Fujitsu fi-4990C Dither, Dpi, Duplex reading mode, Endorser, Equipment Error, Error diffusion

Dither

Technique for producing halftone images representing grayscale by using a pattern of the two pixel levels black and white.

dpi

Dots per inch.

Drop-out color

A color which is used to illuminate the document but does not appear in the read image.

Duplex reading mode

Both sides of the document are read in this mode.

Endorser

The unit for printing characters before or after scanning. These character may be used for collation of the documents and the image data.

Equipment Error

An error that is not recoverable by operator. Call an authorized maintenance engineer.

Error diffusion

High-quality halftone (pseudo-grayscale) image production based on black-and-white pixel binarization. A pixel’s optical density and that of adjacent pixels are summed, with black pixels relocated in their order of density as they relate to adjacent pixels.

The purpose of this technique is to minimize the average error between read and printed densities. Density data for adjacent pixels is modified by diffusing errors on the objective pixel into several pixels, which are then binarized. This maintains high grayscale levels and resolution during reading, while suppressing more patterns by dotted halftone images such as newspaper photo graphs.

Filtering

The quality of images written in pencil or ball-pointed pen and read depends on the reflective light characteristics of the ink or lead.

Dropped pixel’s may produce out lines, gaps or thin, barely connected lines due to even optical density. Filtering detects areas lighter than their surroundings and increases their density to improve image clarity.

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