| Issue |
J. Eur. Opt. Soc.-Rapid Publ.
Volume 14, Number 1, 2018
|
|
|---|---|---|
| Article Number | 27 | |
| Number of page(s) | 7 | |
| DOI | https://doi.org/10.1186/s41476-018-0095-7 | |
| Published online | 27 November 2018 | |
Research
Homogenization with coherent light illuminated beam shaping diffusers for vision applications: spatial resolution limited by speckle pattern
1
Department of Optics and Quantum Electronics, University of Szeged, Dóm tér 9, H-6720, Szeged, Hungary
2
MTA-SZTE Research Group on Photoacoustic Spectroscopy, University of Szeged, Dóm tér 9, H-6720, Szeged, Hungary
Received:
23
August
2018
Accepted:
16
November
2018
Background: Homogenizing properties of beam shaping diffusers illuminated with coherent laser light was studied with special regard on their use in vision applications.
Experimental: Two diffusers projecting circular pattern at different scattering angles (Thorlabs Engineered Diffuser™) were illuminated with different spatial intensity distribution (elliptical Gaussian, nearly flat-top and granular multimode fiber output, respectively) collimated beams.
Results: The intensity distribution measured at high angular resolution with a CMOS sensor revealed the granular (speckle) pattern of the projected light having contrast of nearly 1. The smallest speckle size (highest speckle density) could be obtained at the largest aperture size using nearly flat-top and multimode fiber illumination.
Conclusion: As an important measure of the homogeneity for vision applications the apparent local contrast was calculated as the function of the spatial averaging. Although, the homogeneity requirements depend on the actual application, the usability of such diffusers in combination with coherent light sources is in general strongly limited in megapixel resolution imaging applications, unless time-varying speckle averaging methods can be applied.
Key words: Beam homogenization / Beam shaping diffuser / Speckle pattern
© The Author(s) 2018
Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.
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