Abstract

We present a simple and robust approach to reduce laser speckle, which has limited the adoption of lasers in imaging and display applications. We use colloidal solutions that can quickly reduce speckle contrast due to the Brownian motion of the scattering particles. The high insertion loss associated with propagation through a colloidal solution was overcome by using white paint to cover the sides of the cuvette and an optical fiber to deliver the laser light deep into the colloidal solution, enabling transmission greater than 90%. The diffused laser output followed a Lambertian distribution and produced speckle contrast below 4% at an integration time of 129 μs. The ability for colloidal solutions to achieve fast speckle reduction without power consumption while maintaining high transmission, low cost, a compact size, and a long lifetime makes our approach useful for a wide range of laser imaging and projection applications.

© 2013 Optical Society of America

Full Article  |  PDF Article

References

  • View by:
  • |
  • |
  • |

  1. K. V. Chellappan, E. Erden, and H. Urey, “Laser-based displays: a review,” Appl. Opt. 49, F79–F98 (2010).
    [CrossRef]
  2. J. D. Rigden and E. I. Gordon, “The granularity of scattered optical maser light,” Proc. Inst. Radio Eng. 50, 2367–2368 (1962).
  3. J. W. Goodman, “Optical methods for suppressing speckle,” in Speckle Phenomena in Optics (Roberts, 2007), pp. 141–186.
  4. J. M. Artigas, A. Felipe, and M. J. Buades, “Contrast sensitivity of the visual system in speckle imagery,” J. Opt. Soc. Am. A 11, 2345–2349 (1994).
    [CrossRef]
  5. A. G. Geri and L. A. Williams, “Perceptual assessment of laser-speckle contrast,” J. Soc. Inf. Disp. 20, 22–27 (2012).
    [CrossRef]
  6. T. S. McKechnie, “Speckle reduction,” in Topics in Applied Physics, J. C. Dainty, ed. (Springer-Verlag, 1975), pp. 123–170.
  7. J. G. Manni and J. W. Goodman, “Versatile method for achieving 1% speckle contrast in large-venue laser projection displays using a stationary multimode optical fiber,” Opt. Express 20, 11288–11315 (2012).
    [CrossRef]
  8. A. H. Dhalla, J. V. Migacz, and J. A. Izatt, “Crosstalk rejection in parallel optical coherence tomography using spatially incoherent illumination with partially coherent sources,” Opt. Lett. 35, 2305–2307 (2010).
    [CrossRef]
  9. B. Dingel, S. Kawata, and S. Minami, “Speckle reduction with virtual incoherent laser illumination using a modified fiber array,” Optik 94, 132–136 (1993).
  10. B. Dingel and S. Kawata, “Laser-diode microscope with fiber illumination,” Opt. Commun. 93, 27–32 (1992).
    [CrossRef]
  11. J. Seurin, G. Xu, B. Guo, A. Miglo, Q. Wang, P. Pradhan, J. D. Wynn, V. Khalfin, W. Zou, C. Ghosh, and R. Van Leeuwen, “Efficient vertical-cavity surface-emitting lasers for infrared illumination applications,” Proc. SPIE 7952, 79520G (2011).
    [CrossRef]
  12. B. Redding, M. A. Choma, and H. Cao, “Spatial coherence of random laser emission,” Opt. Lett. 36, 3404–3406 (2011).
    [CrossRef]
  13. B. Redding, M. A. Choma, and H. Cao, “Speckle-free laser imaging using random laser illumination,” Nat. Photonics 6, 355–359 (2012).
    [CrossRef]
  14. L. Wang, T. Tschudi, T. Halldorsson, and P. R. Petursson, “Speckle reduction in laser projection systems by diffractive optical elements,” Appl. Opt. 37, 1770–1775 (1998).
    [CrossRef]
  15. S. Lowenthal and D. Joyeux, “Speckle removal by a slowly moving diffuser associated with a motionless diffuser,” J. Opt. Soc. Am. 61, 847–851 (1971).
    [CrossRef]
  16. M. N. Akram, Z. Tong, G. Ouyang, X. Chen, and V. Kartashov, “Laser speckle reduction due to spatial and angular diversity introduced by fast scanning micromirror,” Appl. Opt. 49, 3297–3304 (2010).
    [CrossRef]
  17. J. I. Trisnadi, “Hadamard speckle contrast reduction,” Opt. Lett. 29, 11–13 (2004).
    [CrossRef]
  18. M. N. Akram, V. Kartashov, and Z. Tong, “Speckle reduction in line-scan laser projectors using binary phase codes,” Opt. Lett. 35, 444–446 (2010).
    [CrossRef]
  19. A. L. Andreev, I. N. Kompanets, M. V. Minchenko, E. P. Pozhidaev, and T. B. Andreeva, “Speckle suppression using a liquid-crystal cell,” Quantum Electron. 38, 1166–1170 (2008).
    [CrossRef]
  20. G. Ouyang, Z. Tong, M. N. Akram, K. Wang, V. Kartashov, X. Yan, and X. Chen, “Speckle reduction using a motionless diffractive optical element,” Opt. Lett. 35, 2852–2854 (2010).
    [CrossRef]
  21. F. Riechert, G. Bastian, and U. Lemmer, “Laser speckle reduction via colloidal-dispersion-filled projection screens,” Appl. Opt. 48, 3742–3749 (2009).
    [CrossRef]
  22. I. D. Morrison and S. Ross, Colloidal Dispersions: Suspensions, Emulsions, and Foams (Wiley, 2002).
  23. D. J. Pine, D. A. Weitz, P. M. Chaikin, and E. Herbolzheimer, “Diffusing-wave spectroscopy,” Phys. Rev. Lett. 60, 1134–1137 (1988).
    [CrossRef]
  24. M. C. W. van Rossum and Th. M. Nieuwenhuizen, “Multiple scattering of classical waves: microscopy, mesoscopy, and diffusion,” Rev. Mod. Phys. 71, 313–371 (1999).
    [CrossRef]
  25. J. J. Chen and C. T. Lin, “Freeform surface design for a light-emitting diode-based collimating lens,” Opt. Eng. 49, 093001 (2010).
    [CrossRef]
  26. T. Kari, J. Gadegaard, T. Sndergaard, T. G. Pedersen, and K. Pedersen, “Reliability of point source approximations in compact LED lens designs,” Opt. Express 19, A1190–A1195 (2011).
    [CrossRef]

