JPH07333498A - Lens for correcting chromatic aberration and optical head formed by using the same - Google Patents
Lens for correcting chromatic aberration and optical head formed by using the sameInfo
- Publication number
- JPH07333498A JPH07333498A JP12352294A JP12352294A JPH07333498A JP H07333498 A JPH07333498 A JP H07333498A JP 12352294 A JP12352294 A JP 12352294A JP 12352294 A JP12352294 A JP 12352294A JP H07333498 A JPH07333498 A JP H07333498A
- Authority
- JP
- Japan
- Prior art keywords
- lens
- chromatic aberration
- aberration correction
- objective lens
- curvature
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Abstract
Description
【０００１】[0001]
【産業上の利用分野】本発明は、光ディスク装置等の光
学系に関し、より詳細には光を記録媒体上に集光し情報
の記憶或いは再生を行なう装置の光ヘッドに適用しうる
色収差補正用レンズ及びそれを用いた光ヘッドに関す
る。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical system such as an optical disk device, and more particularly, for chromatic aberration correction applicable to an optical head of an apparatus for condensing light on a recording medium and storing or reproducing information. The present invention relates to a lens and an optical head using the same.
【０００２】[0002]
【従来の技術】光ディスク装置等の光学系、たとえば光
を記録媒体上に集光し情報の記憶或いは再生を行なう装
置の光ヘッドには、色収差補正用レンズが使われてい
る。従来の光ディスク装置の光学系の例を図６に示す。
光源である半導体レーザ２８から出射された発散光束２
９はコリメートレンズ３０により略平行光束３１にな
る。略平行光束３１はビームスプリッタ３２を透過し、
対物レンズ３３により情報記録媒体３５上に集光され
る。情報記録媒体３５上の情報により変調を受けた反射
光３４は、対物レンズ３３により略平行光束となり、ビ
ームスプリッタ３２により反射し信号検出用光学系３６
を経て受光素子３７にいたる。このような光学系におい
て、対物レンズ３３は情報記録媒体の情報記録面に正確
に集光するようにフォーカスサーボがかけられており、
光軸方向に移動できるようになっている。2. Description of the Related Art A chromatic aberration correcting lens is used in an optical system of an optical disk device or the like, for example, an optical head of a device for condensing light on a recording medium to store or reproduce information. FIG. 6 shows an example of an optical system of a conventional optical disk device.
Divergence beam 2 emitted from semiconductor laser 28 which is a light source
The collimating lens 30 forms a substantially parallel light beam 9 at 9. The substantially parallel light beam 31 passes through the beam splitter 32,
It is condensed on the information recording medium 35 by the objective lens 33. The reflected light 34 modulated by the information on the information recording medium 35 becomes a substantially parallel light flux by the objective lens 33, is reflected by the beam splitter 32, and is reflected by the signal detection optical system 36.
To reach the light receiving element 37. In such an optical system, the objective lens 33 is provided with a focus servo so as to accurately focus the light on the information recording surface of the information recording medium.
It can be moved along the optical axis.
【０００３】前述の光学系において、光源の波長が変化
すると、光学系の色収差が十分に補正されていない状態
では対物レンズの集光位置が色収差のためずれてしま
う。光源の波長変動が緩やかな場合には対物レンズのア
クチュエータによるオートフォーカス機能により焦点位
置を補正できるが、例えば記録時と再生時とで光源の出
力を変化させるような場合には急激に波長がシフトする
ため十分に追随できなくなる。このため、記録と再生を
行なう光ヘッド用の光学系では光源の波長変動があって
も焦点位置のずれが小さくなるように色収差補正を十分
に行なう必要がある。対物レンズ自体を色収差補正した
光学系は、例えば特開昭６３−１０１１８号公報、特開
平３−１５５５１５号公報等に提案されている。In the above-mentioned optical system, when the wavelength of the light source changes, the condensing position of the objective lens shifts due to chromatic aberration when the chromatic aberration of the optical system is not sufficiently corrected. When the wavelength fluctuation of the light source is gentle, the focus position can be corrected by the autofocus function by the actuator of the objective lens, but for example, when the output of the light source is changed during recording and reproduction, the wavelength shifts abruptly. Therefore, it cannot follow up sufficiently. For this reason, in the optical system for the optical head for recording and reproducing, it is necessary to sufficiently perform the chromatic aberration correction so that the shift of the focal position becomes small even if the wavelength of the light source varies. An optical system in which the objective lens itself is corrected for chromatic aberration is proposed in, for example, Japanese Patent Application Laid-Open No. 63-10118 and Japanese Patent Application Laid-Open No. 3-155515.
【０００４】これらに対し、特開平３−１５５５１４号
公報には、コリメートレンズと、対物レンズの間に色収
差の補正を目的とする接合レンズを配置する光学系が提
案されている。これは、対物レンズの駆動系にも負担を
かけることなく全光学系の色収差を低減することが可能
であり、有効な手法の一つである。On the other hand, Japanese Patent Laid-Open No. 3-155514 proposes an optical system in which a collimating lens and a cemented lens for the purpose of correcting chromatic aberration are arranged between the objective lenses. This is one of the effective methods because it is possible to reduce the chromatic aberration of the entire optical system without imposing a burden on the drive system of the objective lens.
