• license plate, number plate, us license plate, british number plate
LPR, ANPR, ALPR, ocr, car plate recognition, vehicle identification


Friday, 18 January 2019 12:09

How do you find your way in the jungle of technical jargon? Each field of expertise has its own terminology. Tech companies use a specialized lingo full of abbreviations and expressions common within the industry, yet hard to grasp for non-experts. Sometimes, manufacturers require the services of a Plain Language Consultant to make their messages simpler and easier to understand. Capitalizing on our industry experience of over 28 years, we would like to enable readers of this article to get familiar with the terms and abbreviations used in Automated Number Plate Recognition (ANPR). Note that this article was written for those needing simple explanations of industry terms.

What’s ANPR?

Automatic – or automated – number plate recognition (ANPR) has many practical applications, such as automatic toll collection, traffic law enforcement, parking lot access control, and road traffic monitoring. ANPR is also known as automatic vehicle identification, car plate recognition, and optical character recognition (OCR) for cars.

In the first part, you can find out more about photography terms used in number plate recognition, in the second part you can read about and transportation terms used in ANPR, and finally, in the third part of the article you will learn about UK vs US English spelling and terminology as well as how companies use product names to communicate with their business partners.

Photography terms in ANPR

ANPR is based on imaging, so there’s a great deal of photography jargon to begin with. Photography terms appear in the context of purpose-built ANPR cameras. These cameras were designed to take images that are ideal for plate recognition. Their priorities:

  • ANPR-optimized images are different from conventional photography. The photo shutter speed is of key importance.
    Blur-free imagingsharp images with clear contours
    is guaranteed by incredibly fast
    shutter speedoptimized for ANPR it can be as short as 1/20,000 second
    – to capture the plate of vehicles travelling at a speed of 150 mph or more.
Fast shutter speed means short exposure time and blur-free images for ANPR
Optimal vs too slow shutter speed imaging for ANPR
  • Shadow-free and glare-free images are guaranteed by the integrated IR light component – to eliminate
    overexposuretoo much light causing burnt-out images
    and to get rid of shadows.
  • Little or no
    distortionmodified shapes and proportions
    of characters, like slant and slope letters and numbers. Note that dedicated OCR software is capable of overcoming the slant/slope of characters captured by cameras deployed at severe angles.
  • As little distortion as possible, by careful choice of camera shutter: global shutter is the type of camera shutter generally considered as best for when photographing moving objects. A global shutter captures the entire image frame at once.
Global shutter imaging helps minimize image distortion in ANPR
Global shutter vs rolling shutter imaging for ANPR
  • Bright and
    high contrast imagesletters and numbers are very different from background
    even in low visibility conditions thanks to
    large aperture, also called iris, simply put, the size of the light hole of the camera, the opening through which light enters the camera
    sensitive sensor and smart

    Steady operation both in bright light and in darkness, thanks to the camera’s day/night filter.
Smart illumination and day/night filters help optimize images for ANPR
Optimal vs. overexposed imaging for ANPR
  • Image
    resolutionmeasured in megapixels
    that is ideal for plate recognition – detailed enough to show the characters in the plate, yet not too many pixels in order to facilitate fast image processing.
  • Frame per second must be carefully selected to match the expected vehicle speed – this is how you can guarantee that there are at least three image frames where the vehicle plate is clearly visible.

Angle of view and focus also play a crucial part in imaging: setting up your recognition camera properly is just as important as buying a purpose-built model camera.

In the second part of the article you can read about transportation terms in ANPR.