Analysing and evaluating a dual-sensor autofocusing method for measuring the position of patterns of small holes on complex curved surfaces

A case study is presented which evaluates the accuracy of a pattern of Ø 0.5 mm small holes on an elliptic cylinder. A mathematical analysis of that problem and practical results from both the tactile and optical sensors are provided and discussed. It is estimated that the deviation in optimal focusing induced by this automated method is between −23 μm and +95 μm. This is sufficiently accurate to ensure that the optical device can capture the entire space outline of each of the small holes on the complex curve surface clearly and can therefore identify its centroid from the image to provide a measurement of the position.