2012 (3)

A. G. Geri and L. A. Williams, “Perceptual assessment of laser-speckle contrast,” J. Soc. Inf. Disp. 20, 22–27 (2012).
[CrossRef]

B. Redding, M. A. Choma, and H. Cao, “Speckle-free laser imaging using random laser illumination,” Nat. Photonics 6, 355–359 (2012).
[CrossRef]

J. G. Manni and J. W. Goodman, “Versatile method for achieving 1% speckle contrast in large-venue laser projection displays using a stationary multimode optical fiber,” Opt. Express 20, 11288–11315 (2012).
[CrossRef]

2011 (3)

B. Redding, M. A. Choma, and H. Cao, “Spatial coherence of random laser emission,” Opt. Lett. 36, 3404–3406 (2011).
[CrossRef]

T. Kari, J. Gadegaard, T. Sndergaard, T. G. Pedersen, and K. Pedersen, “Reliability of point source approximations in compact LED lens designs,” Opt. Express 19, A1190–A1195 (2011).
[CrossRef]

J. Seurin, G. Xu, B. Guo, A. Miglo, Q. Wang, P. Pradhan, J. D. Wynn, V. Khalfin, W. Zou, C. Ghosh, and R. Van Leeuwen, “Efficient vertical-cavity surface-emitting lasers for infrared illumination applications,” Proc. SPIE 7952, 79520G (2011).
[CrossRef]

