JPS6326364B2 - - Google Patents
Info
- Publication number
- JPS6326364B2 JPS6326364B2 JP10109680A JP10109680A JPS6326364B2 JP S6326364 B2 JPS6326364 B2 JP S6326364B2 JP 10109680 A JP10109680 A JP 10109680A JP 10109680 A JP10109680 A JP 10109680A JP S6326364 B2 JPS6326364 B2 JP S6326364B2
- Authority
- JP
- Japan
- Prior art keywords
- lens
- curvature
- radius
- condition
- spherical aberration
- 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
Links
- 230000005499 meniscus Effects 0.000 claims description 2
- 239000002131 composite material Substances 0.000 claims 1
- 230000004075 alteration Effects 0.000 description 17
- 239000006059 cover glass Substances 0.000 description 6
- 238000010586 diagram Methods 0.000 description 2
- 238000000034 method Methods 0.000 description 2
- 230000003287 optical effect Effects 0.000 description 2
- 206010010071 Coma Diseases 0.000 description 1
- 230000004907 flux Effects 0.000 description 1
- 238000002834 transmittance Methods 0.000 description 1
Classifications
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B9/00—Optical objectives characterised both by the number of the components and their arrangements according to their sign, i.e. + or -
- G02B9/04—Optical objectives characterised both by the number of the components and their arrangements according to their sign, i.e. + or - having two components only
Landscapes
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Optics & Photonics (AREA)
- Lenses (AREA)
Description
【発明の詳細な説明】
本発明はビデオデイスク用対物レンズに関する
もので、特にレンズを振らせてトラツキングを行
なう方式のビデオデイスクピツクアツプ用として
使用されるレンズに関するものである。DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an objective lens for a video disk, and more particularly to a lens used for video disk pickup in which tracking is performed by swinging the lens.
周知のように、ビデオデイスクの再生用に使用
される対物レンズは高密度に記録された信号を読
みとるために1μの高分解能を保償する必要があ
るが、信号位置とレンズの光軸が合うように対物
レンズを振らせてトラツキングする方式において
は、レンズの光軸上の性能を問題とし、軸外の性
能はほとんど無関係である。 As is well known, the objective lens used for video disc playback must guarantee a high resolution of 1μ in order to read the signals recorded in high density, but the optical axis of the lens must match the signal position. In this method of tracking by swinging the objective lens, the performance of the lens on the optical axis is the issue, and the off-axis performance is almost irrelevant.
しかし、対物レンズを振らせてトラツキングす
る方式においては、対物レンズは敏感に応答する
ことを求められるため、極めて小形軽量であるこ
とが要求される。 However, in the method of tracking by swinging the objective lens, the objective lens is required to respond sensitively and is therefore required to be extremely small and lightweight.
対物レンズを小形軽量にするには、レンズの構
成枚数を少なくすることが有効であり、このこと
は光の透過率を高めるためにも、更にコストの低
廉化のためにも強く望まれることである。 In order to make an objective lens smaller and lighter, it is effective to reduce the number of lens elements, which is highly desirable in order to increase light transmittance and further reduce costs. be.
しかし、従来のビデオデイスク用対物レンズ
は、レンズを３枚以上使用して構成するのが普通
であつた。 However, conventional objective lenses for video discs have generally been constructed using three or more lenses.
レンズの構成枚数が２枚以下のビデオデイスク
用レンズとしては、米国特許第4027952号と特開
昭55−45084号とが知られているが、これらはい
ずれもレンズの収差を補正するために非球面を採
用している。非球面を用いず、レンズ２枚以下で
構成したビデオデイスク用レンズは現在のところ
知られていない。 U.S. Pat. No. 4,027,952 and Japanese Patent Application Laid-Open No. 1984-45084 are known as lenses for video discs with two or less lens elements, but both of these use non-contact lenses to correct lens aberrations. It uses a spherical surface. At present, there is no known lens for video discs that does not use an aspherical surface and is composed of two or fewer lenses.
本発明の目的は、従来知られていなかつた非球
面を用いず、しかもレンズ２枚という少ない構成
枚数で、小形軽量かつ高分解能なビデオデイスク
用対物レンズを提供することにある。 An object of the present invention is to provide a compact, lightweight, and high-resolution objective lens for a video disk that does not use an aspheric surface, which has not been known in the past, and has a small number of lenses, ie, two lenses.
