Patent ID: 8000213

Claim:
An optical disc recording/reproducing apparatus comprising: an optical pickup which applies a spot of light beam to an optical disc of a land/groove recording system including a first header region that is formed at a position shifted toward one side of a direction perpendicular to a track and a second header region that is formed at a position shifted toward the opposite side from the first header region, and detects reproduced signals from the reflected light beam; a first adder which adds the reproduced signals detection by the optical pickup; a variable amplifier which performs amplitude adjustment for a header region of the added reproduced signal; an offset voltage adjustment circuit which performs adjustment so that the signal in the amplitude-adjusted header region falls within a dynamic range; an A/D converter which converts the output signal from the variable amplifier into a digital signal; peak detection circuits which detect peak values of the reproduced signals in a first section and a second section in the header region, respectively; bottom detection circuits which detect bottom values of the reproduced signals in the first section and the second section in the header region, respectively; a first subtracter which obtains amplitude information in the first section and the second section in the header region, from the peak values and the bottom values which are detected in the first section and the second section by the respective detection circuits; a second subtracter which obtains a difference in amplitude between the first section and the second section in the header region, based on the amplitude information obtained by the first subtracter, and outputs the amplitude difference as an off-track error signal; a detection control timing generation circuit which generates a detection control timing for a detection section that is the first section or the second section in the header region, and replaces the detection control timings of the respective detection circuits at a switching between the land and the groove; and said respective detection circuits holding the detected values obtained by the previous detection operations in sections other than said detection section under the control of the detection control timing generation circuit.