Canon MultiPASS C530, Service Manual

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MultiPASS C530/C560 Chapter 2: Technical Reference
8.3.2 Reading color documents
When scanning a line of a color document, the 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 SPCNT board’s system control IC (IC 4) uses the 8-bit data stored in memory
for each LED color to generate print image data for the colors Cyan, Magenta, Yellow, and Black
(CMYK data). 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 CMYK 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 parallel data and sent to the PC via the Centronics interface.
8.3.3 Reading black & white documents
When scanning black and white documents, the Red, Green and Blue LED’s are lit sequentially for 1/3
the duration used for color scanning, providing illumination equivalent to the same duration of white
light.