JP4121213B2 - Coupling lens and optical pickup - Google Patents

Description

上において、例えば「Ｅ−６」は「１０~⁶」を意味する。
このカップリングレンズに平行光束を入射させた場合の画角（単位：度）：０，０．３３，０．６７，１．００に対する波面収差は以下の通りであり、性能良好である。

このカップリングレンズを射出成形により形成し、位置調整用の溝を幅：１．５ｍｍ、深さ：１．５ｍｍに形成し、図１の如き光ピックアップのカップリングレンズ１０２として用い、図９に示す調整具６０Ｂにより光軸方向の位置調整を行い、極めて容易に精度良く位置調整を行うことができ、設計通りのコリメート作用を実現でき、性能良好な光ピックアップを実現できた。
図１０に、実施例１のカップリングレンズによるコリメート作用を示す。符号７０がカップリングレンズ、符号８０は半導体レーザの発光部、符号９０は半導体レーザのパッケージのカバーガラスを示す。
【００１７】
実施例２
実施例２のカップリングレンズは、光学作用が「コリメート作用とビーム成形作用」であるものである（請求項９、１０）。即ち、このカップリングレンズは、光軸に直交し、且つ、互いに直交するｘ方向とｙ方向に異なる焦点距離を有し、ｘ方向の焦点距離：ｆｘ＝１２．５ｍｍ、ｙ方向の焦点距離：ｆｙ＝３０ｍｍであり、半導体レーザからの発散性の光束をコリメートして平行光束にするとともに、光束の断面形状を略円形に「ビーム整形」する（請求項１１）。ビーム整形倍率：ｆｙ／ｆｘ＝２．４倍である。
このカップリングレンズは、有効径：５ｍｍ、レンズ外径：６ｍｍであり、肉厚：１０．２７９４９５ｍｍである。即ち、肉厚がレンズの有効径に比して大きい（請求項１）。
各面は「非球面」であり、光軸方向をｚ軸、光軸に直交し、互いに直交する２方向をＸ，Ｙ方向とするとき、ＸＺ面内の近軸曲率をＲ_X、ＹＺ面内の近軸曲率をＲ_Y、ＸＺ面内の円錐定数をＫ_X、ＹＺ面内の円錐定数をＫ_Y、円錐形状からの４次，６次，８次，１０次の変形変数の回転対称成分を、それぞれＡＲ，ＢＲ，ＣＲ，ＤＲ、同非回転対称成分をＡＰ，ＢＰ，ＣＰ，ＤＰとして、次式：
Z=(R_XX²+R_YY²)/[1+√{1-(1+K_X)R_X ²X²-(1+K_Y)R_Y ²Y²}]
+AR[(1-AP)X²+(1+AP)Y²]²+BR[(1-BP)X²+(1+BP)Y²]³
+CR[(1-CP)X²+(1+CP)Y²]⁴+DR[(1-DP)X²+(1+DP)Y²]⁵
で表される。レンズデータ（上記「近軸曲率」に関しては、その逆数（1/R_X，1/R_Y）の「近軸曲率半径」を与える）は以下の通りである。
【００１８】
波長：６３５ｎｍの光に対する屈折率：Ｎ＝１．５８０８９２
中心肉厚：１０．２７９４９５ｍｍ

画角（単位：度）：０，０．５，１．００（入射瞳径：４．０ｍｍ）に対する波面収差は以下の通りである。

図１に示す光ピックアップのカップリングレンズ１０２として、このレンズを用い、対物レンズとして両面が共軸非球面（前述の共軸非球面の式で表される）で、以下のデータを有するものとを組み合わせた。
波長：６３５ｎｍの光に対する屈折率：Ｎ＝１．７２６５９２
中心肉厚：１．５ｍｍ

この対物レンズによる集束光束を、基板厚さ：０．６ｍｍのＤＶＤの記録面に集光させたときの、ＸＺ断面を図１１に、ＹＺ断面を図１２に示す。
符号７１がカップリングレンズ、符号７３は対物レンズ、符号７５はＤＶＤの基板を示している。波長：λ＝６３５ｎｍの光源に対し、記録面上の光スポットにおける波面収差は軸上で０．００３λであり、回折限界の光スポットを得るには十分な波面収差である。
このカップリングレンズを射出成形により形成し、位置調整用の溝を幅：１．５ｍｍ、深さ：１．５ｍｍで周面を１周するように形成し、また、図３（ｂ）に示す如き光軸方向に長い長孔１４ａを、幅：１．５ｍｍ、深さ：１．５ｍｍに形成し、図９に示す調整具６０Ｂにより光軸方向の位置調整を行い、調整具６０Ａにより光軸回りの位置調整を行い、極めて容易に精度良く位置調整を行うことができ、設計通りのコリメート作用・ビーム整形作用を実現でき、性能良好な光ピックアップを実現できた。
【００１９】
【発明の効果】
以上に説明したように、この発明によれば新規なカップリングレンズと光ピックアップを実現できる。この発明のカップリングレンズは、レンズ周面に位置調整用の孔もしくは溝を有するので、レンズセルを用いること無く、光軸方向および／または光軸回りの位置調整を極めて容易且つ確実に実現でき、半導体レーザに対する設計上のカップリング作用を実現することができる。この発明の光ピックアップは上記カップリングレンズを用いることにより、設計上の良好な光学特性を実現できる。
【図面の簡単な説明】
【図１】この発明の光ピックアップの実施の１形態を説明するための図である。
【図２】この発明のカップリングレンズの実施の形態を３例示す図である。
【図３】この発明のカップリングレンズの実施の別形態を３例示す図である。
【図４】この発明のカップリングレンズの実施の他の形態を２例示す図である。
【図５】この発明のカップリングレンズの実施の他の形態を示す図である。
【図６】図２（ａ）に示すカップリングレンズの光軸方向の位置調整方法を説明する図である。
【図７】図３（ａ）に示すカップリングレンズの光軸方向の位置調整方法を説明する図である。
【図８】図３（ｃ）に示すカップリングレンズの光軸回りの位置調整方法を説明する図である。
【図９】請求項１ 2 記載のカップリングレンズと、その位置調整方法を説明するための図である。
【図１０】実施例１のカップリングレンズのレンズ作用を示す図である。
【図１１】実施例２のカップリングレンズのＸＺ面内のレンズ作用を説明するための図である。
【図１２】実施例２のカップリングレンズのＹＺ面内のレンズ作用を説明するための図である。
【符号の説明】
１０ カップリングレンズ
１０ａ 位置調整用の孔[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a coupling lens and an optical pickup.
[0002]
[Prior art]
As is well known, the light beam emitted from the semiconductor laser is divergent, so in general, the light beam from the semiconductor laser is converted into a light beam form suitable for an optical system (parallel light beam, weak divergent or weakly convergent light beam). In order to do this, a coupling lens is used.
