Planar light source and image reading device

An image reading device, comprising:

• a document table for supporting an original document;
• a planar light-emitting device having a plate-like shape that emits light from one surface toward the document table;
• a light-emitting device drive circuit that drives the planar light-emitting device;
• a support unit that supports the planar light-emitting device;
• a photoelectric conversion device that converts an image of an original document into an electrical image signal;
• a shading correction device that performs shading correction on the image signal, the shading correction including electrical correction of the image signal;
• a document placement frame on the document table corresponding to a region of the planar light-emitting device that emits a quantity of light sufficient for shading correction by the shading correction device;
• and
• a hinge unit connecting the support unit and the document table to allow pivotal movement of the support unit relative to the document table such that the support unit assumes an open position and a closed position relative to the document table,
• wherein the light-emitting device drive circuit is positioned on the support unit between the planar light-emitting device and the hinge unit.

A method of reading an original document, comprising:

• transmitting light from a planar light emitting device to an original document placement frame;
• illuminating the original document placement frame so that luminosity of the planar light-emitting device is constant in at least one direction;
• moving a photoelectric conversion device over the illuminated original document placement frame in the at least one direction;
• converting an image of the original document in the original document placement frame to electrical signals;
• determining shading correction measurements for the electrical signals for each point in a direction substantially perpendicular to the at least one direction;
• and
• performing shading correction on the electrical image signal, wherein the step of transmitting planar light to the original document placement frame comprises the steps of receiving sufficient light within the original document placement frame for the shading correction and of locating the original document placement frame to correspond to 60% maximum luminosity of the planar light-emitting device.

An image reading device, comprising:

• a document table for supporting an original document;
• planar light-emitting means having a plate-like shape for emitting light from one surface toward the document table;
• photoelectric conversion means for converting an image of an original document into an electrical image signal;
• shading correction means for performing shading correction on the image signal, the shading correction including electrical correction of the image signal;
• and
• a document placement frame on the document table corresponding to a region of the planar light-emitting means that emits a quantity of light sufficient for shading correction by the shading correction means, wherein the document placement frame delineates 60% of maximum luminosity of the planar light-emitting means.