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US 2010/0142009 A1Published application
Image reading apparatus
AssigneeRicoh Company, Ltd.
InventorsHajime TSUKAHARA, Tohru Kanno
Life of this patent
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Abstract
When a light source is in off state, a gray level of image data on a pixel-by-pixel basis is generated as a first black level and an average of gray levels of a portion of the image data corresponding to optical black image portions of sensor chips is generated as a second black level. After that, when an image of an original is read, an average of gray levels of the black image data on a line-by-line basis is generated as a third black level. The first black level is subtracted from a gray level of the image data on a line-by-line basis (an offset correction), and a difference between the third black level and the second black level is added to a gray level of the image data after being subjected to the subtraction on a line-by-line basis.
Claims15
An image reading apparatus comprising:
- an image reading unit configured to scan a printed side of an original in a main scanning direction with a light source turned on and to perform a photoelectric conversion of a reflected light from the printed side on a line-by-line basis with a photoelectric conversion element to read as an analog image signal;
- an analog-to-digital conversion unit configured to convert the analog image signal read by the image reading unit into a digital image signal and outputting the digital image signal;
- a first-black-level generating unit configured to generate, as a first black level, a gray level of the digital image signal outputted from the analog-to-digital conversion unit on a pixel-by-pixel basis in a state where the light source is turned off;
- a second-black-level generating unit configured to generate, as a second black level, an average of gray levels of a portion of the digital image signal outputted from the analog-to-digital conversion unit that corresponds to an optical black image portion in the photoelectric conversion element when the first-black-level generating unit generates the first black level generated on the pixel-by-pixel basis;
- a third-black-level generating unit configured to generates, as a third black level, an average of gray levels of the portion of the digital image signal outputted from the analog-to-digital conversion unit that corresponds to the optical black image portion in the photoelectric conversion element when an image of the original is read;
- and
- an offset correction unit configured to perform an offset correction of the gray level of the digital image signal outputted from the analog-to-digital conversion unit when an image of the original is read based on the first black level generated by the first-black-level generating unit and a difference between the third black level generated by the third-black-level generating unit and the second black level generated by the second-black-level generating unit.
4 more elements
An image reading apparatus comprising:
- an image reading unit configured to scan a printed side of an original in a main scanning direction with a light source turned on and to perform a photoelectric conversion of a reflected light from the printed side on a line-by-line basis with a photoelectric conversion element to read as an analog image signal;
- an analog-to-digital conversion unit configured to convert the analog image signal read by the image reading unit into a digital image signal and outputting the digital image signal;
- a first-black-level generating unit configured to generate, as a first black level, a gray level of a portion of the digital image signal outputted from the analog-to-digital conversion unit that corresponds to the photoelectric conversion element on a pixel-by-pixel basis in a state where the light source is turned off;
- a second-black-level generating unit configured to generate, as a second black level, an average of gray levels of a portion of the digital image signal outputted from the analog-to-digital conversion unit that corresponds to an optical black image portion in the photoelectric conversion element when the first-black-level generating unit generates the first black level generated on the pixel-by-pixel basis;
- a third-black-level generating unit configured to generates, as a third black level, an average of gray levels of the portion of the digital image signal outputted from the analog-to-digital conversion unit that corresponds to the optical black image portion in the photoelectric conversion element when an image of the original is read;
- a first offset correction unit configured to perform an offset correction by subtracting the first black level generated by the first-black-level generating unit from the gray level of the digital image signal outputted from the analog-to-digital conversion unit when an image of the original is read;
- and
- a second offset correction unit configured to perform an offset correction with respect to the analog image signal read by the image reading unit when an image of the original is read based on a difference between the third black level generated by the third-black-level generating unit and the second black level generated by the second-black-level generating unit, wherein
- the analog-to-digital conversion unit converts the analog image signal subjected to the offset correction by the second offset correction unit into a digital image signal when an image of the original is read.
6 more elements
An image reading apparatus comprising:
- an image reading means for scanning a printed side of an original in a main scanning direction with a light source turned on and performing a photoelectric conversion of a reflected light from the printed side on a line-by-line basis with a photoelectric conversion element to read as an analog image signal;
- an analog-to-digital conversion means for converting the analog image signal read by the image reading means into a digital image signal and outputting the digital image signal;
- a first-black-level generating means for generating, as a first black level, a gray level of the digital image signal outputted from the analog-to-digital conversion means on a pixel-by-pixel basis in a state where the light source is turned off;
- a second-black-level generating means for generating, as a second black level, an average of gray levels of a portion of the digital image signal outputted from the analog-to-digital conversion means that corresponds to an optical black image portion in the photoelectric conversion element when the first-black-level generating means generates the first black level generated on the pixel-by-pixel basis;
- a third-black-level generating means for generating, as a third black level, an average of gray levels of the portion of the digital image signal outputted from the analog-to-digital conversion means that corresponds to the optical black image portion in the photoelectric conversion element when an image of the original is read;
- and
- an offset correction means for performing an offset correction of the gray level of the digital image signal outputted from the analog-to-digital conversion means when an image of the original is read based on the first black level generated by the first-black-level generating means and a difference between the third black level generated by the third-black-level generating means and the second black level generated by the second-black-level generating means.
4 more elements
Dependencies are inferred from the claim text.