Optical scanning device and image forming apparatus

An image forming apparatus moving a surface to be scanned in a sub-scanning direction and performing an electrophotographic process so as to form an image on the surface to be scanned, the image forming apparatus comprising an optical scanning device as a device for performing an exposure process in an electrophotographic process, the optical scanning device comprising:

• a light source unit having plural luminous sources;
• a light source driving unit modulating each luminous source in accordance with pixel information;
• an oscillating mirror supported on a twist beam as a rotation shaft, the oscillating mirror collectively deflecting light beams from the luminous sources and performing reciprocating scanning on the surface to be scanned;
• an imaging optical system imaging the light beams from the luminous sources on the surface to be scanned;
• and
• an oscillating mirror driving unit setting a scanning frequency in the neighborhood of a resonance frequency of the oscillating mirror within a resonance band, wherein
• the oscillating mirror driving unit adjusts the scanning frequency of the oscillating mirror in accordance with beam spot intervals in a sub-scanning direction.