Cold light mirror lamp
Dichroic lamps (also Coolbeam ) are halogen - incandescent lamps comprising a dichroic reflector possess the light, therefore a reduced infrared has stake. The heat radiation in the light of the lamp is therefore low, hence the name. In addition, this technology has a positive effect on color rendering .
The reflector of a cold light mirror lamp consists of an interference layer system that reflects visible light very well, but allows infrared to pass (in contrast to other reflector light bulbs). A large part of the released heat is therefore not reflected, but given off to the rear and heats the lamp . This heat radiation emitted to the rear is greater than with other reflector lamps and can lead to overheating. Cold-light mirror lamps can therefore often not be used in luminaires that are poorly cooled due to their design or where they are used; this applies in particular to recessed luminaires. The warning symbol according to IEC 60598 indicates this danger.
Properties of the reflector
The reflector of cold light mirror lamps is made of pressed glass and is covered with several dielectric layers with changing refractive indices before the incandescent lamp is installed. The wavelength-dependent reflection can be controlled through the layer sequence and the layer thickness .
The mirror shape is more or less approximated to a paraboloid of revolution by means of small surface elements . The beam angle often stated on the packaging (values from 10 to 35 ° are common) describes this approximation.
With cold-light mirror lamps, the reflector is an integral part of the light source and is lost if it fails. However, there are also slide and amateur film projectors with cold light mirrors, in which the interference mirror is separate from the lamp. There its shape is a smooth spherical cap . He can make the use of a heat protection filter superfluous.
See also
- Cold light source , use of this principle for special, technical or medical applications