Optical information-recording/reproducing apparatus with cancellation for offset contained in error signal

An optical information-recording/reproducing apparatus with cancellation for an offset contained in an error signal, said apparatus comprising:

• beam-irradiation means for irradiating a beam to an optical information-recording medium having a pre-format portion containing an address signal and a data portion including an area in which information signals are to be recorded;
• reflected-beam detection means for producing an electric signal corresponding to a reflected beam from the optical-information recording medium irradiated by said beam-irradiation means;
• error-signal detection means for detecting an error signal for tracking control and/or focussing control of the beam, based on the electric signal from said reflected-beam detection means;
• information-signal detection means for detecting the information signal to be recorded in the data part of the optical information-recording medium, based on the electric signal from said reflected-beam detection means;
• pre-format portion detection means for detecting the pre-format portion of the optical information-recording medium, based on the electric signal from said reflected-beam detection means;
• offset-cancellation means for overlapping the error signal from the error-signal detection means and a compensation signal corresponding to the substantial difference of DC offset components between the data portion and the pre-format portion, detected by said pre-format detection means;
• and
• control means for controlling tracking and/or a focussing of the beam, based on a signal which is generated when the DC offset components contained in the error signal are compensated by said offset cancellation means.