Photoacoustic Probe Optical Reflection Layer Noise Reduction
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Solution Overview
Problem
The existing photoacoustic probes using capacitive micromachined ultrasonic transducers face issues with noise due to light-induced photoacoustic waves on the receiving surface, which can be exacerbated by solvent cracks and scratches in the optical reflection layer, leading to increased noise and reduced performance.
Innovation Solution
A photoacoustic probe configuration where the optical reflection layer is formed on a support layer with an acoustic matching layer, and a protection layer is added to prevent the acoustic medium from penetrating and causing cracks, while maintaining the mechanical properties of the vibration film.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the optical reflection layer is formed directly on the vibration film, then light reflection efficiency is improved, but the spring constant and deformation amount of the vibration film vary, degrading transducer performance
Solution Approach 1:
The optical reflection layer is separated from the vibration film by introducing a support layer as an intermediate substrate. This segmentation allows the reflection layer to be formed on the support layer rather than directly on the vibration film, preventing variations in spring constant and deformation amount while maintaining light reflection efficiency.
Solution Approach 2:
A support layer is introduced as an intermediary between the vibration film and the optical reflection layer. This mediator layer provides a stable substrate for forming the reflection layer, preventing direct contact that would cause mechanical property variations in the vibration film.
2Productivity
If the probe is used in acoustic medium without protection layer, then acoustic wave transmission is maintained, but solvent cracks occur in the support layer causing light leakage and increased noise
Solution Approach 1:
A protection layer is formed as a thin film over the optical reflection layer to provide environmental protection. This thin film barrier prevents solvent cracks and chemical agent damage while maintaining acoustic wave transmission properties, thereby reducing noise from light leakage.
Solution Approach 2:
The protection layer is formed in advance before the probe is exposed to the acoustic medium and potential chemical agents. This beforehand protective measure prevents solvent cracks and environmental damage before they can occur, ensuring reliable operation.
3Strength
If adhesive is used to adhere vibration film to support layer with optical reflection layer, then bonding strength is improved, but stress is applied to the support layer causing pinholes and scratches
Solution Approach 1:
The adhesive layer is removed from the system by enabling direct bonding between the vibration film and support layer through acoustic welding or other adhesive-free joining methods. This extraction eliminates the source of stress that causes pinholes and scratches in the support layer.
Solution Approach 2:
Chemical bonding using adhesive is replaced with a mechanical or acoustic bonding method that does not require a separate adhesive layer. This substitution eliminates the stress concentration and chemical compatibility issues that lead to support layer degradation.
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 configuration reduces noise by preventing solvent cracks and scratches, ensuring stable operation and accurate signal detection of photoacoustic waves, even with pinholes or scratches on the optical reflection layer.
Implementation Method 1
an optical reflection layer which reflects light with which an object has been irradiated
Implementation Method 2
photoacoustic waves are caused by irradiating the inside of an object with light (electromagnetic waves)... a capacitive electromechanical transducer
Implementation Method 3
capacitive micromachined ultrasonic transducers (CMUT)... can send and receive acoustic waves
Implementation Method 4
the vibration film and the support layer with the optical reflection layer can suitably be caused to adhere to each other via an acoustic matching layer (a layer for conformity of acoustic impedance between the vibration film and the support layer)
Data Source
Figure 1~3
Figure 4A~5
Figure 6~7
AI summary
A probe is provided in which penetration of an acoustic medium (100) into a support layer (103) of an optical reflection member through a pinhole or a scratch on an optical reflection layer (104) is suppressed, occurrence of a solvent crack is suppressed, and noise due to photoacoustic waves that occurs on a receiving surface can be suppressed. The probe includes an element having at least one cell (7) in which a vibration film (4) containing one electrode (2) out of two electrodes that are provided so as to interpose a space therebetween is vibratably supported. The probe further includes a support layer (103) disposed on the vibration film, and an optical reflection layer (104) disposed on the support layer. A protection layer (105) against an acoustic medium is formed on the optical reflection layer (104).