Why is the Zoom Lens not Recommended to Machine Vision System?
As for the image operation of machine vision, the zoom lens is not recommended. The factor including:
1. As far as it goes, zoom lens is commonly used in the field of security monitoring. Currently, its highest resolution is only about 1.5 megapixels, but the physical resolution of industrial cameras is usually as high as 5-10 megapixels for high-accuracy pixel-level calculating of automation systems. Generally, the precision of physical resolution is greatly affected by the bottleneck of optical resolution, which affects the accuracy of calculation results.
2. The main f-stop of the zoom lens is 1/3 inch, and for high-accuracy pixel-level calculating, the sensor size of high-resolution industrial cameras is usually larger than 1/2 inch. Obviously, the image will be obscured if you use a zoom lens.
3. Due to its optical characteristics, the f-stop also changes when the focal length changes. The auto-aperture adjustment is necessary if the image brightness at different focal points is to be consistent. However, the use of auto-aperture will complicate the system, and the high-frequency motion of the aperture motor will sharply shorten the life of the lens.
4. To cover the short and long focuses, a zoom lens must strike a balance between the two items. For the prime lens, the physical distortion can be corrected by a special correction technique; but the distortion of the zoom lens cannot resolved in the same way. As for zoom lens, the distortion curve becomes irregular and uncontrollable in the change of focal length.
4. For industrial inspection, especially the robot automatic control system, has a high requirement for imaging stability. And therefore the key to the stable operation of the whole system is the high resolution industrial camera, the high stability lighting source and the high resolution prime lens.