Patent ID: 7719559

Claim:
An image forming apparatus, comprising: a light source having a plurality of light-emitting portions; a rotating polygonal mirror which scans a beam that is emitted from the light source; a photosensitive member which is exposed by the beam in one scanning cycle of the beam, the one scanning cycle comprising an image period during which exposure of the photosensitive member is performed based on image data and a non-image period during which the exposure of the photosensitive member is not performed by the beam even though the beam is emitted from the light source; a selection unit which selects a light-emitting portion from among the plurality of light-emitting portions, the selected light-emitting portion being used to emit the beam during the image period; a detection unit which detects a light power of the beam emitted from any of the plurality of light-emitting portions; and a control unit which makes the selected light-emitting portion emit the beam during the non-image period and executes auto light power control for the selected light-emitting portion in accordance with the detection result of the beam obtained by the detection unit, wherein the control unit does not execute the auto light power control for at least one of non-selected light-emitting portions from among the plurality of light-emitting portions.