A polygon mirror that includes a top surface, a bottom surface, and a plurality of reflective surfaces disposed between the top surface and the bottom surface. Each reflective surface of the plurality of reflective surfaces forms an angle θ with an adjacent reflective surface. Additionally, each reflective surface of the polygon mirror has an RMS surface roughness of about 1.5 nm or less.

An optical scanning device includes a light source, a photodetector, an optical element group, and a polygon mirror. The light source is configured to emit laser light. The photodetector is configured to detect a beam formed with the laser light. The optical element group is configured to guide the beam to the photodetector. The polygon mirror is configured to perform deflection scanning on the beam, which deflects the beam from a first end in one direction of a main scanning direction to a second end on a side opposite to the first end of the main scanning direction. The beam is incident on the same side of the photodetector when the beam is deflected toward the first end and the second end by the polygon mirror.

The detector that detects a light beam emitted from a light source of a second image forming device and reflected by a polygon mirror, and an adjustment device that performs adjustment processing of adjusting the velocity of the polygon mirror based on an output of the detector are provided. Before a first image forming device performs the image forming processing, the adjustment device performs the adjustment processing while causing the light source of the second image forming device to emit the light beam during a time period including at least a time period in which a photosensitive member of the second image forming device is emitted with the light beam. Before the adjustment processing is finished, the first image forming device starts to move a developing member to a developing position.

In one embodiment, a lidar system includes a light source configured to emit a first set of optical signals that include a first optical signal. The lidar system also includes a scanner that includes a polygon mirror configured to: rotate around an axis of rotation at a rotation rate, and direct the first set of emitted optical signals into a field of regard of the lidar system with the polygon mirror rotating at a first rotation rate. The lidar system further includes a receiver configured to detect a first received optical signal that includes a portion of the first optical signal that is scattered by a target located a distance from the lidar system. The lidar system also includes a controller configured to adjust the rotation rate of the polygon mirror for a second set of optical signals emitted by the light source.

An optical scanning device (12) includes cleaning holders (511, 512), light transmitting members (52), a linear member (54), a winding motor (55), and stoppers (56a, 56b). The two cleaning holders (511, 512) are coupled to the linear member (54). The linear member 54 is driven to circulate by the winding motor (55), whereby the two cleaning holders (511, 512) move and each cleaning member slides on a corresponding one of the light transmitting members (52). When the cleaning holders (511, 512) come into contact with the respective stoppers (56a, 56b), the stoppers (56a, 56b) restrict movement of the respective cleaning holders (511, 512) in one of directions of extension of the light transmitting members (52). A contact determining section (913) determines, based on a current value of the winding motor (55), that the cleaning holder (511, 512) has come into contact with the stopper (56a, 56h).

A scanning optical system, includes a mirror unit equipped with a first mirror surface and a second mirror surface each of which inclines to a rotation axis; and a light projecting system which includes at least one light source to emit a light flux toward the first mirror surface. A light flux emitted from the light source is reflected on the first mirror surface of the mirror unit, thereafter, reflected on the second mirror surface, and then, projected so as to scan in a main scanning direction onto an object in accordance with rotation of the mirror unit, and the light flux reflected on the second mirror surface is polarized in a range within an angle of ±30 degrees to a direction perpendicular to the main scanning direction on the object side.

A scanning optical system, includes a mirror unit equipped with a first mirror surface and a second mirror surface each of which inclines to a rotation axis; and a light projecting system which includes at least one light source to emit a light flux toward the first mirror surface. A light flux emitted from the light source is reflected on the first mirror surface of the mirror unit, thereafter, reflected on the second mirror surface, and then, projected so as to scan in a main scanning direction onto an object in accordance with rotation of the mirror unit, and in a case where a direction included in a main scanning plane is set to 0 degree, the light flux reflected on the second mirror surface is polarized in a range within an angle of ±30 degrees to the main scanning plane.

A scanning optical device includes a light source, a polygon mirror, a motor, a scanning optical system, a frame, and a seating surface. The scanning optical system comprises a first scan lens, a second scan lens, and a reflecting mirror. The reflecting mirror is arranged to reflect a light beam toward the second scan lens. The reflecting mirror is supported on the seating surface. The seating surface allows adjustment of an angle of the reflecting mirror. The reflecting mirror reflects the light beam in a direction from the base wall toward the open side. A part of the reflecting mirror that overlaps the seating surface as viewed in a direction of thickness of the reflecting mirror is exposed to an outside of the frame and accessible from a side of the frame opposite to an open side of the frame.

A scanning optical system, includes a mirror unit having a first mirror surface and a second mirror surface which incline to a rotation axis; and a light projecting system having a light source. A light flux emitted from the light source is reflected on the first mirror surface of the mirror unit, thereafter, reflected on the second mirror surface, and then, projected so as to scan in a main scanning direction onto an object in accordance with rotation of the mirror unit. In the case where a virtual plane is set in a range including the object, a light flux reflected on the second mirror surface has, upon entering the virtual plane, a cross sectional shape in which a length in a direction orthogonal to the main scanning direction is longer than a length in the main scanning direction.

A light reflection device comprises a reflection member having a reflection surface that is formed in a planar shape. The reflection surface reflects incident light. The reflection member performs a revolution and a rotation simultaneously. A direction of the revolution of the reflection member and a direction of the rotation of the reflection member are the same. Angular velocity of the revolution of the reflection member is equal to twice angular velocity of the rotation of the reflection member.