Patent ID: 6937547
Filing Date: 2005-08-30
Classification: G11B

Abstract:
1. A system for detecting a tracking error, which is to be applied to a tracking servo for causing a light beam to follow a track of an optical disc, said system comprising: a light detecting device for detecting light reflected from said optical disc, said light detecting device comprising two photo detecting elements, which are disposed separately from each other in a direction corresponding to a radius direction of the optical disc; two oscillating devices for generating sine waves, said sine waves having amplitudes based on output levels of said two photo detecting elements, respectively, said sine waves having an identical frequency to each other and being synchronized with each other; a first delay device for adding a predetermined amount of delay to the sine wave, which is generated by one of said two oscillating devices, to delay said sine wave; a second delay device for adding a same amount of delay as said predetermined amount of delay to the sine wave, which is generated by another of said two oscillating devices, to delay said sine wave; a first adding device for adding a signal of the sine wave generated by said one of said two oscillating devices to a signal of the sine wave as delayed by said first delay device, to output a first added signal; a second adding device for adding the signal of the sine wave generated by said one of said two oscillating devices to a signal of the sine wave as delayed by said second delay device, to output a second added signal; and a phase comparison device for comparing said first added signal with said second added signal to make a comparison in phase between sine waves based on said first and second added signals, so as to provide a comparison result, and generating and outputting a tracking error signal based on said comparison result.