JPH0625823B2 - Objective lens for optical disk - Google Patents
Objective lens for optical diskInfo
- Publication number
- JPH0625823B2 JPH0625823B2 JP10045285A JP10045285A JPH0625823B2 JP H0625823 B2 JPH0625823 B2 JP H0625823B2 JP 10045285 A JP10045285 A JP 10045285A JP 10045285 A JP10045285 A JP 10045285A JP H0625823 B2 JPH0625823 B2 JP H0625823B2
- Authority
- JP
- Japan
- Prior art keywords
- lens
- group
- focal length
- aberration
- convex
- 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.)
- Expired - Lifetime
Links
- 230000003287 optical effect Effects 0.000 title claims description 19
- 230000005499 meniscus Effects 0.000 claims description 5
- 230000004075 alteration Effects 0.000 description 16
- 239000000470 constituent Substances 0.000 description 8
- 238000010586 diagram Methods 0.000 description 4
- 238000004519 manufacturing process Methods 0.000 description 4
- 239000006059 cover glass Substances 0.000 description 3
- 201000009310 astigmatism Diseases 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 239000011521 glass Substances 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 238000000034 method Methods 0.000 description 1
Landscapes
- Lenses (AREA)
Description
【発明の詳細な説明】 〔産業上の利用分野〕 この発明は、主としてレーザー光を回折限界付近にまで
集光させ得るように収差補正された小型な大口径レン
ズ、特にディジタルオーディオディスクやビデオディス
ク等の光ディスク用対物レンズに関する。DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention mainly relates to a small large-diameter lens whose aberration is corrected so that a laser beam can be focused to near the diffraction limit, and particularly to a digital audio disc or a video disc. And the like for an objective lens for an optical disc.
ディジタルオーディオディスク用あるいはビデオディス
ク用のピックアップレンズとしての光ディスク用レンズ
は、ピックアップユニット等の小さなアクチュエーター
に装着され、フォーカシング等の制御駆動を受けるの
で、まず、小型、軽量であることが要求される。さらに
上記駆動に対し、駆動時にレンズがディスク面に衝突し
ないよう充分な作動距離を有することが要求されてい
る。また、レーザ光をディスク表面に微小スポットとし
て集光させるために、大きなNA(開口数)を保ちなが
ら光軸上とその周辺にわたって、ほぼ無収差に近い程度
に良好に収差が補正されていることが必要である。その
他に、作り易いこと、低コストであること、性能安定
性、耐久性などが求められている。無論これらの諸条件
を満足するレンズ系を提供するには、設計、製作の両面
で精密な技術が必要であることは言うまでもない。A lens for an optical disc as a pickup lens for a digital audio disc or a video disc is mounted on a small actuator such as a pickup unit and is subjected to control drive such as focusing, so that it is first required to be small and lightweight. Further, it is required for the above driving to have a sufficient working distance so that the lens does not collide with the disk surface during driving. Further, in order to focus the laser light as a minute spot on the disk surface, the aberration is favorably corrected over the optical axis and its periphery while maintaining a large NA (near numerical aperture) to a level almost free of aberration. is necessary. In addition, easy manufacture, low cost, performance stability, durability, etc. are required. Needless to say, precise technology is required in both design and manufacturing in order to provide a lens system that satisfies these various conditions.
これらの諸条件を満足する光ディスク用レンズとして、
種々のタイプのレンズ系が報告されているが、小型、軽
量という観点から、構成レンズ枚数が3枚以下のタイプ
について考えると、以下の数種類のタイプに限定され
る。すなわち3群3枚構成、2群3枚構成、2群2枚構
成、非球面を備えたレンズ系、両面非球面単レンズの5
種類である。As an optical disc lens that satisfies these conditions,
Various types of lens systems have been reported, but from the viewpoint of small size and light weight, when considering a type having three or less lens elements, the type is limited to the following several types. That is, three groups, three elements, two groups, three elements, two groups, two elements, a lens system having an aspherical surface, and a double-sided aspherical single lens.
It is a kind.
(発明が解決しようとしている問題点) 上記5種類のタイプのレンズ系に関してその長所及び短
所を検討してみる。(Problems to be Solved by the Invention) The advantages and disadvantages of the above five types of lens systems will be examined.
