A RADIAL WHITE LIGHT INTERFEROMETER FOR MEASUREMENT OF CYLINDRICAL GEOMETRIES Andre R. Sousa 1 ; Armando Albertazzi 2 ; Alex Dal Pont 3 CEFET/SC – Federal Center for Technological Education of Sta. Catarina UFSC – Federal University of Santa Catarina Photonita – Photonical Instruments for Technical Applications asouza@cefetsc.edu.br 1 ; 2 albertazzi@labmetro.ufsc.br; 3 alex@photonita.com.br www.labmetro.ufsc.br; www.photonita.com.br Abstract This work presents a radial white light interferometer developed for non contact measurement of cylindrical parts. The system uses an innovative radial interferometer of non coherent light, enabling the measurement of a whole cylindrical area without any circular movement of the part. The system is fully automated and, as the measurement is performed over an area and not over a line, a few vertical steps are enough to evaluate the whole form of internal or external cylinders. Up to 300.000 points can be measured in each acquisition, making possible an in depth analysis of the cylindrical geometry. Dedicated software process the clouds of points and calculate parameters as circularity in each section, straightness of boundaries, cilindricity, etc. The measurement of the part can be done also by comparison with a standard or by comparison with the part itself, for example, in the evaluation of wear and loss of material during test of products. The part is measured before and after running a test and the results can be compared and several parameters calculated. The calibration of the system defined an uncertainty of ±0,002 mm for absolute measurements and ±0,001 mm for differential measurements. Keywords: White Light Interferometry, Precision Engineering, Dimensional Metrology 1. INTRODUCTION White light interferometry has been extensively used for profiling of technical parts. It combines the high sensitivity of interferometers and the ability to perform absolute height measurements. Parts with lateral sizes ranging from few micrometers to over 100 mm can be measured. It is possible to achieve height resolution better than one nanometer and measurement ranges up to several millimeters, what makes this technique excellent for industrial applications concerning geometric quality control. Several commercial systems using this measurement principle are already available on the market, but usually used to make measurements in rectangular coordinates. X and Y are associated with the lateral dimensions of the image and Z to the heights. In this paper the authors extends white light interferometry to measure in cylindrical coordinates. A high precision 45º conical mirror is used for both illuminate cylindrical parts and to image the resulting interference pattern into a CCD camera. This configuration opens possibilities for measuring high precision cylindrical or almost cylindrical parts. Either continuous or stepwise surfaces can be measured. The measurement principle, practical considerations and performance results are presented here as well few applications of practical interest. The system was developed at the Federal University of Santa Catarina in partnership with the company Photonita – Photonical Instruments for Technical Application Limited.