A document reading device includes an imaging unit that images a document, a placing portion that includes a first placing portion and a second placing portion and that has a placing surface on which the document is placed, the placing surface being formed by the first placing portion and the second placing portion, and a detector that detects an edge of the document that is placed on the placing surface by using a color difference or a luminance difference between the placing surface and the document. An end portion of the first placing portion adjacent to the second placing portion extends toward the second placing portion beyond an end portion of the second placing portion adjacent to the first placing portion.

An image processing apparatus includes a medium discharge portion onto which a medium to be taken out by a person with the person standing is discharged, a placement portion that is installed above the medium discharge portion, an object in color that is represented by using a Y-value closer than a value that represents black color to a value that represents white color where the color is represented by using a Y-value that represents luminance in a YCbCr method being placed on the placement portion, an image capturing member that is installed above the placement portion and that captures an image of the object that is placed on the placement portion. Color of an upper portion of the placement portion is represented by using a Y-value closer than the value that represents the white color to the value that represents the black color where the color is represented by using the Y-value that represents the luminance in the YCbCr method such that the object and the placement portion are distinguishable from each other in the image that is captured by the image capturing member.

A position detection device includes a background member, a reader, and processing circuitry. The background member has a higher absorption characteristic in an invisible wavelength region than in a visible wavelength region. The reader opposite the background member irradiates a recording medium having a mark and the background member with light of a visible wavelength to output a visible image or with light of an invisible wavelength to output an invisible image. The processing circuitry is configured to: detect an end position of the recording medium and a position of the mark on the recording medium from a read image output from the reader; and select the visible or invisible image as the read image used for position detection, according to an absorption characteristic of a color material forming the mark read by the reader and an absorption characteristic of the recording medium in the invisible wavelength region.

A multi-mode scanning device includes a background element, a transparent platen, first and second light sources and an optical module. The first light source outputs visible light to irradiate the background element and an original on the transparent platen to generate first and second light, respectively. The second light source outputs invisible light to irradiate a combination of the background element and the original to generate third and fourth light. The movable optical module receives the first to fourth light and generates sensing signals, and obtains visible light information and invisible light information representative of the original according to the sensing signals. The original is disposed between the background element and the optical module. The first light source and the optical module are disposed on a same side of the background element. The optical module and the second light source are disposed on different sides of the background element.

A reading device includes an illuminator, an imaging device, a memory, and a detector. The illuminator illuminates an object to be read with light in an invisible wavelength range. The imaging device captures an image of the light reflected from the object to be read, within the invisible wavelength range. The memory holds a reference value of the object to be read. The detector detects a state of the object to be read, based on a difference between a level of a reading value of an invisible image captured within the invisible wavelength range and a level of the reference value.

A position detection device includes a background member, a reader, and processing circuitry. The background member has a higher absorption characteristic in an invisible wavelength region than in a visible wavelength region. The reader opposite the background member irradiates a recording medium having a mark and the background member with light of a visible wavelength to output a visible image or with light of an invisible wavelength to output an invisible image. The processing circuitry is configured to: detect an end position of the recording medium and a position of the mark on the recording medium from a read image output from the reader; and select the visible or invisible image as the read image used for position detection, according to an absorption characteristic of a color material forming the mark read by the reader and an absorption characteristic of the recording medium in the invisible wavelength region.

A placement detection system includes: a placement table; an imaging device that images an object placed on the placement table to generate an input image; and a control device. The control device generates a first binarized image for the input image based on a first threshold value and determines whether the object is placed in a predetermined placement orientation. The control device changes a threshold value for a target pixel to a second threshold value higher than the first threshold value when the object is determined to be placed in the predetermined placement orientation, the target pixel being sandwiched between pixels having pixel levels lower than or equal to the first threshold value and has a higher pixel level than the first threshold value in a first region, generates a second binarized image for the target pixel based on the second threshold value, and detects a shape of the object.

A multi-mode scanning device includes a background element, a transparent platen, first and second light sources and an optical module. The first light source outputs visible light to irradiate the background element and an original on the transparent platen to generate first and second light, respectively. The second light source outputs invisible light to irradiate a combination of the background element and the original to generate third and fourth light. The movable optical module receives the first to fourth light and generates sensing signals, and obtains visible light information and invisible light information representative of the original according to the sensing signals. The original is disposed between the background element and the optical module. The first light source and the optical module are disposed on a same side of the background element. The optical module and the second light source are disposed on different sides of the background element.

A reading device includes an illuminator, an imaging device, a memory, and a detector. The illuminator illuminates an object to be read with light in an invisible wavelength range. The imaging device captures an image of the light reflected from the object to be read, within the invisible wavelength range. The memory holds a reference value of the object to be read. The detector detects a state of the object to be read, based on a difference between a level of a reading value of an invisible image captured within the invisible wavelength range and a level of the reference value.

A placement detection system includes: a placement table; an imaging device that images an object placed on the placement table through the placement table to generate an input image; and a control device that receives the input image. The control device identifies a higher-level pixel having a pixel level higher than or equal to a predetermined pixel level in the input image, sets a threshold value of the higher-level pixel, and sets a threshold value of a target pixel other than the higher-level pixel to a lower value than the threshold value of the higher-level pixel in accordance with a distance between the higher-level pixel and the target pixel. The control device binarizes a pixel level of the target pixel in accordance with the threshold value of the target pixel to produce a binarized image and detects a shape of the object by using the binarized image.