JP4366813B2 - Optical pickup device and coupling lens for optical pickup device - Google Patents

Description

【００５１】
回折面は、形状が光軸に対して回転対称な多項式によって表されるものと、光軸と垂直で互いに直交する２つの軸（Ｘ，Ｙ）の多項式によって表されるものがある。
【００５２】
光軸に対して回転対称な多項式で表される回折面は、光路差関数として［数２］により、又、光軸と垂直な軸（Ｘ，Ｙ）の多項式で表される回折面は光路差関数として［数３］により、単位をｍｍとして表わされている。但しＸ，Ｙ，Ｚは右手系の直交座標系、光路差関数の設計波長は７８０ｎｍである。図１に、かかる座標系を示す。
【００５３】
【数２】

【００５４】
【数３】

【００５５】
（実施例１）
［表１］に、実施例１における、対物レンズとカップリングレンズ光学系からなる光ピックアップ装置用の集光光学系に関するデータを示す。尚、これより示すレンズデータ内において、１０のべき乗数（例えば、２．５×１０−３）を、Ｅ（例えば、２．５×Ｅ−３）を用いて表している。また、回転対称な多項式によって表される回折パターンの回折による１次光は、回折後収束する方向に光線の角度が変化する光のことを意味する。
【００５６】
【表１】

【００５７】
対物レンズは、コリメータ側の面が同心円状に分割された複数の輪帯面（第１，２，３輪帯）からなり、各輪帯はその球面収差を利用して波長の異なる複数の光源、および厚みの異なる透明基板に対して、第１，３輪帯が短い波長，薄い基板に対して回折限界内に収差補正されており、第２輪帯が長い波長において厚い基板に対して回折限界内に収差補正された特殊対物レンズである。第２輪帯のｄ’は、第２輪帯の形状を非球面形状式に従って光軸まで延長したときの光軸との交点と、対物レンズの透明基板側の面との光軸上の間隔を示している。この対物レンズは光源側の面から平行光が入射した場合に性能が良好に保たれるように設計されている。
【００５８】
カップリングレンズとして、オレフィン系樹脂からなるＨＯＥコリメータを用いた。コリメータの対物レンズ側の面には、光軸と略同心円状に鋸刃状の回折パターンが設けられている。かかる素材の屈折率を、［表２］に示す。
【００５９】
【表２】

【００６０】
図２は、実施例１のコリメータ単体の色収差を示すグラフである。図２によれば、波長にかかわらずバックフォーカスが移動していないことがわかる。異なる波長の２光源が１パッケージ化されたユニット（例えば２レーザ１パッケージ）を用いた光ピックアップ装置等の場合、波長が異なる光源の光軸方向の位置が同じ場合に、軸上色収差のあるコリメータを用いると、少なくとも１つの光源からの光はコリメータ出射後に平行光とならず、光ピックアップ光学系全体の性能が悪化するが、本実施例のコリメータを用いると、２つの異なる波長の両方共にコリメータから平行光が出射し、光ピックアップ光学系全体の性能が良好に保たれる。
（実施例２）
ビ―ムスプリッタ等の光学素子を用いずに複数の波長の光源を利用する場合、少なくとも１つの光源は光軸から離れた位置に設置せざるをえない。従来のコリメータを用いた場合、軸外から出射した光線はコリメータ出射後、光軸に対して傾きを持った光線となり、対物レンズ及び透明基板を通過するとコマ収差を発生し、集光光学系全体の性能を悪化させる。［表３］に実施例２のコリメータに関するデータを示す。コリメータの光源側の面に回折格子を有している。本実施例のコリメータを、波長６５０ｎｍの光源が光軸上に設置され、波長７８０ｎｍの光源が光軸から０．１ｍｍの距離に設置されるような光ピックアップ光学系にて用いると、波長６５０ｎｍの光源からの光に対しては０次光、波長７８０ｎｍの光源に対しては１次光を利用することにより、どちらの光源からの光もコリメータ出射後は光軸に対して平行な光ヘと変換される。
【００６１】
【表３】

【００６２】
（実施例３）
［表４］に実施例３のコリメータに関するデータを示す。コリメータの光源側の面に（Ｘ，Ｙ）の多項式で表される回折パターンを有している。実施例２のコリメータと同様、光軸上の波長６５０ｎｍの光源に対して０次光を、光軸から０．１ｍｍ離れた位置にある波長７８０ｎｍの光源に対して１次光を利用することにより、どちらの光源からの光も、光軸に対して平行な光として出射することが可能である。コリメータの光源と反対側の面から波長７８０ｎｍの平行光を、直径５ｍｍの開口を通して入射し、波面収差を計算すると、実施例２の回折格子を有したコリメータでは標準偏差値で０．０１０λのコマ収差が発生するが、実施例３のコリメータでは回折格子の代わりに（Ｘ，Ｙ）の多項式で表される回折パターンを用いることで、０．０００λに補正されている。
【００６３】
【表４】

【００６４】
（実施例４）
［表５］に実施例４のコリメータに関するデータを示す。コリメータの光源側の面に（Ｘ、Ｙ）の多項式で表される回折パターンを有しており、反対側の面には光軸に対して回転対称な多項式によって表される回折パターンを有している。光源と反対側の面に設けられた回折パターンによる１次回折光を利用することにより、波長６５０ｎｍの光源と波長７８０ｎｍの光源の光軸方向の位置が同じ場合でも、コリメータ出射後に光軸に対して平行な光が得られる。光源側の面に設けられた回折パターンによる１次回折光は、光軸から０．１ｍｍ離れた位置に設置された波長７８０ｎｍの光源からの光束の主光線を光軸に平行な光線に変換する機能を有する。よって、本実施例のコリメータを、波長６５０ｎｍの光源と波長７８０ｎｍの光源が０．１ｍｍの間隔で並列に設置された、２レーザが１パッケージとなった光源ユニットとともに、光ピックアップ光学系にて用いることにより、どちらの光源からの光もコリメータ出射後に光軸に対して平行な光へと変換される。
【００６５】
【表５】

【００６６】
（実施例５）
［表６］に実施例５の光ピックアップ光学系に関するデータを示す。従来のコリメータを用いた場合、軸外の光源から出射した光線はコリメータ出射後、光軸に対して傾きを持った光線となり、対物レンズ及び透明基板を通過するとコマ収差を発生し、集光光学系全体の性能を悪化させる。本実施例のコリメータでは、軸外光源を用いた時に対物レンズ及び透明基板にて発生するコマ収差を補正するような軸外特性をコリメータに持たせてある。波長７８０ｎｍの光源が光軸から０．１ｍｍ離れた位置に設置されているような光ピックアップ光学系にて、透明基板側のＮＡが０．４５になるような開ロ制限を設けて、光学系全体の波面収差を計算すると、コマ収差は標準偏差値で０．００１λ以下に補正されている。
【００６７】
【表６】