3群3枚構成のレンズ系は、収差補正の自由度が多いと
いう利点を有する反面、組立て時に3枚のレンズを偏心
なく鏡筒に組込まねばならないので、光軸調整に手間が
かかり、コスト高になり易いという欠点を有している。
また2群3枚構成のレンズ系では、3群3枚のレンズ系
にくらべれば収差補正の自由度は減るものの、鏡筒への
組込みは2枚のレンズですみ(1枚は接合レンズとなっ
ている)、光軸調整は比較的容易に行えるという利点が
ある。2群2枚構成のレンズ系については組込み容易性
は、2群3枚構成のレンズ系と同様であると同時に、構
成レンズが1枚少ない分だけコストの面で有利ではある
のだが、収差補正の自由度が少なくなるので、大きなN
A(開口数)では軸上の性能はなんとか保てても、軸外
において充分な収差補正をするのが困難である。また、
非球面を採用しているレンズ系は、収差補正の自由度が
多くなるので、中心から軸外へと充分に収差を補正する
ことが可能であるとともに構成枚数を1枚乃至2枚程度
で済ませることが出来るので、小型軽量で組立てが容易
であるという利点も併せ持っている。しかし、低コスト
化を狙っているので、非球面レンズの材質には主として
プラスチックを採用しているため、温度の変化に対する
光学定数の変動が大きかったり、プラスチックの複屈折
性により高NA化が困難であるなどの欠点を持ってい
る。The lens system with the three-group, three-lens configuration has the advantage that there are many degrees of freedom in aberration correction, but on the other hand, the three lenses must be assembled in the lens barrel without decentration during assembly, which requires time and effort for optical axis adjustment. It has the drawback of being prone to
In addition, in a lens system with a two-group, three-lens configuration, the degree of freedom in aberration correction is less than in a three-group, three-lens system, but only two lenses need to be incorporated into the lens barrel (one is a cemented lens). However, there is an advantage that the optical axis can be adjusted relatively easily. The two-group, two-lens configuration lens system is as easy to assemble as the two-group, three-lens configuration lens system, and at the same time, it is advantageous in terms of cost due to the fact that the number of constituent lenses is one. Since the degree of freedom of
With A (numerical aperture), it is difficult to perform sufficient aberration correction off-axis even though the on-axis performance can be managed. Also,
Since the lens system employing the aspherical surface has a large degree of freedom of aberration correction, it is possible to sufficiently correct the aberration from the center to the off-axis, and the number of constituent elements may be one or two. Therefore, it also has the advantages of being small and light and easy to assemble. However, because we are aiming for cost reduction, we mainly use plastic as the material of the aspherical lens, so there are large fluctuations in the optical constants with changes in temperature, and it is difficult to increase the NA due to the birefringence of plastic. It has drawbacks such as
以上のように各タイプともそれぞれ長所・短所を持って
いることが考察できる。つまり現在実用に併せられてい
る光ディスク用レンズでは、各タイプのレベルで実用化
せざるを得ないのが実情である。従って光ディスク用レ
ンズとしてどのレベルで実用性を見出すのかが採用する
レンズタイプを決める上で重要なポイントとなってい
る。As described above, it can be considered that each type has advantages and disadvantages. In other words, with the optical disk lenses currently being put into practical use, the reality is that they must be put to practical use at the level of each type. Therefore, at what level to find practicality as an optical disk lens is an important point in determining the lens type to be adopted.
この様な考察から本発明者は、収差補正の自由度、高N
A化、小型軽量性、製作の容易さ、性能安定性の各点に
おいてガラスレンズによる2群3枚構成のレンズ系が最
も実用性が多いものであると判断するに至った。2群3
枚構成の光ディスク用レンズとしては、過去に本出願人
によって特開昭59−15913号の提案がなされている。こ
れは全系の焦点距離をfとするとき、第1群レンズと第
2群レンズとの軸上空気間隔が約0.3 f程度と広いので
全長が長くなっており、コンパクト性という点において
は不十分なレンズ系であった。From the above consideration, the present inventor found that the degree of freedom of aberration correction is high
From the viewpoints of A-size, small size and light weight, ease of manufacture, and performance stability, it has been judged that the lens system of two-group, three-lens configuration with glass lenses is most practical. 2 groups 3
As a lens for an optical disc having a single-piece construction, the applicant of the present invention has previously proposed Japanese Patent Laid-Open No. 59-15913. When the focal length of the entire system is f, the axial air gap between the first lens group and the second lens group is as large as about 0.3 f, so the overall length is long, which is unsatisfactory in terms of compactness. It was a sufficient lens system.
