US PATENT SUBCLASS 359 / 689
.~.~.~ Three groups

Current as of: June, 1999
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359 /   HD   OPTICS: SYSTEMS (INCLUDING COMMUNICATION) AND ELEMENTS

642  DF  LENS {32}
676  DF  .~ With variable magnification (e.g., zoom type ) {6}
683  DF  .~.~ With mechanical compensation {6}
689.~.~.~ Three groups {1}
690  DF  .~.~.~.~> + - + Arrangement

DEFINITION

Classification: 359/689

Three groups:

(under subclass 683) Subject matter wherein three groups move independently of each other and at least two of the groups function respectively as (1) a variator movable of varying the focal length and (2) a compensator which moves independently of the first group for compensating for image plane deviation focal length variation.

SEE OR SEARCH THIS CLASS, SUBCLASS:

686+, for mechanical compensation with variable magnification having four groups.

691+, for mechanical compensation with variable magnification having two groups.