【００６８】
尚、コリメータは、一面にのみ回折パターンを有し、回折パターンの回折効果によって、色収差補正がなされ、かつ／又は前記集光光学系の光軸に対して斜方から入射した光束の主光線を光軸とほぼ平行な方向に出射させるようになっていても良く、或いは、コリメータの両面に回折パターンを有し、前記両面の回折パターンの回折効果によって、色収差補正がなされ、かつ／又は前記集光光学系の光軸に対して斜方から入射した光束の主光線を光軸とほぼ平行な方向に出射させるようになっていても良く、更には、コリメータの両面に回折パターンを有し、一方の面における回折パターンの回折効果によって、色収差補正がなされ、かつ他方の面における回折パターンの回折効果によって，前記集光光学系の光軸に対して斜方から入射した光束の主光線を光軸とほぼ平行な方向に入射させるようになっていても良い。
【００６９】
図３は、本実施の形態の光ピックアップ装置を示す概略図である。図３に示す光ピックアップ装置１００においては、２レーザ１パッケージである第１半導体レーザ１１１と第２半導体レーザ１１２とが並列に固定されてユニット化されている。コリメータ１３０は、上記実施例１〜５を用いることが出来る。
【００７０】
第１の光ディスク（例えばＤＶＤ）を再生する場合、集光光学系を構成するコリメータ（カップリングレンズ）１３０と対物レンズ１６０の光軸上に配置された光源としての第１半導体レーザ１１１から出射された光束（波長６３５又は６５０ｎｍ）は、ビームスプリッタ２３０及びコリメータ１３０を透過し平行光束となる。さらに絞り１７０によって絞られ、対物レンズ１６０により第１の光ディスク２００の透明基板２１０を介して情報記録面２２０に集光される。
【００７１】
そして、情報記録面２２０で情報ピットにより変調されて反射した光束は、再び対物レンズ１６０、絞り１７０を介して、コリメータ１３０を透過し、ビームスプリッタ２３０で反射されて、センサレンズ３１０を介して光検出器３００上へ入射し、その出力信号を用いて、第１光ディスク２００に記録された情報の読み取り信号が得られる。
【００７２】
また、光検出器３００上でのスポットの形状変化、位置変化による光量変化を検出して、合焦検出やトラック検出を行い、２次元アクチュエータ１５０により、合焦、トラッキングのために対物レンズ１６０を移動させることができる。
【００７３】
２レーザ１パッケージである第１半導体レーザ１１１と第２半導体レーザ１１２とが並列に固定されてユニット化されており、２つの光源が別々に集光光学系の光軸に沿った方向に移動できないように位置が固定されている場合であっても、色収差補正を行うことが出来る。
【００７４】
第２の光ディスク（例えばＣＤ）を再生する場合、集光光学系の軸外に配置された光源としての第２半導体レーザ１１２から出射された光束（波長７８０ｎｍ）は、コリメータ１３０の光軸と略同軸になるように斜めに入射し、更にコリメータ１３０を透過してほぼ平行光束となる。さらに絞り１７０、対物レンズ１６０を介して第２の光ディスク２００の透明基板２１０を介して情報記録面２２０’に集光される。
【００７５】
そして、情報記録面２２０’で情報ピットにより変調されて反射した光束は、再び対物レンズ１６０、絞り１７０を介して、コリメータ１３０を透過し、ビームスプリッタ２３０で反射されて光検出器３００上へ入射し、その出力信号を用いて、第２の光ディスク２００に記録された情報の読み取り信号が得られる。
【００７６】
また、光検出器３００上でのスポットの形状変化、位置変化による光量変化を検出して、合焦検出やトラック検出を行い、この検出に基づいて２次元アクチュエータ１５０により、合焦、トラッキングのために対物レンズ１６０を移動させることが出来る。
【００７７】
本実施の形態の如く、情報記録のためにより精度良く収斂させるべきＤＶＤ用のレーザ光は、第１の半導体レーザ１１１を、集光光学系の光軸上に配置することによって、その光軸に沿った方向に照射させて、集光光学系の最良の光学特性を発揮できるようにし、一方、情報記録のためにＤＶＤほど精度良く収斂させる必要のないＣＤ用のレーザ光は、第２の半導体レーザ１１２から、コリメータ１３０の光軸に対し斜めに入射させて、その後平行光に変換するようにしている。尚、第２の半導体レーザ１１２からのレーザ光を、コリメータ１３０の軸外から光軸に対して斜めに入射させた場合、対物レンズ１６０を通過する際に生じるコマ収差をうち消すように、コリメータ１３０を通過した第２の半導体レーザ１１２からのレーザ光にコマ収差を生じさせれば、集光光学系全体で、コマ収差を良好に補正できる。
【００７８】
【発明の効果】
本発明によると、例えば２レーザ１パッケージのごときレーザ光源ユニットを用いた場合でも、良好に情報記録／再生が可能な光ピックアップ装置用のカップリングレンズ及び光ピックアップ装置を提供することができる。
【図面の簡単な説明】
【図１】 コリメータの回折面の光路差関数にかかる座標系を示す図である。
【図２】 実施例１のコリメータ単体の色収差を示すグラフである。
【図３】 本実施の形態の光ピックアップ装置を示す概略図である。
【符号の説明】
１００ 光ピックアップ装置
１１１ 第１の半導体レーザ
１１２ 第２の半導体レーザ
１３０ コリメータ
１６０ 対物レンズ
１７０ 絞り
２００ 第１の光ディスク又は第２の光ディスク
３００ 光検出器[0001]
BACKGROUND OF THE INVENTION
  The present invention relates to a coupling lens for an optical pickup device including a light source of a two-laser one package in which two lasers are unitized, and an optical pickup device, for example.
[0002]
[Prior art]
  In recent years, along with the practical application of short-wavelength red semiconductor lasers, development of DVDs (digital versatile discs), which are high-density optical discs with the same size and capacity as conventional optical discs (compact discs), has progressed. It is out. In an optical system of an optical information recording / reproducing apparatus using such an optical disc as an optical information recording medium, in order to increase the recording signal density, the spot focused by the objective lens on the recording medium must be reduced. Is required. For this reason, there is an actual situation that the wavelength of the laser as the light source is shortened and the NA of the objective lens is increased.
[0003]
  For example, in an optical pickup device that records and / or reproduces information with respect to a DVD, when a short wavelength semiconductor laser of 635 nm is used as a light source, the numerical aperture NA on the optical disc side of the objective lens that collects the laser light is collected. Is about 0.6. In addition to CDs and DVDs, optical discs of various standards, such as CD-R (write-once compact disc), MD (mini disc), etc., are commercialized and popularized.
[0004]
  On the other hand, in an optical pickup device that records and / or reproduces information with respect to a CD-R, the wavelength of the light source needs to be λ = 780 nm, but in other optical discs, a wavelength other than a specific light source wavelength is required. A light source can be used, and in such a case, the required numerical aperture NA changes according to the light source wavelength λ to be used. For example, the required numerical aperture NA = λ (μm) /1.73 for a CD, and the required numerical aperture NA = λ (μm) /1.06 for a DVD. The numerical aperture (required numerical aperture) referred to in this specification is the numerical aperture of the condensing optical system viewed from the optical disc side, and the required numerical aperture is the spot size d required on the recording surface of the optical disc and the use. The numerical aperture calculated from the wavelength λ, generally NA = 0.83 × λ ÷ d.
[0005]
[Problems to be solved by the invention]
  As described above, there are various optical disks with different transparent substrate thicknesses, recording densities, operating wavelengths, etc. in the market. Dedicated information recording capable of recording and / or reproducing information on individual optical disks. Purchasing a playback device is a heavy burden on the user. Therefore, an information recording / reproducing apparatus including a compatible optical pickup device that can be used for various optical disks has been proposed.
[0006]
  As such an optical pickup device, there has been proposed an optical pickup device that includes a condensing optical system corresponding to each of different optical disks, and switches the condensing optical system depending on the optical disk to be reproduced. However, this optical pickup device requires a plurality of condensing optical systems, which complicates the configuration and is not preferable because of high costs. Therefore, an optical pickup device that reproduces a plurality of optical discs using one condensing optical system has been proposed.
[0007]
  By the way, as described above, a laser light source having a wavelength of 780 nm is normally used for recording / reproducing information with respect to a CD, while a 635-nm wavelength is usually used for recording / reproducing information with respect to a DVD. It is necessary to use a laser light source having a wavelength. Here, since a single laser light source for irradiating laser beams of different wavelengths has not been put into practical use, it is necessary to provide two laser light sources of different wavelengths in the optical pickup device described above.
[0008]
  When irradiating each laser beam onto an optical disc from two laser light sources via a single condensing optical system, as one aspect, two laser light sources arranged at different positions by using a beam splitter. Can be irradiated onto the optical disc along the optical axis of the condensing optical system. However, in this aspect, there is a problem that it is necessary to insert a beam splitter into the optical path, thereby increasing the size of the optical pickup device.
[0009]
  On the other hand, if the two lasers are arranged in parallel, there is no need to provide a beam splitter, and the optical pickup device can be simplified and reduced in cost. However, when one of the laser light beams from the parallel laser light sources is irradiated along the optical axis of the condensing optical system, the other passes through the optical axis of the condensing optical system or is collected. Incidently with respect to the optical axis of the optical optical system. When laser light is incident on the condensing optical system in such an abnormal manner, problems such as deterioration of aberration occur. However, if each laser light source is independent, it can be moved separately, so that the position can be optimized and finely adjusted so that the aberration performance is good for each laser light source.
[0010]
  On the other hand, a so-called two-laser one-package laser light source in which two laser light sources arranged in parallel are packaged has been developed. If such a laser light source unit is used, the optical pickup device can be further simplified and reduced in cost.
[0011]
  However, since the distance between the individual laser light sources is fixed in the laser light source unit in which two lasers are packaged, the laser light source unit is positioned separately in the direction along the optical axis in addition to the direction perpendicular to the optical axis. There is a problem that it becomes impossible to adjust.
[0012]
  An object of the present invention is to provide a coupling lens for an optical pickup device and an optical pickup device that can record / reproduce information satisfactorily even when a laser light source unit such as two lasers and one package is used.
[0013]
[Means for Solving the Problems]
  The optical pickup device according to claim 1 is a coupling lens that converts a divergence state of a light beam from a first light source having a wavelength λ1 and a second light source having a wavelength λ2, and a light beam converted from the divergence state. A condensing optical system including an objective lens for condensing on the recording surface of the information recording medium, and a detector for detecting reflected light and / or transmitted light from the recording surface, and having a transparent substrate thickness In the optical pickup device for information recording / reproduction capable of recording and / or reproducing information with respect to the first and second optical information recording media having different lengths, the first light source and the second light source are units. And the coupling lens includes a light beam from the light source having the wavelength λ1 and a light beam from the light source having the wavelength λ2.Have the same back focusThe diffraction pattern is formed on at least one surface.
[0014]
  Since the coupling lens has a diffraction pattern for correcting chromatic aberration of the light beam from the light source having the wavelength λ1 and the light beam from the light source having the wavelength λ2 on at least one surface, the first light source and the first light source Even when the two light sources are unitized and the positions of the two light sources are fixed so that they cannot move separately in the direction along the optical axis of the condensing optical system, due to the diffraction effect of the diffraction pattern,The light beam from the light source having the wavelength λ1 and the light beam from the light source having the wavelength λ2 can have the same back focus,Thereby, it is possible to record / reproduce good information. The unitization means that the first light source and the second light source are fixedly housed in one package, for example. However, the present invention is not limited to this, and the two light sources cannot be corrected for aberrations. Widely includes the state fixed to.
[0015]
  Various light sources such as a blue laser light source and a red laser light source can be considered as the first wavelength light source and the second wavelength light source of the present invention. In addition, when there are three light sources having different wavelengths, it is sufficient that two of the light sources have the above-described relationship. In addition to a single lens, for example, a two-lens that combines a normal lens and a plate member having a diffraction pattern having almost no power, a cemented lens, and a hybrid lens can be considered as the coupling lens. Glass is also considered as a material for the coupling lens, but a resin is preferable for forming a diffraction pattern. The condensing optical system includes not only a lens but also a mirror.
[0016]
