Industrial Calibration Procedure for Confocal Microscopes

Abstract

Coordinate metrology techniques are widely used in industry to carry out dimensional measurements. For applications involving measurements in the submillimeter range, the use of optical, non-contact instruments with suitable traceability is usually advisable. One of the most used instruments to perform measurements of this type is the confocal microscope. In this paper, the authors present a complete calibration procedure for confocal microscopes designed to be implemented preferably in workshops or industrial environments rather than in research and development departments. Therefore, it has been designed to be as simple as possible. The procedure was designed without forgetting any of the key aspects that need to be taken into account and is based on classical reference material standards. These standards can be easily found in industrial dimensional laboratories and easily calibrated in accredited calibration laboratories. The procedure described in this paper can be easily adapted to calibrate other optical instruments (e.g., focus variation microscopes) that perform 3D dimensional measurements in the submillimeter range.

Special Issue of the Manufacturing Engineering Society 2019 (SIMES-2019)

“…In this Special Issue of the journal Materials, 29 contributions to cutting-edge advances in different fields of the manufacturing engineering have been collected. In particular, in additive manufacturing and 3D printing [4][5][6][7][8][9][10][11]; sustainable and green manufacturing [12][13][14][15][16]; metrology and quality in manufacturing [17][18][19][20][21]; advances and innovations in manufacturing processes [22][23][24][25]; manufacturing of new materials [26][27][28]; design, modeling, and simulation in manufacturing engineering [29,30] industry 4.0 [31] and manufacturing engineering and society [32]. Among all of them, the topic additive manufacturing and 3D printing stands out for the number of contributions it has had in this Special Issue showing the interest that this topic arouses, currently, among researchers, the industry and the public in general.…”

“…In addition, the Special Issue shows three papers in the topic manufacturing of new materials. Concretely, two about thermoplastic carbon fiber composites C/TPU [26,27] and, other, about an Al-SiC metal matrix composite [28]. It counts also with two works in design, modeling, and simulation in manufacturing engineering about the indentation process [29] and the cold expansion process [30]; one, in the topic industry 4.0 about the application of the supply chain to shipbuilding [31] and the other in the topic manufacturing engineering and society about a new risk methodology based on control charts to assess occupational risks in manufacturing processes [32].…”

Design of Industrial Standards for the Calibration of Optical Microscopes

“…In this procedure, the plane XY and Z-axis and the Ra (roughness parameter that it is given by the confocal microscope) are traced to the SI reference. This method, that could be adapted for other types of microscopes with minor changes, is based in the use of traceable standards and parts easy to find at industry and roughness is calibrated using Type C1 and D1 standards [38].…”

“…The calibration of this model would be accomplished by carrying out the measurement of the pitch on one direction, turning the standard 45º four times and repeating the measurement of the pitch on each direction, as in [38]. Typically, several measurements should be taken for obtaining better results.…”

“…When the calibration process is carried out using contact methods, it will depend on the dimensions and the shape of the stylus and it would be difficult to obtain good results of the measurement in some circumstances. For this reason, the use optical measuring instruments for the calibration as in [38] is a good alternative.…”