| 摘要 |
PROBLEM TO BE SOLVED: To suppress an image plane shift due to a temperature change.SOLUTION: When A(Z)=(1.897×10)Z+6744Z+0.5255, B(Z)=(2.964×10)Z+5645Z+0.6494, C(Z)=(3.270×10)Z+3589Z+0.5250, D(Z)=(5.016×10)Z+4571Z+0.8139, g1(fi)=fi{D(Z)-B(Z)}/12-5D(Z)/6+11B(Z)/6, and g2(fi)=fi{C(Z)-D(Z)}/12-5C(Z)/6+11A(Z)/6, an expression of g2(fi)≤&phgr;nM/&phgr;dM≤g1(fi), where &phgr;nM/&phgr;dM is a ratio of a refractive power &phgr;nM to a diffractive power &phgr;dM in a main scanning direction of a diffraction lens 3, is satisfied in a range of its focal length (fi)=10 to 22 [mm]. |
