JP2006209824A

JP2006209824A - Optical pickup

Info

Publication number: JP2006209824A
Application number: JP2005016937A
Authority: JP
Inventors: Yuichi Hasegawa; 祐一長谷川
Original assignee: Victor Company of Japan Ltd
Current assignee: Victor Company of Japan Ltd
Priority date: 2005-01-25
Filing date: 2005-01-25
Publication date: 2006-08-10

Abstract

<P>PROBLEM TO BE SOLVED: To solve problems of a conventional optical pickup wherein a special purpose photodetector is required for monitoring an outgoing beam resulting in causing disturbance for downsizing due to increase in the number of components and limitation of the arrangement, and variations in the luminous quantity from an objective lens is caused even when an outgoing beam quantity of a semiconductor laser is constant in the case of spherical aberration correction of the objective lens. <P>SOLUTION: A 1/4 wavelength plate 3 together with the objective lens 1 is mounted to a moving part of an objective lens actuator 2 in a way that an incident face is tilted with respect to a reference face of the objective lens 1. The 1/4 wavelength plate 3 is configured such that light is transmitted through a center part of the 1/4 wavelength plate 3 with a size corresponding to an effective diameter of the objective lens 1 and the other regions than the center part reflect the light. The photodetector 9 disclosed herein includes: a first photo-detection section for receiving a first reflection light reflected in an optical disk and transmitted through the center part of the 1/4 wavelength plate 3; and a second photo-detection section for receiving a second reflection light reflected in the other regions than the center part of the 1/4 wavelength plate 3. An optical output emitted from a light source is controlled in response to the luminous quantity of the second reflection light. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

本発明は光ピックアップに係り、特に光ディスクに対して情報信号を記録再生するための光ピックアップに関する。 The present invention relates to an optical pickup, and more particularly to an optical pickup for recording / reproducing information signals on / from an optical disc.

従来、光ピックアップ内の半導体レーザの出力を制御するために、当該半導体レーザから出射されたレーザ光の一部を、光出力のモニタ用として利用している。この光出力のモニタのために、レーザパッケージの内部に光モニタ用の受光素子を内蔵し、レーザチップの出射側と反対側に光が漏れるようにしたものがある。しかし、記録用の光ピックアップでは、出射側の光量を十分確保するため、また、記録用の光をパルスで制御するために、モニタ用の受光素子に、周波数帯域の高いものが必要などの理由から、レーザパッケージに内蔵した受光素子ではなく、出射側の光の一部の光路を分けて、専用の受光素子でモニタする方法が多く用いられている。モニタした光信号に基づいて、半導体レーザの駆動電流を制御することで半導体レーザの出力を制御することができる。 Conventionally, in order to control the output of the semiconductor laser in the optical pickup, a part of the laser light emitted from the semiconductor laser is used for monitoring the optical output. In order to monitor this light output, a light receiving element for light monitoring is built in the laser package so that light leaks to the side opposite to the emission side of the laser chip. However, in the optical pickup for recording, in order to secure a sufficient amount of light on the emission side and to control the recording light with pulses, the reason is that a light receiving element for monitoring requires a high frequency band Therefore, a method is often used in which a part of the light path of the light on the emission side is divided and monitored by a dedicated light receiving element instead of the light receiving element built in the laser package. Based on the monitored optical signal, the output of the semiconductor laser can be controlled by controlling the drive current of the semiconductor laser.

また、記録用光ディスクは、ＣＤ−Ｒから、ＤＶＤ(Digital Versatile Disc)、Ｂｌｕ−ｒａｙなど記録密度が高密度になるに従い、光ディスクの特性に対する要求が厳しくなると共に、記録再生におけるレーザパワーの制御も高精度化が求められている。 Further, as the recording optical disc becomes higher in recording density such as CD-R, DVD (Digital Versatile Disc), Blu-ray, etc., the requirements for the characteristics of the optical disc become stricter, and laser power control in recording and reproduction is also possible. High accuracy is required.

また、半導体レーザの出力を制御するための光検出器は、半導体レーザや、対物レンズ、ミラー等を取り付けている筐体の一部に固定されている。固定部から、対物レンズアクチュエータに向かう光は、対物レンズの移動を考慮し、対物レンズの有効径よりも大きい光束径で設定されている。光検出器は、対物レンズの有効径よりも大きい光束の部分で分割された光を使用して、半導体レーザの出力を制御している（例えば、特許文献１参照）。 A photodetector for controlling the output of the semiconductor laser is fixed to a part of a housing to which the semiconductor laser, an objective lens, a mirror, and the like are attached. The light traveling from the fixed portion toward the objective lens actuator is set with a light beam diameter larger than the effective diameter of the objective lens in consideration of the movement of the objective lens. The photodetector controls the output of the semiconductor laser using light divided by a portion of the light beam larger than the effective diameter of the objective lens (see, for example, Patent Document 1).

通常、光ピックアップは、半導体レーザからの光をレンズ、プリズム、ミラー等を介して、対物レンズに入射させ、対物レンズにより光ディスクの信号面上に集光されたスポットを、光ディスク上のトラックに追従するように、対物レンズを光ディスクのフォーカス方向、ラジアル方向の２軸に駆動するアクチュエータに搭載し、回転するディスクの面振れ、偏芯に追従して、対物レンズが移動するようにサーボがかけられている。 Usually, an optical pickup makes light from a semiconductor laser incident on an objective lens via a lens, prism, mirror, etc., and a spot focused on the signal surface of the optical disk by the objective lens follows a track on the optical disk. As described above, the objective lens is mounted on an actuator that drives the optical disk in the focus direction and the radial direction, and servo is applied so that the objective lens moves following the surface deflection and eccentricity of the rotating disk. ing.

しかしながら、光ディスクの周方向に光ピックアップを高速に移動させる場合に、アクチュエータ駆動部の慣性により、対物レンズが移動することがあり、これを検出する方法として、受光部と発光部を持った光センサ等を用いて対物レンズの位置を検出する方法などがとられている（例えば、特許文献２参照）。 However, when the optical pickup is moved at a high speed in the circumferential direction of the optical disk, the objective lens may move due to the inertia of the actuator driving unit. As a method for detecting this, an optical sensor having a light receiving unit and a light emitting unit. For example, a method of detecting the position of the objective lens using the above is used (see, for example, Patent Document 2).

図９は従来の光ピックアップの一例の構成図を示す。同図（Ａ）は対物レンズ３１付近の構成を示す平面図、同図（Ｂ）は検出光学系の構成図を示す。図９（Ａ）に示すように、対物レンズ３１は対物レンズアクチュエータ３３の可動部に固定されており、ミラー３２が対向して設けられている。 FIG. 9 shows a configuration diagram of an example of a conventional optical pickup. FIG. 2A is a plan view showing the configuration near the objective lens 31, and FIG. 2B is a configuration diagram of the detection optical system. As shown in FIG. 9A, the objective lens 31 is fixed to a movable portion of the objective lens actuator 33, and a mirror 32 is provided to face the objective lens 31.

