Apparatus and method for adjusting output value of optical sensor having light-receiving element that receives regularly-reflected light and diffusely-reflected light

An image forming apparatus comprising:

• a first image forming unit configured to form an image of a first color;
• a second image forming unit configured to form an image of a second color different from the first color;
• a transfer member, wherein the image of the first color and the image of the second color are transferred on the transfer member;
• a transfer unit configured to transfer the images on the transfer member onto a sheet;
• an optical sensor including:
• a substrate having a predetermined surface opposing the transfer member,
• a first light-emitting element provided on the predetermined surface of the substrate, wherein the first light-emitting element emits light to a measurement image on the transfer member,
• a second light-emitting element provided on the predetermined surface of the substrate, wherein the second light-emitting element emits light to the measurement image on the transfer member,
• a light-receiving element provided on the predetermined surface of the substrate, the light-receiving element receiving reflected light from the measurement image, the light-receiving element outputting an output value on the basis of a light receiving result of the light-receiving element,
• a first amplifier circuit configured to amplify the output value from the light-receiving element, and
• a second amplifier circuit configured to amplify the output value amplified by the first amplifier circuit;
• and
• a controller configured to:
• control the first image forming unit to form a first measurement image, control the optical sensor to measure the first measurement image, and control a density of an image to be formed by the first image forming unit on the basis of a first output value corresponding to a measurement result of the first measurement image amplified by the second amplifier circuit,
• control the second image forming unit to form a second measurement image, control the optical sensor to measure the second measurement image, and control a density of an image to be formed by the second image forming unit on the basis of a second output value corresponding to a measurement result of the second measurement image amplified by the second amplifier circuit, and
• control the first image forming unit and the second image forming unit to form a plurality of measurement images, control the optical sensor to measure the plurality of measurement images, and control a color registration on the basis of third output values corresponding to measurement results of the plurality of measurement images amplified by the second amplifier circuit.