In an optical device using a semiconductor laser as a light source, such as an optical pickup or an optical scanning device, the light beam from the semiconductor laser is focused on a very small light spot, so the optical system is designed with high precision. In order to achieve the optical performance of the street, it is necessary to deploy each optical system with high positional accuracy. Especially, the position in the optical axis direction of the coupling lens that couples the light beam from the semiconductor laser is adjusted with extremely high accuracy. Need to be done.
In general, the lens position is adjusted by attaching a lens to a lens cell having an adjustment hole, holding the lens cell on a holder, and adjusting the position of the lens cell with respect to the holder. Such lens position adjustment leads to an increase in size and cost of an optical member near the light source by using a lens cell.
[0003]
[Problems to be solved by the invention]
  This invention does not require a lens cell for position adjustment,For optical pickupThe realization of a coupling lens is an issue. Another object of the present invention is to reduce the size and cost of an optical pickup by using the coupling lens.
[0004]
[Means for Solving the Problems]
  The coupling lens of the present invention is “In an optical pickup that couples a divergent light beam from a semiconductor laser with a coupling lens, condenses it on the recording surface of an optical recording medium by an objective lens, and performs one or more of recording, reproducing, and erasing information.And a coupling lens for coupling a divergent light beam from a semiconductor laser.
  The coupling lens of the present invention is “It has a wall thickness that is approximately equal to or larger than the effective diameter of the lens, and can be adjusted in the optical axis direction and / or around the optical axis without using a lens cell in the holding part of the housing. The face part is held directly,The peripheral surface portion sandwiched between the incident side surface and the exit side surface is provided with one or more holes for position adjustment at a depth that does not shield the effective light beam.
  In the coupling lens according to claim 1, the position adjusting hole may be a “long hole” (Claim 2). In this case, the longitudinal direction of the long hole is defined as “a direction parallel to the optical axis”. (Claim 3) or “a direction orthogonal to the optical axis” (Claim 4).
  The longitudinal direction of the long hole being “a direction perpendicular to the optical axis” means that the longitudinal direction is a direction parallel to a line of intersection between a plane perpendicular to the optical axis and the lens peripheral surface.
  In the coupling lens according to any one of claims 1 to 4, a plurality of position adjusting holes may be formed, and the plurality of holes may be formed "axisymmetric with respect to the optical axis as a symmetry axis". (Claim 5).