(問題点を解決するための手段) 本発明の目的は2群3枚構成の光ディスク用レンズにお
いて、全系の焦点距離をfとするとき、第1群レンズと
第2群レンズとの軸上空気間隔を0.02f程度に小さく
し、小型化を狙った光ディスク用対物レンズを提案する
ことである。(Means for Solving the Problems) An object of the present invention is to provide an optical disc lens having a two-group, three-lens configuration with an axial distance between the first lens group and the second lens group when the focal length of the entire system is f. The objective is to propose an objective lens for optical discs that aims at downsizing by reducing the air gap to about 0.02f.
本発明に係わるレンズ系は第1図以下に示すように構成
されている。即ち、光束の入射側から順に集光側へ向か
って第1群レンズ及び第2群レンズの2つのレンズ群よ
り成り、かつ光束の入射側から順に、第1群レンズは入
射側に凸面を向けた凹メカニカスレンズの第1レンズと
凸レンズの第2レンズとの接合レンズによって構成され
ており、第2群レンズは、入射側に凸面を向けた凸メニ
スカスレンズの第3レンズで構成されている。さらに以
下の条件を満たすことを特徴としている。The lens system according to the present invention is constructed as shown in FIG. That is, it is composed of two lens groups, a first lens group and a second lens group, from the light incident side toward the light condensing side in order, and the first lens group has a convex surface directed toward the incident side from the light incident side. It is composed of a cemented lens of a first lens of a concave mechanical lens and a second lens of a convex lens, and the second group lens is composed of a third lens of a convex meniscus lens with a convex surface facing the incident side. . Further, it is characterized by satisfying the following conditions.
即ち (1)0.1<f/f12<0.2 (2)1.5<r5/f3<2.3 但し、fは全系の焦点距離、f12は第1群レンズ焦点距
離、f3は第2群レンズの焦点距離、r5は第3レンズ
の集光側の曲率半径である。That is, (1) 0.1 <f / f 12 <0.2 (2) 1.5 <r 5 / f 3 <2.3 where f is the focal length of the entire system, f 12 is the focal length of the first lens group, and f 3 is the second lens group. The focal length of the lens, r 5 is the radius of curvature of the third lens on the light collecting side.
上記条件式(1)は作動距離を良好に保つための条件で
ある。上限を越えると、作動距離が小さくなりフォーカ
シングの制御駆動に支障をきたす。また下限を越える
と、第2群レンズの第3レンズの負担するパワーが大き
くなりすぎてしまい、各収差を良好に補正することが困
難になる。The conditional expression (1) is a condition for maintaining a good working distance. If the upper limit is exceeded, the working distance becomes small and the control drive of focusing is hindered. On the other hand, when the value goes below the lower limit, the power of the third lens of the second lens group becomes too large, and it becomes difficult to satisfactorily correct each aberration.
上記条件式(2)は正弦条件を良好に補正するための条
件である。上限を越えると正弦条件の補正過剰、下限を
越えると補正不足となり、ともに軸外収差が悪化して、
軸外の良好な集光性能の確保が困難になる。The conditional expression (2) is a condition for favorably correcting the sine condition. If the upper limit is exceeded, over-correction of the sine condition will occur, and if the lower limit is exceeded, under-correction will occur.
It becomes difficult to secure good off-axis light collection performance.
上記構成と各条件を満たすことにより、第1群レンズと
第2群レンズの軸上空気間隔を極力小さくすることが可
能となり、さらに小型化した2群3枚構成の光ディスク
用レンズを実現することができる。By satisfying the above-mentioned configuration and each condition, it is possible to minimize the axial air distance between the first group lens and the second group lens, and to realize a further downsized lens for an optical disc having a two-group three-lens configuration. You can
以下に本発明にもとずく実施例を示す。 Examples according to the present invention will be shown below.
