IMAGE PICKUP LENS

Japanese Patent JP3311317

B2

PROBLEM TO BE SOLVED: To secure necessary performance by a smaller number of constituting lenses by making the paraxial radius of curvature of the 1st surface of an image-formation lens and the axial thickness of the same satisfy a specified condition.
SOLUTION: This lens is equipped with the image-formation lens 10 and a correction lens 20 which is arranged on the image side of the lens 10 and whose both surfaces are aspherical, and satisfies 0.3<r1/d1<1.0 assuming that the paraxial radius of curvature of the 1st surface of the lens 10 is r1 and the axial thickness of the lens 10 is d1. A sensor for reading the signal of a formed image is provided on the image side of the lens 20, and is hermetically enclosed by a cover glass 30 so that its light receiving surface may not be directly exposed to moisture, and a space between the light receiving surface and the cover glass is filled with nitrogen gas. Both surfaces of the lens 20 are convex to an object side paraxially, and the lens 20 presents such special shape that the aspherical surface displacing direction is reverse to the paraxial radius of curvature of the aspherical surface, and it is easily realized by using plastic material.

Takayuki Iizuka

JP25734499A

August 05, 2002

December 11, 1990

Click for automatic bibliography generation  

Asahi Optical Co., Ltd.

G02B13/18; G02B13/24; (IPC1-7): G02B13/18; G02B13/24

JP2289806A
JP296107A
JP6177819A
JP2250014A
JP62153811A
JP1209413A
JP478814A
JP411209A
JP4168408A
JP2124509A
JP1158409A
JP1245211A

Tamio Nishiwaki

Previous Patent: LIFE EVALUATION METHOD OF ARTICLE BEING SUBJECTED TO HEAT CYCLE

Next Patent: SCREEN DEVICE HAVING PNEUMATIC CLASSIFICATION FUNCTION