Ultrasonic Probe Reflective Layer Design for Focusing and Bandwidth Control
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Solution Overview
Problem
Ultrasonic imaging probes face challenges in achieving a narrow bandwidth in the short-distance domain with reduced focusing length, and in improving image quality, particularly due to limitations in the design of reflective layers and acoustic impedance matching.
Innovation Solution
A probe design incorporating a piezoelectric layer, a backing layer, a reflective layer with higher acoustic impedance, and a lens layer, where the reflective layer occupies a smaller area and length than the piezoelectric layer, and is strategically positioned between the piezoelectric and backing layers to amplify and focus ultrasonic waves, along with a matching layer to reduce impedance differences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If a reflective layer occupying a smaller area than the piezoelectric layer is used, then the focusing length of ultrasonic waves is reduced, but the bandwidth in the short-distance domain becomes wider
Solution Approach 1:
The reflective layer is designed with non-uniform thickness, where the thickness increases from the central portion toward the both end portions in the elevation direction. This local variation in thickness creates different acoustic impedance characteristics at different locations, enabling the reflective layer to simultaneously achieve reduced focusing length in the central region and controlled bandwidth in the short-distance domain through the gradient structure.
Solution Approach 2:
The reflective layer's thickness parameter is changed continuously from the central portion to the end portions, creating a gradient structure. This parameter change allows the acoustic impedance to vary spatially, which controls the ultrasonic wave reflection characteristics to achieve both reduced focusing length and appropriate bandwidth control in different spatial regions.
2Object-generated harmful factors
If the reflective layer occupies a smaller area than the piezoelectric layer, then the side lobes are reduced, but the acoustic pressure strength in the short-distance domain decreases
Solution Approach 1:
The reflective layer employs local quality variation through non-uniform thickness distribution, being thinner at the central portion and thicker at the end portions. This local differentiation allows the central region to maintain high acoustic pressure strength while the edge regions control side lobe generation, achieving both objectives simultaneously through spatially varying properties.
Solution Approach 2:
The probe structure combines the piezoelectric layer with a composite reflective layer having varying thickness, creating a composite structure that integrates the functions of both amplitude control (for acoustic pressure) and spatial distribution control (for side lobe reduction) in a single integrated component.
3Reliability
If there is a large difference in acoustic impedance between the piezoelectric layer and the subject, then ultrasonic wave transmission is poor, but using materials with extreme impedance values increases device complexity
Solution Approach 1:
The matching layer acts as an intermediary between the piezoelectric layer and the subject, providing a gradual transition in acoustic impedance. This intermediate layer reduces the impedance mismatch by creating a stepped or gradient impedance profile, improving ultrasonic wave transmission without requiring extreme material properties or complex multi-layer structures.
Solution Approach 2:
The matching layer changes the acoustic impedance parameter gradually from the high impedance of the piezoelectric layer to the lower impedance of the subject. This continuous or stepped parameter change enables efficient ultrasonic energy transmission by reducing reflection at interfaces, achieving reliable transmission with a simple single-layer or dual-layer structure.
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 design enables a narrower bandwidth with increased acoustic pressure strength in the short-distance domain, reduced side lobes, and improved image quality by effectively focusing ultrasonic waves and enhancing apodization.
Implementation Method 1
a piezoelectric layer to generate ultrasonic waves
Implementation Method 2
a backing layer to absorb ultrasonic waves generated at the piezoelectric layer and proceeding toward a rear
Implementation Method 3
a reflective layer... provided in between the piezoelectric layer and the backing layer to amplify the ultrasonic waves generated at the piezoelectric layer; The reflective layer is formed of material having an acoustic impedance higher than an acoustic impedance of the piezoelectric layer
Implementation Method 4
a lens layer to focus the ultrasonic waves proceeding toward a front of the piezoelectric layer at a certain point
Implementation Method 5
a matching layer to reduce a difference of acoustic impedances between the piezoelectric layer and a subject
Data Source
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AI summary
A probe (100) includes: a piezoelectric layer (111) to generate ultrasonic waves, a backing layer (112) to absorb ultrasonic waves generated at the piezoelectric layer and proceeding toward a rear, a reflective layer (113) occupying an area smaller than an area of the piezoelectric layer and provided in between the piezoelectric layer and the backing layer to amplify the ultrasonic waves generated at the piezoelectric layer, and a lens layer (115) to focus the ultrasonic waves proceeding toward a front of the piezoelectric layer at a certain point.