2010 (6)

2009 (1)

2008 (1)

A. L. Andreev, I. N. Kompanets, M. V. Minchenko, E. P. Pozhidaev, and T. B. Andreeva, “Speckle suppression using a liquid-crystal cell,” Quantum Electron. 38, 1166–1170 (2008).
[CrossRef]

2004 (1)

1999 (1)

M. C. W. van Rossum and Th. M. Nieuwenhuizen, “Multiple scattering of classical waves: microscopy, mesoscopy, and diffusion,” Rev. Mod. Phys. 71, 313–371 (1999).
[CrossRef]

1998 (1)

1994 (1)

1993 (1)

B. Dingel, S. Kawata, and S. Minami, “Speckle reduction with virtual incoherent laser illumination using a modified fiber array,” Optik 94, 132–136 (1993).

1992 (1)

B. Dingel and S. Kawata, “Laser-diode microscope with fiber illumination,” Opt. Commun. 93, 27–32 (1992).
[CrossRef]

1988 (1)

D. J. Pine, D. A. Weitz, P. M. Chaikin, and E. Herbolzheimer, “Diffusing-wave spectroscopy,” Phys. Rev. Lett. 60, 1134–1137 (1988).
[CrossRef]

1971 (1)

1962 (1)

J. D. Rigden and E. I. Gordon, “The granularity of scattered optical maser light,” Proc. Inst. Radio Eng. 50, 2367–2368 (1962).

Akram, M. N.

Andreev, A. L.

A. L. Andreev, I. N. Kompanets, M. V. Minchenko, E. P. Pozhidaev, and T. B. Andreeva, “Speckle suppression using a liquid-crystal cell,” Quantum Electron. 38, 1166–1170 (2008).
[CrossRef]

Andreeva, T. B.

A. L. Andreev, I. N. Kompanets, M. V. Minchenko, E. P. Pozhidaev, and T. B. Andreeva, “Speckle suppression using a liquid-crystal cell,” Quantum Electron. 38, 1166–1170 (2008).
[CrossRef]

Artigas, J. M.

Bastian, G.

Buades, M. J.

Cao, H.

B. Redding, M. A. Choma, and H. Cao, “Speckle-free laser imaging using random laser illumination,” Nat. Photonics 6, 355–359 (2012).
[CrossRef]

B. Redding, M. A. Choma, and H. Cao, “Spatial coherence of random laser emission,” Opt. Lett. 36, 3404–3406 (2011).
[CrossRef]

Chaikin, P. M.

D. J. Pine, D. A. Weitz, P. M. Chaikin, and E. Herbolzheimer, “Diffusing-wave spectroscopy,” Phys. Rev. Lett. 60, 1134–1137 (1988).
[CrossRef]

Chellappan, K. V.

Chen, J. J.

J. J. Chen and C. T. Lin, “Freeform surface design for a light-emitting diode-based collimating lens,” Opt. Eng. 49, 093001 (2010).
[CrossRef]

Chen, X.

Choma, M. A.

B. Redding, M. A. Choma, and H. Cao, “Speckle-free laser imaging using random laser illumination,” Nat. Photonics 6, 355–359 (2012).
[CrossRef]

B. Redding, M. A. Choma, and H. Cao, “Spatial coherence of random laser emission,” Opt. Lett. 36, 3404–3406 (2011).
[CrossRef]

Dhalla, A. H.

Dingel, B.

B. Dingel, S. Kawata, and S. Minami, “Speckle reduction with virtual incoherent laser illumination using a modified fiber array,” Optik 94, 132–136 (1993).

B. Dingel and S. Kawata, “Laser-diode microscope with fiber illumination,” Opt. Commun. 93, 27–32 (1992).
[CrossRef]

Erden, E.

Felipe, A.

Gadegaard, J.

Geri, A. G.

A. G. Geri and L. A. Williams, “Perceptual assessment of laser-speckle contrast,” J. Soc. Inf. Disp. 20, 22–27 (2012).
[CrossRef]

Ghosh, C.

