Laser Speckle Imaging Geometry for Reflection-Free Flow Measurement
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Solution Overview
Problem
Conventional laser speckle imaging (LSI) techniques are susceptible to motion artifacts and surface reflections, leading to erroneous results due to specular and diffuse reflections, shallow depth penetration, and low sampling of dynamic particles, which affect the accuracy of blood flow and particle movement measurements.
Innovation Solution
A system comprising a light source and detector affixed to a structure that maintains a fixed spatial relationship with the sample, excluding surface reflections and focusing on multiply-scattered photons, using a processor to calculate speckle contrast and determine particle movement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If conventional LSI uses independent mounting of imaging components and sample, then alignment flexibility is improved, but motion artifact susceptibility increases
Solution Approach 1:
The patent combines the light source, detector, and sample mounting into a single integrated imaging system where all components are rigidly mounted together. This eliminates relative motion between components and the sample, preventing motion artifacts while maintaining alignment through the integrated design.
2Use of energy by moving object
If LSI illuminates the sample surface directly, then illumination efficiency is improved, but surface reflection interference increases
Solution Approach 1:
The patent converts the harmful surface reflections into a useful geometric constraint. By positioning the detector at a specific angle relative to the light source, the system uses the law of reflection to direct surface reflections away from the detector, thereby eliminating interference while maintaining efficient illumination of the sample.
3Measurement precision
If detector is positioned to capture scattered light, then particle detection capability is improved, but surface reflection detection increases
Solution Approach 1:
The patent employs asymmetric positioning of the detector at a specific angle relative to the light source and sample surface. This asymmetric geometry creates different detection paths for scattered light from particles versus reflected light from the surface, allowing the detector to capture particle scattering signals while excluding surface reflections through angular separation.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enhances the accuracy and depth penetration of particle movement measurements by reducing motion artifacts and surface reflections, providing more reliable and informative signals about the flow of light scattering particles.
Implementation Method 1
uses a coherent laser source to illuminate a sample of light scattering particles, and images the scattered light using a multi-pixel detector
Implementation Method 2
The sensor records the so-called 'speckle' pattern, produced by light interference, as the scattered coherent light recombines onto the detection element
Implementation Method 3
specular reflection is the process by which a mirrored surface reflects light
Implementation Method 4
diffuse reflection is the process by which matte objects, such as a sheet of binder paper, reflect light
Data Source
Figure 1A~1B
Figure 1C~1D
Figure 2A~2B
AI summary
Devices, systems, and methods are disclosed for improved laser speckle imaging of samples, such as vascularized tissue, for the determination of the rate of movement of light scattering particles within the sample. The system includes a structure adjoining a light source and a photo-sensitive detector. The structure can be positioned adjacent the sample (e.g., coupled to the sample) and configured to orient the light source and detector relative the sample such that surface reflections, including specular reflections and diffuse reflections, are discouraged from entering the detection field of the detector. The separation distance along the structure between the light source and the detector may further enable selective depth penetration into the sample and biased sampling of multiply scattered photons. The system includes an operably coupled processor programmed to derive contrast metrics from the detector and to relate the contrast metrics to a rate of movement of the light scattering particles.