An image reading device includes: a reading unit; a first detecting unit that detects a position of the reading unit in the sub-scanning direction; a second detecting unit that detects a position of the reading unit in the sub-scanning direction; and a calculating unit that calculates a skew quantity and a skew direction of the reading unit, based on a difference, introduced by the skew, between a travel distance by which the reading unit has travelled from a measurement reference position located on an upstream side of the first detecting unit and the second detecting unit in a moving direction to a point where the reading unit is detected by the first detecting unit, and a travel distance by which the reading unit has travelled from the measurement reference position to a point where the reading unit is detected by the second detecting unit.

Disclosed is a method of determining line feed error in an image forming apparatus for printing an image, said image forming apparatus comprising a print head having a head sensor configured to sense information from the image printed on a print medium, said method comprising the steps of printing a first swath of the image on the print medium, repositioning the print head relative to the print medium by at least one line feed distance, determining a line feed error based upon information sensed from the printed first swath by the head sensor, and printing, using the determined line feed error, a second swath of the halftone image on the print medium.

Example implementations relate to streak compensation. Some examples may calibrate an initial gain for data from an optical element based on a scan of a first calibration target, obtain an image of a second calibration target from the optical element using the calibrated initial gain, and detect at least one streak in the image of the second calibration target. Some examples may also record data representing the at least one detected streak and may calibrate a final gain for the optical element based on the initial gain and the data representing the at least one detected streak.

An image reader including a document table having a reference point, a first region of a sheet having a predetermined size when a vertex of the sheet is positioned on the reference point, and a second region, a changing mechanism changing a reading position in a sub scanning direction, and a controller configured to control the changing mechanism to change the reading position to a first position such that a distance in the sub scanning direction between the reference point and the first position corresponds to a length of the predetermined sheet size in the sub scanning direction, acquire specific digital data of the second region through image reading in the first position with a light source turned off, compare a particular value of the specific digital data with a criterion value within the second region, and determine a state of a document cover based on the comparison.

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.

An optical scanning device includes a light source that emits light, a deflector that deflects and scans the light emitted from the light source in a main scanning direction, a housing, a synchronization detection sensor, and a sensor board. The synchronization detection sensor is mounted in the housing, detects scanning light from the deflector, and outputs a write timing reference signal of image data. The sensor board is mounted with the synchronization detection sensor. The aforementioned sensor board is formed with a light transmitting hole for allowing a part of the scanning light to pass therethrough when an incident position of the scanning light for a light receiving surface coincides with a center position of the aforementioned light receiving surface in a sub-scanning direction on an extension line of a center line of the light receiving surface of the aforementioned synchronization detection sensor in the sub-scanning direction.

An image processing apparatus includes a support member to support a sheet, a light source that extends in a main-scanning direction and is configured to move in a sub-scanning direction and irradiate light on the sheet as the light source moves in the sub-scanning direction, a conversion unit configured to generate multiple line image data based on light reflected by the sheet and incident thereon, as the light source moves in the sub-scanning direction, and a processing unit configured to carry out a correction process with respect to each of the line image data using a different correction formula for each of the line image data.

An image reading apparatus includes a reading unit for reading an image formed on a sheet, a reference member for performing shading correction, and a moving mechanism including a drive source, a cam to be rotated by the drive source, and a moving member that abuts against the cam, wherein, with a conveying direction of the sheet being a first direction, a width direction of the sheet intersecting the first direction being a second direction, and a direction intersecting the first direction and the second direction being a third direction, the moving mechanism is configured to be operable to move the reading unit to a first position and a second position that is different from the first position in position in the third direction.

An image reader including a document table having a reference point, a first region of a sheet having a predetermined size when a vertex of the sheet is positioned on the reference point, and a second region, a changing mechanism changing a reading position in a sub scanning direction, and a controller configured to control the changing mechanism to change the reading position to a first position such that a distance in the sub scanning direction between the reference point and the first position corresponds to a length of the predetermined sheet size in the sub scanning direction, acquire specific digital data of the second region through image reading in the first position with a light source turned off, compare a particular value of the specific digital data with a criterion value within the second region, and determine a state of a document cover based on the comparison.

An image processing apparatus includes a support member to support a sheet, a light source that extends in a main-scanning direction and is configured to move in a sub-scanning direction and irradiate light on the sheet as the light source moves in the sub-scanning direction, a conversion unit configured to generate multiple line image data based on light reflected by the sheet and incident thereon, as the light source moves in the sub-scanning direction, and a processing unit configured to carry out a correction process with respect to each of the line image data using a different correction formula for each of the line image data.