J. Seurin, G. Xu, B. Guo, A. Miglo, Q. Wang, P. Pradhan, J. D. Wynn, V. Khalfin, W. Zou, C. Ghosh, and R. Van Leeuwen, “Efficient vertical-cavity surface-emitting lasers for infrared illumination applications,” Proc. SPIE 7952, 79520G (2011).
[CrossRef]

Goodman, J. W.

Gordon, E. I.

J. D. Rigden and E. I. Gordon, “The granularity of scattered optical maser light,” Proc. Inst. Radio Eng. 50, 2367–2368 (1962).

Guo, B.

J. Seurin, G. Xu, B. Guo, A. Miglo, Q. Wang, P. Pradhan, J. D. Wynn, V. Khalfin, W. Zou, C. Ghosh, and R. Van Leeuwen, “Efficient vertical-cavity surface-emitting lasers for infrared illumination applications,” Proc. SPIE 7952, 79520G (2011).
[CrossRef]

Halldorsson, T.

Herbolzheimer, E.

D. J. Pine, D. A. Weitz, P. M. Chaikin, and E. Herbolzheimer, “Diffusing-wave spectroscopy,” Phys. Rev. Lett. 60, 1134–1137 (1988).
[CrossRef]

Izatt, J. A.

Joyeux, D.

Kari, T.

Kartashov, V.

Kawata, S.

B. Dingel, S. Kawata, and S. Minami, “Speckle reduction with virtual incoherent laser illumination using a modified fiber array,” Optik 94, 132–136 (1993).

B. Dingel and S. Kawata, “Laser-diode microscope with fiber illumination,” Opt. Commun. 93, 27–32 (1992).
[CrossRef]

Khalfin, V.

J. Seurin, G. Xu, B. Guo, A. Miglo, Q. Wang, P. Pradhan, J. D. Wynn, V. Khalfin, W. Zou, C. Ghosh, and R. Van Leeuwen, “Efficient vertical-cavity surface-emitting lasers for infrared illumination applications,” Proc. SPIE 7952, 79520G (2011).
[CrossRef]

Kompanets, I. N.

A. L. Andreev, I. N. Kompanets, M. V. Minchenko, E. P. Pozhidaev, and T. B. Andreeva, “Speckle suppression using a liquid-crystal cell,” Quantum Electron. 38, 1166–1170 (2008).
[CrossRef]

Lemmer, U.

Lin, C. T.

J. J. Chen and C. T. Lin, “Freeform surface design for a light-emitting diode-based collimating lens,” Opt. Eng. 49, 093001 (2010).
[CrossRef]

Lowenthal, S.

Manni, J. G.

McKechnie, T. S.

T. S. McKechnie, “Speckle reduction,” in Topics in Applied Physics, J. C. Dainty, ed. (Springer-Verlag, 1975), pp. 123–170.

Migacz, J. V.

Miglo, A.

J. Seurin, G. Xu, B. Guo, A. Miglo, Q. Wang, P. Pradhan, J. D. Wynn, V. Khalfin, W. Zou, C. Ghosh, and R. Van Leeuwen, “Efficient vertical-cavity surface-emitting lasers for infrared illumination applications,” Proc. SPIE 7952, 79520G (2011).
[CrossRef]

Minami, S.

B. Dingel, S. Kawata, and S. Minami, “Speckle reduction with virtual incoherent laser illumination using a modified fiber array,” Optik 94, 132–136 (1993).

Minchenko, M. V.

A. L. Andreev, I. N. Kompanets, M. V. Minchenko, E. P. Pozhidaev, and T. B. Andreeva, “Speckle suppression using a liquid-crystal cell,” Quantum Electron. 38, 1166–1170 (2008).
[CrossRef]

Morrison, I. D.

I. D. Morrison and S. Ross, Colloidal Dispersions: Suspensions, Emulsions, and Foams (Wiley, 2002).

Nieuwenhuizen, Th. M.

