An image scanner includes a controller configured to perform black data acquiring process for each color that includes, in a particular period of time, while controlling a light source to be turned off, controlling each of a plurality of light receiving elements to read an image of an object and transmit read data of the object to a shift register, and in a specific period of time next to the particular period of time, controlling the light source to emit light of a color different from the particular color, and controlling the shift register to output a plurality of pieces of image data of the object as a plurality of pieces of black data for the particular color, the plurality of pieces of image data corresponding to the plurality of pieces of read data of the object transmitted by the plurality of light receiving elements, respectively.

An image reading apparatus according to the present disclosure includes a platen glass, an image reader, and an output interface. An original is placed on the platen glass. The image reader is configured to read an image of the original on the platen glass. The image reader includes at least one sensor configured to detect a quantity of light for each of a plurality of regions on the platen glass. The output interface is configured to output information which identifies one or more regions of the plurality of regions in which the quantity of light detected therefrom exceeds a given value.

A signal processing device includes a signal output circuit, a controller, and a corrector. The signal output circuit outputs a signal according to a physical quantity being input. The controller controls the signal output circuit. The corrector corrects a signal to be corrected. The signal to be corrected is output from the signal output circuit. The signal output circuit selectively performs one of first operation of outputting a characteristic signal that indicates characteristics of the signal output circuit and second operation of outputting a pseudo signal that is generated spuriously, according to control of the controller. The corrector corrects the signal to be corrected based on one of the characteristic signal and the pseudo signal output from the signal output circuit.

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.

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 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.

An image scanning apparatus, comprising: a scanning device; a reference member; a correction unit; a controller; and a storage device, the scanning device comprising light receiving elements and a lens array, wherein the controller executes: a preparation process and an executive process, the preparation process comprising: a white reference data obtaining process to obtain white reference data by scanning a white reference original; and a white storing process to obtain white basic data by averaging the white reference data of a particular number of adjoining light receiving elements, wherein the executive process comprises: a reference member data obtaining process to obtain reference member data by scanning the reference member; a lens fluctuation calculation process to calculate fluctuation data of the correction data based on the reference member data; and a correction data generation process to generate the correction data by adding the fluctuation data to the white basic data.

A document reading device includes: a conveying unit configured to convey a document; a background member having a mark for correcting an inclination of the document; a color reading unit configured to read an image of the document and to output color image data; a monochrome reading unit configured to read the image of the document and to output monochrome image data; a switching unit configured to switch between a first state and a second state; and a hardware processor configured to switch into the first state at the time of a color mode, and to switch into the second state at the time of the monochrome mode, configured to detect the inclination of the document, and configured to correct the inclination of the color image data, and to correct the inclination of the monochrome image data, in accordance with the detected inclination of the document.

A shading correction device includes first and second extractors, an intersection calculator, a phase shift amount calculator, a phase shifter, a generator, and a corrector. The first extractor extracts a first periodic component of original shading data. The second extractor extracts a second periodic component of a second reading result. The intersection calculator calculates a first intersection of the first component and a reference level and a second intersection of the second component and the reference level. The phase shift amount calculator calculates a phase shift amount at each of plural positions with a difference between the first and second intersections. The phase shifter shifts a phase of the first component with the phase shift amount. The generator generates corrected shading data including the phase-shifted first component and the original shading data with the first component smoothed. The corrector performs shading correction based on the corrected shading data.

A shading correction device includes first and second extractors, an intersection calculator, a phase shift amount calculator, a phase shifter, a generator, and a corrector. The first extractor extracts a first periodic component of original shading data. The second extractor extracts a second periodic component of a second reading result. The intersection calculator calculates a first intersection of the first component and a reference level and a second intersection of the second component and the reference level. The phase shift amount calculator calculates a phase shift amount at each of plural positions with a difference between the first and second intersections. The phase shifter shifts a phase of the first component with the phase shift amount. The generator generates corrected shading data including the phase-shifted first component and the original shading data with the first component smoothed. The corrector performs shading correction based on the corrected shading data.