Measurement and correction of the slope angle of flat surfaces digitized by a conoscopic holography system

Abstract

Conoscopic Holography (CH) is a non-contact interferometric technique used in surface digitizing. Similarly to other laser techniques it is influenced by the optical behaviour of the part surface and the conditions during scanning (geometry, strategy, etc.). In this work, a CH system and a touch probe (TP) integrated in a CMM were used to analyse the CH behaviour for measuring the slope angle of flat surfaces in inspection tasks. For this purpose, several digitizing tests were performed with both sensors on a square specimen under different slope angles. The tests were performed for two different orientations of the laser spot as well as at three different positions within the sensor depth of field (DOF). The specimen angles determined by each sensor were compared to each other and the difference (slope deviation) was used as an indicator of the CH behaviour. Considering the results, some recommendations were provided for digitizing sloped flat surfaces with the CH sensor and it was also developed a model to predict and compensate the measurement deviations of this sensor with regard to the TP.