The Dichroic Filter is also known as the light combiner, half mirror, RGB light combiner, laser beam splitter etc. Dichroic Filters are widely used in projectors, optical instruments, scanning instruments and other fields. The characteristic is that the design wavelength divides the beam into transmitted light and reflected light. It almost completely transmits the light of the transmitted wavelength , and the reflected wavelength of light is almost completely reflective.

Dichroic filters can filter light from a white light source to produce light that is perceived by humans to be highly saturated in color. Such filters are popular in architectural[1] and theatrical applications.

Dichroic reflectors known as cold mirrors are commonly used behind a light source to reflect visible light forward while allowing the invisible infrared light to pass out of the rear of the fixture. Such an arrangement allows intense illumination with less heating of the illuminated object. Many quartz-halogen lamps have an integrated dichroic reflector for this purpose, being originally designed for use in slide projectors to avoid melting the slides, but now widely used for interior home and commercial lighting. This improves whiteness by removing excess red; however, it poses a serious fire hazard if used in recessed or enclosed luminaires by allowing infrared radiation into those luminaires. For these applications non-cool-beam (ALU or Silverback) lamps must be used.