Toshiba 3511, 4511 manual ’ = + b +

7

(c)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 targeted pixel are “a” and “b” respectively. X is converted to X’ through the low pass filtering.

When the matrix is (3 x 1):

a x b	x’ =	a + b + x
		3

The above averaging operation is performed for all the pixels to accomplish the high reproducibility of original.

(The following is the case that the low pass filtering is applied on the primary scanning pixel.)

Density										Density
										After low-pass filter
0	1	2	3	4	5	6	7	8	9	0	1	2	3	4	5	6	7	8	9

Primary scanning pixel positions Primary scanning pixel positions

Fig. 7-302

•High-pass filter processing

Character outline blurs when the original, such as text, with big difference in density among the pixels is optically scanned and output from the CCD. Characteristic of the lens and other factors cause this phenomenon. In this equipment, processing such as edge enhancement is applied between the targeted pixel and the neighboring pixels to eliminate this phenomenon and realize high reproducibility of original.

Solid black area

Original

Image signal

Low contrast area

After correction

Fig. 7-303

e-STUDIO3511/4511 IMAGE PROCESSING 7 - 6 November 2003 © TOSHIBA TEC