Density detecting device used for image forming apparatus

Abstract

A device and method for detecting a toner image density accurately while using a characteristic curve found at the time of initialization. In the initialization, light of a first amount for low density is irradiated onto a photoreceptor from a density sensor, to acquire a first low-density light amount characteristic curve. In the characteristic curve, a toner image density corresponding to first density data is taken as a first reference density. A first amount of light for high density is then set to acquire a high-density light amount characteristic curve. In the characteristic curve, density data corresponding to the first reference density is taken as first correcting reference data. In density detection, a second amount of light for low density and a second amount of light for high density are found. A second low-density light amount characteristic curve corresponding to the second amount for low density is acquired. The density of a toner image having the second reference density approximately equal to the first reference density is detected by the density sensor irradiating light of the second amount for high density. The density data outputted by the density sensor is taken as second correcting reference data. If the second amount for high density is set, the density data outputted by the density sensor is corrected on the basis of the first and second correcting reference density data.