| 摘要 |
PURPOSE:To attain the always excellent recording and complete erasure by adopting the constitution that each light source is driven while the relation between recorded light power and extinction light power is kept constant. CONSTITUTION:Differential amplifiers 19, 20 output the difference between outputs VPW, VPE from a PIN diode and reference voltages VSW, VSE respectively. Both laser drive circuits 21, 22 give a current to each laser so that the outputs of the differential amplifiers 19, 20 are zero, that is, the relation of VPW=VSW and VPE=VSE is always established to apply power control. The characteristic of a converter 24 is constituted to establish the relation of VSE= K.VSW and the converter is turned on with a gate signal at 'L' and turned off at 'H'. An 'L' level of a REC signal is given to a gate at reproduction and an 'H' level is given at recording. Thus, the relation of VSE=0, that is, the extinct light power is zero at the reproduction and the relation of VSE= K.VSW is established at the recording, and the optimum extinct light power is lighted to the recording light power. |