[0005]
  The coupling lens according to claim 6.“In an optical pickup that couples a divergent light beam from a semiconductor laser with a coupling lens, condenses it on the recording surface of an optical recording medium with an objective lens, and performs one or more of recording, reproducing, and erasing information, the semiconductor laser A coupling lens that couples a divergent light beam from the lens, and has a thickness that is substantially equal to or larger than the effective diameter of the lens, and without using a lens cell in the holding portion of the housing, The cylindrical circumferential surface portion is directly held so as to be adjustable in the optical axis direction and / or around the optical axis, and the depth of the position adjusting groove that does not block the effective light flux in the circumferential surface portion sandwiched between the incident side surface and the exit side surface The above peripheral surface portion was provided around one round.It is characterized by.
  the aboveClaims 1-6The coupling lens described in any one of (1) can be produced by various methods as to its production method, and in particular, it can be produced by “molding with a mold (molding or injection molding)” (Claim 7). In this way, since the holes and grooves for position adjustment can be formed integrally, lens manufacturing is easy.
  UpClaims 1-7The optical action of the coupling lens described in any one of (1) can be optically symmetric (Claim 8), Or an optical action such as “having different focal lengths in two directions orthogonal to the optical axis and orthogonal to each other” (Claim 9). the aboveClaim 8In the described coupling lens, the optically symmetric optical action of the lens can be a collimating action (Claim 10). Also, aboveClaim 9In the described coupling lens, different focal lengths in two directions orthogonal to each other can be set so that “the divergent light beam from the semiconductor laser is converted into a parallel light beam whose cross-sectional shape is nearly circular” (Claim 11).
  The coupling lens is a “single lens”. However, such a single lensClaim 7Except for the case of manufacturing by molding using a mold like the described coupling lens, it is not always necessary to be a single lens, and a plurality of lenses can be bonded to form a “single lens”. Therefore, it goes without saying that one or more joint surfaces may exist between the incident side surface and the exit side surface, and the optical materials of the respective lens components to be joined can be made different.
[0006]
  Claim 12The coupling lens ofIn an optical pickup that couples a divergent light beam from a semiconductor laser by a coupling lens, condenses it on a recording surface of an optical recording medium by an objective lens, and performs one or more of recording / reproducing / erasing information from the semiconductor laser. A coupling lens for coupling a divergent light beam having the following characteristics.
That is, an optical axis symmetric lens portion having an optical action symmetric to the optical axis and an anamorphic lens portion having different optical actions in two directions orthogonal to the optical axis and orthogonal to each other. The portion is configured to realize an anamorphic optical action.
  The optical axis symmetric lens portion and the anamorphic lens portion have a thickness substantially equal to or larger than the effective diameter of the lens, and without using a lens cell in the holding portion of the housing, and / or in the optical axis direction. The cylindrical peripheral surface portion is directly held so as to be adjustable around the optical axis.
  The optical axis symmetric lens portion is provided with one or more holes for position adjustment in the optical axis direction or grooves for position adjustment in the optical axis direction at a depth that does not block the effective light beam.
Further, the anamorphic lens portion is provided with one or more holes for adjusting the position around the optical axis at a depth that does not block the effective light beam.
  In this case, the optical axis symmetric lens portion and / or the anamorphic lens portion can be manufactured by “molding by a mold” such as molding or injection molding, or configured as a cemented lens by bonding a plurality of lens components. You can also
  In the optical pickup according to the present invention, a divergent light beam from a semiconductor laser is coupled by a coupling lens, and condensed on a recording surface of an optical recording medium by an objective lens, thereby performing one or more of information recording / reproducing / erasing. In optical pickup,Claims 1-12The coupling lens according to any one of 1 is used (Claim 13).
[0007]
DETAILED DESCRIPTION OF THE INVENTION
  FIG. 1 schematically shows an embodiment of an optical pickup according to the present invention.
  A divergent light beam from the semiconductor laser 101 that is a light source is converted into a light beam shape suitable for the subsequent optical system by the coupling lens 102, passes through the polarization beam splitter 103 and the quarter wavelength plate 104, and is deflected by the deflection prism 105. The optical path is bent and enters the objective lens 106, becomes a converged light beam by the action of the objective lens 106, enters the optical recording medium 107 such as a CD (compact disc) or a DVD (digital video disc), and the substrate of the optical recording medium 107. And is condensed as a light spot on the recording surface. The optical recording medium 107 is scanned on a track by a light spot, information is recorded or reproduced, or information is erased.