図９（Ｂ）において、半導体レーザ３４から出射した光はコリメータレンズ３５により平行光束となり、ビームスプリッタ３６を透過してミラー３２により光路を変換され対物レンズ３１へと向かう。対物レンズ３１で集光された光は図示しない光ディスク上にスポットを形成し、信号の記録再生を行う。光ディスクで反射した光は、再び対物レンズ３１、ミラー３２を通り、ビームスプリッタ３６で反射して、集光レンズ３７、検出レンズ３８を透過して光検出器３９へと導かれる。一方、半導体レーザ３４の出力を制御するため、往路の光の一部をビームスプリッタ３６で反射し、光量モニタ用の光検出器４０へと入射させている。 In FIG. 9B, the light emitted from the semiconductor laser 34 becomes a parallel light beam by the collimator lens 35, passes through the beam splitter 36, changes the optical path by the mirror 32, and travels toward the objective lens 31. The light condensed by the objective lens 31 forms a spot on an optical disk (not shown) and performs signal recording / reproduction. The light reflected by the optical disk passes through the objective lens 31 and the mirror 32 again, is reflected by the beam splitter 36, passes through the condenser lens 37 and the detection lens 38, and is guided to the photodetector 39. On the other hand, in order to control the output of the semiconductor laser 34, a part of the outgoing light is reflected by the beam splitter 36 and is incident on the photodetector 40 for monitoring the light amount.

特開２００４−５８９４号公報JP 2004-5894 A 特開２０００−１１４０５号公報JP 2000-11405 A

しかし、従来の光ピックアップでは、半導体レーザの光量をモニタするために、半導体レーザから光ディスクに向かう光の一部の光路を分割して取り出すため、半導体レーザの出射光をすべて使うことができない。また、出射光をモニタするために、専用に光検出器を配置する必要があり、部品点数の増加、配置の制限による小型化の妨げになっている。更に、対物レンズの移動を検出するためには、受光部と発光部を持った光センサ等を、対物レンズアクチュエータに搭載する必要があり、これも、部品点数の増加、配置の制限による小型化の妨げになる。 However, in the conventional optical pickup, in order to monitor the light amount of the semiconductor laser, a part of the optical path from the semiconductor laser toward the optical disk is divided and extracted, so that all the emitted light of the semiconductor laser cannot be used. Moreover, in order to monitor the emitted light, it is necessary to arrange a dedicated photodetector, which hinders miniaturization due to an increase in the number of parts and restriction of arrangement. Furthermore, in order to detect the movement of the objective lens, it is necessary to mount an optical sensor or the like having a light receiving part and a light emitting part on the objective lens actuator, which is also reduced in size by increasing the number of parts and restricting the arrangement. It becomes an obstacle.

また、従来の光ピックアップでは、対物レンズの位置によらず、固定部で半導体レーザの出射光量の一部をモニタして、出力を制御している。しかし、対物レンズに入射する光束は、半導体レーザの出射パターンと、コリメーション等の光学的な条件により、光量の分布をもっている。従って、半導体レーザからの出射光量は一定であっても、対物レンズから出射される光量は、対物レンズのトラッキング方向の位置により、僅かであるが変動をきたしてしまう。 Further, in the conventional optical pickup, the output is controlled by monitoring a part of the emitted light amount of the semiconductor laser at the fixed portion regardless of the position of the objective lens. However, the light beam incident on the objective lens has a light amount distribution due to the emission pattern of the semiconductor laser and optical conditions such as collimation. Therefore, even if the amount of light emitted from the semiconductor laser is constant, the amount of light emitted from the objective lens varies slightly depending on the position of the objective lens in the tracking direction.

また、Ｂｌｕ−ｒａｙなどの高密度ディスクでは、記録密度を上げるため、対物レンズに開口数が０.８５程度の非常に高いものが使用されている。このような光学系では、使用するディスクの厚さ誤差や、半導体レーザの波長ばらつきに対応するために、球面収差を補正する光学系が必要となる。 Further, in a high-density disc such as Blu-ray, a very high objective lens having a numerical aperture of about 0.85 is used for increasing the recording density. In such an optical system, an optical system for correcting spherical aberration is required in order to cope with the thickness error of the disk used and the wavelength variation of the semiconductor laser.

球面収差を補正する方法として、負のパワーをもつレンズと正のパワーをもつレンズを組合せ、両者のレンズ間隔を可動とすることにより、対物レンズに入射する光束を、平行から、拡散、収束に変化させることで、ディスクの厚み誤差や、半導体レーザの波長ばらつきにより発生する球面収差を、対物レンズの倍率誤差により発生する球面収差によりキャンセルすることにより補正する方法が用いられることが多い。しかしながら、このような補正方法では、上記のレンズ間隔を変えることで、対物レンズに入射する光束が平行光束から変動する分、半導体レーザの出力が一定であっても、対物レンズから出射される光量が変動してしまう。 As a method for correcting spherical aberration, a lens having negative power and a lens having positive power are combined, and the distance between the lenses is movable, so that the light beam incident on the objective lens can be changed from parallel to diffused and converged. In many cases, a method is used in which the spherical aberration caused by the disc thickness error or the semiconductor laser wavelength variation is corrected by canceling the spherical aberration caused by the magnification error of the objective lens. However, in such a correction method, the amount of light emitted from the objective lens is changed even if the output of the semiconductor laser is constant because the light flux incident on the objective lens varies from the parallel light flux by changing the lens interval. Will fluctuate.

本発明は以上の点に鑑みなされたもので、半導体レーザから出射した光を、有効に使用すると共に、専用の受光素子を必要とせず、部品点数の削除、小型化を実現し得る光ピックアップを提供することを目的とする。 The present invention has been made in view of the above points, and an optical pickup capable of effectively using light emitted from a semiconductor laser, eliminating the need for a dedicated light receiving element, and reducing the number of parts and reducing the size. The purpose is to provide.

また、本発明の他の目的は、対物レンズの移動や、球面収差補正等の光学系に変化がある場合にも、対物レンズから出射する光量が一定になるよう、半導体レーザの出力を制御する光ピックアップを提供することにある。 Another object of the present invention is to control the output of the semiconductor laser so that the amount of light emitted from the objective lens is constant even when there is a change in the optical system such as movement of the objective lens or spherical aberration correction. It is to provide an optical pickup.

上記の目的を達成するため、第１の発明は、光源から出射した光を対物レンズに入射して光ディスク上に集光させることにより情報信号を記録し、又は光ディスクからの反射光を対物レンズを通して検出光学系に入射して記録情報信号を再生する光ピックアップにおいて、対物レンズの光ディスク側とは反対側面に対して光軸上離間対向する位置に、かつ、対物レンズの基準面に対して入射面が傾斜するように、対物レンズと共に対物レンズアクチュエータの可動部に１／４波長板を搭載し、１／４波長板は、入射面の対物レンズの有効径に対応した大きさの中央部に光を透過させて１／４波長板として機能させ、かつ、入射面の中央部以外の領域は光を反射させる構成とし、検出光学系内の光検出器は、光ディスクで反射し、かつ、１／４波長板の中央部を透過した第１の反射光を受光する第１の光検出部と、１／４波長板の中央部以外の領域で反射した第２の反射光を受光する第２の光検出部とを有し、第２の反射光の光量に応じて、光源から出射する光出力を制御することを特徴とする。 In order to achieve the above object, the first invention records an information signal by making light emitted from a light source incident on an objective lens and condensing it on the optical disk, or reflecting reflected light from the optical disk through the objective lens. In an optical pickup that reproduces a recorded information signal by being incident on a detection optical system, the incident surface is located at a position opposed to the side surface opposite to the optical disk side of the objective lens on the optical axis and with respect to the reference surface of the objective lens The quarter wavelength plate is mounted on the movable part of the objective lens actuator together with the objective lens so that the optical axis is inclined, and the quarter wavelength plate is light-transmitted at the center part of the size corresponding to the effective diameter of the objective lens on the incident surface. And a region other than the central portion of the incident surface is configured to reflect light, and a photodetector in the detection optical system is reflected by the optical disc, and 1 / 4 A first light detector that receives the first reflected light that has passed through the central portion of the long plate, and a second light that receives the second reflected light that has been reflected in a region other than the central portion of the quarter-wave plate. And detecting a light output from the light source in accordance with the amount of the second reflected light.

