Toshiba 350, 452, 453, 353 service manual Control of Exposure Lamp, General description

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6.4 Control of Exposure Lamp

6.4.1 General description

Control circuit for the exposure lamp consists of the following three blocks:

(1)Lighting device for the xenon lamp (Inverter) Turns ON/OFF the exposure lamp.

(2)CCD circuit

This circuit converts the reflected light amount from the original surface and the shading correc- tion plate to electrical signals. The exposure amount is controlled in two ways:

(a)White reference formation - reads the reflected light amount from the white shading correction plate

(b)Black reference formation - reads the light amount at the regulation position with the expo- sure 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 Shading correction plate

Exposure lamp (xenon lamp)

Lighting device for xenon lamp (Inverter)

PWA-CCD CCD

PWA-SLG

A/D		Scanner
		CPU
	Image processing circuit

Fig. 6-401

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