STEP-VARYING-LENGTH OBJECTIVE LENS Russian patent published in 1998 - IPC

FIELD: optical instrumentation engineering; TV systems. SUBSTANCE: objective lens has fixed first and second components and moving third and fourth components of different design for different focal lengths of objective lens made for entrance in and exit from optical circuit. First focal length of 500.5 mm is provided by first and second fixed components 1 through 8. Second focal length of 200.1 mm is formed by first and second components 1 through 8 and by moving third and third components 9 through 13. Third focal length of 70.1 mm is produced by fixed first and second components 1 through 8 and third And fourth components 14 through 21 mounted for their entrance in and exit from optical circuit. EFFECT: provision for stepped variation of focal length and obtaining of its three values. 7 dwg , 6 tbl