| 摘要 |
PURPOSE:To decrease the deterioration in performance due to secular change or the like by providing a photodetector in the transmission direction of a half mirror and a laser diode in the reflecting direction. CONSTITUTION:A laser light is irradiated from a laser diode 1, divided into three beams through a diffraction grating 2, reflected on the half mirror 3 and a light spot is projected on an information track on a disc 7 via a collimator lens 4 and a focusing lens 8. The laser light reflected on the disc face 7 passes through the half mirror 3 and is projected and received by the photodetector 6 through a detector lens 5. The durability of the optical system pickup is improved remarkably without affected by the variation of the assembling accuracy of the bonding face of the half mirror and the tilt of the half mirror reflecting face attended with secular change and also ease of assembling is attained. |
