Swept-Source Interferometry for Depth-Resolved Neural Activity Detection
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Solution Overview
Problem
Current non-invasive optical measurement techniques, such as optical coherence tomography (OCT) and interferometric Near-Infrared Spectroscopy (iNIRS), face limitations in achieving high spatial resolution and depth penetration in brain tissue due to light scattering, and struggle with detecting fast-optical signals associated with neural activity.
Innovation Solution
A non-invasive optical measurement system that employs a swept-source interferometry with a narrow spectral linewidth, using an optical source to sweep light over a wide wavelength range during brief measurement periods, and an interferometer to generate an interference light pattern with spatial and oscillation frequency components, detected by an array of optical detectors to derive intensity values and determine the depth of physiological events, such as neural activity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional optical detection techniques are used to measure neural activity in the brain, then the measurement can be performed non-invasively, but the spatial resolution is limited to centimeters due to light scattering
Solution Approach 1:
The patent replaces conventional time-domain or spectral-domain detection with frequency-domain detection using a swept-source laser. By modulating the laser frequency and detecting the phase-modulated backscattered light, the system achieves depth-resolved measurements with millimeter-scale spatial resolution through multiple scattering events, overcoming the diffusive limit of conventional optical methods
Solution Approach 2:
The patent changes the detection parameter from intensity measurement to phase measurement. By detecting the phase modulation of backscattered light caused by frequency sweeping, the system can resolve optical path length differences with micrometer precision, enabling depth discrimination despite multiple scattering events that randomize photon paths
2Measurement precision
If traditional OCT systems use coherent light to capture sub-surface images, then high z-resolution can be achieved, but the detection depth is limited because most light scatters and contributes to background noise
Solution Approach 1:
The patent converts the harmful effect of multiple scattering into a beneficial signal. Instead of rejecting scattered photons as noise, the system detects the phase modulation imprinted on scattered light during frequency sweeping. The phase information encodes the optical path length, allowing depth resolution even when photons undergo multiple scattering events
Solution Approach 2:
The patent introduces frequency modulation as an intermediary to encode depth information. By sweeping the laser frequency and detecting the resulting phase modulation in backscattered light, the system creates a measurable signal that carries depth information through scattering media, bridging the gap between the light source and the detected signal
3Ease of operation
If optical imaging methods are used to detect neural activity, then the system can be scaled to wearable or portable form factors, but the temporal resolution for detecting fast-optical signals is insufficient
Solution Approach 1:
The patent uses periodic frequency sweeping of the laser source to encode temporal information. By rapidly sweeping the laser frequency at defined rates and detecting the phase-modulated signal, the system achieves high temporal resolution for fast-optical signals while maintaining a compact, portable form factor without large magnets or magnetic shielding
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
This approach enhances data throughput and light collection efficiency, enabling higher signal-to-noise ratio and detection speed, allowing for the detection of neural activity at deeper tissue depths with improved spatial resolution and temporal resolution.
Implementation Method 1
an interferometer to generate an interference light pattern with spatial and oscillation frequency components
Implementation Method 2
light, which scatters many times inside brain, skull, dura, pia, and skin tissues
Implementation Method 3
combining, during each of the measurement period(s), the physiological-encoded signal light and the reference light into an interference light pattern
Data Source
AI summary
An optical source sweeps a source light over an optical wavelength range. An interferometer splits the source light into sample light and reference light, delivers the sample light into an anatomical structure, such that the sample light is scattered by the anatomical structure, resulting in physiological-encoded signal light that exits the anatomical structure, and combines the signal light and the reference light into an interference light pattern having an array of spatial components and a plurality of oscillation frequency components. An optical detector array detects intensity values of the array of spatial components. A processor derives an array of intensity values of each oscillation frequency component from the detected spatial component intensity value array, reduces each derived oscillation frequency component intensity value array to a single frequency component intensity value, and determines a depth of a physiological event in the anatomical structure based on the reduced frequency component intensity values.