<title>Luminance contrast requirements for colored symbols in helmet-mounted displays</title>

Abstract

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Effects of saturation contrast on color recognition in night vision goggles

“…More recently, display technology has allowed for symbology to be viewed superimposed in front of the intensifier tube, thus allowing for color coding of symbology, the benefits of which have been shown elsewere 2 . However, this configuration gives rise to a problem similar to one studied previously in our laboratory, in the context of color helmetmounted displays (HMDs), in which the outside scene mixes with the symbology causing the hue and saturation of the symbol to shift and thus cause errors in color recognition 3,4 .…”

“…These mixtures were calculated to produce the following luminance contrast ratios given a 7 cd/m 2 background: 1.025, 1.05, 1.1, 1.2, 1.4, 1.6, 1.8, and 2:1. This range was used so that we could fit Weibull functions as we did previously 4,8 and thus calculate 95% correct luminance contrast ratios. The color coordinates of the stimuli (pre-color mixture) were chosen such that they could be replicated by anyone who may not have access to a colorimeter.…”

“…The color coordinates of the stimuli (pre-color mixture) were chosen such that they could be replicated by anyone who may not have access to a colorimeter. To do this we relied on previous research 3,4,8,9,10,11,12 which has shown that, in general, colors along the gamut of a display device are chosen most often to be representative of that color. For example, full input of the green gun with the red and blue guns off gives the top left corner of the gamut and is most always called green.…”

“…This was done to assure that the symbology color mixtures were within tolerances each day. The stimulus for the experiment was a representative HMD target designator (TD) box used previously 3,4,8 and is shown in Figure 1. …”

Daylight luminance requirements for full-color, see-through, helmet-mounted display systems

“…Although luminance and contrast requirements for the legibility of white symbology have been and are a continuing topic of investigation, such requirements for color symbology in HMDs have not been pursued as vigorously. [15][16][17] Metrics defining color contrast (and hence luminance) are more complicated than those presented previously where the contrast refers only to differences in luminance. Color contrast metrics must include differences in chromaticity as well as luminance.…”