Multi-spectral laser speckle contrast images using a wavelength-swept laser

Abstract

A multi-spectral laser speckle contrast imaging (MS-LSCI) system is proposed using only a single wavelength-swept laser, which provides both highly coherent and multi-spectral outputs to simultaneously generate laser speckle contrast images and multi-spectral images, respectively. Using a laser light swept from 770 to 821 nm at a repetition rate of 5 Hz and a CCD camera of 335 fps, 67 multi-spectral frame images are acquired in 0.76 nm wavebands over 51 nm spectral range. The spectral sub-windowing method of single wavelength-swept laser source is used to solve the lack of spectral information from a few individual light sources, which is a limitation of conventional MS-LSCI systems. In addition to the speckle flow index from the LSCI frames, the multi-spectrally encoded images can generate additional images of spectral absorbance. To further examine the performance of the MS-LSCI system, an in vivo cuff-induced ischemia experiment was conducted to show the real-time imaging of hemodynamic and blood oxygen saturation changes simultaneously over the entire 2.5 cm × 4.5 cm field of view.

Optical Monitoring of Microplastics Filtrated from Wastewater Sludge and Suspended in Ethanol

“…C has values ranging from 0 to 1 for undeveloped and fully developed speckles, respectively. It has a long history of applications ranging from surface roughness characterization [ 21 , 24 ] to flow rate determination [ 25 ]. In this study, we employed it in the qualitative identification of the presence of microplastics.…”

Hydrofluoroether Impurities—Chemical Detection Using a Deep Learning Laser Speckle Contrast Evolving Spiking Neural Network

“…Fig. 1 shows the attributes of monochromatic lasers that will be used to encode the laser from its original images with SC properties, using the mean intensity approach [38] to spike train encoding of rank order population (ROP) by [39] . The encoding approach is to amplify the spike train domain before FE layer.…”

“…Laser Speckle Contrast Imaging (LSCI) is a sophisticated and useful imaging method that uses the speckles of a highly coherent light source (laser source), that are randomly generated on the image sensor. This imaging technique is regarded as an economical method to obtain information on the movement or flow of the target medium [38] .…”

“…The speckle contrast can be determined by analyzing the reflection intensity of the image [38] [43] . The speckle contrast, K, can be calculated using Equation (1) .…”