| 摘要 |
PURPOSE:To obtain proper images without being affected by the transmissivity of a subject by providing a sensor for size detection and a sensor for density detection with proper spectral sensitivity characteristics according to their uses. CONSTITUTION:When images 6A and 6B are formed on an original in the density order, the size detection sensor 8 senses an edge 6D of the original 6 as the leading edge of a signal in either case because its sensitivity is almost zero in a wavelength area of a pressure plate where the reflective index is high. The length, i.e. size of the original 6 is found from the original detection time ts so far and a scanning speed. A nearly equal output voltage is obtained as the detection output of the density detection sensor 18 regardless of whether the original is thick or thin because the spectral sensitivity characteristic of the sensor 18 extends to the peak wavelength of the reflective index of the pressure, and density suitable to a photosensitive body is obtained.
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