JPS63273807A - Aspherical single lens - Google Patents

Abstract

PURPOSE:To obtain a small-sized, lightweight objective for video disk reproduction by using specific aspherical surfaces for both 1st and 2nd surfaces. CONSTITUTION:The 1st and 2nd surfaces are both aspherical, and those aspherical surfaces are expressed by an equation I defining (h) as the height (h) from the optical axis, (x) as the distance of a corresponding aspherical surface peak from a tangential plane, (d) as the curvature at the aspherical surface peak, (k) as an ellipse constant, and A-D as aspherical surface constants and have various elements shown by II. In the equalities II, d1 is the thickness of a lens, d2 the thickness of a disk, N1 the refractive index of the lens 1 corresponding 780nm, and N2 the refractive index of the disk corresponding to 780nm. Consequently, a small-sized, lightweight lens with high performance is obtained as the objective for video disk reproduction.

Description

【発明の詳細な説明】 〔産業上の利用分野〕 この発明は、ビデオディスク再生用対物レンズ等として
使用される大口径比非球面単レンズに関する。DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a large aperture ratio aspheric single lens used as an objective lens for video disk reproduction.

〔従来の技術〕[Conventional technology]

この発明で目的とするビデオディスク再生用対物レンズ
は、高い解像力が要求され又収差も回折限界内に収まる
程度に補正されている必要がある。The objective lens for video disk reproduction, which is the object of the present invention, is required to have high resolving power, and aberrations must be corrected to the extent that they fall within the diffraction limit.

又ビデオディスクにおいてはトラッキングのために対物
レンズ自体を動かす方式がとられることがあり、対物レ
ンズは極めて小型軽量でなければならずレンズ枚数を少
なくする必要がある。Furthermore, in video discs, a method is sometimes used in which the objective lens itself is moved for tracking purposes, and the objective lens must be extremely small and lightweight, and the number of lenses must be reduced.

そのためにビデオディスク再生用対物レンズは、単レン
ズにし、しかも前に述べたレンズ性能を得るために球面
単レンズでは無理で、非球面単レンズにする必要がある
。しかも非球面単レンズは製作が容易でない。For this purpose, the objective lens for video disk reproduction must be a single lens, and in order to obtain the lens performance described above, it is impossible to use a spherical single lens; it is necessary to use an aspherical single lens. Moreover, aspherical single lenses are not easy to manufacture.

〔発明が解決しようとする問題点〕[Problem that the invention seeks to solve]

この発明は、前に述べたような要求を満足するビデオデ
ィスク再生用対物レンズ等に利用する非球面単レンズを
提供することを目的とするものである。An object of the present invention is to provide an aspherical single lens for use in an objective lens for video disc reproduction, etc., which satisfies the above-mentioned requirements.

〔問題点を解決するための手段〕[Means for solving problems]

このような問題を解決するためには、両面がいずれも非
球面であって、非球面のような特殊な形状であっても容
易に多量に生産が可能なようにプラスチックの非球面単
レンズにした。In order to solve this problem, we developed a plastic aspherical single lens that has both aspherical surfaces and can be easily produced in large quantities even with a special shape such as an aspherical surface. did.

即ちこの発明の単レンズは、第１図に示すような断面形
状の第１面および第２面がいずれも非球面であって、こ
れらの非球面はｈを光軸からの高さ、Ｘを対応する非球
面頂点の接平面からの距離。That is, in the single lens of the present invention, the first and second surfaces of the cross-sectional shape shown in FIG. 1 are both aspherical surfaces, and these aspherical surfaces have h as the height from the optical axis and Distance from the tangent plane of the corresponding aspheric vertex.

Ｃを非球面頂点の曲率、ｋを円錐定数、Ａ、Ｂ。C is the curvature of the aspherical apex, k is the conic constant, A, B.

Ｃ，Ｄを非球面係数とすると次の式で表わされる更にこ
の発明の単レンズは次の諸元を有している。When C and D are aspherical coefficients, the single lens of the present invention is expressed by the following equation.Furthermore, the single lens of the present invention has the following specifications.

ｆ　＝　４．５０　、Ｎ　Ａ　＝　０．４５　、ＷＤ　
＝　１．９３７ｒ　、　　＝−２−＝　２．７８４３２
３　、　　ｋ１＝　−１，１２２８２■ Ａ　　＝３．３５７８？ｌＸ１０　　、　Ｂ１＝５．５
９３１８１Ｘ１０Ｃ＝　−５，０７５８０２Ｘ　１０　
　　、Ｄ　１＝　０ｒ、、　＝−Ｅ　　＝−８，３０９
８４８、に２＝−２，１４９８３Ｘ　１０Ａ　　＝Ｏ，
Ｂ１　＝０．Ｃ１＝０．Ｄ、＝Ｏｄ　　＝３．３６０８
　、ｄ２＝１．２　、　　Ｎ１＝１．４８８０１Ｎ　は
レンズエの７８０ｎｍにおける屈折率、Ｎ２はディスク
２の７８０ｎｍにおける屈折率。f = 4.50, NA = 0.45, WD
= 1.937r, =-2-= 2.78432
3, k1=-1,12282■A=3.3578? lX10, B1=5.5
93181X10C=-5,075802X 10
, D 1= 0r, , =-E =-8,309
848, 2=-2,14983X 10A=O,
B1=0. C1=0. D,=Od=3.3608
, d2=1.2, N1=1.48801N is the refractive index of Lensue at 780 nm, and N2 is the refractive index of disk 2 at 780 nm.

