Optical sensor and image forming apparatus including same

An image forming apparatus, comprising at least:

• an image bearing member configured to bear a toner image;
• an image forming unit configured to form the toner image on the image bearing member;
• and
• an optical sensor configured to detect image information, the optical sensor including:
• a light-emitting element configured to direct light to an image;
• a light-receiving element configured to receive light reflected by the image;
• a normal detection optical path configured to allow the light emitted by the light-emitting element and the light reflected from the image to follow a normal detection optical path during normal operation;
• a calibration reflecting plate disposed inside the optical sensor, configured to reflect light from the light-emitting element when sensitivity is calibrated;
• a calibration optical path from the light-emitting element to the light-receiving element that is different from the normal optical path utilized when the emitted light is reflected by the calibration reflecting plate;
• and
• a first optical function element disposed in the calibration optical path, configured to be switchable between a light permeating state, in which the light passes therethrough, and a light intercepting state, in which the light is blocked, when voltage is applied.