Abstract: An improved apparatus (11) for emitting infrared radiation of a desired wavelength includes a primary surface (.[.35.]. .Iadd.25.Iaddend.); a burner (24) for raising the temperature of the primary surface so as to cause the primary surface to emit infrared radiation of a first wavelength; a secondary surface (26) surrounding the primary surface in spaced relation thereto and arranged to be heated by infrared radiation emitted by the first surface and for emitting infrared radiation of a second wavelength toward the object; and an actuator (28) for selectively varying the spacing between the primary and secondary surfaces so that infrared radiation emitted by the secondary surface .[.will be at a desired wavelength and.]. will be focused; whereby the apparatus will emit infrared radiation of a desired wavelength toward the object.