Toshiba e-STUDIO163 Service Manual page 104

1) High quality image processing
- Background processing function (Range correction)
This function removes undesirable background so that the original can be reproduced appropri-
ately. By using the background adjustment function while manually adjusting the image density,
undesirable background of the original can be removed if any, and some necessary but disap-
peared background can be recovered. By using this function, it is possible to cut the background
density down to zero when copying originals which have a certain level of background density,
such as newspapers.
<Example>
Back-
ground
Lower
- Filtering
This function is enabled by low-pass filter processing and high-pass filter processing.
Low-pass filter processing
This processing removes image/electrical noise and decreases moire by performing averaging
operation between the image signals of the targeted pixel and those of the neighboring pixels to
enhance the reproducibility of original.
<Example>
Density of the targeted pixel position is X. Density of pixel positions at front and back of the tar-
geted pixel are "a" and "b" respectively. X is converted to X' through the low pass filtering.
The above averaging operation is performed for all the pixels to accomplish the high reproducibil-
ity of original.
(The following is the case that the low pass filtering is applied on the primary scanning pixel.)
e-STUDIO163/203 IMAGE PROCESSING
Dynamic range
After range
width
adjustment
Text
Density Higher
Histogram
When the matrix is (3 x 1):
a x
Extended dynamic range
Lower
Fig. 7-3
a+b+x
b
x' =
3
7 - 4
width
Density Higher
December 2005 © TOSHIBA TEC