  The light beam reflected by the recording surface becomes a “return light beam”, passes through the objective lens 106, is reflected by the deflection prism 105, and passes through the quarter-wave plate 104. At this stage, the light beam has passed through the quarter-wave plate 104 twice, and the polarization plane turns 90 degrees from the original direction. Accordingly, the return light beam incident on the polarization beam splitter 103 is reflected by the polarization beam splitter 103. This reflected light beam becomes a condensed light beam given astigmatism by the anamorphic condensing lens 108, and enters the light receiving unit 109. The light receiving unit 109 has a light receiving surface divided into four parts, and information signals (when reproducing information) and servo signals (focusing signals by the astigmatism method, push-pull method, etc.) based on the light reception signals obtained from the respective light receiving surfaces Tracking signal) is obtained. Based on this servo signal, focusing, tracking, etc. are executed.
  When there is a margin in the amount of light from the light source, a normal beam splitter can be used instead of the deflecting beam splitter, and in this case, a quarter wavelength plate is unnecessary.
  That is, the optical pickup shown in FIG. 1 couples the divergent light beam from the semiconductor laser 101 by the coupling lens 102, condenses it on the recording surface of the optical recording medium 107 by the objective lens 106, and records and reproduces information. An optical pickup that performs one or more erasures. Of course, the optical pickup according to the present invention may have a configuration other than that shown in FIG. 1, and a known method may be used for obtaining a focusing signal and a tracking signal.
  The coupling lens 102 converts the divergent light beam into a “light beam form suitable for the subsequent optical system” in order to couple the divergent light beam from the semiconductor laser 101 to the subsequent optical system. In order to exhibit a desired coupling function, extremely accurate position adjustment is required. In order to easily perform this highly accurate position adjustment, as the coupling lens 102 of the optical pickup,Claims 1-12The coupling lens described in any one of (1) is used (Claim 13).
[0008]
Hereinafter, embodiments of the coupling lens will be described.
FIG. 2 shows three embodiments of the coupling lens.
Each of the three types of coupling lenses 10, 11, and 12 shown in FIGS. 2A, 2B, and 2C is a coupling lens that couples a divergent light beam from a semiconductor laser. One or more holes for position adjustment are provided in the peripheral surface portion sandwiched between the incident side surface and the exit side surface to a depth that does not shield the effective light beam.
That is, the coupling lens 10 shown in FIG. 2A is provided with a position adjusting hole 10a on the peripheral surface portion. The peripheral surface of the coupling lens 11 shown in (b) is provided with two holes 11a and 11b for position adjustment, and the coupling lens 12 shown in (c) has four holes 12a and 12a for position adjustment. 12b, 12c, and 12d are provided. Since these holes 10a, 11a, 11b, 12a, 12b, 12c, and 12d are formed as holes directly on the peripheral surfaces of the coupling lenses 10, 11, and 12, the holes pass through the coupling lens. The depth of each hole must be “a depth that does not shield the effective light beam” so as not to shield the periphery of the effective light beam.
In addition, the coupling lenses 11 and 12 shown in FIGS. 2B and 2C have a plurality of holes for position adjustment, and these holes are “axisymmetric with respect to the optical axis as a symmetry axis”. (Claim 5). As described above, the arrangement of the plurality of holes for position adjustment in an axial symmetry with the optical axis as the symmetry axis has the following technical significance. In other words, the stress due to the position adjusting hole causes the wavefront deterioration of the light beam subjected to the coupling action. However, if the position adjusting hole arrangement is axisymmetric with respect to the optical axis, the wavefront is deteriorated. Is distributed and reduced symmetrically around the optical axis, and can suppress the occurrence of large wavefront degradation.
[0009]
  In FIG.For optical pickupThree other forms of implementation of a coupling lens are shown.
  Each of the three types of coupling lenses 13, 14, and 15 shown in FIGS. 3A, 3B, and 3C is a coupling lens that couples a divergent light beam from a semiconductor laser. One or more holes for position adjustment are provided in the peripheral surface portion sandwiched between the incident side surface and the exit side surface to a depth that does not shield the effective light beam.
  The coupling lens 10 shown in FIG. 3A is provided with a hole 13a for position adjustment on the peripheral surface portion. A position adjusting hole 14a is provided on the peripheral surface of the coupling lens 14 shown in FIG. 5B, and a position adjusting hole 15a is provided in the coupling lens 15 shown in FIG.
  It goes without saying that the depth of each hole is set to “depth that does not shield the effective light beam” so that these holes 13a, 14a, and 15a do not block the periphery of the effective light beam that passes through the coupling lens. Nor.
  The position adjusting holes 13a, 14a, and 15a shown in FIGS. 3A, 3B, and 3C are all “long holes”. The long holes 14a and 15a have a longitudinal direction parallel to the optical axis (Claim 3), and the long holes 13a have a longitudinal direction perpendicular to the optical axis (Claim 4). The ends of the long holes in the longitudinal direction may have a planar shape that intersects in the longitudinal direction like the long holes 13a and 14a, or may be “rounded” like the long holes 15a.
