JPS6472676A - Mechanism for detecting optical system position - Google Patents

Abstract

PURPOSE:To reduce cost and to improve reliability by providing an optical member emitting a part of light beams irradiated by means of an optical system in the shifting direction of the optical system and disposing a light-receiving element beyond the moving range of the optical system. CONSTITUTION:The optical member emitting a part of the light beams irradiated by the optical system in the shifting direction of the optical system is provided in the optical system, and the lightreceiving element receiving the light beams which have been emitted from the optical member is disposed beyond the moving range of the optical system. Namely, the detected light quantity of a photodetector 16 changes in accordance with a solid angle viewed from the light source S' of a light-receiving surface in the photodetector 16 in the emitted light beams of the light source S', and it is proportional to the square of a distance between the light source S' and the photodetector 16. Thus, the distance between an optical pickup 3 and the photodetector 16 can be detected. Namely, the shifting and absolute positions of the optical pickup 3 with respect to a case 1 can be detected. Thus, the optical pickup position detector of low cost, high precision and non-contact can be obtained.