| 摘要 |
PURPOSE:To increase the detecting range of focus and also to improve the S/N for an optical pickup device by giving the focus control of an asymmetrical method to two luminous fluxes which are divided in directions opposite or orthogonal to each other by a beam splitter or a half mirror. CONSTITUTION:The reflected light of an optical disk 5 produces the Kerr revolution of a deflecting surface and is made incident on a half mirror 3. The half of this incident light is made incident on a half mirror 6 while holding the Kerr revolution. The mirror 6 transmits the half of the incident light with the Kerr revolution held. While the other half of the incident light is divided into three luminous fluxes in direction opposite to each other at 90 deg. to the optical axis centering on the diameter of a beam. Then the transmitted light is made incident on a photodetector 8, and the revolving angle of the deflecting surface is converted into the transmitted light quantity and made incident on a photodetecting element 9 of a main signal. While the reflected beams of both sides are made incident on two-split photodetecting elements 7 and 7' respectively. Then a focus shift signal is obtained from the difference component of one or both of the elements 7 and 7'. While a tracking shift signal is obtained from the difference component between both elements 7 and 7'. |
