Research of night light effects on colorimetric characteristics of image perceived by the pilot in an aircraft cockpit

Abstract

Subject of Research. The influence of radiation spectra from the source of artificial night light on colorimetric characteristics of image perceived by the pilot in the aircraft cockpit has been studied. The image is displayed on the LCD screen of multifunctional color indication equipment unit. Night illumination of the cockpit is performed with the use of artificial lamps of red, green, blue and, rarely, white light. Method. Any given color to be displayed on the screen is perceived by an observer differently with presence and absence of external illumination. When external light of white color is used, perceived color depends upon color temperature of the light source; if illumination source has any arbitrary spectral characteristics, then perceivable color depends upon whole spectral content of the used source. The color, perceived by an observer, is formed as the mixture of the color displayed on the screen (image element color) with the color presented by diffuse reflection of external illumination source from the surface of the screen. The brightness of both colors is added. Mathematical expressions, that define calculation rule for chromaticity coordinates of color perceived by an observer, are based on the Grassmann’s law of additive color mixing. Quantitative analysis of the effect, caused by radiation spectra from an external source of artificial light on color gamut area, corresponding to image, perceived by an observer, has been performed through simulation in MathCad 15.0. Main Results. It was shown, that the color palette of on-board indication equipment, obtained on automated working place for any preset source of external illumination of fluorescent spectrum, corresponding to white light, is not usable correctly in the aircraft night flight mode. An observer loses ability to perceive properly saturated primary colors of red and blue in the case of green-blue light source of external illumination; and the same issue occurs with green and blue for red light source. Using of sources with high illumination level of “warm” white color causes significant shift of the colors perceived by an observer, from the area of saturated blue and green colors in the direction towards the white point defined by illumination source. Using the sources with high illumination level of smooth white color and also with the white color, which white point coordinates coincide with the white point coordinates the color gamut triangle of the tested screen, lead to offset of colors, perceived by an observer, equally for each primary color (red, green, blue) and yellow, cyan and magenta as well. And finally, dealing with sources with high illumination level of “cold” white color, significant offset of colors, perceived by an observer, occurs; those seeming colors are drifting from the area of saturated red and green colors in the direction towards the white point defined by illumination source. Practical Relevance. The results are usable by developers of indication equipment and the manufacturers of LCD panels for colorimetric calculations with account of an influence of external illumination with various spectral content on the screen.v