M. C. W. van Rossum and Th. M. Nieuwenhuizen, “Multiple scattering of classical waves: microscopy, mesoscopy, and diffusion,” Rev. Mod. Phys. 71, 313–371 (1999).
[CrossRef]

Ouyang, G.

Pedersen, K.

Pedersen, T. G.

Petursson, P. R.

Pine, D. J.

D. J. Pine, D. A. Weitz, P. M. Chaikin, and E. Herbolzheimer, “Diffusing-wave spectroscopy,” Phys. Rev. Lett. 60, 1134–1137 (1988).
[CrossRef]

Pozhidaev, E. P.

A. L. Andreev, I. N. Kompanets, M. V. Minchenko, E. P. Pozhidaev, and T. B. Andreeva, “Speckle suppression using a liquid-crystal cell,” Quantum Electron. 38, 1166–1170 (2008).
[CrossRef]

Pradhan, P.

J. Seurin, G. Xu, B. Guo, A. Miglo, Q. Wang, P. Pradhan, J. D. Wynn, V. Khalfin, W. Zou, C. Ghosh, and R. Van Leeuwen, “Efficient vertical-cavity surface-emitting lasers for infrared illumination applications,” Proc. SPIE 7952, 79520G (2011).
[CrossRef]

Redding, B.

B. Redding, M. A. Choma, and H. Cao, “Speckle-free laser imaging using random laser illumination,” Nat. Photonics 6, 355–359 (2012).
[CrossRef]

B. Redding, M. A. Choma, and H. Cao, “Spatial coherence of random laser emission,” Opt. Lett. 36, 3404–3406 (2011).
[CrossRef]

Riechert, F.

Rigden, J. D.

J. D. Rigden and E. I. Gordon, “The granularity of scattered optical maser light,” Proc. Inst. Radio Eng. 50, 2367–2368 (1962).

Ross, S.

I. D. Morrison and S. Ross, Colloidal Dispersions: Suspensions, Emulsions, and Foams (Wiley, 2002).

Seurin, J.

J. Seurin, G. Xu, B. Guo, A. Miglo, Q. Wang, P. Pradhan, J. D. Wynn, V. Khalfin, W. Zou, C. Ghosh, and R. Van Leeuwen, “Efficient vertical-cavity surface-emitting lasers for infrared illumination applications,” Proc. SPIE 7952, 79520G (2011).
[CrossRef]

Sndergaard, T.

Tong, Z.

Trisnadi, J. I.

Tschudi, T.

Urey, H.

Van Leeuwen, R.

J. Seurin, G. Xu, B. Guo, A. Miglo, Q. Wang, P. Pradhan, J. D. Wynn, V. Khalfin, W. Zou, C. Ghosh, and R. Van Leeuwen, “Efficient vertical-cavity surface-emitting lasers for infrared illumination applications,” Proc. SPIE 7952, 79520G (2011).
[CrossRef]

van Rossum, M. C. W.

M. C. W. van Rossum and Th. M. Nieuwenhuizen, “Multiple scattering of classical waves: microscopy, mesoscopy, and diffusion,” Rev. Mod. Phys. 71, 313–371 (1999).
[CrossRef]

Wang, K.

Wang, L.

Wang, Q.

J. Seurin, G. Xu, B. Guo, A. Miglo, Q. Wang, P. Pradhan, J. D. Wynn, V. Khalfin, W. Zou, C. Ghosh, and R. Van Leeuwen, “Efficient vertical-cavity surface-emitting lasers for infrared illumination applications,” Proc. SPIE 7952, 79520G (2011).
[CrossRef]

Weitz, D. A.

D. J. Pine, D. A. Weitz, P. M. Chaikin, and E. Herbolzheimer, “Diffusing-wave spectroscopy,” Phys. Rev. Lett. 60, 1134–1137 (1988).
[CrossRef]

Williams, L. A.

