| 摘要 |
PURPOSE:To miniaturize a hard part on a tip of an endoscope and to easily apply the titled optical system for medical purposes by arranging an optical path converting prism and correcting prism in an optical path from the incident face of an objective lens up to a light receiving face of a fixed image pickup element. CONSTITUTION:The optical axis of the objective lens O in the endoscope optical system is made parallel with the center axis of the endoscope. The lens O is constituted as a retro-focus type consisting of a front group F having negative refractive force and a rear group R having positive refractive force and a filter FL, an optical path converting prism P1 and a correcting prism P2 are successively arranged on the projection side of the lens O. The angles of two reflections on the prism P1 can be optionally changed by the combination of these prisms P1, P2 and the projection point of the prism P2 is arranged on a position near the extension line of the optical axis of the lens O. Said correction makes it possible to prevent one end of the element S from being projected from the outside system of the lens system and the whole optical system can be miniaturized.
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