Patent ID: 7643190

Claim:
A method for controlling an image forming apparatus including a first optical scanning portion and a second optical scanning portion, wherein each of the first and second optical scanning portions has a laser emitting unit, a rotatable polygonal mirror arranged to expose and scan a different image bearing member with laser light from the laser emitting unit, and a driving unit arranged to rotate the rotatable polygonal mirror, the image forming apparatus being capable of forming a color image by causing the first and second optical scanning portions to expose and scan the respective image bearing members and to transfer respective images to a moving medium, the method comprising: starting rotation control of controlling rotation of the driving unit; after starting rotation control of controlling rotation of the driving unit, forming a color image by using the first and second optical scanning portions in response to an instruction to start image formation of a color image and forming a monochrome image by using the first optical scanning portion without using the second optical scanning portion in response to an instruction to start image formation of a monochrome image; detecting a remaining amount of a developer used in forming the color or monochrome image; and performing the rotation control on the driving unit of the first scanning unit and not starting the rotation control on the driving unit of the second scanning unit if absence of a developer used for an image to be formed by the second optical scanning portion is detected and presence of a developer used for an image to be formed by the first optical scanning portion is detected.