Halogen Infrared IRK 15005Z with HeLeN Coating
When the original infrared quartz lamps were first trialled in spaceheating applications, one of their principal drawbacks was the unacceptable level of visual glare that accompanied these high power sources. This surprisingly simple situation took several decades to solve, because the lamps ran far too hot to be able to use the traditional lamp filter coatings.

Westinghouse was first to attack this by flamespraying its lamps with orange iron (III) oxide pigment, but this still transmitted a lot of light and absorbed too much infrared. In the early 1980s Thorn invented a Ruby Quartz lamp, but that was very difficult to produce. It was not until the development of the Ruby Jacket lamp, also by Thorn, that the first commercially viable solution was achieved. However those lamps were also expensive to produce, and efforts continued on colouring the inner halogen tube directly.

The next major breakthrough was made by Philips in 1999, with this lamp's 'HeLeN' coating. It consists of a multilayer dichroic interference film applied directly to the quartz, and having excellent thermal resistance. Performance is greatly improved, as the coating's IR transmission is around 10-30% higher than ruby quartz lamps, visible transmission is further reduced, and the emitted light has a less saturated red colour. Coating thickness variations in the vicinity of the evacuation tip-off do allow the escape of a spot of white light, but this is partially alleviated by relocating the tip to the rear side of the lamp. Their only drawback was the high cost due to the extremely slow dip-coating process, which could also lead to colour variations if not well controlled. However the improved output and attractive golden appearance made these lamps an instant sales success.
Manufacturer: Philips
Lamp Power: 2000 Watts
Lamp Voltage: 235 Volts
Lamp Current: 8.51 Amperes
Cap Type: SK15 + Faston Terminals Silicone cables 300mm
Bulb Type: T-10.5 T-3 in eighths/inch
Bulb Finish: HeLeN coating
Filament Type: C-8 Single Coil Axial
Lighted Length: 280mm 11 Inches
Atmosphere: Argon + Bromine
Luminous Flux: 425 lumens
Luminous Efficacy: 0.2 lm/W
Luminous Intensity: N/A
Beam Distribution: N/A
Colour Temperature & CRI: CCT: 2500K (Filament) Ra: 32
Chromaticity Co-ordinates: CCx: 0.503 CCy: 0.307
Lifetime: 7000 hours
Burning Position: Horizontal ± 15°
Overall Length: 357.5mm 141/16 Inches
Factory: Pont-a-Mousson France
Date of Manufacture: 2002 December Date Code: M2
Original Value:
References: 1) Photoelectric measurement.
2) Philips Brochure - HeLeN Infrared Spaceheating Lamps - October 1999, France.
3) Philips Datasheet - HeLeN Infrared Spaceheating Lamps - 2002.