JPH0140325B2 - - Google Patents
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- JPH0140325B2 JPH0140325B2 JP61154500A JP15450086A JPH0140325B2 JP H0140325 B2 JPH0140325 B2 JP H0140325B2 JP 61154500 A JP61154500 A JP 61154500A JP 15450086 A JP15450086 A JP 15450086A JP H0140325 B2 JPH0140325 B2 JP H0140325B2
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- Prior art keywords
- lens
- group
- positive
- focal length
- cemented
- Prior art date
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- 230000003287 optical effect Effects 0.000 claims description 24
- 239000002131 composite material Substances 0.000 claims description 6
- 230000004075 alteration Effects 0.000 description 34
- 238000010586 diagram Methods 0.000 description 8
- 210000001747 pupil Anatomy 0.000 description 5
- 230000000694 effects Effects 0.000 description 4
- 206010010071 Coma Diseases 0.000 description 3
- 230000002411 adverse Effects 0.000 description 1
- 230000006866 deterioration Effects 0.000 description 1
- 238000003384 imaging method Methods 0.000 description 1
Description
【発明の詳細な説明】
ａ 技術分野
本発明は、光デイスク用対物レンズに関するも
のである。DETAILED DESCRIPTION OF THE INVENTION a. Technical Field The present invention relates to an objective lens for an optical disk.
ｂ 従来技術及びその問題点
光デイスクに記録された高密度の情報の読み取
りに使用されるレンズは、高密度の信号を読み取
らなければならないので、その分解能は1μ程度
が要求される。b. Prior art and its problems Lenses used to read high-density information recorded on optical disks must read high-density signals, so their resolution is required to be about 1 μm.
従来、この要求を満足するための光デイスク用
対物レンズの発明が多数なされているが、その殆
どは単波長における収差補正がなされているのみ
である。光源が安定している場合や、光源の波長
による変動による結像性能の変化が無視できる光
学系においては、単波長での収差補正で充分であ
ると考えられるが、光源が不安定で、波長の変動
があり、それによる収差の変動が無視できない光
学系においては、単波長の収差補正だけでは前記
要求を満足する事ができず、複数波長の収差補
正、即ち色収差の補正を考慮しなくてはならな
い。 Conventionally, many inventions of objective lenses for optical disks have been made to satisfy this requirement, but most of them only correct aberrations at a single wavelength. In cases where the light source is stable or in optical systems where changes in imaging performance due to fluctuations in the wavelength of the light source can be ignored, aberration correction at a single wavelength may be sufficient. In optical systems where there are fluctuations in aberrations and the resulting fluctuations in aberrations cannot be ignored, it is not possible to satisfy the above requirements by correcting single wavelength aberrations alone, and correction of aberrations of multiple wavelengths, that is, correction of chromatic aberrations, must be considered. Must not be.
本発明に類似したレンズタイプの発明は、例え
ば、特開昭51−18557号、特開昭55−4068号、特
開昭58−87521号、特開昭59−15921号、特開昭59
−174810号、特開昭61−91612号などがあるが、
いずれも球面収差、コマ収差などの収差補正はな
されているものの、色収差の補正に対する配慮は
なされていない。 Lens type inventions similar to the present invention are disclosed, for example, in JP-A-51-18557, JP-A-55-4068, JP-A-58-87521, JP-A-59-15921, and JP-A-59.
-174810, JP-A No. 61-91612, etc.
In both cases, aberrations such as spherical aberration and comatic aberration are corrected, but no consideration is given to correction of chromatic aberration.
