A Recipe for a 4+ Primaries DLP Projector

Human eyes sense light using five distinct receptor types: long, medium and short-wavelength cones; rods; and intrinsically photosensitive retinal ganglion cells (iPRGCs). The sensitivity distributions of these five receptors overlap substantially. To study their relative contribution to visual perception, it is necessary to develop specialized displays that can selectively isolate each receptor type. Here, we describe one such display, the PROPixx Multispectral DLP projector by VPixx Technologies. The PROPixx Multispectral is designed with red, green, blue and yellow LED primaries. We present technical details of this projection system, outline engineering challenges associated with building its light engine, and describe the spectral power distributions of each light source. The use of four primaries facilitates the method of silent substitution, an experimental paradigm in which light pairs are used to selectively modulate individual receptor types, while maintaining an identical level of activity in the others, thus “silencing” them. We discuss this technology's potential to advance vision research and briefly discuss how adding additional primary light sources (e.g., cyan, ultraviolet) can unlock additional advanced vision research paradigms.