| 摘要 |
PROBLEM TO BE SOLVED: To obtain an optical scanner by which high-definition printing is obtained a simple constitution by suppressing deviation in an image formation position in a main scanning direction due to wavelength fluctuation or/and the divergence of focus (specially image surface curvature movement in a subscanning direction) in the subscanning direction associated with environmental fluctuation and a color image forming device using it. SOLUTION: This scanner comprises a deflecting means to deflect a light beam emitted by a light source means and a scanning optical means to perform image formation on a surface to be scanned with the light beam deflected by the deflecting means, and the scanning optical means possesses at least one refractive surface and also at least one diffraction surface, and when the synthesizing power of the refractive surface in the main scanning direction is set asϕr, and that of the diffraction surface in the main scanning direction is set asϕd and the rate of change of the refractive index of the material of an optical device forming the refractive surface to the oscillating wavelength of the light source means is set as dn/dλ(/nm), the condition of -2.37×10<-3> (/ nm)<(ϕr/ϕd)×(dn/dλ)<-0.9×10<-3> (/nm) is satisfied. |
