitted light 36 has a third focal point.
The hologram 8 is formed so that the irradiation shape on the light receiving sensor 38 and the irradiation shape on the fourth light receiving sensor 39 of the fourth transmitted light 37 are the same. Return path focused light 1 from optical disk 11
Even if the polarization state of No. 5 changes due to the Kerr effect, the S-polarized components of the first backward diffracted light 16 and the second backward diffracted light 17 are equal to each other as described above, and thus the focus error is detected by the spot size method. be able to.

【００７１】同様に第１受光センサ２６と第２受光セン
サ２７を３分割センサにし、さらに、第１透過光２４の
焦点５１が第１受光センサ２６に対して上流に第２透過
光２５の焦点５２が第２受光センサ２７に対して下流に
在り、かつ第１透過光２４の第１受光センサ２６上の照
射形状と第２透過光２５の第２受光センサ２７上の照射
形状が同一になるようにホログラム８を形成することに
より、スポットサイズ法でフォーカスエラーを検出する
ことができる。Similarly, the first light receiving sensor 26 and the second light receiving sensor 27 are three-divided sensors, and the focus 51 of the first transmitted light 24 is further upstream of the first light receiving sensor 26 and the focus of the second transmitted light 25. 52 is downstream of the second light receiving sensor 27, and the irradiation shape of the first transmitted light 24 on the first light receiving sensor 26 and the irradiation shape of the second transmitted light 25 on the second light receiving sensor 27 are the same. By forming the hologram 8 in this way, the focus error can be detected by the spot size method.

【００７２】[0072]

【発明の効果】本発明は、透明な光ガイド部材の平行平
面のうち、光ディスク盤側を第１面、第１面に対し前記
光ディスク盤と反対側に位置する面を第２面とすると
き、第２面側に配置された直線偏光を発する発光素子
と、光ディスク盤からの反射光を、直線偏光の偏光方向
に対してｎを整数とした場合に（２ｎ＋１）π／４の角
度を有する同一方向に回折し回折角が異なる２つの回折
光、または直線偏光の偏光方向に対して（２ｎ＋１）π
／４の角度を有する異なった方向に回折し回折角が等し
い回折光に変換し、且つフォーカスエラー検出機能及び
トラッキングエラー検出機能を有するトラック方向の中
心軸を境界としてパターンの異なる２つの領域からなる
ホログラムと、ホログラムにより生成される２つの復路
回折光のＰ偏光成分を各々第１受光センサと第２受光セ
ンサへ透過し、さらに残りＳ偏光成分を第１面に反射す
る偏光分離膜をコーティングされた復路偏光分離部と、
第１面にあり復路偏光分離部からの２つの反射光を再び
第２面に反射する復路反射面と、第２面にあり復路反射
部からの２つの反射光を各々第３受光センサと第４受光
センサに導く透過窓を有して構成される。したがって、
読み出された光磁気信号が第１受光センサと第２受光セ
ンサの和信号と第３受光センサと第４受光センサの和信
号の両和信号の差動増幅により、光磁気信号以外の同位
相ノイズ成分が除去された良質なＲＦ信号を得ることが
でき、さらにフォーカスエラー信号をスポットサイズ法
により、トラック情報をプッシュプル法により、発光素
子の波長変動に対して安定な信号を得ることができる。According to the present invention, among the parallel planes of the transparent light guide member, the optical disk side is the first surface and the surface opposite to the optical disk side is the second surface. , The linearly polarized light emitting element arranged on the second surface side and the reflected light from the optical disc have an angle of (2n + 1) π / 4 when n is an integer with respect to the polarization direction of the linearly polarized light. (2n + 1) π for two diffracted lights that are diffracted in the same direction but have different diffraction angles, or for the polarization direction of linearly polarized light.
It is composed of two regions having different patterns with a center axis in the track direction as a boundary, which has a focus error detection function and a tracking error detection function, and which is diffracted into different directions having an angle of / 4 and converted into diffracted light with the same diffraction angle. A hologram and a polarization separation film that transmits the P-polarized light components of the two backward diffracted light beams generated by the hologram to the first light receiving sensor and the second light receiving sensor, respectively, and further reflects the remaining S-polarized light component on the first surface are coated. And the return polarization splitting unit,
The return reflection surface, which is on the first surface and reflects the two reflected lights from the return polarization splitting portion to the second surface again, and the two reflection lights, which are on the second surface and reflected from the return reflection portion, are respectively reflected by the third light receiving sensor and the third light receiving sensor. 4 It has a transmission window leading to the light receiving sensor. Therefore,
The read magneto-optical signal has the same phase other than the magneto-optical signal due to the differential amplification of the sum signal of the first light receiving sensor and the second light receiving sensor and the sum signal of the third light receiving sensor and the fourth light receiving sensor. It is possible to obtain a high-quality RF signal from which a noise component has been removed, and a focus error signal can be obtained by the spot size method, and track information can be obtained by the push-pull method to obtain a stable signal with respect to the wavelength variation of the light emitting element. .

