Toshiba e-STUDIO 206, Service Manual

Page: 99 / 238

6
© February 2007 TOSHIBA TEC CORPORATION All rights reserved e-STUDIO166/206
SCANNER
6 - 11
Shading correction
A variation is caused by the following factors in the CCD output.
1) The light source has a variation in its light distribution.
2) Each of the 7,084 elements varies in optoelectronic conversion efficiency.
These differences need to be corrected and this correction is referred to as a shading correction. The
shading correction is performed by applying a normalization process using the following formula on the
black data and the white data obtained in advance to correct the lighting variance and element variation
of the image data.
( S - K )
( W - K )
I = k
x
k: Coefficient
S: Image data before correction
K: Black data (stored in "Black" memory)
W: White data (stored in "White" memory)