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White reference data generating unit applied to shading correction system
| Details |
Inventors: Ito, Masaaki;
Assignee: Ricoh Company, Ltd. (Tokyo, JP)
Primary Examiner: Coles, Sr.; Edward L.
Assistant Examiner: Vu; Kim Yen
Attorney, Agent or Firm: Oblon, Spivak, McClelland, Maier & Neustadt
A white reference data generating unit which generates white reference data used in a shading correction process includes a line memory for storing white reference data, a determination circuit for determining whether or not the image data supplied from an image sensor is equal to or less than a predetermined threshold level, a updating circuit for updating the white reference data stored in the line memory to new white reference data calculated based on the white reference data stored in the line memory and input data while each line on a white reference plate is scanned, and a selector for supplying the image data, as the input data, to the updating circuit when the determination circuit determines that the image data is greater than the threshold level, and for supplying difference data, as the input data, to the updating circuit when the determination circuit determines that the image data is equal to or less than the threshold level, the difference data being obtained by subtracting a predetermined value from the white reference data stored in the line memory. |
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DETAILED DESCRIPTION What is claimed is: 1.
A white reference data generating unit for generating white reference data based on image data which is obtained while an image sensor means is scanning on a white reference plate in a predetermined number of lines, said white reference data being used in a shading correction process, said white reference data generating unit comprising: storage means for storing the white reference data; determination means, coupled to said image sensor means, for determining whether or not the image data supplied from said image sensor means is equal to or less than a threshold level based on data stored as the white reference data in said storage means; updating means, coupled to said storage means, for updating the white reference data stored in said storage means to new white reference data calculated based on the white reference data stored in said storage means and input data while said image sensor means is scanning each line on said white reference plate; and supply means, coupled to said storage means, said determination means and said updating means, for supplying the image data, as the input data, to said updating means when said determination means determines that the image data is greater than the threshold level, and for supplying difference data, as the input data, to said updating means when said determination means determines that the image data is equal to or less than the threshold level, said difference data being obtained by subtracting a first value form the white reference data stored in said storage means.
2.
A white reference data generating unit as claimed in claim 1, wherein said threshold level used in said determination means is a level less than the white reference data stored in said storage means by a second value.
3.
A white reference data generating unit as claimed in claim 2 further comprising subtraction means for subtracting the second value from said white reference data stored in said storage means, wherein a result obtained by said subtraction means is used as said threshold level
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Image Analysis 