【００７３】加えて、製造法としても平行平板へのホロ
グラムのパターンニングや、膜形状などの簡単な構成で
あるため、高精度に高集積化が可能で、しかも安価な光
磁気記録用光ピックアップを提供することができる。In addition, as a manufacturing method, since the hologram is patterned on the parallel plate and the film configuration is simple, the optical pickup for magneto-optical recording can be highly accurately and highly integrated. Can be provided.

【図面の簡単な説明】[Brief description of drawings]

【図１】（ａ）本発明の第１実施例における光ピックア
ップの平面図 （ｂ）同縦断面図FIG. 1A is a plan view of an optical pickup according to a first embodiment of the present invention, and FIG. 1B is a longitudinal sectional view of the same.

【図２】本発明の第１実施例に係るホログラムのパター
ン説明図FIG. 2 is an explanatory diagram of a hologram pattern according to the first embodiment of the present invention.

【図３】本発明に係る光磁気信号検出原理図FIG. 3 is a principle diagram of magneto-optical signal detection according to the present invention.

【図４】本発明の実施例に係る受光センサの形状および
信号処理回路説明図FIG. 4 is an explanatory diagram of a shape of a light receiving sensor and a signal processing circuit according to an embodiment of the present invention.

【図５】本発明の実施例に係る波長変動した場合の受光
センサ上での回折光を示す図FIG. 5 is a diagram showing diffracted light on the light receiving sensor when the wavelength is changed according to the embodiment of the invention.

【図６】（ａ）本発明の第２実施例に係る光ピックアッ
プの平面図 （ｂ）同縦断面図FIG. 6A is a plan view of an optical pickup according to a second embodiment of the invention, and FIG. 6B is a longitudinal sectional view of the same.

【図７】本発明の第２実施例に係るホログラムのパター
ン説明図FIG. 7 is an explanatory diagram of a hologram pattern according to a second embodiment of the present invention.

【図８】本発明の実施例に係る別のフォーカスエラー検
出方法例を示す図FIG. 8 is a diagram showing another example of a focus error detection method according to the embodiment of the present invention.

【符号の説明】[Explanation of symbols]

１ センサ基盤 ２ 半導体レーザチップ ４ 反射プリズム ５ 光ガイド部材 ６ 入射窓 ８ ホログラム １０ 対物レンズ １１ 光ディスク盤 １２ スポット １６ 第１復路回折光 １７ 第２復路回折光 １８ 第１復路偏光分離部 １９ 第２復路偏光分離部 ２０ 偏光分離補助部材 ２１ パッケージ ２３ 直線偏光 ２６ 第１受光センサ ２７ 第２受光センサ ３０ 第１復路反射部 ３１ 第２復路反射部 ３４ 第１透過窓 ３５ 第２透過窓 ３８ 第３受光センサ ３９ 第４受光センサ ４４ リードフレーム 1 Sensor Substrate 2 Semiconductor Laser Chip 4 Reflecting Prism 5 Light Guide Member 6 Incident Window 8 Hologram 10 Objective Lens 11 Optical Disc Board 12 Spot 16 First Return Diffracted Light 17 Second Return Diffracted Light 18 First Return Polarization Separation Section 19 Second Return Polarization separation section 20 Polarization separation auxiliary member 21 Package 23 Linearly polarized light 26 First light receiving sensor 27 Second light receiving sensor 30 First return path reflection section 31 Second return path reflection section 34 First transmission window 35 Second transmission window 38 Third light reception sensor 39 Fourth light receiving sensor 44 Lead frame