【０００５】[0005]
【発明が解決しようとする課題】しかしながら、前記従
来の特開昭６３−１０１１８号公報、特開平３−１５５
５１５号公報等に提案されている発明は、いずれも３枚
構成の組レンズであり、重量が大きくなるという問題が
あった。However, the above-mentioned conventional Japanese Patent Laid-Open Nos. 63-10118 and 3-155 are known.
The inventions proposed in Japanese Patent No. 515, etc. are all three-lens construction lenses and have a problem that the weight becomes large.
【０００６】また前記特開平３−１５５５１４号公報に
提案されている光学系は、２枚貼り合わせの色収差補正
用接合レンズを１つ光学系に挿入したときの軸上色収差
の補正量が少なく、より多くの色収差補正が必要な光学
系においては色収差補正レンズを複数個挿入せねばなら
ず、光学系が複雑になってしまうという問題があった。
さらに、３枚貼り合わせの色収差補正レンズは光学的な
性能においては優れるが、コストアップの要因となる。The optical system proposed in the above-mentioned Japanese Patent Laid-Open No. 3-155514 has a small amount of correction of axial chromatic aberration when one cemented lens for chromatic aberration correction of two cemented lenses is inserted into one optical system. In an optical system that requires more chromatic aberration correction, a plurality of chromatic aberration correction lenses must be inserted, which causes a problem that the optical system becomes complicated.
Further, although the chromatic aberration correction lens formed by laminating three pieces is excellent in optical performance, it causes a cost increase.
【０００７】本発明は、従来の問題を解決するため、２
枚組のレンズ１つで十分な色収差補正ができる色収差補
正用レンズ及びそれを用いた光ヘッドを提供することを
目的とする。The present invention solves the conventional problems by
An object of the present invention is to provide a chromatic aberration correction lens capable of performing sufficient chromatic aberration correction with one lens in a set and an optical head using the same.
【０００８】[0008]
【課題を解決するための手段】前記課題を解決するた
め、本発明の色収差補正レンズは、光ヘッド用の対物レ
ンズと組み合わせて使用する色収差補正用のレンズであ
って、前記色収差補正レンズは、１枚の正レンズと１枚
の負レンズとを貼り合わせた接合レンズであり、かつ前
記色収差補正レンズの光源側の面の曲率半径をｒ1 、出
射側の面の曲率半径をｒ3 、対物レンズの焦点距離をｆ
o とするとき、前記式（数１）及び（数２）を満足する
ことを特徴とする。In order to solve the above problems, a chromatic aberration correction lens of the present invention is a chromatic aberration correction lens used in combination with an objective lens for an optical head, and the chromatic aberration correction lens is It is a cemented lens in which one positive lens and one negative lens are bonded together, and the radius of curvature of the surface on the light source side of the chromatic aberration correction lens is r 1 , the radius of curvature of the surface on the exit side is r 3 , and the objective F is the focal length of the lens
When o , it is characterized by satisfying the expressions (Equation 1) and (Equation 2).
【０００９】前記構成においては、色収差補正レンズの
光源側の面の曲率半径ｒ1 と、出射側の面の曲率半径ｒ
3 と、対物レンズの焦点距離ｆo の積が前記式（数３）
を満足することが好ましい。In the above structure, the radius of curvature r 1 of the surface on the light source side of the chromatic aberration correction lens and the radius of curvature r of the surface on the exit side are
3, the product of the focal length f o of the objective lens is the formula (Equation 3)
It is preferable to satisfy
【００１０】また前記構成においては、１枚の正レンズ
と１枚の負レンズを貼り合わせた接合レンズであって、
前記正レンズと前記負レンズのうち少なくとも１枚、望
ましくは２枚のレンズがプレス成形可能な硝材で形成さ
れていることが好ましい。Further, in the above-mentioned structure, a cemented lens in which one positive lens and one negative lens are cemented together,
It is preferable that at least one lens, preferably two lenses, of the positive lens and the negative lens are made of a press-moldable glass material.
【００１１】次に本発明の光ヘッドは、光源と、光源か
らの光束を分離する光束分離手段と、光束を情報記録媒
体上に集光する手段と、前記情報記録媒体からの反射ま
たは透過光を受光する受光手段を有する光ヘッドにおい
て、前記光源と前記集光する手段との間に前記色収差補
正レンズを有することを特徴とする。Next, the optical head of the present invention comprises a light source, a light beam separating means for separating a light beam from the light source, a means for condensing the light beam on an information recording medium, and a reflected or transmitted light from the information recording medium. In the optical head having a light receiving means for receiving the light, the chromatic aberration correction lens is provided between the light source and the light collecting means.