この発明では、所定の構成とした１／４波長板を対物レンズの光ディスク側とは反対側面に対して光軸上離間対向する位置に、かつ、対物レンズの基準面に対して入射面が傾斜するように、対物レンズと共に対物レンズアクチュエータの可動部に１／４波長板を搭載するようにしたため、一つの光検出器が、少なくとも光ディスクの信号を読み取るための第１の光検出部と、光源の光出力を制御するためのモニタ用の第２の光検出部とを備えることができる。 In the present invention, the 1/4 wavelength plate having a predetermined configuration is positioned at a position facing the optical axis away from the side surface opposite to the optical disk side of the objective lens, and the incident surface is inclined with respect to the reference plane of the objective lens. As described above, since the quarter wavelength plate is mounted on the movable portion of the objective lens actuator together with the objective lens, one photodetector detects at least a signal of the optical disc, and a light source. And a second light detection unit for monitoring for controlling the light output of the light source.

また、上記の目的を達成するため、第２の発明は、第１の発明の第２の光検出部を、前記光ディスクのトラック方向に２分割された２分割受光部を有する構成とし、これら２分割受光部でそれぞれ受光して得られた２受光信号の差を演算して対物レンズのトラッキング方向の移動を検出する第１の演算手段と、上記の２受光信号の和を演算して光源から出射する光出力を制御するための信号を生成する第２の演算手段とを更に有することを特徴とする。この発明では、光源の光出力を制御するためのモニタ用の第２の光検出部を、対物レンズのトラッキング方向の移動検出用としても兼用できる。 In order to achieve the above object, according to a second aspect of the present invention, the second photodetecting section according to the first aspect of the present invention includes a two-divided light receiving section that is divided into two in the track direction of the optical disc. A first calculation means for calculating a difference between two light reception signals obtained by receiving light at the divided light receiving portions and detecting movement of the objective lens in the tracking direction, and calculating a sum of the two light reception signals from the light source. And a second calculating means for generating a signal for controlling the emitted light output. In the present invention, the second light detection unit for monitoring for controlling the light output of the light source can also be used for detecting the movement of the objective lens in the tracking direction.

また、上記の目的を達成するため、第３の発明は、光源から出射した光を対物レンズに入射して光ディスク上に集光させることにより情報信号を記録し、又は光ディスクからの反射光を対物レンズを通して検出光学系に入射して記録情報信号を再生する光ピックアップにおいて、対物レンズの光ディスク側とは反対側面に対して光軸上離間対向する位置に１／４波長板を設けると共に、対物レンズの有効径に対応した大きさの１／４波長板の中央部では光を透過させて１／４波長板として機能させ、かつ、１／４波長板の入射面の中央部以外の領域は光を反射させる構成とし、検出光学系には、少なくとも入射光の偏光方向が光源から出射する直線偏光と同じときにはその光量の大部分を反射し、かつ、光量の一部を透過する特性を有するミラーと、ミラーを透過した光源から出射して対物レンズに向かう直線偏光を受光する第１の光検出器と、１／４波長板の中央部以外の領域で反射してミラーを透過した第２の反射光を受光する第２の光検出器とを有し、第１の光検出器は、対物レンズに向かう光束の全体をモニタし、第２の光検出器は、対物レンズの有効径に入射しない部分に相当する光をモニタし、第１及び第２の光検出器の出力信号を演算して得た信号に基づき、光源から出射する光出力を制御することを特徴とする。 In order to achieve the above object, the third invention records an information signal by making light emitted from a light source incident on an objective lens and condensing it on an optical disk, or reflecting light reflected from an optical disk as an object. In an optical pickup that reproduces a recorded information signal by being incident on a detection optical system through a lens, a quarter wavelength plate is provided at a position facing and spaced apart from the optical disk side of the objective lens on the optical axis, and the objective lens In the central part of the quarter-wave plate having a size corresponding to the effective diameter of light, light is transmitted to function as a quarter-wave plate, and the area other than the central part of the incident surface of the quarter-wave plate is light. The detection optical system has a characteristic that reflects most of the light amount and transmits a part of the light amount when at least the polarization direction of the incident light is the same as the linearly polarized light emitted from the light source. And a first photodetector that receives linearly polarized light emitted from the light source that has passed through the mirror and directed toward the objective lens, and a second that is reflected by a region other than the central portion of the quarter-wave plate and is transmitted through the mirror. And a second photodetector that receives the reflected light, and the first photodetector monitors the entire luminous flux directed to the objective lens, and the second photodetector has an effective diameter of the objective lens. The light corresponding to the non-incident portion is monitored, and the light output emitted from the light source is controlled based on the signals obtained by calculating the output signals of the first and second photodetectors.

この発明では、所定の特性としたミラーを透過した光源から出射して対物レンズに向かう直線偏光を受光する第１の光検出器と、１／４波長板の中央部以外の領域で反射してミラーを透過した第２の反射光を受光する第２の光検出器とを有し、第１の光検出器は、対物レンズに向かう光束の全体をモニタし、第２の光検出器は、対物レンズの有効径に入射しない部分に相当する光をモニタするようにしたため、第１及び第２の光検出器の出力信号を演算して対物レンズの有効径に入射する光に相当する光量を検出し、その検出信号に基づき、光源から出射する光出力を制御することができる。 In this invention, the light is reflected by a first photodetector that receives linearly polarized light that is emitted from a light source that has passed through a mirror having a predetermined characteristic and is directed toward the objective lens, and is reflected by a region other than the central portion of the quarter-wave plate. A second photodetector that receives the second reflected light that has passed through the mirror, the first photodetector monitors the entire luminous flux directed to the objective lens, and the second photodetector comprises: Since the light corresponding to the portion not incident on the effective diameter of the objective lens is monitored, the output signals of the first and second photodetectors are calculated to obtain the light amount corresponding to the light incident on the effective diameter of the objective lens. Based on the detected signal, the light output emitted from the light source can be controlled.

本発明によれば、一つの光検出器が、光ディスクの信号を読み取るための第１の光検出部と、光源の光出力を制御するためのモニタ用の第２の光検出部とを備える構成としたため、光源から出射した光を、有効に使用できると共に、光出力のモニタや対物レンズの移動検出用に専用の受光素子を不要とし、光ピックアップの部品点数を従来に比べて削減できると共に小型化を実現できる。 According to the present invention, one photodetector includes a first photodetector for reading a signal from an optical disc and a second photodetector for monitoring for controlling the light output of the light source. Therefore, the light emitted from the light source can be used effectively, and a dedicated light receiving element is not required for monitoring the optical output and detecting the movement of the objective lens, reducing the number of parts of the optical pickup and reducing the size Can be realized.

