Image forming apparatus

An image forming apparatus to form an image on a sheet, the image forming apparatus comprising:

• an image bearing member;
• an image forming unit configured to form a pattern image on the image bearing member;
• an optical sensor fixed on a fixing member and configured to detect reflected light from the pattern image on the image bearing member;
• and
• a controller configured to receive an output signal output from the optical sensor via a signal line, and to control a density of an image to be formed by the image forming unit based on the output signal,
• wherein the optical sensor includes:
• a substrate,
• a light emitting element mounted on a first surface of the substrate,
• a light receiving element mounted on the first surface of the substrate, and
• a connector mounted on a second surface of the substrate that is opposite to the first surface,
• wherein the substrate has a first positioning hole and a second positioning hole and is fixed to the fixing member by screws inserted through the first positioning hole and the second positioning hole,
• wherein the connector and the signal line are connected,
• wherein a position of the connector on the substrate is offset to a predetermined side from a center between the first positioning hole and the second positioning hole in a longitudinal direction of the substrate,
• wherein the fixing member has a first hole, a second hole, and an interference portion arranged between the first hole and the second hole,
• wherein, in a case where the substrate is fixed to the fixing member by a screw inserted through the first positioning hole of the substrate and the first hole of the fixing member and another screw inserted through the second positioning hole of the substrate and the second hole of the fixing member, the interference portion does not interfere with the connector on the substrate, and
• wherein, in a case where the substrate is fixed to the fixing member by a screw inserted through the first positioning hole of the substrate and the second hole of the fixing member and another screw inserted through the second positioning hole of the substrate and the first hole of the fixing member, the interference portion is contacted by the connector on the substrate.