Enhancing efficacy in laser projection by four wavelength combination

•Combination of four laser wavelengths for maximizing both color gamut and efficacy.•We report a method that permits to calculate the best combination.•Best combination can only be achieved by adding a fourth laser wavelength.•Maximal efficacy is obtained at certain combination of laser power and wavelengths.•Results represent a guideline for the future development of picoprojectors.

In this paper we present a novel study about the combination of four laser wavelengths in order to maximize both color gamut and efficacy to produce the color white. Firstly, an analytic method to calculate efficacy as a function of both four laser wavelengths and four laser powers is derived. Secondly, we provide a new way to present the results by providing the diagram efficacy vs. color gamut area that summarizes the performance of any wavelength combination for projection purposes. The results indicate that the maximal efficacy for the D65 white is only achievable by using a suitable combination of both laser power ratios and wavelengths.