e-STUDIO200L/202L/230/232/280/282 SCANNER June 2004 © TOSHIBA TEC
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6.4 Control of Exposure Lamp
6.4.1 General description
The control circuit for the exposure lamp consists of the following three blocks:
1) Lighting device for the exposure lamp (Inverter)
This device turns the exposure lamp (xenon lamp) ON/OFF.
2) CCD circuit
This circuit converts the light amount reflected from the original surface and shading correction plate
to electrical signals. The exposure amount is controlled in two ways:
- White reference formation – reads the light amount reflected from the white shading correction
plate
- Black reference formation – reads the light amount at the specified position with the exposure
lamp lights OFF
3) Image processing circuit
A series of image processes such as a gamma correction and a shading correction are applied on
the output signal from the CCD. The signal is then digitized and output from this circuit.
Fig. 6-9
PWA-CCD CCD
PWA-SLG
Image processing circuit
Exposure lamp
(
xenon lamp
)
A/D
Scanner
CPU
Lighting device for
exposure lamp
(
inverter
)
Shading correction plateOriginal
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