  The optical pickup device according to claim 2 is a coupling lens that converts a divergence state of a light beam from a first light source having a wavelength λ1 and a second light source having a wavelength λ2, and a light beam converted from the divergence state. A condensing optical system including an objective lens for condensing on the recording surface of the information recording medium, and a detector for detecting reflected light and / or transmitted light from the recording surface, and having a transparent substrate thickness In an optical pickup device for recording / reproducing information capable of recording and / or reproducing information with respect to first and second optical information recording media having different lengthsThe first light source and the second light source are unitized, and the coupling lens has a diffraction pattern consisting of at least one surface, and a light beam from the light source having the wavelength λ1 and a light beam from the light source having the wavelength λ2 On the other hand, it has the same back focus, and has a diffraction pattern that emits a principal ray of a light beam incident obliquely with respect to the optical axis of the condensing optical system in a direction substantially parallel to the optical axis. And In the present specification, the optical axis of the condensing optical system means an axis passing through the center of the coupling lens. This is because when the condensing optical system has a mirror or the like, the angle of the optical axis changes according to the reflection angle. The chief ray means a ray at the center of the light beam limited by an aperture such as a diaphragm.
[0017]
  Since the coupling lens has a diffraction pattern for correcting chromatic aberration of the light beam from the light source having the wavelength λ1 and the light beam from the light source having the wavelength λ2 on at least one surface, the first light source and the second light source Even when the position is fixed so that the two light sources cannot move separately in the direction along the optical axis of the condensing optical system, due to the diffraction effect of the diffraction pattern, The light beam from the light source having the wavelength λ1 and the light beam from the light source having the wavelength λ2 can have the same back focus, thereby enabling good information recording / reproduction. In addition, among the light beams emitted from the first light source or the second light source, the coupling lens uses the principal ray of the light beam incident obliquely with respect to the optical axis of the condensing optical system as an optical axis. Since the light is emitted in a substantially parallel direction, even if one of the light sources is arranged at a position that does not irradiate the light beam in the direction along the optical axis of the condensing optical system, the light source is as if Since the light beam can be irradiated in the optical axis direction so as to be on the optical axis of the condensing optical system, better information recording / reproduction can be performed.
[0018]
  The optical pickup device according to a third aspect is characterized in that the coupling lens is a single lens.
[0019]
  The optical pickup device according to claim 4, wherein the coupling lens has a diffraction pattern only on one surface, and is incident obliquely with respect to the optical axis of the condensing optical system due to a diffraction effect of the diffraction pattern. The principal ray of the luminous flux is emitted in a direction substantially parallel to the optical axis.
[0020]
  The optical pickup device according to claim 5, wherein the coupling lens has a diffraction pattern on both surfaces, and the light beam from the light source having the wavelength λ1 and the light source having the wavelength λ2 are generated by the diffraction effect of the diffraction patterns on the both surfaces. The principal ray of the light beam incident obliquely with respect to the optical axis of the condensing optical system is emitted in a direction substantially parallel to the optical axis. It is characterized by being.
[0021]
  The optical pickup device according to claim 6, wherein the coupling lens has a diffraction pattern on both surfaces, and a light beam from the light source having the wavelength λ1 and a light source having the wavelength λ2 by a diffraction effect of the diffraction pattern on one surface. The principal ray of the light beam incident obliquely with respect to the optical axis of the condensing optical system can be obtained by the diffraction effect of the diffraction pattern on the other surface. It is characterized in that the light is emitted in a direction substantially parallel to.
[0022]
  The optical pickup device according to claim 7 is a coupling lens that converts a divergence state of a light beam from a first light source having a wavelength λ1 and a second light source having a wavelength λ2, and a light beam converted from the divergence state. A condensing optical system including an objective lens for condensing on the recording surface of the information recording medium, and a detector for detecting reflected light and / or transmitted light from the recording surface, and having a transparent substrate thickness In an optical pickup device for recording / reproducing information capable of recording and / or reproducing information with respect to first and second optical information recording media having different lengths, the first light source and the second light source are units. The coupling lens forms a diffraction pattern having the same back focus with respect to the light beam from the light source having the wavelength λ1 and the light beam from the light source having the wavelength λ2 on at least one surface. The lens is configured to reduce off-axis coma aberration in the condensing optical system of light beams incident from an oblique direction with respect to the optical axis of the condensing optical system among the light beams emitted from the first light source or the second light source. It has an off-axis characteristic to be corrected.
[0023]
  Since the coupling lens has at least one diffraction pattern having the same back focus with respect to the light beam from the light source having the wavelength λ1 and the light beam from the light source having the wavelength λ2, Even when the second light source is unitized and the positions of the two light sources are fixed so that they cannot move separately in the direction along the optical axis of the condensing optical system, the diffraction effect of the diffraction pattern Therefore, the light beam from the light source having the wavelength λ1 and the light beam from the light source having the wavelength λ2 can have the same back focus, thereby enabling good information recording / reproduction. In addition, among the light beams emitted from the first light source or the second light source, the coupling lens uses the principal ray of the light beam incident obliquely with respect to the optical axis of the condensing optical system as an optical axis. Since the light is emitted in a substantially parallel direction, even if one of the light sources is arranged at a position that does not irradiate the light beam in the direction along the optical axis of the condensing optical system, the light source is as if Since the light beam can be irradiated in the optical axis direction so as to be on the optical axis of the condensing optical system, better information recording / reproduction can be performed. Further, since the predetermined coma aberration occurs in the off-axis light that generates a certain image height by passing through the objective lens and the transparent substrate, the reverse coma aberration is eliminated so that the coma aberration is eliminated by the coupling lens. Can effectively reduce the coma aberration in the entire condensing optical system with respect to the light beam incident obliquely with respect to the optical axis of the condensing optical system, thereby improving the information recording / Playback is possible.
[0024]
  The optical pickup device according to claim 8, wherein the wavelength λ1 and the wavelength λ2 have a relationship of λ1 <λ2, the thickness of the transparent substrate of the first optical information recording medium is t1, and the second When the thickness of the transparent substrate of the optical information recording medium is t2, the relationship of t1 <t2 is established. Therefore, for example, recording / reproducing information on different recording media such as CD and DVD Can be performed.
[0025]
  The optical pickup device according to claim 9 is characterized in that the light beam emitted from the second light source is incident obliquely with respect to the optical axis of the condensing optical system.
[0026]
  An optical pickup device according to a tenth aspect is a collimator that changes a divergent light beam incident on the coupling lens into a substantially parallel light beam with respect to an optical axis.
[0027]
  The coupling lens for an optical pickup device according to claim 11 is a coupling lens that converts a divergence state of a light beam from a first light source having a wavelength λ1 and a second light source having a wavelength λ2, and the divergence state is converted. A condensing optical system including an objective lens for condensing the collected light beam on the recording surface of the optical information recording medium, and a detector for detecting reflected light and / or transmitted light from the recording surface In the coupling lens for an optical pickup device for recording / reproducing information capable of recording and / or reproducing information with respect to the first and second optical information recording media having different transparent substrate thicknesses, the first The light source and the second light source are unitized, and the coupling lens has a diffraction pattern having the same back focus with respect to the light beam from the light source having the wavelength λ1 and the light beam from the light source having the wavelength λ2. The coupling lens is formed of at least one surface of the light beam emitted from the first light source or the second light source, the light beam incident obliquely with respect to the optical axis of the condensing optical system. The principal ray is emitted in a direction substantially parallel to the optical axis.
[0028]
  Since the coupling lens has a diffraction pattern having the same back focus with respect to the light beam from the light source having the wavelength λ1 and the light beam from the light source having the wavelength λ2 on at least one surface, Even when the second light source is unitized and the two light sources are separately positioned so that they cannot move in the direction along the optical axis of the condensing optical system, diffraction of the diffraction pattern Due to the effect, the light beam from the light source having the wavelength λ1 and the light beam from the light source having the wavelength λ2 can have the same back focus, thereby enabling good information recording / reproduction. In addition, among the light beams emitted from the first light source or the second light source, the coupling lens uses the principal ray of the light beam incident obliquely with respect to the optical axis of the condensing optical system as an optical axis. Since the light is emitted in a substantially parallel direction, even if one of the light sources is arranged at a position that does not irradiate the light beam in the direction along the optical axis of the condensing optical system, the light source is as if Since the light beam can be irradiated in the optical axis direction so as to be on the optical axis of the condensing optical system, better information recording / reproduction can be performed.
[0029]
  The coupling lens according to claim 12 is a single lens.
[0030]
  The coupling lens for an optical pickup device according to claim 13, wherein the coupling lens has a diffraction pattern only on one surface, and further with respect to the optical axis of the condensing optical system due to a diffraction effect of the diffraction pattern. A principal ray of a light beam incident from an oblique direction is emitted in a direction substantially parallel to the optical axis.
[0031]
  The coupling lens for an optical pickup device according to claim 14, wherein the coupling lens has a diffraction pattern on both surfaces, and the light flux from the light source having the wavelength λ1 and the wavelength due to the diffraction effect of the diffraction patterns on the both surfaces. The light beam from the light source of λ2 can have the same back focus, and the principal ray of the light beam incident obliquely with respect to the optical axis of the condensing optical system is emitted in a direction substantially parallel to the optical axis. It is characterized by that.