第1図で本発明の光ディスク用対物レンズの一実施例の
構成を示すと、光束の入射側から順に集光側へ向って、
第1群レンズI及び第2群レンズIIの2つのレンズ群に
よって構成されており、入射側から順に第1群レンズI
は入射側に凸面を向けた凹メニスカスレンズの第1レン
ズL1と凸レンズの第2レンズL2との接合レンズによ
って構成されており、第2群レンズIIは入射側に凸面を
向けた凸メニスカスレンズの第3レンズL3で構成され
ている2群3枚構成のレンズ系である。尚符号1はカバ
ーガラスである。第2図は収差図である。FIG. 1 shows the configuration of an embodiment of the objective lens for an optical disc according to the present invention.
The first lens group I and the second lens group II are composed of two lens groups, and the first lens group I is arranged in order from the incident side.
Is a cemented lens of a first lens L 1 which is a concave meniscus lens having a convex surface directed toward the incident side and a second lens L 2 which is a convex lens, and the second lens group II is a convex meniscus having a convex surface directed toward the incident side. It is a lens system of a two-group, three-lens configuration including a third lens L 3 of the lens. Reference numeral 1 is a cover glass. FIG. 2 is an aberration diagram.
但し r1、r2…r5:各構成レンズの曲率半径 d1、d2…d4:各構成レンズの軸上厚みと軸上空気
間隔 n1…n3:各構成レンズの波長780 nmにおける屈折率 ν1…ν3:各構成レンズのアッベ数 f:全系の焦点距離 f12:第1群レンズの焦点距離 f3:第2群レンズの焦点距離 NA:開口数 td:カバーガラスの厚み tn:カバーガラスの波長780 nmにおける屈折率 θ:半画角 実施例1 f=1 NA=0.47 r1=1.875 d1=0.15 n1=1.81961 ν1=37.3 r2=0.73 d2=0.425 n2=1.51118 ν2=64.2 r3=−3.875 d3=0.02 r4=0.7175 d4=0.3 n3=1.51118 ν3=64.2 r5=2.515 td=0.3 tn=1.55 f/f12=0.16 r5/f3=2.21 実施例2 f=1 NA=0.47 r1=2.215 d1=0.15 n1=1.81961 ν1=37.3 r2=0.7125 d2=0.4 n2=1.55749 ν2=60.8 r3=−4.42 d3=0.02 r4=0.7175 d4=0.3 n3=1.81961 ν3=37.3 r5=2.5225 td=0.3 tn=1.55 f/f12=0.15 r5/f3=2.22 実施例3 f=1 NA=0.47 r1=2.0 d1=0.125 n1=1.81961 ν1=37.3 r2=0.7125 d2=0.4 n2=1.55749 ν2=60.8 r3=−5.125 d3=0.02 r4=0.72 d4=0.3 n3=1.81961 ν3=37.3 r5=2.52 td=0.3 tn=1.55 f/f12=0.16 r5/f3=2.20 実施例4 f=1 NA=0.47 r1=2.0 d1=0.15 n1=1.81961 ν1=37.3 r2=0.735 d2=0.425 n2=1.51118 ν2=64.2 r3=−3.375 d3=0.02 r4=0.7175 d4=0.3 n3=1.81961 ν3=37.3 r5=2.4845 td=0.3 tn=1.55 f/f12=0.15 r5/f3=2.17 実施例5 f=1 NA=0.47 r1=1.875 d1=0.15 n1=1.81961 ν1=37.3 r2=0.7225 d2=0.425 n2=1.51118 ν2=64.2 r3=−3.925 d3=0.02 r4=0.71 d4=0.3 n3=1.81961 ν3=37.3 r5=2.4388 td=0.3 tn=1.55 f/f12=0.15 r5/f3=2.15 実施例6 f=1 NA=0.47 r1=1.8 d1=0.175 n1=1.81961 ν1=37.3 r2=0.685 d2=0.375 n2=1.61335 ν2=60.3 r3=15.0 d3=0.02 r4=0.685 d4=0.3 n3=1.81961 ν3=37.3 r5=1.926 td=0.3 tn=1.51 f/f12=0.2 r5/f3=1.65 〔発明の効果〕 以上の様に構成したことにより、本発明の光ディスク用
レンズは、2群3枚構成で第1群レンズと第2群レンズ
との軸上空気間隔を0.02f程度に小さくすることが出来
てより一層コンパクト化され、大口径で明かるく、光軸
上とその周辺にわたってほぼ無収差に近い程度に良好に
収差が補正され、小さく加工の容易なレンズで製造コス
トが低減され、すぐれた性能を有する良好に改良された