[0010]
In the second embodiment shown in FIG. 4, the coupling lens 16 has two long holes 16 a and 16 b that are long in the direction orthogonal to the optical axis as the position adjusting hole. Position adjusting holes 17a, 17b, 17c, and 17d are formed.
The long holes 16a and 16b and the holes 17a, 17b, 17c and 17d are formed so as to be “axisymmetric with respect to the optical axis as a symmetry axis” (Claim 5), and are “large” like the coupling lenses 12 and 13 in FIG. The occurrence of wavefront deterioration can be suppressed ”.
When a plurality of position adjusting holes are provided symmetrically with respect to the optical axis, the number of holes is not limited to the even number (two or four) exemplified above, and may be an odd number.
In the embodiment shown in FIG. 5, the coupling lens 18 has the circumferential surface portion sandwiched between the incident side surface and the exit side surface, and the groove 18 a for position adjustment has a depth at which the effective light beam is not shielded. One round is provided (Claim 6).
In this way, when the position adjusting groove 18a makes one round of the lens peripheral surface portion, the above-described effect of “suppression of wavefront deterioration” can be further enhanced.
[0011]
  As illustrated above, the coupling lens has a hole or groove for position adjustment formed in the lens body. Therefore, a method of “molding with a mold” such as molding or injection molding is suitable as the manufacturing method. Yes (Claim 7). However, in molding with a mold, in the process of cooling, the presence of position adjusting holes and grooves tends to cause stress non-uniformity in the lens. However, such deterioration of the wavefront aberration may be caused by arranging a plurality of holes symmetrically on the optical axis, or by positioning a groove for position adjustment on the peripheral surface as described above. By forming so as to make one round, it can be suppressed and reduced.
  Considering the ease of forming holes and grooves for position adjustment and the stability of the lens during position adjustmentOf this inventionIn the coupling lens, as illustrated above, the thickness of the lens is set to be approximately equal to the effective diameter of the lens or larger than the effective diameter of the lens (Claim 1).
[0012]
A method for adjusting the position of the coupling lens using the position adjusting holes will be described with reference to FIGS. 6 to 8 exemplify a coupling lens having one position adjusting hole, the adjustment method is the same even if there are a plurality of position adjusting holes. 6-8, the coupling lens has shown the state hold | maintained at the holding part which is not illustrated in figure.
The coupling lens 10 shown in FIG. 6 is the same as that shown in FIG. 2A. In this example, the optical action is symmetric with respect to the optical axis. Therefore, the position adjustment is a position adjustment in the optical axis direction. The coupling lens 10 is set in a holding portion (a groove having a V-shaped cross section with the optical axis direction as a longitudinal direction) of a housing (not shown). In this state, the tip of the adjustment pin 50 is inserted into the hole 10a, and the adjustment pin 50 is displaced in the optical axis direction. Then, the coupling lens 10 contacts the groove walls on the two surfaces of the holding portion and is displaced in the optical axis direction while maintaining the optical axis direction. Using this displacement, position adjustment in the optical axis direction is performed. If the coupling lens 10 is an anamorphic lens and it is necessary to adjust the position around the optical axis, the adjustment pin 50 is displaced in the direction perpendicular to the optical axis, and the coupling lens 10 is moved around the optical axis. It may be adjusted by rotating.
[0013]
  The coupling lens 13 shown in FIG. 6 is the same as that shown in FIG. 3A, and a long hole 13a for position adjustment is formed in the peripheral surface portion with the longitudinal direction being the direction perpendicular to the optical axis. ing. In this example, the optical action of the coupling lens 13 is symmetric with respect to the optical axis, and the position adjustment is performed in the optical axis direction. The coupling lens 13 is held by a holding portion of the housing similar to the above, and can be displaced in the optical axis direction while maintaining the optical axis direction.
  An adjustment tool 60 is used for position adjustment. The adjusting tool 60 has an eccentric pin 61 at the tip. When the eccentric pin 61 is inserted into the long hole 13a and the adjustment tool 60 is swung, the coupling lens 13 can be displaced back and forth in the optical axis direction, and this is used to adjust the position in the optical axis direction. be able to. Of course, an adjustment pin as shown in FIG. 6 is inserted into the long hole 13a to adjust the position in or around the optical axis.LikeIt is also possible to make it.
  In the case of the coupling lens 18 shown in FIG. 5, it will be easily understood that the position adjustment in the optical axis direction can be performed by the same method as shown in FIG.
  The coupling lens 15 shown in FIG. 8 is the same as that shown in FIG. 3C, and a long hole 15a for position adjustment is formed on the peripheral surface portion with the longitudinal direction as the optical axis direction. Yes. In this example, the optical action of the coupling lens 13 is not symmetric with respect to the optical axis, and the position adjustment is performed around the optical axis. The coupling lens 15 is held by a holding portion of the housing similar to the above, and can be rotated around the optical axis while maintaining the optical axis direction.
