Advanced Video Control Unit (AVCU) User Guide
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DITHERING CONTROL AND CONFIGURATION
The most recent NVIS products include enhanced capabilities to manipulate the color
performance to reduce color sequential artifacts (the LCOS is a reflective, color sequential
display).
The LCOS micro-displays used in NVIS products are monochrome reflective devices. Color is
provided through the illumination source
—in the case of NVIS products, this is accomplished with
a diffuse RGB LED source. The LCOS pixels exist in one of two states
– on or off. The display
can adjust the intensity of each color on a per pixel basis through temporal modulation of the pixel
– turning it on and off in rapid succession to achieve the correct intensity of each color from the
LED. This occurs per color, per frame, at 60 Hz.
In some applications, users may perceive
dynamic false contouring
(DFC) in regions of the
database that contain transitioning color gradients or textures with many gray levels. This situation
is caused by the time delay between modulating for the first and last bit of a given color. By
truncating the bit depth for each pixel, you can reduce this time delay and the effects of DFC.
The dithering hardware available in the current generation of NVIS products contains
enhancements to boost the color depth with an algorithm that operates on a pixel-by-pixel basis,
requiring no frame store (and therefore, no latency). This allows the hardware to effectively
“reclaim” the bit color depth that is lost.
All dithering-capable units are set to 4 bits per color (most significant), and 4 bit dither boost for
an effective 8 bit color depth. To view or change these settings, use SXprog:
Launch the SXprog application while the NVIS unit is ON, and the computer is connected to
the VCU via the included 9-pin RS-232 serial cable (straight through).
Click
Connect
.
When you are connected, click on the
Settings
tab.
You will see the Settings dialog box shown in Figure 15.
