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Vol: 55(69) No: 4 / December 2010 Retrofitting a Length Measuring Machine for Linear Scale Calibration Gyula Hermann Department of Intelligent Engineering Systems, Óbuda University, Faculty of Informatics, Bécsi út 93B, 1034 Budapest, Hungary, phone: (+36-1) 666-5535, e-mail: hermann.gyula@nik.uni-obuda.hu Kálmán Tomanyiczka Metrology Division, Hungarian Trade Licensing Offics, Németvölgyi út 37-39, 112 Budapest, Hungary, phone: (+36-1) 458-5854, e-mail: tomanyiczka@mkeh.hu Keywords: linear scale calibration, length measuring machine, nanometer resolution, ultrasonic piezomotor Abstract The paper describes a project with the aim of retrofitting a length measuring machine for the calibration of linear scales, with scale division in the micrometer range. It consists of an optical system, including a CCD camera with a built-in computer, for capturing the line width and the scale division, through the lens and backlight illumination. The motion system carrying the scale scale is driven by a pair of symmetrically located ultrasonic piezomotors providing nanometer resolution. To control the carriege motion Cerebella Model Articulated Controller (CMAC) was used. The paper starts with presenting the various definitions of the scale division. From these definitions simple algorithms, to determine the pitch, are derived. The main point is to minimize the effect of non-linearity and diffraction, by using high resolution optics and through the lens illumination, hereby improving measurement accuracy. The displacement is measured by an HP heterodyne laser interferometer. The scale division is determined by correcting the measured displacement with distance between the optical axis and the line position determined by the camera. For higher resolution the CCD camera system can be replaced by a near field microscope. References Barakauskas, A., Kasparaitis, A., Šukys, A., Kojelavičius, P., “Analysis of Geometrical Accuracy of Long Grating Scale Calibrator”. [2] Bers, J.S., Penzes, W.B., “The NIST length scale calibration interferometer” Journal of Research of the National Standards and Technology, Vol. 104, No.3 May-June 1999, pp. 225-252. [3] Druzuvec, M., Acko, B., Godina, A., Weller, T., “Simulation of line scale contamination in calibration uncertainty model”, Int. Journ. Simul. Model, vol. 7, no. 3, pp. 113-123, 2008. [4] Hermann, Gy. “Geometric Error Correction in Coordinate Measurement”, Acta Polytechnica Hungarica, vol. 4, no. 1, pp. 47-62, 2007. [5] Jakštas, A., Kaušiniš, S., Flügge, J., “Investigation of calibration facilities of precision line scales”, Mechanika, vol. 53, no. 3, pp. 62-67, 2005. [6] Kaušinis, S., Jakštas, A., Barakauskas, A., Kasparaitis, A., “Investigating of dynamic properties of line scale calibration system”, Proceedings of XVIII IMEKO World Congress Metrology for Sustainable Development, 2006, Rio de Janeiro, Brazil. [7] Meli, F., Thalman, R., Blattner, P., “High precision pitch calibration of gratings using diffraction interferometry”, Proceedings of the 1st. Conf. on Precision Engineering and Nanotechnology, 1999, Bremen, Germany, vol. 2, pp. 252-255. [8] Misumi, I., Gonda, S., Kurosowa, T., Tanimura, Y., Ochiai, N., Kitta, J., Kubota, F., Yamada, M., Fujiwara, Y., Nakayama, Y., Takamasu, K., “Comparing measurements of 1D-grating samples using optical diffraction technique, CD-SEM and nanometrological AFM”, Proceedings of the 3rd EUSPEN International Conference, Eindhoven, The Netherlands, 2002, pp. 517-520. [9] Peng Xi, Changhe Zhou, Hongxin Luo, Enwen Dai, Liren Liu, “Near field detection of the quality of high-density gratings with nanotechnology” Proceedings of SPIE Nano and Micro-Optics for Information Systems, vol. 5225. pp. 140-144. [10] Tae Bong Eom, Jin Wan Han “A multi-purpose linear measuring system with laser interferometer”. [11] Theska, R., Frank, T., Hackel, T., Höhne, G., Lotz, M., “Design principles for highest precision applications”. [12] WGDM-7 Preliminary comparison on nano-metrology according to the rules of CCL key comparisons. Nano 3 Line scale standards. Final report. PTB Braunschweig, Aug. 29, 2003. |