【００１２】[0012]
【作用】前記した本発明の色収差補正レンズの構成によ
れば、光ヘッド用の対物レンズと組み合わせて使用する
色収差補正用のレンズであって、前記色収差補正レンズ
は、１枚の正レンズと１枚の負レンズとを貼り合わせた
接合レンズであり、かつ前記色収差補正レンズの光源側
の面の曲率半径をｒ1 、出射側の面の曲率半径をｒ3 、
対物レンズの焦点距離をｆo とするとき、前記式（数
１）及び（数２）を満足することにより、２枚組のレン
ズ１つで十分な色収差補正ができる色収差補正用レンズ
を実現できる。そして、光源の波長変動による対物レン
ズの軸上色収差を良好に補正しながら、対物レンズの光
軸方向への移動により色収差補正レンズと対物レンズの
間隔が変動した場合でも、波面収差の変動が抑えられて
いる。すなわち、前記式（数１）は色収差補正レンズの
入射面、及び出射面の曲率半径ｒ1 およびｒ3 を規定す
る式である。前記式（数１）の下限は色収差補正レンズ
の入射面と出射面の曲率半径がいずれも正、或いはいず
れも負であるための条件である。色収差補正レンズの入
射面と出射面のうちいずれかが正であり、残りが負であ
る場合には色収差補正レンズの持つ正または負のパワー
が大きすぎ、色収差補正レンズと対物レンズの間の距離
が変わったときの収差の変動が大きくなってしまう。ま
た前記式（数１）の上限を越えた場合には、入射面及び
出射面の曲率が大きくなり、パワーが小さくなる。この
場合、色収差補正レンズは接合面のみにパワーを持つこ
ととなり、良好に収差を除去できる硝材の組合せが限定
されてしまう。また、前記式（数２）の上限或いは下限
を越えた場合には、色収差補正レンズの入射面と出射面
の曲率半径が異なりすぎ、レンズ単体での収差除去が困
難になる。According to the structure of the chromatic aberration correcting lens of the present invention described above, the chromatic aberration correcting lens is used in combination with the objective lens for the optical head, and the chromatic aberration correcting lens includes one positive lens and one positive lens. A cemented lens in which a negative lens is cemented together, and the radius of curvature of the light source side surface of the chromatic aberration correction lens is r 1 , the radius of curvature of the exit side surface is r 3 ,
When the focal length of the objective lens is f o , by satisfying the above equations (Equation 1) and (Equation 2), it is possible to realize a chromatic aberration correction lens capable of performing sufficient chromatic aberration correction with one lens of two lenses. . Further, while properly correcting the axial chromatic aberration of the objective lens due to the wavelength variation of the light source, even if the distance between the chromatic aberration correction lens and the objective lens varies due to the movement of the objective lens in the optical axis direction, the variation of the wavefront aberration is suppressed. Has been. That is, the equation (Equation 1) is an equation that defines the radii of curvature r 1 and r 3 of the entrance surface and the exit surface of the chromatic aberration correction lens. The lower limit of the equation (Equation 1) is a condition that the radii of curvature of the entrance surface and the exit surface of the chromatic aberration correction lens are both positive or negative. If either the entrance surface or the exit surface of the chromatic aberration correction lens is positive and the rest is negative, the positive or negative power of the chromatic aberration correction lens is too large and the distance between the chromatic aberration correction lens and the objective lens is large. The change in aberration becomes large when the value changes. If the upper limit of the above formula (Equation 1) is exceeded, the curvature of the entrance surface and the exit surface becomes large and the power becomes small. In this case, the chromatic aberration correction lens has power only on the cemented surface, and the combination of glass materials that can satisfactorily remove aberration is limited. If the upper limit or the lower limit of the equation (Equation 2) is exceeded, the radii of curvature of the entrance surface and the exit surface of the chromatic aberration correction lens are too different, and it becomes difficult to remove the aberration by the lens alone.
【００１３】また前記において、色収差補正レンズの光
源側の面の曲率半径ｒ1 と、出射側の面の曲率半径ｒ3
と、対物レンズの焦点距離ｆo の積が前記式（数３）を
満足するという本発明の好ましい構成によれば、さらに
十分な色収差補正ができる。Further, in the above description, the radius of curvature r 1 of the surface on the light source side of the chromatic aberration correction lens and the radius of curvature r 3 of the surface on the emission side of the lens.
When, according to a preferred configuration of the present invention that the product of the focal length f o of the objective lens satisfies the formula (number 3), it is more fully correct chromatic aberration.
【００１４】また前記において、１枚の正レンズと１枚
の負レンズを貼り合わせた接合レンズであって、前記正
レンズと前記負レンズのうち少なくとも１枚、望ましく
は２枚のレンズがプレス成形可能な硝材で形成されてい
るという本発明の好ましい構成によれば、さらにコスト
を安価に作成できる。前記において、プレス成形可能な
硝材とは、たとえばガラスまたは樹脂などの材料であ
る。Further, in the above, in a cemented lens in which one positive lens and one negative lens are cemented together, at least one, preferably two lenses of the positive lens and the negative lens are press-molded. According to the preferable configuration of the present invention in which it is made of a possible glass material, the cost can be further reduced. In the above description, the press-moldable glass material is a material such as glass or resin.
【００１５】次に本発明の光ヘッドの構成によれば、光
源と、光源からの光束を分離する光束分離手段と、光束
を情報記録媒体上に集光する手段と、前記情報記録媒体
からの反射または透過光を受光する受光手段を有する光
ヘッドにおいて、前記光源と前記集光する手段との間に
前記色収差補正レンズを有することにより、２枚組のレ
ンズ１つで十分な色収差補正ができる光ヘッドを安価に
製造できる。Next, according to the structure of the optical head of the present invention, the light source, the light beam separating means for separating the light beam from the light source, the means for condensing the light beam on the information recording medium, and the light beam from the information recording medium. In the optical head having the light receiving means for receiving the reflected or transmitted light, the chromatic aberration correcting lens is provided between the light source and the means for condensing the light, so that the chromatic aberration can be sufficiently corrected by one lens of two sets. The optical head can be manufactured at low cost.