  An adjustment tool 60 is used for position adjustment. When the eccentric pin 61 is inserted into the long hole 15a and the adjusting tool 60 is swung, the coupling lens 15 can be swung oscillating around the optical axis, and this is used to adjust the position around the optical axis. It can be performed. Of course, an adjustment pin as shown in FIG. 6 is inserted into the long hole 13a to adjust the position in or around the optical axis.LikeIt is also possible to make it.
  In the case of an anamorphic coupling lens, it is necessary to adjust the position in the optical axis direction and around the optical axis. In such a case, a long hole long in the optical axis direction, such as the long hole 13a and the long hole 15a, A long hole that is long in the direction perpendicular to the optical axis, or a long hole or hole that is long in the optical axis direction, and a groove that makes one round of the peripheral surface may be formed in the same coupling lens. From the viewpoint of preventing the deterioration of wavefront aberration caused by stress in the vicinity of the holes and the long holes, it is preferable to make the number of holes and the long holes plural and arrange them symmetrically on the optical axis.
[0014]
  The coupling lens shown in FIG. 9 is a coupling lens that couples a divergent light beam from a semiconductor laser. The coupling lens has an optical axis symmetric lens portion 21 having an optically symmetric optical action, and is orthogonal to the optical axis. The anamorphic lens portion 20 has different optical actions in two directions orthogonal to each other, and the optical axis symmetrical lens portion 21 and the anamorphic lens portion 20 are configured to realize an anamorphic optical action.
  As shown, both the optical axis symmetric lens portion 21 and the anamorphic lens portion 20 have a lens thickness substantially equal to or larger than the effective diameter of the lens.
  The optical axis symmetric lens portion 21 is provided with a groove 21a for position adjustment in the optical axis direction at a depth that does not shield the effective light beam, and the anamorphic lens portion 20 has an optical axis on the peripheral surface. One or more holes 20a (one in this example, but plural in this example) for adjusting the surrounding position are provided at a depth that does not shield the effective light beam. The eccentric pin 61B of the adjusting tool 60B is inserted into the groove 21a, and the position of the optical axis symmetrical lens portion 21 is adjusted in the optical axis direction by swinging the adjusting tool 60B. The eccentric pin 61A of the adjusting tool 60A is inserted into the groove 21a. The position of the optical axis symmetrical lens portion 21 around the optical axis can be adjusted by swinging the adjustment tool 60A.
[0015]
【Example】
  Two specific examples will be given below.
  Example 1
  In the coupling lens of Example 1, the optical action is a “collimating action that is symmetric with respect to the optical axis” (claims 9 and 11). This coupling lens has an effective diameter of 5 mm, a lens outer diameter of 6 mm, and a wall thickness of 6.5 mm. That is, the wall thickness is approximately equal to the effective diameter of the lens (Claim 1).
  Each surface is a “coaxial aspheric surface”, where the optical axis direction is the z-axis, the direction orthogonal to the optical axis (the lens radial direction) is the y-direction, the paraxial radius of curvature is R, the conic constant is K, and the higher order Aspheric coefficient is A_Four, A₆, A₈, A_Ten,. . . The coaxial aspheric formula, known as:
  z = (y²/ R) / [1 + √ {1- (1 + K) (y / R)²}] A_Foury^Four+ A₆y⁶+ A₈y⁸+ A_Teny^Ten+. . . .
It is represented by The lens data is as follows.
[0016]
Wavelength: Refractive index for light of 635 nm: N = 1.87007
Center wall thickness: 6.5mm

In the above, for example, “E-6” is “10 ~⁶"Means.
Wavefront aberrations with respect to angle of view (unit: degree): 0, 0.33, 0.67, and 1.00 when a parallel light beam is incident on this coupling lens are as follows, and the performance is good.

This coupling lens is formed by injection molding, and a position adjusting groove is formed with a width of 1.5 mm and a depth of 1.5 mm, which is used as a coupling lens 102 of an optical pickup as shown in FIG. By adjusting the position in the optical axis direction with the adjusting tool 60B shown, the position can be adjusted very easily with high accuracy, the collimating action as designed can be realized, and an optical pickup with good performance can be realized.
FIG. 10 shows the collimating action of the coupling lens of Example 1. Reference numeral 70 denotes a coupling lens, reference numeral 80 denotes a light emitting portion of the semiconductor laser, and reference numeral 90 denotes a cover glass of the semiconductor laser package.
