volume | PIER Journals

Abstract

A coherent imaging system images a frame or an object onto a changing diffuser and projects the resulting pattern which generally contains speckles. Using a spatial light modulator (SLM) as the changing diffuser, the speckles in the pattern are suppressed without the need for any other mechanisms. With $M$ random phasor arrays being displayed in the SLM during the integration time of a detector, a suppression factor (C_f) of speckles, 1/√M, is achievable in the projected pattern, which is the sum of the intensity of M uncorrelated patterns. This paper shows both theoretically and in simulations that the C_f of the sum pattern was considerably reduced when two elementary patterns with fully developed speckles were negatively correlated. With the correlation coefficients of the elementary patterns found at [-0.3, -0.25], the C_f of the sum of 10 negatively-correlated speckle patterns was 48% lower than the C_f of the sum of 10\,uncorrelated speckle patterns. The negatively correlated patterns can be implemented using spatial light modulators or diffractive optical elements, and are used to suppress speckle noise in digital holography, laser projection display, and holographic display projections with relatively high efficiency.

1. Goodman, J. W., "Some fundamental properties of speckle," Journal of Optical Society America, Vol. 66, 1145-1150, 1976.
doi:10.1364/JOSA.66.001145

2. Silverstein, S. D. and M. O'Donnell, "Theory of frequency and temporal compounding in coherent imaging: Speckle suppression and image resolution," Journal of Optical Society America A, Vol. 5, 104-113, 1988.
doi:10.1364/JOSAA.5.000104

3. Goodman, J. W., Speckle Phenomena in Optics: Theory and Applications, Roberts & Co., 2007.

4. Rojas, J. A. M., J. Alpuente, E. Bolívar, P. López-Espí, S. Vignote, and M. I. Rojas, "Empirical characterization of wood surfaces by means of iterative autocorrelation of laser speckle patterns," Progress In Electromagnetics Research, Vol. 80, 295-306, 2008.
doi:10.2528/PIER07112706

5. Iwai, T. and T. Asakura, "Speckle reduction in coherent information processing," Proceedings of The IEEE, Vol. 84, 765-781, 1996.
doi:10.1109/5.488745

6. Wang, L., T. Tschudi, T. Halldórsson, and P. R. Pétursson, "Speckle reduction in laser projection systems by diffractive optical elements," Applied Optics, Vol. 37, 1770-1775, 1998.
doi:10.1364/AO.37.001770

7. Trisnadi, J. I., "Hadamard speckle contrast reduction," Optics Letters, Vol. 29, 11-13, 2004.
doi:10.1364/OL.29.000011

8. Qi, F., V. Tavakol, D. Schreurs, and B. K. J. C. Nauwelaers, "Discussion on validity of Hadamard speckle contrast reduction in coherent imaging system," Progress In Electromagnetics Research, Vol. 104, 125-143, 2010.
doi:10.2528/PIER10040604

9. Yurlov, V., A. Lapchuk, S. Yun, J. Song, and H. Yang, "Speckle suppression in scanning laser display," Applied Optics, Vol. 47, 179-187, 2008.
doi:10.1364/AO.47.000179

10. Akram, M. N., V. Kartashov, and Z. Tong, "Speckle reduction in line-scan laser projectors using binary phase codes," Optics Letters, Vol. 35, 444-446, 2010.
doi:10.1364/OL.35.000444

11. Kartashov, V. and M. N. Akram, "Speckle suppression in projection displays by using a motionless changing diffuser," Journal of Optical Society America A, Vol. 27, 2593-2601, 2010.
doi:10.1364/JOSAA.27.002593

12. Ouyang, G., Z. Tong, M. N. Akram, K. Wang, V. Kartashov, X. Yan, and X. Chen, "Speckle reduction using a motionless diffractive optical element," Optics Letters, Vol. 35, 2852-2854, 2010.
doi:10.1364/OL.35.002852

13. Tong, Z., M. N. Akram, and X. Chen, "Speckle reduction using orthogonal arrays in laser projectors," Applied Optics, Vol. 49, 6425-6429, 2010.
doi:10.1364/AO.49.006425

14. Chang, Y.-S., H. Y. Lin, and W.-F. Hsu, "Speckle suppression by 2D spatial light modulator in laser projection system," SID 2011 Symposium, Vol. 32.2, Los Angeles, May 15--19, 2011.

15. Bay, C., N. Hubner, J. Freeman, and T. Wilkinson, "Maskless photolithography via holographic optical projection," Optics Letters, Vol. 35, 2230-2232, 2010.
doi:10.1364/OL.35.002230

16. Hsu, W.-F. and C.-F. Yeh, "Speckle suppression in holographic projection displays by temporal integration of diffractive optical elements," Digital Holography and Three Dimensional Imaging, DH, paper DTuC4, Tokyo, Japan, May 9--11, 2011.

17. Buckley, E., "Holographic laser projection," J. Display Technology, Vol. 7, 135-140, 2011.
doi:10.1109/JDT.2010.2048302

18. Hsu, W.-F., Y.-W. Chen, and Y.-H. Su, "Implementation of phase-shift patterns using a holographic projection system with phase-only diffractive optical elements," Applied Optics, Vol. 50, 3646-3652, 2011.
doi:10.1364/AO.50.003646

19. Goodman, J. W., Statistical Optics, 17, John Wiley & Sons, Inc., NY, 1985.

20. Kreyszig, E., Advanced Engineering Mathematics, 9th Ed., 1089, John Wiley & Sons, Inc., NY, 2006.

21. Pedersen, H. M., "Theory of speckle-correlation measurements using nonlinear detectors," Journal of Optical Society America A, Vol. 1, 850-855, 1984.
doi:10.1364/JOSAA.1.000850

22. Marron, J. and G. M. Morris, "Correlation measurements using clipped laser speckle," Applied Optics, Vol. 25, 789-793, 1986.
doi:10.1364/AO.25.000789

23. Ogiwara, A. and J. Ohtsubo, "Maximum dynamic range of clipped correlation of integrated laser speckle intensity," Journal of Optical Society America A, Vol. 5, 403-405, 1988.
doi:10.1364/JOSAA.5.000403

24. Ohtsubo, J. and T. Asakura, "Statistical properties of the sum of partially developed speckle patterns," Optics Letters, Vol. 1, 98-100, 1977.
doi:10.1364/OL.1.000098

Dr. Wei-Feng Hsu

Dr. I.-Lin Chu