![]() Because the beam is spreading out faster, the power density (irradiance) drops. However, note that in general, the higher the laser power, the higher the divergence. Going from a 5 mW to a 500 mW laser is a 100 times power increase - but the hazard distances only become 10 times as long. If a laser’s power is increased, the hazard distances are longer by the square root of the power increase. Divergence can be improved (made tighter) using a lens or better engineering of the laser itself. Usually, the more powerful a laser, the larger the typical divergence of the laser. Doubling a laser’s divergence will reduce all of these hazard distances by half. The diagrams above depict the NOHD being reduced by half, but this reduction also applies to skin and fire hazard distances, and to the visual interference distances (flashblindness, glare and distraction). Beyond the Nominal Ocular Hazard Distance, the chance of injury is “vanishingly small” according to safety experts. For example, doubling the divergence will reduce the hazard distances by half:Ĭolor indicates the relative hazard: Red = potential injury, green = unlikely injury. If a laser’s divergence (beam spread) is increased, the hazard distances directly decrease. The text has also been reproduced on this page, for ease of reading.įor additional details, see the web pages Laser safety calculations for eye and visual interference hazard distances and Basic principles of laser beam hazards for aviation. ![]() In addition, text below the chart describes how divergence (beam spread), power and wavelength (color) affects these hazard distances. The chart below gives hazard distances for selected consumer laser types, and for various parameters such as the beam color, beam spread and power.
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