How Optical CMMs and 3D Scanning Will Revolutionize the 3D Metrology World

Every day, optical technology plays a bigger and bigger role in metrology. No doubt optical metrology will soon be used to perform continuous, high-speed inspections of items of all shapes, sizes, and materials. However, it will take time to move from a world dominated by coordinate measuring machines that use sensors to one where optical CMM reigns, especially in industries such as automotive or aeronautics where every new thing must prove itself first. One of the biggest changes in metrology in the past 30 years has been the development of portable measuring devices. This has brought inspection right into the production line, as close to the part as possible. The change—sparked by the development of portable measuring arms in the early 1990s and the emergence of laser trackers shortly after—turned traditional industries' inspection methods completely upside down. However, most portable measurement solutions still use technologies that have serious limitations in production environments. For example, these solutions demand extreme stability throughout the measurement process. Optical solutions, especially those using video cameras, sidestep these limitations by enabling automatic positioning and continuous measurement. Now, laser- and white-light-based digitizing technologies can also produce increasingly dense data. In this chapter, we will see the basic implementation principles and advantages offered by these optical solutions for performing direct inspections in a production environment. Key point is about using optical reflectors as metrological references on parts and using these references to (1) allow self-positioning of handheld scanners, (2) automatically align the device with a predetermined 3D reference, (3) easily move the device around the part, and (4) maintain high measurement precision in industrial production environments. We will also analyze all the factors that go into measurement precision and see how the use of optical technologies make it possible to greatly reduce the primary causes of measurement imprecision. To illustrate our analysis, the reader will find specific cases taken from real applications in the aeronautical, automotive, and naval industries.