A typical machine vision system includes the following five blocks: lighting, lenses, high-speed cameras, frame grabbers, and vision processors. The frame grabber is just a component of a complete machine vision system, but it plays a very important role.
The frame grabber is also called a video capture card. It can be used to obtain digital video information and store and play it. Many video capture cards can obtain audio while capturing video information, so that the audio and video parts are saved and played simultaneously when they are digitized.
The interface from the video signal source and the image acquisition card can be divided into: analog acquisition card and digital acquisition card. The analog capture card collects analog video signals into the PC through the AV or S terminal, so that the analog signals are converted into digital signals. The video signal source can come from analog cameras, TV signals, analog video recorders, etc.
The digital capture card digitally captures the digital video signal into the PC in a digital-to-digital format. Its video signal source is mainly from DV (digital video camera) and other digital equipment.
An important difference between analog capture cards and digital capture cards is that with digital capture cards, there is no loss of video signals during the capture process, which can guarantee the same results as the original video source, while using analog capture cards will have a certain degree of video signals. Loss.
In simple terms, we can make an analogy: analog capture is similar to using a video recorder to rip a video tape. The ripping subband is always not as clear as the master tape. If you use the subband to rip again, the effect will be worse. Digital collection is like using a computer The data files are copied, no matter how many times they are copied, the copied files are exactly the same as the original files, without any difference. Two-in-one capture card refers to digital analog capture card, AV + DV capture card. Digital input and output, analog interface input (DV / AV / S-video), full interface board.
If the high-speed camera and industrial computer are the eyes and brain of the machine vision system, then the frame grabber is the heart of the machine vision system. It must accurately accept the video data of various specifications of the front-end camera, receive external trigger pulses, and start the exposure and scanning of the camera, playing an important role in the system.