| 摘要 |
PURPOSE:To realize the control of the exposure with high accuracy and high stability by means of an inexpensive photodetector available in the market, by using a quantity of light detecting means having the spectral sensitivity that substantially cuts the infrared rays. CONSTITUTION:A filter that cuts the >=700mmu beams down to <=5% for instance is put in front of a photodetector PD as a light receiver 4 in an exposure controller 5 of a copying machine. As a result, the stable quantity of light can be obtained to a photoreceptor and under any environment. Accordingly it is unnecessary to set the photoreceptor at the same spectral sensitivity as the photoreceptor. Then the quantity of light can be simply controlled by cutting the long wavelength light having no sensitivity to the photoreceptor by a filter. In such way, the exposure can be controlled with high accuracy and high stability by means of an inexpensive photodetector available in the market. |