また、光デイスクシステムの動作では、記録面
（デイスク面）に当つた光は反射され、再びレン
ズに戻り光源方向に向い、フオーンカシングやト
ラツキング等の各種信号を発生するために、光セ
ンサーへ導かれるようになつている。従つて、対
物レンズは、記録面での反射光を集光する能力も
考慮される必要があるが、射出瞳が記録面に近い
従来の対物レンズは、トラツキングやフオーンカ
シングの動作の際に、コリメート光と対物レンズ
の光軸が傾いた場合に反射光がレンズの瞳に有効
に取り込まれず、ケラレが生じ、センサ上の光量
バランスをくずし、各種信号が誤差を含むように
なるという問題があつた。 In addition, in the operation of an optical disk system, the light that hits the recording surface (disk surface) is reflected, returns to the lens, faces the light source, and is guided to the optical sensor to generate various signals such as focussing and tracking. It's becoming like that. Therefore, the ability of the objective lens to condense the reflected light from the recording surface must also be taken into account, but conventional objective lenses, whose exit pupil is close to the recording surface, cannot collimate during tracking or focussing operations. There was a problem that when the optical axis of the light and objective lens was tilted, the reflected light was not effectively captured by the pupil of the lens, causing vignetting, disrupting the light balance on the sensor, and causing various signals to contain errors. .
Ｃ 目的
本発明は、単波長のみでなく、複数波長におけ
る収差補正、即ち色収差の補正を良好に行い、光
源の波長の変動による収差変化を極力小くすると
共に、射出瞳位置デイスクから離されておりデイ
スクからの反射光の集光能力の高い、しかもNA
（開口数）の大きい光デイスク用対物レンズを提
供しようとするものである。C. Purpose of the present invention is to effectively correct aberrations not only at a single wavelength but also at multiple wavelengths, that is, to correct chromatic aberrations, to minimize changes in aberrations due to fluctuations in the wavelength of a light source, and to set the exit pupil position apart from the disk. High ability to collect reflected light from the disc, and NA
The object of the present invention is to provide an objective lens for optical disks with a large numerical aperture.
ｄ 問題点の解決手段
本発明の光デイスク用対物レンズは、正レンズ
と負レンズとの接合レンズから成り正の焦点距離
を有する第１群レンズと、正の焦点距離を有する
第２群レンズとから成る２群３枚構成の光デイス
ク用対物レンズにおいて、前記第１群レンズは、
光源側から、正・負の接合レンズあるいは負・正
の接合レンズから成り、前記第２群レンズは、そ
の光源側の面を非球面とした両凸レンズから成
り、かつ以下の諸条件を満足している事を特徴と
するものである。d. Means for Solving Problems The objective lens for optical disks of the present invention is composed of a cemented lens of a positive lens and a negative lens, and includes a first group lens having a positive focal length, and a second group lens having a positive focal length. In the optical disk objective lens having three elements in two groups, the first group lens is:
From the light source side, it consists of a positive/negative cemented lens or a negative/positive cemented lens, and the second lens group consists of a biconvex lens whose surface on the light source side is an aspherical surface, and satisfies the following conditions. It is characterized by the fact that
(1) ｜ν1―ν2｜＞20
(2) ｜r2｜＜ｆ
(3) 0.5＞ｆ／fI＞0.1
ここでｆはレンズ全系の合成焦点距離、ν1―ν2
は第１群レンズを構成する２枚のレンズのアツベ
数の差、r2は第１群レンズの接合面の曲率半径、
fIは第１群レンズの合成焦点距離である。(1) ｜ν 1 ―ν 2 ｜＞20 (2) ｜r 2 ｜＜f (3) 0.5＞f/f I ＞0.1 Here, f is the composite focal length of the entire lens system, ν 1 －ν 2
is the difference in the Atsube numbers of the two lenses that make up the first group lens, r2 is the radius of curvature of the cemented surface of the first group lens,
f I is the composite focal length of the first lens group.
ｅ 作用 次に上記各条件について説明する。e action Next, each of the above conditions will be explained.
(1)の条件は色収差の補正を適切にするための条
件であり、｜ν1―ν2｜が下限よりも小さいときに
は、第１群レンズでの色収差の補正に対する作用
が小さすぎ、目的とする波長の変動による収差の
変化を小さくする事ができなくなる。 Condition (1) is a condition for appropriate correction of chromatic aberration, and when |ν 1 −ν 2 | is smaller than the lower limit, the effect on the correction of chromatic aberration in the first group lens is too small, and the objective is not achieved. It is no longer possible to reduce changes in aberration due to changes in wavelength.
