| 摘要 |
PURPOSE:To correct the light amount with high reliability by comparing the light amount of a reference light source with that of an exposure lamp through one light amount sensor, and controlling the power supply of a power source so that those light amounts become equal to each other. CONSTITUTION:Light from the exposure lamp 4 is converted by the light-amount sensor 7 into an electric signal, which is converted into a digital signal by a part 16 after amplification 15; and it is compared with the previously stored light amount by an arithmetic device 17 and the light amount from the exposure light source 19 is adjusted so that the exposure lamp 4 and reference light source 10 has the same light amount. Consequently, even if the sensor 7 becomes dirty owing to flying toner and dust in a copying machine, the light amount from the exposure lamp 4 and that from the reference lamp 10 are detected by the one dirty sensor 7 nearly at the same time, so the detection conditions of the both are equal, so that the light amount on a photoreceptor 8 is held nearly constant. |