この発明の非球面単レンズは、ＮＡが０．４５で非常に
大きく、差動距離が１．９３７で比較的大であり、上記
のように両面非球面で屈折率が１．４８８０１のプラス
チック材料（例えばアクリル樹脂）により射出成形等の
成形手段にて製造される。The aspherical single lens of this invention has a very large NA of 0.45, a relatively large differential distance of 1.937, and is made of plastic material with aspherical surfaces on both sides and a refractive index of 1.48801 as described above. (for example, acrylic resin) using a molding method such as injection molding.

この発明の非球面単レンズの収差は第２図〜第４図に示
した。波面収差（ｒｍｓ）は、像高が０テ０．００５４
人、　０．０７−１１’０．０２１８λ、０．１テｏ、
０３５０入である。The aberrations of the aspherical single lens of this invention are shown in FIGS. 2 to 4. Wavefront aberration (rms) is 0.0054 when the image height is 0.
Person, 0.07-11'0.0218λ, 0.1 Teo,
It comes in 0350 pieces.

この発明の非球面単レンズは、収差曲線図や波面収差か
ら明らかなようにすぐれたレンズである〔発明の効果〕 この発明では、ビデオディスク用対物レンズ等で要求さ
れる要件である小型軽量で高い性能のレンズで、しかも
プラスチック製で製造が簡単で多量生産に適している。The aspheric single lens of the present invention is an excellent lens as is clear from the aberration curve diagram and wavefront aberration. [Effects of the Invention] The present invention has achieved a compact and lightweight lens, which is a requirement for objective lenses for video discs, etc. It is a high-performance lens, and since it is made of plastic, it is easy to manufacture and suitable for mass production.

【図面の簡単な説明】[Brief explanation of the drawing]

第１図は本発明の構成図、第２図は本発明のレンズの球
面収差及び正弦条件違反量、第３図は非点収差、第４図
は横収差。FIG. 1 is a configuration diagram of the present invention, FIG. 2 is a spherical aberration and amount of violation of the sine condition of the lens of the present invention, FIG. 3 is astigmatism, and FIG. 4 is lateral aberration.

Claims (1)

【特許請求の範囲】 第１面および第２面がいずれも非球面で、ｈを光軸から
の高さ、ｘを光軸からの高さｈの非球面頂点の接平面か
らの距離、ｃを非球面頂点の曲率、ｋを円錐定数、Ａ、
Ｂ、Ｃ、Ｄを非球面係数として、非球面が式 ｘ＝（ｃｈ＾２／｛１＋√［１−（１＋ｋ）ｃ＾２ｈ＾
２］｝）＋Ａｈ＾４＋Ｂｈ＾６＋Ｃｈ＾８＋Ｄｈ＾１＾
０で表わされ、次の諸元を持つ非球面単レンズ。 ｒ＿１＝１／ｃ＿１＝２．７６４３２３、ｋ＿１＝−１
．１２２８２Ａ＿１＝３．３５７８７１×１０＾−＾３
、Ｂ＿１＝５．５９３１６１×１０＾−＾５Ｃ＿１＝−
５．０７５８０２×１０＾−＾６、Ｄ＿１＝０ｒ＿２＝
１／ｃ＿２＝−６．３０９８４８、ｋ＿２＝−２．１４
９８３×１０Ａ＿２＝０、Ｂ＿２＝０、Ｃ＿２＝０、Ｄ
＿２＝０ｄ＿１＝３．３６０６、ｄ＿２＝１．２０、Ｎ
＿１＝１．４８６０１Ｎ＿２＝１．５５ （ｄ＿１はレンズの厚さ、ｄ＿２はディスクの厚さ、Ｎ
＿１は７８０ｎｍにおけるレンズの屈折率Ｎ＿２は７８
０ｎｍにおけるディスクの屈折率）[Claims] Both the first surface and the second surface are aspheric surfaces, where h is the height from the optical axis, x is the distance from the tangential plane of the apex of the aspheric surface at the height h from the optical axis, and c is the curvature of the aspherical vertex, k is the conic constant, A,
Let B, C, and D be aspherical coefficients, and the aspherical surface is expressed by the formula x = (ch^2/{1+√[1-(1+k)c^2h^
2]})+Ah^4+Bh^6+Ch^8+Dh^1^
An aspheric single lens represented by 0 and having the following specifications. r_1=1/c_1=2.764323, k_1=-1
．． 12282A_1=3.357871×10^-^3
,B_1=5.593161×10^-^5C_1=-
5.075802×10^-^6, D_1=0r_2=
1/c_2=-6.309848, k_2=-2.14
983×10A_2=0, B_2=0, C_2=0, D
_2=0d_1=3.3606, d_2=1.20, N
_1=1.48601N_2=1.55 (d_1 is the thickness of the lens, d_2 is the thickness of the disk, N
_1 is the refractive index of the lens at 780 nm N_2 is 78
refractive index of the disk at 0 nm)