JPS6427030A - Optical recording and reproducing device - Google Patents

Abstract

PURPOSE:To prevent a focus dislocation generated in an optical system, by executing test recording to a test track by varying a focal position synchronously with a rotation, and detecting and correcting a focal position where the amplitude of a reproducing signal becomes maximum. CONSTITUTION:A test track is provided on the recording area of the inner peripheral part of a recording medium. Subsequently, by a sweeping data generating circuit 25, a sweeping signal S11 which is varied successively in accordance with a sector address S10 is generated, and the same signal of short wavelength is recorded to the test track, in a different focus control position at every sector, through a D/A converting circuit DAC 21. A sum signal S3 which has reproduced said signal in a regular focus control position becomes a signal whose amplitude is different at every sector, therefore, it is applied to a detecting circuit 27 and brought to an envelope detection, and a sector whose amplitude is maximum is detected through a detecting circuit 26. Subsequently, it is corrected to a focus control position at the time when the sector whose amplitude is maximum has been recorded, through the circuit 25. When the correction is ended, a light spot is moved to a data recording area and reproduction is executed. In such a way, the focus dislocation is decreased.