| 摘要 |
PROBLEM TO BE SOLVED: To optimize the quantity of laser beams for the recording/reproducing operation by accurately measuring the surface temperature of a rotary disk without contact and also predicting the temperature rise of the disk from the ambient temperature. SOLUTION: The surface temperature of the rotating disk is measured by an infrared detector 5 in the manner of simultaneously measuring the same places of the disk by different wave-lengthsλ1,λ2, and by means of obtaining a ratio of radiation energy Wλ1 and Wλ2, the true temperature is measured without being affected by radiation rate of the disk. A thermistor 6 is arranged around the disk to measure the ambient temperature, and the detected signal is inputted to a microcomputer 9 as the temperature information through a thermistor amplifier 8. Since the surface temperature of the disk 1 is largely varied when the temperature difference with the ambient temperature To is large, the temperature Ta detected by the infrared detector 5 and the temperature Tb detected by the thermistor 6 are monitored for keeping the surface temperature constant after a lapse of specified time except the transient period, and when the difference of these temperatures becomes the prescribed temperature or higher, the adjustment of the quantity of laser beams for recording is carried out.
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