MR16 with Facetted Dichroic Reflector Lamp - ENL

In 1965 the concept of the MR16 dichroic lamp was invented by Emmet Wiley of General Electric. They became very popular in projectors, and later also for display spotlighting.

The original lamps had specular reflectors and it was sometimes found that undesirable images of the filament would be projected in the beam, leading to a non-uniformity of the illuminated area. A solution was proposed in a 1965 patent by Robert Levin of Sylvania, with his invention of the "Peened Reflector". That had small spherical depressions in its surface to introduce a controlled level of diffusion - but it also caused a notable decrease in reflection efficacy, and the glasworking tools were very difficult to produce.

A still more effective solution was invented by Emmet Wiley in 1975, with the concept of what GE called the "Multi-Mirror" reflector. The surface is divided into around 300 keystone-shaped facets, each having a flat surface and therefore being easy to machine. Moreover the sharp angles of the peened reflectors were eliminated, which achieved not only reduced optical diffusion losses for a higher light output, but also less wear and a longer tool life.

The ENL model was one of ten multi-mirror types introduced in 1975. It was originally intended for fibre optic lighting applications, and as such has a longer life than other more highly loaded projection types. Beginning in the early 1980s the multifacetted dichroic lamps became popular among lighting designers because of their elegant and glittering appearance. They experimented with versions like this long-life ENL, and within a few years the MR16 lamp began to transition into general display lighting applications.
Manufacturer: General Electric Co. U.S.A.
Lamp Power: 50 Watts
Lamp Voltage: 12 Volts
Lamp Current: 4.17 Amperes
Cap Type: GX5.3 Nickel Pins
Bulb Type: MR-51 MR-16 in eighths/inch
Bulb Finish: Dichroic Mirror Vycor capsule
Filament Type: C-6 Transverse Coil
Atmosphere: Bromine-Argon
Luminous Flux: N/A
Luminous Efficacy: N/A
Luminous Intensity: candelas
Beam Distribution: 38 mm focal dist.
Colour Temperature & CRI: CCT: 2850K CRI: Ra 99
Chromaticity Co-ordinates: CCx: 0.448 CCy: 0.408
Rated Lifetime: 1500 hours to 50% survival
Burning Position: Universal
Max. Overall Length: 44 mm 1 3/4"
Working Distance: 38 mm 1 1/2"
Factory: Bellevue, OH U.S.A.
Date of Manufacture: 1976 February Date Code: 50
Original Value: US $13.50(1976)
References: 1) GE Photographic Lamp & Equipment Guide P5-61P, 1975 USA.
2) GE Photo-Lamp Catalogue & Price List, 1976 USA.
3) US Patent 3,428,800 - Spotlight Lamp, R.E. Levin & T.M. Lemons, GTE Sylvania, Filed 1965-Dec.
4) US Patent 4,021,659 - Projector Lamp Reflector, E.H. Wiley, General Electric, Filed 1975-Oct.