Tri-wavelength blending method for speckle reduction and color space enhancement in laser projection systems

A novel tri-wavelength blending speckle reduction method was proposed and studied both experimentally and theoretically. In the proposed method, a 543 nm diode pumped solid state (DPSS) laser was employed to cooperated with a shorter wavelength 523 nm laser diode (LD) and a common 532 nm DPSS laser. Comparing to the traditional speckle reduction method, the proposed method takes into account both speckle reduction and color space coverage of a project system. It was shown that speckle contrast ratio (SCR) as low as 3.3 % was achieved when the power ratio of 523 nm, 532 nm and 543 nm light were set to 4:1:1. The effect on the color gamut after the use of tri-wavelength blending method was also investigated. It was found that by using the proposed tri-wavelength blending green lasers together with the commercially available red (635 nm) and blue (467 nm) laser diodes, a color space coverage as large as 97.6 % of the Rec.2020 color gamut can be achieved.