Lightstream MR11 Dichroic Reflector - M52 FTB

Following the 1975 invention of the MR16 Multifacetted Reflector lamps by Emett Wiley's of GE in America, Thorn Lighting was one of the first to recognise the potential of these lamps for accent and display spotlighting applications. By 1982 Thorn had launched its Lightstream 50mm range, and became the clear leader of this new market in Europe.

Around 1979 the concept was miniaturised to the smaller MR11 lamps of just 11/8" or 35mm diameter. Their original application is believed to have been for the optical curing of the newly developed white dental filling materials, and Thorn pioneered the development of miniature lamps for a handheld unit that brings brings high intensity light into the mouth via an optical fibre. The company wasted no time in extending the concept to general ligting, and the model featured on this page was one of the first to be introduced, around 1982. They immediately became successful in applications where a tiny and high intensity light source is required, for instance inside glass display cabinets of jewellery stores, as well as integrated into furniture lighting.

In reducing the lamp diameter, it was found that the application of facets to to the reflector caused a much more significant decrease in light output than had been the case for the larger MR16 lamps, due to increased refraction losses at the boundaries of the facets. This problem was solved by the 1980 invention of Thorn's Alex Halberstadt, to leave the pole area of the reflector specular and to facet only the larger diameter areas. This proved to be possible because images of the filament in the beam, which the facets are intended to remove, are primarily caused by the parts of the reflector that are farthest from the filament.
Manufacturer: Thorn EMI
Lamp Power: 20 Watts  
Lamp Voltage: 12 Volts  
Lamp Current: 1.67 Amperes  
Cap Type: GZ4 Glass base
Bulb Type: MR-35 MR-11 in eighths/inch
Bulb Finish: Open Front Dichroic Mirror
Filament Type: C-6 Transverse single coil
Atmosphere: Krypton:Argon Bromine cycle
Luminous Flux: 350 lm (capsule flux)
Luminous Efficacy: 17.5 lm/W (capsule efficacy)
Peak Intensity: 1,760 candelas to half-peak intensity
Beam Distribution: 17.0° to half-peak intensity
Colour Temperature & CRI: CCT: 3000K CRI: Ra 100
Chromaticity Co-ordinates: CCx: 0.452 CCy: 0.409
Rated Lifetime: 2000 hours to 50% survival
Burning Position: Universal  
Overall Length: 35.0 mm 13/8"
Light Centre Length: N/A
Factory: Enfield, London United Kingdom
Date of Manufacture: February 1986 e6b
Original Value: GB £7.29 (1985)
References: 1) Thorn Lighting Comprehensive Catalogue, 1984/85 (UK), p.256
2) Thorn Lighting Price List, 1985 (UK), p.63.
3) Thorn Lighting Micrographic Lamps Catalogue, 1979 (UK).
4) "Dental Technology with Light", G.L. Adams & E.J.G. Beeson, Thorn Lighting Journal No.20 (Spring 1979), pp.24-26
5) "Lightstream for Display", B. Haywood & H.R. King, Thorn Lighting Journal No.27, p.24
6) "Tungsten Halogen Reflector Lamps", R.A. Hume & A.J. Barrell, Proceedings of the UK National Lighting Conference 1986 pp.246-255
7) UK Patent 2,082,745, An Improved Reflector for Electric Projector Reflector Lamps, A.L. Halberstadt, Thorn Lighting, Filed August 1980.