また、本発明によれば、対物レンズに向かう光束の全体をモニタする第１の光検出器の出力信号と、対物レンズの有効径に入射しない部分に相当する光をモニタする第２の光検出器の出力信号を演算して対物レンズの有効径に入射する光に相当する光量を検出し、その検出信号に基づき、光源から出射する光出力を制御するようにしたため、トラッキングによる対物レンズの移動や、光学系による対物レンズへ入射する光束の変化に対応して、対物レンズからの出射光量を一定になるように、半導体レーザの光出力を細かく制御することができる。 Further, according to the present invention, the output signal of the first photodetector that monitors the entire light beam directed toward the objective lens and the second light detection that monitors the light corresponding to the portion not incident on the effective diameter of the objective lens. The light output corresponding to the light incident on the effective diameter of the objective lens is detected by calculating the output signal of the detector, and the light output emitted from the light source is controlled based on the detection signal. In addition, the light output of the semiconductor laser can be finely controlled so that the amount of light emitted from the objective lens becomes constant in response to the change in the light beam incident on the objective lens by the optical system.

次に、本発明の実施の形態について図面と共に説明する。 Next, embodiments of the present invention will be described with reference to the drawings.

（第１の実施の形態）
図１は本発明になる光ピックアップの第１の実施の形態の構成図を示し、同図（Ａ）は対物レンズ付近の構成を示す上面図、同図（Ｂ）は光ピックアップ内の半導体レーザ６からミラー４及び光検出器９までの検出光学系の構成図を示す。本実施の形態では、図１（Ａ）に示すように、対物レンズ１を駆動する対物レンズアクチュエータ２の可動部に、１／４波長板３を所定の角度傾けて取り付けている。図１（Ｂ）に示す検出光学系は、光ディスクからの反射光を受光する領域と、所定の距離に１／４波長板３からの反射光を受光する領域をもつ。１／４波長板３は対物レンズ１に対して傾いているため、光ディスクからの反射光と分離して、１／４波長板３からの反射光を検出することができる。 (First embodiment)
FIG. 1 shows a configuration diagram of a first embodiment of an optical pickup according to the present invention, FIG. 1A is a top view showing a configuration near an objective lens, and FIG. 1B is a semiconductor laser in the optical pickup. 6 shows a configuration diagram of a detection optical system from 6 to the mirror 4 and the photodetector 9. FIG. In the present embodiment, as shown in FIG. 1A, a quarter wavelength plate 3 is attached to a movable portion of an objective lens actuator 2 that drives the objective lens 1 at a predetermined angle. The detection optical system shown in FIG. 1B has a region for receiving reflected light from the optical disc and a region for receiving reflected light from the quarter-wave plate 3 at a predetermined distance. Since the quarter wavelength plate 3 is inclined with respect to the objective lens 1, it is possible to detect the reflected light from the quarter wavelength plate 3 separately from the reflected light from the optical disk.

すなわち、図１（Ｂ）において、半導体レーザ６から出射した光は、コリメータレンズ５により平行光束に変換され、回折格子１１、偏光ビームスプリッタ１０を透過し、ミラー４で反射して、図１（Ａ）に示す対物レンズアクチュエータ２へ導かれる。対物レンズアクチュエータ２は、図示しない光ディスクに対して、フォーカス方向、トラッキング方向の２軸に駆動できる可動部をもち、その可動部には、光ディスクの信号面に光を集光させるための対物レンズ１と、１／４波長板３が搭載されている。 That is, in FIG. 1B, light emitted from the semiconductor laser 6 is converted into a parallel light beam by the collimator lens 5, passes through the diffraction grating 11 and the polarization beam splitter 10, and is reflected by the mirror 4. It is guided to the objective lens actuator 2 shown in A). The objective lens actuator 2 has a movable part that can be driven in two directions in the focus direction and the tracking direction with respect to an optical disk (not shown), and the objective lens 1 for condensing light on the signal surface of the optical disk in the movable part. A quarter-wave plate 3 is mounted.

これにより、ミラー４で反射した光は、対物レンズアクチュエータ２の可動部に搭載された１／４波長板３で円偏光にされた後、対物レンズ１により図示しない光ディスクの信号面に集光して光スポットを形成する。光ディスクで反射した光は、再び対物レンズ１を通り、１／４波長板３で偏光を直線偏光とされる。偏光方向は往路のミラー４で反射した光に対して９０度変えられる。 As a result, the light reflected by the mirror 4 is circularly polarized by the quarter wavelength plate 3 mounted on the movable part of the objective lens actuator 2 and then condensed on the signal surface of the optical disk (not shown) by the objective lens 1. To form a light spot. The light reflected by the optical disk passes through the objective lens 1 again, and is converted into linearly polarized light by the quarter wavelength plate 3. The polarization direction is changed by 90 degrees with respect to the light reflected by the forward mirror 4.

１／４波長板３で直線偏光とされた光ディスクからの反射光は、図１（Ｂ）に示すように、ミラー４で反射して光路が変えられ、更に偏光ビームスプリッタ１０で反射し、集光レンズ７で集光されて、検出レンズ８を透過して光検出器９へと導かれ、光電変換され、得られた電気信号に基づいて読み取り信号が得られると共にサーボ信号が生成される。 As shown in FIG. 1B, the reflected light from the optical disk that has been linearly polarized by the quarter wavelength plate 3 is reflected by the mirror 4 to change the optical path, and further reflected by the polarization beam splitter 10 to be collected. The light is condensed by the optical lens 7, is transmitted through the detection lens 8, is guided to the photodetector 9, is photoelectrically converted, and a read signal is obtained and a servo signal is generated based on the obtained electrical signal.

この実施の形態では、対物レンズアクチュエータ２をフォーカス方向、トラッキング方向に駆動するための、サーボ信号を生成する方法として、公知のフォーカスに非点収差法、トラッキングに公知の差動プッシュプル法を用いている。 In this embodiment, as a method of generating a servo signal for driving the objective lens actuator 2 in the focus direction and the tracking direction, an astigmatism method is used for a known focus, and a known differential push-pull method is used for tracking. ing.

ここで、前記１／４波長板３は、対物レンズアクチュエータ２の可動部に、対物レンズ１と対向して取り付けられ、また、図２に示すように、対物レンズ１の基準面に対して、光ディスクのラジアル方向に所定の角度θ傾けて取り付けられている。 Here, the ¼ wavelength plate 3 is attached to the movable part of the objective lens actuator 2 so as to face the objective lens 1, and as shown in FIG. The optical disk is mounted at a predetermined angle θ in the radial direction.

また、１／４波長板３は、図３（Ａ）の平面図に示すように、中心部の対物レンズ１の有効径に相当する領域３ａには、光を透過するように反射防止膜１５が施され、また、同図（Ｂ）の側面図に示すように、両面共に反射防止膜１５が施され、通常の１／４波長板の効果をもたせる構成としている。なお、１／４波長板３の光源側の面（図３（Ｂ）の下側の面）の全面に反射防止膜１５が形成されている。 Further, as shown in the plan view of FIG. 3A, the quarter-wave plate 3 has an antireflection film 15 so as to transmit light to a region 3a corresponding to the effective diameter of the objective lens 1 at the center. In addition, as shown in the side view of FIG. 5B, both surfaces are provided with an antireflection film 15 so as to have the effect of a normal quarter wavelength plate. An antireflection film 15 is formed on the entire surface of the quarter-wave plate 3 on the light source side (the lower surface in FIG. 3B).

