Optical information recording and reproducing apparatus

Claim 1

An optical information recording and reproducing apparatus, comprising: an optical system for condensing lights generated in a light source and projecting said lights onto an optical recording medium, a focus actuator means having a focusing coil and impressing a driving signal on said coil to vary the distance of said optical system from said recording medium to adjust the focus of said optical system, a focus error detecting means for receiving reflected lights or passing lights in said recording medium to output a focus error signal corresponding to an offset amount from the focus state of said optical system, a gain controlling means interposed between said focus error detecting means and a driving circuit for receiving a plurality of controlling input signals for variably setting gains and for outputting a driving signal to said focusing coil, and an offset fluctuation controlling means for controlling a level shift of said driving signal produced on the basis of said focus error signal, whereby the light emitting output of said light source is varied in response to data to be recorded, the data is written into said recording medium and, at the time of a writing mode, said offset fluctuation controlling means is controlled to hold the offset amount of said driving signal to be fixed.