Machine vision technology is currently an application in the fields of industrial production inspection and medical testing to achieve automation and intelligence. The whole machine vision system is divided into two parts: image acquisition and image processing, and the image acquisition card is an important component connecting these two sections in the image acquisition system that simulates the industrial camera.
Because the image acquisition part of the machine vision system is mainly composed of LED light source, industrial lens and industrial camera, and the image processing part is realized by image processing software, therefore, in the principle structure, the image acquisition card is connected with the industrial camera and the image processing software.
Here are some concepts commonly used with frame grabbers:
1. A/D conversion
The frame grabber can realize the conversion of analog signals to digital signals, which plays an important role in the image acquisition of the entire machine vision system. The analog-to-digital conversion of the frame grabber of the machine vision system is called A/D conversion, and the corresponding components that realize the conversion are called A/D converters.
2. Number of transmission channels
In the process of industrial production inspection, it is sometimes necessary for multiple vision systems to operate at the same time to ensure a certain production efficiency. Therefore, in order to meet the needs of the system operation, the frame grabber needs to A/D convert several cameras at the same time. The number of transmission channels refers to the number of simultaneous conversion of the same image capture card, and the optional transmission channels of the acquisition card developed and produced on the market are single channel, dual channel, and four channel.
3. Sampling frequency
Sampling frequency is one of the main technical indicators of the frame grabber of the machine vision system, which refers to the frequency of the frame grabber when collecting image information, reflecting the speed and ability of the frame grabber to process images.
4. Frames and fields
A video signal can be sampled progressively over a series of frames, or by interlaced fields for a sequence of interlaced video sequences, where half of the data of a frame is sampled at each time sampling interval.
Frame grabber features:
The analog video signal from the video input can be received on the PC through the frame grabber, the signal is collected, quantized into a digital signal, and then compressed and encoded into a digital video.
Most frame grabbers have the function of hardware compression, which first compresses the video signal on the card when acquiring the video signal, and then transmits the compressed video data to the host computer through the PCI interface.
Therefore, the key to real-time acquisition is the processing time required for each frame. If the processing time of each frame of video image exceeds the time between two adjacent frames, data loss, i.e., frame loss, will occur.
The capture card compresses the obtained video sequence first, and then stores it on the hard disk, which means that the acquisition and compression of the video sequence are completed together, eliminating the inconvenience of compressing again.
Article source: New Machine Vision
Disclaimer: The purpose of reprinting this article is to convey more information, and it is only for the purpose of readers to learn and Xi communicate. The copyright of the article belongs to the original author, if there is any infringement, please contact to delete.