Title:
WIDE-ANGLE LENS SYSTEM
Document Type and Number:
Japanese Patent JP3579627
Kind Code:
B2
Abstract:
PROBLEM TO BE SOLVED: To provide a retrofocus and inner focus type wide-angle lens system consisting of three groups and having a half viewing angle being abut 44° and having an f-number being about 3.5.
SOLUTION: This wide-angle lens system is constituted of a 1st negative lens group 10, a 2nd positive lens group 20 and a 3rd positive lens group 30 having a diaphragm in order from an object side, and the 2nd lens group 20 moves in an optical axis direction in the case of focusing. Then, it satisfies following conditional expressions (1) and (2). (1) 0.5<&verbar f1/f&verbar <1.2 and (2) 0.7<f2/f<1.8. Provided that (f) means the focal distance of an entire system at the time of infinity photographing, f1 means the focal distance of the 1st lens group and f2 means the focal distance of the 2nd lens group.
Inventors:
Takayuki Izumi
Application Number:
JP2000037785A
Publication Date:
October 20, 2004
Filing Date:
February 16, 2000
Export Citation:
Assignee:
Pentax Co., Ltd.
International Classes:
G02B13/04; G02B13/06; G02B13/18; (IPC1-7): G02B13/04; G02B13/18
Domestic Patent References:
| JP8248312A | ||||
| JP10260346A | ||||
| JP4719390B1 | ||||
| JP5126535A | ||||
| JP200098222A | ||||
| JP2000131606A |
Attorney, Agent or Firm:
Kunio Miura