| 摘要 |
PROBLEM TO BE SOLVED: To reduce the magnification error of a scanning image-forming lens and to effectively reduce the fluctuation of a vertical line in a multibeam scan ner. SOLUTION: In this multibeam scanner, plural beams from plural light sources 11 and 12 which can be independently driven and modulated in accordance with an image signal are deflected at constant angular velocity by a deflector 16 common to the beams, and the deflected beams are condensed as light spots separated from each other in a subscanning direction on a surface to be scanned 18 by the common scanning image-forming lens 17, then plural lines on the surface to be scanned are simultaneously scanned nearly at constant velocity. In the device, plural light sources are selected so thatΔK andΔλsatisfy a condition:Δλ/[25.4×2/δ×ΔK×θ}]<=1. Provided thatΔK andΔλare the quantities defined byΔK=(1/θ)(dL/dλ) when it is assumed that the angle of view equivalent to writing width isθ(rad), writing density isδ(dpi), the maximum wavelength difference between plural light sources isΔλand the writing width corresponding to the angle of view:θwith the beam of use reference wavelength:λis L (λ).
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