Patent ID: 7218580

Claim:
A skew detection method of detecting inclination of an optical recording medium including wobble grooves for light spot guide, the skew detection method comprising: separating light beams from a recording/reproduction light source into one main spot and two side spots to irradiate those spots onto a signal recording surface of the optical recording medium to detect, by recording/reproduction light detecting means, reflected light beams respectively corresponding to the main spot and the two side spots which are reflected from the signal recording surface; detecting, when tracking servo is performed along the wobble grooves of the optical recording medium, phase errors between a wobble signal obtained from reflected light beams of the main spot and wobble signals obtained from reflected light beams of the respective side spots; and generating, from a difference in phase error of the received wobble signals, a skew signal including inclination direction and inclination quantity of the optical recording medium.