Importance

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Abstract

An infra-red measurement radiometer is disclosed having one or more laser emitters (10) to define a sighting area, characterised in that the brightness of the laser beams (24) emitted is controllable by the operator. Brightness of the laser beams can be increased or decreased to a useful extent by switching more or less lasers into or out of operations. Brightness can be reduced by optical attenuation, such as the interposition of an optical element between the laser and the target, such as a diffraction lens or an iris device, or by use of an optical brightness filter, as in photography. It is also possible to change the laser beam brightness by variation of the electrical power supply (V.sub.s) to the laser emitter (10). This can be done with a resistor circuit (12), which may be fixed, or variable, and which may be located electrically between the laser emitter and power source, which is commonly a DC dry cell battery. In accordance with the invention, the operator of an instrument is able to adjust the laser brightness, within safety limits, which allow enough brightness to be both safe and useful. When the target measurement or treatment area is located at a relatively long distance away from the instrument, or in obscure illumination conditions, greater laser brightness becomes valuable.

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First Claim