光ディスク用レンズが実現できる。However, r 1 , r 2 ... R 5 : Curvature radii of each constituent lens d 1 , d 2 ... d 4 : axial thickness and axial air gap of each constituent lens n 1 ... n 3 : wavelength of each constituent lens 780 nm Refractive index at ν 1 ... ν 3 : Abbe's number of each constituent lens f: Focal length of the entire system f 12 : Focal length of the first group lens f 3 : Focal length of the second group lens NA: Numerical aperture td: Cover glass Thickness tn: Refractive index of cover glass at wavelength 780 nm θ: Half angle of view Example 1 f = 1 NA = 0.47 r 1 = 1.875 d 1 = 0.15 n 1 = 1.816 61 ν 1 = 37.3 r 2 = 0.73 d 2 = 0.425 n 2 = 1.51118 ν 2 = 64.2 r 3 = -3.875 d 3 = 0.02 r 4 = 0.7175 d 4 = 0.3 n 3 = 1.51118 ν 3 = 64.2 r 5 = 2.515 t d = 0.3 t n = 1.55 f / f 12 = 0.16 r 5 / f 3 = 2.21 Example 2 f = 1 NA = 0.47 r 1 = 2.215 d 1 = 0.15 n 1 = 1.81961 ν 1 = 37 .3 r 2 = 0.7125 d 2 = 0.4 n 2 = 1.55749 ν 2 = 60.8 r 3 = −4.42 d 3 = 0.02 r 4 = 0.7175 d 4 = 0.3 n 3 = 1.81961 ν 3 = 37.3 r 5 = 2.5225 t d = 0.3 t n = 1.55 f / f 12 = 0.15 r 5 / f 3 = 2.22 Example 3 f = 1 NA = 0.47 r 1 = 2.0 d 1 = 0.125 n 1 = 1.81961 ν 1 = 37.3 r 2 = 0.7125 d 2 = 0.4 n 2 = 1.55749 ν 2 = 60.8 r 3 = −5.125 d 3 = 0.02 r 4 = 0.72 d 4 = 0.3 n 3 = 1.81961 ν 3 = 37.3 r 5 = 2.52 t d = 0.3 t n = 1.55 f / f 12 = 0.16 r 5 / f 3 = 2.20 example 4 f = 1 NA = 0.47 r 1 = 2.0 d 1 = 0.15 n 1 = 1.81961 ν 1 = 37.3 r 2 = 0.735 d 2 = 0.425 n 2 = 1.51118 ν 2 = 64.2 r 3 = −3.375 d 3 = 0.02 r 4 = 0.7175 d 4 = 0.3 n 3 = 1.81961 ν 3 = 37.3 r 5 = 2.4845 t d = 0.3 t n = 1.55 f / f 12 = 0.15 r 5 / f 3 = 2.17 Example 5 f = 1 NA = 0.47 r 1 = 1.875 d 1 = 0.15 n 1 = 1.81961 ν 1 = 37.3 r 2 = 0.7225 d 2 = 0.425 n 2 = 1.51118 ν 2 = 64.2 r 3 = -3.925 d 3 = 0.02 r 4 = 0.71 d 4 = 0.3 n 3 = 1.81961 ν 3 = 37.3 r 5 = 2.4388 t d = 0.3 t n = 1.55 f / f 12 = 0.15 r 5 / f 3 = 2.15 Example 6 f = 1 NA = 0.47 r 1 = 1.8 d 1 = 0.175 n 1 = 1.81961 ν 1 = 37.3 r 2 = 0.685 d 2 = 0.375 n 2 = 1.61335 ν 2 = 60.3 r 3 = 15.0 d 3 = 0.02 r 4 = 0.685 d 4 = 0.3 n 3 = 1.81961 ν 3 37.3 r 5 = 1.926 t d = 0.3 t n = 1.51 f / f 12 = 0.2 r 5 / f 3 = 1.65 [Effects of the Invention] The optical disk lens of the present invention has the two groups With a three-lens configuration, the axial air gap between the first and second lens groups can be reduced to about 0.02f, making it even more compact and with a large aperture. Optically, the aberration is corrected well on the optical axis and its periphery to a level almost free of aberration, and the manufacturing cost is reduced with a small and easy-to-process lens, and a well-improved optical disc lens with excellent performance is provided. realizable.
