GL843 datasheet(73/84 Pages) GENESYS

73 / 84 page

GL843 High Speed USB2.0 With ADF 2-in-1 Scanner Controller For 3x

Page 73

8 Support Analog Front End Timing

GL843 supports external 16 bits front-end.

Wolfson: WM8192, WM8199, …etc.

Analog device: AD9826, …etc.

9 Image Type

A. Supports color, gray and line art scanning.

B. Supports color filters options (R, G or B channels) in gray or line art scanning.

C. Supports true gray with programmable R, G and B weightings.

10 Bits Depth

16*3 bits color, 16 bits gray level and 1 bit line art (Black & White).

Image data type: 16 bits, 8 bits and 1 bit.

11 Shading & Correction

a. White Shading & Dark Shading:

White shading and dark shading are pixel-by-pixel corrections with 16-bit solution and can be enabled or

disabled by S/W. The white shading curve is calculated by S/W.

Data arrangement: three line in mode: dark R1, white R1, dark G1, white G1, dark B1, white B1,

dark R2, white R2, dark G2, white G2, dark B2, white B2,

dark R3, white R3, dark G3, white G3, dark B3, white B3,

one line in mode: dark R1, white R1, dark R2, white R2, dark R3, white R3…

dark G1, white G1, dark G2, white G2, dark G3, white G3…

dark B1, white B1, dark B2, white B2, dark B3, white B3…

White shading formula:

2000H * Target / (Wn-Dn) = White Gain data ----- for 8 times system

White shading formula:

4000H * Target / (Wn-Dn) = White Gain data ----- for 4 times system

For example: Target = 3FFFH,

Wn = 2FFFH,

Dn = 0040H and 8 times system operation

then White Gain = 2000H * 3FFFH / (2FFFH-0040H) = 2AE4H (1.34033 times)

b. Gamma Correction:

16-bit GAMMA correction table is programmed by S/W.

Range: 0 ~ 64k (16 bits) input mapping to 0 ~ 255 (8 bits) output.

Style: increment or decrement gamma curve

Note: 16 bits image data will be mapped to 8 bits data by gamma table. Designer can get 16 bit image data

by disabling gamma table.

12 Threshold Setting for Line-Art

Threshold can be programmed by S/W.

Range: 0 ~ 255 adjustable.

The threshold with hysteresis characteristic is for reducing image noise.

BWHI

BWLOW

hysteresis width

a,b,c,g : are black pixels

d,e,f,h,i : are white pixels

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