ERROR SIGNAL DETECTING SYSTEM

摘要

PURPOSE:To simplify a control mechanism of a photodetecting element and to attain the miniaturization of an optical head by dividing a reflected luminous flux into two parts through a prism having different output angles and leading these divided luminous fluxes to the 1st and 2nd 2-split phtodetecting elements which are unified on the same plane. CONSTITUTION:The light 10 delivered from a semiconductor laser 1 and reflected by a disk 8 is reflected again by a polarizing/reflecting surface 5a of a polarized beam splitter 5 and made incident on a prism 31. The lower half of the luminous flux goes straight to be turned to a focused beam 33a and made incident to 2-split areas 34a and 34b of a photodetecting element 34. While the upper half of the luminous flux is polarized into two directions to be converted into focused beams 33b and 33c and made incident on 2-split areas 34d and 34e of the element 34. A focus error signal is obtained from the difference between output signal of areas 34a and 34b. While a tracking error signal is obtained from the difference between output signals of areas 34d and 34e. In such a way, the control mechanism of the element 34 is greatly simplified.