Laser Wavelength Choices for Pico-Projector Applications

The rapid progress in laser light source development, particularly in the gallium-nitride material system, means that a wide range of wavelengths are now available for pico-projection applications intended to deliver 20 lm or less. In principle, this affords designers of pico-projection systems great flexibility in choosing laser wavelengths to optimize specific performance metrics. With the proliferation of laser-based pico-projectors, however, it has become clear that current laser safety regulations and their wavelength-dependent classification criteria play a fundamental role in determining the brightness roadmaps of scanned-beam and liquid crystal on silicon (LCoS) pico-projection systems. In this paper, it is shown that it is possible to choose laser wavelengths to simultaneously maximize eye-safe luminous flux and color gamut, but that the resultant values are significantly different for Class 2 and Class 1 eye-safe projection systems.