Application of Fresnel diffraction to distance metrology

The use of Fresnel diffraction as a means for measuring absolute distances represents a unique approach to the science of non-contact distance metrology. Fresnel diffraction-based metrology measures the central intensity of a Fresnel diffraction pattern to determine the absolute distance to the source which is producing the pattern. This technique is presented at a time when traditional methods of non-contact distance measurement, particularly interferometric techniques and triangularization systems, are approaching a limit in their abilities. A Fresnel diffraction-based distance measurement system offers the potential for becoming the new standard in high accuracy, high versatility measurement tools. Because of the inherent simplicity involved in the extraction of distance information from a single Fresnel diffraction pattern, this technique is proving useful in a wide variety of applications.