Toshiba 4511, 3511 manual Functions of image processing circuit, Example

7.3.2 Functions of image processing circuit

The image processing section on the SYS board realizes the followings:

(1)ACS (Auto Color Selection)

This function determines whether the original to be scanned is colored or monochrome, based on the analysis of the R, G and B signals output from the CCD.

(2)Color conversion (CMY image data processing)

When functioning the copier, the RGB image data is converted to CMY image data. (When functioning the scanner, it is converted to RGB image data.)

The image data taken in by the scanner represents the intensities of reflection from the three primary colors of light (Red, Green and Blue). These RGB values are then color-converted to the respective amounts of toners corresponding to the three colors (Yellow, Magenta and Cyan) for printing (=CMY image data processing).

(3)Black component generation

K (Black) signal is generated from the CMY image data. Based on this K signal, the CMY image data is corrected to suppress hue on reproducing grays or to make the black look more real.

(4)High quality image processing

(a)Background processing function

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 disappeared background can be recovered. 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 newspapers.

<Example>

Larger		Dynamic range		Larger	Extended dynamic
		width	After background			range width
			processing
pixels	Back-			pixels
of	ground			of
No.				No.
Smaller			Text	Smaller
	Lower	Density	Higher		Lower	Density	Higher

Histogram

Fig. 7-301

(b)Image discrimination

By determining the magnitude of density variation in a block (n x n dot), the target pixels are judged whether they are text or photograph. If they are determined to be text, they are further judged whether they are black or color text, using the differences in the levels of CMY signals.

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November 2003 © TOSHIBA TEC 7 - 5 e-STUDIO3511/4511 IMAGE PROCESSING