JPS5525853A - Tracking device for optical information track - Google Patents

Abstract

PURPOSE:To avoid the position shift of the optical system and the reduction of the light and thus to realize an automatic tracking of the track in a high accuracy by using the array of the semiconductor light source and also utilizing the optical self- coupling effect for the detection. CONSTITUTION:The beams sent from array 1 of seviconductor light sources 1a-1c are shifted in the direction crossing information track 8 on recording carrier 7 and then condensed in the form of three beam spots 6a-6c via light deflector 4 and condenser lens 5. Spots 6a-6c reflected from carrier 7 are put into sources 1a-1c again through deflector 4 and lens 5. Optical detectors 10a-10c detect the variation of the light intensity via the self-coupling effect. In this case, the mean value of the light intensity between sources 1a and 1b varies by the shift to the center of information track 8 of spot 6b. Differential amplifier 12 gives the differential amplification to the differntial output of detectors 10a and 10c and aoplies defferntial output 13 so as to give the negative feedback to the output to deflector 4. Thus the position of spot 6b is put at the center of track 8 automatically.