一方、図３（Ａ）の平面図及び図３（Ｂ）の側面図に示すように、１／４波長板３の外周部の領域３ｂで、対物レンズ１に近い側の面には全反射膜１６が施され、対物レンズ１の有効径よりも外側の部分の光は当該全反射膜１６で反射して、検出光学系へ向かう構成としている。なお、１／４波長板３は対物レンズアクチュエータ２の可動部に取り付けられているが、全反射膜１６は対物レンズアクチュエータ２の可動部に設けてもよい。 On the other hand, as shown in the plan view of FIG. 3A and the side view of FIG. 3B, total reflection is performed on the surface near the objective lens 1 in the region 3 b of the outer peripheral portion of the quarter-wave plate 3. A film 16 is applied, and light outside the effective diameter of the objective lens 1 is reflected by the total reflection film 16 and travels toward the detection optical system. Although the quarter wavelength plate 3 is attached to the movable part of the objective lens actuator 2, the total reflection film 16 may be provided on the movable part of the objective lens actuator 2.

光ピックアップの、ミラー４から対物レンズアクチュエータ２に向かう部分の光束は、対物レンズ１の、トラッキング方向の移動などを考慮して、対物レンズ１の有効径よりも大きい光束が入射している。このため、通常は、対物レンズアクチュエータ２の可動部に対物レンズ１の有効径に相当する絞りを設けている。 The light beam of the portion of the optical pickup from the mirror 4 toward the objective lens actuator 2 is incident with a light beam larger than the effective diameter of the objective lens 1 in consideration of the movement of the objective lens 1 in the tracking direction. For this reason, normally, a diaphragm corresponding to the effective diameter of the objective lens 1 is provided in the movable part of the objective lens actuator 2.

これに対し、本実施の形態では、絞りの外側の光、すなわち、対物レンズ１の有効径よりも外側の部分の光は１／４波長板３を透過した後に全反射膜１６で反射させ、その反射光を更にミラー４で反射し、図１（Ｂ）に示した偏光ビームスプリッタ１０で反射して、集光レンズ７及び検出レンズ８を介して光検出器９に導かれる。すなわち、本実施の形態では、図２に示すように１／４波長板３を傾けて、全反射膜１６で反射された光は、１／４波長板３を２度通過して、偏光方向が９０度変換された直線偏光となる。反射光は１／４波長板３の傾き角の２倍（すなわち、２θ）傾いて検出光学系へ導かれる。 On the other hand, in the present embodiment, the light outside the stop, that is, the light outside the effective diameter of the objective lens 1 is reflected by the total reflection film 16 after passing through the quarter-wave plate 3, The reflected light is further reflected by the mirror 4, reflected by the polarizing beam splitter 10 shown in FIG. 1B, and guided to the photodetector 9 through the condenser lens 7 and the detection lens 8. In other words, in the present embodiment, as shown in FIG. 2, the quarter wavelength plate 3 is tilted, and the light reflected by the total reflection film 16 passes through the quarter wavelength plate 3 twice and the polarization direction. Becomes linearly polarized light converted by 90 degrees. The reflected light is guided to the detection optical system with an inclination twice (that is, 2θ) of the inclination angle of the quarter-wave plate 3.

また、１／４波長板３は図２に示したように、対物レンズ１の基準面に対して所定の角度θ傾けられているため、光検出器上９では、１／４波長板３の中央部の領域３ａを透過した、光ディスクから反射した光が集光される位置に対して、全反射膜１６で反射された光は異なる位置にスポットが集光される。 Further, as shown in FIG. 2, the quarter wavelength plate 3 is inclined at a predetermined angle θ with respect to the reference plane of the objective lens 1. In contrast to the position where the light reflected from the optical disk that has passed through the central region 3a is collected, the light reflected by the total reflection film 16 is condensed at a different position.

図４は本実施の形態の光ピックアップで使用する光検出器９の受光部を示すものである。同図に示すように、光検出器９は、中央の４分割光検出部９ａと、上下に配置された２つの２分割光検出部９ｂ及び９ｃと、４分割光検出部９ａに対して所定距離、離れた位置に配置された非分割光検出部９ｄとからなる。 FIG. 4 shows a light receiving portion of the photodetector 9 used in the optical pickup of the present embodiment. As shown in the figure, the photodetector 9 has a predetermined configuration with respect to the central 4-split light detection unit 9a, the two 2-split light detection units 9b and 9c arranged above and below, and the 4-split light detection unit 9a. It consists of a non-divided light detector 9d arranged at a distance and a distant position.

４分割光検出部９ａは、１／４波長板３の中央部の領域３ａを透過した、光ディスクから反射した光（０次回折光であるメイン光）を、４つの受光部でそれぞれ受光してそれぞれ光電変換し、得られた４信号に基づいて、光ディスクに記録されている情報信号を読み取ると共に、非点収差法によるフォーカスサーボ信号を生成させる。また、２分割光検出部９ｂ及び９ｃは、上記の光ディスクから反射した光（±１次回折光であるサブ光）を、各２つの受光部でそれぞれ受光してそれぞれ光電変換し、得られた各２信号に基づいて、差動プッシュプル法によるトラッキングエラー信号を生成させる。 The 4-split light detector 9a receives the light (main light, which is 0th-order diffracted light) that has passed through the central region 3a of the quarter-wave plate 3 and reflected from the optical disk, and receives the light by the four light receivers. Based on the four signals obtained by photoelectric conversion, an information signal recorded on the optical disk is read and a focus servo signal is generated by the astigmatism method. Each of the two-divided light detectors 9b and 9c receives the light reflected from the optical disc (sub-light, which is ± first-order diffracted light) by each of the two light receiving units, and performs photoelectric conversion. Based on the two signals, a tracking error signal by the differential push-pull method is generated.

更に、非分割光検出部９ｄは、上記１／４波長板３の全反射膜１６で反射した光を受光する検出部で、その入射光を光電変換して得られた信号を用いて、半導体レーザ６の駆動電流を制御することで、その光出力パワーを制御する。 Further, the non-divided light detection unit 9d is a detection unit that receives light reflected by the total reflection film 16 of the quarter-wave plate 3, and uses a signal obtained by photoelectrically converting the incident light, thereby using a semiconductor. The optical output power is controlled by controlling the drive current of the laser 6.

