||Following the 1960 introduction by Sylvania and Baush & Lomb of the Super Tru-Flector, the world's first dichroic lamp, these thin-film dielectric filters were put to widespread use on various projector lamps. The preferred embodiment was to apply the coating to an ellipsoidal glass mirror, this being mounted beside the filament and the whole assembly sealed into a tubular outer bulb. Around 1962 Sylvania made a breakthrough by dispensing with the outer bulb and making the coated reflector itself a part of the bulb. This resulted in the Tru-Beam concept, the first of which was this DNF version.
The glass reflector and lens have been formed by the sagging technique, in which a glass disc is heated and allowed to slump into a mould by gravity and with the aid of vacuum suction. The dichroic filter is believed to comprise a 15-layer stack of Zinc Sulphide and Magnesium Fluoride, and a novel feature of this lamp is its 3500K colour temperature thanks to an increased red transmission. A small opening at the rear of the reflector allows the filament, mounted on a conventional flare and stem assembly with exhaust tube, to be sealed into the same. A clear glass lens has been fused to the rim of the reflector to seal the assembly, and enables the atmosphere surrounding the filament to be filled with inert gas.
This design was in production for only a few years until 1965 when the first single ended low voltage halogen capsules began to gain popularity. An improved DNF lamp was then launched, employing a small halogen capsule cemented into the dichroic mirror. This paved the way for GE's subsequent development of the pressed glass MR16 reflector concept into which the halogen capsule could be directly cemented without any requirement for a separate base.