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.

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.

An image processing device includes a reception unit and a generation unit. The reception unit receives an input image signal, and a synchronization signal used to generate an output image signal on a basis of the input image signal. The generation unit generates, in a case in which the reception unit receives an initial synchronization signal of a unit of image reading, a synchronization signal for a subsequent input image signal. The reception unit receives the synchronization signal generated by the generation unit.

An image processing device includes a reception unit and a generation unit. The reception unit receives an input image signal, and a synchronization signal used to generate an output image signal on a basis of the input image signal. The generation unit generates, in a case in which the reception unit receives an initial synchronization signal of a unit of image reading, a synchronization signal for a subsequent input image signal. The reception unit receives the synchronization signal generated by the generation unit.

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.

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.

A reading device includes a position reference member and a reader. The position reference member has a reference pattern that includes a line extending in a prescribed direction. The position reference member is configured to relatively move in a direction orthogonal to the prescribed direction. The reader includes a plurality of sensor chips, each of the sensor chips including a plurality of pixels. The reference pattern corresponds to each of the sensor chips of the reader.

An image forming apparatus includes a photosensitive member; a charging device, a developing device, a transfer device, and a controller. The controller is capable of executing an operation in a first mode that an image forming operation is controlled so that an exposure start enable timing is set during movement of the photosensitive member through one full circumference from first passing, through an exposure position, of a region of the photosensitive member which has passed through a charging position, and executing an operation in a second mode that an image forming operation is controlled so that the exposure start enable timing is set after the movement of the photosensitive member. On the basis of image information of the first sheet of an image forming job, the controller selects an executing mode from a plurality of modes including at least the first mode and the second modes.

An image reading device comprises: a feeder that feeds a document along with a predetermined path; a first reading part that reads a first side of the document at a first position in the path and creates a first image; a second reading part that reads a second side of the document at a second position which is located posterior to the first position in the path and creates a second image; a synthesizing part that lays the first image and the second image on top of one another and creates a composite image; and a detecting part that detects a characteristic pattern of a specific document from the composite image created by the synthesizing part.

An image reading device comprises: a feeder that feeds a document along with a predetermined path; a first reading part that reads a first side of the document at a first position in the path and creates a first image; a second reading part that reads a second side of the document at a second position which is located posterior to the first position in the path and creates a second image; a synthesizing part that lays the first image and the second image on top of one another and creates a composite image; and a detecting part that detects a characteristic pattern of a specific document from the composite image created by the synthesizing part.