[0032]
  The coupling lens for an optical pickup device according to claim 15, wherein the coupling lens has a diffraction pattern on both surfaces, and the light beam from the light source having the wavelength λ1 and the light beam from the light source having the wavelength λ1 by the diffraction effect of the diffraction pattern on one surface. The light beam from the light source having the wavelength λ2 can have the same back focus, and the diffraction effect of the diffraction pattern on the other surface causes the main light beam incident obliquely with respect to the optical axis of the condensing optical system. The light beam is emitted in a direction substantially parallel to the optical axis.
[0033]
  The coupling lens for an optical pickup device according to claim 16 is a coupling lens that converts a divergence state of a light beam from a first light source having a wavelength λ1 and a second light source having a wavelength λ2, and the divergence state is converted. A condensing optical system including an objective lens for condensing the collected light beam on the recording surface of the optical information recording medium, and a detector for detecting reflected light and / or transmitted light from the recording surface In the coupling lens for an optical pickup device for information recording / reproduction capable of recording and / or reproducing information with respect to the first and second optical information recording media having different transparent substrate thicknesses, The light source and the second light source are unitized, and the coupling lens has a diffraction pattern having the same back focus with respect to the light beam from the light source having the wavelength λ1 and the light beam from the light source having the wavelength λ2. The coupling lens is formed of at least one surface of the light beam emitted from the first light source or the second light source, and the light beam incident obliquely with respect to the optical axis of the condensing optical system. It has an off-axis characteristic that corrects off-axis coma in the condensing optical system.
[0034]
  Since the coupling lens has at least one diffraction pattern having the same back focus with respect to the light beam from the light source having the wavelength λ1 and the light beam from the light source having the wavelength λ2, Even when the second light source is unitized and the positions of the two light sources are fixed so that they cannot move separately in the direction along the optical axis of the condensing optical system, the diffraction effect of the diffraction pattern Therefore, the light beam from the light source having the wavelength λ1 and the light beam from the light source having the wavelength λ2 can have the same back focus, thereby enabling good information recording / reproduction. In addition, among the light beams emitted from the first light source or the second light source, the coupling lens uses the principal ray of the light beam incident obliquely with respect to the optical axis of the condensing optical system as an optical axis. Since the light is emitted in a substantially parallel direction, even if one of the light sources is arranged at a position that does not irradiate the light beam in the direction along the optical axis of the condensing optical system, the light source is as if Since the light beam can be irradiated in the optical axis direction so as to be on the optical axis of the condensing optical system, better information recording / reproduction can be performed. Further, since the predetermined coma aberration occurs in the off-axis light that generates a certain image height by passing through the objective lens and the transparent substrate, the reverse coma aberration is eliminated so that the coma aberration is eliminated by the coupling lens. Can effectively reduce the coma aberration in the entire condensing optical system with respect to the light beam incident obliquely with respect to the optical axis of the condensing optical system, thereby improving the information recording / Playback is possible.
[0035]
  The coupling lens for an optical pickup device according to claim 17, wherein the wavelength λ1 and the wavelength λ2 have a relationship of λ1 <λ2, and the thickness of the transparent substrate of the first optical information recording medium is t1. Since the relationship t1 <t2 is established when the thickness of the transparent substrate of the second optical information recording medium is t2, information is obtained for different recording media such as CDs and DVDs. Can be recorded / reproduced.
[0036]
  The coupling lens for an optical pickup device according to claim 18 is characterized in that the light beam emitted from the second light source is incident obliquely with respect to the optical axis of the condensing optical system.
[0037]
  According to a nineteenth aspect of the present invention, there is provided a coupling lens for an optical pickup device, which is a collimator that changes a divergent light beam incident on the coupling lens into a substantially parallel light beam with respect to an optical axis.
[0038]
  The coupling lens according to claim 20, wherein the coupling lens converts a divergent state of the light beam, and the same back focus is applied to the light beams from at least two different wavelength light sources in the light beams from at least two different wavelength light sources. And a principal ray of a light beam incident obliquely with respect to the optical axis of the coupling lens, out of the light beams of at least two different wavelengths, is formed on the coupling. The light is emitted in a direction substantially parallel to the optical axis of the lens.
[0039]
  Since the coupling lens has at least one diffraction pattern having the same back focus with respect to light beams from light sources of different at least two wavelengths, the two light sources are separately provided on the optical axis of the coupling lens. Even when the position is fixed so as not to move in the direction along the chromatic aberration, chromatic aberration correction can be performed by the diffraction effect of the diffraction pattern, thereby enabling good information recording / reproduction. The coupling lens emits a principal ray of a light beam incident obliquely with respect to the optical axis of the coupling lens out of light beams emitted from light sources having different wavelengths in a direction substantially parallel to the optical axis. Therefore, even when one of the light sources is arranged at a position that does not irradiate a light beam in a direction along the optical axis of the condensing optical system, the light source is as if it is an optical axis of the condensing optical system. As described above, since the light beam can be irradiated in the optical axis direction, better information recording / reproduction is possible.
[0040]
  The coupling lens according to claim 21 is a single lens.
[0041]
  The coupling lens according to claim 22 has a diffraction pattern only on one surface, and the principal ray of the light beam incident obliquely with respect to the optical axis of the coupling lens due to the diffraction effect of the diffraction pattern. The light is emitted in a direction substantially parallel to the optical axis of the coupling lens.
[0042]
  The coupling lens according to claim 23 has a diffraction pattern on both sides, and can have the same back focus with respect to light beams from light sources having different wavelengths by the diffraction patterns on both sides, and The principal ray of the light beam incident obliquely with respect to the optical axis of the coupling lens is emitted in a direction substantially parallel to the optical axis of the coupling lens by the diffraction effect of the diffraction patterns on both sides.
[0043]
  The coupling lens according to claim 24 has a diffraction pattern on both surfaces, and has the same back focus with respect to light beams from light sources of at least two different wavelengths by the diffraction effect of the diffraction pattern on one surface. The principal ray of the light beam incident obliquely with respect to the optical axis of the coupling lens is emitted in a direction substantially parallel to the optical axis of the coupling lens by the diffraction effect of the diffraction pattern on the other surface. Features.
[0044]
  The diffraction pattern (or diffractive surface) used in this specification is a form (or surface) in which a relief is provided on the surface of an optical element, for example, the surface of a lens, and the effect of changing the angle of light rays by diffraction is given. When there is a region where diffraction occurs on one optical surface and a region where it does not occur, the region where diffraction occurs. As the shape of the relief, for example, on the surface of the optical element, it is formed as a substantially concentric annular zone centered on the optical axis, and each annular zone is shaped like a sawtooth if the cross section is viewed in a plane including the optical axis. Are known, but include such shapes.
[0045]
  In this specification, the coupling lens means a lens or a lens group that converts divergent light from a light source into a substantially parallel light beam in an optical pickup device in a narrow sense, but is not limited thereto.
[0046]
  In this specification, examples of the optical information recording medium (optical disk) include various CDs such as CD-R, CD-RW, CD-Video, and CD-ROM, DVD-ROM, DVD-RAM, DVD-R, Various types of DVDs such as DVD + RW, DVD-RW, DVD-Video, etc., disc-shaped current optical information recording media such as MD, and next-generation recording media are also included. A transparent substrate exists on the information recording surface of many optical information recording media. However, there exist or have been proposed that the thickness of the transparent substrate is almost zero, or that there is no transparent substrate at all. For convenience of explanation, the description “through a transparent substrate” may be used in the present specification, but such a transparent substrate includes a case where the thickness is zero, that is, there is no transparent substrate.
[0047]
  In this specification, recording and reproducing information refers to recording information on the information recording surface of the information recording medium as described above and reproducing information recorded on the information recording surface. The optical pickup device of the present invention may be used only for recording or reproduction, or may be used for both recording and reproduction. Further, it may be used for recording on a certain information recording medium and reproducing on another information recording medium, or may be used for recording or recording on a certain information recording medium. It may be used for performing reproduction and recording and reproduction on another information recording medium. Note that reproduction here includes simply reading information.
[0048]
  The optical pickup device of the present invention can be mounted on audio and / or image recording and / or reproducing devices of various players or drives, or AV equipment, personal computers, and other information terminals in which they are incorporated.
[0049]
DETAILED DESCRIPTION OF THE INVENTION
  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. Each lens constituting the optical system for an optical pickup according to the present embodiment has an aspheric shape expressed by the following [Equation 1] on at least one surface of the optical surface. Where Z is an axis in the optical axis direction, h is an axis perpendicular to the optical axis, and the light traveling direction is positive, r is a paraxial radius of curvature, κ is a conical coefficient, Ai is an aspheric coefficient, and Pi is an aspheric surface It is a power number.
[0050]
[Expression 1]

