Epson Perfection 640U Series Manual - Página 5

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Image Quality—Epson ColorTrue® Imaging System (cont.)

3. Processing: Many Epson scanners use a custom ASIC (Application Speciﬁc Integrated Circuit) for fast

scanning. Key features include:

Line correction captures and processes full RGB color for every pixel and minimizes color fringing in



subscan direction.

Zoom capability enables smoothest edges along diagonal or curved lines and achieves higher



interpolated resolution

On-board memory allows for Auto Area Segmentation (AAS) and Text Enhancement Technology (TET)



processing within the scanner—AAS and TET are independent from PC or Macintosh processing,

allowing the scanner to work with better "raw" data.

Additionally, Epson scanners have a pixel optimization feature

that uses the full resolution of the scanner's CCD, even scanning

at a lesser resolution. The beneﬁt of this feature is truer image

quality.

For example, on one of the Epson 600 dpi Perfection



scanners, when scanning an image at 300 dpi, the scanner

still uses all 600 pixels per inch to scan the image, then

averages the data to yield the lower resolution image.

Some competitive models lower resolution by turning off



some pixels to capture less image data.

Image Quality—Color CCD

All Epson scanners use a color CCD which uses a single white light source, instead of a monochrome CCD

and three light sources. The color CCD results in faster scanning speeds and the ability to scan three-

dimensional objects without producing color "ghosts."

Key Differences Color CCD

How it works

Result when

scanning three-

dimensional objects

Scanner Technical Brief—Page 5

Red, green, and blue are quickly captured

in the color CCD illuminated by a single

light source.

Glass

Color CCD

Single light source allows precise

alignment when scanning non-ﬂat

surfaces

Monochrome CCD

three separate lamps are ﬁred for eachline

of a scan, slowing the scanning speed.

Glass

Monochrome

CCD

White light

source

The three lamps can cause misalignment

when reﬂected from non-ﬂat surfaces.

Epson Method:

Competitive Method:

Off

Red light

source

Green light

source

Blue light

source

Off

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