DEVELOPMENT DENSITY DETECTOR

摘要

PURPOSE:To detect development density even during printing operation by forming an electrostatic latent image for density detection except in the image area of a photosensitive body by scanning a laser beam, and comparing its density with a reference density value and judging whether the development density is adequate or not. CONSTITUTION:An optical modulator 15 modulates the laser beam 17 from a laser 16 according to a video signal 13 and a pattern signal 24. An electrostatic image for density detection is formed beside the image area of the photosensitive body 11 and further developed by a developing device 21 to obtain the toner image for density detection. When this toner image 25 for density detection faces a light emission part 31 and a photodetection part 32 according to the rotation of the photosensitive body 11, the light emission part 31 irradiates the toner image 25 and the reflected light is made incident to the photodetection part 32. The density signal 34 outputted by a photodetection quantity converting circuit 33 is supplied to a comparing circuit 35 and compared with the reference density signal 37 from a reference voltage generating circuit 36.