第１図に示すように、本発明の対物レンズ１０
は、物界側から順に、第１レンズ１は曲率の強い
面を物界側に向けた正レンズ、第２レンズ２は曲
率の強い面を物界側に向けた正のメニスカスレン
ズからなる２群２枚構成にして、全系の合成焦点
距離をｆ、第１レンズ１の物界側の面の曲率半径
をr1、同じく像界側の面の曲率半径をr2、第２レ
ンズ２の物界側の面の曲率半径をr3、同じく像界
側の面の曲率半径をr4、第１レンズ１の屈折率を
n1、第２レンズ２の屈折率をn2、第２レンズ２の
焦点距離をf2とする時、
(1) n1＋n2／２＞1.7
(2) −0.3＜r1／r2＜0.3
(3) 0.2f2＜r3＜0.5f2
(4) 0.7f＜r4＜1.4f
なる条件を満足するレンズ系である。 As shown in FIG. 1, an objective lens 10 of the present invention
In order from the object world side, the first lens 1 is a positive lens with a surface with a strong curvature facing the object world side, and the second lens 2 is a positive meniscus lens with a surface with a strong curvature facing the object world side. The group is composed of two elements, and the combined focal length of the entire system is f, the radius of curvature of the surface on the object world side of the first lens 1 is r 1 , the radius of curvature of the surface on the image field side is r 2 , and the second lens 2 The radius of curvature of the surface on the object side is r 3 , the radius of curvature of the surface on the image field side is r 4 , and the refractive index of the first lens 1 is
When n 1 , the refractive index of the second lens 2 is n 2 , and the focal length of the second lens 2 is f 2 , (1) n 1 +n 2 /2>1.7 (2) −0.3<r 1 /r 2 This is a lens system that satisfies the following conditions: <0.3 (3) 0.2f 2 <r 3 <0.5f 2 (4) 0.7f < r 4 <1.4f.
第１図のレンズ系の左方から平行に入射したレ
ーザー光束（波長780.0nｍ）は対物レンズ１０を
透過し、収束光束となつて信号面を保護するカバ
ーガラス３に入射する。この入射光束はカバーガ
ラス３で正の球面収差を発生させるため、対物レ
ンズ１０で生ずる負の球面収差を小さく押えてお
けば、対物レンズ１０で生ずる球面収差とカバー
ガラス３で生ずる球面収差が打ち消し合つて、球
面収差を補正することができる。 A laser beam (wavelength: 780.0 nm) that enters in parallel from the left side of the lens system in FIG. 1 passes through the objective lens 10, becomes a convergent beam, and enters the cover glass 3 that protects the signal surface. This incident light flux generates positive spherical aberration on the cover glass 3, so if the negative spherical aberration generated on the objective lens 10 is kept small, the spherical aberration generated on the objective lens 10 and the spherical aberration generated on the cover glass 3 can be canceled out. At the same time, spherical aberration can be corrected.
対物レンズ１０で発生する球面収差を小さく押
えるためには、レンズの屈折率を大きくして、面
の曲率半径を大きくしておくのがよい。条件(1)は
このために設けられた条件であり、この条件が破
られると対物レンズ１０で発生する球面収差を小
さく押えることができない。 In order to suppress the spherical aberration generated in the objective lens 10, it is preferable to increase the refractive index of the lens and increase the radius of curvature of the surface. Condition (1) is a condition established for this purpose, and if this condition is violated, the spherical aberration generated in the objective lens 10 cannot be kept small.
条件(2)は第１レンズ１の球面収差の発生を小さ
く押えるための条件であり、この条件の上限ある
いは下限を越えると第１面あるいは第２面の曲率
半径が小さくなり、球面収差が大きく発生して、
全系での補正が不可能となる。 Condition (2) is a condition for suppressing the occurrence of spherical aberration in the first lens 1. If the upper or lower limit of this condition is exceeded, the radius of curvature of the first or second surface becomes small, and the spherical aberration increases. Occurred,
Correction for the entire system becomes impossible.
条件(3)は第２レンズ２で発生する球面収差を小
さく押えるための条件であり、この下限を越える
と第３面の曲率半径が小さくなりすぎて、第３面
で球面収差が大きく発生する。条件(3)の上限を越
えると、第２レンズ２のパワーの負担が第４面に
かかつてきて、第４面で球面収差が大きく発生
し、全系で補正不可能となる。 Condition (3) is a condition for keeping the spherical aberration generated in the second lens 2 small; if this lower limit is exceeded, the radius of curvature of the third surface becomes too small, and a large spherical aberration occurs on the third surface. . If the upper limit of condition (3) is exceeded, the burden of the power of the second lens 2 will be applied to the fourth surface, and a large spherical aberration will occur on the fourth surface, making it impossible to correct it in the entire system.
