PARS-OCT Imaging System Non-Contact Subsurface Resolution

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Solution Overview

Problem

Conventional photoacoustic imaging techniques require physical coupling to the sample, making them unsuitable for clinical applications such as ophthalmic imaging, intraoperative imaging, and endoscopic procedures due to limitations in sensitivity and accessibility.

Innovation Solution

The development of thermally enhanced photoacoustic remote sensing (TE-PARS) systems, which utilize excitation, signal enhancement, and interrogation beams focused below the sample surface to generate and detect photoacoustic signals non-contactually, enhancing sensitivity and resolution beyond the optical diffraction limit through thermal and pressure modulation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If conventional photoacoustic techniques are used, then image formation is achieved, but physical coupling to the sample is required which limits accessibility for clinical applications

Engineering Contradiction:

ImproveAccessibility for clinical applicationsVSAvoidPhysical coupling requirement

Core Design Contradiction:

Ease of operationVSDevice complexity

Solution Approach 1:

The patent replaces the mechanical coupling system (acoustic transducers requiring physical contact with the sample) with an optical detection system. The PARS technique uses optical beams to both excite the sample and detect the photoacoustic signals remotely through optical property changes, eliminating the need for mechanical coupling and enabling non-contact imaging for ophthalmic and endoscopic applications.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Measurement precision

If conventional photoacoustic techniques are used, then optical absorption contrast is visualized, but sensitivity is insufficient for subsurface imaging

Engineering Contradiction:

ImproveSensitivity for subsurface imagingVSAvoidSignal strength from subsurface structures

Core Design Contradiction:

Measurement precisionVSLoss of information

Solution Approach 1:

The patent employs periodic modulation of the excitation beam intensity or frequency to generate photoacoustic signals at specific frequencies. This periodic action allows the use of lock-in detection or frequency-domain analysis to extract weak subsurface signals from background noise, significantly improving sensitivity for imaging structures beneath the sample surface.

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The patent introduces an intermediary detection mechanism that monitors optical property changes (refractive index, absorption) caused by photoacoustic excitation. This intermediary approach allows indirect detection of subsurface structures through their effect on the optical path, enhancing sensitivity without requiring direct acoustic coupling to deep structures.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Measurement precision

If optical resolution photoacoustic microscopy is used, then high resolution imaging is achieved, but the optical focus must be tightly controlled which limits depth penetration

Engineering Contradiction:

ImproveImage resolutionVSAvoidDepth penetration capability

Core Design Contradiction:

Measurement precisionVSLength of stationary object

Solution Approach 1:

The patent separates the excitation and detection focal points in space, allowing the excitation beam to be focused at one depth while the detection beam samples a different region. This dimensional separation enables high-resolution imaging at the excitation focus while simultaneously monitoring subsurface structures at different depths, overcoming the trade-off between resolution and penetration depth.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

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

Enables non-contact, high-resolution imaging of subsurface structures with improved sensitivity and contrast, facilitating applications in ophthalmic and endoscopic imaging by leveraging thermal and pressure-induced refractive index changes for enhanced photoacoustic signal generation and detection.

Implementation Method 1

nanosecond or picosecond laser pulses are directed into a sample causing the generation of thermo-elastic induced acoustic waves

Methodology Applied

Scientific EffectPhotoacoustic effect: Photoacoustic Effect

Implementation Method 2

causing the generation of thermo-elastic induced acoustic waves

Methodology Applied

Scientific EffectThermo-elastic effect:

Implementation Method 3

a signal enhancement beam or collection of beams configured to modify the observation or generation of temperature and pressure signals

Methodology Applied

Scientific EffectOptical heating: Heating

Implementation Method 4

leveraging thermal and pressure-induced refractive index changes for enhanced photoacoustic signal generation and detection

Methodology Applied

Scientific EffectThermal refractive index change:

Implementation Method 5

leveraging thermal and pressure-induced refractive index changes for enhanced photoacoustic signal generation and detection

Methodology Applied

Scientific EffectPressure refractive index change:

Data Source

PatentUS11122978B1PARS imaging methods

Publication Date: 2021.09.21 ILLUMISONICS INC

AI summary

A dual-modality photoacoustic remote sensing combined with optical coherence tomography (PARS-OCT) system for visualizing details in a sample, the system comprising one or more light sources configured to generate (1) one or more excitation beams configured to generate signals in the sample at one or more first locations below a surface of the sample; (2) one or more interrogation beams incident on the sample at one or more second locations; (3) a sample beam; and (4) a reference beam.