Photodetecting system for a magneto-optical disk head system

Claim 1

A magneto-optical disk head system, comprising: a laser light source for emitting a laser light; an optical system for focusing said laser light emitted from said laser light source on a magneto-optical disk; means for separating a reflection light of said laser light reflected at said magneto-optical disk to a plurality of polarized lights having orthogonal polarization directions; a photodetector for detecting said plurality of polarized lights, said photodetector comprising: a plurality of photodetecting segments divided into plural groups, wherein each one of said plurality of photodetecting segments has a cathode, wherein the cathodes of photodetector segments within the same group are connected in common, and wherein each said photodetector segment is a photodiode comprised of; an insulating substrate; a cathode semiconductor layer formed on the insulating substrate; and a plurality of anode semiconductor layer regions formed on the cathode semiconductor layer; said cathode semiconductor layer being divided by recesses that extend from the top surface of the cathode semiconductor layer in close proximity to the anode semiconductor layer regions to the insulating substrate; said magneto-optical disk head system further comprising: information signal detecting means for detecting an information signal of said magneto-optical disk by performing a subtraction between a first sum obtained by adding cathode signals of a first group of said photodetecting segments and a second sum obtained by adding cathode signals of a second group of said photodetecting segments; and error signal detecting means for producing focusing and tracking error signals of said magneto-optical disk by adding and subtracting anode signals of said first and second groups of said photodetecting segments.