| 摘要 |
PURPOSE:To make an optical system compact by making its shape almost cylindrical, by irradiating again the reflected light on a recording carrier by means of a slightly inclined mirror, and detecting the again reflected light by a radiation detector. CONSTITUTION:The radiation beam generated from a radiation light source 12 is reflected by a recording part 18, transmitted through a objective lens 16 and lambda/4 wavelength board 15, reflected on a polarization beam splitter 14 and made to be incident to a mirror 19. The mirror 19 is inclined in a slight angle, and the light reflected on the mirror 19 reversely follows the incident path and is again radiated to the recording part 18. The again reflected light is slightly diverted and made incidence to a radiation detector 20, and a position error detection signal is obtained by the detector 20. By making an optical system as mentioned above, the optical system can be made almost cylindrical because the mirror 19 can be set near to the polarization beam splitter 14 so that the system can be made compact. |
