Determination of appropriate sampling conditions for three-dimensional microtopography measurement

Currently, there are no national or international standards available for the measurement of surface roughness in three-dimensions. The selection of measuring parameters (for example, the sampling interval and area) therefore relies largely on the experiences of users and is fraught with subjectivity. This is inconvenient, particularly for inexperienced users; moreover, this practice makes it difficult for inter-comparisons of measurement results to be conducted.

This paper aims to develop an objective criterion for selecting appropriate sampling conditions. A philosophy of surface roughness measurement in terms of the Nyquist wavelength limit is discussed. A sampling interval selection approach, based on spectral analysis, is then proposed. The proposed approach is not only applicable for the three-dimensional measurement scenario, but is also useful for the traditional two-dimensional measurement approach. The proposed technique has the added advantage that it can also be used to check the suitability of the measurement probe tip for any particular application. Experimental results based on measurements carried out on a large range of engineering surfaces (using a stylus instrument) are presented to demonstrate the effectiveness of the proposed approach.