【００１６】プレス工法によりレンズを成形する場合に
は、小さな曲率であっても一旦金型が加工できれば、後
は安定して製造することができる。そのため色収差補正
レンズの接合面の曲率半径を小さくすることも可能であ
り、設計の自由度が拡がる。When the lens is molded by the press method, even if the lens has a small curvature, once the mold can be processed, the lens can be stably manufactured thereafter. Therefore, it is possible to reduce the radius of curvature of the cemented surface of the chromatic aberration correction lens, and the degree of freedom in design is expanded.
【００１７】[0017]
【実施例】以下に実施例をあげて本発明をさらに具体的
に説明する。各実施例において、対物レンズ、及び情報
記録媒体の保護樹脂は同じものを使用することとし、対
物レンズの、焦点距離は３ｍｍ、開口数は０．５５、光
学系の設計中心波長は６８０ｎｍのものを用いた。ま
た、レンズデータにおいては、面番号１から３が色収差
補正レンズであって、面番号４から５が対物レンズ、面
番号６から７が情報記録媒体の保護樹脂である。曲率半
径をｒ、面間隔をｄ、波長６８０ｎｍ、６７０ｎｍ、６
９０ｎｍにおける硝材の屈折率をそれぞれ、ｎ（６８
０）、ｎ（６７０）、ｎ（６９０）とし、前記対物レン
ズ及び前記情報記録媒体の各データを表１に示す。な
お、ｒとｄの単位はｍｍである。EXAMPLES The present invention will be described in more detail with reference to the following examples. In each embodiment, the objective lens and the protective resin of the information recording medium are the same, and the objective lens has a focal length of 3 mm, a numerical aperture of 0.55, and a design center wavelength of the optical system of 680 nm. Was used. In the lens data, surface numbers 1 to 3 are chromatic aberration correction lenses, surface numbers 4 to 5 are objective lenses, and surface numbers 6 to 7 are protective resins for the information recording medium. Radius of curvature is r, surface spacing is d, wavelengths are 680 nm, 670 nm, 6
The refractive index of the glass material at 90 nm is n (68
0), n (670), n (690), and Table 1 shows the respective data of the objective lens and the information recording medium. The unit of r and d is mm.
【００１８】[0018]
【表１】 [Table 1]
【００１９】また、本対物レンズは両面とも非球面であ
って、前記非球面上の任意の点から前記非球面の頂点に
おける接平面までの距離（サグ量）をＸ、前記任意の点
から光軸までの距離をｈ、第ｋ面の曲率半径をｒk 、第
ｋ面の頂点近傍での円錐定数をＣk 、第ｋ面の４次、６
次、８次、１０次の非球面定数をそれぞれＤk 、Ｅk、
Ｆk 、Ｇk とした時に前記非球面の形状が、下記式（数
４）で表される。Further, the objective lens has aspherical surfaces on both sides, and the distance (sag amount) from an arbitrary point on the aspherical surface to a tangent plane at the apex of the aspherical surface is X, and light is emitted from the arbitrary point. The distance to the axis is h, the radius of curvature of the k-th surface is r k , the conic constant near the apex of the k-th surface is C k , the fourth-order of the k-th surface is 6
The second, eighth, and tenth aspherical constants are D k , E k , and
The shape of the aspherical surface when F k and G k are expressed by the following equation (Equation 4).
【００２０】[0020]
【数４】 [Equation 4]
【００２１】前記式（数４）の係数は表２に示す。Table 2 shows the coefficients of the above equation (Equation 4).
【００２２】[0022]
【表２】 [Table 2]
【００２３】本対物レンズを単独で用いた場合の軸上波
面収差は２．９ｍλであり、６８０ｎｍ近傍における軸
上色収差は０．１２８μｍ／ｎｍである。ここで、６８
０ｎｍ近傍における軸上色収差とは、光源の波長が６８
０ｎｍ近傍で１ｎｍ変動したときの作動距離（ｄ5 ）の
変化量であって、６７０ｎｍでの作動距離をＷ670 、６
９０ｎｍでの作動距離をＷ690 としたとき、下記式（数
５）で表される。When this objective lens is used alone, the axial wavefront aberration is 2.9 mλ and the axial chromatic aberration near 680 nm is 0.128 μm / nm. Where 68
On-axis chromatic aberration in the vicinity of 0 nm means that the wavelength of the light source is 68
It is the amount of change of the working distance (d 5 ) when it varies by 1 nm in the vicinity of 0 nm, and the working distance at 670 nm is W 670,6
When the working distance at 90 nm is W 690 , it is expressed by the following formula (Equation 5).
