ABSTRACT
Until a few years ago, optical (or noncontact) dimensional metrology was dominated by measuring microscopes and optical projectors. The prerequisites for state-of-theart optical coordinate metrology include the use of modern image processing techniques and laser sensors, which were developed during the last decade. Multisensor coordinate measuring machines (CMMs) today feature both contact and noncontact sensors, thus combining the advantages of tactile and optical measurements in a single
7.1 From Prole Projector to Optical-Tactile Metrology ................................... 125 7.2 Visual Sensors for Coordinate Measuring Machines ................................... 126
7.2.1 Optical Edge Sensor ......................................................................... 127 7.2.2 Image Processing Sensor .................................................................. 128 7.2.3 Illumination for Visual Sensors ........................................................ 131 7.2.4 Distance Sensors ............................................................................... 133 7.2.5 Autofocus .......................................................................................... 134 7.2.6 Laser Point Sensors ........................................................................... 134 7.2.7 Multidimensional Distance Sensors ................................................. 136 7.2.8 Multisensor Technology.................................................................... 137
7.3 Computer tomography .................................................................................. 139 7.3.1 Principle of X-Ray Tomography ....................................................... 139 7.3.2 Multisensor Coordinate Measuring Machines with X-Ray
Tomography ...................................................................................... 141 7.3.3 Accurate Measurements with Computer Tomography ..................... 142 7.3.4 Measuring a Plastic Part ................................................................... 146
7.4 Measuring Accuracy ..................................................................................... 147 7.4.1 Specication and Acceptance Testing .............................................. 147 7.4.2 Measurement Uncertainty ................................................................ 148 7.4.3 Correlation among Sensors ............................................................... 150
7.5 Outlook ......................................................................................................... 150
system. This sensor combination has made it possible to accomplish most of the measuring tasks encountered in present-day manufacturing. Optoelectronic sensors have gained signicance especially because of the growing complexity of part shapes and sizes and the advanced requirements of component miniaturization. The high measuring speed of multisensor CMMs permits economical, near-production measurement.
