Laser Phosphor vs RGB laser: How does it work?

The light source in an RGB projector, also called direct laser projectors, contains individual red, green and blue lasers. As we’ve all learned in kindergarten, these primary colors are the building blocks of all other colors. By combining different proportions of these three lasers, the projector can reproduce millions of different shades and hues. The laser output is mixed, processed by the projector’s DMD (Digital Micromirror Device) chips and directed through the lens on the projection canvas.

However, instead of using three different colors, the laser phosphor projectors use just one. The majority go for only blue laser diodes. “Why blue?”, you might ask. Well, the choice for blue lasers is based on the high density and power efficiency of this color. The blue light from the laser shines onto a spinning yellow phosphor wheel. The chemical compound phosphor absorbs the blue light, and radiates a bright, yellow light. This broadband yellow light is captured and split into the primaries using a color wheel. These can then be used to produce the colored images on the canvas.

What are the main differences?

By design, RGB is a wide color gamut light source. RGB projectors can go to the theoretical single bandwidth gamut called Rec. 2020, which is currently the widest color space available.
The RGB pure laser beams are close to monochromatic. It means that these beams are associated with points at the border of the color space diagram. All the colors which lie in the triangle spanned by the corresponding points can be reproduced.

For comparison, the accessible color range for a laser phosphor projector is a triangle with the edges lying inside the diagram (e.g. Rec. 709). But can easily be filterd to increase the colors out to for example DCI/P3 colours.
But don’t forget: if you want your projector to show Rec. 2020 colors, you need content that’s created within the same color gamut. And for now, the production of Rec. 2020 content is still pricier. Movies are mostly maid in DCI/P3 colors and TV shows are usually produced in Rec. 709 colors,