[0017]
  Example 2
  In the coupling lens of Example 2, the optical action is “collimating action and beam shaping action” (Claims 9 and 10). That is, this coupling lens has different focal lengths in the x and y directions perpendicular to the optical axis and perpendicular to each other, the focal length in the x direction: fx = 12.5 mm, and the focal length in the y direction: fy = 30 mm, collimating the divergent light beam from the semiconductor laser into a parallel light beam, and “beam shaping” the cross-sectional shape of the light beam into a substantially circular shape (Claim 11). Beam shaping magnification: fy / fx = 2.4 times.
  This coupling lens has an effective diameter of 5 mm, a lens outer diameter of 6 mm, and a wall thickness of 10.2797995 mm. That is, the wall thickness is larger than the effective diameter of the lens (Claim 1).
  Each surface is an “aspherical surface”, and the paraxial curvature in the XZ plane is R when the optical axis direction is the z axis, the two directions orthogonal to the optical axis are the X and Y directions._X, R is the paraxial curvature in the YZ plane_Y, The conic constant in the XZ plane is K_X, The conic constant in the YZ plane is K_YThe rotationally symmetric components of the 4th, 6th, 8th, and 10th order deformation variables from the cone shape are AR, BR, CR, DR, and the non-rotationally symmetric components are AP, BP, CP, DP, respectively. formula:
  Z = (R_XX²+ R_YY²) / [1 + √ {1- (1 + K_X) R_X ²X²-(1 + K_Y) R_Y ²Y²}]
    + AR [(1-AP) X²+ (1 + AP) Y²]²+ BR [(1-BP) X²+ (1 + BP) Y²]^Three
    + CR [(1-CP) X²+ (1 + CP) Y²]^Four+ DR [(1-DP) X²+ (1 + DP) Y²]^Five
It is represented by Lens data (For the above "Paraxial curvature", its reciprocal (1 / R_X, 1 / R_YThe “paraxial radius of curvature”) is as follows:
[0018]
Wavelength: Refractive index for light of 635 nm: N = 1.580892
Center wall thickness: 10.279495mm

The wavefront aberration with respect to the angle of view (unit: degree): 0, 0.5, 1.00 (incidence pupil diameter: 4.0 mm) is as follows.

This lens is used as the coupling lens 102 of the optical pickup shown in FIG. 1, and both surfaces of the objective lens are coaxial aspheric surfaces (represented by the above-described coaxial aspherical equation) and have the following data: Combined.
Wavelength: Refractive index for light of 635 nm: N = 1.726592
Center wall thickness: 1.5mm

FIG. 11 shows the XZ cross section and FIG. 12 shows the YZ cross section when the focused light beam by the objective lens is condensed on the recording surface of the DVD having a substrate thickness of 0.6 mm.
Reference numeral 71 denotes a coupling lens, reference numeral 73 denotes an objective lens, and reference numeral 75 denotes a DVD substrate. For a light source having a wavelength of λ = 635 nm, the wavefront aberration at the light spot on the recording surface is 0.003λ on the axis, which is sufficient for obtaining a diffraction-limited light spot.
This coupling lens is formed by injection molding, and a groove for position adjustment is formed so as to make one round of the circumferential surface with a width: 1.5 mm and a depth: 1.5 mm, as shown in FIG. Such a long hole 14a that is long in the optical axis direction is formed with a width of 1.5 mm and a depth of 1.5 mm, and the position of the optical axis direction is adjusted by the adjusting tool 60B shown in FIG. By adjusting the position of the surroundings, it was possible to adjust the position very easily and accurately, and it was possible to realize the collimating action and beam shaping action as designed, realizing an optical pickup with good performance.
[0019]
【The invention's effect】
As described above, according to the present invention, a novel coupling lens and optical pickup can be realized. Since the coupling lens of the present invention has a hole or groove for position adjustment on the lens peripheral surface, position adjustment around and / or around the optical axis can be realized very easily and reliably without using a lens cell. The design coupling action for the semiconductor laser can be realized. The optical pickup of the present invention can realize good optical characteristics in design by using the coupling lens.
[Brief description of the drawings]
FIG. 1 is a diagram for explaining one embodiment of an optical pickup according to the present invention.
FIG. 2 is a diagram showing three examples of embodiments of the coupling lens of the present invention.
FIG. 3 is a view showing three examples of another embodiment of the coupling lens of the present invention.
FIG. 4 is a view showing two examples of another embodiment of the coupling lens of the present invention.
FIG. 5 is a diagram showing another embodiment of the coupling lens of the present invention.
6 is a diagram for explaining a method for adjusting the position of the coupling lens shown in FIG. 2A in the optical axis direction; FIG.
7 is a diagram for explaining a method of adjusting the position of the coupling lens shown in FIG. 3A in the optical axis direction.