[0051]
  There are two types of diffractive surfaces, the shape of which is represented by a polynomial whose shape is rotationally symmetric with respect to the optical axis, and the case of the diffraction surface which is represented by a polynomial of two axes (X, Y) perpendicular to the optical axis and orthogonal to each other.
[0052]
  The diffractive surface represented by a polynomial that is rotationally symmetric with respect to the optical axis is expressed by [Equation 2] as an optical path difference function, and the diffractive surface represented by a polynomial of axes (X, Y) perpendicular to the optical axis is the optical path. The difference function is expressed by [Equation 3] in units of mm. However, X, Y, and Z are right-handed orthogonal coordinate systems, and the design wavelength of the optical path difference function is 780 nm. FIG. 1 shows such a coordinate system.
[0053]
[Expression 2]

[0054]
[Equation 3]

[0055]
Example 1
  [Table 1] shows data related to the condensing optical system for the optical pickup device including the objective lens and the coupling lens optical system in Example 1. In the lens data shown here, a power of 10 (for example, 2.5 × 10−3) is expressed using E (for example, 2.5 × E−3). Further, the first-order light resulting from diffraction of a diffraction pattern represented by a rotationally symmetric polynomial means light whose angle of light changes in the direction of convergence after diffraction.
[0056]
[Table 1]

