The present disclosure provides an optical scanning apparatus and an electronic image-forming apparatus. The optical scanning apparatus includes a light source; a first optical unit; an optical deflector, configured to deflect the light beam emitted from the first optical unit; and a second optical unit, configured to guide the light beam deflected by the optical deflector on a scanned target surface for forming an image. An image height on the scanned target surface satisfies an expression: Y=fc×tan(B×θ), where Y denotes the image height on the scanned target surface, fc denotes an image-forming characteristic coefficient of the second optical unit, B denotes a scanning coefficient of the second optical unit, θ denotes an effective scanning angle of the optical scanning apparatus, and all region or a partial region in effective scanning range of the second optical unit satisfies a condition: 0.7≤B≤0.9.

The present disclosure provides an optical scanning apparatus and an electronic image-forming apparatus. The optical scanning apparatus includes a light source; a first optical unit; an optical deflector, configured to deflect the light beam emitted from the first optical unit; and a second optical unit, configured to guide the light beam deflected by the optical deflector on a scanned target surface for forming an image. An image height on the scanned target surface satisfies an expression: Y=fc×tan(B×θ), where Y denotes the image height on the scanned target surface, fc denotes an image-forming characteristic coefficient of the second optical unit, B denotes a scanning coefficient of the second optical unit, θ denotes an effective scanning angle of the optical scanning apparatus, and all region or a partial region in effective scanning range of the second optical unit satisfies a condition: 0.7≤B≤0.9.

A light-emitting device includes: a first light-emitting unit that extends in one direction and that has a first emission surface that emits light located along the one direction; a second light-emitting unit that is located in the one direction with respect to the first light-emitting unit, that extends in the one direction, and that has a second emission surface that emits light located along the one direction; a cleaning unit that is capable of moving in the one direction and an opposite direction that is opposite to the one direction to clean the first emission surface; a transmission part that extends from the cleaning unit in the one direction and that transmits a moving force for moving the cleaning unit to the cleaning unit; and an extending part that extends from the transmission part in the one direction to elongate the transmission part. When the cleaning unit is positioned furthest in the opposite direction, an end of the extending part in the one direction is located further in the one direction than a midpoint between an end of the first light-emitting unit in the one direction and an end of the second light-emitting unit in the one direction.

A light-emitting device includes: a first light-emitting unit that extends in one direction and that has a first emission surface that emits light located along the one direction; a second light-emitting unit that is located in the one direction with respect to the first light-emitting unit, that extends in the one direction, and that has a second emission surface that emits light located along the one direction; a cleaning unit that is capable of moving in the one direction and an opposite direction that is opposite to the one direction to clean the first emission surface; a transmission part that extends from the cleaning unit in the one direction and that transmits a moving force for moving the cleaning unit to the cleaning unit; and an extending part that extends from the transmission part in the one direction to elongate the transmission part. When the cleaning unit is positioned furthest in the opposite direction, an end of the extending part in the one direction is located further in the one direction than a midpoint between an end of the first light-emitting unit in the one direction and an end of the second light-emitting unit in the one direction.

According to an embodiment, a signal generation circuit includes a generation unit configured to generate a second clock signal from division of a first clock signal and generate a timing signal with a cycle length that is a sum of a predetermined number of half-cycle periods of the second clock signal. A period changing unit of the signal generation circuit is configured to adjust the cycle length of the timing signal by changing a length of at least one half-cycle period of the second clock signal. An output unit of the signal generation circuit is configured to output the second clock signal and the timing signal.

According to an embodiment, a signal generation circuit includes a generation unit configured to generate a second clock signal from division of a first clock signal and generate a timing signal with a cycle length that is a sum of a predetermined number of half-cycle periods of the second clock signal. A period changing unit of the signal generation circuit is configured to adjust the cycle length of the timing signal by changing a length of at least one half-cycle period of the second clock signal. An output unit of the signal generation circuit is configured to output the second clock signal and the timing signal.

An image forming apparatus includes an exposure unit provided with a rotatable polygon mirror including a plurality of reflecting surfaces for scanning a light beam emitted from a light source to expose a photosensitive member with the light beam according to image information. A determining unit determines an end of lifetime of the exposure unit based on a detecting result of density of a toner image detected by two detecting units at a first timing and a detecting result of density of the toner image detected by the two detecting units at a second timing after the first timing.

An image forming apparatus includes an exposure unit that reflects a laser beam emitted from a light source by a polygon mirror having a plurality of reflection surfaces to form a latent image on a photosensitive member, and a control unit that controls the image forming apparatus in a plurality of operation modes including a normal mode and a low speed mode having a slower process speed than the normal mode. The control unit controls the polygon mirror to use all of the plurality of reflection surfaces to reflect the laser beam when in the normal mode. When in the low speed mode, the control unit makes the process speed faster than 0.5 times that of the normal mode, rotates the polygon mirror faster than in the normal mode, and controls the polygon mirror to use only some of the plurality of reflection surfaces to reflect the laser beam.

An image forming apparatus includes an exposure unit that reflects a laser beam emitted from a light source by a polygon mirror having a plurality of reflection surfaces to form a latent image on a photosensitive member, and a control unit that controls the image forming apparatus in a plurality of operation modes including a normal mode and a low speed mode having a slower process speed than the normal mode. The control unit controls the polygon mirror to use all of the plurality of reflection surfaces to reflect the laser beam when in the normal mode. When in the low speed mode, the control unit makes the process speed faster than 0.5 times that of the normal mode, rotates the polygon mirror faster than in the normal mode, and controls the polygon mirror to use only some of the plurality of reflection surfaces to reflect the laser beam.

An image reading apparatus includes a circuit board on which a plurality of light sources are disposed in a longitudinal direction, a light guide portion including a first holding portion configured to hold the circuit board, and a second holding portion configured to hold the circuit board, a support member configured to support the light guide portion, and an image reading unit configured to read image information by performing photoelectric conversion on reflected light reflected by a sheet which has received light emitted from the light guide portion. The support member includes a projecting portion disposed between the first holding portion and the second holding portion in the longitudinal direction, the projecting portion facing and projecting toward the circuit board held by the first holding portion and the second holding portion.