PURPOSE: To remove distortion of expansion and contraction without generating mechanical distortion, by making a plate-like lens slidable against a case body, the absorbing the distortion generatd by expansion and contraction of the plate - like lens.
CONSTITUTION: A plate-like lens 3 consists of plural lens bodies 4, and these lens bodies 4 are arrayed on one straight line. On a guide base 2 of a case body, guide surfaces 5, 5' are formed, both end faces 6, 6' in the longitudinal direction of the plate-like lens 3 are abutted to the guide surfaces, and both of them are formed in the tapered shape so as to slide by its expansion and contraction. When the plate-like lens 3 expands, the plate-like lens 3 slides in a state that both end faces 6, 6' are always abutted to the guide surfaces 5, 5', therefore, it can be slided without backlash.
SUGASAWA ISAMU
EBARA SHIYOUICHI
ITOU HIDENORI
JIYOUDAI YASUHIRO