[0057]
  The objective lens is composed of a plurality of annular surfaces (first, second, and third annular regions) in which the collimator-side surface is concentrically divided, and each annular region uses a spherical aberration and a plurality of light sources having different wavelengths. For transparent substrates of different thicknesses, the first and third zones are corrected for aberrations within the diffraction limit for short wavelengths and thin substrates, and the second zone is diffracted for thick substrates at long wavelengths. It is a special objective lens that has been corrected for aberrations within the limits. D ′ of the second annular zone is the distance on the optical axis between the intersection of the second annular zone and the optical axis when the shape of the second annular zone is extended to the optical axis according to the aspherical shape formula and the surface of the objective lens on the transparent substrate side. Is shown. This objective lens is designed to maintain good performance when parallel light is incident from the light source side surface.
[0058]
  An HOE collimator made of an olefin resin was used as the coupling lens. On the surface of the collimator on the objective lens side, a sawtooth diffraction pattern is provided substantially concentrically with the optical axis. The refractive index of such a material is shown in [Table 2].
[0059]
[Table 2]

[0060]
  FIG. 2 is a graph showing the chromatic aberration of the collimator alone of Example 1. FIG. 2 shows that the back focus does not move regardless of the wavelength. In the case of an optical pickup device or the like using a unit in which two light sources with different wavelengths are packaged (for example, two lasers and one package), a collimator having axial chromatic aberration when the positions of light sources with different wavelengths are the same in the optical axis direction When the collimator is used, the light from at least one light source does not become parallel light after being emitted from the collimator and the performance of the entire optical pickup optical system is deteriorated. Parallel light is emitted from the optical pickup, so that the performance of the entire optical pickup optical system is maintained.
(Example 2)
  When a light source having a plurality of wavelengths is used without using an optical element such as a beam splitter, at least one light source must be installed at a position away from the optical axis. When a conventional collimator is used, the light beam emitted from the off-axis becomes a light beam that is inclined with respect to the optical axis after exiting the collimator. Worsen the performance. [Table 3] shows data related to the collimator of Example 2. A diffraction grating is provided on the light source side surface of the collimator. When the collimator of this embodiment is used in an optical pickup optical system in which a light source having a wavelength of 650 nm is installed on the optical axis and a light source having a wavelength of 780 nm is installed at a distance of 0.1 mm from the optical axis, By using the 0th order light for the light from the light source and the primary light for the light source with a wavelength of 780 nm, the light from either light source is converted into light parallel to the optical axis after exiting the collimator. Converted.
[0061]
[Table 3]

[0062]
(Example 3)
  [Table 4] shows data related to the collimator of Example 3. A surface of the collimator on the light source side has a diffraction pattern represented by a polynomial of (X, Y). Similar to the collimator of Example 2, zero-order light is used for a light source having a wavelength of 650 nm on the optical axis, and primary light is used for a light source having a wavelength of 780 nm located 0.1 mm away from the optical axis. The light from either light source can be emitted as light parallel to the optical axis. When collimated light having a wavelength of 780 nm is incident from a surface opposite to the light source of the collimator through an aperture having a diameter of 5 mm and wavefront aberration is calculated, the collimator having the diffraction grating of Example 2 has a standard deviation value of 0.010λ coma. Although aberration occurs, the collimator of Example 3 is corrected to 0.000λ by using a diffraction pattern represented by a polynomial of (X, Y) instead of the diffraction grating.
[0063]
[Table 4]

[0064]
(Example 4)
  [Table 5] shows data related to the collimator of Example 4. The collimator has a diffraction pattern represented by a (X, Y) polynomial on the light source side surface, and a diffraction pattern represented by a rotationally symmetric polynomial with respect to the optical axis on the opposite surface. ing. By using the first-order diffracted light by the diffraction pattern provided on the surface opposite to the light source, even if the position of the light source with the wavelength of 650 nm and the light source with the wavelength of 780 nm are the same in the optical axis direction, Parallel light is obtained. The first-order diffracted light by the diffraction pattern provided on the surface on the light source side converts the principal ray of the light beam from the light source having a wavelength of 780 nm installed at a position 0.1 mm away from the optical axis into a light beam parallel to the optical axis. Have Therefore, the collimator of this embodiment is used in an optical pickup optical system together with a light source unit in which two lasers are combined into one package in which a light source having a wavelength of 650 nm and a light source having a wavelength of 780 nm are installed in parallel at an interval of 0.1 mm. Thus, the light from either light source is converted into light parallel to the optical axis after exiting the collimator.
[0065]
[Table 5]

[0066]
(Example 5)
  [Table 6] shows data related to the optical pickup optical system of Example 5. When a conventional collimator is used, the light beam emitted from the off-axis light source becomes a light beam that is inclined with respect to the optical axis after exiting the collimator. It degrades the performance of the entire system. In the collimator of this embodiment, the collimator has an off-axis characteristic that corrects coma aberration generated in the objective lens and the transparent substrate when an off-axis light source is used. In an optical pickup optical system in which a light source having a wavelength of 780 nm is installed at a position 0.1 mm away from the optical axis, an open limit is provided so that the NA on the transparent substrate side is 0.45. When the total wavefront aberration is calculated, the coma aberration is corrected to a standard deviation value of 0.001λ or less.
[0067]
[Table 6]

