Control Of Exposure Lamp; General Description - Toshiba e-STUDIO200L Service Manual

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.
Original
PWA-CCD CCD
e-STUDIO200L/202L/203L/230/232/233/280/282/283
SCANNER
Shading correction plate
Exposure lamp ( xenon lamp )
PWA-SLG
A/D
Image processing circuit
Fig. 6-9
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Lighting device for
exposure lamp
( inverter )
Scanner
CPU