Title:
LENS FOR OPTICAL RECORDING AND REPRODUCING DEVICE
Document Type and Number:
Japanese Patent JPH01161308
Kind Code:
A
Abstract:
PURPOSE:To constitute the title lens of tow lenses in two groups and to set up NA to >=0.5 by using an optical axial direction refractive index distribution type medium as a light source side lens material. CONSTITUTION:The title lens is constituted of two single lenses 3, 4 and a medium with a uniform refractive index is used for the image side lens 4. The one side of the light source side lens 3 is formed as a plane symmetrical about the optical axis, the other face is formed as a convex shape symmetrical about the optical axis and the optical axis direction refractive index distribution material is used as the lens medium. When it is defined that the intersecting point between the convex face of the lens 3 and the optical axis is an origin and the length of the optical axis in the thickness direction is Z, 0<=Z<=Zs is formed, provided that refractive index distribution n(Z) in the optical axis direction satisfies the condition of inequality I in the range of 0.01<=Zs/Zo<=1. (Zo: thickness of the medium on the optical axis, Zs: thickness on the optical axis required by refractive index distribution, no: refractive index at Z=0, and k: constant). Thus, a bright optical system with 0.50-0.55 NA can be constituted of two lenses.
Inventors:
KIKKO SHIGEO
Application Number:
JP32105587A
Publication Date:
June 26, 1989
Filing Date:
December 18, 1987
Export Citation:
Assignee:
NIPPON SHEET GLASS CO LTD
International Classes:
G11B7/135; G02B9/06; G02B13/00; (IPC1-7): G02B9/06; G02B13/00; G11B7/135
Attorney, Agent or Firm:
Ohno Seiichi