An image scanner includes a transparent plate, a scanning device, a driving device, a positioning member, a light absorbing portion and a white reference portion. The transparent plate has an original placing surface. The scanning device irradiates an original with light by means of a light source and scans reflected light from the original. The driving device reciprocates the scanning device along the transparent plate. The positioning member positions the original placed on the original placing surface of the transparent plate. The light absorbing portion, which is disposed on the original placing surface side of the positioning member and at substantially a central portion of the positioning member in moving directions of the scanning device, absorbs ambient light entering to the original placing surface side of the positioning member through the transparent plate. The white reference portion is provided to the original placing surface side of the positioning member.

An image scanner includes a transparent plate, a scanning device, a driving device, a positioning member, a light absorbing portion and a white reference portion. The transparent plate has an original placing surface. The scanning device irradiates an original with light by means of a light source and scans reflected light from the original. The driving device reciprocates the scanning device along the transparent plate. The positioning member positions the original placed on the original placing surface of the transparent plate. The light absorbing portion, which is disposed on the original placing surface side of the positioning member and at substantially a central portion of the positioning member in moving directions of the scanning device, absorbs ambient light entering to the original placing surface side of the positioning member through the transparent plate. The white reference portion is provided to the original placing surface side of the positioning member.

An image reading apparatus for bound media includes a placement table, on which a bound medium is placed, a first arm that is opposite to a bound portion of the bound medium, a second arm, a lifting unit that lifts up a turned medium of the bound medium, a second arm moving mechanism that moves the second arm, so that the turned medium lifted by the lifting unit is sandwiched between the first arm and the second arm, an arm moving mechanism that moves the first arm and the second arm, so that the turned medium turns over, a first imaging unit that performs imaging of a side of the turned medium opposite to the first arm, and a second imaging unit that performs imaging of the a side of the turned medium opposite to the second arm.

An image reading device includes a first unit to read one surface of a document in a first area facing a document path, a second unit disposed in the first area to read the other surface of the document, a first reference member facing the first unit at a first distance therefrom at a second position in a second area not facing the path, a second reference member facing the first unit at a second distance therefrom at a first position in the first area, a third reference member facing the second unit at the second distance therefrom, and a correction unit to correct, based on a difference between first data generated through reading of the first member by the first unit and second data generated through reading of the second member by the first unit, third data generated through reading of the third member by the second unit.

An image scanner includes a transparent plate, a scanning device, a driving device, a positioning member, a light absorbing portion and a white reference portion. The transparent plate has an original placing surface. The scanning device irradiates an original with light by means of a light source and scans reflected light from the original. The driving device reciprocates the scanning device along the transparent plate. The positioning member positions the original placed on the original placing surface of the transparent plate. The light absorbing portion, which is disposed on the original placing surface side of the positioning member and at substantially a central portion of the positioning member in moving directions of the scanning device, absorbs ambient light entering to the original placing surface side of the positioning member through the transparent plate. The white reference portion is provided to the original placing surface side of the positioning member.

A reading device includes a light source configured to emit a first light band and a second light band towards a reading target object, the first and second light bands being different; an imager including multiple photoelectric conversion elements, each photoelectric conversion element configured to be sensitive to one of multiple light reception wavelengths; and circuitry. The imager receives light having the multiple light reception wavelengths reflected from the reading target object; outputs a first color read value of the reading target object with a first color having a first light reception wavelength of the multiple light reception wavelengths; and outputs a second color read value of the reading target object with a second color having a second light reception wavelength of the multiple light reception wavelengths. The circuitry corrects the first color read value based on the second color read value and output the corrected first color read value.

A rod lens array 10a includes a plurality of gradient-index rod lenses 1b arrayed to have optical axes parallel to each other, and forms an erecting equal-magnification image. The gradient-index rod lenses 1b each have a refractive-index distribution in a radial direction thereof. The refractive-index distribution n(r) is approximated by n(r)=n.sub.0.Math.{1(A/2).Math.r.sup.2}, where a refractive index at a center of the gradient-index rod lens 1b is represented by n.sub.0, a refractive-index distribution constant of the gradient-index rod lens 1b is represented by A, and a distance from the center of the gradient-index rod lens 1b is represented by r. The gradient-index rod lens 1b has an aperture angle of 3 to 6, the aperture angle represented by =sin.sup.1(n.sub.0A.Math.r.sub.0), where a radius of the gradient-index rod lens is represented by r.sub.0. The rod lens array 10a has an imaging distance of 45 to 75 mm and a depth of field of 1.5 to 3.0 mm with value of modulation transfer function (MTF) of 30% or more at a spatial frequency of 6 lp/mm.

A rod lens array 10a includes a plurality of gradient-index rod lenses 1b arrayed to have optical axes parallel to each other, and forms an erecting equal-magnification image. The gradient-index rod lenses 1b each have a refractive-index distribution in a radial direction thereof. The refractive-index distribution n(r) is approximated by n(r)=n.sub.0.Math.{1(A/2).Math.r.sup.2}, where a refractive index at a center of the gradient-index rod lens 1b is represented by n.sub.0, a refractive-index distribution constant of the gradient-index rod lens 1b is represented by A, and a distance from the center of the gradient-index rod lens 1b is represented by r. The gradient-index rod lens 1b has an aperture angle of 3 to 6, the aperture angle represented by =sin.sup.1(n.sub.0.Math.A.Math.r.sub.0), where a radius of the gradient-index rod lens is represented by r.sub.0. The rod lens array 10a has an imaging distance of 45 to 75 mm and a depth of field of 1.5 to 3.0 mm with value of modulation transfer function (MTF) of 30% or more at a spatial frequency of 6 lp/mm.