Better images for ANPR capture

New technology to optimise the results of Automatic Number Plate Recognition (ANPR), in bright sunlight and at night, has been released.

Jan 25, 2007
By David Howell
L-R: PC Joe Swan, Sgt Thomas Neilson and Sgt Chris Smith

New technology to optimise the results of Automatic Number Plate Recognition (ANPR), in bright sunlight and at night, has been released.

The Cobra Automatic Number Plate Recognition Image Capture system has been designed to read vehicle number plates day and night, in the most demanding conditions.

The system, produced by Appian Technology, can be supplied with a range of different internal camera and IR (Infrared) illumination options for ANPR application including mobile, fixed and long range ANPR.

It uses high-resolution optical zoom cameras, both for ANPR and high definition overview/ contextual imaging.

Zoom functionality means the system can be rapidly optimised to suit differing plate and environmental conditions at ANPR capture points. It can be easily moved from one location to another and the settings simply adjusted – avoiding the need for time consuming, risky and costly relensing.

Globally, number plates have widely differing characteristics and contrasts. To overcome this problem, the Cobra has a choice of IR wavelengths available – 810,870 and 940NM. The zoom enables the cameras field of view to be optimised to local plate sizes.

Additionally, the user can adjust both IR pulse duration and illumination power. In its long range dual illuminator configuration the camera has a range of up to 45 metres (subject to wavelength).

The camera is compact and lightweight and suitable for both mobile and fixed applications, with a flexible range of camera modules and illumination options.

It is easy to use and maintain and has a high environmental specification.

Obtaining high confidence recognition results in bright sunlight, when plate characters are partly shaded is a significant challenge.

At night the effect of bright headlights needs to be suppressed to improve the accuracy of recognition.

The Cobra has a number of features designed to combat these problems, including improved processing gain and narrow band IR filtering.

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