A heater for the non-contact heating of an object, such as a substrate for material deposition, includes a housing defining a deposition cavity and a source of radiation outside the deposition cavity. A reflector is optically coupled to the source of radiation to collect the radiation and to focus it on the radiation path. The reflector may have different shapes. If, for example, the reflector is an ellipsoidal reflector, the source of radiation then is mounted in a first focus, the substrate is located in the other focus, and the radiation path is positioned on the main focal axis of the ellipsoidal reflector. The radiation from the source of radiation is delivered to the substrate inside the deposition cavity through a radiation path(s) formed in the housing wall to heat the substrate to the temperature T.sub.s, so that T.sub.1