第1図は本発明に係る実施例におけるレンズ構成図、第
2図は実施例1の収差図で(イ)球面収差、(ロ)正弦
条件、(ハ)非点収差を表わす。(尚、実施例2〜6の
収差図は実施例1に近似するので省略する。) r1…r5:各構成レンズの曲率半径、 d1…d4:各構成レンズの軸上厚みと軸上空気間隔、
I:第1群レンズ、II:第2群レンズ、 L1:第1レンズ、L2:第2レンズ、 L3:第3レンズ。FIG. 1 is a lens configuration diagram of an example according to the present invention, and FIG. 2 is an aberration diagram of the example 1 showing (a) spherical aberration, (b) sine condition, and (c) astigmatism. (Note that the aberration diagrams of Examples 2 to 6 are omitted because they are similar to those of Example 1.) r 1 ... r 5 : radius of curvature of each constituent lens, d 1 ... d 4 : axial thickness of each constituent lens, and On-axis air spacing,
I: The first group lens, II: a second lens group, L 1: a first lens, L 2: the second lens, L 3: the third lens.
Claims (1)
1群レンズ及び第2群レンズの2つのレンズ群によって
構成されており、入射側から順に第1群レンズは、入射
側に凸面を向けた凹メニスカスレンズの第1レンズと凸
レンズの第2レンズとの結合レンズによって構成されて
おり、第2群レンズは入射側に凸面を向けた凸メニスカ
スレンズの第3レンズで構成されている2群3枚構成の
レンズ系であって、以下の条件を満たすことを特徴とす
る光ディスク用対物レンズ。 (1)0.1<f/f12<0.2 (2)1.5<r5/f3<2.3 但し、fは全系の焦点距離、f12は第1群レンズの焦点
距離、f3は第2群レンズの焦点距離、r5は第3レン
ズの集光側の曲率半径である。1. A first lens group and a second lens group, each of which is composed of two lens groups, which are arranged in this order from the incident side of a light beam toward the condensing side. The first lens is a concave meniscus lens having a convex surface facing to and the second lens is a convex lens. The second lens group is composed of a third lens being a convex meniscus lens having a convex surface facing the incident side. An objective lens for an optical disc, which is a lens system of two-lens-three-lens configuration and satisfies the following conditions. (1) 0.1 <f / f 12 <0.2 (2) 1.5 <r 5 / f 3 <2.3 where f is the focal length of the entire system, f 12 is the focal length of the first lens group, and f 3 is the second lens group. The focal length of the lens, r 5 is the radius of curvature of the third lens on the light collecting side.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP10045285A JPH0625823B2 (en) | 1985-05-14 | 1985-05-14 | Objective lens for optical disk |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP10045285A JPH0625823B2 (en) | 1985-05-14 | 1985-05-14 | Objective lens for optical disk |
Publications (2)
Publication Number | Publication Date |
---|---|
JPS61259215A JPS61259215A (en) | 1986-11-17 |
JPH0625823B2 true JPH0625823B2 (en) | 1994-04-06 |
Family
ID=14274303
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
JP10045285A Expired - Lifetime JPH0625823B2 (en) | 1985-05-14 | 1985-05-14 | Objective lens for optical disk |
Country Status (1)
Country | Link |
---|---|
JP (1) | JPH0625823B2 (en) |
Families Citing this family (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5491587A (en) * | 1989-02-28 | 1996-02-13 | Asahi Kogaku Kogyo Kabushiki Kaisha | Collimating lens for optical system using semiconductor laser |
US5173809A (en) * | 1989-02-28 | 1992-12-22 | Asahi Kogaku Kogyo Kabushiki Kaisha | Objective lens system of optical information recording/reproducing apparatus |
JP2902435B2 (en) * | 1989-02-28 | 1999-06-07 | 旭光学工業株式会社 | Objective lens system for optical information recording / reproducing device |
-
1985
- 1985-05-14 JP JP10045285A patent/JPH0625823B2/en not_active Expired - Lifetime
Also Published As
Publication number | Publication date |
---|---|
JPS61259215A (en) | 1986-11-17 |
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