Canon MultiPASS C5000 Service Manual page 103

When scanning a line of a color docummt, thr LED's are sequentially lit: first Red, then
Green, then Blue. The corresponding image data of the line are then read and stored to
memory. The Red, Green and Blue LED's are mounted on the white LED board at the right
side of the contact sensor. The light emitted from the LED's passes through the optical
guide, where it is reflected, gathered. and projected at the document.
During color copying, the SCNT board's Color Image Processing IC UC 902) uses the a-bit
data stored in memory for each 1X1) color to generate print image data for the colors Cyan,
Magenta, Yellow, and Black ( CMYK data 1. Generation of CMYK data is independent
from the reading contact sensor data. When CMYK data generation is slower than the
reading process, reading is halted until ChIYK data generation is completed.
When using the unit as a color scanner, the Red, Green and Blue data which were scanned
and stored to memory are converted to ~.'a~~Jlel data and sent to the PC via the Centronics
interface.
8.1.3 Reading black & white documents
When scanning black and white dacumcnts, the Red, Green and Blue LED's are lit
sequentially for l/3 the duration used foT color scnnning, providing illumination equivalent
to the same duration of white light.
Figure 2-23 Contact Sensor
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Chapter 2: Technical Reference