(2)の条件も(1)の条件と同様に色収差の補正に適
切にするための条件であり、｜r2｜が上限よりも
大きいときには、第１群レンズの正レンズと負レ
ンズによる色消しの作用が小さくなり、色収差の
補正が不足となり、目的とする波長の変動による
収差の変化を小さくする事ができなくなる。 Condition (2), like condition (1), is also a condition to make it suitable for correcting chromatic aberration, and when |r 2 | is larger than the upper limit, the color due to the positive and negative lenses of the first group lens is The erasing effect becomes smaller, chromatic aberration correction becomes insufficient, and it becomes impossible to reduce the change in aberration due to the desired wavelength variation.
(3)の条件は、第１群レンズの合成焦点距離を定
める事により、第２群レンズの焦点距離をも間接
的に定め、球面収差、コマ収差の補正を良好にす
るための条件であり、今ｆ／fIが下限よりも小さ
いときには、第１群レンズの負担は小さくなる
が、単レンズである第２群レンズの負担が大きく
なりすぎ、逆に上限よりも大きいときには、第１
群レンズの負担が大きすぎ、球面収差、コマ収差
の補正が困難となるばかりか、(1)，(2)の条件とも
関連して色収差の補正も困難となる。 Condition (3) is a condition that indirectly determines the focal length of the second group lens by determining the composite focal length of the first group lens, and improves the correction of spherical aberration and coma aberration. , when f/f I is smaller than the lower limit, the load on the first group lens becomes small, but the load on the second group lens, which is a single lens, becomes too large, and conversely, when it is larger than the upper limit, the load on the first group lens becomes small.
The load on the group lens is too large, making it difficult to correct spherical aberration and coma aberration, and also makes it difficult to correct chromatic aberration in conjunction with conditions (1) and (2).
さらに第２群レンズを両凸レンズとすると共
に、その光源側の面r4を非球面とする事により、
第２群レンズで発生する球面収差、コマ収差を小
さくでき、諸収差をさらに小さくする事ができる
ため、よりNA（開口数）の大きいレンズ、即ち
NAが0.5を越えるビデオデイスクや光書き込みを
行う光デイススクに用いることのできる対物レン
ズを提供する事ができる。 Furthermore, by making the second group lens a biconvex lens and making the surface r4 on the light source side an aspherical surface,
Spherical aberration and coma aberration occurring in the second group lens can be reduced, and various aberrations can be further reduced, so a lens with a larger NA (numerical aperture), i.e.
It is possible to provide an objective lens that can be used for video discs with NA exceeding 0.5 and optical discs that perform optical writing.
加えて、第２群レンズはデイスク側の面が凸と
なつていることから、当然のことながら射出瞳位
置をデイスク面より遠方にすることができるた
め、フオーカシングやトラツキング等の各種信号
を発生する光センサへの光がケラレることが少な
く、良好な各種信号が取り出せる光デイスクシス
テムを構成することができる。 In addition, since the second group lens has a convex surface on the disk side, the exit pupil position can be placed further away from the disk surface, so it is possible to generate various signals such as focusing and tracking. It is possible to configure an optical disk system in which the light to the optical sensor is less likely to be eclipsed and various good signals can be extracted.
ｆ 実施例
以下、本発明の実施例１、実施例２、実施例
３、実施例４の数値を全系合成焦点距離ｆ＝１に
おける数値で示す。f Example Hereinafter, numerical values of Example 1, Example 2, Example 3, and Example 4 of the present invention will be shown as numerical values at the total system composite focal length f=1.
なお、第２群レンズの光源側の面の非球面形状
は以下の式にて定義される。 Note that the aspherical shape of the light source side surface of the second group lens is defined by the following equation.
但し、Ｘは光軸と球面との交点において光軸に
垂直な平面よりの光軸方向への距離、ｈは光軸よ
り光軸垂直方向の距離、ｃは近軸の曲率（１／
ｒ）、Ｋは２次曲面係数、Aiは非球面係数である。 However, X is the distance in the optical axis direction from the plane perpendicular to the optical axis at the intersection of the optical axis and the spherical surface, h is the distance from the optical axis in the direction perpendicular to the optical axis, and c is the paraxial curvature (1/
r), K is a quadratic surface coefficient, and A i is an aspheric coefficient.
