Challenges to apply the biospeckle laser technique in the field

Abstract

Biospeckle laser, or dynamic laser speckle, is used as a technique when its outcomes are useful to monitor activity of the illuminated sample. The term “bio” means the relation of the activity with biological material, and the adoption of the dynamic laser speckle has been reported since 1970s, initially in blood flow monitoring. The range of applications improved along the years from medicine to agriculture, food and other areas. However, despite the increase of applications, there are some limits or challenges that are necessary to overcome in order to make this technique useful far from the optical laboratories. The instability of the solidstate lasers, used to reduce the size of the setup, as well as the influence of the external light and vibration can compromise the results and are some examples of the limits found. The standardization of the procedures to maintain the repeatability is another issue that must be faced, associated to the portability and accessibility of the devices. This work presents the state of the art in the area of biospeckle laser application and discuss the efforts that have to be taken to make it accessible, robust and reliable. A proposal of a free library in M code (Matlab and Octave) with its tutorial is presented and shared as a way to start the standardization of the image analysis. The library has a collection of numerical and graphical codes, as well as frequency filters to isolate phenomena. A list of applications is presented associated to the advances regarding the new born experimental configurations, mainly related to the digital devices used to acquire and to analyze the data.