Light beam deflector
A light beam deflector for recording an image at a recording medium, at which a light beam modulated in accordance with image information passes through an incidence face of a cubic prism which is driven to rotate, the light beam deflector reflecting the light beam at a reflection surface, emitting the light beam through an emission face, and deflecting and scanning the light beam. An astigmatic difference correction surface is structured at at least one of the light beam incidence face and emission face of the cubic prism. The astigmatic difference correction surface is set with an inclination angle and inclination direction that are suitable for correcting astigmatism which arises due to the light beam passing through the incidence face, being reflected at the reflection surface and passing through the emission face.
1 . A light beam deflector, at which a light beam modulated in accordance with image information passes through an incidence face of a cubic prism which is driven to rotate, the light beam deflector reflecting the light beam at a reflection surface, emitting the light beam through an emission face, and deflecting and scanning the light beam, for recording an image at a recording medium, wherein
at least one of the light beam incidence face and emission face of the cubic prism includes an astigmatic difference correction surface, which is specified with an inclination angle and inclination direction suitable for correcting astigmatism that arises due to the light beam passing through the incidence face, being reflected at the reflection surface and passing through the emission face.
2 . The light beam deflector of claim 1 , wherein the astigmatic difference correction surface of the cubic prism is formed so as to include an isosceles trapezoid shape in a sectional view cut along an axial direction of the rotation.
3 . The light beam deflector of claim 1 , wherein the astigmatic difference correction surface of the cubic prism is formed so as to include a parallelogram shape in a plan view of directions orthogonal to an axis of the rotation.
4 . The light beam deflector of claim 1 , wherein the astigmatic difference correction surface is formed at an incidence face portion of the cubic prism, the astigmatic difference correction surface including an inclination in the form of a rotation about a sub-scanning direction of the reflection surface, the sub-scanning direction being a direction in which the reflection surface is inclined with respect to the incident light beam.
5 . The light beam deflector of claim 1 , wherein the astigmatic difference correction surface is formed at an incidence face portion of the cubic prism, the astigmatic difference correction surface including an inclination in the form of a rotation about a main scanning direction of the reflection surface, the main scanning direction being a direction in which the reflection surface is orthogonal with respect to the light beam.