A reading module has a light source, an optical system imaging, as image light, reflected light of light radiated from the light source to a document, a sensor where a plurality of imaging regions for converting the image light imaged by the optical system into an electrical signal are arranged next to each other in the main scanning direction, and a housing the light source, the optical system, and the sensor. The optical system has a mirror array where a plurality of reflection mirrors whose reflection surfaces are aspherical concave surfaces are coupled together in an array in the main scanning direction, and an aperture stop portion adjusting the amount of the image light reflected from the reflection mirror. The amount of the image light striking the reflection mirror is increasingly small from opposite end parts of the reflection mirror toward its central part in the main scanning direction.

Provided is an image forming apparatus configured to acquire a density of a test print image at each position in the main scanning direction, which is read by the image reading unit after a first test print image is formed, to correct a setting value of an exposure amount of an exposure device to a first light amount, which is higher than a reference light amount that is an exposure amount when the first test print image is formed, in an area where the acquired density is lower than a target density, to correct the exposure amount of the exposure device to a second light amount, which is lower than the reference light amount, in an area where the acquired density is higher than the target density, and to form a second test print image. On the basis of the second test print image, density correction is performed.

An image forming apparatus includes: a halftone processing unit configured to perform halftone processing on image data by a dither matrix that includes a plurality of submatrices and decide an exposure region of an image. In at least one of a first dither matrix corresponding to a first section, and a second dither matrix corresponding to a second section adjacent to the first dither matrix in the main scanning direction and corresponding to a second section different from the first section in tone value, at least a size of an exposure region of an image formed by using a first submatrix corresponding to a predetermined tone value in the dither matrix and a size of an exposure region of an image formed by using a second submatrix corresponding to the predetermined tone value are different.

A light scanning device includes: a first semiconductor laser 44a that emits a light beam L1; a polygonal mirror 42 that deflects the light beam L1; a reflective mirror 64a that reflects the light beam L1 deflected by the polygonal mirror 42 and causes the light beam L1 to enter a photosensitive drum 13; and a BD sensor 72 that detects the light beam L1 deflected by the polygonal mirror 42. The light scanning device scans the photosensitive drum 13 with the light beam L1 and set scanning timing of the photosensitive drum 13 using the light beam L1 based on detection timing of the light beam L1 using the BD sensor 72. The BD sensor 72 is arranged in the position farther from the polygonal mirror 42 than the last reflective mirror 64a that reflects the light beam L1 immediately before entering the photosensitive drum 13 and arranged inside a scanning angle range of the light beam L1 corresponding to an effective scan area of the photosensitive drum 13.

An image forming apparatus includes a control unit: starting up a rotary polygon mirror based on a first signal output by a driving unit thereof; causing a light source to emit a laser-beam while controlling a rotational speed of the rotary polygon mirror based on the first signal to acquire a second signal output from a detecting unit of the laser-beam; turning off the light source after acquiring a phase relation between the first and second signals; causing a charging unit to charge a photosensitive member; making the laser-beam to enter onto the detecting unit without exposing the photosensitive member based on the phase relation in response to the rotational speed reaching a target speed; controlling the rotational speed based on the second signal in response to the laser-beam being entered; and starting image formation in response to the rotational speed converging within a predetermined range including the target speed.

Provided is an image forming apparatus configured to acquire a density of a test print image at each position in the main scanning direction, which is read by the image reading unit after a first test print image is formed, to correct a setting value of an exposure amount of an exposure device to a first light amount, which is higher than a reference light amount that is an exposure amount when the first test print image is formed, in an area where the acquired density is lower than a target density, to correct the exposure amount of the exposure device to a second light amount, which is lower than the reference light amount, in an area where the acquired density is higher than the target density, and to form a second test print image. On the basis of the second test print image, density correction is performed.

For measuring the oscillation amplitude of a scanner mirror in a projection system of a motor vehicle headlight, a laser beam generated by a laser source is directed onto the scanner mirror and reflected by the latter so that the laser beam thus reflected is incident on a detector device (20) that has a plurality of photodetector elements (Q1, Q2, Q3, Q4) and there describes a curve (P) based on the oscillation movement of the scanner mirror. The center point of the curve (P) is offset by an offset value (x.sub.offset, y.sub.offset) from the center of the detector device (20). The time period (t.sub.ON,X, t.sub.ON,Y) in which the curve passes through the specific detector region (R.sub.X, R.sub.Y) that corresponds to a coordinate to be measured is determined; and the oscillation amplitude (x.sub.pp, y.sub.pp) in the direction of the specific coordinate is determined using the ratio of the time period (t.sub.ON,X, t.sub.ON,Y) determined in this manner to the total duration (T) of an oscillation period and the offsets (x.sub.offset, y.sub.offset).

A first receiving recess (44d) and a second receiving recess (44e) are formed on a surface of the housing, on which a pair of image forming lenses (47) are placed, to receive a first temperature sensor (101a) and a second temperature sensor (101b), and are formed in positions, in which thermal deformation characteristics of the housing are approximately identical at one side and the other side of a first straight line K1, while interposing the first straight line K1 therebetween.

A light beam scanning device scans a luminous flux irradiated from a light source and deflected by a deflector to a scanned surface through an optical system having a set of mirrors. A apparatus, such as the light beam scanning device, further includes a scanning line curve adjusting device to bend a first mirror of the set of mirrors so as to correct a curve in a scanning line on the scanned surface, and a scanning line tilt adjusting device to change orientation of a second mirror of the set of mirrors so as to correct a tilt in the scanning line on the scanned surface. The light beam scanning device may be provided in an image forming apparatus.

A light source control device, includes circuitry to: apply a threshold current, a first emission current, and a first correction current to a light source to drive the light source to emit light to form a first pixel, and apply the threshold current, a second emission current, and a second correction current to the light source to drive the light source to emit light to form a second pixel, wherein the circuitry calculates a value of the second correction current by multiplying a value of the first correction current by a ratio of a value of the second emission current to a value of the first emission current, the value of the second emission current being greater than the value of the first emission current.