| 摘要 |
PURPOSE:To make correspond a beam luminous quantity on a recording medium nearly one to one to an output voltage of a luminous quantity detection circuit by adjusting an output voltage of the light quantity detection circuit so that a measured luminous quantity of a luminous quantity measuring instrument arranged at a prescribed location of a beam path is a prescribed value. CONSTITUTION:The luminous quantity measuring instrument is arranged to a prescribed location of a beam path, e.g., at the scanning start end of a recording medium to measure the accurate beam luminous quantity. Then a beam is inputted to a luminous quantity detection circuit 11 and a variable resistor 19 is adjusted so that an output voltage Vm reaches a prescribed value. Through the adjustment, the beam luminous quantity on the recording medium and the output voltage of the circuti 11 are made coincident nearly one by one independently of the variation of the output current Im of a photodetector 10 and the variation in the coupling efficiency of a collimate lens.
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