条件(4)は上記条件(1)，(2)，(3)のもとで各面で発
生するコマ収差を補正し、正弦条件を良好に保つ
ための条件である。この条件(4)の下限を越えると
正弦条件は補正過剰となり、上限を越えると正弦
条件は補正不足となる。 Condition (4) is a condition for correcting coma aberration occurring on each surface under conditions (1), (2), and (3) above, and maintaining a good sine condition. When the lower limit of this condition (4) is exceeded, the sine condition becomes over-corrected, and when the upper limit is exceeded, the sine condition becomes under-corrected.
次に本発明の実施例を示す。 Next, examples of the present invention will be shown.
実施例 １
r1＝1.9065
d1＝0.3317 n1＝1.73818 ν1＝25.7
r2＝−57.6283
d2＝0.0353
r3＝0.6758
d3＝0.2861 n2＝1.81906 ν2＝37.3
r4＝1.0966
ｆ＝1.0 f2＝1.6461 N.A.＝0.45
ｗ＝0.3840 ｔ＝0.4400
（n1＋n2）／２＝1.779 r1／r2＝−0.033
r3／f2＝0.411 r4／ｆ＝1.097
実施例 ２
r1＝1.9831
d1＝0.3480 n1＝1.72205 ν1＝28.3
r2＝−8.5644
d2＝0.0160
r3＝0.6408
d3＝0.2834 n2＝1.81906 ν2＝37.3
r4＝0.8854
ｆ＝1.0 f2＝1.8608 N.A.＝0.45
ｗ＝0.3760 ｔ＝0.4400
（n1＋n2）／２＝1.771 r1／r2＝−0.232
r3／f2＝0.344 r4／ｆ＝0.885
実施例 ３
r1＝1.5894
d1＝0.2400 n1＝1.79318 ν1＝40.7
r2＝−19.2667
d2＝0.0160
r3＝0.6248
d3＝0.2800 n2＝1.79318 ν2＝40.7
r4＝0.7331
ｆ＝1.0 f2＝2.4873 N.A.＝0.45
ｗ＝0.3660 ｔ＝0.4400
（n1＋n2）／２＝1.793 r1／r2＝−0.082
r3／f2＝0.251 r4／ｆ＝0.733
実施例 ４
r1＝1.5483
d1＝0.3515 n1＝1.67500 ν1＝31.2
r2＝−34.1058
d2＝0.0160
r3＝0.6597
d3＝0.2799 n2＝1.79318 ν2＝40.7
r4＝0.9758
ｆ＝1.0 f2＝1.8451 N.A.＝0.45
ｗ＝0.3699 ｔ＝0.4400
（n1＋n2）／２＝1.734 r1／r2＝−0.045
r3／f2＝0.358 r4／ｆ＝0.976
実施例 ５
r1＝1.3450
d1＝0.2925 n1＝1.81906 ν1＝37.3
r2＝5.2000
d2＝0.0160
r3＝0.7237
d3＝0.2795 n2＝1.81906 ν2＝37.3
r4＝1.1400
ｆ＝1.0 f2＝1.8576 N.A.＝0.45
ｗ＝0.3759 ｔ＝0.4400
（n1＋n2）／２＝1.819 r1／r2＝0.259
r3／f2＝0.390 r4／ｆ＝1.140
実施例 ６
r1＝2.0070
d1＝0.3453 n1＝1.81906 ν1＝37.3
r2＝26.5339
d2＝0.0396
r3＝0.6858
d3＝0.2935 n2＝1.81906 ν2＝37.3
r4＝1.1865
ｆ＝1.0 f2＝1.5698 N.A.＝0.50
ｗ＝0.3800 ｔ＝0.4400
（n1＋n2）／２＝1.819 r1／r2＝0.076
r3／f2＝0.437 r4／ｆ＝1.187
実施例 ７
r1＝1.7603
d1＝0.1917 n1＝1.81948 ν1＝37.2
r2＝9.7869
d2＝0.0208
r3＝0.7376
d3＝0.3251 n2＝1.81948 ν2＝37.2
r4＝1.2986
ｆ＝1.0 f2＝1.6526 N.A.＝0.50
ｗ＝0.3832 ｔ＝0.4584
（n1＋n2）／２＝1.819 r1／r2＝0.180
r3／f2＝0.446 r4／ｆ＝1.299
ただし、r1，r2，r3，r4はレンズの各面の曲率
半径、d1，d2，d3は各レンズの肉厚および空気間
隔、n1，n2は各レンズの波長780.0nｍの光に対す
る屈折率、ν1，ν2は各レンズのｄ線に対するアツ
ベ数、ｆは全系の焦点距離、f2は第２レンズの焦
点距離、ｗは作動距離、ｔはカバーガラスの厚さ