【００２４】[0024]
【数５】 [Equation 5]
【００２５】（実施例１）図１は本実施例の光学系の光
路図である。図１において１が色収差補正レンズであ
り、２が対物レンズ、３が情報記録媒体の保護樹脂であ
る。図中ｄ1 〜ｄ6、ｒ1 〜ｒ6 はそれぞれ面間隔、頂
点曲率半径である。本実施例の色収差補正レンズの曲率
半径、面間隔及び硝材の各波長における屈折率を表３に
示す。(Embodiment 1) FIG. 1 is an optical path diagram of an optical system of this embodiment. In FIG. 1, 1 is a chromatic aberration correction lens, 2 is an objective lens, and 3 is a protective resin for an information recording medium. In the drawing, d 1 to d 6 and r 1 to r 6 are the surface spacing and the vertex curvature radius, respectively. Table 3 shows the radius of curvature, the surface spacing, and the refractive index of the glass material at each wavelength of the chromatic aberration correction lens of this embodiment.
【００２６】[0026]
【表３】 [Table 3]
【００２７】本実施例の色収差補正レンズを前記対物レ
ンズと共に用いた場合、作動距離は、１．２７７２１３
９５ｍｍであって、６８０ｎｍ近傍における軸上色収差
は、４．１９×１０-4μｍ／ｎｍであり、６８０ｎｍ近
傍で、ほぼ完全に軸上色収差が除去されている。また、
軸上波面収差は２．３８ｍλである。色収差補正レンズ
と、対物レンズとの面間隔（ｄ3 ：表中で＊印）は対物
レンズがフォーカシングのため光軸方向に移動した場合
に変化するが、ｄ3 が３．０ｍｍに変化した場合、本光
学系全体の軸上波面収差は２．３６ｍλであり、８．０
ｍｍに変化した場合は、２．４２ｍλである。このよう
に、本発明の色収差補正レンズを用いた光学系では、対
物レンズが単独でフォーカシングのために光軸方向に移
動しても収差の変動がほとんど生じない。When the chromatic aberration correction lens of this embodiment is used together with the objective lens, the working distance is 1.277213.
The axial chromatic aberration in the vicinity of 680 nm is 4.19 × 10 −4 μm / nm at 95 mm, and the axial chromatic aberration is almost completely removed in the vicinity of 680 nm. Also,
The axial wavefront aberration is 2.38 mλ. And chromatic aberration correction lens, the surface distance between the objective lens (d 3: * mark in the table) is changed when the objective lens is moved in the optical axis direction for focusing, if d 3 is changed to 3.0mm , The axial wavefront aberration of the entire optical system is 2.36 mλ, which is 8.0
When it is changed to mm, it is 2.42 mλ. As described above, in the optical system using the chromatic aberration correction lens of the present invention, the aberration hardly changes even if the objective lens alone moves in the optical axis direction for focusing.
【００２８】（実施例２）図２は、第２の実施例の光学
系の光路図である。図２の中で、５が本発明の色収差補
正レンズ、６が対物レンズ、７が情報記録媒体の保護樹
脂、８は光源からの光束である。本実施例は、第１の実
施例と同様の色収差補正レンズを他の硝材を用いて構成
した例である。本実施例の色収差補正レンズの曲率半
径、面間隔、硝材の各波長における屈折率を表４に示
す。(Embodiment 2) FIG. 2 is an optical path diagram of the optical system of the second embodiment. In FIG. 2, 5 is a chromatic aberration correction lens of the present invention, 6 is an objective lens, 7 is a protective resin for an information recording medium, and 8 is a light beam from a light source. The present embodiment is an example in which the same chromatic aberration correction lens as that of the first embodiment is configured by using another glass material. Table 4 shows the radius of curvature, the surface spacing, and the refractive index of the glass material at each wavelength in the chromatic aberration correction lens of this example.
【００２９】[0029]
【表４】 [Table 4]
【００３０】本実施例の色収差補正レンズを前記対物レ
ンズと共に用いた場合、作動距離は、１．２６０２７１
４３ｍｍであって、６８０ｎｍ近傍における軸上色収差
は、−２．７×１０-4μｍ／ｎｍとなり、軸上色収差が
良好に除去されている。さらに、軸上波面収差は４．８
ｍλである。色収差補正レンズと、対物レンズとの面間
隔（ｄ3 ：表４中で＊印）が３．０ｍｍに変化した場合
の軸上波面収差は４．１ｍλであり、８．０ｍｍに変化
した場合は、５．８ｍλである。When the chromatic aberration correction lens of this embodiment is used together with the objective lens, the working distance is 1.260271.
The axial chromatic aberration is 43 mm, and the axial chromatic aberration in the vicinity of 680 nm is −2.7 × 10 −4 μm / nm, and the axial chromatic aberration is well removed. Further, the axial wavefront aberration is 4.8.
mλ. The on-axis wavefront aberration is 4.1 mλ when the surface distance between the chromatic aberration correction lens and the objective lens (d 3 : mark in Table 4) changes to 3.0 mm, and when it changes to 8.0 mm, It is 5.8 mλ.
【００３１】（実施例３）図３は、第３の実施例の光学
系の光路図である。図３の中で、９が本発明の色収差補
正レンズ、１０が対物レンズ、１１が情報記録媒体の保
護樹脂、１２は光源からの光束である。第３の実施例の
色収差補正レンズの曲率半径、面間隔、硝材の各波長に
おける屈折率を表５に示す。(Embodiment 3) FIG. 3 is an optical path diagram of the optical system of the third embodiment. In FIG. 3, 9 is a chromatic aberration correction lens of the present invention, 10 is an objective lens, 11 is a protective resin for an information recording medium, and 12 is a light beam from a light source. Table 5 shows the radius of curvature, the surface spacing, and the refractive index of the glass material at each wavelength of the chromatic aberration correction lens of the third example.
