Title:
IMAGE PICKUP LENS HAVING LONG BACK FOCUS
Document Type and Number:
Japanese Patent JP3373031
Kind Code:
B2
Abstract:
PURPOSE: To provide a photographic lens which has an angle of view of about 20°, is as bright as about 2.0 in F-number, has a long back focus and has extremely high optical performance by composing this lens of a first lens group having a negative refracting power as a whole and a second lens group having a positive refracting power as a whole and satisfying specific conditions.
CONSTITUTION: This photographic lens is composed of the first lens group I which is composed, successively from an object side, of a (1-1)th lens of a positive lens, a (1-2)th lens of a negative meniscus lens directing its concave face to an image side and a (1-3)th lens of a biconcave negative lens and has the negative refracting power as a whole and the second lens group II which has the positive refracting power as a whole. The photographic lens described above satisfies the conditions of equation I to equation III. In the equation I to the equation III, (1f) denotes the focal length of the entire system of the lens; f1-2, f1-3 respectively denote the focal lengths of the (1-2)th lens and the (1-3)th lens; fIF denotes the combined focal length of the (1-1)th lens and the (1-2)th lens.
Inventors:
Takada Katsuhiro
Application Number:
JP4116794A
Publication Date:
February 04, 2003
Filing Date:
March 11, 1994
Export Citation:
Assignee:
Olympus Optical Co., Ltd.
International Classes:
G02B13/04; H04N5/225; (IPC1-7): G02B13/04
Domestic Patent References:
| JP2285312A | ||||
| JP5134174A | ||||
| JP727971A | ||||
| JP682689A | ||||
| JP6381310A |
Attorney, Agent or Firm:
Hiroshi Nirazawa (7 outside)