| 摘要 |
Cam grooves for displacing lenses of an optical system in which lenses or lens groups are displaced in parallel to an optical axis by a lens-operating ring mounted on a support barrel rotatable about the optical axis, but not shifted in parallel to the optical axis. The cam grooves are provided by obtaining the maximum lengths of displacement of vari-focal lenses, among the lengths of displacement of the one or more lenses or one more lens groups, in respective equal-difference minute ranges between respective changed focal lengths, over the entire range of a train of varying focal lengths or photographic distance; and by applying lead angles as slope of cam grooves to the respective maximum lengths of displacement of the lenses.
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