Patent ID: 6754146
Filing Date: 2004-06-22
Classification: G11B

Abstract:
An error signal detection apparatus for an optical recording/reproducing system comprising a light source emitting a light beam and an objective lens focusing the light beam to form a light spot on a recording medium, the apparatus comprising:a photodetecting unit dividing at least a part of the light beam passed through the objective lens after being reflected/diffracted from an information stream of the recording medium into light beam portions, and detecting the light beam portions; and a signal processor detecting phase differences between detection signals from the light beam portions to detect a tangential tilt error signal, wherein the photodetecting unit divides the light beam into first, second, third, and fourth light beam portions in a direction corresponding to a radial direction of the recording medium, and detects and outputs first, second, fourth, and third detection signals from the first, second, third, and fourth light beam portions, and the signal processor detects and outputs the tangential tilt error signal as a sum of a phase difference between the first and second detection signals and a phase difference between the third and fourth detection signals, detects a phase difference between a fifth detection signal which is a sum of the first and third detection signals, and a sixth detection signal which is a sum of the second and fourth detection signals, compares a phase of the fifth detection signal with a phase of the sixth detection signal, and outputs a fifth phase comparison signal when the phase of the fifth detection signal leads the phase of the sixth detection signal, and a sixth phase comparison signal when the phase of the sixth detection signal leads the phase of the fifth detection signal.