IMAGE FORMING APPARATUS AND METHOD FOR DETECTING PATTERN IMAGE FOR IMAGE QUALITY ADJUSTMENT

PROBLEM TO BE SOLVED: To perform pattern detection following change over time such as soiling of a sensor, in image quality adjustment. SOLUTION: A color image forming apparatus 1 includes the optical sensor 22 that emits light to an intermediate transfer belt 5L and obtains an output value output when light reflected from the intermediate transfer belt 5L is received. On the basis of the output value of the quantity of light, the color image forming apparatus calculates the required value of the quantity of light to be emitted. On the basis of the required value of the quantity of light, the color image forming apparatus sets the adjusted value of the quantity of light having a preset limit value as the upper limit. The color image forming apparatus 1 forms a pattern image for image quality adjustment on the intermediate transfer belt 5L, and detects the pattern image according to whether an output value obtained by emitting light with the adjusted value of the quantity of light from the optical sensor 22 exceeds a predetermined threshold value. If the required value of the quantity of light exceeds the limit value when this pattern image is detected, a threshold is decreased according to the degree of excess. COPYRIGHT: (C)2011,JPO&INPIT