These lamps are now standard equipment on most microscopes manufactured in Japan, the United States, and Western Europe. Tungsten-halogen lamps have compact bulbs that introduce a number of advantages over normal incandescent lamps, most notably their brilliant light, smaller dimension, uniformity of illumination, longer lamp life and greater economy. Tungsten-halogen lamps operate at very high temperatures and may cause serious burn injuries if handled while hot. When replacing these lamps, always allow them to cool for at least 20 minutes before removing them from the lamphouse. Avoid handing the bulb envelope directly because fingerprints left on the envelope will become burned into the glass, often initiating premature lamp failure.
Manufacturers package tungsten-halogen lamps in protective plastic bags to avoid handling problems.
Use a pair of scissors to cut the bag near the tungsten pins and insert the lamp into its holder while it still remains in the bag. Remove the bag when the lamp is properly positioned in the lamphouse. The base is a two-pin style with tungsten lead wires fused to the borosilicate glass envelope. The reflector aids in directing the light by allowing most of the infrared radiation generated by these bulbs to pass through the dichroic mirror reflector housing, while reflecting the shorter visible and near-ultraviolet wavelengths. These lamps operate at 6 to 21 volts DC and are usually placed in a lamphouse that provides for control of the operating voltage as well as removal of excess heat through cooling fans.