Scanning optical apparatus, image forming apparatus and method for manufacturing a scanning lens

摘要

In a scanning optical apparatus including a light source, a light deflector having a reflecting surface, and a single scanning lens, a light flux deflected in a main scanning direction is focused on an image surface. The reflecting and image surfaces are conjugate to each other with respect to a sub scanning direction, Bmax×Bmin>0, and Dmax×Dmin<0 where Bmax and Bmin are a maximum value and a minimum value, respectively, of paraxial focal points, Dmax and Dmin are a maximum value and a minimum value, respectively, of midpoints of focal depth in the sub scanning plane, the values being determined with reference to the image surface, wherein the value of the image surface is 0 and the values on a farther-from-the-scanning-lens side behind the image surface have positive values.

主权项

1. A scanning optical apparatus comprising:
a light source configured to emit a light flux; a light deflector having a reflecting surface and configured to deflect the light flux emitted from the light source in a main scanning direction; and a single scanning lens configured to focus the light flux deflected by the light deflector on an image surface to be scanned, the scanning lens being configured such that: the reflecting surface and the image surface are conjugate to each other with respect to a sub scanning direction orthogonal to the main scanning direction,
Bmax×Bmin>0, andDmax×Dmin<0where Bmax is a maximum value of paraxial focal points in the sub scanning plane, Bmin is a minimum value of the paraxial focal points in the sub scanning plane, Dmax is a maximum value of midpoints of focal depth in the sub scanning plane, and Dmin is a minimum value of the midpoints of focal depth in the sub scanning plane, the values being determined with reference to the image surface, wherein the value of the image surface is 0 and the values of points on a farther-from-the-scanning-lens side behind the image surface have positive values,
wherein the following condition is satisfied:
|(Bmax+Bmin)/2|>|(Dmax+Dmin)/2|.