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.

According to aspects of the embodiments, there is provided process and architecture for enabling multiple digital micromirror devices (DMDs) that include optical modulation elements configured to modulate light outputting from a light source, and a projection unit configured to project light modulated by the optical modulation elements on a printing plate. Image defects due to misalignment in the cross-process direction of the output from the DMDs are discovered by using a single test pattern image and combined with knowledge of how individual pixels are rendered to register printing elements which can render a variable number of pixels. Misalignment errors can be corrected by selecting a different set of mirrors for a given DMD.

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.