また、riは第ｉ面の曲率半数、diは第ｉ番目の
レンズ厚またはレンズ間隔、Niは第ｉ番目のレ
ンズの屈折率、νiは第ｉ番目のレンズのアツベ数
である。 In addition, r i is half the curvature of the i-th surface, d i is the i-th lens thickness or lens spacing, N i is the refractive index of the i-th lens, and ν i is the Atsube number of the i-th lens. .
〔実施例 １〕
ｆ＝1.000 NA＝0.53
r1＝3.7205 d1＝0.7052 N1／ν1＝1.77250／49.6
r2＝−0.7598 d2＝0.5882 N2／ν2＝1.84666／
23.9
r3＝−4.2769 d3＝0.2882
＊r4＝1.1191 d4＝0.6379 N3／ν3＝1.51633／
64.1
r5＝−0.7640
ν1―ν2＝25.7 ｆ／fI＝1.000／3.349＝0.299
＊r4は非球面で構成され、係数は以下のとお
り。[Example 1] f=1.000 NA=0.53 r 1 =3.7205 d 1 =0.7052 N 1 /ν 1 =1.77250/49.6 r 2 =−0.7598 d 2 =0.5882 N 2 /ν 2 =1.84666/
23.9 r 3 = −4.2769 d 3 = 0.2882 *r 4 = 1.1191 d 4 = 0.6379 N 3 /ν 3 = 1.51633/
64.1 r 5 = -0.7640 ν 1 - ν 2 = 25.7 f/f I = 1.000/3.349 = 0.299 *r 4 is composed of an aspheric surface, and the coefficients are as follows.
Ｋ＝−2.6680 A1＝０ A2＝−0.28311
A3＝−1.66390 A4＝−0.33836 A5＝−13.91960
〔実施例 ２〕
ｆ＝1.000 NA＝0.53
r1＝3.3494 d1＝0.6828 N1／ν1＝1.71300／53.8
r2＝−0.7715 d2＝0.5784 N2／ν2＝1.80518／
25.4
r3＝−3.6795 d3＝0.4038
＊r4＝1.0153 d4＝0.5882 N3／ν3＝1.51633／
64.1
r5＝−0.7809
ν1―ν2＝28.4 ｆ／fI＝1.000／3.318＝0.301
＊r4は非球面で構成され、係数は以下のとお
り。K = -2.6680 A 1 = 0 A 2 = -0.28311 A 3 = -1.66390 A 4 = -0.33836 A 5 = -13.91960 [Example 2] f = 1.000 NA = 0.53 r 1 = 3.3494 d 1 = 0.6828 N 1 / ν 1 = 1.71300/53.8 r 2 = −0.7715 d 2 = 0.5784 N 2 /ν 2 = 1.80518/
25.4 r 3 = −3.6795 d 3 = 0.4038 *r 4 = 1.0153 d 4 = 0.5882 N 3 /ν 3 = 1.51633/
64.1 r 5 = -0.7809 ν 1 - ν 2 = 28.4 f/f I = 1.000/3.318 = 0.301 *r 4 is composed of an aspheric surface, and the coefficients are as follows.
Ｋ＝−2.41700 A1＝０ A2＝−0.25325
A3＝−1.72490 A4＝−1.17487 A5＝−9.88444
〔実施例 ３〕
ｆ＝1.000 NA＝0.53
r1＝3.2108 d1＝0.6433 N1／ν1＝1.72916／54.7
r2＝−0.7955 d2＝0.5882 N2／ν2＝1.84666／
23.9
r3＝―3.4440 d3＝0.3758
＊r4＝1.0419 d4＝0.5882 N3／ν3＝1.51633／
64.1
r5＝−0.8122
ν1―ν2＝30.8 ｆ／fI＝1.000／3.168＝0.316
＊r4は非球面で構成され、係数は以下のとお
り。K = -2.41700 A 1 = 0 A 2 = -0.25325 A 3 = -1.72490 A 4 = -1.17487 A 5 = -9.88444 [Example 3] f = 1.000 NA = 0.53 r 1 = 3.2108 d 1 = 0.6433 N 1 / ν 1 = 1.72916/54.7 r 2 = −0.7955 d 2 = 0.5882 N 2 /ν 2 = 1.84666/
23.9 r 3 = -3.4440 d 3 = 0.3758 * r 4 = 1.0419 d 4 = 0.5882 N 3 /ν 3 = 1.51633/
64.1 r 5 = -0.8122 ν 1 - ν 2 = 30.8 f/f I = 1.000/3.168 = 0.316 *r 4 is composed of an aspheric surface, and the coefficients are as follows.
