e-STUDIO182/212/242
© 2009 TOSHIBA TEC CORPORATION All rights reserved
SCANNER
6 - 10
Optoelectronic conversion
The CCD of the contact image sensor (CIS) unit in this equipment performs photoelectronic conversion
and charge transfer by the combination of its shift registers and photodiodes (light-receiving sensors) to
output signals for a primary scanning direction.
Each light-receiving sensor photoelectronically converts the received light into charge and transfers the
charge to each shift register. These shift registers then transfer the charge at the timing of transfer
clocking. This transfer clock pulse is equally input into every chip, and thus all the shift registers are
driven at the same timing. The charge transferred into each chip is then combined into each channel,
and then output in a time division system. Furthermore the multiple channels simultaneously perform
this process to output the scanning signals of the multiple systems in parallel.
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 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)
Summary of Contents for e-studio182
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Page 128: ...e STUDIO182 212 242 2009 TOSHIBA TEC CORPORATION All rights reserved LASER OPTICAL UNIT 7 8 ...
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