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Selecting Optimal Avionic and Vetronic Displays for Your Application

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2 256 > 1024), allowing them to identify details in images with limited dynamic range. The extra bit depth adds both subtlety to the gradations in tone that are displayed and the range to obtain the higher clarity. For color images, the added bit depth allows smoother color transitions that significantly improve user accuracy in interpreting fine details. This is especially true when the images are from a modern 12-bit or higher color camera. Ten-bit capability makes images look natural and smooth, delivering undetectable color transitions. How an LCD Works An LCD consists of a liquid crystal fluid in between two pieces of polarized glass, aka substrate. A backlight, typically from strings of LEDs, creates light that passes through the first substrate. Low-voltage electric currents from the display controller cause the liquid crystal molecules to align in ways that allow various levels of light to pass through to the second substrate, creating colors and images. To further enhance user perception of imagery, displays can use specifically manufactured LEDs that are color matched with the phosphor content of the LCD color filters. By controlling the color filter selection of the LCD and the phosphor selection of the backlight LEDs, a display's optical performance is maximized. Using increased color depth and LED color matching delivers impressive increases in end-user image perception with a huge systems engineering advantage; the platform network does not have to be redesigned to achieve a better image. Some platform upgrade requirements now specify HD imaging systems when, in fact, the display components are incapable of rendering HD images without a wholesale replacement of the supporting vetronics infrastructure so it can support HD bandwidth requirements. A better solution is to simply use displays that fit the current network but are enhanced to get the most out of the sensor imagery and then modify the sensor video processing algorithm to output in higher-color depth and grayscale. Optimized Images for Multiple Applications in One Display Because humans have better perception of differences between darker tones than lighter ones, most applications use a gamma encoding of imaging to optimize the use of image signal bits. Without gamma encoding, applications would allocate too many bits (and too much bandwidth) to highlight differences that humans can't differentiate and too few bits to shadow values where humans are sensitive, reducing visual quality. However, optimal gamma encoding varies by the display application. It is commonly around 2.2 but may be .78 for a thermal-imaging application and 1.8 for a battle graphic. On today's platforms, most displays are supporting between three and six different applications. To deliver the best possible visual quality to the end user, these displays need to have simultaneous support for multiple gamma encoding values, with seamless matching of those values to the appropriate application- controlled windows. No commercial-quality LCD can deliver that capability without customization. Eliminating Windscreen or Bubble Canopy Display Reflections Aircraft crewmembers have long struggled with reflections on the windscreen or bubble canopy from flat panel cockpit instrument displays. The wide viewing angle of a normal LCD, very desirable when watching TV at home, floods a cockpit with light, often with some images reflecting off the windscreen or canopy glass. This problem is especially acute during night visual flight rules (VFR) operations (Figure 3). The reflected images may distract pilots, interfere with their long-range vision through the canopy, and even cause disorientation. The overall effect can be distracting or, worse, life threatening. Now it is possible to eliminate undesirable canopy reflective optics by controlling off-angle luminance with a tightly packed array of fiber optic elements embedded in the display glass. Each fiber is coated in a black cladding and is many times smaller than the pixel window of an LCD. These innovations deliver an effect similar to looking through a matrix of packed straws; the view is clear directly in line with the straws, but blocked if viewed from the side. Light from a display is directed into a desired viewing angle, making it easily visible only for the pilot or copilot, without the stray light optics that cause cockpit reflections. Bubble Canopy WP: https://www.mrcy.com/resourcehub/avionics/dual- redundant-display-in-bubble-canopy-applications Figure 3: Flight crew windshield display reflections

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