An optical scanning apparatus includes an optical box having a top surface that is constituted by a single lid. A first surface of the top surface is disposed closer to a rotary polygon mirror than a second surface and is disposed closer to a bottom surface of the optical box than an edge portion of a light deflector positioned farthest from the bottom surface. A third surface of a convex portion of the top surface is positioned farther from the bottom surface than the first surface. A lower edge portion of the convex portion is disposed outside a circumscribed circle of the rotary polygon mirror.

The image forming apparatus includes the optical scanning apparatus configured to scan a surface of an image bearing member provided in an image forming apparatus body with a laser beam. The optical scanning apparatus is inserted through an insertion opening formed in a frame member of the image forming apparatus body and supported by a support member mounted to the frame member. A housing of the optical scanning apparatus has an opening that allows passage of the laser beam, and includes a transparent dustproof member that covers the opening. On the surface side of the housing on which the dustproof member is provided, a plurality of projecting portions projecting with respect to the dustproof member are provided.

An image forming apparatus includes a light source, an optical deflector, an optical deflector casing, a bearing, and a sound absorption unit. The optical deflector reflects and deflects an optical beam emitted from the light source, having a rotational reflection member disposed on a rotation shaft to perform optical scanning. The optical deflector casing seals a space in which the optical deflector. The bearing rotatably supports the rotation shaft of the rotational reflection member with respect to the optical deflector casing, and includes at least portion exposed to an external space outside the sealed space of the optical deflector casing. The sound absorption unit is disposed opposite the exposed portion of the bearing with the external space therebetween.

A light scanning device includes a polygon mirror, a first incidence optical system, a second incidence optical system, a first scanning lens, and a second scanning lens. The polygon mirror includes a deflection surface ensuring entering of the first light beam and the second light beam at an identical timing. Assuming that a reflection point of a light beam on the deflection surface at time point at which the light beam reflected at the deflection surface passes through a position on an optical axis of a scanning lens, the second scanning lens is superimposed on the first scanning lens at different positions in a main-scanning direction and an optical axis direction such that a circle locus is along an offset curved line. The circle locus is a locus of a point corresponding to the reference point by the rotation of the polygon mirror.

A motor that rotates a rotation shaft of a polygon mirror is mounted on a motor board. A first photoelectric conversion element senses beam light reflected by each of a plurality of mirror surfaces. A sensing target portion is provided to the rotation shaft. A light sensor is disposed apart from the motor board and includes a light emitting portion and a second photoelectric conversion element. An amplification circuit amplifies a sense signal of the second photoelectric conversion element. A control device controls a timing of starting to form an electrostatic latent image on the basis of a sense signal of the first photoelectric conversion element. The control device identifies a scanning surface that is scanning the beam light on the basis of the sense signal of the second photoelectric conversion element amplified by the amplification circuit, and adjusts a pixel pitch of the electrostatic latent image.

An image forming apparatus includes a photosensitive member and a scanning unit including a light source, a rotatable polygonal mirror, and a sensor. The image forming apparatus includes setting of an operation in a first mode and setting of an operation in a second mode. The image forming apparatus further comprises, a surface identifying portion and a correction data storing portion configured to prestore correction data including first correction data for a first rotational speed and second correction data for a second rotational speed. Positional deviation in a main scan direction of laser light is corrected on the basis of the first correction data or the second correction data.

An optical scanning device includes a laser driver, an offset value determiner, a bias current setter, and a laser driver controller. The laser driver controls a laser light emitter to increase or decrease an excess of a current over a bias current in response to an input analog signal. The offset value determiner determines an offset value of the analog signal input to the laser driver based on a target light quantity of the laser light emitter. The bias current setter controls the bias current of the laser driver to a setting value in accordance with laser characteristics or lens transmittance of the laser light emitter. The laser driver controller controls a light emission quantity of the laser light emitter by inputting, to the laser driver, the analog signal offset based on a signal of the determined offset value.

An image forming apparatus includes: an exposure device; a housing including a support member that supports the exposure device; and a cooling device configured to make a refrigerant flow in a first direction in a space between the exposure device and the support member. The exposure device includes a first foot portion and a second foot portion aligned in the first direction and each protruding downward. The support member includes, on a surface thereof facing a lower surface of the exposure device, a first projection portion extending in a second direction intersecting the first direction and aligned with the first foot portion in the second direction, and a second projection portion extending in the second direction, aligned with the second foot portion in the second direction, and having a plurality of portions spaced apart from each other in the second direction. The first foot portion and the second foot portion are separated from the support member.

An optical scanning apparatus includes a deflector including a deflection surface, on which first and second light beams are deflected to scan first and second scanned surfaces in a main scanning direction, and first and second optical systems configured to guide the first and second light beams deflected by the deflection surface to the first and second scanned surfaces wherein the first optical system includes first refractive element, a second refractive element, and first reflective element, wherein the second optical system includes a third refractive element, a second reflective element, a fourth refractive element, and a third reflective element, wherein at least one of the first refractive element and the third refractive element includes a specific optical surface, and wherein distances on the optical axis from an axial deflection point on the deflection surface to the second and fourth refractive elements differ from each other.

A cover closes a first opening of a main box portion. A second opening is formed in a unit housing of an optical scanning unit to externally expose a connector mounted on an electronic board. The unit housing has a protruding inner frame portion and a wiring portion. The protruding inner frame portion protrudes from an outer surface of the unit housing and surrounds the second opening. The cover includes a protruding outer frame portion that protrudes from an inner surface of the cover and surrounds the protruding inner frame portion. A top portion of the protruding inner frame portion is formed along an inner-side portion of the protruding outer frame portion on an inner surface of the cover. A top portion of the protruding outer frame portion is formed along an outer-side portion of the protruding inner frame portion on the outer surface of the unit housing.