Title:
ZOOM LENS
Document Type and Number:
Japanese Patent JPH01302312
Kind Code:
A
Abstract:
PURPOSE:To obtain a satisfactory optical performance and to prevent the occurrence of harmful light such as ghost or flare by providing five lens groups satisfying specific conditions. CONSTITUTION:Conditions of inequalities I-IV are satisfied where L, fi, N5.i, R5.i, fw are the distance between the convergence point of the luminous flux on the axis which passes first to third groups and the front principle point of the fourth group, the focal length of the i-th group, the refractive index of the medium of the i-th lens in the fifth group, the radius of curvature of the i-th lens face of the fifth group, and the focal length at the wide angle end of the whole of this lens system respectively. Thus, a high aperture ratio and a high variable power ratio are obtained, and harmful light like ghost or flare based on the reflected light from surfaces of a cover glass or an image pickup element is effectively eliminated.
Inventors:
HORIUCHI AKINAGA
HAMANO HIROYUKI
HAMANO HIROYUKI
Application Number:
JP13412988A
Publication Date:
December 06, 1989
Filing Date:
May 31, 1988
Export Citation:
Assignee:
CANON KK
International Classes:
G02B15/17; G02B15/167; G02B15/20; G02B27/00; (IPC1-7): G02B15/17
Attorney, Agent or Firm:
Takanashi Yukio