To provide an image forming apparatus capable of suppressing reduction in transmittance caused by internal absorption of a resin lens by a simple system.
The image forming apparatus includes a light source including a plurality of light-emitting units capable of outputting a plurality of light beams at a wavelength of less than 450 nm, a rotary polygon mirror, a photoreceptor, a scanning optical lens system, detecting means, and a control unit. The detecting means includes a resin lens that condenses a scanned light beam, in which a plurality of light beams have different positions from each other in a sub-scanning direction on the resin lens. If the control unit determines that the level of a detection signal of the light beam from the detection means has decreased, the control unit instructs the rotary polygon mirror to output a light beam from another light-emitting unit in the plurality of light-emitting units upon carrying out a scanning process on the detection means.
OBAYASHI MAKOTO
WATANABE YOSHIKAZU
