InoTec SCAMAX 2600, Service Manual

Page: 15 / 68

SCAMAX
®
2600/4000
Tech. Manual 06/2002 T-15
3.1 CCD-Linear-Camera
The CCD linear camera consists of a lens unit mounted on an aluminium plate and a CCD linear sensor
with associated electronics components fixed in a metal housing, which is attached to the aluminium
plate.
The document to be scanned is illuminated in the scan area. The CCD linear sensor captures the
reflected light containing the image information, after it has been refracted by two mirrors and passed
through the lens.
CCD stands for C harge C oupled D evice. It is an electronic component containing capacitor elements
arranged in parallel. The capacitors convert the amount of light received into electrical current, the voltage
generated being proportional to the amount of light detected. An analogue-to-digital converter translates
the charge for each pixel into an 8-bit digital value.
This process takes place at very high speed, the clock speed being 20 MHz. This means that each
second an enormous amount of image information is read and output, i.e. 20 megapixels for bitonal and
60 megapixels for colour (20 for each channel red, green, blue).
The CCD used has 5000 light sensitive pixel elements. This number is sufficient to scan an A4 page in
portrait mode (3,700 pixel) or an A3 in portrait mode (4,670 pixel) at an optical resolution of 400 dpi (dots
per inch).
It is necessary to set the optical reduction in such a way that a width of 1 inch (25.4 mm) covers exactly
400 pixels on the CCD chip (see illustration next page).
For lower resolutions the pixel elements shown in the table below are deactivated:
400
dpi X X X X X X X X X X
300 dpi X X X X X X X X
240 dpi X X X X X X
200 dpi X X X X X
The scan speed (paper transport speed) is automatically adjusted according to the resolution selected.
200 dpi requires only half the number of lines, thus the paper can be transported at double the speed.
SCAMAX 2600 SCAMAX 4000
Resolution in dpi Paper transport speed in m/min. Paper transport speed in m/min.
200 29,3 27,5
240 24,4 X
300 19,6 18,3
400 14,7 13,8