Image forming apparatus

An image forming apparatus comprising:

• a photosensitive member;
• a polygon mirror rotated by a drive unit and having a plurality of reflection surfaces;
• an exposure unit configured to form a latent image on the photosensitive member by reflecting a laser beam emitted from a light source with the polygon mirror and by scanning the photosensitive member;
• a developing unit configured to form a toner image on the photosensitive member by causing toner to adhere to the latent image formed on the photosensitive member;
• a transfer unit configured to transfer the toner image formed on the photosensitive member onto a recording material directly or via an intermediate transfer member;
• a fixing unit configured to fix the toner image by heating the recording material onto which the toner image has been transferred;
• and
• a control unit configured to control operation of the image forming apparatus in a plurality of operation modes including a normal mode and a low speed mode having a slower process speed than the normal mode in accordance with an input instruction, the process speed defining a speed of the recording material passing through the fixing unit,
• wherein the control unit controls the polygon mirror of the exposure unit to use all of the plurality of reflection surfaces to reflect the laser beam when an instruction designating the normal mode as the operation mode is input, or when no instruction designating a specific operation mode is input, and
• the control unit controls making the process speed of the low speed mode faster than 0.5 times the process speed of the normal mode, rotating the polygon mirror faster than in the normal mode, and controlling the polygon mirror of the exposure unit to use only some of the plurality of reflection surfaces to reflect the laser beam, when an instruction designating the low speed mode as the operation mode is input.