JPS57173865A - Picture density controller of electronic copier - Google Patents

Abstract

PURPOSE:To always obtain a copied picture having a stable density, by comparing a difference between concentration of a toner after development, of a picture blank part of a photosensitive body, and reference density after development, of a non-picture part, with the reference density by a comparator, and controlling the quantity of replenishment of a toner by this value. CONSTITUTION:When a copying switch is turned on, density of a blank part of a picture part is held in the first idle cycle. Subsequently, in the copying cycle, a latent image of an original 3 and a latent image of a target 6 are formed in the picture part of a photosensitive body 4 and the non-picture part, respectively, these latent images are developed by a developing device 10, and a toner image becomes a reference image 5. The toner image is transferred on a form in the transfer process, and as for the reference image, its density is detected by a density detector 14. This density signal is converted to voltage by a quantity of light quantity-voltage transducer 18, the density is measured by a density measuring circuit 19, and is outputted to a comparator 20 together with the density of the blank part measured previously. The comparator 20 compares a difference between these values with the reference density, a toner replenishing motor 21 is stopped or started in accordance with the detected value is higher or lower than the reference value, thus a toner replenishing roll 10a is controlled.