REAL TIME MICRODISPLACEMENTS TESTING BY OPTO-DIGITAL HOLOGRAPHIC INTERFEROMETRY TECHNIQUE
الكلمات المفتاحية:
Digital holography، Opto-digital holography، Holographic interferometry، Non destructive testingالملخص
In opposite of classical holography, the opto-digital holography recording step is based on CCD (charge coupled device) sensors and the optical reconstruction step is based on LCD (liquid crystal displays) or DMD (digital mirror displays) devices. Knowing, that the important disadvantage of these elements was their pixel size which was relatively high comparatively to the classical photoplate's grains size, it was not possible to make holograms of large objects. The quick evolution of these imaging devices, these last few years, permits to find, such devices with relatively low pixel size (nearly 4 μm for CCD and 7 μm for LCD). It is then possible to work on voluminous objects and to get best holograms quality. We show in this work that it is possible to record and reconstruct holograms of objects having several cms square.
Since all the process is controlled numerically, it is possible to follow in real time using the holographic interferometry techniques, double exposure, real time or time average, any changes in the object under study and to start and stop the process at any time by adequate software. This can be done by subtracting a reference image by suitable software directly on the CCD camera. We show also, the ability of the technique to study in real time all evolutional phenomena.
التنزيلات
المراجع
P. Hariharan, Optical Holography, Cambridge University Press, Cambridge, New Rochelle Melbourne Sydney, New York, 1987;
Graham Saxby, Practical Holography, Prentice Hall, New
York, London, Toronto, Sydney, Tokyo, 1988;
U. Schnars and W. Jüptner, Direct recording of holograms by CCD target and numerical reconstruction, Appl. Opt. 33 2 (1994), pp. 179–181;
U. Schnars. Direct phase determination in hologram interferometry with use of digitally recorded holograms, J. Opt. Soc. Am. 11 7 (1994), pp. 2011–2015;
L. Xu, J. Miao and A. Asundi. Properties of digital holography based on in-line configuration, Opt. Eng. 39 12 (2000), pp. 3214–3219;
D. Dirksen, H. Droste, B. Kemper, H. Delere, M. Deivick, H.H. Scheld and G. Bally. Lensless Fourier holography for digital holographic interferometry on biological samples, Opt. Lasers Eng. 36 3 (2001), pp. 241–249;
Mark A. Schulze, Martin A. Hunt, Edgar Voelkl, Joel D. Hickson, William Usry, Randall G. Smith, Robert Bryant, C. E. (Tommy) Thomas Jr. Semiconductor wafer defect detection using digital holography, Process and Materials Characterization and Diagnostics in IC Manufacturing II, SPIE's Advanced Microelectronic Micromanufacturing, Santa Clara, California, 27-28 February 2003;
L. Bouamama, M. Bouafia, G. Wernicke, S. Krueger, H. Gruber. Real time opto-digital holographic microscopy (RTODHM), Catalysis Today 89 (2004) 337–341;
T. Kreis, P. Asundi, R. Höfling. Hologram reconstruction using a digital micromirror device, Opt. Eng. 40 6 (2001), pp. 926–933.
