PURPOSE: To correct focus movement due to the variation in refractive index and shape alteration with temperature, by mounting an inner lens frame which holds a plastic lens in a lens frame rotatably, and moving the inner lens frame in an optical-axis direction through a rotating mechanism for temperature compensation equipped with bimetals.
CONSTITUTION: A temperature compensating circuit ring 34 is inserted between the outer circumference of the inner lens frame 32 and the inner circumference of the lens frame 30 so that their recessed and projected grooves 33 and 36a, and 35 and 37a engage with each other. When temperature varies in said state, each bimetal varies in curvature to rotate the inner lens frame 32 through screw parts 31 and 39 relatively to the lens frame 30, moving it in the optical axis direction of the lens 40. Therefore, the air gap of the lens system is varied as mentioned above according to the temperature to compensate the focus movement of the lens system due to the temperature variation.
MINEGISHI HITOSHI
YAMADA NOBORU
