ANPR in details

ANPR working prinicple

  • Control spot has a camera that takes a shot of the vehicle (1)

  • The picture is digitalised and using VIS software the licence plate is recognized (2)

  • The licence plate is checked in the database (3)

  • After the checking the entry into the database, the entry is archieved in the database (4)

  • A requested operation is preformed (for example: the barrier opens, if a vehicle is entered into the database) (5)

The process of ANPR recognition

1. Taking a picture

When a trigger event is detected (vehicle detected on the inductive loop or signal from the doppler or laser trigger device), a computer takes a snapshot of the current camera view. Picture is saved and sent to the ANPR engine application.

2. Optimizing the picture

The ANPR software uses its own algorythms for optimizing the picture in order to get best picture for OCR purposes. Contrast, brightness, gamma etc. can be changed in order to get optimal picture for further processing.

3. Searching for a licence plate

In the first step of ANPR recognition process, the software is checking the picture, if there is a licence plate present anywhere in the picture. If no licence plate is found, the picture is canceled for further steps, otherwise the (possible) licence plate location(s) are send to the next step engine.

4. Checking licence plate candidates, ASCII characters reading

When more licence plate candidates are found on a single picture, the program checks each of them and decides, which candidat is most likely the licence plate which we are looking for. When only 1 licence plate is defined, an OCR engine is started, which reads out the characters from the licence plate. If there is more possibilities for one character (for example I and 1, 8 and B ...), the program uses fuzzy logic and self-learning neural network to decide, which character is the correct one.

5. Completing ANPR process

All data (original picture, ASCII readout) are "packed" back into one stream and sent to the higher-level program, which then decides what to do (for example: checking the entry into the database ...).