| 摘要 |
PURPOSE:To make the detection of the density of image rays possible without giving any influence to the image rays at all by subjecting the light source side of a slit plate to a specular treatment, conducting the rays from a light source irradiated by the specular surface to a quantity of light detecting means and detecting the quantity of light. CONSTITUTION:A slit 9 for forming overlay images sharply on a photosensitive drum 1 is subjected to a mirror treatment on part or the entire surface of its light source side, so that part of images are reflected. Part of image rays reflected by the slit 9 pass through a detecting lens 7 and are detected with a detector 8. The output of the detector 8 is beforehand calibrated of the output for a transparent overlay film, and when a film 5 makes one turn, the average density of the entire part of the film is detected easily by integrating the output of the detector 8. |
