Prime color light source development for helmet-mounted displays

The subtractive LCD color display used in the helmet mounted display places technically challenging reuqirements upon the color separation optics when used with a light source emitting broadband light spectra. This is because the bands of blue-green wavelengths and yellow wavelengths must be filtered out to provide good color gamut while retaining extremely high brightness in the display. High brightness is required for use in the outdoor environment. In order to improve the overall helmet performance, metal halide arc lamps with spectra tailored to emit prime colors have been developed for Kopin Corporation under a contract from Natick US Army Research and Development Center (funding from ARPA) for delivery to Honeywell. The metal halide lamps are based upon the concept of limiting the radiation of the lamp as much as possible to only ground state based atomic line spectra and selecting the atomic species involved to minimize radiation in the blue-green and yellow wavelengths. The ideal lamp would consist of a single broad line in each of the red, green and blue regions of the spectrum and was well approximated in the actual lamp. In addition, the use of mercury as a component was eliminated because of its emission at 577 nm in the yellow. The final lamp is krypton based AC operated short arc with separate halides added for each of the prime colors.