Patent ID: 7253937

Claim:
A multi-beam optical scanning device, comprising: a plurality of light sources; a deflection unit configured to deflect a plurality of light beams from the light sources; a first optical system configured to guide the light beams from the light sources to the deflection unit; and a second optical system configured to guide the light beams deflected by the deflection unit to a scanning surface;, wherein the first optical system includes a first lens that couples the light beams from the light sources, and a second lens that guides the light beams from the first lens to the deflection unit, said second lens being an anamorphic element having power at least in a sub scanning direction, at least the second lens includes a diffracting surface having a power, and assuming a magnification in a main scanning direction of a whole optical system of the multi-beam optical scanning device is represented by βm 0 , a magnification in the sub scanning direction of the whole optical system of the multi-beam optical scanning device is represented by βs 0 , and a magnification in the sub scanning direction of the second optical system is represented by βs 2 , the following relation (1) is satisfied: |β m 0 |>|βs 0|, and |β s 0 |>|βs 2| (1), and assuming the power of the diffracting surface of the first lens in the main scanning direction is represented by P 1 m, the power of the diffracting surface of the first lens in the sub scanning direction is represented by P 1 s, and the power of the diffracting surface of the second lens in the sub scanning direction is represented by P 2 s, the following relation (2) is satisfied: | P 2 s|>|P 1 m |, and | P 2 s|>|P 1 s| (2).