Halomet HTI 400W / 24 Metal Halide Reflector
The HTI Metal Halide lamps were developed as a natural progression from HMI technology, in particular to realise lamps of compact dimensions as alternatives to halogen incandescent products.  The 250W/32 and 400W/24 lamps were primarily intended for professional projection of Super 8 and 16mm cine films respectively, with integrated optics to permit substitution for halogen reflector lamps.  Their daylight output spectrum, hot re-strike capability and long life by comparison with high-performance halogen sources has also led to the widespread adoption of HTI sources in medical endoscopy work, and the illumination of glass optical fibres.

The arc tube filling consists principally of the rare earth holmium, employed in place of the more common dysprosium on account of the very high wall loading in this compact arc tube.  It is augmented by cadmium iodide, while both the iodides and the bromides of lithium and caesium are added in strictly controlled proportions to modify the spectrum and arc dimensions, while also performing the crucial role of limiting devitrification of the quartz wall, and keeping corrosion of the electrodes under control.

The arc tube itself delivers a colour temperature of 4600K with a CRI of 90.  The spectral transmission of the hard SiO2-TiO2 dichroic coating on the reflector modifies this somewhat by transmitting some of the longer wavelenghts, with the net result that the colour temperature of the beam is set at 5600K.  The colour rendering however suffers slightly as a result, falling to a CRI of around 70.  The double ended construction with a short pinch-sealed arc tube enables a lamp of very compact dimensions to be realised, which is capable of being hot-restarted.
Manufacturer: Osram GmbH
Lamp Power: 400 Watts
Lamp Current: 7.3 Amps 300Hz Square-Wave
Lamp Voltage: 55 Volts 25kV Hot-Restrike
Cap: Special Plug
Bulb Finish: Dichroic cold-light mirror
Bulb Type: PDR-67
Overall Length: 73 mm
Focal Distance: 24 mm
Electrodes: Tungsten rods with 4.5mm arc gap
Arctube Atmosphere: Ar | HgBr2, HgI2, CdI2, CsI, CsBr, LiI, LiBr
Luminous Flux (100 hrs): 30,000 lm @ 100 hours (measured with bare arc tube)
Luminous Efficacy (100 hrs): 75 lm/W @ 100 hours (measured with bare arc tube)
Colour Temperature & CRI: CCT: 5600K CRI: Ra 70
Chromaticity Co-ordinates: CCx: CCy:
Burning Position: Horizontal ± 20°
Rated Life: 250 hours to 50% survival
Warm Up / Re-strike Time:
Factory: Eichstätt, Germany
Date of Manufacture: February 1992
Original / Present Value:
 
 
References: 1) Osram Lighting Program Photo/Optics 1992/93.