Documentation for Auto Intellect 5.0. Documentation for other versions of Intellect is [available too].

The following video camera requirements should be met in order to ensure the recognition of license plate numbers using the Auto-Intellect system.

№

Property

Range

Comment

1

Camera type

CCTV

Analog and IP-cameras can be in use.

2

Camera resolution

Not less than 520 TVL horizontally.

Only high resolution CCTV camera usage guarantees the recognition rate declared in the technical characteristics of the system.

3

Illuminance of the monitored area

Not less than 50 lux for cameras with 0.05 lux CCD sensitivity;
Not less than 20 lux for cameras with 0.0002 lux CCD sensitivity;
0 lux for cameras with IR illumination.

At night time, standard auto road illumination devices are sufficient to provide 50 lux illuminance in full compliance with the building regulations.

4

Automatic amplification adjustment

LOW or MIDDLE depending on the camera

This function must be enabled. Unfortunately, the scene is usually not sufficiently illuminated, thus the image looks too dark in case this function is disabled. Enabling this function amplifies the whole video signal including the CCD noise. The amplification value is chosen for each camera separately.

5

Auto aperture and auto electronic shutter

  • not more than 1/500 sec for vehicle speed below 40 km/h;
  • not more than 1/1000 sec for fast motions (vehicle speed above 40 km/h).

The image should be sharp. Sharpness can be achieved by locking the shutter speed (exposure). Locking the speed of the electronic shutter is a very important function.
When the exposure is long, i.e. the shutter speed is low (1/100, 1/50 sec), the moving objects are blurred in the image. This most affects the small details, eg. the symbols in license plate numbers. The video sequence as a whole may look good enough, but the static frames that comprise it may be blurred, making LP number recognition partially or completely impossible. If the video camera is not forced to operate at high shutter speed, it will automatically switch to long exposure in case of poor lighting conditions, preventing plates recognition. With the same settings, the video camera can recognize the numbers in bright light only, automatically switching to short exposure.
If the video camera is installed at an angle more than 10 degrees to perpendicular to the license plate, we recommend to halve the shutter speed.

6

Color

Black and white image

It is recommended to use black and white cameras unless it is necessary to store color pictures of the vehicle. This is because clolr cameras while having same characteristics have less sensitivity and pictures appear less sharp.

7

Video stream speed (fps)

Slow mode – 3 fps.
Fast mode – 25 fps.

For proper recognition, the plate is to be fully observed and read at least in one frame. For getting the car direction, the plate is to be fully observed and read at least in two frames. The maximum speed of vehicles moving in the control zone is defined for each object and depends on the way of camera installation, what objective is in use, etc. In some frames the plate can be light-struck/darkened/covered depending on the traffic situation, the time of day, etc. To avoid such problems, it is necessary to increase the number of frames in which the plate is observed. It is achieved by the video stream speed-up or decreasing of maximum allowed speed of a car.


For recognition it is necessary to make sure that frames with number plates fulfill the following characteristics:

  • license plate number should be fully placed in the frame;
  • height of the symbols is not less than 15 px, width is not less than 2px;
  • symbols should be sharp, not smeared, undistorted, not overexposed, evenly lighted;
  • symbols should be visually differentiated;
  • technical requirements for the number plates should follow according government standards;
  • minimum allowed contrast with evenly dirty number plate should not be less than 10% ) contrast differentiation of symbols to the background is 25 on 256 point scale);
  • maximum allowed uneven dirtiness is not more than 12% (ratio of the dirty area of the number plate to its whole area);
  • geometrical proportions of the number plate picture should not differ from such proportions of the number plate itself with more than 10%;
  • without the effect of interlacing (on speed) for analog cameras.