【００３２】[0032]
【表５】 [Table 5]
【００３３】本実施例の色収差補正レンズは、第１面の
曲率半径ｒ1 と第３面の曲率半径ｒ 3 がいずれも正の場
合の例である。本実施例の色収差補正レンズを前記対物
レンズと共に用いた場合、作動距離は１．２６９７５６
５ｍｍで、６８０ｎｍ近傍における軸上色収差は０．０
２１５μｍ／ｎｍとなり、対物レンズを単体で用いた場
合の約１／６程度に低減できる。このときの軸上波面収
差は、３．８ｍλである。対物レンズと色収差補正レン
ズの間隔（ｄ3 ：表４中で＊印）が３．０ｍｍの時の軸
上波面収差は３．６ｍλであり、ｄ3 が８．０ｍｍの時
の軸上波面収差は４．２ｍλである。 ＜実施例４＞図４は、第４の実施例の光学系の光路図で
ある。図４の中で、１３が本発明の色収差補正レンズ、
１４が対物レンズ、１５が情報記録媒体の保護樹脂、１
６は光源からの光束である。第４の実施例の色収差補正
レンズの曲率半径、面間隔、硝材の各波長における屈折
率を表６に示す。The chromatic aberration correction lens of this embodiment has the first surface
Radius of curvature r1And the radius of curvature r of the third surface 3Is a positive place
It is an example of a case. The objective lens is the chromatic aberration correction lens of this embodiment.
Working distance is 1.269756 when used with lens
At 5 mm, the axial chromatic aberration near 680 nm is 0.0
215 μm / nm, when the objective lens is used alone.
It can be reduced to about 1/6 of the total. On-axis wavefront collection at this time
The difference is 3.8 mλ. Objective lens and chromatic aberration correction lens
Interval (d3: Shaft when * mark in Table 4 is 3.0 mm
The upper wavefront aberration is 3.6 mλ and d3Is 8.0 mm
The on-axis wavefront aberration is 4.2 mλ. <Embodiment 4> FIG. 4 is an optical path diagram of the optical system of the fourth embodiment.
is there. In FIG. 4, 13 is the chromatic aberration correction lens of the present invention,
14 is an objective lens, 15 is a protective resin for the information recording medium, 1
Reference numeral 6 is a light beam from the light source. Correction of chromatic aberration of the fourth embodiment
Refraction of lens radius of curvature, surface spacing, and glass material wavelengths
The rates are shown in Table 6.
【００３４】[0034]
【表６】 [Table 6]
【００３５】本実施例は、プレス成形用の硝材を用いた
例である。本色収差補正レンズを実施例１で用いた対物
レンズと共に使用した場合、作動距離は１．３４２７１
７８１ｍｍで、６８０ｎｍ近傍における軸上色収差は
０．０４０９μｍ／ｎｍと対物レンズ単体の場合の１／
３未満に低減される。また、光学系の軸上波面収差は、
３．１ｍλである。また、色収差補正レンズと対物レン
ズ間の面間隔（ｄ3 ：表中で＊印）が、３．０ｍｍの時
の軸上波面収差は、８．４ｍλであり、８．０ｍｍの時
の軸上波面収差は７．４ｍλである。また、接合面の曲
率半径が２．８ｍｍと小さいため研磨加工では製造が困
難であるが、プレス成形が可能な硝材を用いているた
め、成型用の金型さえ加工できれば後は安定して製造す
ることが可能となる。This embodiment is an example using a glass material for press molding. When this chromatic aberration correction lens is used together with the objective lens used in Example 1, the working distance is 1.34271.
At 781 mm, the axial chromatic aberration in the vicinity of 680 nm is 0.0409 μm / nm, which is 1/100 of that of the objective lens alone.
It is reduced to less than 3. The on-axis wavefront aberration of the optical system is
It is 3.1 mλ. The axial wavefront aberration is 8.4 mλ when the surface distance between the chromatic aberration correction lens and the objective lens (d 3 : mark in the table) is 3.0 mm, and the axial wavefront aberration is 8.0 mm. The wavefront aberration is 7.4 mλ. Moreover, since the radius of curvature of the joint surface is as small as 2.8 mm, it is difficult to manufacture by polishing, but since a glass material that can be press-molded is used, stable manufacturing is possible after that if a molding die can be processed. It becomes possible to do.
