MAGNETIC MEMORY DRIVE AND OPTICAL DEVICE

摘要

In a magnetic memory drive, a diffraction grating (16) receives a beam emitted by a light source (1) to generate three beams of 0th-order and +1st-order light beams, and a condensing system (17) converges the beams on a magnetic recording medium (4). The beams reflected from the medium is received by a photodetector (15) which outputs signals corresponding to quantities of the received beams, and a signal processor (61) processes the signals to output a tracking error. The photodetector comprises a plurality of light-receiving sections. When crosstalk from a light-receiving section for the 0th-order beam to light-receiving sections for the +1st-order beams is epsilon and crosstalk from the light-receiving sections for the +1st-order beam to the light-receiving section for the 0th-order is epsilon ' in the light-receiving sections of the photodetector, quantity of light Q0 of the 0th-order light beam and quantity of light Q+1 of the +1st-order light beams has a relationship represented by equation (1). Thus, the tracking error is reduced.