The first detecting module 16 and the second detecting module 17 may be two sensors for sensing objects, which are respectively installed in front of and behind the line scan camera 14. Here, the front of the line scan camera 14 is the direction of the line scan camera 14 near the incoming direction of the vehicle, and the rear of the line scan camera 14 is the direction of the line scan camera 14 near the outgoing direction of the vehicle.
The first detecting module 16 and the second detecting module 17 may utilize a photoelectric sensor or a ground sensing coil, or may also utilize other types of sensors such as an ultrasonic sensor, or a visual sensor. According to the detection of the sensor, the vehicle passing over the system for acquiring an image of a chassis of a vehicle may have the following states: 1. the vehicle entering the detection area; and 2. the vehicle leaving the detection area.
When a vehicle enters the detection area, the line scan camera 14 starts capturing images of the chassis of the vehicle; and when the vehicle leaves the detection area, the line scan camera 14 stops the image capturing of the chassis of the vehicle. In the period between the vehicle entering the detection area and the vehicle leaving the detection area, if the speed of the vehicle changes, the control module 13 adjusts the line frequency of the line scan camera in real time according to the changed speed, so that the line scan camera 14 continues to capture images with the adjusted line frequency.