What is the principle of electronic eye capture without seat belt?

What is the principle of "electronic eye capture without seat belt"? Introduce the following related contents:

The principle of electronic eye capture without seat belt is as follows:

1, illegal photo. You can shoot the electronic eye of the seat belt, the mobile phone photography on the road and the oncoming police speed measurement. Some need manpower, but I heard that there are already smart cameras. At present, drivers who fail to use seat belts according to traffic regulations when driving on expressways or urban expressways will be fined 200 yuan, with 2 points recorded;

2. When driving on roads other than expressways and urban expressways, if the driver fails to use the seat belt as required, he shall be fined from 20 yuan to 50 yuan;

3. If the passenger fails to use the seat belt when the motor vehicle is running, he will be fined in 5 yuan ~ 10 yuan. Please fasten your seat belt for your safe travel.