Minolta Di 620 Manual page 47

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The control flow for auto density (AE) control is shown below.
The scanner starts normal scanning of the document. (The copy cycle starts.)
The image data read by the CCD sensor is transmitted (in parallel) from
the Shading Correction block to the Histogram block, where the data val-
ues are sampled, and the samples are counted in order to generated the
reflectivity histogram.
The CPU determines the type of the original based on the histogram, and
sets the removal threshold accordingly.
The CPU transmits the threshold value to the IR Density Correction block.
This block then corrects the image density of incoming data in accordance
with the relation shown below.
Output
X
0
-b
Start Key ON
<Realtime Scanning>
X=aχ-b
X: Image density value after density correction
a: 1
χ: Image density value before density correction
-b: Threshold (intercept)
Input
χ
1155M103CA
To ¿ on next page.
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