| 摘要 |
PURPOSE:To obtain invariably proper exposure by increasing the quantity of light of a light source automatically according to the degree of contamination of a mirror. CONSTITUTION:An extremely small mirror 21 is fixed to the top surface of the end part of the light source and a photodetecting element 22 is provided opposite the small mirror 21 and below the 1st mirror unit 7. The position relation among the light source 5, small mirror 21, and photodetecting element 22 is so adjusted that the rays of light emitted by the light source 5 are reflected by the small mirror 21 and then by the 2nd mirror 11 and the 3rd mirror 12 to enter the photodetecting element 22. A voltage or current generated according to the quantity of the light incident on the photodetecting element 22 is amplified by an input amplifier 23 and inputted to a control part 24. The control part 24 controls the voltage or current of the light source 5 according to variation in the voltage or current corresponding to the quantity of the light incident on the photodetecting element 22 from a voltage or current when the quantity of light is initially set properly, thereby controlling the quantity of light emission of the light source 5. |
