Abstract: A generator of polychromatic light for a projector of a multicolor image, e.g. as used in the testing of a color-television camera, comprises a spherical mixing chamber with three inlet apertures angularly equispaced about an outlet aperture spanned by a transparent test pattern and with a light-diffusing inner wall surface designed to emit a blend of several color components radiated into it from respective sources. A projection objective juxtaposed with the outlet aperture defines with that aperture and with its own entrance pupil a light cone determining a concave illuminating area of circular outline on the chamber wall; the differently colored light beams radiated into the chamber impinge upon limited wall zones offset from this illuminating area in order to homogenize the outgoing polychromatic beam.