| 摘要 |
PROBLEM TO BE SOLVED: To provide an inexpensive and energy-saving multibeam optical scanner in which a stable small beam spot is obtained despite of a temperature variation, and to provide an image forming apparatus furnished with the multibeam optical scanner. SOLUTION: The multibeam optical scanner is provided with a plurality of: light sources having a plurality of light emitting points composed of semiconductor lasers; first optical systems which guide a plurality of luminous fluxes emitted from the plurality of light emitting points to a deflecting means which deflects the luminous fluxes; and second optical systems which guide the plurality of luminous fluxes deflected with the defecting means onto a face to be scanned. The multibeam optical scanner is also provided with at least one deflecting means. The first optical systems have at least one resin lens having a diffracting face, the second optical systems have at least one resin optical element, the plurality of luminous fluxes pass through the first optical systems and the second optical systems corresponding to the plurality of luminous fluxes, and the following relation (A) is satisfied: ¾Δm'1+Δm'2+Δm'3¾<Wm/2, whereΔm'1 stands for a beam waist positional variation of main scanning due to the power variation of deflecting part occurring when the light source wavelength increases by 1 nm in the first optical systems,Δm'2 stands for a beam waist positional variation of main scanning due to the power variation of diffracting part occurring when the light source wavelength increases by 1 nm in the first optical systems,Δm'3 stands for a beam waist positional variation of main scanning due to the power variation occurring when the light source wavelength increases by 1 nm in the second optical systems, and Wm stands for the depth of main scanning beam diameter on the face to be scanned. COPYRIGHT: (C)2007,JPO&INPIT
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