With reference to a correction value revision parameter table, a periodic non-uniformity correction value corresponding to changed rotational speed is obtained from the correction value revision parameter table, and set as a new periodic non-uniformity correction value corresponding to the rotational speed of a rotary component, and thereby a gradation which is an image formation parameter of image data is corrected.

A driving device is used in an image reading apparatus, and reciprocates a scanning unit for reading an image on an original. The driving device comprises a pull member, a driving pulley which transmits driving force to the pull member, a following pulley which applies tension to the pull member and a pulley holder having a pulley axis which holds the following pulley rotatably. Then, the pulley axis has a lock pawl capable of locking an upper end portion of the following pulley and canceling engagement with the following pulley by being tilted toward a side of an axial center by elastic deformation. Furthermore, the lock pawl is arranged at a side of a tension acting direction from the pull member to the following pulley except the farthest position from the driving pulley among positions in a circumferential direction of the pulley axis. It is possible to attach and detach the following pulley easily at a time of maintenance or the like.

A driving device is used in an image reading apparatus, and reciprocates a scanning unit for reading an image on an original. The driving device comprises a pull member, a driving pulley which transmits driving force to the pull member, a following pulley which applies tension to the pull member and a pulley holder having a pulley axis which holds the following pulley rotatably. Then, the pulley axis has a lock pawl capable of locking an upper end portion of the following pulley and canceling engagement with the following pulley by being tilted toward a side of an axial center by elastic deformation. Furthermore, the lock pawl is arranged at a side of a tension acting direction from the pull member to the following pulley except the farthest position from the driving pulley among positions in a circumferential direction of the pulley axis. It is possible to attach and detach the following pulley easily at a time of maintenance or the like.

A plurality of light sources, an optical deflector including a rotational member configured to be rotational about an axis of rotation thereof, and a plurality of reflective members, are provided in a light scanning unit for an image forming apparatus. The optical deflector is arranged to deflect light incident obliquely from the plurality of light sources and the plurality of reflective members are arranged to reflect the light deflected by the optical deflector to a plurality of surfaces, which are to be scanned and correspond to the plurality of light sources, and arranged such that scan lines on opposite surfaces with respect to the axis of rotation of the optical deflector among the plurality of surfaces to be scanned are bent in the same direction.

A plurality of light sources, an optical deflector including a rotational member configured to be rotational about an axis of rotation thereof, and a plurality of reflective members, are provided in a light scanning unit for an image forming apparatus. The optical deflector is arranged to deflect light incident obliquely from the plurality of light sources and the plurality of reflective members are arranged to reflect the light deflected by the optical deflector to a plurality of surfaces, which are to be scanned and correspond to the plurality of light sources, and arranged such that scan lines on opposite surfaces with respect to the axis of rotation of the optical deflector among the plurality of surfaces to be scanned are bent in the same direction.

An image forming apparatus of the present invention acquires first correction characteristics representing an output density for an input gradation value at a reference position in a main scanning direction and second correction characteristics representing a relative relationship of an output density at a predetermined position in the main scanning direction with the output density at the reference position in the main scanning direction. Then, the image forming apparatus corrects image data corresponding to the predetermined position in the main scanning direction based on the first correction characteristics and the second correction characteristics.

An image forming apparatus of the present invention acquires first correction characteristics representing an output density for an input gradation value at a reference position in a main scanning direction and second correction characteristics representing a relative relationship of an output density at a predetermined position in the main scanning direction with the output density at the reference position in the main scanning direction. Then, the image forming apparatus corrects image data corresponding to the predetermined position in the main scanning direction based on the first correction characteristics and the second correction characteristics.

An image forming apparatus includes a light-receiving unit that includes light-receiving elements arranged along a movement direction of a target formed on an image carrier, and is arranged so as to receive light emitted from a light-emitting unit and specularly reflected off the image carrier; a member configured to limit a size, in the movement direction, of diffused reflection light that is incident on the light-receiving unit; a selection unit configured to select whether or not each of the light-receiving elements in the light-receiving unit is an effective light-receiving element; a generation unit configured to generate a detection signal from an output of the effective light-receiving element; and a detection unit configured to detect a target formed on the image carrier based on the detection signal.

An image forming apparatus includes a rotating body to form an image, a sensor to detect a home position of the rotating body, a processor to acquire image density data of the image formed by the rotating body in odd-numbered rotation and even-numbered rotation of the rotating body separately based on a rotation home position signal output by the sensor, extract an image density fluctuation caused by a rotation of the rotating body, and correct an image forming condition based on the image density fluctuation.

In an image forming apparatus that employs a laser scanning optical system that does not use an f lens, in the case where magnification correction by insertion/removal of an auxiliary pixel is performed based on the premise of digital PWM, an insertion/removal position of an auxiliary pixel is controlled in accordance with a purpose of each piece of image processing.