The Importance of Consistent Illumination in Machine Vision
Machine vision systems evaluate the image of the object, not the object itself, so the first stage in the process is to get the correct lighting arrangement for the application.
Machine vision systems are used throughout industry for critical inspection and measurement, frequently as part of a quality control approach. It is essential that the measurements made are both accurate and repeatable, because any variable, either internal or external that affects the performance of the imaging system could in turn affect the resulting measurements. This is just as important when inspecting low-cost, high-volume components as it is for high-cost, low-volume items.
Machine vision systems evaluate the image of the object, not the object itself, so the first stage in the process is to get the correct lighting arrangement for the application, to ensure that the camera can capture an image containing all of the details needed to make the measurements. This is essential since if any information is missing as a result of incorrect illumination, subsequent measurements are much more difficult or impossible. Information that is completely missing from the image can never be recovered by analysis algorithms. The way the light strikes the target, the wavelength of the light and the nature of the sample surface all influence the image produced at the camera. The direction of light allows different features to be highlighted while the use of a light of particular wavelength can have a major influence on the contrast in the image. In addition, the surface of the object affects the image, with shiny surfaces in particular giving rise to multiple reflections.