JPS6413236A - Optical pickup - Google Patents

Abstract

PURPOSE:To reduce the number of components and to miniaturize a pickup by constituting the titled device so that a photosensor is arranged at a position where a laser beam is not directly projected but made incident thereon through an opening, and a birefringent plate is arranged between a recording medium and a laser. CONSTITUTION:The birefringent plate 22 having different refraction factors according to the forwarding direction of an incident light is arranged between the semiconductor laser 21 and a lens 11 and the photosensor 16 where the laser beam 6 is not directly projected but only the incident light through the opening 9 is projected, is arranged on a protruding part 4b. The laser beam 6 from a laser chip 5 is projected to a disk through the birefringent plate 22, the lenses 11, 14 and a quarter wave-length plate 13, and when the reflected light 6 is made incident on the birefringent plate 22, since the focus by the lens 11 is shifted out of the position of the laser chip 5 by the change of the refraction factor, the reflected light is detected by the sensor 16. Accordingly, the number of components is reduced, and the pickup can be miniaturized.