なお、光検出器９は、図５に示すように、図４に示した非分割光検出部９ｄの替わりに、光ディスク上のトラック方向に対して２分割した受光部９ｅ１、９ｅ２を持つ２分割光検出部９ｅを設ける構成でもよい。この例では、対物レンズ１がトラッキング方向（ラジアル方向）に移動した場合に、２分割光検出部９ｅの２つの受光部９ｅ１、９ｅ２でそれぞれ受光して光電変換して得た信号の差を、差動アンプ１７で演算し、その差信号に基づいて、対物レンズ１のトラッキング方向の移動量を検出することが可能となる。また、２つの受光部９ｅ１、９ｅ２でそれぞれ受光して光電変換して得た信号を加算器１８で加算して得た信号に基づいて、半導体レーザ６の光出力を制御する。 As shown in FIG. 5, the photodetector 9 is divided into two parts having light receiving parts 9e1 and 9e2 divided into two in the track direction on the optical disc instead of the non-divided light detection part 9d shown in FIG. The structure which provides the photon detection part 9e may be sufficient. In this example, when the objective lens 1 moves in the tracking direction (radial direction), the difference between signals obtained by photoelectrically receiving and photoelectrically receiving the light by the two light receiving portions 9e1 and 9e2 of the two-split light detection portion 9e, The amount of movement of the objective lens 1 in the tracking direction can be detected based on the difference signal calculated by the differential amplifier 17. Further, the optical output of the semiconductor laser 6 is controlled based on the signal obtained by adding the signals obtained by photoelectrically converting the light received by the two light receiving portions 9e1 and 9e2 by the adder 18.

なお、１／４波長板３を１度（θ＝１°）傾けて配置し、検出光学系の焦点距離を２０ｍｍとした場合、１／４波長板３で反射した光は、０.７（＝２０・ｔａｎ２°）ｍｍだけ、光ディスクの反射光から得られるメインのスポットから離れた位置にスポットを作る。 When the quarter wavelength plate 3 is inclined by 1 degree (θ = 1 °) and the focal length of the detection optical system is 20 mm, the light reflected by the quarter wavelength plate 3 is 0.7 ( = 20 · tan 2 °) A spot is created at a position away from the main spot obtained from the reflected light of the optical disk.

このように、本実施の形態によれば、一つの光検出器９が、光ディスクの信号を読み取ると共に対物レンズ１の光ディスクに対するフォーカス位置を検出するための４分割光検出部９ａと、対物レンズ１の光ディスク上のトラックに対するトラッキング位置を検出するための２分割光検出部９ｂ及び９ｃと、半導体レーザ６の光出力を制御するためのモニタ用の光検出部９ｄ又は９ｅとを備えて、光ディスクの信号読み取りと、フォーカス位置及びトラッキング位置の検出と、モニタ用とを兼用することができる。 As described above, according to the present embodiment, the single photodetector 9 reads the signal of the optical disc and detects the focus position of the objective lens 1 with respect to the optical disc, and the objective lens 1. A two-part light detectors 9b and 9c for detecting a tracking position with respect to a track on the optical disk, and a monitor light detector 9d or 9e for controlling the light output of the semiconductor laser 6; The signal reading, the detection of the focus position and the tracking position, and the monitor can be combined.

従って、本実施の形態によれば、半導体レーザ６から出射した光を、有効に使用できると共に、光出力のモニタや対物レンズの移動検出用に専用の受光素子を必要としないため、光ピックアップの部品点数を従来に比べて削減できると共に小型化を実現できる。 Therefore, according to the present embodiment, the light emitted from the semiconductor laser 6 can be used effectively, and a dedicated light receiving element is not required for monitoring the optical output and detecting the movement of the objective lens. The number of parts can be reduced as compared with the conventional one and the size can be reduced.

（第２の実施の形態）
図６は本発明になる光ピックアップの第２の実施の形態の構成図を示し、同図（Ａ）は対物レンズ付近の構成を示す上面図、同図（Ｂ）は光ピックアップ内の半導体レーザ６からミラー２３及び光検出器２６までの検出光学系の構成図を示す。同図中、図１と同一構成部分には同一符号を付してある。 (Second Embodiment)
FIG. 6 shows a configuration diagram of a second embodiment of an optical pickup according to the present invention, FIG. 6A is a top view showing a configuration in the vicinity of the objective lens, and FIG. 6B is a semiconductor laser in the optical pickup. 6 shows a configuration diagram of a detection optical system from 6 to a mirror 23 and a photodetector 26. FIG. In the figure, the same components as those in FIG.

図６において、半導体レーザ６から出射した光はコリメータレンズ５により平行光束となり、偏光ビームスプリッタ１０を透過し、球面収差補正のための、ビームエキスパンダ２５に入射する。ビームエキスパンダ２５は凹レンズと凸レンズの組合せで構成されており、両レンズの間隔が、光軸方向に移動可能になっており、光ディスク１００の厚み誤差、半導体レーザ６の波長ばらつきに応じて、出射する光束の平行度を変化させることができる。 In FIG. 6, the light emitted from the semiconductor laser 6 is converted into a parallel light beam by the collimator lens 5, passes through the polarization beam splitter 10, and enters the beam expander 25 for correcting spherical aberration. The beam expander 25 is composed of a combination of a concave lens and a convex lens, and the distance between the two lenses is movable in the optical axis direction. It is possible to change the parallelism of the luminous flux.

ビームエキスパンダ２５を出た光は、ミラー２３により光路を曲げられ、対物レンズアクチュエータ２０に向かう。ここで、ミラー２３は、入射する光がＰ偏光のときには、Ｐ偏光の大部分を反射するが一部を透過し、入射する光がＳ偏光のときには、入射光を全反射するような膜で構成されている。例えば、ミラー２３は、Ｐ偏光については透過率Ｔｐが９５％、反射率Ｒｐが５％である膜で、Ｓ偏光については透過率Ｔｓが０％、反射率Ｒｓが１００％である膜により構成されている。 The light exiting the beam expander 25 is bent in the optical path by the mirror 23 and travels toward the objective lens actuator 20. Here, when the incident light is P-polarized light, the mirror 23 is a film that reflects most of the P-polarized light but transmits a part thereof, and when the incident light is S-polarized light, totally reflects the incident light. It is configured. For example, the mirror 23 is a film having a transmittance Tp of 95% and a reflectance Rp of 5% for P-polarized light, and a film having a transmittance Ts of 0% and a reflectance Rs of 100% for S-polarized light. Has been.

従って、ビームエキスパンダ２５を出て上記の構成のミラー２３に入射する光はＰ偏光であるので、ミラー２３で大部分が反射して図６（Ａ）に示した対物レンズアクチュエータ２０に向かうが、一部が透過して、図６（Ａ）及び（Ｂ）に示すように、ミラー２３の先に配置された第一の光検出器２４ａの受光面に図７に２７で示す光スポットを形成して受光される。この第一の光検出器２４ａには、対物レンズアクチュエータ２０に向かう光束の全体に相当する光の５％が入射することになる。 Accordingly, since the light that exits the beam expander 25 and enters the mirror 23 having the above-described configuration is P-polarized light, most of the light is reflected by the mirror 23 and travels toward the objective lens actuator 20 shown in FIG. A part of the light spot is transmitted, and as shown in FIGS. 6A and 6B, a light spot indicated by 27 in FIG. 7 is formed on the light receiving surface of the first photodetector 24a disposed at the tip of the mirror 23. Form and receive light. 5% of the light corresponding to the entire light beam traveling toward the objective lens actuator 20 is incident on the first photodetector 24a.

一方、ミラー２３により反射されて対物レンズアクチュエータ２０に向かった光は、対物レンズ１の有効径に相当する部分の光は、１／４波長板２２により直線偏光が円偏光に変換された後、対物レンズ１により光ディスク１００上に集光されて信号を記録、または、ディスクの信号を再生するために使用される。 On the other hand, the light reflected by the mirror 23 toward the objective lens actuator 20 is a portion of the light corresponding to the effective diameter of the objective lens 1 after the linearly polarized light is converted into circularly polarized light by the quarter wavelength plate 22. The light is condensed on the optical disk 100 by the objective lens 1 and used for recording a signal or reproducing the signal of the disk.

