CCTV or ANPR Camera?
ANPR software works by examining video frames at high speed looking for shapes and patterns that resemble rectangular areas containing text – i.e. number plates. The actual letters and numbers that make up the plate are then extracted from that part of the image.ANPR software may work with standard CCTV cameras for stationary vehicles – and if the shutter speed is set to 1/1000th sec. it can capture plates on fast moving vehicles in bright or controlled lighting conditions. However in darker conditions, approaching vehicles headlights will dazzle the camera and the camera will compensate by closing the iris down preventing a plate read. Fixed aperture cameras will fail by over or under exposing the plate.
A specialised ANPR number plate capture camera such as the RoadWolf™ uses longer wavelength Infrared light (below the visible part of the spectrum) to overcome these problems for retro-reflective plates.
Most number plates around the world are now retro-reflective which means that provided a suitable light source is positioned adjacent to the camera lens, then a plate at virtually any angle will reflect back nearly all of the light. RoadWolf™ ANPR cameras use a combination of filtered infra-red light, filtered CCD sensors to precise wavelengths, electronic shuttering techniques and anti-smear and anti-bloom circuitry to remove flare from headlights and reflected sunlight.
The resulting images provide crisp, clear number plates for the Recognition Engine to interpret the plate whatever the ambient lighting conditions and whatever the speed of the vehicle.