Ｋ＝−2.30290 A1＝０ A2＝−0.23252
A3＝−1.44759 A4＝−1.27730 A5＝−6.51423
〔実施例 ４〕
ｆ＝1.000 NA＝0.53
r1＝3.3989 d1＝0.4376 N1／ν1＝1.84666／23.9
r2＝0.8174 d2＝1.1764 N2／ν2＝1.72916／54.7
r3＝―4.3828 d3＝0.5294
＊r4＝1.3486 d4＝0.6171 N3／ν3＝1.58913／
61.0
r5＝−0.6736
｜ν1―ν2｜＝30.8 ｆ／fI＝1.000／3.794＝0.264
＊r4は非球面で構成され、係数は以下のとお
り。K = -2.30290 A 1 = 0 A 2 = -0.23252 A 3 = -1.44759 A 4 = -1.27730 A 5 = -6.51423 [Example 4] f = 1.000 NA = 0.53 r 1 = 3.3989 d 1 = 0.4376 N 1 / ν 1 = 1.84666/23.9 r 2 = 0.8174 d 2 = 1.1764 N 2 / ν 2 = 1.72916/54.7 r 3 = -4.3828 d 3 = 0.5294 *r 4 = 1.3486 d 4 = 0.6171 N 3 / ν 3 = 1. 58913/
61.0 r 5 = −0.6736 | ν 1 − ν 2 | = 30.8 f/f I = 1.000/3.794 = 0.264 *r 4 is composed of an aspheric surface, and the coefficients are as follows.
Ｋ＝−0.47950 A1＝０ A2＝−0.74708
A3＝−3.44288 A4＝8.22981 A5＝−87.94210
ｇ 効果
以上説明したように本発明は、２群３枚構成の
光デイスク用対物レンズにおいて、前記(1)から(3)
までの条件を満足して構成した事により、諸収差
（特に色収差）を良好に補正する事ができ、1μ程
度の分解能を持ち、さらに波長の変動による性能
劣化が非常に少ない、光デイスク用対物レンズを
提供できると共に、両凸レンズで、しかもその光
源側の面を非球面とした第２群レンズを用いたこ
とにより、NAが0.5を越えるNAの大きなレンズ
を得ることができるのに加えて、射出瞳位置をデ
イスク面より遠方に置くことができるので、各種
の信号を発生する光センサへの悪影響が少ないレ
ンズとすることができる。K = -0.47950 A 1 = 0 A 2 = -0.74708 A 3 = -3.44288 A 4 = 8.22981 A 5 = -87.94210 g Effects As explained above, the present invention provides an objective lens for an optical disk having three elements in two groups. , (1) to (3) above.
By satisfying the above conditions, it is possible to effectively correct various aberrations (especially chromatic aberration), and the objective for optical disks has a resolution of about 1μ, and there is very little performance deterioration due to wavelength fluctuations. In addition to being able to provide a lens with a large NA exceeding 0.5, by using a second group lens that is a biconvex lens and has an aspherical surface on the light source side. Since the exit pupil position can be placed farther away than the disk surface, it is possible to create a lens that has less adverse effects on the optical sensor that generates various signals.
第１図は実施例１のレンズ構成図、第２図は実
施例１の諸収差曲線図、第３図は実施例２のレン
ズ構成図、第４図は実施例２の諸収差曲線図、第
５図は実施例３のレンズ構成図、第６図は実施例
３の諸収差曲線図、第７図は実施例４のレンズ構
成図、第８図は実施例４の諸収差曲線図である。
1 is a diagram of the lens configuration of Example 1, FIG. 2 is a diagram of various aberration curves of Example 1, FIG. 3 is a diagram of the lens configuration of Example 2, and FIG. 4 is a diagram of various aberration curves of Example 2. Figure 5 is a lens configuration diagram of Example 3, Figure 6 is a diagram of various aberration curves of Example 3, Figure 7 is a diagram of lens configuration of Example 4, and Figure 8 is a diagram of various aberration curves of Example 4. be.
