Bi-directional LEDs – Ci 24 and 40
Most CIS wide format scanners have one set of LEDs positioned at one end of each CIS sensor. These LEDs are shone down a single light guide to provide illumination.
In the Colortrac SmartLF Ci 24 and Ci 40 large format scanners, each CIS sensor has two sets of LEDs, one at each end. These are shone down two light guides. Because illumination is bi-directional instead of uni-directional there is less potential for shadowing.
Bi-directional LEDs – Gx+ 28, 42 and 56
Most CCD wide format scanners are illuminated by fluorescent tubes.
Colortrac SmartLF Gx+ 28, 42 and 56 large format scanners are illuminated by white LEDs which are shone from either side of the CCD cameras.