A color measurement apparatus comprising: a color measurement unit configured to perform color measurement of an image on a sheet, the color measurement unit including a light source; a reference member used for calibration of the color measurement unit; a moving unit configured to move the color measurement unit to a first position at which the light source irradiates a region other than the reference member with light and a second position at which the light source irradiates the reference member with light; and a control unit configured to, after causing the light source to emit light when the color measurement unit is positioned at the first position, and then moving the color measurement unit to the second position, execute the calibration based on data obtained by causing the light source to irradiate the reference member with light.

An image processing circuit board, a reading device, an image forming apparatus, an image processing method, and an image processing device. The image processing circuit board subtracts output of an image sensor when no input light is received, from output of a reading device that reads image data of a subject using the image sensor, discriminates between effective area and invalid area of the image data output by the reading device, and converts the image data of the invalid area into a predetermined output value after the output of the image sensor when no input light is received is subtracted from the output of the reading device.

An information processing apparatus includes processing circuitry. The processing circuitry detects an abnormality in an image reading apparatus from a first spectral reflectance and a second spectral reflectance, the first spectral reflectance being generated based on data read from a reference white plate installed in the image reading apparatus, the second spectral reflectance being generated before generation of the first spectral reflectance, and identifies a cause of an abnormality in the image reading apparatus in a case where the processing circuitry detects the abnormality.

An image forming apparatus includes a printer, a first reader, a second reader, and a processor. The printer is configured to print an image having diagnostic information on a sheet of paper. The first reader is configured to read a first image from the sheet of paper. The second reader is configured to read a second image from the sheet of paper. The processor is configured to cause a display to display a diagnosis result of a defect based on the first image and the second image.

An image reading device includes a background unit, a reading unit, and circuitry. The background unit is configured to be a background in reading of a recording medium and includes a first region that is black and a second region that is different from the first region. The reading unit is configured to read an image with the background unit as the background, and generate a read value based on a result of reading the image with the background unit. The circuitry is configured to correct the read value based on a reference value generated by the reading unit by reading the second region of the background unit.

In the image processing apparatus according to the present disclosure, a data processing unit derives a density variation component for at least one modulation period from a difference between a reference plate reading value when the illumination is turned off, a reference plate reading value when the illumination is turned on, and black reference data and white reference data in synchronization with modulation of the SS clock, and corrects the image data with the density variation component. The white reference data indicates the light distribution of the illumination in the main scanning direction, and the data processing unit corrects the density variation component on the basis of the difference between the white reference data and the black reference data, and corrects the image data with the corrected density variation component.

An image reading device and an image forming apparatus. The image reading device includes an image reader to read an image of a document, and a color reference component arranged to face the image reader. In the image reading device, the image reader reads the color reference component at a prescribed timing to obtain color reference image data, and correction data generating processes are executed based on the obtained color reference image data to generate correction data used to correct data of the image read by the image reader. In the image reading device, wherein the color reference component is moved relative to the image reader in a direction orthogonal to a direction toward and away from the image reader. The image forming apparatus includes the image reading device, and an image is formed on a recording material based on data of the image read by the image reading device.

In the image processing apparatus according to the present disclosure, a data processing unit derives a density variation component for at least one modulation period from a difference between a reference plate reading value when the illumination is turned off, a reference plate reading value when the illumination is turned on, and black reference data and white reference data in synchronization with modulation of the SS clock, and corrects the image data with the density variation component. The white reference data indicates the light distribution of the illumination in the main scanning direction, and the data processing unit corrects the density variation component on the basis of the difference between the white reference data and the black reference data, and corrects the image data with the corrected density variation component.

An image processing circuit board, a reading device, an image forming apparatus, an image processing method, and an image processing device. The image processing circuit board subtracts output of an image sensor when no input light is received, from output of a reading device that reads image data of a subject using the image sensor, discriminates between effective area and invalid area of the image data output by the reading device, and converts the image data of the invalid area into a predetermined output value after the output of the image sensor when no input light is received is subtracted from the output of the reading device.

An image reading apparatus includes a stacking unit, a conveyance unit to convey stacked sheets, a reading unit, a white reference plate provided in a second position, and a processor. The reading unit is movable and, at a first position, reads a conveyed sheet image to obtain image data and, at the second position, reads the white reference plate. The processor generates, based on a plate reading result, a shading correction value and corrects the image data using the shading correction value. Based on whether the number of times in which reading the white reference plate has been performed is less than a predetermined number of times, the reading unit changes a time interval in a reading period that is from a first timing to a second timing. The processor generates, each time the white reference plate is read, the shading correction value based on the plate reading results.