An optical scanning device includes a deflector for deflecting a light beam to optically scan a scanned region on a scanned surface in a main scanning direction, and an imaging optical system for guiding the light beam deflected by the deflector, to the scanned surface. The imaging optical system includes an imaging optical element in which, in the main scanning direction, a distance to an optical axis from one effective end portion through which a light beam that enters one end portion of the scanned region passes is longer than a distance to the optical axis from another effective end portion through which a light beam that enters another end portion of the scanned region passes. In the imaging optical element, a thickness in an optical axis direction of the one effective end portion is thinner than a thickness in the optical axis direction of the other effective end portion.

An optical scanning device includes a deflector for deflecting a light beam to optically scan a scanned region on a scanned surface in a main scanning direction, and an imaging optical system for guiding the light beam deflected by the deflector, to the scanned surface. The imaging optical system includes an imaging optical element in which, in the main scanning direction, a distance to an optical axis from one effective end portion through which a light beam that enters one end portion of the scanned region passes is longer than a distance to the optical axis from another effective end portion through which a light beam that enters another end portion of the scanned region passes. In the imaging optical element, a thickness in an optical axis direction of the one effective end portion is thinner than a thickness in the optical axis direction of the other effective end portion.

A light scanning device includes a deflection unit, a first imaging lens, and a second imaging lens. The first imaging lens has a bottom surface adhesively secured to a housing via a plurality of adhesion portions. The second imaging lens has a bottom surface adhesively secured to a top surface of the first imaging lens via a plurality of adhesion portions. The plurality of the adhesion portions interposed between the first imaging lens and the housing are symmetrically located with respect to a center position of the first imaging lens in a main-scanning direction. The adhesion portions interposed between the first imaging lens and the second imaging lens are symmetrically located with respect to the center position of the first imaging lens in the main-scanning direction, and are located outside in the main-scanning direction with respect to the adhesion portions between the first imaging lens and the housing.

A light scanning device includes a deflection unit, a first imaging lens, and a second imaging lens. The first imaging lens has a bottom surface adhesively secured to a housing via a plurality of adhesion portions. The second imaging lens has a bottom surface adhesively secured to a top surface of the first imaging lens via a plurality of adhesion portions. The plurality of the adhesion portions interposed between the first imaging lens and the housing are symmetrically located with respect to a center position of the first imaging lens in a main-scanning direction. The adhesion portions interposed between the first imaging lens and the second imaging lens are symmetrically located with respect to the center position of the first imaging lens in the main-scanning direction, and are located outside in the main-scanning direction with respect to the adhesion portions between the first imaging lens and the housing.

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).

In an image forming apparatus a controller starts a heater to heat up in response to a print command In a first case where temperature of the fixing device at a timing of reception of the print command is lower than a first threshold value, the controller starts rotating a first motor, and subsequently starts rotating a second motor before the conveying device conveys the sheet according to the received print command. The first threshold value is lower than the target temperature. In a second case where the temperature of the fixing device at the timing of reception of the print command is higher the first threshold value, the controller starts rotating the second motor, and subsequently starts rotating the first motor before the conveying device conveys the sheet according to the received print command.

An image forming method exposes a surface of an image bearer with light according to an image pattern including an image portion to form an electrostatic latent image, and includes: setting, among pixels constituting the image portion, at least a group of pixels existing at a boundary with respect to a non-image portion as a non-exposure pixel group, and at least a group of pixels existing at a boundary with respect to the non-exposure pixel group as a high power exposure pixel group; specifying, among the pixels constituting the image portion, a predetermined pixel as a target pixel, and a group of pixels existing at a boundary with respect to the non-image portion close to the target pixel as a boundary pixel group; and specifying a light power value of the target pixel based on image identification information acquired from the pixels constituting the image portion.

An image forming method exposes a surface of an image bearer with light according to an image pattern including an image portion to form an electrostatic latent image, and includes: setting, among pixels constituting the image portion, at least a group of pixels existing at a boundary with respect to a non-image portion as a non-exposure pixel group, and at least a group of pixels existing at a boundary with respect to the non-exposure pixel group as a high power exposure pixel group; specifying, among the pixels constituting the image portion, a predetermined pixel as a target pixel, and a group of pixels existing at a boundary with respect to the non-image portion close to the target pixel as a boundary pixel group; and specifying a light power value of the target pixel based on image identification information acquired from the pixels constituting the image portion.

A housing of an optical scanning device includes a first abutting portion and a second abutting portion. In the optical scanning device, an optical axis adjustment and a focal position adjustment in a main scanning direction and a sub scanning direction are conducted in a state where a part of a holder that holds a light source unit for emitting multi-beam light abuts on the first abutting portion and in a state where a part of a peripheral edge of an optical element that has both a collimator lens function and a cylindrical lens function abuts on the second abutting portion. Furthermore, a beam pitch of the multi-beam light is adjusted by rotating the holder around an optical axis in a state where the holder abuts on the first abutting portion.

A housing of an optical scanning device includes a first abutting portion and a second abutting portion. In the optical scanning device, an optical axis adjustment and a focal position adjustment in a main scanning direction and a sub scanning direction are conducted in a state where a part of a holder that holds a light source unit for emitting multi-beam light abuts on the first abutting portion and in a state where a part of a peripheral edge of an optical element that has both a collimator lens function and a cylindrical lens function abuts on the second abutting portion. Furthermore, a beam pitch of the multi-beam light is adjusted by rotating the holder around an optical axis in a state where the holder abuts on the first abutting portion.