A pixel clock generating device includes a high-frequency clock generator, a comparer, a pixel clock generator, and a value switcher. The high-frequency clock generator is configured to generate a high-frequency clock. The comparer is configured to measure a time interval between a leading-end synchronizing signal and a trailing-end synchronizing signal in a main scanning and calculate an error between the time interval and a target value. The pixel clock generator is configured to generate a pixel clock based on the high-frequency clock and a pixel clock frequency and correct the pixel clock based on the error. The value switcher, including a plurality of groups of values with which the pixel clock is generated, is configured to switch between the plurality of groups of values according to a switching signal after the trailing-end synchronizing signal is inputted, the comparer calculates the error, and the pixel clock generator corrects the pixel clock.

An image forming apparatus includes an image forming device and circuitry. The image forming device forms an image. The circuitry corrects an amount of deviation based on a pattern formed by the image forming device, changes a magnification of the pattern, and calculates the amount of deviation based on the magnification.

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 in which 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 in which 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 mode.

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 masking processing of masking control of the drive motor based on the rotation synchronous signal, wherein a time period of a first masking processing for a first rotation speed is shorter than a time period of a second masking 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 masking processing from the first masking processing to the second masking processing after reduction of the rotation speed of the rotary polygon mirror is started.

An image forming apparatus includes: a specification unit configured to perform surface specification processing for specifying a reflective surface that deflects light; a correction unit configured to perform correction processing for correcting image data in accordance with which reflective surface deflects light; and a control unit configured to control so as to cause scanning of a first photosensitive member to start before the surface specification processing completes, and control so as to, after the surface specification processing completes, cause the correction processing to be performed, with respect to image data for causing light to be emitted from a second light source and in accordance with a specification result of the surface specification processing, and cause scanning of the second photosensitive member to start.

An image forming apparatus which is capable of reducing a load on a data bus therein when controlling an image reading apparatus depending on its image processing capability. When acquired identification information about the image forming apparatus is included in a clock control table 600, a clock frequency for controlling hardware of the image reading apparatus in accordance with the clock control table 600, while setting the clock frequency therefor to a default setting of the clock control table 600 when the acquired identification information is not included in the clock control table 600, wherein a minimum value of clock frequencies in the clock control table 600 is set as the default setting of the clock control table 600.

A device detects at least one position of at least a part of a printing material while the printing material is transported in a printing machine. The device includes an optical sensor for establishing a distance between a printing machine component and the printing material. The distance established by the optical sensor is temperature-compensated by a computer.

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 forming apparatus includes image forming devices, image output devices, an endless conveyor, a transfer device, holders, a detector, and circuitry. The image forming devices include image bearers. The image output devices form latent images on the image bearers. The image forming devices form visible images from the latent images. The transfer device transfers the visible images onto the endless conveyor that conveys the visible images in an image conveyance direction. The holders hold the image forming devices interchangeable at holding positions aligned in the image conveyance direction. The detector detects the visible images. The circuitry compares a first visible image of the visible images formed at a specific holding position of the holding positions with a second visible image of the visible images formed at another holding position of the holding positions on the endless conveyor, to correct misalignment between the first and second visible images.

An image forming apparatus, including: a light source; a photosensitive member rotatable in a first direction; a deflecting unit configured to deflect the light beam in a second direction orthogonal to the first direction; a conversion unit configured to convert image data into a plurality of bit data corresponding to a density on a pixel-by-pixel basis; a specifying unit configured to specify a pixel size that is a number of divided pixels forming a pixel according to a position of the pixel in the second direction; and a correction unit configured to correct the plurality of bit data according to the pixel size, wherein the specifying unit specifies pixel sizes of pixels after an arrangement of the pixels in the second direction is replaced for each pixel group, the pixel group being obtained by dividing, with respect to each predetermined number of pixels, pixels arranged in the second direction.