VIDEO DATA PROCESSING
31 March, 1999
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2.9.3 GRADATION PROCESSING
The gamma-compensated data is dithered.
The result of dithering depends on whether 1-bit or 2-bit mode was selected with
the driver.
After dithering, the data is converted to 4-bit and sent to the engine through the
video interface.
•
1-bit mode: The output for each pixel after dithering is either 0 or 1. This
becomes either 0 or F after conversion to 4-bit data.
•
2-bit mode: The output for each pixel after dithering is 0, 1, 2, or 3. This becomes
either 0, 5, A, or F after conversion to 4-bit data.
2.9.4 AMDG (ADAPTIVE MULTI-DOT GAMMA)
This process converts 4-bit data into 8-bit data (256 shades).
Each pixel is compared with a range of pixels above and to the left, and is
converted to an 8-bit value based on the results, using an internal look-up table.
The data then passes to the GAVD (Gate Array Video) interface through the laser
diode control chip (HEMA) on the LD unit.
2.9.5 LASER DIODE CONTROL
Modulation
PM and PWM modulation for LD control converts the 8-bit data (equivalent to 256
gradations) to laser power levels.
Smoothing
Smoothing only occurs if the following settings have been made with the printer
driver.
•
Resolution: 600 dpi
•
Color level: 1-bit
•
Smoothing: Auto
The LD controller smooths the data to reduce jagged edges. Normally, the laser
writes the coloured part of each pixel at the left side of the pixel. However, to
smooth the image, the laser sometimes writes the coloured part at the right side of
the pixel. The machine determines automatically which pixels have to be treated in
this way.
