Acoustic Detection of Non-Metallic Objects Using Air-Coupled Transducers
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Solution Overview
Problem
Concealed object detection in obscuring mediums, such as clothing or shoes, is challenging for law enforcement and loss prevention due to the ineffectiveness of existing screening methods like metal detectors for non-metallic objects and the safety concerns of ionizing radiation-based technologies.
Innovation Solution
A portable acoustic/ultrasonic detection system utilizing air-coupled or electromagnetic-acoustic transducers to transmit and receive signals within the frequency range of 15 KHz to 500 MHz, capable of creating narrow beams and generating 2D or 3D images of concealed objects without physical contact, using signal processing techniques like beamforming and interferometry.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If metal detectors are used for concealed object detection, then detection capability is provided, but detection effectiveness is poor for non-metallic objects such as plastic or liquid materials
Solution Approach 1:
The patent replaces electromagnetic induction-based metal detectors with acoustic wave-based detection systems. The acoustic transducers transmit ultrasonic waves through the subject and detect reflections or transmission changes, enabling detection of non-metallic objects (plastic, liquid, organic materials) that are invisible to traditional metal detectors. This substitution fundamentally expands material type coverage while maintaining detection reliability.
Solution Approach 2:
The system changes the detection parameter from electromagnetic response (metal-specific) to acoustic impedance and sound speed variations (material-property-general). By measuring how acoustic waves interact with different materials based on their density and elastic properties, the system achieves universal detection across metallic, non-metallic, and liquid materials.
2Measurement precision
If ionizing radiation-based screening technologies are used, then detection capability is improved, but safety concerns arise due to harmful radiation exposure
Solution Approach 1:
The patent substitutes ionizing radiation (X-rays, gamma rays) with non-ionizing acoustic ultrasonic waves. The acoustic transducers generate sound waves at frequencies above human hearing (typically 20 kHz to several MHz) that penetrate materials and provide imaging without the carcinogenic risks associated with ionizing radiation, thereby eliminating harmful radiation exposure while maintaining measurement precision through advanced signal processing.
Solution Approach 2:
The system converts the potential harm of high-energy radiation into a beneficial low-energy acoustic wave approach. By using ultrasonic frequencies that are harmless to biological tissue yet sufficiently energetic to provide detailed material characterization through acoustic impedance measurements, the system achieves safe screening with high detection precision.
3Object-affected harmful factors
If traditional acoustic detection methods are used, then safety is maintained, but detection resolution and imaging capability are insufficient
Solution Approach 1:
The patent divides the acoustic detection system into multiple independent transducer elements arranged in arrays. Each element independently transmits or receives acoustic signals, and through beamforming algorithms, the system synthesizes high-resolution images by coherently processing signals from multiple segments. This segmentation enables both safety (using low-power acoustic waves) and high imaging resolution (through computational synthesis).
Solution Approach 2:
The system transitions from one-dimensional acoustic sensing to two-dimensional or three-dimensional imaging by arranging transducers in planar arrays and applying spatial signal processing. This dimensional expansion allows construction of cross-sectional images of concealed objects within the subject, providing detailed spatial resolution while maintaining acoustic safety.
4Reliability
If contact-based ultrasonic detection is used, then detection sensitivity is improved, but ease of operation is reduced due to requirement for mechanical coupling
Solution Approach 1:
The patent introduces air-coupled transducers that use air as an intermediary medium between the transducer and the subject, eliminating the need for direct mechanical contact or coupling gels. The air-coupled design maintains detection sensitivity by using high-power ultrasonic transmission through air while greatly simplifying operation, as operators only need to position the transducer near the subject without requiring skin contact or coupling agent application.
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 effective detection of concealed objects made of plastic or liquid materials, providing safer and cost-effective screening with high resolution imaging, allowing for real-time identification of hidden items without the need for mechanical coupling or ionizing radiation.
Implementation Method 1
at least one acoustic/ultrasonic transducer configured to convert the electrical signal into an acoustic/ultrasonic signal, transmit the acoustic/ultrasonic signal
Implementation Method 2
receive a reflected acoustic/ultrasonic signal from an object in the target area and convert the reflected acoustic/ultrasonic signal into a received electrical signal
Implementation Method 3
an acoustic/ultrasonic antenna aperture operatively connected to the transducer and configured to focus the transmitted acoustic/ultrasonic signal to create a narrow beam in the target area
Implementation Method 4
a processor configured to extract object information from the received electrical signal
Data Source
AI summary
An acoustic/ultrasonic detection system can detect, for example, an object concealed under the clothing of a subject. The system includes a signal generator configured to output an electrical signal. An acoustic/ultrasonic transducer can be configured to convert the electrical signal into an acoustic/ultrasonic signal, transmit the acoustic/ultrasonic signal, receive a reflected acoustic/ultrasonic signal from an object in the target area and convert the reflected acoustic/ultrasonic signal into a received electrical signal. The transducer is at least one of an air-coupled transducer and an electro-magnetic acoustic transducer. The system can also include an acoustic/ultrasonic antenna aperture operatively connected to the transducer and configured to focus the transmitted acoustic/ultrasonic signal to create a narrow beam in the target area, a processor configured to extract object information from the received electrical signal and an object indication device to provide an indication of a detected object based on the extracted object information.