Useful Information
- ♦ Application
- ♦ Cameras
- ♦ Lenses
- ♦ Light & CCTV
- ♦ Number Plate Recognition
- ♦ Thermal Imaging
- ♦ Housings
- ♦ Digital Images
- ♦ Digital Technology & Recording
- ♦ Video Compression
- ♦ Infrared
- ♦ IR & LED Lighting
- ♦ IP CCTV & Technology
- ♦ Monitors
- ♦ Motion Detection
- ♦ Multiplexers
- ♦ PIR Movement Sensor
- ♦ Remote Positioning Devices
- ♦ Video Motion Detection
- ♦ Multiple Screen Display
- ♦ Signal Noise Ratio
- ♦ Survellance Vechicle
- ♦ Three-dimensional (3D) design in CCTV & Security
- ♦ Transmission of Video Signals by Cable
- ♦ Transmission of Video Signals by Remote Methods
- ♦ Transmission of Video Signals by Fibre Optics
- ♦ Video Analysis
- ♦ Wireless CCTV
Number Plate Recognition
Automatic Number Plate Recognition (ANPR) is probably the next growth product to take off in the UK,(and the world) in fact, it is already beginning to be the biggest potential earner for installation companies. Network systems were all the hype in recent years but have not really grown as the pundits originally predicted. One problem is that it crosses technological barriers and the needs of available bandwidth were conveniently obscured.
On the other hand ANPR technology is completely within the scope of knowledge of CCTV companies, although there are a few new terms and technologies to come to grips with. As with previous new developments there is plenty of scope for the industry to deliver more hype and misinformation. There are pitfalls for the unwary and this and future articles will aim to explain some of these for the customer and installer (or, systems integrator).
We are grateful for assistance in producing this article to CitySync for the APR system and Derwent CCTV for information on infrared illumination.
We will start by considering ANPR for a single lane using a dedicated camera and go on to discuss some other applications such as multi-lane systems and Town Centre systems with colour cameras.
Vehicle Speed and Capture Rate
Another very important consideration is the speed of the vehicles to be monitored and the width of the area to be covered. There are again two important interrelated elements connected with vehicle speed. One is the rate of the image grabber software the other is the speed of the processor. With modern processors the latter can no be ignored.
Consider a vehicle travelling at 30 MPH, this equates to 13.4 Metres in one second. A UK camera produces 50 fields per second and the shutter speed is usually 1/50th second. In 1/50th second the vehicle would travel 0.27 Metres (268mm). This would cause a blurred image and problems with the OCR translation.
For this reason the shutter speed should be set to 1/1000th second, in which case the vehicle would travel only 0.013 Metres (13.4mm). The same reasoning applies when trying to capture moving images with a 35mm camera. This is slightly less important when looking head on at a vehicle but becomes increasingly important when the vehicle is at an angle approaching the camera.