QUANTITY-OF-LIGHT CONTROL METHOD FOR PLATE WIDTH MEASURING INSTRUMENT

摘要

PROBLEM TO BE SOLVED: To enable always using of a light source with the minimum necessary quantity of light by performing a quantity-of-light control to keep the exposure time of an image receiver. SOLUTION: A control panel 40 is provided with an exposure control section 42 to determine exposure time of a CCD camera 30 depending on the intensity of a photodetecting signal of the camera 30 and a lower light source drive control section 44 which receives information on actual exposure time from the exposure control section 42 to output a lower light source drive voltage command according to the difference from the target exposure time. This enables keeping of the exposure time almost constant regardless of secular aging of a light source and changes in measuring environment to be allowed to approach the target exposure time thereby achieving application with the minimum necessary quantity of light.