Understanding the exposure-time effect on speckle contrast measurement for laser projection with rotating diffuser

  • Koji SuzukiEmail author
  • Shigeo Kubota
Special Section: Regular Paper Laser Display and Lighting Conference (LDC’ 18), Yokohama, Japan
Part of the following topical collections:
  1. Laser Display and Lighting Conference (LDC' 18), Yokohama, Japan


To evaluate the influence of observer’s exposure time over speckle noise of laser displays, we developed the high-speed measurement method which can measure speckle contrast over a wide range of exposure time without adjusting the brightness of laser displays in our previous work. We attempted to observe the exposure-time effect in speckle contrast for several commercially available laser displays using this method. However, their speckle contrasts were nearly constant at various exposure times in our experiments, although it is a more reasonable argument that the speckle contrast of laser display equipped with a temporally-averaging speckle-reduction device is dependent on the exposure time. Since we assumed that the temporal averaging factors of their laser displays were underestimated, we prototyped a speckle-reduction device using an intentionally slow-rotating diffused plate and measured the speckle contrast for a laser projection applying this device in this work. The speckle contrast was increased at the lower linear velocity of the diffused plate than 3.8 mm/s when the exposure time was fixed at the human response time. And, the speckle contrast was increased in the region of short exposure time when the linear velocity was fixed at 0.12, 0.47 and 1.9 mm/s. By analyzing the cross-correlation and the speckle average grain size, we confirmed that this phenomenon was caused by the exposure-time effect. In addition, we verified the relationship between the linear velocity, the exposure time and the temporal averaging factor by comparing the measurement results with theoretical fitting function.


Speckle contrast Exposure time Laser Speckle-reduction device Diffused plate Linear velocity 


Compliance with ethical standards

Conflict of interest

On behalf of all authors, the corresponding author states that there is no conflict of interest.


  1. 1.
    Kubota, S., Goodman, J.W.: Very efficient speckle contrast reduction realized by moving diffuser device. Appl. Opt. 49(23), 4385–4391 (2010)ADSCrossRefGoogle Scholar
  2. 2.
    Fukui, T., Ito, K., Suzuki, K., Tokita, H., Furukawa, Y., Kubota, S.: Effective calibration method for absolute speckle contrast measurement. In: 1st Laser display conf. dig. tech. pap. LDC8-3, laser display conference, Yokohama: (2012)Google Scholar
  3. 3.
    Suzuki, K., Fukui, T., Kubota, S., Furukawa, Y.: Verification of speckle contrast measurement interrelation with observation distance. Opt. Rev. 21(1), 94–97 (2014)CrossRefGoogle Scholar
  4. 4.
    Fukui, T., Suzuki, K., Kubota, S.: speckle contrast measurement in arbitrary observation distance. In: Proc. IDW’13, PRJ4-1, 1251–1254, Sapporo (2013)Google Scholar
  5. 5.
    Kubota, S.: Simulating the human eye in measurements of speckle from laser-based projection display. Appl. Opt. 53(17), 3814–3820 (2014)ADSCrossRefGoogle Scholar
  6. 6.
    Fukui, T., Suzuki, K., Kubota, S.: Speckle measurement of laser display by means of simulating to human eye perception. In: Proc. IDW’14, PRJ3-2, 1094–1097, Niigata: (2014)Google Scholar
  7. 7.
    The Illuminating Engineering Institute of Japan: Hikari No Keisoku Manual (Light Measurement Manual), p. 404. Nihon Riko Shuppankai, Tokyo (1990) (in Japanese)Google Scholar
  8. 8.
    Suzuki, K., Kubota, S.: Understanding the exposure-time effect on speckle contrast measurements for laser displays. Opt. Rev. 25(1), 131–139 (2018)CrossRefGoogle Scholar
  9. 9.
    Suzuki, K., Kubota, S.: Understanding the exposure-time effect on speckle contrast measurement for laser projection with rotating diffuser. In: 7th Laser display and lighting conf. dig. tech. pap. LDCp9-11, laser display and lighting conference, Yokohama (2018)Google Scholar
  10. 10.
    Xu, M., Shi, Y., Tang, G., Liu, J., Chen, X.: Speckle characterization in laser projector display. World academy of science, engineering and technology. Int. J. Math. Comput. Phys. Electri. Comput. Eng. 6(3), 261–264 (2012)Google Scholar
  11. 11.
    Kurashige, M., Ishida, K., Takanokura, T., Ohyagi, Y., Watanabe, M.: The evaluation of speckle contrast with variable speckle generator. J. Soc. Info. Display 19/9, 631–638 (2011)CrossRefGoogle Scholar
  12. 12.
    Kuwata, M., Sasagawa, T., Kojima, K., Michimori, A., Sugiura, H., Hirano, Y., Endo, T.: Reducing speckle in laser displays with moving screen system. J. Image Inform. Telev. Eng. 65(2), 224–228 (2011) [in Japanese]Google Scholar
  13. 13.
    Li, D., Kelly, D.P., Sheridan, J.T.: Speckle suppression by doubly scattering system. Appl. Opt. 52(35), 8617–8626 (2013)ADSCrossRefGoogle Scholar
  14. 14.
    Tomita, Y., Suzuki, K., Fukui, T., Tokita, T., Kubota, S.: Nonuniform intensity distribution of the scattered light by moving diffuser across projection lens pupil and its influence in speckle reduction. Opt. Rev. 21(1), 90–93 (2014)CrossRefGoogle Scholar
  15. 15.
    Goodman, J.W.: Speckle phenomena in optics. Roberts & Company, Colorado (2007)Google Scholar
  16. 16.
    Kinoshita, J., Takamori, A., Yamamoto, K., Kuroda, K., Suzuki, K.: Image resolution of raster-scan laser mobile projectors considering color speckle effects. In: 7th laser display and lighting conf. dig. tech. pap. LDC6-2, laser display and lighting conference, Yokohama (2018)Google Scholar

Copyright information

© The Optical Society of Japan 2018

Authors and Affiliations

  1. 1.#203, Kawasaki Business Incubation CenterOxide CorporationKawasakiJapan

Personalised recommendations