Title:
LENS
Document Type and Number:
Japanese Patent JP3720187
Kind Code:
B2
Abstract:
PROBLEM TO BE SOLVED: To provide a lens reduced in the number of constitutional lenses and cost and capable of obtaining high reading capacity, a sufficiently large viewing angle, image formation magnification, and brightness.
SOLUTION: A 1st group optical system G1 having positive refractive power, a 2nd group optical system G2 having negative refractive power, a diaphragm 5, a 3rd group optical system G3 having positive refractive power, and a 4th group optical system G4 having negative refractive power are successively arranged from the object side to the image face side. The 1st group optical system G1 is constituted of a positive meniscus lens L1 turning its convex face to the object side, the 2nd group optical system G2 is constituted of a lens L2 forming concave faces on both the sides, the 3rd group optical system G3 is constituted of a lens L3 having convex faces on both the sides and forming an aspherical surface on the image side face, and the 4th group optical system G4 is constituted of a negative meniscus lens L4 turning its convex face to the image side. When the radius of curvature of the object side face 1 of the lens L1 is R1 and the focal distance of the whole lens system is f, a condition of 0.40<R1/f<0.60 is satisfied.
Inventors:
Kazuyasu Ohashi
Application Number:
JP5573498A
Publication Date:
November 24, 2005
Filing Date:
February 23, 1998
Export Citation:
Assignee:
株式会社リコー
International Classes:
G02B13/18; G02B13/24; (IPC1-7): G02B13/24; G02B13/18
Domestic Patent References:
| JP9101452A | ||||
| JP243512A | ||||
| JP1183614A | ||||
| JP3172812A | ||||
| JP6308384A | ||||
| JP11190820A | ||||
| JP10227972A | ||||
| JP1123959A |
Attorney, Agent or Firm:
Shuji Sanada
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