| US 7,609,422 B2 | ||
| Document reading apparatus that reads a document image with a CCD image sensor | ||
| Yoshinobu Kagami, Yokohama (Japan) | ||
| Assigned to Ricoh Company, Ltd., Tokyo (Japan) | ||
| Filed on Sep. 14, 2004, as Appl. No. 10/939,460. | ||
| Claims priority of application No. 2003-326920 (JP), filed on Sep. 18, 2003. | ||
| Prior Publication US 2005/0105143 A1, May 19, 2005 | ||
| Int. Cl. H04N 1/04 (2006.01) | ||
| U.S. Cl. 358—483 [358/474] | 6 Claims |
| 1. A document reading apparatus, comprising:
a light source configured to irradiate the surface of a document with light;
an optical system configured to lead the light reflected by the document to a predetermined position;
a photoelectric converter array configured to photoelectrically convert the light led by the optical system, pixel outputs
of the photoelectric converter array being allocated to a plurality of terminals and then being output;
an A/D converter unit configured to analog-to-digital convert each pixel output from the photoelectric converter array to
produce digital outputs that are integers;
an average output value detecting unit configured to detect the average value of the integer digital outputs of each terminal
converted by the A/D converter unit; and
a terminal difference correcting unit configured to correct the integer digital outputs of a first one of the terminals in
response to a difference between the average value of the first one of the terminals and the average value of a second one
of the terminals, a decimal being distributed to the integer digital outputs of the first one of the terminals when the difference
in average values includes the decimal, wherein the terminal difference correcting unit includes
at least one random value generating adder/subtractor unit configured to perform an arithmetic operation on an integer digital
output of the integer digital outputs, using the equation:
Dout=ROUND(Din−0.5+RAND+a), wherein
“ROUND” is a round-off function for rounding off a decimal, “Din” is the integer digital output, “RAND” is a random value between 0 and 1, “a” is the difference in average values, and “Dout” is the corrected integer digital output.
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