Title:
ZOOM LENS
Document Type and Number:
Japanese Patent JPH03212608
Kind Code:
A
Abstract:
PURPOSE:To obtain the zoom lens which is small in size, high in variable power and has good performance by using aspherical faces for at least one faces of the 2nd lens group of negative, positive and negative 3-lens group consisting and specifying the refractive index of the aspherical faces to <=1.7. CONSTITUTION:The negative 1st lens group, the positive 2nd lens group and the negative 3rd lens group are disposed successively from an object side and the focal distance of the adjacent groups are set at different codes and, therefore, a change in the focal distance of the entire system with a change in the inter-group spacing is large and the constitution effective fro obtaining the high variable power zoom lens is adopted. Since the respective inter-group spacings are monotonously decreased at the time of the variable power from a wide angle end to a telephoto end, the disposition of the refracting power before and after a stop is symmetrically approximated in the entire variable power region and the correction of aberrations is facilitated if the stop is disposed in the 2nd lens group. The aspherical faces are used for at least one faces of the 2nd lens group and the refractive index of the aspherical face lenses is specified to <=1.7, by which the spherical aberrations are well corrected and the change in curvature of field by the variable power is decreased.
Inventors:
MORI NOBUYOSHI
Application Number:
JP711290A
Publication Date:
September 18, 1991
Filing Date:
January 18, 1990
Export Citation:
Assignee:
KONISHIROKU PHOTO IND
International Classes:
G02B13/18; G02B15/16; (IPC1-7): G02B13/18; G02B15/16
Attorney, Agent or Firm:
Fumio Sato (2 others)