Claims (1)
正の焦点距離を有する第１群レンズと、正の焦点
距離を有する第２群レンズとから成る２群３枚構
成の光デイスク用対物レンズにおいて、 前記第１群レンズは、光源側から、正・負の接
合レンズあるいは負・正の接合レンズから成り、 前記第２群レンズは、その光源側の面を非球面
とした両凸レンズから成り、 かつ以下の諸条件を満足している事を特徴とす
る光デイスク用対物レンズ。 (1) ｜ν1―ν2｜＞20 (2) ｜r2｜＜ｆ (3) 0.5＞ｆ／fI＞0.1 ここでｆはレンズ全系の合成焦点距離、ν1―ν2
は第１群レンズを構成する２枚のレンズのアツベ
数の差、r2は第１群レンズの接合面の曲率半径、
fIは第１群レンズの合成焦点距離である。[Scope of Claims] 1. Light composed of three lenses in two groups, consisting of a first lens group consisting of a cemented lens of a positive lens and a negative lens and having a positive focal length, and a second group lens having a positive focal length. In the disk objective lens, the first group lens is composed of a positive/negative cemented lens or a negative/positive cemented lens from the light source side, and the second group lens has an aspherical surface on the light source side. An objective lens for optical disks comprising a biconvex lens and satisfying the following conditions. (1) ｜ν 1 ―ν 2 ｜＞20 (2) ｜r 2 ｜＜f (3) 0.5＞f/f I ＞0.1 Here, f is the composite focal length of the entire lens system, ν 1 －ν 2
is the difference in the Atsube numbers of the two lenses that make up the first group lens, r2 is the radius of curvature of the cemented surface of the first group lens,
f I is the composite focal length of the first lens group.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP15450086A JPS6310118A (en) | 1986-07-01 | 1986-07-01 | Lens for optical disk |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP15450086A JPS6310118A (en) | 1986-07-01 | 1986-07-01 | Lens for optical disk |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS6310118A JPS6310118A (en) | 1988-01-16 |
| JPH0140325B2 true JPH0140325B2 (en) | 1989-08-28 |
Family
ID=15585600
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP15450086A Granted JPS6310118A (en) | 1986-07-01 | 1986-07-01 | Lens for optical disk |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS6310118A (en) |
Families Citing this family (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH01284816A (en) * | 1988-05-12 | 1989-11-16 | Olympus Optical Co Ltd | Objective lens for optical pickup |
| FR2642883B1 (en) * | 1989-02-09 | 1995-06-02 | Asahi Optical Co Ltd | |
| 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 |
| US5491587A (en) * | 1989-02-28 | 1996-02-13 | Asahi Kogaku Kogyo Kabushiki Kaisha | Collimating lens for optical system using semiconductor laser |
| US6788473B2 (en) | 2000-12-07 | 2004-09-07 | Samsung Electronics Co., Ltd. | Objective lens device for correcting chromatic aberration and optical pickup employing the same |
Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5118557A (en) * | 1974-07-22 | 1976-02-14 | Olympus Optical Co | Bideo deisukuyotaibutsurenzu |
| JPS554068A (en) * | 1978-06-26 | 1980-01-12 | Olympus Optical Co Ltd | Focusing lens for video disc |
| JPS6191612A (en) * | 1984-10-12 | 1986-05-09 | Tokinaa Kogaku Kk | Objective for optical disk |
-
1986
- 1986-07-01 JP JP15450086A patent/JPS6310118A/en active Granted
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5118557A (en) * | 1974-07-22 | 1976-02-14 | Olympus Optical Co | Bideo deisukuyotaibutsurenzu |
| JPS554068A (en) * | 1978-06-26 | 1980-01-12 | Olympus Optical Co Ltd | Focusing lens for video disc |
| JPS6191612A (en) * | 1984-10-12 | 1986-05-09 | Tokinaa Kogaku Kk | Objective for optical disk |
Also Published As
| Publication number | Publication date |
|---|---|
| JPS6310118A (en) | 1988-01-16 |
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