For decades, engineers developing metrology instrumentation have used telecentric lenses in their products. Contour projectors and optical comparators, for example, owe much of their measurement capability to these unique lenses.Over the past decade or two, as new technologies have shifted product emphasis toward electronic features and digital processing, optical system design has frequently been relegated to a low priority, with the expectation that software will correct poor imagery.Quite recently, however, there has been a revival of interest in solving imaging problems in the optics and lighting "front end" of a system. The increasing use of telecentric lenses in many machine vision applications provides a striking example. Design engineers have discovered that it is often easier and ultimately less expensive to provide "optically processed" images by using telecentric lenses and appropriate lighting.Because telecentric lenses provide accurate images at the speed of light, their use also reduces the demands on the digital processor, speeding up a vision systemis throughput. In addition, telecentric lenses can solve many imaging problems that software cannot...