In this embodiment, the speed of the vehicle may be monitored in real time as to whether it changes. If it is detected that the speed of the vehicle has changed, the method proceeds to step 207. If no change in the speed of the vehicle is detected, the line scan camera continues to perform image capturing on the chassis of the vehicle.

Step 207, determining new line frequency for image capturing.

In this embodiment, the process of determining the new line frequency for image capturing based on the changed speed is similar to the step 102 of the foregoing method embodiment, and is not repeated herein.

Step 208: continuing the image capturing on the chassis of the incoming vehicle.

At step 208, the line scan camera is controlled to continue the image capturing on the chassis of the vehicle.

In this embodiment, if the speed of the vehicle changes, the image capturing on the chassis of the vehicle is continued with the newly determined line frequency. Otherwise, the image capturing for the chassis of the vehicle is continued with the previously determined line frequency.

In this embodiment, after the vehicle enters the detection area, even if the speed of the vehicle changes, the line frequency for the line scan camera can be determined again according to the changed speed, so that the line frequency of the line scan camera always matches the speed of the vehicle. This avoids stretch or compression in part that may occur on images of the chassis of the vehicle captured by the line scan camera.

Step 209: detecting leaving of the incoming vehicle.

At step 209, it is to detect whether the vehicle leaves.