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We measured color-breakup thresholds for a simple field-sequential color stimulus while varying its luminance, contrast, and retinal velocity. Data analysis yielded an equation that predicts whether color breakup will be visible for specified viewing conditions. We compare this equation with an earlier version and discuss its uses and limitations.

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The quest for color head-and helmet-mounted displays has led some designers to consider the use of field-sequential color (FSC) because it offers higher resolution than conventional color displays in a compact package. Unfortunately, FSC displays exhibit color breakup sometimes, and the viewing conditions under which this occurs have not been established very well. We performed an experiment to determine color-breakup thresholds for a simple FSC stimulus as a function of stimulus luminance, contrast, and retinal velocity. We developed equations that describe the results and can be used to predict whether color breakup will be visible for specified viewing conditions.

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Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden, to Washington Headquarters Services, Directorate for Information Operations and Reports, 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202-4302, and Previously, we presented an experiment in which we defined minimum, but not sufficient, luminance contrast ratios for color recognition and legibility for helmet-mounted display (HMD) use. In that experiment, observers made a subjective judgment of their ability to recognize a color by stopping the incremental increase in contrast ratio of a static display. For some target color/background combinations, there were extremely high error rates and in these cases sufficient contrast ratios were not achieved. In the present experiment, we randomly presented one of three target colors on one of five backgrounds. The contrast ratio of the target on the background ranged from 1.025:1 up to 1.3:1 in steps of 0.025 . As before, we found that observers could accurately identify the target colors at very low contrast ratios. In addition, we defined the range in which color recognition and legibility became sufficient ( 3 95% correct). In a second experiment we investigated how well observers did when more than one color appeared in the symbology at one time. This allowed observers to compare target colors against each other on the five backgrounds. We discuss our results in terms of luminance contrast ratio requirements for both color recognition as well as legibility in HMDs.14. SUBJECT TERMS luminance contrast ratio, helmet-mounted display, color recognition, legibility THIS PAGE INTENTIONALLY LEFT BLANK LUMINANCE CONTRAST REQUIREMENTS FOR COLORED SYMBOLS IN HELMET-MOUNTED DISPLAYS INTRODUCTIONThe use of colored symbology in a helmet-mounted display (HMD) has the potential to give the warfighter a significant combat advantage compared to monochrome symbology (2). Unfortunately, it is not as technically easy to employ colored symbology as monochrome symbology in an HMD. Monochrome symbology can be displayed using only one phosphor and relatively high levels of luminance output can be achieved. The use of colored symbology is more complex, and may require tradeoffs in resolution and luminance (3). Since the potential use of colored HMD symbology is still in the developmental stages, it is important to establish the minimum and optimal parameters for its employment. Specific parameters that need to be addressed include luminance, contrast, and hue.In a previous experiment, we presented results from a study aimed at determining the minimum, or sufficient, luminance-contrast ratio for three symbology colors presented against five backgrou...

Increasing interest ui helmet-mounted displays (HMDs) has fueled research in variable transmittancc visors (VTVs) because a VTV can reduce glare and increase HMD contrast in bnghl lighting conditions. The ideal VTV will be an electrically controllable light valve that allows the pilot TO adjust visor muismittance (tut) to the level appropriate to the ambient lighting conditions. Liquid*crystal based devices can provide an efficient method for accomplishing this. Because High! helmets utilize polycarbonate visors« VTVs must be implemented on complex curved, plastic substrates. Liquid crystal devices, however, arc typically implemented on flat glass substrates. We present a novel system. Variable Attenuation Liquid Crystal Device (VALiD), which can be utilized for this application* VALID is a dichroic dye and liquid crystal based guest-host system. Our specific configuration allows for a fast system that fails to the clear state. Furthermore, the degree of polarization dependence can be tailored for use in different applications VALiD has been implemented on thin, flexible, flat plastic substrates Recently, this has been extended to doubly curved polycarbonate substrates and a prototype has been fabricated In this paper we present the characteristics of this technology.

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