From the Profile Projector to Optical-Tactile Metrology

Up until a few years ago optical (or non-contact) dimensional metrology was dominated bymeasuring microscopes and projectors which had remained more or less unchanged since the development of the profile projector (Fig. 1). However, the automatic measurement of geometric features could only be performed for two-dimensional parts using the transmitted-light technique. More recently and because of its versatility, automated, multi-dimensional coordinate metrology has replaced many of the single-purpose machines previously used to measure industrially manufactured parts. As a result, this new type of metrology has displaced the older, less capable techniques and attained industry-wide acceptance.The prerequisites for state-of-the-art optical coordinate metrology include the use of modern image processing techniques and laser sensors first developed during the past decade. Multisensor coordinate measuring machines today feature both contact and non-contact sensors, thus combining the advantages of tactile and optical measurement in a single system. This sensor combination has made it possible to accomplish most measuring tasks encountered in present-day manufacturing. Optoelectronic sensors have gained significance especially because of the growing complexity of part shapes and sizes and the advanced requirements of component miniaturization. The high measuring speed of multisensor coordinate measuring machines permits economical, near-production measurement.While this versatile sensor technology offers the user a wide variety of application possibilities, it also demands a deeper understanding of its inherent productive capabilities and limits. The purpose of this book is to make this new technology both easier to understand and easier to use. It closes a gap in the previously available technical literature which primarily dealt with mechanical probing [1, 2, 4, 7]. Although this book is concerned mostly with optoelectronic sensors, it also touches on important aspects of tactile sensors and combined optical-tactile measurement approaches. Much consideration has been given to applications, and a separate chapter has been devoted to the subject of measuring accuracy.


Fig. 1: Profile projector (Werth RECORD®), 1954 model