| 摘要 |
PURPOSE:To perform excellent information recording, by detecting the reflected light of laser light during the recording, detecting the state of bit formation from the detected level and controlling a laser light source, and obtaining an adequate laser output. CONSTITUTION:The laser light form the laser light source 6 is focused on a recording medium 1 through a polarization beam splitter 5, quarter-wavelength plate 4, etc., and the reflected light from the recording medium 1 is reflected by the polarization beam splitter 5 to enter a photodetector 8, where it is converted into an electric signal. A switch 9 is closed when bits are generated and opened when not, and the output of the photodetector 8 at the former time and the output of an amplifier 11 when bits sampled by a sampling circuit 10 are not generated are compared with each other by a comparator 12; if the output at the former time is lower, a control part 14 is driven to vary the bias level of the laser light source 14, increasing the laser light output. |