Claims (6)

【特許請求の範囲】[Claims] 【請求項１】光ディスク盤へ直線偏光の光を照射する発
光素子と、前記発光素子からの光を、前記光ディスク盤
に集光する対物レンズと、前記光ディスク盤からの反射
光を受光する第１受光センサ、第２受光センサ、第３受
光センサ及び第４受光センサと、前記受光センサ群と前
記対物レンズとの間に配置され、前記発光素子からの光
を前記対物レンズへ案内するとともに、前記対物レンズ
を通過した前記光ディスク盤からの反射光を前記受光セ
ンサ群へ案内する透明な平行平板の光ガイド部材と、前
記光ガイド部材の平面のうち、前記対物レンズ側に位置
する面を第１面、この第１面に対し前記光ディスク盤と
反対側に位置する面を第２面とするとき、前記対物レン
ズを通過した前記光ディスク盤からの反射光を、ｎを整
数とした場合に、前記発光素子からの光の偏光方向に対
して（２ｎ＋１）π／４の角度を有する同一方向に回折
し且つ回折角が異なる２つの光へ変換する機能を有し、
かつ前記光ディスク盤のトラック方向と同一方向の分割
線を境界として２つの異なるパターンを持つホログラム
を、前記光ガイド部材の第１面に設け、前記発光素子か
らの光を前記ホログラムに導く入射窓を前記光ガイド部
材の第２面に設け、前記ホログラムからの２つの回折光
のＰ偏光成分を各々前記第１受光センサ及び前記第２受
光センサへ透過し、Ｓ偏光成分を反射する第１偏光分離
部及び第２偏光分離部を前記光ガイド部材の第２面に設
け、前記両偏光分離部からの２つの反射光を各々前記第
３受光センサ及び前記第４受光センサへ反射する反射部
を前記光ガイド部材の前記第１面に設け、前記反射部か
らの２つの反射光を前記第３受光センサ及び前記第４受
光センサに導く透過窓を前記光ガイド部材の前記第２面
に設け、前記対物レンズ及び前記ホログラムを通ってき
た前記両回折光の２つの焦点が、前記両偏光分離膜と各
々前記第３受光センサ、前記第４受光センサの間に存在
するように設定し、前記第１受光センサと前記第２受光
センサとの出力和と前記第３受光センサと前記第４受光
センサとの出力和との差により、前記光ディスク盤に記
録されている情報を検出し、前記第１受光センサと前記
第３受光センサとの出力和と前記第２受光センサと第４
受光センサとの出力和との差動により、トラッキングエ
ラー等トラック情報を検出し、前記第１受光センサと前
記第３受光センサまたは前記第２受光センサと前記第４
受光センサによりフォーカスエラー信号を検出するよう
に構成したことを特徴とする光ピックアップ。1. A light emitting element for irradiating an optical disk with linearly polarized light, an objective lens for condensing light from the light emitting element onto the optical disk, and a first for receiving reflected light from the optical disk. The light receiving sensor, the second light receiving sensor, the third light receiving sensor, and the fourth light receiving sensor are arranged between the light receiving sensor group and the objective lens, and guide light from the light emitting element to the objective lens. A transparent parallel plate light guide member that guides the reflected light from the optical disk board that has passed through the objective lens to the light receiving sensor group, and a plane located on the objective lens side of the planes of the light guide member is the first. When the second surface is a surface located on the side opposite to the optical disk board with respect to the first surface, and the reflected light from the optical disk board that has passed through the objective lens is n, Has a serial function and the diffraction angle and diffraction in the same direction having an angle with respect to the polarization direction (2n + 1) π / 4 of light from the light emitting element is converted into two different light,
A hologram having two different patterns with a dividing line in the same direction as the track direction of the optical disc as a boundary is provided on the first surface of the light guide member, and an entrance window for guiding light from the light emitting element to the hologram is provided. A first polarization splitting device, which is provided on the second surface of the light guide member, transmits the P-polarized light components of the two diffracted lights from the hologram to the first light-receiving sensor and the second light-receiving sensor, respectively, and reflects the S-polarized light component. Section and a second polarization splitting section are provided on the second surface of the light guide member, and the reflecting sections for reflecting the two reflected lights from the both polarization splitting sections to the third light receiving sensor and the fourth light receiving sensor, respectively. A transmission window provided on the first surface of the light guide member for guiding the two reflected lights from the reflection section to the third light receiving sensor and the fourth light receiving sensor is provided on the second surface of the light guide member, and