White Paper

Selecting Optimal Avionic and Vetronic Displays for Your Application

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w w w. m r c y. c o m WHITE PAPER 1 Selecting the Optimal Display for Your Application After a cursory analysis, it may seem that all display technology is basically the same and a standard liquid crystal display (LCD) commercial product will be adequate for your program. A closer examination of advanced LCD functionality reveals multiple ways an application-specific display will improve operating safety, enhance end-user efficiency, and reduce complete lifecycle costs. This paper first discusses advanced capabilities that enhance LCD technology and then reviews business factors to consider when selecting or specifying display systems. Effective Night Vision Imaging Systems (NVIS) Most aircraft and land system displays need the ability to provide clear, easily viewed images during both day and night operation. These displays are all equipped with a day/night switch, but there is great variation in the quality of NVIS support and what the end user really sees. Two common issues are night vision 'blooming' and uneven image luminance during night operation. As shown below in Figure 1, 'blooming' is a huge problem for end users with night vision goggles. A standard laptop experiences blooming when the brightness setting is taken to its lowest viewable setting, or steps down luminance for its light emitting diodes (LEDs) to a lesser percentage when switched to night mode. The same effect occurs in some deployed helicopters and ground vehicles, impacting warfighters' situational awareness and reaction efficiency. A commercial-grade NVIS filter can be used, but this often effects the red chromaticity, giving images an orange hue. This, in turn, reduces the light transmitted through the LCD, making details less clear across all sections of the image. Figure 1: View through a camera with a night vison lens Blooming can be eliminated if the display implements a true dual mode, with separate day and night backlighting approaches. This type of dual mode backlighting may offer either white or RGB LEDs for daylight operation and separate NVIS-compatible LEDs for night operation. The NVIS backlighting LEDs should be capable of a wide range of luminance from 650–930nm. Very low-level luminance can be achieved by a burst modulation scheme; an explicit NVIS LED wavelength cutoff below 650nm goes even further to prevent NVIS blooming. The second night operation issue, uneven display luminance, is also common in commercial, and even industrial, quality displays. When night mode means reduced luminance, light is no longer distributed evenly across the display and 'spotlights' appear on the edges, interfering with end-user image perception. The same separate NVIS LEDs used to eliminate blooming also can be equipped with optimized, display- specific light guides that spread the low-level light evenly across the display so there are no spotlights. Sunlight Readability The flip side of effective NVIS is effective sunlight readability. In the bright light of a desert, tropical ocean, or arctic environment, the challenge is to deliver more luminance to a display so that image details can still be easily seen by end users. Commercial-grade LCD displays use lower-cost COTS LEDs and operate them at close to, or above, 100 percent of their maximum voltage during normal operations, so there is no headroom for a luminance increase in bright sunlight. One path to a solution is to use LEDs that normally function at less than half of their rated power capacity, so there is room to incrementally increase luminance over time, as the LED inevitably will degrade. This desired longevity effect can be further enhanced if an etched light guide is used to diffuse the light from the LED, maximizing its effectiveness. These solutions are also useful in dealing with a related issue, extended display life, which is discussed later in this paper. Displaying All the Image Details Available from a Sensor Figure 2: The bit depth of a display is key to delivering image details Modern display systems must be able to present sensor information to end users with as much detail as possible. Using a display without enough bit depth to closely match the sensor video output means that critical details will be lost. As shown in Figure 2, at the same range, an image only distinguishable as a human being at eight bits can be clearly identified as an armed warrior wearing typical NATO standard dress and carrying a typical NATO M5 weapon at a higher 10-bit gray scale, matching the 10-bit sensor. Effective display of today's sensor technology is achieved with a 10-bit native display (30-bit RBG), creating images with 1.3 billion colors and 1024 shades of gray. This grayscale depth, even using XGA standard resolution and 1:1 pixel matching to a thermal imaging (TI) sensor, renders an image perceived by end users as HD quality. Current applications of thermal imaging offer an increasing ability to discriminate at long range, but are only maximized when paired with a 10-bit display that closely matches the thermal imaging raw video output capability. Ten-bit displays are also highly effective for all types of night vision imagery, especially when compared to 8-bit displays. The two extra bits of grayscale depth give users a fourfold increase in image clarity (from

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