An image signal processing device includes a reference signal generating portion, a determination portion, and an extraction portion. The reference signal generating portion generates and outputs a reference signal that sequentially transmits reference pulses shifted from horizontal synchronization pulses on a horizontal synchronization signal by a predetermined shift time. The determination portion determines whether the horizontal synchronization pulses are normal by comparing time differences between input of the horizontal synchronization pulses and input of the reference pulses with the shift time. The extraction portion extracts line image data points from an image signal in synchronization with the input of the horizontal synchronization pulses that have been determined as normal.

An image signal processing device includes a reference signal generating portion, a determination portion, and an extraction portion. The reference signal generating portion generates and outputs a reference signal that sequentially transmits reference pulses shifted from horizontal synchronization pulses on a horizontal synchronization signal by a predetermined shift time. The determination portion determines whether the horizontal synchronization pulses are normal by comparing time differences between input of the horizontal synchronization pulses and input of the reference pulses with the shift time. The extraction portion extracts line image data points from an image signal in synchronization with the input of the horizontal synchronization pulses that have been determined as normal.

Separately providing a shift register for performing serial-to-parallel conversion on a BD signal and a shift register for performing parallel-to-serial conversion on a bit pattern to generate a PWM signal increases the scale of a circuit for adjusting a writing start position in the scanning direction of a light beam. Therefore, the shift register for performing serial-to-parallel conversion on a BD signal and the shift register for performing parallel-to-serial conversion on a bit pattern to generate a PWM signal are configured as a common register.

Separately providing a shift register for performing serial-to-parallel conversion on a BD signal and a shift register for performing parallel-to-serial conversion on a bit pattern to generate a PWM signal increases the scale of a circuit for adjusting a writing start position in the scanning direction of a light beam. Therefore, the shift register for performing serial-to-parallel conversion on a BD signal and the shift register for performing parallel-to-serial conversion on a bit pattern to generate a PWM signal are configured as a common register.

An image forming apparatus including: a drive motor configured to rotate a rotary polygon mirror to deflect light beam; a signal generation unit configured to generate a rotation synchronous signal; and a rotation control unit configured to control a rotation speed of the rotary polygon mirror, wherein the rotation control unit executes a disabling processing of disabling control of the drive motor based on the rotation synchronous signal, wherein a term of a first disabling processing for a first rotation speed is shorter than a term of a second disabling processing for the second rotation speed, and wherein when the rotation speed of the rotary polygon mirror is changed from the first rotation speed to the second rotation speed, the rotation control unit switches the disabling processing from the first disabling processing to the second disabling processing after reduction of the rotation speed of the rotary polygon mirror is started.

An image reading apparatus includes a document placement unit, a document conveyance unit, a reading unit, a case, and a movable member. The document conveyance unit conveys a document, placed on the document placement unit, along a conveyance path. The case accommodates the reading unit and includes a transparent member which allows passing of light to receiving elements, and an opening. The movable member includes a cover portion and a connection portion and moves in an adjustment direction perpendicular to a longitudinal direction of the case. The cover portion covers the case opening while being in contact with an outside of the case. The connection portion connects the reading unit and the cover portion. When the movable member moves in the adjustment direction, the reading unit moves within the case to change an angle of the reading unit with respect to a document conveyance direction.

An image reading apparatus includes a document placement unit, a document conveyance unit, a reading unit, a case, and a movable member. The document conveyance unit conveys a document, placed on the document placement unit, along a conveyance path. The case accommodates the reading unit and includes a transparent member which allows passing of light to receiving elements, and an opening. The movable member includes a cover portion and a connection portion and moves in an adjustment direction perpendicular to a longitudinal direction of the case. The cover portion covers the case opening while being in contact with an outside of the case. The connection portion connects the reading unit and the cover portion. When the movable member moves in the adjustment direction, the reading unit moves within the case to change an angle of the reading unit with respect to a document conveyance direction.

A carriage of an image reading apparatus includes a first lamp and a second lamp. A moving mechanism moves the carriage in a sub-scanning direction from a first side to a second side. The first lamp and the second lamp are arranged in a row in the sub-scanning direction. A control unit turns on any one of the first lamp and the second lamp during reading of one line. The control unit recognizes the position of a first-side edge based on first image data obtained when the first lamp is turned on. The control unit recognizes the position of a second-side edge based on second image data obtained when the second lamp is turned on. The control unit synthesizes the first image data and the second image data to generate job read image data.

A carriage of an image reading apparatus includes a first lamp and a second lamp. A moving mechanism moves the carriage in a sub-scanning direction from a first side to a second side. The first lamp and the second lamp are arranged in a row in the sub-scanning direction. A control unit turns on any one of the first lamp and the second lamp during reading of one line. The control unit recognizes the position of a first-side edge based on first image data obtained when the first lamp is turned on. The control unit recognizes the position of a second-side edge based on second image data obtained when the second lamp is turned on. The control unit synthesizes the first image data and the second image data to generate job read image data.

An image forming apparatus includes: a scanning unit configured to form an electrostatic latent image on a photoconductor by scanning the photoconductor with one or more scanning beams in a main scanning direction based on an image signal, repetitively in a sub-scanning direction perpendicular to the main scanning direction; a generating unit configured to perform halftone processing on image data to generate the image signal; and a storage unit configured to store correction information. The correction information is set such that start positions of a plurality of scanning lines are linearly displaced to either a negative side or a positive side of the main scanning direction along the sub-scanning direction, in accordance with a direction of a first vector forming a smaller angle with the sub-scanning direction among two vectors in the halftone processing.