[0068]
  Note that the collimator has a diffraction pattern only on one surface, the chromatic aberration is corrected by the diffraction effect of the diffraction pattern, and / or the principal ray of the light beam incident obliquely with respect to the optical axis of the condensing optical system. The light may be emitted in a direction substantially parallel to the optical axis, or the collimator has diffraction patterns on both sides, and chromatic aberration is corrected by the diffraction effect of the diffraction patterns on both sides, and / or The principal ray of the light beam incident obliquely with respect to the optical axis of the optical optical system may be emitted in a direction substantially parallel to the optical axis, and further, has a diffraction pattern on both sides of the collimator, The chromatic aberration is corrected by the diffraction effect of the diffraction pattern on one surface, and the light is incident obliquely on the optical axis of the condensing optical system by the diffraction effect of the diffraction pattern on the other surface. The main ray of the beam may be adapted to be incident in a direction substantially parallel to the optical axis.
[0069]
  FIG. 3 is a schematic diagram showing the optical pickup device of the present embodiment. In the optical pickup device 100 shown in FIG. 3, a first semiconductor laser 111 and a second semiconductor laser 112 which are two lasers and one package are fixed in parallel and unitized. The collimator 130 can use the first to fifth embodiments.
[0070]
  When reproducing the first optical disk (for example, DVD), the light is emitted from the first semiconductor laser 111 as a light source disposed on the optical axis of the collimator (coupling lens) 130 and the objective lens 160 constituting the condensing optical system. The transmitted light beam (wavelength 635 or 650 nm) passes through the beam splitter 230 and the collimator 130 and becomes a parallel light beam. Further, the aperture is narrowed down by a diaphragm 170 and focused on the information recording surface 220 by the objective lens 160 through the transparent substrate 210 of the first optical disk 200.
[0071]
  Then, the light beam modulated and reflected by the information pits on the information recording surface 220 is transmitted again through the collimator 130 via the objective lens 160 and the diaphragm 170, reflected by the beam splitter 230, and then reflected by the sensor lens 310. The light incident on the detector 300 is used to obtain a read signal of information recorded on the first optical disc 200 using the output signal.
[0072]
  Further, a change in the amount of light due to a change in the shape and position of the spot on the photodetector 300 is detected, and focus detection and track detection are performed. The two-dimensional actuator 150 moves the objective lens 160 for focusing and tracking. Can be moved.
[0073]
  The first semiconductor laser 111 and the second semiconductor laser 112 which are two lasers and one package are fixed in parallel and unitized, and the two light sources cannot move separately in the direction along the optical axis of the condensing optical system Even when the position is fixed as described above, chromatic aberration correction can be performed.
[0074]
  When reproducing the second optical disk (for example, CD), the light beam (wavelength 780 nm) emitted from the second semiconductor laser 112 as the light source disposed off the axis of the condensing optical system is substantially the same as the optical axis of the collimator 130. The light is incident obliquely so as to be coaxial, and further passes through the collimator 130 to become a substantially parallel light beam. Further, the light is condensed on the information recording surface 220 ′ via the aperture 170 and the objective lens 160 and the transparent substrate 210 of the second optical disk 200.
[0075]
  Then, the light beam modulated and reflected by the information pits on the information recording surface 220 ′ is transmitted again through the collimator 130 through the objective lens 160 and the diaphragm 170, reflected by the beam splitter 230, and incident on the photodetector 300. Then, a read signal of information recorded on the second optical disc 200 is obtained using the output signal.
[0076]
  Further, a change in the amount of light due to a change in the shape and position of the spot on the photodetector 300 is detected, and focus detection and track detection are performed. Based on this detection, the two-dimensional actuator 150 performs focusing and tracking. The objective lens 160 can be moved.
[0077]
  As in this embodiment, the laser beam for DVD that should be converged more accurately for information recording is placed on the optical axis by placing the first semiconductor laser 111 on the optical axis of the condensing optical system. The laser light for CD that does not need to be converged as accurately as the DVD for information recording is applied to the second semiconductor so that the best optical characteristics of the condensing optical system can be exhibited. The laser 112 is incident obliquely with respect to the optical axis of the collimator 130 and then converted into parallel light. Note that when the laser light from the second semiconductor laser 112 is incident on the optical axis obliquely from the off-axis of the collimator 130, the collimator so as to eliminate the coma generated when passing through the objective lens 160. If coma aberration is generated in the laser light from the second semiconductor laser 112 that has passed through 130, the coma aberration can be satisfactorily corrected in the entire condensing optical system.
[0078]
【The invention's effect】
  According to the present invention, it is possible to provide a coupling lens for an optical pickup device and an optical pickup device capable of recording / reproducing information satisfactorily even when a laser light source unit such as two lasers and one package is used.
[Brief description of the drawings]
FIG. 1 is a diagram showing a coordinate system related to an optical path difference function of a diffractive surface of a collimator.
2 is a graph showing chromatic aberration of a single collimator of Example 1. FIG.
FIG. 3 is a schematic view showing an optical pickup device of the present embodiment.
[Explanation of symbols]
100 Optical pickup device
111 First semiconductor laser
112 Second semiconductor laser
130 collimator
160 Objective lens
170 aperture
200 First optical disc or second optical disc
300 photodetector

Claims (24)

