The video capture card is one of the components of the machine vision system. It is the interface between the image acquisition part and the processing part, and it is the intermediate unit module that completes the image acquisition from the camera to the computer storage and processing. The video capture card has many parameter characteristics. Different parameters and performance directly determine the effect of video acquisition and display.
The factors affecting the acquisition quality of the video capture card mainly include the following aspects:
• Sampling accuracy:
The bit depth of the AD converter (such as 8bit, 10bit, 12bit, etc.) determines the accuracy of the video signal after it is converted into a digital signal. A higher bit depth means a more delicate color level and higher image quality.
• Sampling frequency:
• According to the Nyquist theorem, the sampling frequency must be at least twice the highest frequency of the signal to reconstruct the original signal without distortion. If the sampling clock frequency of the video capture card is less than twice the video bandwidth, it may cause image information loss or reduce quality.
• Resolution:
• Resolution is not only related to the display size, but also affected by factors such as the dot pitch of the picture tube and the video bandwidth. Higher resolution means that the image contains more pixels and can show richer details.
• Pixels:
• The number of pixels in the image acquisition card, that is, the number of photoelectric sensing elements on the CCD or CMOS sensor, determines the clarity and detail of the image. After each photosensitive element undergoes steps such as photosensitivity, photoelectric conversion, and A/D conversion, a dot is formed on the output photo. The more pixels, the higher the image quality.
• Video bandwidth:
• This refers to the transmission capacity of the video signal. The video bandwidth of the video acquisition card should match the signal source to ensure the complete acquisition of the video signal.
• Compatibility and supported input formats:
• The video acquisition card should support the output format of your video source (such as a camera), such as HDMI, SDI, VGA, etc., otherwise the video signal may not be captured correctly.
• Software compatibility and optimization:
• The compatibility of the acquisition card with the operating system and the quality of the related drivers will affect the efficiency of the acquisition process and the image quality.
• Hardware performance:
• The processing power and memory size of the computer, especially when acquiring at high resolution or high frame rate, powerful hardware can avoid image freezes and data loss.
• Cable quality:
• Using high-quality cables helps reduce signal attenuation and interference, thereby maintaining the integrity of the video signal.
Combining these factors, selecting and configuring the appropriate video capture card and its related settings is critical to achieving high-quality video capture.
