Toshiba e-STUDIO 160 Service Manual page 103

(2) Filtering
This function uses a low-pass filter circuit and a high-pass filter circuit.
(a) Low-pass filter circuit
By averaging the differences between the target pixel and its adjacent ones, the circuit eliminates
image and electrical noise as well as restricts moire to obtain an image with high reproducibility of
the original.
For example, assuming the density of the target pixel position to be x, and the densities of its front
and back positions to be a and b, respectively, the density of the target pixel position x' after low-
pass filter operation is given as follows.
For (3 x 1) matrix:
a x b
The above operation is performed for all pixel positions to accomplish high original reproducibility.
The following figure shows the low-pass filtering processing on the primary scanning pixel.
Density
0 1 2 3 4 5 6 7 8 9
Primary scanning pixel positions
e-STUDIO160/200/250 IMAGE PROCESSING
a + b + x
x'=
3
6 - 4
Density
After low-pass
filter processing
Primary scanning pixel positions
0 1 2 3 4 5 6 7 8 9
December 2002 TOSHIBA TEC
07005