FIG. 8 is a diagram illustrating a method for adjusting the position of the coupling lens shown in FIG. 3C around the optical axis.
FIG. 9Claim 1 2 DescriptionIt is a figure for demonstrating this coupling lens and its position adjustment method.
10 is a diagram illustrating the lens action of the coupling lens of Example 1. FIG.
11 is a diagram for explaining a lens action in an XZ plane of a coupling lens of Example 2. FIG.
12 is a diagram for explaining the lens action in the YZ plane of the coupling lens of Example 2. FIG.
[Explanation of symbols]
10 Coupling lens
10a Hole for position adjustment

Claims (13)

In an optical pickup that couples a divergent light beam from a semiconductor laser by a coupling lens, condenses it on a recording surface of an optical recording medium by an objective lens, and performs one or more of recording / reproducing / erasing information from the semiconductor laser. A coupling lens for coupling a divergent light beam of
Cylindrical shape that has a thickness approximately equal to or larger than the effective diameter of the lens, and can be adjusted in the optical axis direction and / or around the optical axis without using a lens cell in the housing holding portion. The peripheral surface is directly held,
To the circumferential surface portion which is sandwiched exit-side surface and the incident side surface, one or a hole for adjusting the position, the coupling lens for the optical pickup being characterized in that provided in the depth not shield the effective light beam. The coupling lens according to claim 1,
A coupling lens, wherein the position adjusting hole is a long hole. The coupling lens according to claim 2,
A coupling lens, wherein the longitudinal direction of the long hole for position adjustment is a direction parallel to the optical axis. The coupling lens according to claim 2,
A coupling lens, wherein the longitudinal direction of the long hole for position adjustment is a direction perpendicular to the optical axis. In the coupling lens of any one of Claims 1-4,
A coupling lens comprising a plurality of position adjusting holes, wherein the plurality of holes are formed symmetrically about the optical axis. In an optical pickup that couples a divergent light beam from a semiconductor laser by a coupling lens, condenses it on a recording surface of an optical recording medium by an objective lens, and performs one or more of recording / reproducing / erasing information from the semiconductor laser. A coupling lens for coupling a divergent light beam of
Cylindrical shape that has a thickness approximately equal to or larger than the effective diameter of the lens, and can be adjusted in the optical axis direction and / or around the optical axis without using a lens cell in the housing holding portion. The peripheral surface is directly held,
To the circumferential surface portion which is sandwiched exit-side surface and the incident side surface, a groove for adjusting a position, a depth that does not shield the effective light beam, a coupling lens, characterized in that provided in one revolution of the circumferential surface portion. The coupling lens according to any one of claims 1 to 6,
  A coupling lens formed by a mold. The coupling lens according to any one of claims 1 to 7,
  A coupling lens characterized in that the optical action is symmetric with respect to the optical axis. The coupling lens according to any one of claims 1 to 7,
  A coupling lens having different focal lengths in two directions orthogonal to the optical axis and orthogonal to each other. The coupling lens according to claim 8, wherein
  A coupling lens, wherein the optical action of the lens is a collimating action. The coupling lens according to claim 9, wherein
  A coupling lens having different focal lengths in two directions orthogonal to each other so that a divergent light beam from a semiconductor laser is converted into a parallel light beam whose cross-sectional shape is nearly circular. In an optical pickup that couples a divergent light beam from a semiconductor laser by a coupling lens, condenses it on a recording surface of an optical recording medium by an objective lens, and performs one or more of recording / reproducing / erasing information from the semiconductor laser. A coupling lens for coupling a divergent light beam of
  An optical axis symmetric lens portion having an optical action that is optically symmetric and an anamorphic lens portion having different optical actions in two directions that are orthogonal to the optical axis and orthogonal to each other,
  The optical axis symmetrical lens portion and the anamorphic lens portion are configured to realize an anamorphic optical action,
The optical axis symmetric lens portion and the anamorphic lens portion have a thickness substantially equal to or larger than the effective diameter of the lens, and without using a lens cell in the holding portion of the housing, And / or the cylindrical peripheral surface is directly held, adjustable around the optical axis,
The optical axis symmetric lens portion is provided with one or more holes for position adjustment in the optical axis direction or grooves for position adjustment in the optical axis direction at a depth that does not block the effective light beam on the peripheral surface thereof, The above-mentioned anamorphic lens portion is provided with at least one hole for adjusting the position around the optical axis on the peripheral surface thereof at a depth that does not block the effective light beam. Ring lens. In an optical pickup that couples a divergent light beam from a semiconductor laser by a coupling lens, condenses it on a recording surface of an optical recording medium by an objective lens, and performs one or more of recording, reproducing, and erasing information.
  An optical pickup using the coupling lens according to any one of claims 1 to 12.

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