ここで、対物レンズアクチュエータ２０の可動部には、対物レンズ１の有効径の外側の部分の光を反射する反射部２１が設けられているため、対物レンズ１に向かう光のうち、対物レンズ１の有効径の外側の部分の光は反射部２１により反射して、ミラー２３に戻る。ミラー２３はＰ偏光の一部を透過するようになっているため、反射部２２で反射された光はＰ偏光であるので、その５％は、ミラー２３を透過して、第二の光検出器２４ｂに入射し、その受光面に図７に２８で示す光スポットを形成して受光される。 Here, since the movable portion of the objective lens actuator 20 is provided with a reflection portion 21 that reflects the light of the portion outside the effective diameter of the objective lens 1, the objective lens 1 out of the light toward the objective lens 1. The light outside the effective diameter is reflected by the reflecting portion 21 and returns to the mirror 23. Since the mirror 23 transmits a part of the P-polarized light, the light reflected by the reflecting portion 22 is the P-polarized light, so that 5% of the light passes through the mirror 23 and is detected by the second light. 7 is incident on the light receiving surface 24b, and a light spot indicated by 28 in FIG.

この例では、対物レンズアクチュエータ２０の可動部に１／４波長板２２が取り付けられているが、上記の反射部２１は、１／４波長板２２よりも、ミラー２３側に設けられる必要がある。反射した光がＰ偏光である必要があるからである。１／４波長板２２を透過した光は、直線偏光（ここではＰ偏光）から円偏光になって対物レンズ１に入射するが、光ディスク１００で反射した光は、１／４波長板２２を透過することで再び円偏光から直線偏光になる。 In this example, the quarter wavelength plate 22 is attached to the movable part of the objective lens actuator 20, but the reflection part 21 needs to be provided closer to the mirror 23 than the quarter wavelength plate 22. . This is because the reflected light needs to be P-polarized light. The light transmitted through the quarter-wave plate 22 changes from linearly polarized light (here P-polarized light) to circularly polarized light and enters the objective lens 1, but the light reflected by the optical disc 100 passes through the quarter-wave plate 22. Then, the circularly polarized light is changed to the linearly polarized light again.

このとき、１／４波長板２２を透過した光ディスク１００からの反射光は、往路とは偏光方向が９０度回転した直線偏光となるため、この例のように、往路がＰ偏光の場合、光ディスク１００からの反射光は１／４波長板２２を透過することでＳ偏光となる。従って、１／４波長板２２を透過した光ディスク１００からの反射光は、ミラー２３を透過せず、ミラー２３で全反射して検出光学系へ向かうことになる。 At this time, since the reflected light from the optical disc 100 that has passed through the quarter-wave plate 22 is linearly polarized light whose polarization direction is rotated by 90 degrees from the forward path, as in this example, when the forward path is P-polarized light, the optical disk The reflected light from 100 passes through the quarter-wave plate 22 and becomes S-polarized light. Therefore, the reflected light from the optical disc 100 that has passed through the quarter-wave plate 22 does not pass through the mirror 23 but is totally reflected by the mirror 23 and travels toward the detection optical system.

ミラー２３で全反射した、１／４波長板２２を透過した光ディスク１００からの反射光は、図６（Ｂ）に示すビームエキスパンダ２５を透過し、偏光ビームスプリッタ１０で反射して光路が変えられた後、集光レンズ７で集光され、更に検出レンズ８を透過して光検出器２６へと導かれ、ここで光電変換され、得られた電気信号に基づいて公知の方法で読み取り信号が得られると共にサーボ信号が生成される。 The reflected light from the optical disk 100 totally reflected by the mirror 23 and transmitted through the quarter-wave plate 22 is transmitted through the beam expander 25 shown in FIG. 6B and reflected by the polarizing beam splitter 10 to change the optical path. Then, the light is condensed by the condensing lens 7, further transmitted through the detection lens 8 and guided to the photodetector 26, where it is photoelectrically converted, and a read signal is read out by a known method based on the obtained electric signal. And a servo signal is generated.

一方、対物レンズアクチュエータ２０の可動部に設けられた反射部２１で反射した光は、半導体レーザ６からミラー２３に入射する光束の９５％の外周部分の光で、さらにミラー２３を透過率５％で透過するので、半導体レーザ６からミラー２３に入射する光束の４.７５％の光が第二の光検出器２４ｂに入射する。 On the other hand, the light reflected by the reflecting portion 21 provided at the movable portion of the objective lens actuator 20 is light from the outer peripheral portion of 95% of the light beam incident on the mirror 23 from the semiconductor laser 6 and further passes through the mirror 23 with a transmittance of 5%. Therefore, 4.75% of the light beam incident on the mirror 23 from the semiconductor laser 6 enters the second photodetector 24b.

ここで、第二の光検出器２４ｂに入射する光は、対物レンズ１の有効径に相当する部分以外の光に相当するので、第一の光検出器２４ａに入射した光から、第二の光検出器２４ｂに入射した光を差し引くことで、実際に対物レンズ１に入射する光量を計算することができる。ただし、第二の光検出器２４ｂに入射する光量は、前記のとおり、第一の光検出器２４ａに入射する光量が５％なのに対して、４.７５％相当になるので、係数をかけて、演算する必要がある。また、この係数は、反射部２１の反射率に応じて適切な値とする。 Here, since the light incident on the second photodetector 24b corresponds to light other than the portion corresponding to the effective diameter of the objective lens 1, the second incident light is incident on the second photodetector 24a. By subtracting the light incident on the photodetector 24b, the amount of light actually incident on the objective lens 1 can be calculated. However, as described above, the amount of light incident on the second photodetector 24b is equivalent to 4.75% while the amount of light incident on the first photodetector 24a is 5%. , It is necessary to calculate. This coefficient is set to an appropriate value according to the reflectance of the reflecting portion 21.

第一の光検出器２４ａにより光電変換されて得られた第一の光検出信号から、第二の光検出器２４ｂにより光電変換されて得られた第二の光検出信号に適切な値の係数をかけて差し引く演算を行うことにより、実際に対物レンズ１に入射する光量を示す信号が得られるので、この光量を示す信号に基づいて半導体レーザ６の駆動電流を、図示しない駆動制御回路により実際に対物レンズ１に入射する光量が一定になるように制御する。これにより、半導体レーザ６から出射される光出力パワーは、実際に対物レンズ１に入射する光量が一定になるように可変制御される。 A coefficient having an appropriate value from the first light detection signal obtained by photoelectric conversion by the first light detector 24a to the second light detection signal obtained by photoelectric conversion by the second light detector 24b. Since the signal indicating the amount of light actually incident on the objective lens 1 is obtained by performing the subtraction operation, the drive current of the semiconductor laser 6 is actually measured by a drive control circuit (not shown) based on the signal indicating the amount of light. The amount of light incident on the objective lens 1 is controlled to be constant. Thereby, the optical output power emitted from the semiconductor laser 6 is variably controlled so that the amount of light actually incident on the objective lens 1 is constant.

