Patent ID: 7058294
Filing Date: 2006-06-06
Classification: G02B,H04N

Abstract:
1. An autofocus system for a camera, comprising: a contrast focus detector which detects a position of a focusing lens group, at which a contrast of an object image which passes through a photographing optical system reaches a maximum while moving said focusing lens group via a lens driver, said contrast focus detector defining said position of said focusing lens group at which said contrast of said object image reaches a maximum as a contrast in-focus position; a phase-difference focus detector which separates a light bundle of said object image into two light bundles so that said two light bundles are formed as two object images on a light-receiving element to detect a phase difference between said two object images formed thereon, said phase-difference focus detector defining a position of said focusing lens group at which an in-focus state is obtained for said object as a phase-difference in-focus position; and a controller for moving said focusing lens group via said lens driver to one of said phase-difference in-focus position and said contrast in-focus position, wherein said controller adjusts a moving range of said focusing lens group for detecting said contrast by said contrast focus detector in accordance with a degree of reliability of said phase-difference in-focus position, wherein said reliability corresponds to a minimum value of a correlation function of said two objects images, wherein said controller moves said focusing lens group to a start position spaced from said phase-difference in-focus position by a first moving amount when said minimum value is smaller than a predetermined value, and by a second moving amount when said minimum value is one of equal to and greater than said predetermined value, so as to detect said contrast while moving said focusing lens group from said start position in a direction toward said phase-difference in-focus position, the absolute value of said second moving amount being greater than the absolute value of said first moving amount.