A coupling lens for converting the divergence state of the light beam from the first light source having the wavelength λ1 and the second light source having the wavelength λ2, and for condensing the light beam converted from the divergence state on the recording surface of the optical information recording medium. First and second optical information having different transparent substrate thicknesses, and a condensing optical system including the objective lens and a detector for detecting reflected light and / or transmitted light from the recording surface. In an optical pickup device for recording / reproducing information capable of recording and / or reproducing information with respect to a recording medium,
Unitizing the first light source and the second light source,
The coupling lens has a diffraction pattern that have the same back focus with respect to the light beam from the light beam as a light source of the wavelength λ2 from the light source of the wavelength .lambda.1, optical pickup, wherein the forming at least one surface apparatus. A coupling lens for converting the divergence state of the light beam from the first light source having the wavelength λ1 and the second light source having the wavelength λ2, and for condensing the light beam converted from the divergence state on the recording surface of the optical information recording medium. First and second optical information having different transparent substrate thicknesses, and a condensing optical system including the objective lens and a detector for detecting reflected light and / or transmitted light from the recording surface. In an optical pickup device for recording / reproducing information capable of recording and / or reproducing information with respect to a recording medium,
Unitizing the first light source and the second light source,
The coupling lens is a diffraction pattern consisting of at least one surface,
The light beam from the light source having the wavelength λ1 and the light beam from the light source having the wavelength λ2 have the same back focus, and the principal ray of the light beam incident obliquely with respect to the optical axis of the condensing optical system is defined as the optical axis. An optical pickup device having a diffraction pattern for emitting light in a substantially parallel direction . The optical pickup apparatus of claim 2 wherein the coupling lens is characterized by a single lens der Rukoto. The optical pickup device according to claim 2, wherein the coupling lens has a diffraction pattern only on one surface . The coupling lens has a diffraction pattern on both surfaces, and has the same back focus with respect to the light beam from the light source of wavelength λ1 and the light beam from the light source of wavelength λ2 due to the diffraction effect of the diffraction patterns on both surfaces, 4. The optical pickup device according to claim 3 , wherein a principal ray of a light beam incident obliquely with respect to the optical axis of the condensing optical system is emitted in a direction substantially parallel to the optical axis. . The coupling lens has a diffraction pattern on both sides, and has the same back focus with respect to the light beam from the light source of wavelength λ1 and the light beam from the light source of wavelength λ2 due to the diffraction effect of the diffraction pattern on one surface. The diffraction effect of the diffraction pattern on the other surface causes the principal ray of the light beam incident obliquely with respect to the optical axis of the condensing optical system to be emitted in a direction substantially parallel to the optical axis. The optical pickup device according to claim 3 . A coupling lens for converting the divergence state of the light beam from the first light source having the wavelength λ1 and the second light source having the wavelength λ2, and for condensing the light beam converted from the divergence state on the recording surface of the optical information recording medium. First and second optical information having different transparent substrate thicknesses, and a condensing optical system including the objective lens and a detector for detecting reflected light and / or transmitted light from the recording surface. In an optical pickup device for recording / reproducing information capable of recording and / or reproducing information with respect to a recording medium,
The first light source and the second light source are unitized,
The coupling lens forms a diffraction pattern having the same back focus with respect to the light beam from the light source of wavelength λ1 and the light beam from the light source of wavelength λ2, on at least one surface, and the first light source or the first light source Among the light beams emitted from the light source 2, the light beam incident obliquely with respect to the optical axis of the condensing optical system has an off-axis characteristic that corrects off-axis coma aberration in the condensing optical system. A characteristic optical pickup device. The wavelength λ1 and the wavelength λ2 have a relationship of λ1 <λ2, the thickness of the transparent substrate of the first optical information recording medium is t1, and the thickness of the transparent substrate of the second optical information recording medium is The optical pickup device according to claim 1, wherein a relationship of t <b> 1 <t <b> 2 is established, where t <b> 2 is t <b> 2 . The light beam emitted from the second light source, the optical pickup apparatus according to claim 8, characterized that you incident obliquely with respect to the optical axis of the focusing optical system. The optical pickup device according to any one of claims 1 to 8, wherein the coupling lens is characterized Oh Rukoto a collimator to substantially parallel light beam to the optical axis of the divergent light flux is incident. A coupling lens for converting the divergence state of the light beam from the first light source having the wavelength λ1 and the second light source having the wavelength λ2, and for condensing the light beam converted from the divergence state on the recording surface of the optical information recording medium. First and second optical information having different transparent substrate thicknesses, and a condensing optical system including the objective lens and a detector for detecting reflected light and / or transmitted light from the recording surface. In a coupling lens for an optical pickup device for recording and reproducing information capable of recording and / or reproducing information on a recording medium,
The first light source and the second light source are unitized,
The coupling lens has a diffraction pattern consisting of at least one surface , and has the same back focus with respect to the light beam from the light source having the wavelength λ1 and the light beam from the light source having the wavelength λ2, and the light of the condensing optical system coupling lens for the optical pickup device characterized that you have had a diffraction pattern which mainly emits light of a light beam incident in a direction substantially parallel to the optical axis obliquely with respect to the axis. The coupling lens for an optical pickup device according to claim 11 , wherein the coupling lens is a single lens . The coupling lens, the coupling lens for the optical pickup device according to claim 1 1 or 1 2, characterized in that having a diffraction pattern only on one side. The coupling lens has a diffraction pattern on both surfaces, and has the same back focus with respect to the light beam from the light source of wavelength λ1 and the light beam from the light source of wavelength λ2 due to the diffraction effect of the diffraction patterns on both surfaces, the optical pickup according to claim 1 2, characterized that you have adapted to emit a principal ray of a light beam incident from an oblique direction with respect to the optical axis of said focusing optical system in a direction substantially parallel to the optical axis Coupling lens for equipment. The coupling lens has a diffraction pattern on both sides, and has the same back focus with respect to the light beam from the light source of wavelength λ1 and the light beam from the light source of wavelength λ2 due to the diffraction effect of the diffraction pattern on one surface. The diffraction effect of the diffraction pattern on the other surface causes the principal ray of the light beam incident obliquely with respect to the optical axis of the condensing optical system to be emitted in a direction substantially parallel to the optical axis. The coupling lens for an optical pickup device according to claim 12, wherein the coupling lens is an optical pickup device. A coupling lens for converting the divergence state of the light beam from the first light source having the wavelength λ1 and the second light source having the wavelength λ2, and for condensing the light beam converted from the divergence state on the recording surface of the optical information recording medium. First and second optical information having different transparent substrate thicknesses, and a condensing optical system including the objective lens and a detector for detecting reflected light and / or transmitted light from the recording surface. In a coupling lens for an optical pickup device for recording and reproducing information capable of recording and / or reproducing information on a recording medium,
The first light source and the second light source are unitized,
The coupling lens forms a diffraction pattern having the same back focus with respect to the light beam from the light source of wavelength λ1 and the light beam from the light source of wavelength λ2 , on at least one surface, and the first light source or the first light source of the light beam emitted from the second light source, that having a-axis characteristics as to correct the off-axis coma in the light converging optical system of the light beam incident from an oblique direction with respect to the optical axis of said focusing optical system coupling lens for the optical pickup device you wherein a. The wavelength λ1 and the wavelength λ2 have a relationship of λ1 <λ2, the thickness of the transparent substrate of the first optical information recording medium is t1, and the thickness of the transparent substrate of the second optical information recording medium is 17. The coupling lens for an optical pickup device according to claim 11, wherein a relationship of t <b> 1 <t <b> 2 is established when t <b> 2 is t <b> 2 . 18. The coupling lens for an optical pickup device according to claim 17, wherein the light beam emitted from the second light source is incident obliquely with respect to the optical axis of the condensing optical system . The coupling lens for an optical pickup device according to any one of claims 11 to 18, wherein the coupling lens is a collimator that makes a divergent light beam incident on the coupling lens substantially parallel to an optical axis. . In a coupling lens that converts the divergent state of the light beam,
For light fluxes from light sources of at least two different wavelengths, having a diffraction pattern from at least one surface having the same back focus,
Of each of the light flux of the at least two different wavelengths, Rukoto to emit a principal ray of a light beam incident from an oblique direction with respect to the optical axis of the coupling lens in a direction substantially parallel to the optical axis of the coupling lens the characteristics and to Luke Tsu pulling lens. Ca Tsu pulling lens of claim 20 wherein the coupling lens which is a single lens. The coupling lens, mosquitoes Tsu pulling lens according to claim 20 or 21, characterized in Rukoto to have a diffraction pattern only in one plane. The coupling lens has a diffraction pattern on both sides, and has the same back focus with respect to light beams from light sources of at least two different wavelengths by the diffraction patterns on both sides,
By the diffraction effect of the diffraction pattern of the two-sided, and features that you exit the principal ray of the light beam incident from an oblique direction with respect to the optical axis of the coupling lens in a direction substantially parallel to the optical axis of the coupling lens coupling lens of claim 2 1,. The coupling lens has a diffraction pattern on both sides, and has the same back focus with respect to light beams from light sources of at least two different wavelengths due to the diffraction effect of the diffraction pattern on one side,
By the diffraction effect of the diffraction pattern in the other surface, characterized that you exit the principal ray of the light beam incident from an oblique direction with respect to the optical axis of the coupling lens in a direction substantially parallel to the optical axis of the coupling lens The coupling lens according to claim 21 .

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