Scanner and ADF functions and operation
The following sections describe how the document scanner and the automatic document feeder (ADF)
function.
Scanner functions
The scanner uses a light source, a color-separation method, and a charge-coupled device (CCD) array
to collect optical information about the document and transform that into an image file. The scanner
consists of these elements:
●
A lamp (LED)
●
Five mirrors and a lens
●
A CCD
Figure 5-23 Optical system
Lens
LED Lam p
Scanner Glass
600 ppi CCD
The scanner lamp illuminates a small strip of the document (called the raster line). The mirrors direct
the light through the lens to the CCD. The CCD senses and records the light, creating an analog
representation of the raster line. If the ADF is being used, the document then advances in the ADF to
the next raster line. If the flatbed is being used, the scanner module advances to the next raster line.
This advancing and collection process continues to the end of the sheet.
The image data is collected in the motor controller board, where it is processed and sent to the formatter.
The formatter then handles the image data, outputting it as a copy, sending it through the fax card as a
fax, or directing it to the computer as scanner output.
The image data collected is 600 pixels per inch (ppi). Each pixel has 8 bits for each of the three colors
(256 gray scale levels for each color), or a total of 24 bits per pixel (24-bit color).
106 Chapter 5 Theory of operation ENWW
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