OPTICAL HEAD

摘要

PROBLEM TO BE SOLVED: To simplify an information signal reproducing system and a servo signal detecting system by integration and to detect a tracking error signal with good accuracy. SOLUTION: The laser beam separated by a beam splitter 25 is introduced through an optical system consisting of a Wollaston prism 26 and a diffraction grating 27 to photodetector 28. The two luminous fluxes among the three luminous fluxes separated by the Wollaston prism 26 are further separated by the diffraction grating 27. Information signals are reproduced by using the separated zero order diffracted light and ± first order diffracted light. The other one luminous flux is further separated by the diffraction grating and the focus error signal is detected by using the separated zero order diffracted light. The tracking error signal is detected by using the separated ± first order diffracted light. The photodetecting surface of the photodetector 28 is made smaller by setting the angle formed by the gratings of the diffraction grating 27 smaller than 45 deg. from the dividing line.