Moire topography with color gratings

Optical triangulation-based microtopographic inspection of surfaces

The non-invasive inspection of surfaces is a major issue in a wide variety of industries and research laboratories. The vast and increasing range of surface types, tolerance requirements and measurement constraints demanded during the last decades represents a major research effort in the development of new methods, systems and metrological strategies. The discreet dimensional evaluation the rugometric characterization and the profilometric inspection seem to be insufficient in many instances. The full microtopographic inspection has became a common requirement. Among the different systems developed, optical methods have the most important role and among those triangulation-based ones have gained a major status thanks to their flexibility, reliability and robustness. In this communication we will provide a brief historical review on the development of optical triangulation application to the dimensional inspection of objects and surfaces and on the work done at the Microtopography Laboratory of the Physics Department of the University of Minho, Portugal, in the development of methods and systems of optical triangulation-based microtopographic inspection of surfaces.

Moiré topography by slit beam scanning

A new method of moiré topography is suggested in which a slit beam is used in a scanning mode to generate moiré fringes. One remarkable feature of this method is that, as opposed to existing shadow and projection types, height differences between two consecutive fringes become constant so that absolute fringe orders need not be identified. This advantage makes it possible to measure three-dimensional surface profiles in an automatic manner simply by using a computer-aided image-processing technique. In addition this method can be easily implemented in a conventional coordinate measuring machine with a minimum addition of optical hardware.