である。Example 1 r 1 = 1.9065 d 1 = 0.3317 n 1 = 1.73818 ν 1 = 25.7 r 2 = −57.6283 d 2 = 0.0353 r 3 = 0.6758 d 3 = 0.2861 n 2 = 1.81906 ν 2 = 37.3 r 4 =1.0966f= 1.0 f 2 = 1.6461 NA = 0.45 w = 0.3840 t = 0.4400 (n 1 + n 2 ) / 2 = 1.779 r 1 / r 2 = -0.033 r 3 / f 2 = 0.411 r 4 / f = 1.097 Example 2 r 1 ＝1.9831 d 1 ＝0.3480 n 1 ＝1.72205 ν 1 ＝28.3 r 2 ＝−8.5644 d 2 ＝0.0160 r 3 ＝0.6408 d 3 ＝0.2834 n 2 ＝1.81906 ν 2 ＝37.3 r 4 ＝0.8854 f =1.0 f2 =1.8608 NA=0.45 w=0.3760 t=0.4400 ( n1 + n2 )/2=1.771 r1 / r2 =-0.232 r3 / f2 =0.344 r4 /f=0.885 Example 3 r1 =1.5894 d1 = 0.2400 n 1 = 1.79318 ν 1 = 40.7 r 2 = −19.2667 d 2 = 0.0160 r 3 = 0.6248 d 3 = 0.2800 n 2 = 1.79318 ν 2 = 40.7 r 4 = 0.7331 f = 1.0 f 2 = 2.4 873 NA=0.45 w= 0.3660 t=0.4400 ( n1 + n2 )/2=1.793 r1 / r2 =-0.082 r3 /f2=0.251 r4/ f =0.733 Example 4 r1 =1.5483 d1 =0.3515 n1 =1.67500 ν 1 = 31.2 r 2 = −34.1058 d 2 = 0.0160 r 3 = 0.6597 d 3 = 0.2799 n 2 = 1.79318 ν 2 = 40.7 r 4 = 0.9758 f = 1.0 f 2 = 1.8451 NA = 0.45 w = 0.3699 t=0.4400 ( n 1 + n 2 )/2 = 1.734 r 1 / r 2 = -0.045 r 3 / f 2 = 0.358 r 4 / f = 0.976 Example 5 r 1 = 1.3450 d 1 = 0.2925 n 1 = 1.81906 ν 1 = 37.3 r 2 = 5.2000 d 2 = 0.0160 r 3 = 0.7237 d 3 = 0.2795 n 2 = 1.81906 ν 2 = 37.3 r 4 = 1.1400 f = 1.0 f 2 = 1.8576 NA = 0.45 w = 0.3759 t = 0.4400 (n 1 +n 2 )/ 2 = 1.819 R 1 / R 2 = 0.259 R 3 / F 2 = 0.390 R 4 / F =1.140 Example 6 R 1 = 2.0070 D 1 = 0.3453 N 1 = 1.81906 ν 1 = 37.3 R 2 = 26.5339 D 2 = 0.0396 r 3 = 0.6858 d 3 = 0.2935 n 2 = 1.81906 ν 2 = 37.3 r 4 = 1.1865 f = 1.0 f 2 = 1.5698 NA = 0.50 w = 0.3800 t = 0.4400 (n 1 + n 2 )/2 = 1.819 r 1 /r 2 = 0.076 r 3 /f 2 = 0.437 r 4 /f = 1.187 Example 7 r 1 = 1.7603 d 1 = 0.1917 n 1 = 1.81948 ν 1 = 37.2 r 2 = 9.7869 d 2 = 0.0208 r 3 = 0.7376 d 3 = 0.3251 n 2 = 1.81948 ν 2 = 37.2 r 4 = 1.2986 f = 1.0 f 2 = 1.6526 NA = 0.50 w = 0.3832 t = 0.4584 (n 1 + n 2 )/2 = 1.819 r 1 / r 2 = 0.180 r 3 /f 2 = 0.446 r 4 / f = 1.299 where r 1 , r 2 , r 3 , r 4 are the curvature radius of each surface of the lens, d 1 , d 2 , d 3 are the wall thickness and air spacing of each lens, n 1 and n 2 are the refractive index of each lens for light with a wavelength of 780.0 nm, ν 1 and ν 2 are the Atbe numbers of each lens for the d-line, f is the focal length of the entire system, f 2 is the focal length of the second lens, w is the working distance and t is the thickness of the cover glass.
なお、上記実施例でカバーガラスの波長780.0n
ｍの光に対する屈折率は1.51である。 In addition, in the above example, the wavelength of the cover glass was 780.0n.
