Title:
ZOOM LENS
Document Type and Number:
Japanese Patent JPH03155516
Kind Code:
A
Abstract:
PURPOSE:To obtain an inexpensive, compact, and bright zoom lens with zoom ratio of around six times by comprising zoom lenses of four groups, especially, the fourth lens out of them of a comparatively few number of lenses, and also, attaching a high positive power. CONSTITUTION:The zoom lens is comprised of a first lens group with a positive refracting power moving on an optical axis for focusing, a second lens group with a negative refracting power moving on the optical axis for variable power, a third lens group with the negative refracting power moving on the optical axis for the correction of an image surface fluctuating based on the variable power, and the fourth lens group with the positive refracting power fixed for image-forming. At such a case, the fourth lens group is provided with a diaphragm, and also, it is comprised of a 4a-th lens group with the positive refracting power and a 4b-th lens group with the positive refracting power, which satisfies the condition of equation I. Where, it is assumed; fw:focal distance of entire system at short focal distance side, fIV:focal distance of fourth lens group, and fIVA:focal distance of 4a-th lens group in equation I. Thereby, it is possible to obtain the inexpensive, compact, and bright zoom lens with zoom ratio of around six times.
Inventors:
YONEYAMA SHUJI
Application Number:
JP18584190A
Publication Date:
July 03, 1991
Filing Date:
July 13, 1990
Export Citation:
Assignee:
ASAHI OPTICAL CO LTD
International Classes:
G02B15/20; (IPC1-7): G02B15/20
Attorney, Agent or Firm:
Kanai Hideyuki