| 摘要 |
PURPOSE:To execute highly precise focusing and tracking without allowing the structure to be complicated without the necessity of using a highly precise feedback system and an object lens by generating the phase conjugate light of monochromatic light with which an optical recording medium is irradiated and detecting the light. CONSTITUTION:Light from the monochromatic light source 1 of a position. A passes through a beam splitter 2 and the object lens 12 forms a spot for information reading on a position B conjugated with the position A on the optical recording medium 5. Only the light made incident on a part 5h whose reflectance is high on the medium 5 among incident light 4 is made incident on a phase conjugate mirror 7 and phase conjugate light 8 from the mirror 7 reversely moves the same path as reflected light 6, passes through the lens 12, is reflected on a beam splitter 2 and reaches a photodetector 9 on a position C conjugated with the positions A and B. The influence of the focus error and tracking error of the medium 5 is not accepted on the detector 9 and the need for a highly precise focusing/tracking feedback system and the object lens is eliminated. |
