Special Section on Speckle-Based Metrology

Accuracy in dynamic laser speckle: optimum size of speckles for temporal and frequency analyses

[+] Author Affiliations
Roberto A. Braga, Jr.

Universidade Federal de Lavras, Dep. Engenharia, CEDIA, Lavras, Minas Gerais 37200-000, Brazil

Rolando J. González-Peña

Universitat de València, Dep. Fisiología, Unidad de Biofísica y Física Médica, Facultad de Medicina y Odontología, Avda. Blasco Ibáñez, 15, Valencia, Spain

Opt. Eng. 55(12), 121702 (May 11, 2016). doi:10.1117/1.OE.55.12.121702
History: Received February 26, 2016; Accepted April 18, 2016
Text Size: A A A

Abstract.  The dynamic laser-speckle phenomenon has been used as a potential tool to monitor the activity of many biological and nonbiological samples; however, a key tailoring of the experimental configuration must be taken into account to avoid wrong measurements, since the general rules addressed to speckle as information cannot be directly adopted in dynamic laser-speckle monitoring. The speckle/pixel size ratio is provided by the f-number and by the magnification of the macro lens, and attention is mainly directed toward adjusting a speckle/pixel ratio higher than 1. However, a speckle/pixel ratio much higher than one does not mean an optimum adjustment. This work tested different apertures with fixed magnification yielding to monitor a drying paint process. The outcomes were evaluated in the time and frequency domains. The highest speckle/pixel size ratio was not the best to monitor the process using the dynamic laser speckle under frequency analysis. Tailoring of the devices must take into account the optimum speckle/pixel size ratio, which could vary depending on the application, and the known Nyquist theorem cannot be considered as a sufficient condition since the setup of the optical camera with its macro and iris must also be adjusted in accordance with the frequency response.

Figures in this Article
© 2016 Society of Photo-Optical Instrumentation Engineers

Topics

Lasers ; Speckle ; Apertures

Citation

Roberto A. Braga, Jr. and Rolando J. González-Peña
"Accuracy in dynamic laser speckle: optimum size of speckles for temporal and frequency analyses", Opt. Eng. 55(12), 121702 (May 11, 2016). ; http://dx.doi.org/10.1117/1.OE.55.12.121702


Access This Article
Sign in or Create a personal account to Buy this article ($20 for members, $25 for non-members).

Some tools below are only available to our subscribers or users with an online account.

Related Content

Customize your page view by dragging & repositioning the boxes below.

Related Book Chapters

Topic Collections

Advertisement
  • Don't have an account?
  • Subscribe to the SPIE Digital Library
  • Create a FREE account to sign up for Digital Library content alerts and gain access to institutional subscriptions remotely.
Access This Article
Sign in or Create a personal account to Buy this article ($20 for members, $25 for non-members).
Access This Proceeding
Sign in or Create a personal account to Buy this article ($15 for members, $18 for non-members).
Access This Chapter

Access to SPIE eBooks is limited to subscribing institutions and is not available as part of a personal subscription. Print or electronic versions of individual SPIE books may be purchased via SPIE.org.