Image Acquisition Card Image Acquisition card, its function is to collect the image signal to the computer, in the form of data files saved on the hard disk. It is an essential hardware device for image processing, which allows us to transfer video signals from the camera to the computer.Interpreting the meaningThe Image Acquisition card is the interface of the image acquisition part and the image processing part. Images are sampled, quantified, converted to digital images and entered, stored in the frame memory, called acquisition. The image grabber also provides the function of digital I/O.Technical Data
(1) Image Transmission format is the most important parameter of video editing, the image acquisition card needs to support the output signal format adopted by the camera in the system. Most cameras use RS422 or EIA644 (LVDS) as the output signal format. In digital camera, ieee1394,usb2.0 and Cameralink are widely used in several image transmission forms. (2) Image format
Black and white images: Typically, the grayscale level of an image can be divided into 256 levels, which is expressed as 8 bits. When the grayscale of the image has more precise requirements, it can be represented by 10-bit, 12-bit, etc. Color Image: Color image can be composed of RGB (YUV) 3 colors, according to its brightness level of different 8-8-8,10-10-10 and other formats. (3) Number of transmission channels when a high-resolution image is taken at a higher rate, a high output rate is generated, which generally requires simultaneous output of multiple signals, and the image capture card should be able to support multiple inputs. In general, there are 1-way, 2-way, 4-way, 8-way input and so on. With the development of technology and the continuous demand of the industry, more and more of the acquisition card is also appearing on the market. (4) The maximum number of dots supported by the resolution capture card reflects the performance of its resolution. The general acquisition card can support 768*576 lattice, and the performance of the acquisition khaki support the largest lattice can reach 64k*64k. Single-line maximum and single-frame maximum lines also reflect the resolution performance of the capture card. The same three-dimensional acquisition card can achieve 1920x1080 resolution. (5) sampling frequency sampling frequency reflects the acquisition card processing image speed and ability. In the high image acquisition, it is necessary to pay attention to whether the sampling frequency of the acquisition card satisfies the requirement. High-grade collection khaki sampling frequency up to 65MHZ. (6) The transmission rate of the mainstream image acquisition card and motherboard are PCI interface, the theoretical transmission speed of 132mb/s.principle
Acquisition, video/image sampling, quantization after the conversion of digital images and input, stored in the frame memory process. Because the transmission of image signal needs very high transmission speed, the universal transmission interface can not meet the requirements, so the image acquisition card is required. 1, the field of view (FOV) or the scene is the camera and optical system "see" to the real world specific parts. 2. The CCD chip converts light energy into electric energy. 3. The camera outputs this information to the image capture card in the format of the analog signal. 4. The ad – Converter converts the analog signal into a 8-bit (or multi-bit) digital signal. Each pixel independently expresses the intensity of the light in the form of a grayscale value (gray level). 5, these light intensity values from the CCD chip matrix is stored in the memory of the matrix data structure.Calculation FormulaFrame image size (image size): WxH (length x width) color depth: D (number of bits)---desired Image color (8Bit grayscale image or 16/24/32bit true color) frame rate: F---Standard PAL system is 25 frames. Data volume: Q (MB) sample rate: A (MB)
Calculation formula: Q=WXHXFXD/8 Judgment Standard: If a>qx1.2, then the acquisition card can be competent to collect work.
A typical vision system--Image Capture card + computer + input/output + control mechanism
