Functions and Applications of Image Capture Cards Common Terms Related to Image Capture Cards 1. A/D Conversion An image capture card converts analog signals into digital signals, which plays a vital role in image acquisition within the entire machine vision system. This analog-to-digital conversion performed by the image capture card in a machine vision system is known as **A/D conversion**, and the component that implements the conversion is called an ‘’A/D converter‘’. 2. Number of Transmission Channels In industrial production inspection, multiple vision systems often need to operate simultaneously to ensure production efficiency. Therefore, to meet system operation requirements, an image capture card must support A/D conversion for multiple cameras at the same time. The number of transmission channels refers to how many signals a single image capture card can convert concurrently. Commercially available capture cards feature single-channel, dual-channel, four-channel and other optional channel modes. 3. Sampling Frequency Sampling frequency is a key technical parameter of image capture cards for machine vision systems. It indicates the frequency at which the card collects image data and reflects its image processing speed and capability. 4. Frames and Fields A video signal can be progressively sampled through a series of frames, or interlaced-sampled through sequential interlaced fields. In an interlaced video sequence, half of the data for one frame is sampled at each time interval. Features of Image Capture Cards Connected to a PC, an image capture card receives analog video signals from video input ports, samples and quantizes them into digital signals, and then compresses and encodes them into digital video. Most image capture cards support hardware compression. When capturing video signals, they compress the video onboard first, then transmit the compressed video data to the host computer via a PCI interface. Accordingly, the key to real-time acquisition lies in the processing time required for each frame. If the processing time of one frame exceeds the interval between two adjacent frames, data loss, namely ‘’frame dropping‘’, will occur. Capture cards compress acquired video sequences before storing them on hard drives. In other words, video acquisition and compression are completed synchronously, eliminating the need for secondary compression.