| 摘要 |
An image reading apparatus includes a gray reference member, a reading unit, an adjusting unit, a calibration unit, a storage unit, and a control unit. The control unit is configured to execute a first preprocessing and a second preprocessing. The first preprocessing includes: acquiring first black data from one line worth of image data; acquiring white data; calculating white-black difference data; acquiring first light gray data; and calculating first light gray-black difference data. The second processing includes: acquiring second black data from the one line worth of the image data; acquiring second light gray data; calculating second light gray-black difference data; calculating a change ratio by dividing the second light gray-black difference data by the first light gray-black difference data; and calculating calibration data by multiplying the white-black difference data by the change ratio. Shading of the image data is calibrated in response to the calibration data. |
| 主权项 |
1. An image reading apparatus comprising:
a gray reference member colored in gray having a reflection ratio lower than that of white; a reading unit configured to irradiate light onto an original document or the gray reference member to read images thereon on a line-to-line basis and produce image data; an adjusting unit configured to apply an adjustment value to the reading unit, the reading unit adjusting a light amount to be irradiated onto the original document and the gray reference member in a range from zero to maximum in accordance with the adjustment value; a calibration unit configured to calibrate shading of the image; a storage unit; and a control unit configured to execute a first preprocessing and a second preprocessing, the second preprocessing being executed after execution of the first preprocessing, the first preprocessing executed by the control unit including:
(a) reading with the reading unit the original document and the gray reference member without irradiating the light thereonto and producing one line worth of the image data relating to pixels arranged in one line;(b) acquiring first black data from the one line worth of the image data produced in (a);(c) reading with the reading unit a white color document upon irradiating the light having a light amount adjusted by a first adjustment value and producing one line worth of the image data relating to pixels arranged in one line;(d) acquiring white data from the one line worth of the image data produced in (c);(e) calculating, on a pixel-to-pixel basis, white-black difference data by subtracting the first black data from the white data and storing the white-black difference data in the storage unit;(f) reading with the reading unit the gray reference member upon irradiating the light having the maximum light amount and producing one line worth of the image data relating to pixels arranged in one line;(g) acquiring first light gray data from the pixels in the one line worth of the image data produced in (f); and(h) calculating, on a pixel-to-pixel basis, first light gray-black difference data by subtracting the first black data from the first light gray data and storing the first light gray-black difference data in the storage unit; and the second preprocessing executed by the control unit including:
(i) reading with the reading unit the original document and the gray reference member without irradiating the light thereonto and producing one line worth of the image data relating to pixels arranged in one line;(j) acquiring second black data from the one line worth of the image data produced in (i);(k) reading with the reading unit the gray reference member upon irradiating the light having the maximum amount and producing one line worth of the image data relating to pixels arranged in one line;(l) acquiring second light gray data from the one line worth of image data produced in (k);(m) calculating, on a pixel-to-pixel basis, second light gray-black difference data by subtracting the second black data from the second light gray data and storing the second light gray-black difference data in the storage unit;(n) calculating, on a pixel-to-pixel basis, a change ratio by dividing the second light gray-black difference data by the first light gray-black difference data; and(o) calculating, on a pixel-to-pixel basis, calibration data by multiplying the white-black difference data by the change ratio, wherein shading of the image data is calibrated in response to the calibration data. |
