Minolta Di 620 Manual page 50

The threshold value is transmitted from the PWB-IB to the IR Density Correc-
tion block. This block then corrects the image density of incoming data in
accordance with the relation shown below.
Output
X
0
-b
1155M103CA
For all quality modes other than "Photo," the gradation curve of the density-
corrected data is adjusted in accordance with the Image Quality mode so as
to enhance the reproduction of the high-density areas.
If the Image Quality mode is set to "Photo," however, the gradation curve is
designed to promote image smoothness, even density, and low noise. In this
case, the curve is adjusted in accordance with the manual density setting, as
illustrated below.
The above processing enables the user to select copy density effectively for
any of the image quality modes.
•
The following block diagram illustrates the manual density control flow.
Photoelectric
Conversion (PWB-IA)
¿
X=aχ-b
X: Image density value after density correction
a: 1
χ: Image density value before density correction
Input
χ
-b: Threshold (intercept)
Output
X
Dark
0
CCD (ODD/EVEN)
IR Density Correction
Memory
M-31
Light
Input
χ
1155M106CA
Manual Density Mode
PWB-B
PWB-IB
CPU
1155M107CB