Patent ID: 6263163
Filing Date: 2001-07-17
Classification: G02B

Abstract:
A focal length detector of a camera having a zoom lens, said focal length detector having a code plate and a brush which contacts with said code plate, said code plate and said brush being moved relative to each other according to a variation of the focal length of said zoom lens, said focal length detector having a focal-length detecting circuit;wherein said brush comprises three sliding contacts which are electrically connected to one another;wherein said code plate comprises three code patterns and a ground pattern which are insulated from one another, said three code patterns and said ground pattern being electrically connected to said focal-length detecting circuit,wherein said ground pattern remains in contact with a specific sliding contact of said three sliding contacts regardless of the relative position of said code plate and said brush,wherein said three code patterns come into contact with the remaining two of said three sliding contacts in predetermined combinations when said code plate and said brush are moved relative to each other,wherein two of said three code patterns are formed as two repetitive-pattern detecting terminals for detecting intermediate focal lengths between a wide-angle extremity and a telephoto extremity of said zoom lens, the two repetitive-pattern detecting terminals having code patterns that, in combination with a remaining two of said three sliding contacts, generate non-unique codes for detecting relative focal length movement of said zoom lens, andwherein a remaining one of said three code patterns is formed as a specific-code detecting terminal for detecting specific focal length positions of said zoom lens.