Patent ID: 7324250

Claim:
An image forming apparatus comprising: a light source section for emitting a light beam; an oscillating mirror adapted to be reciprocatingly oscillated while reflecting the light beam emitted from said light source section onto a surface of a photosensitive drum so as to scan the surface of said photosensitive drum with the reflected light beam and to form an electrostatic latent image corresponding to image data onto the surface of a photosensitive drum; and an oscillating-mirror drive unit for supplying to said oscillating mirror a drive signal for reciprocatingly oscillating said oscillating mirror within a given angular range, said oscillating-mirror drive unit including: a detection section for detecting a variation amount of a drive voltage of the drive signal if a power supply voltage is varied due to change in load condition of the image forming apparatus and; and a drive-frequency alteration section for altering a drive frequency of the drive signal depending on the variation amount of the drive voltage detected by said detection section; wherein said drive-frequency alteration section is operable, when the drive voltage is lowered, to generate a lower drive frequency than an existing drive frequency of the drive signal, and, when the drive voltage is increased, to generate a higher drive frequency than an existing drive frequency of the drive signal.