Machine Vision

 

Lenses are the second part in the chain of image processing. Optimized illumination of an object provides the best conditions to transfer the image information from the object to the camera. This transfer is accomplished with optics, which may be a specially designed and extremely complex package (see image) or a simple combination of basic lenses. A lens (or better an objective containing several lenses) is always designed for certain parameters. It is always a compromise between magnification, field of view (FOV), F-number, spectral range, image size, aberrations, and finally costs. The resolution dictated by the camera's pixel size is often only reachable with a high quality lens - inexpensive lenses usually have a resolution of two or three pixels.

A general limit on an objective's resolution is given by diffraction, which is roughly equal to the F-number expressed in microns. The right choice of lenses is just as important as the choice of illumination.