Telecentric zoom lens system

Details Telecentric zoom lens system Telecentric zoom lens system

1982-04-05

1987-01-20

Corbin, John K.

350415, 350450, G02B 1516

Patent

active

046376909

ABSTRACT:
As a projection optical system for a measuring projector, a telecentric optical system is required, and, moreover, it is advantageous when a zoom lens system is utilized. The present invention provides a telecentric zoom lens system to be used with a measuring projector wherein an iris is arranged between the lens groups to be moved for variation of magnification and wherein the iris is also moved at the time of zooming in order to prevent increase in the diameter of the front lens and increase in distortion which are caused when the telecentric character is given to a known zoom lens system.
To arrange the iris between a second and third lens groups in a zoom lens system comprising four lens groups respectively having positive, negative, positive and positive powers and to enable to move the iris integrally with the third positive lens group, it is preferable to add a negative lens group between the two positive lens groups, i.e., the third and fourth lens groups, so that the zoom lens system comprises five lens groups respectively having positive, negative, positive, negative and positive powers, and to move the added fourth lens group so that it becomes telecentric in respect to the iris, which is fixed to and at the front of the third lens group.

REFERENCES:
patent: 3316051 (1967-04-01), Baluteau
patent: 3549230 (1970-12-01), Kato et al.
patent: 3918798 (1975-11-01), Takano
patent: 4249805 (1981-02-01), Hilbert et al.

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