Patent ID: 8717636
Filing Date: 2014-05-06
Classification: H04N

Abstract:
1. An image reading device, comprising: a document feed unit configured to cause a document to move along a document delivery path; a light source unit including a plurality of light sources configured to generate light and a separate light guide associated with each light source, the light source unit being movable between a first position and a second position, the second position being adjacent to at least a portion of the document delivery path, the light source unit being further configured to illuminate a first criterion member at the first position, and to illuminate the document received from the document feed unit at the second position; a second criterion member arranged to face the light source unit when the light source unit is located at the second position, the second criterion member having a length that is sufficient to substantially cover a range of a light illumination by the light source unit at the second position; an image acquisition unit configured to acquire criterion shading data, auxiliary shading data and image data, the criterion shading data corresponding to a first reflection of the light illumination by the light source unit off the first criterion member, the auxiliary shading data corresponding to a second reflection of the light illumination by the light source unit off the second criterion member, the image data corresponding to a third reflection of the light illumination by the light source off the document; and a control unit configured to compensate the image data according to the criterion shading data, and to update the criterion shading data with the auxiliary shading data; wherein the light source unit comprises a light guide holder that comprises a separate recess to receive the light guides, such that each recess receives one of the light guides; wherein the document comprises a plurality of documents delivered sequentially by the document feed unit, the control unit being configured to update the criterion shading data between passing of each of the plurality of documents by the second position; wherein the control unit is configured to control the light source unit and the image acquisition unit so as to acquire the auxiliary shading data prior to an arrival of any of the plurality of documents at the second position and at a time after a first of two consecutive ones of the plurality of documents has passed by the second position and before a second of the two consecutive ones of the plurality of documents arrives at the second position; wherein the control unit is configured to update the criterion shading data according to a relationship defined by: wherein Ru is the criterion shading data that has been updated, R being the criterion shading data acquired that correspond to the first reflection of the light illumination by the light source unit off the first criterion member, SRn being the auxiliary shading data acquired between passing of n-1