An image reading apparatus including: an illumination device configured to illuminate an original; and a solid-state image sensor configured to receive and convert a reflected light from the original into an image signal, wherein the illumination device includes: a plurality of light emitting elements; and a light guide configured to guide light emitted from the light emitting elements toward the original, wherein the light guide includes: a deflection surface configured to deflect the light emitted from the light emitting elements to direct the light toward the original; and an emission surface configured to emit the light deflected by the deflection surface toward the original, wherein the deflection surface has a plurality of first curved optical surfaces provided side by side in a longitudinal direction of the light guide, and wherein the emission surface has a plurality of second curved optical surfaces provided side by side in the longitudinal direction.

An image forming apparatus includes a photoconductor, an optical scanner, a development device, a movable density sensor, a density sensor driver, and a processor. The optical scanner includes a light source to emit light, and irradiates a surface of the photoconductor in a main scanning direction with the light to form a latent image on the surface of the photoconductor. The development device develops the latent image into a toner image. The density sensor detects unevenness in density of the toner image in the main scanning direction. The density sensor driver moves the density sensor in the main scanning direction. The processor corrects a driving signal for the light source according to image data to reduce the unevenness in density in the main scanning direction, according to positional data of the density sensor in the main scanning direction and an output value of the density sensor.

An image reading apparatus includes a light emitting element, a luminance calculating unit, a light amount setting unit, and a storing unit. The light amount setting unit, in each line period, causes the light emitting element to emit a light with gradually changing a reference light amount from a reference light amount set as a default value from among a plurality of reference light amounts stored in the storing unit, identifies a reference light amount so that the luminance calculated by the luminance calculating unit is within a predetermined range, sets the identified reference light amount as a default value for the next line period, and causes the storing unit to store that reference light amount.

A lighting apparatus includes a first illumination portion and a second illumination portion. The first illumination portion and the second illumination portion respectively include a bar-like light guide whose shape of an end face of an end portion includes a part of a circle, an ellipse or a parabola, and light source elements that are provided to face the end face of the end portion of the light guide. In the light guide of the second illumination portion, light enters a determined range in which a focus of the shape of the end face of the end portion of the light guide is included. In the light guide of the first illumination portion, light enters a range that is not the determined range in which the focus of the shape of the end face of the light guide is included.

A reading module includes: a light source for applying light to a document; an optical system for forming an image as image light from reflected light of the light applied from the light source to the document; and a sensor in which a plurality of sensor chips for converting the image light formed by the optical system to electric signals are disposed in adjacency to one another in a main scanning direction. The optical system includes: a mirror array in which a plurality of reflecting mirrors whose reflecting surfaces are aspheric surfaces are coupled in array in the main scanning direction; and apertures provided between the reflecting mirrors and the sensor chips, respectively, to regulate light quantity of the image light reflected by the individual reflecting mirrors. The specular-surface number of the reflecting mirrors is set to an integral multiple of the number of the sensor chips.

An image-forming apparatus includes a light-irradiation unit configured to move a spot of laser light on a surface of a photosensitive member at a non-constant scanning velocity in a main scanning direction to form a latent image on the photosensitive member, an image data correcting unit configured to correct a length in the main scanning direction of image data by inserting one or more image data pieces into the image data, the number of the image data pieces increasing as the scanning velocity increases, and/or extracting one or more image data pieces from the image data, the number of the image data pieces increasing as the scanning velocity decreases, and a brightness correcting unit configured to correct a brightness of the laser light so that an emission brightness increases as the scanning velocity increases and/or the emission brightness decreases as the scanning velocity decreases.

An exposure unit includes a light-emitting element array and a lens array. The light-emitting element array includes a plurality of light-emitting elements that are disposed in a first direction and each emit a light beam. The lens array faces the light-emitting element array in a second direction that is orthogonal to the first direction, and focuses the light beams emitted from the respective light-emitting elements. The following expression [3] is satisfied. A symmetric property, determined from the following expression [1], of a light amount distribution in the first direction of at least one of the light beams focused by the lens array satisfies the following expression [2].

S=|(HLHR)/(XE/2)|[1]

0S0.65[2]

LoLB[3]

An image-forming apparatus includes a light-irradiation unit configured to move a spot of laser light on a surface of a photosensitive member at a non-constant scanning velocity in a main scanning direction to form a latent image on the photosensitive member, an image data correcting unit configured to correct a length in the main scanning direction of image data by inserting one or more image data pieces into the image data, the number of the image data pieces increasing as the scanning velocity increases, and/or extracting one or more image data pieces from the image data, the number of the image data pieces increasing as the scanning velocity decreases, and a brightness correcting unit configured to correct a brightness of the laser light so that an emission brightness increases as the scanning velocity increases and/or the emission brightness decreases as the scanning velocity decreases.

An optical scanning device includes a scanning member, a plurality of light sources, a first reflection mirror, and a second reflection mirror. The scanning member scans incident laser beams in a predetermined main scanning direction. The plurality of light sources emit the laser beams from positions that are different along a sub scanning direction that is perpendicular to an optical axis direction of the laser beams and the main scanning direction. The first reflection mirror is inclined around the main scanning direction as a rotation axis, is inclined around the sub scanning direction as another rotation axis, and reflects the laser beams emitted from the light sources. The second reflection mirror is inclined around the main scanning direction as a rotation axis, is inclined around the sub scanning direction as another rotation axis, and reflects the laser beams reflected by the first reflection mirror toward the scanning member.

An image reading apparatus includes a light emitting element, a luminance calculating unit, a light amount setting unit, and a storing unit. The light amount setting unit, in each line period, causes the light emitting element to emit a light with gradually changing a reference light amount from a reference light amount set as a default value from among a plurality of reference light amounts stored in the storing unit, identifies a reference light amount so that the luminance calculated by the luminance calculating unit is within a predetermined range, sets the identified reference light amount as a default value for the next line period, and causes the storing unit to store that reference light amount.