IMAGE SCANNING APPARATUS

摘要

An image scanning apparatus is configured to obtain a greatest gray gradation value when the light source illuminates the gray reference member at a first light quantity value, set a second light quantity value such that a gray signal having the gray gradation value is output by the signal conversion unit based on the analog signal output by the photoelectric conversion element belonging to a block identified by the block information when the light source illuminates the gray reference member at the second light quantity value, calculate a shading correction value, scan the image on the original sheet with controlling the light source to illuminate the original sheet in accordance with the second light quantity value, and apply the shading correction to the digital signal output by the signal conversion unit in accordance with the shading correction value.

主权项

1. An image scanning apparatus, comprising:
a gray reference member arranged in a conveying path in which an original sheet is to be conveyed, the gray reference member having a reflection coefficient smaller than that of a white color; a scanning unit configured to scan an image on the original sheet on a line basis, the scanning unit including a light source configured to illuminate the original sheet when passing the gray reference member and a plurality of photoelectric conversion elements aligned in a scanning direction which is a transverse direction of the conveying path and divided into a plurality of blocks; a signal conversion unit configured to convert an analog signal from each of the plurality of photoelectric conversion elements to a digital signal; and a controller, the controller is configured to:
obtain a greatest gray gradation value among a plurality of gradation values of gray signals output by the signal conversion unit when the light source illuminates the gray reference member at a first light quantity value, the first light quantity value being set so that white signals would be output by the signal conversion unit if the light source would illuminate a white reference member at the first light quantity, and block information identifying a block to which the photoelectric conversion element that output the analog signal corresponding to the gray signal of the greatest gray gradation value before the scanning unit scans the image on the original sheet;set a second light quantity value such that a gray signal having the gray gradation value is output by the signal conversion unit based on the analog signal output by the photoelectric conversion element belonging to the block identified by the block information when the light source illuminates the gray reference member at the second light quantity value;calculate a shading correction value;control the scanning unit to scan the image on the original sheet with controlling the light source to illuminate the original sheet in accordance with the second light quantity value; andapply the shading correction to the digital signal output by the signal conversion unit in accordance with the shading correction value.