| 摘要 |
PURPOSE:To accelerate response to the switching of a printing density and to obtain excellent printing quality by changing the reference value of an optical density detecting means and the light emitting time of a light emitting means which irradiates a photosensitive body in response to this change. CONSTITUTION:When the reference value of the optical density detecting means 5 is changed by a printing density designating means 8, the light emitting time of the light emitting means 2 is changed in response to a change in the reference value, and accordingly the width and intensity of a bright part potential of an electrostatic latent image formed on the surface of the photosensitive body 1 vary, so that a printing density varies. An optical density on the photosensitive body 1 detected by the optical density detecting means 5 is compared with the reference value, and when the detected density is lower than the reference value, toner is replenished to a developing unit 3. Thus, a toner concentration in a developer inside the developing device 3 is kept constant, the response to the switching of the printing density is accelerated to change the printing density. Moreover, excellent printing quality is obtained. |
