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Proceedings Paper

Fringe generation and phase shifting with LCDs in projection moiré topography
Author(s): Jan A. N. Buytaert; Joris J. J. Dirckx
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Paper Abstract

Structured light projection techniques are an important and popular approach for whole-field surface topography. Within this branch, projection moiré interferometry is our preferred optical metrology method. The use of liquid crystal display (LCD) projectors to produce structured light patterns has been proposed and used before in projection moiré. It allows fast and easy adaptation of the grid pitch and thus measurement sensitivity. In this paper we will show how using a second liquid crystal panel makes the projection moiré technique even more versatile and performant: The setup incorporates optical demodulation (OD) which in turn allows for accurate phase-shifting and the use of phase-shifting algorithms (PSAs). The Z-resolution is high and no filtering or interpolation is needed in X-Y by using the gray scale value variations through the phase-shifting and optical demodulation. Thus, we make optimal use of the camera pixel resolution and achieve an uncompromised measuring resolution. Furthermore, the setup is entirely digitally controlled, needs no physical interaction and avoids mechanically moving component. The low-cost setup, technique and theory will be covered in this talk. The resolution and other performance properties will be discussed and demonstrated. And to conclude, an application to achieve elasticity parameters of membranes will be shown. interferometry is our preferred optical metrology method. The use of liquid crystal display (LCD) projectors to produce structured light patterns has been proposed and used before in projection moiré. It allows fast and easy adaptation of the grid pitch and thus measurement sensitivity. In this paper we will show how using a second liquid crystal panel makes the projection moiré technique even more versatile and performant: The setup incorporates optical demodulation (OD) which in turn allows for accurate phase-shifting and the use of phase-shifting algorithms (PSAs). The Z-resolution is high and no filtering or interpolation is needed in X-Y by using the gray scale value variations through the phase-shifting and optical demodulation. Thus, we make optimal use of the camera pixel resolution and achieve an uncompromised measuring resolution. Furthermore, the setup is entirely digitally controlled, needs no physical interaction and avoids mechanically moving component. The low-cost setup, technique and theory will be covered in this talk. The resolution and other performance properties will be discussed and demonstrated. And to conclude, an application to achieve elasticity parameters of membranes will be shown.

Paper Details

Date Published: 15 April 2010
PDF: 8 pages
Proc. SPIE 7522, Fourth International Conference on Experimental Mechanics, 75220H (15 April 2010); doi: 10.1117/12.851666
Show Author Affiliations
Jan A. N. Buytaert, Univ. of Antwerp (Belgium)
Joris J. J. Dirckx, Univ. of Antwerp (Belgium)


Published in SPIE Proceedings Vol. 7522:
Fourth International Conference on Experimental Mechanics
Chenggen Quan; Kemao Qian; Anand Krishna Asundi; Fook Siong Chau, Editor(s)

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