Eye safety considerations within ANPR / LPR applications

There are limits to the level of public exposure to infra-red light. It is not possible to get enough light for a camera by using a continuous infra-red light but by pulsing, the average output power is much reduced and the intensity when the camera is on can be increased. Gardasoft provide advice on safe distances for public exposure to infra-red.

High levels of artificial optical radiation can cause damage to both eyes and skin. Exposure limit values have been drawn up for such hazards. Every light system is placed within a Risk Group, which defines the level of risk when the light is used normally.

When the light emits less than the exposure limit values it is categorized as exempt.

The hazard distance is the point furthest from the light at which the exposure limit is exceeded. Generally the hazard distance becomes smaller either as the light power output decreases or the less time one is exposed to the light.

When used to illuminate targets for speed cameras, the risk assessment has taken into account the position of drivers and pedestrians and the likely times that they may be within the light beam. This includes abnormal situation such as cars queuing for long periods due to traffic conditions. For IR models the light output is not visible and thus the aversion response does not automatically protect the eye. The White models will cause the eye to blink, but are not necessarily safer because of the strong spectral peak in the blue.

When installed as detailed in the figure above, there is no risk to the public. If it is necessary to have the light operating whilst being within 0.5m of the lightface, appropriate eye protection should be worn.