A dichroic coating reflects one band of colour and lets the rest through. Two such prisms with a glass spacer make a trichroic block: blue peels off first, red next, green goes straight. That is the RGB split inside a 3CCD camera — not the dispersion of a Newton prism.
Philips patented this colour-separating prism in 1972 for three-tube television cameras; later 3CCD camcorders put a sensor on each exit face. This bench is the same idea in the open: white in, three coloured beams out onto three screens.
