| 摘要 |
PURPOSE:To detect a shading state with a simple struction by arranging a shading member on optical paths to be used in common at the time of reading and printing and making a part of the shading member light-transmissible. CONSTITUTION:Areas A1, A2 are common optical paths to be used at the time of reading and printing and the shading device 25 through a part of which light can be transmitted is arranged on either one optical path. Small windows 60 for transmitting light are formed on respective part corresponding to shading areas 30C, 30D positioned between apertures 30A, 30B in the advancing direction of the belt 30. When the shading areas 30C, 30D are set up on the positions shading the whole optical paths, only light beams passed through the windows 60 of both the areas 30C, 30D are directed to the screen and only the areas of the screen corresponding to the windows 60 are brightened. Thus, the shading of the whole optical paths can be detected by checking the existence of the bright part.
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