| 摘要 |
PURPOSE:To prevent diffracted light on a going route from being made incident upon a photodetector by forming an aperture restricting means on an optical path formed from a radiating light source to an information carrier. CONSTITUTION:Radiated light 2 from the radiating light source 1 consisting of a semiconductor laser is passed through a hologram element 5 and the aperture restricting means 7 and converted upon the information recording face of the information carrier 4 by an objective lens 3. The reflected light from the carrier 4 is passed through the lens 3 again and made incident upon the element 5. The plus primary diffracted light 8 out of diffracted light diffracted by the element 5 is made incident upon a detector 6. On the other hand, the radiated light is diffracted at the time of passing the element 5 even in the going path from the light source 1 to the carrier 4 and the minus primary diffracted light 9 is generated. The generation of the diffracted light 9 is reduced by using the means 7 and the generated diffracted light 9 is interrupted even in the return route. Consequently, the diffracted light on the going route is prevented from being made incident upon the photodetector. |
