| 摘要 |
PURPOSE:To record the stable and corrent information at high speed by positioning plural spots on the same information track and changing over the function of at least one spot at the time of back and forth movements of the relative motion. CONSTITUTION:The state of the information track 51c right before the recording is made by the spot 62 is monitored by the spot 64. When any foreign matter or defect 56 exists, this existence is represented as variation of the light quantity attained to a photodetector 69. A signal from the photodetector 69 is transmitted to a control circuit 74 through a preamplifier 72 and a changeover circuit 73. At the time of recording operation on the information track 51c (back movement time), the monitoring on the track is made by the spot 64, meanwhile this part is performed by the spot 63 when the recording is made on the information track 51b (forth movement time). Therefore, the informations from the preamplifiers 71, 72 are selected and changed over by the changeover circuit 73 in accordance with the informations of the back and forth movements from an interface 77 then transmitted to the control circuit 74. |
