Abstract: An optical scan unit (10) is configured to include a light source (11), a divergent light conversion element (12) having such positive power as to convert divergent light from the light source (11) into convergent light to form a spot on a projection plane, an optical deflector (13) deflecting a light beam from the divergent light conversion element (12) to a first scan direction and a second scan direction which is orthogonal to the first scan direction, and a deflection angle conversion element 14 (14) having such negative power as to convert a deflection angle of the light deflected by the optical deflector (13).

Abstract: In a scanning optical apparatus including a single lens configured to convert a beam deflected by a polygon mirror into a spot-like image on a to-be-scanned surface, the lens satisfies the conditions: ?0.59<?1?0, ?0.46<?2?0.2, ?0.6?D1<0.43, and ?0.17?D2?0.16 where ?1 indicates an angle [deg] formed in a main scanning plane between a first optical axis and a reference line perpendicular to the to-be-scanned surface, ?2 indicates an angle [deg] formed in the main scanning plane between the first optical axis and a second optical axis, D1 indicates an amount of shift [mm] in the main scanning plane, of a point of intersection between the first optical axis and an incident-side lens surface, from the reference line, and D2 indicates an amount of shift [mm] in the main scanning plane, of a point of intersection between the second optical axis and an exit-side lens surface, from the first optical axis.

Abstract: An oscillating mirror module as a deflecting unit is disposed so that a movable mirror faces a plane where image carriers are arranged. A plurality of light source units are disposed within a plane parallel to the plane where the image carriers are arranged so that main light fluxes of light beams emitted from the light sources form predetermined angles with each other. The oscillating mirror module includes an incidence mirror that bends a plurality of light beams emitted from the light source units to direct the light beams to the movable mirror, and a separation mirror that separates the light beams scanned by the movable mirror into two opposite directions with respect to a cross-section including a surface normal of the movable mirror and perpendicular to the rotation axis of the movable mirror. A light collecting unit collects light beams so that output optical axes of the light beams corresponding to the light source units intersect on a surface of the movable mirror of the deflecting unit.

Abstract: In a scanning optical apparatus, a third optical element is configured such that a first optical axis defined as an optical axis of an incident-side lens surface of the third optical element is inclined in a main scanning plane with respect to a normal line extending from a scanning center on a target surface to be scanned and an intersection point between the first optical axis and the incident-side lens surface is shifted with respect to the normal line, and that a second optical axis defined as an optical axis of an emission-side lens surface is inclined in the main scanning plane with respect to the first optical axis and an intersection point between the second optical axis and the emission-side lens surface is shifted with respect to the first optical axis.

Abstract: In a scanning optical apparatus including a single lens configured to convert a beam deflected by a polygon mirror into a spot-like image on a scanned surface, an angle ?2 [deg] formed in a main scanning plane between the first optical axis and the second optical axis of the opposite lens surfaces of the lens satisfies the condition of ?0.6<?2??0.1, and at least one of the conditions ?0.5<?1<0 and ?0.1<D2<0.2 are satisfied where ?1 indicates an angle [deg] formed in the main scanning plane between the first optical axis and a reference line perpendicular to the scanned surface, and D2 indicates an amount of shift [mm] in the main scanning plane, of a point of intersection between the second optical axis and the exit-side lens surface, from the first optical axis.