Light spot position detector and optical head

An optical head comprising:

• an objective lens for converging light on an optical recording medium;
• actuating means for actuating said objective lens to provide tracking control and focusing control;
• light receiving means, which is divided into four quadrant light receiving parts by two dividing lines and installed in said optical head, the dividing lines intersecting each other at right angles, for receiving light;
• projecting means for projecting a light spot on said light receiving means, the light spot shifting according to a displacement of the said objective lens driven by said actuating means;
• amplifying means for individually amplifying detection signals from said light receiving parts according to light intensity of the light spot on said light receiving means;
• arithmetic means for calculating a two-dimensional position of the light spot on said light receiving means according to outputs from said amplifying means and for transmitting a first position signal and a second position signal indicating the two-dimensional position;
• and
• gain adjusting means for adjusting gains of said amplifying means and said arithmetic means with respect to the detection signals from said light receiving parts such that an amount of crosstalk between the first position signal and the second position signal is restrained within a given range.

A light spot position detecting method comprising the steps of:

• (a) receiving light by a detector, which is divided into four quadrant light receiving parts by two dividing lines, the dividing lines intersecting each other at right angles;
• (b) individually amplifying detection signals generated by said step (a) according to light intensity of the light spot on the photodetector;
• (c) calculating a two-dimensional position of the light spot on the photodetector and generating a first position signal and a second position signal indicating the two-dimensional position;
• and
• (d) adjusting gains of the amplification of said step (c) and gains realized in said step (c) with respect to the detection signals such that cross talk between the first position signal and the second position signal is controlled.