Advanced Inspection Techniques

Abstract

To date, Automated Visual Inspection has concentrated almost exclusively on mass- produced objects, because the high cost of designing an inspection system has made it uneconomic to apply these techniques to any other type of artifact. However, there are several possible applications areas for industrial vision systems that have been almost totally neglected to date and which we shall address in this chapter: (i) Objects made in small quantities. (It has been estimated that 75% of manufactured goods are made in batches of 50, or fewer, items.) (ii) Complex (monolithic) objects. Examples are car engine blocks, castings, mouldings and currency notes. (iii) Inspecting assemblies of components (e.g. pianos, printed circuit boards, electric motors, hair-dryers, in-flight meal trays, computer keyboards, etc.). (iv) Mass-produced goods which are deliberately made with a high degree of individual variation, to simulate their being hand made. (There has always been a high premium paid for hand-made objects, such as wood carvings, hand- thrown pottery, embroidery, painted china, etc. While it is a relatively straightforward matter to manufacture goods with the same level of variability that hand-made goods possess1, it is not yet feasible economically to inspect them automatically. If this did come about, then “individual character”, similar to that so prized in hand-made goods, could be added to many more massproduced artifacts.) (v) Objects which have, by their very nature, a high degree of variability. Good examples of this group are to be found in the food manufacturing industry. (Pizzas are like fingerprints - no two look exactly alike!) (vi) Objects which are either flexible or consist of an assembly of jointed parts. (vii) Natural objects which also exhibit a high degree of variability and which have ill-defined quality criteria.