Patent ID: 8249481

Claim:
A developing device comprising: a developing roller that supplies toner to an electrostatic latent image formed on a surface of a photoreceptor to form a toner image; a developing tank that stores a two-component developer containing toner; a toner density detecting section that detects a toner density in the developing tank and outputs a detection result, an output value of the detection result changing in accordance with an input control value; a correcting section that calculates a sensitivity coefficient regarding a sensitivity of the toner density detecting section, which is indicative of a correlation between the control value and the output value, and corrects the control value based on the calculated sensitivity coefficient; and a toner density calculating section that calculates the toner density in the developing tank using the detection result obtained from the toner density detecting section to which the corrected control value is inputted, the correcting section recalculating the sensitivity coefficient for each predetermined time interval or whenever a predetermined condition is satisfied, calculating an actual amount of correction from a product of the recalculated sensitivity coefficient and a correction voltage value that is expected from a reference value of the control value and the toner density, and correcting the control value based on a sum of the calculated actual amount of correction, a voltage value that is determined depending on a temperature detected by a temperature sensor, and a voltage value that is determined depending on a humidity detected by a humidity sensor.