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H. CCD gamma correction
a. Outline and purpose
The CCD elements of R/G/B have gamma fluctuations, which are cor-
rected to make proper balance of gray (color) when scanning images.
rected to make proper balance of gray (color) when scanning images.
b. Details of operation
For correction, the SIT chart is used.
1) Execute SIM 63-3 to read the gray pattern of the SIT chart. Calcu-
late the shit between the read pattern gamma and the reference
gamma to obtain the correction level, and store it.
gamma to obtain the correction level, and store it.
2) Apply the gamma correction data to the read images in actual im-
age scanning.
The above operation is performed for each CCD element of R/G/B.
White sheet image data signal
Calculated Sharding correction ratio data and memorize
CCD
WHITE SHEET
LAMP ON
Original image data signal
Readout the Sharding correction data and
make the sharding correction
Corrected image(True image data signal)
CCD
DOCUMENT
LAMP ON
Original image data signal
Non correction image data
CCD
DOCUMENT
LAMP ON
No sharding correction
SHARDING CORRECTION
Output
density
density
Input density
High
Low
Low
High
CCD
CORRECTION
Original(No correction)
Referance
curve
High
CCD
CORRECTION
Output
density
density
Input density
High
Low
Low
After Correction
Referance
curve
Output
density
density
Input density
High
Low
Low
High
CCD
CORRECTION
Correction
Referance
curve
Correction value
Before
correction
correction
After correction
AR-C150
3 – 10
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