Multifaceted reflector

MR lamps are designated by symbols such as MR16 where the diameter is represented by numerals indicating units of eighths of an inch.

Emmett H. Wiley of General Electric (USA) was awarded patent #3,314,331 for a miniature reflector lamp in 1967.

Most MR lamps consist of a halogen capsule (or, bulb) integrated with a pressed glass reflector with a base conforming to bi-pin GU5.3 standard.

The compact size of the MR base allows for much smaller, more discreet fixtures than the incandescent reflector bulbs that pre-dated MRs.

Others use selective dichroic coating that reflects visible light and allows infrared radiation to pass through.

This type reduces heating of illuminated objects since less infrared radiation is present in the light beam.

[quantify] With both types of incandescent bulbs, useful life can be considerably shortened if their filaments experience mechanical shock or vibration.

Using an electronic transformer with a soft start feature can considerably extend life, as it reduces the characteristically high inrush current that occurs initially when the lamp is cold.

For these two reasons, some MR lamps include a cover glass that serves as an integrated ultraviolet filter and explosion shield.

MR16 lamps lacking this cover require the use of a fixture that incorporates an external piece of glass specifically designed to provide both ultraviolet and physical protection.

There is a wide variety of designs, varying significantly with regard to beam width, light colour, efficiency and luminous power.

Some designs may have simple cut-off apertures that limit beam width, or even individual reflectors or lenses for each LED.

They are typically smaller (transformers excepted), provide better beam control and offer a whiter light than ordinary incandescent lamps.

MR lamps have several disadvantages over other types of lighting, most notably their high operating temperature and the risks of explosion from their pressurized bulb.