Objective The two focal points of the two diffracted lights that have passed through the lens and the hologram are set so as to be present between the both polarization separation films and the third light receiving sensor and the fourth light receiving sensor, respectively, and the first light receiving is performed. The information recorded on the optical disk disc is detected by the difference between the output sum of the sensor and the second light receiving sensor and the output sum of the third light receiving sensor and the fourth light receiving sensor, and the first light receiving sensor is detected. And the output sum of the third light receiving sensor, the second light receiving sensor and the fourth
Track information such as a tracking error is detected by a difference from the output sum of the light receiving sensor, and the first light receiving sensor and the third light receiving sensor or the second light receiving sensor and the fourth light receiving sensor.
An optical pickup characterized in that a light receiving sensor is used to detect a focus error signal. 【請求項２】前記光ディスク盤のトラック方向と同一方
向の分割線を境界として２つの異なるパターンを持つ前
記ホログラムによって、前記対物レンズを通過した前記
光ディスク盤からの前記反射光を前記発光素子からの光
の偏光方向に対して（２ｎ＋１）π／４の角度を有する
異なった方向に回折し且つ回折角が同一の２つの光へ変
換することを特徴とする請求項１記載の光ピックアッ
プ。2. The reflected light from the optical disc plate that has passed through the objective lens is emitted from the light emitting element by the hologram having two different patterns with a dividing line in the same direction as the track direction of the optical disc disc as a boundary. 2. The optical pickup according to claim 1, wherein the light is diffracted into different directions having an angle of (2n + 1) π / 4 with respect to the polarization direction of the light and converted into two lights having the same diffraction angle. 【請求項３】前記光ガイド部材の前記第２面に接合され
た前記光ガイド部材の屈折率と同程度の屈折率を持つ偏
光分離補助部材を有することを特徴とする請求項１又は
請求項２記載の光ピックアップ。3. A polarization separation auxiliary member having a refractive index similar to that of the light guide member, which is joined to the second surface of the light guide member. The optical pickup described in 2. 【請求項４】前記発光素子、前記両受光センサが、セン
サ基板上に配置されていることを特徴とする請求項１又
は請求項２記載の光ピックアップ。4. The optical pickup according to claim 1, wherein the light emitting element and the both light receiving sensors are arranged on a sensor substrate. 【請求項５】前記ホログラムにより前記両透過光のＰ偏
光成分の内、一方の光の焦点が受光センサに対して上流
に、他方の光の焦点が受光センサに対して下流にあり、
かつ２つの光の受光センサ上の照射形状が同一になるよ
うにし、Ｐ偏光成分の光が照射する２つの受光センサで
フォーカスエラー信号を検出することを特徴とする請求
項１又は請求項２記載の光ピックアップ。5. Among the P-polarized light components of the both transmitted light by the hologram, one light has a focal point upstream of the light receiving sensor and the other light has a focal point downstream of the light receiving sensor,
3. The focus error signal is detected by the two light-receiving sensors that emit light of the P-polarized component so that the two light-receiving sensors have the same irradiation shape on the light-receiving sensor. Optical pickup. 【請求項６】前記ホログラムにより前記両透過光のＳ偏
光成分の内、一方の光の焦点が受光センサに対して上流
に、他方の光の焦点が受光センサに対して下流にあり、
かつ２つの光の受光センサ上の照射形状が同一になるよ
うにし、Ｓ偏光成分の光が照射する２つの受光センサで
フォーカスエラー信号を検出することを特徴とする請求
項１又は請求項２記載の光ピックアップ。6. The hologram has one of the S-polarized light components of the transmitted light having a focal point upstream of the light receiving sensor and the other light having a focal point downstream of the light receiving sensor.
3. The focus error signal is detected by the two light-receiving sensors that emit light of the S-polarized component so that the two light-receiving sensors have the same irradiation shape on the light-receiving sensor. Optical pickup.