Abstract: A microscope illuminator containing an incandescent point source of illumination, an aspheric lens with heat absorbing characteristics defining an optical path for the illumination, a cut-off filter and a rotatable dichroic interference filter capable of being moved into the optical path of the illumination and capable of polarizing light as its angle of incidence with respect to the optical path is varied, a condensing lens and a rotatable mirror for receiving the polarized illumination from the dichroic filter and altering the optical path to coincide with the optical axis of a microscope. Additional filters are optionally provided.