An image forming apparatus, including: an image signal generating portion configured to generate an image signal based on image data; a light source configured to emit a light beam based on the image signal; and a deflection device configured to deflect the light beam in a main scanning direction, wherein the image signal generating portion includes: a mode setting portion configured to set a plurality of modes including a mode in which a value of a pixel of the image data is not converted and a mode in which the value of the pixel in one or more lines is converted, to a plurality of areas into which a scanning area is divided in the main scanning direction, respectively; and a pixel value conversion portion configured to convert the value of the pixel in each mode in accordance with a position of the pixel in the main scanning direction.

An image forming apparatus includes: a light source that emits a laser beam; a polygon mirror that reflects the laser beam; a photoreceptor that is to be exposed to the laser beam reflected by the polygon mirror; a motor that rotates the polygon mirror; and a hardware processor capable of detecting sheet type, that is, type of a sheet conveyed in the image forming apparatus, wherein the hardware processor controls to rotate the motor at a first rotation speed until the sheet type is detected, and rotate the motor at a second rotation speed determined on the basis of the sheet type after detection of the sheet type.

An optical scanning device includes a casing (31). The casing (31) can be stacked in a plurality of stages in a state in which a lid member (32) has been removed, and includes a connection leg part (31e) extending from a predetermined position of the outside surface of a sidewall part (31b) to a lower side of a lower surface of the casing (31), and the connection leg part (31e) is provided with an engaged part (31g) for connection which is engaged with an engaging part (31d) formed at a sidewall part (31b) of another casing (31) when the casing (31) is stacked on an upper side of the other casing (31).

An optical scanning apparatus includes a deflector configured to deflect a light beam from a light source and scan a surface to be scanned in a main-scanning direction and a single imaging optical element configured to guide the light beam deflected by the deflector to the surface to be scanned. Scanning speeds of the light beam on the surface to be scanned at an on-axis image height and at an off-axis image height are different from each other, and conditions
0.0<(R1.sub.h/2+R2.sub.h/2)/(R1.sub.h/2R2.sub.h/2)<1.7 and
0.8<h/TC<2.0
are satisfied.

A scanning path of light includes a synchronization detection area A where a synchronization detection sensor 47 detects scanning light and an image writing area B where writing of the image data to a photosensitive drum 11 is performed by the scanning light, and a light amount change unit 100 is configured to reduce a change amount of a light amount in the synchronization detection area A as compared with the image writing area B.

Provided is an optical scanning device, which includes a bottomed box-like casing (31) in which a ceiling side is opened, a rotating polygon mirror (35) housed in the casing (31) to deflect and scan light beams emitted from a light source, a driving motor (41) fixed to a bottom wall of the casing (31) to drive the rotating polygon mirror (35), and a lid member (37) that closes the ceiling side of the casing (31) and is fixed to the casing (31) via a fixing mechanism (311), wherein the fixing mechanism (311) is provided adjacent to a minimum separation part (B) of a sidewall of the casing (31) in which a distance from the rotating polygon mirror (35) is minimum.

An image forming apparatus includes: a speed setting portion configured to set a rotation speed of a drive motor to one of a plurality of predetermined specific speeds; a measurement processing portion configured to, in each of a plurality of detection cycles in which light is detected after scanning by a polygon mirror, measure an interval between a detection timing of the light and an output timing at which a drive signal input to the drive motor of the polygon mirror first after the detection timing, is output; and an identification processing portion configured to identify a reference reflection surface that corresponds to a reference interval, based on the measured interval and the reference interval corresponding to a specific speed at a time when the measured interval was measured, the reference interval being among reference intervals that have been set in advance for each of the specific speeds.

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 apparatus includes a first polarizing member and a second polarizing member between a light source and a MEMS mirror that is a deflection mirror. The first polarizing member reflects a first polarization component included in a beam light emitted from the light source so as to squarely enter the MEMS mirror and passes a second polarization component having a phase difference of a half-wavelength with respect to the first polarization component. The second polarizing member is provided between the first polarizing member and the MEMS mirror to pass the first polarization component reflected by the first polarizing member therethrough twice before and after being reflected by the MEMS mirror to change the first polarization component into the second polarization component. A rotation axis of the MEMS mirror is parallel to an optical axis of the beam light immediately before being reflected by the first polarizing member.

The present disclosure provides a printing apparatus. The printing apparatus includes a light-emitting device, a reflector, and a light-sensing device. The light-emitting device emits printing light. The reflector is at least partially located in an irradiation region of the printing light, and has a surface reflecting the printing light at different positions to generate reflected light having different exit directions. The light-sensing device includes a light-sensing surface. The light-sensing surface is at least partially located in an irradiation region of the reflected light and senses the reflected light to generate a plurality of continuously-distributed light spots on the light-sensing surface with any adjacent light spots equally spaced apart.