Patent ID: 8040501

Claim:
An image forming apparatus comprising: a carrier; a forming device configured to form a mark on the carrier; a sensor including a light emitting device and a light receiving device, the light emitting device being configured to emit light toward the carrier, and the light receiving device being configured to receive light reflected from at least one of the carrier and the mark and output a light reception signal corresponding to a quantity of the received light; a determiner configured to determine a position of the mark on a basis of the light reception signal; a changer configured to change a sensor sensitivity of the sensor by changing at least one of a quantity of light emitted by the light emitting device and a sensitivity of the light receiving device; an evaluator configured to obtain the light reception signal a plurality of times and configured to evaluate a degree of closeness between an average level of the light reception signal obtained a plurality of times and a target level; and a controller configured to control the changer to change the sensor sensitivity of the sensor according to a result of the evaluation of the evaluator, wherein a first ratio is a ratio of a number to the plurality of times, the number being a number of times where either one of a plurality of conditions is met, the plurality of conditions including a condition where the light reception signal is at the target level, a condition where the light reception signal is equal to or lower than the target level, and a condition where the light reception signal is equal to or higher than the target level, and wherein the evaluator evaluates the degree of closeness on a basis of a judgment whether the first ratio is within a reference range.