【００３６】なお、実施例１、２あるいは３において
も、硝材のプレス成形が可能になれば安定して製造する
ことが可能になることはいうまでもない。 （実施例５）図５は本発明の色収差補正レンズを用いた
光ヘッドの構成図である。光源である半導体レーザ１７
から出射された発散光束１８はコリメートレンズ１９に
より略平行光束２０になる。略平行光束２０はビームス
プリッタ２１を透過し、色収差補正レンズ２２にいた
る。色収差補正レンズ２２からの出射光は、対物レンズ
２３により収束光束２４となり、情報記録媒体２５の情
報記録面上に集光される。情報記録媒体２５上の情報に
より変調を受けた反射光２４は、対物レンズ２３により
略平行光束となり、色収差補正レンズを透過した後、ビ
ームスプリッタ２１により反射し信号検出用光学系２６
を経て、受光素子２７にいたる。Needless to say, in Examples 1, 2 and 3 as well, if the glass material can be press-molded, it can be stably manufactured. (Embodiment 5) FIG. 5 is a configuration diagram of an optical head using the chromatic aberration correction lens of the present invention. Semiconductor laser 17 which is a light source
The divergent light beam 18 emitted from the light source is converted into a substantially parallel light beam 20 by the collimator lens 19. The substantially parallel light flux 20 passes through the beam splitter 21 and reaches the chromatic aberration correction lens 22. The light emitted from the chromatic aberration correction lens 22 becomes a convergent light beam 24 by the objective lens 23 and is condensed on the information recording surface of the information recording medium 25. The reflected light 24 modulated by the information on the information recording medium 25 becomes a substantially parallel light flux by the objective lens 23, passes through the chromatic aberration correction lens, and then is reflected by the beam splitter 21 to be reflected by the optical system 26 for signal detection.
After that, the light receiving element 27 is reached.
【００３７】本実施例の光ヘッドでは、色収差補正レン
ズ２２の働きによって半導体レーザ１７の出力を変化さ
せた場合に発生する波長の変動に伴う対物レンズのフォ
ーカスずれが低減される。そのため、ヘッドを構成する
他の光学部品の色収差の許容度を広げることが可能とな
り、高価な光学部品を用いずにヘッドを構成できる。ま
た、組レンズからなる色消し対物レンズを用いた場合と
比べて、対物レンズのアクチュエータにかかる負担が小
さくてすむため、高速アクセス等の点で有利である。In the optical head of this embodiment, the chromatic aberration correction lens 22 serves to reduce the focus shift of the objective lens due to the wavelength variation which occurs when the output of the semiconductor laser 17 is changed. Therefore, it becomes possible to widen the tolerance of chromatic aberration of other optical components constituting the head, and the head can be configured without using expensive optical components. Further, as compared with the case of using an achromatic objective lens composed of a combined lens, the burden on the actuator of the objective lens can be reduced, which is advantageous in terms of high-speed access and the like.
【００３８】[0038]
【発明の効果】以上述べたように、本発明の色収差補正
レンズは、光源の波長変動による対物レンズの軸上色収
差を良好に補正しながら、対物レンズの光軸方向への移
動があっても波面収差の変動が抑えられている。とくに
２枚構成でありながら色収差の補正効果が大きい。As described above, the chromatic aberration correction lens of the present invention satisfactorily corrects the axial chromatic aberration of the objective lens due to the wavelength fluctuation of the light source, while the objective lens moves in the optical axis direction. The fluctuation of wavefront aberration is suppressed. In particular, the two-lens configuration has a great effect of correcting chromatic aberration.
【００３９】また、プレス工法でレンズを加工する場合
には、一旦金型を加工すれば、あとは安定して成形でき
ることから、研磨加工では安定して製造できないような
小さな曲率半径の接合面であっても問題にならない。When the lens is processed by the press method, once the mold is processed, the mold can be stably formed. Therefore, it is possible to form a cemented surface having a small radius of curvature that cannot be stably manufactured by polishing. It does not matter if there is.
【００４０】また、本発明の色収差補正レンズを光ヘッ
ドに用いることにより、記録再生時のレーザのパワー変
化に伴う波長変動があっても対物レンズの焦点位置の変
動が少ないため、フォーカスサーボがはずれることはな
く、安定したヘッドが構成できる。また、対物レンズに
色消し組みレンズを用いた場合に比べて、対物レンズア
クチュエータにかかる負担を小さくすることができる。Further, by using the chromatic aberration correction lens of the present invention for the optical head, the focus servo is out of focus because the focus position of the objective lens does not fluctuate even if the wavelength fluctuates due to the laser power change during recording and reproduction. Stable head can be constructed. In addition, the load on the objective lens actuator can be reduced as compared with the case where an achromatic lens is used as the objective lens.
【図１】本発明の第１の実施例を示す光路図。FIG. 1 is an optical path diagram showing a first embodiment of the present invention.
【図２】本発明の第２の実施例を示す光路図。FIG. 2 is an optical path diagram showing a second embodiment of the present invention.
【図３】本発明の第３の実施例を示す光路図。FIG. 3 is an optical path diagram showing a third embodiment of the present invention.
【図４】本発明の第４の実施例を示す光路図。FIG. 4 is an optical path diagram showing a fourth embodiment of the present invention.
【図５】本発明の第５の実施例の色収差補正レンズを用
いた光ヘッドの構成図。FIG. 5 is a configuration diagram of an optical head using a chromatic aberration correction lens according to a fifth embodiment of the present invention.
【図６】従来の光ヘッドの光路図。FIG. 6 is an optical path diagram of a conventional optical head.
