Functions Of Image Processing Circuit - Toshiba e-STUDIO167 Service Manual

7.3.2

Functions of image processing circuit

1) High quality image processing
- Background processing function (Range correction)
This function processes to remove undesirable fog from the background so that the original can
be reproduced appropriately. By using this function, it is possible to cut the background density
down when copying originals which have a certain level of background density, such as newspa-
pers.
<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.
e-STUDIO167/207/237
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
© February 2007 TOSHIBA TEC CORPORATION All rights reserved
7 - 4
width
Density Higher