The present invention relates to a original illuminating device of a copying machine, more particularly, to original illuminating device that illuminates the original by effectively leading light from a bar-shaped illuminant.
Typically, as shown in FIG. 4, any conventional electrophotographic copying machine is provided with an illuminant 72 comprised of a halogen lamp for example at a specific position of condenser mirror 71 and also with a plane reflection mirror 73 which faces the condenser mirror 71 and the relative positions of the installed condenser mirror 71 and the plane reflection mirror 73 are correctly set to allow light to radiate the original surface 75 placed on the contact glass 74 by the predetermined incident angles being opposite from each other. Light reflected from the original 75 is then vertically led downward to allow slit 76 to cut unnecessary portions before eventually being led to the image processing unit which is not shown in FIG. 4.
When using such a original illuminating device having the constitution mentioned above, since the original 75 can be illuminated also by plane reflection mirror 73 in addition to the illumination of the original 75 by the condenser mirror 71, light emitted from the illuminant 72 can effectively be used for illuminating the original 75.
On the other hand, such a conventional copying machine usually improves performances for detaching the copied paper from both the photoreceptor drum and fixing roller by providing blank portion having a specific width at the tip end of the copied paper. Normally, white reflection part 77 is provided on the bottom surface of the contact glass 74 for generating the blank portion. As a result, when intensity of light from the plane reflection mirror 73 is strong, there is a significant difference in the amount of light radiated onto the original 75 between those conditions in which light is shut off by the reflection part 77 and light freely radiates onto the original 75, thus causing tip-shadow to be generated in the tip portion of the copied paper. Conversely, when intensity of light from the plane reflection mirror 75 is weak, in order to radiate the predetermined intensity of light onto the original 75, light volume should be increased by strengthening the magnitude of watt of the illuminant 72 itself.