Remote, noninvasive, cardio-vascular activity tracer and hard target evaluator
Inventors
Assignees
National Aeronautics and Space Administration NASA
Publication Number
US-11119072-B2
Publication Date
2021-09-14
Expiration Date
2039-08-09
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Abstract
A system for monitoring vibrations in a target region of interest may include a pulsed laser transmitter assembly, interferometric, telescope, and receiver optics, a photo-EMF detector assembly, signal conditioning/processing electronics, and a monitoring circuit/display. The detector assembly, which has a photo-EMF detector and amplifier circuits, generates an output signal indicative of the vibrations. A laser module outputs a source beam at a PRF of at least 2 Hz. A beam splitter device splits the source beam into separate interrogating and reference beams. The mirror directs the reference beam onto the photo-EMF detector for interference with a reflected return signal. The telescope optics generates an amplified return signal, and directs the amplified return signal to the photo-emf detector. The monitoring computer compares the output signal from the signal processor to a baseline to ascertain a difference therebetween, and generates a diagnostic signal indicative of the difference.
Core Innovation
A remote, non-invasive system is disclosed for monitoring the functionality of a region of interest (ROI) using reflected laser return signals. The ROI may be a designated surface area of a biological target, such as a human patient, with return signals containing information describing cardio-vascular function. The system operates using a pulsed laser transmitter, interferometric, telescope, and receiver optics, and a photo-electromotive force (photo-EMF) detector assembly to generate output signals indicative of vibrations. This approach allows detection of minute displacements caused by cardiac pulsations or other periodic motion through garments, with displacement magnitudes on the order of nanometers to femtometers.
The problem addressed is suboptimal performance of existing laser vibrometers for non-invasive monitoring of cardio-vascular activity and other vibration under the particular conditions described. Existing cardiac monitoring methods like ECG require electrodes attached directly to the patient or invasive leads, and conventional laser vibrometers are not optimized for remote, non-contact measurements through clothing or for detecting extremely minute vibrations at various body locations or hard targets. This hinders precise, non-obtrusive monitoring of cardiac mechanical function, especially at extremities or in challenging environments.
The disclosed system features a photo-EMF detector with high sensitivity, capable of detecting displacements down to about 1 picometer or less, producing electrical signals from interferometric fringe motion caused by vibrations. The system includes a pulsed laser with a pulse repetition frequency of at least 2 Hz and may be configured with a relaxed Mach-Zehnder interferometer setup to maximize sensitivity and signal-to-noise ratio. The system can operate through fabrics without requiring skin preparation and may be miniaturized into a handheld device for diverse applications including monitoring cardiac activity away from the chest cavity while the patient remains clothed.
Claims Coverage
The patent includes three independent claims covering a system and a method for monitoring vibrations in a region of interest of a monitored target. The claims specify inventive features related to the photo-EMF detector assembly, laser assembly, optical components, and signal processing technologies.
Photo-EMF detector assembly with multi-pixel Cadmium Telluride doped with transition metals
A photo-EMF detector assembly comprised of a multi-pixel device constructed from Cadmium Telluride doped with a combination of transition metals including Titanium and Chromium, optionally also Vanadium, providing the capability to generate output signals indicative of vibrations with high sensitivity via interferometric fringe motion detection.
Laser assembly with beam splitter and pulsed laser source
A laser assembly including a laser generator configured to output a source beam with a pulse repetition frequency of at least 2 Hz, a beam splitter to split the source beam into separate interrogating and reference beams, and a mirror angled to direct the reference beam onto the photo-EMF detector, enabling interferometric detection of vibrations.
Interferometric optical setup with telescope optics and return signal amplification
Telescope optics configured to amplify the return signal reflected from the region of interest and direct the amplified return signal onto the photo-EMF detector to form interferometric fringes, enhancing measurement sensitivity for minute displacements.
Monitoring circuit comparing output signals to baseline to generate diagnostics
A monitoring circuit configured to receive the output signal from the photo-EMF detector, compare it to a baseline reference to ascertain differences, and generate a diagnostic signal indicative of such differences, enabling detection and evaluation of vibrations.
Method for vibration monitoring using pulsed laser and interferometric detection
A method comprising generating a source beam at a pulse repetition frequency of at least about 10 Hz, splitting into interrogating and reference beams, directing these beams appropriately onto the ROI and photo-EMF detector, amplifying the return signal, generating output signals indicative of vibrations caused by interferometric fringes motion, and processing these signals to diagnose differences from baseline.
The claims collectively cover a highly sensitive remote monitoring system and method featuring a specialized photo-EMF multi-pixel detector doped with transition metals, a pulsed laser assembly with beam splitting and interferometric optics including signal amplification, and a diagnostic monitoring circuit. These inventive features enable non-invasive detection of minute vibrations through clothing or on hard targets with enhanced sensitivity and diagnostic capability.
Stated Advantages
Highly sensitive detection of minute vibrations down to about 1 picometer or less, enabling non-invasive monitoring of cardiac mechanical function through clothing without skin preparation.
Non-contact, remote, and non-intrusive monitoring allowing operation away from the patient's chest cavity while the patient remains clothed, facilitating use in various environments including constrained or bulky clothing situations.
Enhanced precision and early detection of cardiac function defects and other vibration-related abnormalities, with improved signal-to-noise ratio and sensitivity through an optimized interferometric setup.
Potential miniaturization into a handheld device with reduced size, weight, and power consumption, facilitating portability and wider application scenarios.
Ability to monitor both biological targets and hard targets for non-destructive evaluation, expanding the system's applicability beyond medical diagnostics to structural monitoring.
Documented Applications
Non-contact, non-invasive monitoring of cardiac mechanical function such as opening and closing cycles of the heart's chambers and valves by detecting minute displacements of patient garments at various body regions including ankles, feet, toes, neck, back, and hands.
Monitoring blood circulation and related vibrations to detect conditions such as poor circulation or latent diabetes by assessing vibration strength at peripheral body parts remotely.
Non-destructive evaluation (NDE) of hard targets including metallic or non-metallic objects like aircraft or spacecraft fuselages and wings, detecting latent defects or structural abnormalities through induced vibrations.
Remote monitoring of biological functions beyond cardiac activity, such as respiratory function, by detecting periodic motion causing vibrations in a biological target.
Use in challenging environments such as spacesuits, high temperature, reduced-oxygen, or microgravity settings for real-time biometric data acquisition.
Generation of multi-dimensional vibrational data (1D, 2D, 3D, 4D) to produce images of specific regions, enabling fast, sensitive, and cost-effective diagnosis.
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