A. G. Geri and L. A. Williams, “Perceptual assessment of laser-speckle contrast,” J. Soc. Inf. Disp. 20, 22–27 (2012).
[CrossRef]

Wynn, J. D.

J. Seurin, G. Xu, B. Guo, A. Miglo, Q. Wang, P. Pradhan, J. D. Wynn, V. Khalfin, W. Zou, C. Ghosh, and R. Van Leeuwen, “Efficient vertical-cavity surface-emitting lasers for infrared illumination applications,” Proc. SPIE 7952, 79520G (2011).
[CrossRef]

Xu, G.

J. Seurin, G. Xu, B. Guo, A. Miglo, Q. Wang, P. Pradhan, J. D. Wynn, V. Khalfin, W. Zou, C. Ghosh, and R. Van Leeuwen, “Efficient vertical-cavity surface-emitting lasers for infrared illumination applications,” Proc. SPIE 7952, 79520G (2011).
[CrossRef]

Yan, X.

Zou, W.

J. Seurin, G. Xu, B. Guo, A. Miglo, Q. Wang, P. Pradhan, J. D. Wynn, V. Khalfin, W. Zou, C. Ghosh, and R. Van Leeuwen, “Efficient vertical-cavity surface-emitting lasers for infrared illumination applications,” Proc. SPIE 7952, 79520G (2011).
[CrossRef]

Appl. Opt. (4)

J. Opt. Soc. Am. (1)

J. Opt. Soc. Am. A (1)

J. Soc. Inf. Disp. (1)

A. G. Geri and L. A. Williams, “Perceptual assessment of laser-speckle contrast,” J. Soc. Inf. Disp. 20, 22–27 (2012).
[CrossRef]

Nat. Photonics (1)

B. Redding, M. A. Choma, and H. Cao, “Speckle-free laser imaging using random laser illumination,” Nat. Photonics 6, 355–359 (2012).
[CrossRef]

Opt. Commun. (1)

B. Dingel and S. Kawata, “Laser-diode microscope with fiber illumination,” Opt. Commun. 93, 27–32 (1992).
[CrossRef]

Opt. Eng. (1)

J. J. Chen and C. T. Lin, “Freeform surface design for a light-emitting diode-based collimating lens,” Opt. Eng. 49, 093001 (2010).
[CrossRef]

Opt. Express (2)

Opt. Lett. (5)

Optik (1)

B. Dingel, S. Kawata, and S. Minami, “Speckle reduction with virtual incoherent laser illumination using a modified fiber array,” Optik 94, 132–136 (1993).

Phys. Rev. Lett. (1)

D. J. Pine, D. A. Weitz, P. M. Chaikin, and E. Herbolzheimer, “Diffusing-wave spectroscopy,” Phys. Rev. Lett. 60, 1134–1137 (1988).
[CrossRef]

Proc. Inst. Radio Eng. (1)

J. D. Rigden and E. I. Gordon, “The granularity of scattered optical maser light,” Proc. Inst. Radio Eng. 50, 2367–2368 (1962).

Proc. SPIE (1)

J. Seurin, G. Xu, B. Guo, A. Miglo, Q. Wang, P. Pradhan, J. D. Wynn, V. Khalfin, W. Zou, C. Ghosh, and R. Van Leeuwen, “Efficient vertical-cavity surface-emitting lasers for infrared illumination applications,” Proc. SPIE 7952, 79520G (2011).
[CrossRef]

Quantum Electron. (1)

A. L. Andreev, I. N. Kompanets, M. V. Minchenko, E. P. Pozhidaev, and T. B. Andreeva, “Speckle suppression using a liquid-crystal cell,” Quantum Electron. 38, 1166–1170 (2008).
[CrossRef]

Rev. Mod. Phys. (1)

M. C. W. van Rossum and Th. M. Nieuwenhuizen, “Multiple scattering of classical waves: microscopy, mesoscopy, and diffusion,” Rev. Mod. Phys. 71, 313–371 (1999).
[CrossRef]

Other (3)

I. D. Morrison and S. Ross, Colloidal Dispersions: Suspensions, Emulsions, and Foams (Wiley, 2002).

J. W. Goodman, “Optical methods for suppressing speckle,” in Speckle Phenomena in Optics (Roberts, 2007), pp. 141–186.

T. S. McKechnie, “Speckle reduction,” in Topics in Applied Physics, J. C. Dainty, ed. (Springer-Verlag, 1975), pp. 123–170.

