Full-field optical metrology in polar and cylindrical coordinates

Abstract

There are a large number of engineering measurement demands that can be very well met with optical methods. Among them, there are some that deal with circular or cylindrical geometries, for which Cartesian coordinates are not the ideal. Measurements in cylindrical and polar coordinates are much more natural choices. This paper presents an overview of various principles and configurations to measure textures, wear, geometry and deformations of external and internal cylindrical parts, displacements, deformations, stresses and residual stresses in cylindrical or polar coordinates. Optical measurement techniques such as triangulation, photogrammetry, deflectometry, white light interferometry, speckle interferometry, shearography in cylindrical or polar coordinates, are addressed. Most of the configurations presented here involve internal or external conical mirrors. These special optical components have several very interesting properties capable of performing transformations between coordinate systems. Examples of real engineering demands are presented and briefly discussed. The results obtained met the demands for which they were developed. Our expectation is that the configurations presented here can serve as a reference for already established applications and as a source of inspiration for new demands and possibilities.