Photoacoustic Imaging Device Using Continuous Wave Laser Modulation
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Solution Overview
Problem
Current photoacoustic imaging technologies face challenges in achieving high-resolution imaging at a low cost, particularly in the depth direction, due to the need for expensive pulse lasers in existing multiphoton excitation methods.
Innovation Solution
A photoacoustic imaging device utilizing a semiconductor laser light source emitting continuous waves, combined with a frequency shifting unit and a variable focus lens, to generate intensity-modulated light that induces thermal expansion and acoustic waves, allowing for high-resolution imaging without the need for expensive pulse lasers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a short pulse laser is used to generate acoustic waves through instantaneous thermal expansion, then imaging depth information can be obtained via arrival time, but the device cost becomes high
Solution Approach 1:
The patent changes the laser operating parameters from pulsed mode to continuous wave mode with intensity modulation. By modulating the intensity of continuous laser light at ultrasonic frequencies (MHz band), the system generates acoustic waves without requiring expensive short pulse lasers, thereby reducing device cost while maintaining imaging capability
Solution Approach 2:
The patent applies periodic intensity modulation to the continuous laser beam at ultrasonic frequencies. This periodic modulation creates rhythmic thermal expansion in the tissue, generating acoustic waves at the modulation frequency. The periodic nature of this action enables depth encoding through frequency analysis rather than time-of-flight measurement
2Ease of manufacture
If a continuous wave laser with intensity modulation is used instead of short pulse laser, then device cost is reduced, but depth determination by arrival time becomes impossible
Solution Approach 1:
The patent transitions from time-domain depth encoding (arrival time) to frequency-domain depth encoding. By modulating the continuous laser at different ultrasonic frequencies and analyzing the received signals in the frequency domain, depth information is extracted through spectral analysis rather than temporal measurement, adding a frequency dimension to the imaging process
Solution Approach 2:
The patent replaces the temporal measurement mechanism (time-of-flight) with a frequency-based detection mechanism. Instead of measuring when acoustic waves arrive, the system modulates light intensity at ultrasonic frequencies and detects the resulting acoustic signals through their frequency characteristics, substituting mechanical time measurement with optical frequency modulation
3Device complexity
If resolution in depth direction is determined by acoustic wave properties, then imaging is simplified, but high resolution cannot be achieved
Solution Approach 1:
The patent makes the light source perform multiple functions: it serves as both the illumination source and the acoustic wave generator through intensity modulation. The modulated continuous laser simultaneously provides optical excitation and acoustic signal generation, eliminating the need for separate pulsed laser systems and complex acoustic transducers while achieving high depth resolution
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 high-resolution photoacoustic imaging at a lower cost by using continuous wave lasers and a variable focus lens to modulate light frequencies, generating acoustic waves with high specificity and resolution in the depth direction.
Implementation Method 1
a frequency shifting unit configured to shift a frequency of light by causing a Doppler effect
Implementation Method 2
The photoacoustic effect is a phenomenon that molecules having absorbed the light energy releases heat and an acoustic wave is generated as a result of volume expansion due to the heat
Implementation Method 3
an acoustic wave is generated as a result of volume expansion due to the heat
Data Source
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AI summary
The objective of the invention is to make it possible to provide a high-resolution photoacoustic imaging device at low cost. This photoacoustic wave detecting device is provided with: a beam splitter (111) which splits emitted light from a light source; an optical physical property shifting unit (120) which changes at least one physical property of the split beams in such a way that the split beams interfere with one another; a lens (140) into which each split beams enters parallel to the optical axis; and an acoustic detecting unit (150) which detects an acoustic wave generated in a region of an observation target at the focal point of the lens (140).