Cited By

OSA participates in CrossRef's Cited-By Linking service. Citing articles from OSA journals and other participating publishers are listed here.

Alert me when this article is cited.


Figures (3)

Fig. 1.
Fig. 1.

(a) Photograph of a colloidal solution in a clear glass cuvette. A CW laser at 532 nm is coupled to a SMF, and the output from the fiber tip is incident from free space above the colloidal solution of TiO2 particles in water (the particle density is 2×1010cm3). The incident light is primarily scattered at the top of the solution with very little propagating through the base of the cuvette. (b) The same colloidal solution in a glass cuvette with the fiber tip delivering the laser light deep inside the colloidal solution. In this case, emission is seen leaving the base of the cuvette as well as the sides. (c) The same colloidal solution is contained in a cuvette with white paint covering the sides. Again a fiber is used to deliver the laser light deep into the colloidal solution. Strong output is observed through the base of the cuvette. (d) Schematic of the setup shown in (c). The fiber tip is at a distance L from the base of the cuvette, and the total thickness of the solution in the cuvette is t. After multiple scattering in the colloidal solution, most of the diffusive light escapes through the base of the cuvette, and the output has an angular distribution similar to a Lambertian source. (e) Fraction of light collected by the detector shown in (d) as the colloidal solution was gradually added to the cuvette. The fiber tip was fixed 4 mm from the base of the cuvette. Initially, the transmission decreases as colloidal solution is added until the tip of the fiber is submerged. Adding solution above the fiber tip increases the transmission until it saturates at 0.18. (f) Measured transmission in (c) was compared to that in (a). The fraction of light collected by the detector (collection efficiency) is denoted on the left axis, and the calculated transmission assuming the transmitted light follows a Lambertian distribution is shown on the right axis. The solid blue circles represent the transmission as the fiber was moved away from the cuvette base inside the solution. In this experiment, 30mm of solution was placed in the cuvette to ensure the transmission was saturated as observed in (e). The open red circles represent the transmission through different thicknesses of the same colloidal solution contained in an unpainted cuvette with the laser beam incident from free space above the solution.

Fig. 2.
Fig. 2.

(a) Schematic of the experimental setup used to measure speckle contrast. The diffused laser emission was collimated by a lens and incident onto a scattering film (S). The transmitted light was imaged onto a CCD camera by an objective lens (Obj). (b) Without a colloidal solution, speckle is observed with contrast C=0.34. (c) Using the fiber-coupled colloidal solution (L=5mm in a painted cuvette), speckle is suppressed with C=0.032. (d) Measured speckle contrast as a function of the distance L between the fiber tip and the base of the cuvette. The integration time was fixed at 129 μs. (e) Based on the speckle contrast in (d), the number of independent speckle patterns averaged during the 129 μs integration time and the decorrelation time of a speckle pattern were estimated at different L.

Fig. 3.
Fig. 3.

(a) CW laser output from the fiber-coupled colloidal solution in a painted cuvette was used to illuminate an AF chart, which was imaged in transmission through a static scattering film (S) onto a CCD camera. (b) Image of the AF chart without the colloidal solution. Speckle formation corrupted the image. (c) Image of the AF chart with the colloidal solution. The speckle contrast was greatly reduced, and the features of the AF chart are clearly visible despite the scattering film. The integration time of the CCD camera was adjusted in (b) and (c) to fully utilize the dynamic range of the CCD camera.

Metrics