Night vision goggle stimulation using LCoS and DLP projection technology, which is better?

Abstract

High fidelity night-vision training has become important for many of the simulation systems being procured today. The end-users of these simulation-training systems prefer using their actual night-vision goggle (NVG) headsets. This requires that the visual display system stimulate the NVGs in a realistic way. Historically NVG stimulation was done with cathode-ray tube (CRT) projectors. However, this technology became obsolete and in recent years training simulators do NVG stimulation with laser, LCoS and DLP projectors. The LCoS and DLP projection technologies have emerged as the preferred approach for the stimulation of NVGs. Both LCoS and DLP technologies have advantages and disadvantages for stimulating NVGs. LCoS projectors can have more than 5-10 times the contrast capability of DLP projectors. The larger the difference between the projected black level and the brightest object in a scene, the better the NVG stimulation effects can be. This is an advantage of LCoS technology, especially when the proper NVG wavelengths are used. Single-chip DLP projectors, even though they have much reduced contrast compared to LCoS projectors, can use LED illuminators in a sequential red-green-blue fashion to create a projected image. It is straightforward to add an extra infrared (NVG wavelength) LED into this sequential chain of LED illumination. The content of this NVG channel can be independent of the visible scene, which allows effects to be added that can compensate for the lack of contrast inherent in a DLP device. This paper will expand on the differences between LCoS and DLP projectors for stimulating NVGs and summarize the benefits of both in night-vision simulation training systems.