Requirements for mounting and setup of cameras for carriage recognition

The image received from video cameras must be sharp, contrast and readable for the correct recognition of containers license plates.

Requirements for the video camera characteristics:

1. It is recommended to use the resolution of no more than 800x600, because using a resolution of more than 800x600 does not lead to the recognition quality improvement.
2. High resolution black and white cameras are recommended because they provide better quality of image at low light conditions.
3. Recommended frame rate is 25 FPS.
4. The carriage speed must meet the camera operation speed. For a better recognition, it is necessary, and it is enough to have 1-2 frames of a carriage number.
5. It should be possible to set a fixed exposure value (shutter) on a video camera of 1/2000 s or less.
6. The video cameras should have high sensitivity (0.01 lx or more).

Requirements for video camera position:

1. The distance between the video camera and the carriage should be at least 1.5 meters (depends on the focal length of the camera lens), the optimal distance is 5-7 meters.

   Note

   To simplify the setting, it is recommended to use the varifocal lenses. The focal length variation range should be selected in each case of the system installation.

   If you use the camera with an integrated lens with a focal length of 2.8 mm or less, then there may be strong geometric distortions on the image. As a result, the recognition quality may go down. To avoid this, it is necessary to use special removable lenses with an aspherical lens, which eliminate these distortions.

2. The camera height for reading the side number is 3–3.5 meters. The camera height for reading the chassis number is 1.5 meters.
3. The width of the carriage plate number in the image should be about 30-35% of the total image width, in most cases this means the width of the camera control zone is 3-5 meters.
4. The optical axis of video camera should be perpendicular to the plane of carriage plate number.
5. The position of the carriage in the frame should be strictly horizontal.

6. The infrared sensor and the video camera should be located in the same vertical plane.

   Note

   If the analog video camera is used, then to prevent the video signal fading on the transmission line, it is necessary that the distance from the video camera to the digitizing device does not exceed 30 meters.

Image requirements:

1. The minimum character height in the frame should be 16 pixels, 20–50 pixels are recommended. The width of the character line should be at least 2-3 pixels.
   
2. The geometric distortion by optics ("barrels" and "pincushions") should be reduced.
3. The image of the carriage plate numbers should be clear, contrast and readable.

When configuring video cameras, it is also required:

1. Focus camera exactly to the carriage plate number.
2. Disable the AGC mode in video camera.
3. Disable the modes of adding contrast in video camera.

To provide the system operation at night, use the searchlight lighting of carriages/cisterns. Use usual halogen spotlight with a capacity of 1–1.5 kW when mounting spotlight in the distance of 5-7 meters from railway. Locate spotlight as shown in the figure below. Such location allows avoiding the following:

1. Blinding of camera by spotlight directed to it from another side of railway.
2. Image flashing by light reflection from carriage.

Reference image received from the correctly mounted and setup video camera is shown in the following figure.