Triggering topologies for camera and illuminators within ANPR / LPR applications

The figure below illustrates some typical camera triggering topologies. Looking from left to right, topology 1 shows the traditional triggering arrangement whereby the camera is triggered by a vehicle sensor, the camera then triggers the light and starts its exposure. Topology 2 shows the light being triggered by the sensor. The light then triggers the camera. This has the advantage that the light can filter the trigger signal, addressing situations where for example one vehicle causes multiple triggers or short noise spikes cause false triggers, in effect, the light ‘cleans up’ the trigger signal. Topology 3 shows an increasingly popular arrangement where the camera is continuously taking images and the camera’s on-board software looks for vehicles in view. There is no external trigger and the light provides a regular trigger to the camera. Alternatively, the camera continually triggers the light.

The number of pulses and the distance between them is very application-specific, and is another area where Gardasoft can provide advice and testing expertise as well as a very fast delivery of suitable products.