A position detector includes a reading device, a position reference member having a mark opposite the reading device, and circuitry. The circuitry controls the reading device to detect the contour of the processing target and the position of the image pattern on the processing target and the position of the mark and corrects a processing position for the processing target to offset distortion of the reading device.

A sheet conveying device includable in an image forming apparatus that uses a method of conveying a conveyance target medium and a method of forming an image, includes a position detector, a position adjuster, and circuitry. The position detector is configured to detect a position of a conveyance target medium. Based on a detection of the position of the conveyance target medium by the position detector, the position adjuster moves in at least one of a width direction of the conveyance target medium and a rotation direction of the conveyance target medium within a plane of conveyance of the conveyance target medium and repeatedly adjusts the position of the conveyance target medium while conveying the conveyance target medium. The circuitry changes a conveying speed of the conveyance target medium, according to a change of the position of the conveyance target medium after adjusted by the position adjuster.

A system and method are provided for registering source and target images. The method includes receiving a first source image and a first scanned image. The first scanned image is one that has been generated by scanning a printed page that has been generated by printing the first source image or a transformed first source image derived from the first source image. Locations of corners of a target image in the first scanned image are identified. With a first computed transform, the corners of the target image in the first scanned image are aligned to corners of the first source image to generate an aligned target image. Local features in the source image and aligned target image are detected. A second transform is computed to align the target image with the first source image, based on the detected local features.

A conveyance device includes a conveyance roller, a registration roller, a sensor, a mode setting part, a storage, a conveyance state determination part and a drive control part. The mode setting part sets the mode to either a plain paper mode or a tab paper mode. The storage stores threshold information corresponding to the mode. The conveyance state determination part determines, when the plain paper mode is set, whether the conveyance state of the recording medium is a skew conveyance state or a tab paper conveyance state, based on the detection result of the sensor and the plain paper mode threshold information. The conveyance state determination part determines, when the tab paper mode is set, whether the conveyance state of the recording medium is the skew conveyance state or the tab paper conveyance state, based on the detection result of the sensor and the tab paper mode threshold information.

An image forming apparatus includes an image forming unit, a retransport assembly, and a controller. The retransport assembly includes a first transport roller pair, a second transport roller pair, and a skew roller pair configured to alone transport, in a skewed manner, a sheet spaced from the first transport roller pair and the second transport roller pair, and a reference wall. The controller controls the retransport assembly and executes a waiting operation to cause the sheet to wait at the retransport assembly. The controller is configured to execute the waiting operation by stopping the skew roller pair and one of the first transport roller pair and the second transport roller pair in a state in which the sheet is nipped by the skew roller pair and the one of the first transport roller pair and the second transport roller pair.

Alignment apparatuses include a frame and contact elements connected to the frame. The contact elements contact items that are to be transported in a processing direction relative to the frame. The contact elements are in permeant fixed positions relative to the frame, and do not move relative to the frame. Adjustable mounts are connected to the frame and move the frame in the processing direction and in a perpendicular cross-processing direction. A controller is electrically connected to the adjustable mounts, and the controller is adapted to control the adjustable mounts to simultaneously move the frame and all the contact elements in the cross-processing direction and the processing direction while rotating the frame. Methods laterally shift imaging on sheets that have had rotational correction performed by such alignment apparatuses.

A conveying device includes a first pair of nipping rollers, a second pair of nipping rollers, a position corrector configured to correct a position of a recording medium in a width direction of the recording medium, an end position detector configured to detect an end position of the recording medium in the width direction, and circuitry configured to, in adjustment of the end position detector, stop conveying the recording medium in response to arrival of a leading end of the recording medium at the end position detector, cause the position corrector to move the recording medium toward an outside of the conveyance passage in the width direction to a position at which the end position detector is covered by the recording medium, adjust the output of the end position detector, and cause the end position detector to detect the recording medium.

A sheet conveyance apparatus includes a conveyance roller, an abutment member including an abutment surface against which a side edge, in a width direction, of the sheet abuts, and configured to correct a skew of the sheet, an obliquely conveying roller configured to convey the sheet such as the side edge of the sheet is conveyed toward the abutment surface, a sheet side edge detection portion configured to detect a position of the side edge of the sheet, and a control unit configured to control that a conveyance force, in the width direction, by the obliquely conveying roller in response to a detection result of the sheet side edge detection portion becomes smaller than that in an abutment movement.

A detection device includes a transport passage along which a medium is transported and a detection unit that detects a leading edge portion and a trailing edge portion of the medium in the transport passage while transportation of the medium is stopped and while the medium is pulled in a pulling direction along the transport passage.

In some examples, direct memory access based hardware deskew may include ascertaining scanned data associated with scanning of a physical medium by using a reading direct memory access to step through the scanned data based on a skew angle associated with an orientation of the physical medium relative to a scan bar that is to perform the scanning of the physical medium. Further, direct memory access based hardware deskew may include modifying the scanned data to reduce the skew angle associated with the orientation of the physical medium.