Optical member, optical scanning device, and image forming device

An optical member that refracts a light beam to diverge or focus the light beam, the optical member being a single lens made of a transparent material, comprising:

• at least three pairs of opposing surfaces, each pair of the at least three pairs of opposing surfaces comprising one surface on which the light beam is incident and the other surface from which the incident light beam is emitted,
• wherein
• each of the at least three pairs of opposing surfaces includes a lens part,
• curvatures of the lens parts at one side of surfaces of respective pairs of at least two pairs of the at least three pairs of opposing surfaces are different from each other,
• respective shortest distances between optical axes of the lens parts at one side of the surfaces of respective pairs of the at least two pairs of surfaces and reference sides, which are each any one of respective sides surrounding surfaces including the lens parts, are different from each other, and
• the optical member is selectively arranged to be installed in a housing by directing any one lens part of the lens parts at the one side of the surfaces to an incident side of the light beam while a corresponding one lens part of the lens parts at the other side of the surfaces is directed to an emission side of the light beam.

An optical scanning device comprising an optical member that refracts a light beam to diverge or focus the light beam, wherein

• the optical member includes at least three pairs of opposing surfaces,
• each of the at least three pairs of opposing surfaces includes a lens part,
• curvatures of the lens parts at one side of surfaces of the respective three pairs of opposing surfaces are all the same,
• each of the lens parts has a spherical surface on an incident side of the light beam and a toroidal surface on an emission side of the light beam, and
• the toroidal surface is a surface having a curvature in one direction but not having any curvature in a direction orthogonal to the one direction.