Title:
GAUSS TYPE LENS
Document Type and Number:
Japanese Patent JP3254165
Kind Code:
B2
Abstract:
PROBLEM TO BE SOLVED: To obtain high reading density in the vicinity of image formation magnification 0.16535, to reduce cost and to obtain the sufficient angle of view and sufficient brightness by arranging 1st group to 4th group which are positive, negative, negative and positive from an object side and making them satisfy specified conditions.
SOLUTION: The 1st and the 2nd groups, a diaphragm, and the 3rd and the 4th groups are arranged from the object side. The 1st group is a 1st lens being a positive meniscus and the 2nd group is constituted by bonding 2nd and 3rd lenses being a positive meniscus and a negative meniscus. The 3rd group is constituted by bonding 4th and 5th lenses being a negative meniscus and a positive meniscus and the 4th group is a 6th lens being a positive meniscus. Assuming that n2, n3, ν2, and ν3 are the refractive indexes and the Abbe numbers of the 2nd and 3rd lenses, R3 to R5 are the radii of curvature of the object side surface and the image side surface of the 2nd lens, and the image side surface of the 3rd lens, D5 and D6 are distances between the image side surface of the 3rd lens and the diaphragm, and the diaphragm and the object side surface of the 4th lens, and (f), f1 and f4 are the focal distances of an entire system, the 1st group and the 4th group, respectively, the conditions expressed by expressions are satisfied.
Inventors:
Kazuyasu Ohashi
Application Number:
JP11717097A
Publication Date:
February 04, 2002
Filing Date:
May 07, 1997
Export Citation:
Assignee:
株式会社リコー
International Classes:
G02B13/24; G02B9/08; (IPC1-7): G02B13/24
Domestic Patent References:
| JP8146292A | ||||
| JP8286107A | ||||
| JP9113802A | ||||
| JP5113535A | ||||
| JP4311912A | ||||
| JP4125516A | ||||
| JP6342120A | ||||
| JP56107208A |
Attorney, Agent or Firm:
Yoshiyuki Ishibashi