The refractive index for light of m is 1.51.
以上示した実施例によれば、第２図乃至第８図
の収差図からわかるように球面収差、正弦条件が
良好に補正された作動距離0.36f〜0.38fのビデオ
デイスク用対物レンズが得られる。また、ｆ＝
2.4mmで枠をも含めた重さが0.07ｇとなり、極め
て軽量である。 According to the embodiments shown above, as can be seen from the aberration diagrams in FIGS. 2 to 8, it is possible to obtain an objective lens for a video disk with a working distance of 0.36f to 0.38f, in which spherical aberration and sine conditions are well corrected. . Also, f=
It is 2.4mm and weighs 0.07g including the frame, making it extremely lightweight.
第１図は実施例１のレンズの断面図、第２図乃
至第８図は夫々実施例１乃至実施例７の収差図で
ある。
１…第１レンズ、２…第２レンズ、３…カバー
ガラス、１０…対物レンズ。
FIG. 1 is a sectional view of the lens of Example 1, and FIGS. 2 to 8 are aberration diagrams of Examples 1 to 7, respectively. DESCRIPTION OF SYMBOLS 1...First lens, 2...Second lens, 3...Cover glass, 10...Objective lens.
Claims (1)
を物界側に向けた正レンズ、第２レンズは曲率の
強い面を物界側に向けた正のメニスカスレンズか
らなる２群２枚構成にして、全系の合成焦点距離
をｆ、第１レンズの物界側の面の曲率半径をr1，
第１レンズの像界側の面の曲率半径をr2、第２レ
ンズの物界側の面の曲率半径をr3、第２レンズの
像界側の面の曲率半径をr4、第１レンズの屈折率
をn1、第２レンズの屈折率をn2、第２レンズの焦
点距離をf2とするとき、 (1) n1＋n2／２＞1.7 (2) −0.3＜r1／r2＜0.3 (3) 0.2f2＜r3＜0.5f2 (4) 0.7f＜r4＜1.4f なる条件を満足するビデオデイスク用対物レン
ズ。[Claims] 1. In order from the object world side, the first lens is a positive lens with a surface with a strong curvature facing the object world side, and the second lens is a positive meniscus lens with a surface with a strong curvature facing the object world side. The composite focal length of the entire system is f, the radius of curvature of the object-world side surface of the first lens is r 1 ,
The radius of curvature of the surface on the image field side of the first lens is r 2 , the radius of curvature of the surface on the object world side of the second lens is r 3 , the radius of curvature of the surface on the image field side of the second lens is r 4 , the radius of curvature of the surface on the image field side of the second lens is r 4 , When the refractive index of the lens is n 1 , the refractive index of the second lens is n 2 , and the focal length of the second lens is f 2 , (1) n 1 +n 2 /2>1.7 (2) −0.3<r 1 An objective lens for video discs that satisfies the following conditions: /r 2 <0.3 (3) 0.2f 2 <r 3 <0.5f 2 (4) 0.7f < r 4 <1.4f.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP10109680A JPS5726815A (en) | 1980-07-25 | 1980-07-25 | Objective lens for video disk |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP10109680A JPS5726815A (en) | 1980-07-25 | 1980-07-25 | Objective lens for video disk |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS5726815A JPS5726815A (en) | 1982-02-13 |
| JPS6326364B2 true JPS6326364B2 (en) | 1988-05-30 |
Family
ID=14291554
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP10109680A Granted JPS5726815A (en) | 1980-07-25 | 1980-07-25 | Objective lens for video disk |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS5726815A (en) |
Families Citing this family (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3220408C2 (en) * | 1982-05-29 | 1985-05-15 | Optische Werke G. Rodenstock, 8000 München | Scanning lens |
| JPS58219511A (en) * | 1982-06-16 | 1983-12-21 | Olympus Optical Co Ltd | Lens for optical disc |
| JPS607413A (en) * | 1983-06-28 | 1985-01-16 | Matsushita Electric Ind Co Ltd | Lens for converging beam |
| JPS60247212A (en) * | 1984-05-14 | 1985-12-06 | Alps Electric Co Ltd | Objective lens for optical pickup |
| JPH07119889B2 (en) * | 1985-09-20 | 1995-12-20 | コニカ株式会社 | Condensing optical system for recording / reproducing optical system of optical information recording medium |
| JPS62245212A (en) * | 1986-04-18 | 1987-10-26 | Konika Corp | Collimator lens |
-
1980
- 1980-07-25 JP JP10109680A patent/JPS5726815A/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| JPS5726815A (en) | 1982-02-13 |
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