Patent ID: 8457509

Claim:
An image forming apparatus that forms an image on an image carrier and transfers the image thus formed on paper to be fixed, the image forming apparatus comprising: an obtaining unit that radiates light from a light-emitting unit onto the image carrier and that obtains an output value of a light-receiving unit having received the light reflected from the image carrier; a light amount setting unit that calculates a required light amount value indicating a light amount required for the light-emitting unit based on the output value and that sets a light amount adjusting value indicating a light amount of the light-emitting unit using a limiting value preset as an upper limit based on the required light amount value thus calculated; a detecting unit that detects a pattern image by forming the pattern image to perform image quality adjustment on the image carrier and by judging whether an output value obtained by radiating light of the light amount adjusting value from the light-emitting unit exceeds a predetermined threshold for performing the image quality adjustment; and a controller that controls image formation on the image carrier based on a detected result by the detecting unit, wherein the detecting unit maintains the threshold at a constant value when the required light amount value does not exceed the limiting value, and reduces the threshold when the required light amount value exceeds the limiting value depending on a degree of the excess, the limiting value being an upper limit of a driving voltage of the light-emitting unit, the pattern image includes a plurality of images, having predetermined widths, varying in a plurality of colors, and which are formed at a predetermined pitch with non-color area between the plurality of images in a sub-scanning direction of the image carrier, and the obtaining unit obtains respective output values corresponding to each of the plurality of colors from each of a plurality of sensors, each sensor including one of the light-emitting unit and one of the light-receiving unit.