このように、本実施の形態では、トラッキングによる対物レンズ１の移動や、光学系による対物レンズ１へ入射する光束の変化に対応して、対物レンズ１に入射する光量が一定になるように半導体レーザ６の光出力を細かく可変制御することができる。 As described above, in the present embodiment, the semiconductor is configured so that the amount of light incident on the objective lens 1 is constant in accordance with the movement of the objective lens 1 due to tracking and the change in the luminous flux incident on the objective lens 1 due to the optical system. The light output of the laser 6 can be finely variably controlled.

なお、上記の実施の形態では、反射部２１は、対物レンズアクチュエータ２０の可動部に直接形成するように説明したが、図８に示すように、１／４波長板２９のミラー２３側の入射面の一部に形成してもよい。また、１／４波長板２９とは別に中央部を透過、外周部を反射する部材を１／４波長板２２のミラー２３側入射面に取り付けてもよい。 In the above-described embodiment, it has been described that the reflecting portion 21 is formed directly on the movable portion of the objective lens actuator 20, but as shown in FIG. 8, the incident on the mirror 23 side of the quarter-wave plate 29. You may form in a part of surface. In addition to the quarter-wave plate 29, a member that transmits the central portion and reflects the outer peripheral portion may be attached to the incident surface of the quarter-wave plate 22 on the mirror 23 side.

また、半導体レーザ６から出射される直線偏光はＰ偏光であるものとして説明したが、Ｓ偏光であってもよい。ただし、この場合は、ミラー２３の特性を入射するＰ偏光を全反射し、入射するＳ偏光は一部分のみ透過し、残りは反射する特性とする必要がある。 Further, the linearly polarized light emitted from the semiconductor laser 6 has been described as being P-polarized light, but may be S-polarized light. In this case, however, it is necessary that the characteristics of the mirror 23 are such that the incident P-polarized light is totally reflected, and the incident S-polarized light is partially transmitted and the rest is reflected.

本発明の光ピックアップの第１の実施の形態の構成図である。1 is a configuration diagram of a first embodiment of an optical pickup according to the present invention. FIG. 図１の光ピックアップの要部の構成の説明図である。It is explanatory drawing of a structure of the principal part of the optical pick-up of FIG. 図１の光ピックアップの１／４波長板に施される膜の説明図である。It is explanatory drawing of the film | membrane applied to the quarter wavelength plate of the optical pick-up of FIG. 図１の光ピックアップの光検出器の構成の一例を示す図である。It is a figure which shows an example of a structure of the photodetector of the optical pick-up of FIG. 図１の光ピックアップの光検出器の構成の他の例を示す図である。It is a figure which shows the other example of a structure of the photodetector of the optical pick-up of FIG. 本発明の光ピックアップの第２の実施の形態の構成図である。It is a block diagram of 2nd Embodiment of the optical pick-up of this invention. 図６の光ピックアップ内の光検出器とその光スポットを示す図である。It is a figure which shows the photodetector in the optical pick-up of FIG. 6, and its light spot. 図６の光ピックアップ内の反射膜の取り付け位置の他の例を示す図である。It is a figure which shows the other example of the attachment position of the reflecting film in the optical pick-up of FIG. 従来の光ピックアップの一例の構成図である。It is a block diagram of an example of the conventional optical pickup.

Explanation of symbols

１対物レンズ
２、２０対物レンズアクチュエータ
３、２２、２９１／４波長板
４、２３ミラー
５コリメータレンズ
６半導体レーザ
７集光レンズ
８検出レンズ
９、２６光検出器
９ａ４分割光検出部
９ｂ、９ｃ、９ｄ２分割光検出部
９ｅ非分割光検出部
１０偏光ビームスプリッタ
１１回折格子
１５反射防止膜
１６全反射膜
１７差動アンプ
１８加算器
２１反射部
２３ミラー
２４ａ第一の光検出器
２４ｂ第二の光検出器
２５ビームエキスパンダ

DESCRIPTION OF SYMBOLS 1 Objective lens 2, 20 Objective lens actuator 3, 22, 29 1/4 wavelength plate 4, 23 Mirror 5 Collimator lens 6 Semiconductor laser 7 Condensing lens 8 Detection lens 9, 26 Photo detector 9a 4 division | segmentation light detection part 9b, 9c, 9d 2 split light detector 9e Non-split light detector 10 Polarizing beam splitter 11 Diffraction grating 15 Antireflection film 16 Total reflection film 17 Differential amplifier 18 Adder 21 Reflector 23 Mirror 24a First photodetector 24b First light detector 24b Nino Photo Detector 25 Beam Expander

Claims

The information signal is recorded by making the light emitted from the light source incident on the objective lens and condensed on the optical disk, or the reflected light from the optical disk is incident on the detection optical system through the objective lens to reproduce the recorded information signal. In the optical pickup that
Of the objective lens actuator together with the objective lens so that the incident surface is inclined with respect to the side opposite to the optical disc side of the objective lens on the optical axis and inclined with respect to the reference plane of the objective lens. A 1/4 wavelength plate is mounted on the movable part, and the 1/4 wavelength plate functions as a 1/4 wavelength plate by transmitting light to the central portion of the incident surface corresponding to the effective diameter of the objective lens. And the region other than the central portion of the incident surface is configured to reflect light,
The photodetector in the detection optical system includes a first photodetector that receives the first reflected light reflected by the optical disc and transmitted through the central portion of the quarter-wave plate, and the 1 / A second light detection unit that receives the second reflected light reflected by the region other than the central portion of the four-wavelength plate, and outputs light from the light source according to the amount of the second reflected light. An optical pickup characterized by controlling.

The second light detection unit includes a two-divided light receiving unit that is divided into two in the track direction of the optical disc, and calculates a difference between the two received light signals respectively received by the two divided light receiving units. First calculating means for detecting movement of the objective lens in the tracking direction, and second calculating means for calculating a sum of the two light receiving signals and generating a signal for controlling the light output emitted from the light source. The optical pickup according to claim 1, further comprising:

The information signal is recorded by making the light emitted from the light source incident on the objective lens and condensed on the optical disk, or the reflected light from the optical disk is incident on the detection optical system through the objective lens to reproduce the recorded information signal. In the optical pickup that
A quarter-wave plate is provided at a position on the optical axis opposite to the side opposite to the optical disk side of the objective lens, and the quarter-wave plate having a size corresponding to the effective diameter of the objective lens In the central part, light is transmitted and functions as a quarter-wave plate, and the area other than the central part of the incident surface of the quarter-wave plate is configured to reflect light,
The detection optical system includes a mirror having a characteristic of reflecting most of the light amount and transmitting a part of the light amount when at least the polarization direction of incident light is the same as the linearly polarized light emitted from the light source, and the mirror A first photodetector that receives linearly polarized light that is emitted from the light source that has passed through and directed toward the objective lens, and a second that is reflected by a region other than the central portion of the quarter-wave plate and is transmitted through the mirror. And a second photodetector for receiving the reflected light, wherein the first photodetector monitors the entire light beam directed to the objective lens, and the second photodetector comprises the objective lens. Monitoring the light corresponding to the portion not incident on the effective diameter of the light source, and controlling the light output emitted from the light source based on the signals obtained by calculating the output signals of the first and second photodetectors. Features an optical pickup.