According to one embodiment, an image reading apparatus includes an exposure unit, a light sensor, and a controller. The exposure unit selectively emits light to positions along a first scan direction to write pixels in accordance with a main scan line of image data. The light sensor is at a position to receive light from the exposure unit and is configured to output a synchronization signal according to the detection of the light emitted for each main scan line of image data. The controller adjusts a starting pixel position along the first scan direction for a main scan line of image data based on a change in an output interval of the synchronization signal resulting from a change in an intensity of light emitted by the exposure unit.

An optical element includes an optical surface for giving an optical effect to a light beam that passes therethrough. The optical surface includes a first region and a second region. The first region and the second region are smoothly continuous with each other. The optical surface has an absolute value of a maximum curvature at a boundary between the first region and the second region. The absolute value of the maximum curvature is smaller than a predetermined value.

An image forming apparatus includes a scanning means provided with a light source, a polygon mirror and a driving means for driving rotation of the polygon mirror; a photosensitive member, a developing means, and a detecting means for detecting a laser light from the light source. A controller controls to execute a light emission operation so that an area including an image forming area of the photosensitive member is irradiated with the laser light. The controller controls to execute a switching operation in which a rotational speed of the polygon mirror is switched from a first speed to a second speed different from the first speed. The controller controls to execute the light emission operation in a state in which the photosensitive member and the developing means are in contact and are rotating, and to execute the switching operation based on a detecting result of the detecting means in the light emission operation.

An image forming apparatus includes a plurality of photosensitive members; a scanner unit including light sources, a rotatable polygonal mirror, and reflecting members; and a fixing portion. Parts of the laser beams emitted from the light sources are reflected by the rotatable polygonal mirror toward the fixing device side, and rest parts of the laser beams are reflected by the rotatable polygonal mirror toward a side opposite from the fixing device side. Of the parts of the laser beams reflected by the rotatable polygonal mirror toward the fixing device side, the laser beam reflected toward the reflecting member provided at a position remotest from the rotatable polygonal mirror travels downward relative to a horizontal direction. A rotational axis of the rotatable polygonal mirror is inclined relative to a vertical direction.

Optical scanner and electrophotographic image forming apparatus are provided. The optical scanner includes a light source, configured to emit a light beam; an optical deflector, configured to deflect the light beam emitted from the light source; a first optical unit, arranged there-between and including a refraction unit and a diffraction unit; and a second optical unit, arranged in a light exit direction of the optical deflector and configured to make the light beam deflected by the optical deflector form an image on a scanning target surface. A range of a ratio of a refractive power Φ.sub.r to a diffractive power Φ.sub.d of the first optical unit in a main scanning direction is 0.3<Φ.sub.r/Φ.sub.d<0.5; and a range of a ratio of a refractive power Φ.sub.s to a diffractive power Φ.sub.n of the first optical unit in a sub scanning direction is 0.7<Φ.sub.s/Φ.sub.n<1.0.

Optical scanner and electrophotographic image forming device are provided. The optical scanner includes a light source; and a first optical unit, a deflection apparatus, and an f-θ lens, which are sequentially arranged along a primary optical axis direction of a light beam emitted from the light source. The light beam emitted from the light source is focused onto a scanning target surface after sequentially passing through the first optical unit, the deflection apparatus, and the f-θ lens. Optical scanning directions of the light beam emitted from the light source include a primary scanning direction and a secondary scanning direction which are perpendicular to each other, and along the primary scanning direction, the f-θ lens satisfies following expressions: SAG1>0, SAG2>0, and 0<(SAG1+SAG2)/d<0.8.

A laser scanning unit includes a light source portion, a scanning portion, a first correction portion, and a second correction portion. The light source portion outputs a plurality of light beams. The scanning portion scans the plurality of light beams to form a plurality of electrostatic latent images, respectively corresponding to a plurality of colors including at least one reference color and at least one non-reference color, in an image forming portion. The first correction portion applies an external mechanical force to an optical element located in a path of a reference beam, corresponding to the reference color, among the plurality of light beams to correct distortion of a scan line of the reference beam. The second correction portion controls the light source portion to correct distortion of a scan line of a non-reference beam, corresponding to the non-reference color, among the plurality of light beams.

A laser scanning unit includes a light source portion, a scanning portion, a first correction portion, and a second correction portion. The light source portion outputs a light beam. The scanning portion scans the light beam to form an electrostatic latent image in an image forming portion. The first correction portion applies an external mechanical force to an optical element located in a path of the light beam to correct inclination of a scan line of the light beam. The second correction portion controls the light source portion to correct distortion of the scan line of the light beam.

The present disclosure provides a light scanning unit and an electronic image forming apparatus including the light scanning unit. The light scanning unit includes a light source, a first optical unit, an optical deflector, and a second optical unit. The light source includes at least two light-emitting points; the at least two light-emitting points are distributed along a straight line; and an angle between an extension direction of a distribution line thereof and a main scanning direction or a secondary scanning direction of the light scanning unit includes an acute angle, where the main scanning direction is perpendicular to the secondary scanning direction. The first optical unit is configured to collimate at least two light beams emitted from the light source along the main scanning direction and to focus the at least two light beams emitted from the light source along the secondary scanning direction.

An image forming apparatus includes a photoreceptor; an image signal generating unit configured to generate an image signal based on input image data; a light emitting portion configured to emit light based on the image signal and expose the photoreceptor; a driving unit configured to drive the light emitting portion; a first substrate in which the driving unit is provided and a plurality of the light emitting portions is provided in a direction parallel to a rotational axis direction of the photoreceptor; an exposure head including the first substrate; a reference clock signal generating unit configured to generate a reference clock signal that is a clock signal of a constant frequency; a modulated clock signal generating unit configured to generate a modulated clock signal by performing spread spectrum on the reference clock signal, the modulated clock signal being a composite wave in which odd-order harmonics are combined with a fundamental wave when a triangular wave is subjected to Fourier series expansion; a transmission unit configured to superimpose the modulated clock signal on the image signal and transmit the superimposed signal to the first substrate; a second substrate on which the image signal generating unit, the modulated clock signal generating unit, and the transmission unit are provided; and an extraction circuit that is mounted on the first substrate and extracts the modulated clock signal from the superimposed signal transmitted from the transmission unit.