JPS6450669A - Light quantity monitor device - Google Patents

Abstract

PURPOSE:To monitor deterioration in the light quantity of a lamp at low cost without using a special light quantity sensor by constituting a titled device in such a way that the light quantity of the lamp for original illumination is detected through the use of an image sensor reading the original concerned. CONSTITUTION:The original S illuminated by illumination light beams L2 from original illumination parts 8a and 8b and a reference reflecting plate 4 output reflected light beams 11. The reflected light beams L1 are image-formed on a CCD sensor 38 as a prescribed image by an image-forming lens 36 through a reflecting mirror 34, and they are photoelectrically converted so as to obtain a picture signal. Photoelectric conversion signals from a CCD optical sensor 38 are led into an A/D converter 40 and into one input terminal in a comparator 12, and the light quantity value of a light source 18a is judged to be more than the light quantity value or not. A reference voltage VREF which is obtained by dividing a power voltage V by resisters R1 and R2 is impressed on the other input terminal of the comparator 12, and the reference voltage VREF is selected to the voltage equivalent to a value 90% of reference light quantity, for example.