| 摘要 |
PURPOSE:To exceedingly improve detection sensitivity and to miniaturize an optical pickup part by causing the interference of luminous fluxes varying in displacement of angles by defocusing within the section of thee light emitted from an interference fringe generating means. CONSTITUTION:The light emitted from a semiconductor laser 9 throughcollimating lens 10 and a beam splitter 11, is changed in optical path by a rising mirror 16 and is condensed by an objective lens 12. The surface of an optical disk 17 is irradiated with the condensed light. The reflected light from the optical disk 17 traces the reverse route and is reflected by the beam splitter 11 so as to be made incident on double diffraction gratings 14. The adjustment in such a case is executed more roughly than heretofore simply by bringing photodetectors 18, 19 near to the double diffraction gratings 14 and fixing the photodetectors with accuracy of several ten microns while observing the outputs of the photodetectors. The extremely small optical pickup is constituted by using the double diffraction gratings 14. |