１、５、９、１３、２２ 色収差補正レンズ ２、６、１０、１４、２３、３３ 対物レンズ ３、７、１１、１５、２５、３５ 情報記録媒体の
保護樹脂 ４、８、１２、１６ 光源からの略平行光束 １７、２８ 半導体レーザ １８、２９ 光源から出射された発散光束 １９、３０ コリメートレンズ ２０、３１ 略平行光束 ２１、３２ ビームスプリッタ ２４、３４ 収束光束 ２６、３６ 信号検出用光学系 ２７、３７ 受光素子 ｒ1 、ｒ2 、ｒ3 、ｒ4 、ｒ5 、ｒ6 それぞれの
面の曲率半径 ｄ1 、ｄ2 、ｄ3 、ｄ4 、ｄ5 、ｄ6 面間隔1, 5, 9, 13, 22 Chromatic aberration correction lens 2, 6, 10, 14, 23, 33 Objective lens 3, 7, 11, 15, 25, 35 Protective resin for information recording medium 4, 8, 12, 16 Light source Approximately parallel luminous flux 17, 28 Semiconductor lasers 18, 29 Divergent luminous flux emitted from light source 19, 30 Collimating lens 20, 31 Substantially parallel luminous flux 21, 32 Beam splitter 24, 34 Convergent luminous flux 26, 36 Signal detection optical system 27 , 37 Light receiving elements r 1 , r 2 , r 3 , r 4 , r 5 , r 6 curvature radii of the respective surfaces d 1 , d 2 , d 3 , d 4 , d 5 , d 6 surface spacing
Claims (4)
使用する色収差補正用のレンズであって、前記色収差補
正レンズは、１枚の正レンズと１枚の負レンズとを貼り
合わせた接合レンズであり、かつ前記色収差補正レンズ
の光源側の面の曲率半径をｒ1 、出射側の面の曲率半径
をｒ3 、対物レンズの焦点距離をｆo とするとき、下記
式（数１）及び（数２）を満足することを特徴とする色
収差補正レンズ。 【数１】 【数２】 1. A lens for chromatic aberration correction used in combination with an objective lens for an optical head, wherein the chromatic aberration correction lens is a cemented lens in which one positive lens and one negative lens are bonded together. There, and the chromatic aberration correction r 1 radius of curvature of the light source side surface of the lens, the radius of curvature of the exit side r 3, when the focal length of the objective lens and f o, the following formula (formula 1) and ( A chromatic aberration correction lens characterized by satisfying the expression (2). [Equation 1] [Equation 2]
径ｒ1 と、出射側の面の曲率半径ｒ3 と、対物レンズの
焦点距離ｆo の積が下記式（数３）を満足する請求項１
に記載の色収差補正レンズ。 【数３】 And wherein the chromatic aberration correcting light source-side radius of curvature r 1 of the surface of the lens, the radius of curvature r 3 of the surface of the emission side, the product of the focal length f o of the objective lens satisfies the following expression (Expression 3) Claim 1
The chromatic aberration correction lens described in. [Equation 3]
合わせた接合レンズであって、前記正レンズと前記負レ
ンズのうち少なくとも１枚、望ましくは２枚のレンズが
プレス成形可能な硝材で形成されている請求項１または
２に記載の色収差補正レンズ。3. A cemented lens in which one positive lens and one negative lens are cemented together, and at least one, preferably two lenses of the positive lens and the negative lens can be press-molded. The chromatic aberration correction lens according to claim 1, which is made of a glass material.
分離手段と、光束を情報記録媒体上に集光する手段と、
前記情報記録媒体からの反射または透過光を受光する受
光手段を有する光ヘッドにおいて、前記光源と前記集光
する手段との間に請求項１，２または３に記載の色収差
補正レンズを有することを特徴とする光ヘッド。4. A light source, a light beam separating means for separating a light beam from the light source, a means for condensing the light beam on an information recording medium,
An optical head having a light receiving means for receiving reflected or transmitted light from the information recording medium, comprising the chromatic aberration correction lens according to claim 1, 2 or 3 between the light source and the light collecting means. Characteristic optical head.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP12352294A JPH07333498A (en) | 1994-06-06 | 1994-06-06 | Lens for correcting chromatic aberration and optical head formed by using the same |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP12352294A JPH07333498A (en) | 1994-06-06 | 1994-06-06 | Lens for correcting chromatic aberration and optical head formed by using the same |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH07333498A true JPH07333498A (en) | 1995-12-22 |
Family
ID=14862702
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP12352294A Pending JPH07333498A (en) | 1994-06-06 | 1994-06-06 | Lens for correcting chromatic aberration and optical head formed by using the same |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH07333498A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2004504618A (en) * | 2000-07-24 | 2004-02-12 | ライカ ジオシステムズ アクチエンゲゼルシャフト | Method and apparatus for optically measuring distance or velocity |
-
1994
- 1994-06-06 JP JP12352294A patent/JPH07333498A/en active Pending
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2004504618A (en) * | 2000-07-24 | 2004-02-12 | ライカ ジオシステムズ アクチエンゲゼルシャフト | Method and apparatus for optically measuring distance or velocity |
| JP4868485B2 (en) * | 2000-07-24 | 2012-02-01 | ライカ ジオシステムズ アクチエンゲゼルシャフト | Method and apparatus for optically measuring distance or velocity |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| A521 | Written amendment |
Free format text: JAPANESE INTERMEDIATE CODE: A523 Effective date: 20040903 |