CN106971708B

CN106971708B - Multi-lens for amplifying direction angle of ultrasonic detector

Info

Publication number: CN106971708B
Application number: CN201710106999.1A
Authority: CN
Inventors: 奚磊; 金天
Original assignee: University of Electronic Science and Technology of China
Current assignee: University of Electronic Science and Technology of China
Priority date: 2017-02-27
Filing date: 2017-02-27
Publication date: 2021-06-01
Anticipated expiration: 2037-02-27
Also published as: CN106971708A

Abstract

The invention discloses a multi-lens for amplifying a direction angle of an ultrasonic detector, and belongs to the field of acoustic signal imaging. The multi-lens is made by tightly attaching N layers of lenses made of different materials, and the two surfaces of the multi-lens are smooth; between two adjacent lenses, the sound velocity as a concave material is less than the sound velocity as a convex material; and at least one of the materials has a sound velocity greater than the ambient sound velocity (e.g., water or air). The invention utilizes the principle that an acoustic signal can be refracted when being transmitted from one medium to another medium to enlarge the direction angle of the multi-lens; after two or more times of divergence, the effect of amplifying the direction angle of the ultrasonic detector is finally achieved.

Description

Multi-lens for amplifying direction angle of ultrasonic detector

Technical Field

The invention belongs to the field of acoustic signal imaging, and particularly relates to a multi-lens for enlarging the direction angle of an acoustic signal by using the principle that the acoustic signal can be refracted when the acoustic signal is transmitted from one medium to another medium.

Background

At present, the imaging modes of the ultrasonic detector used at home and abroad mainly comprise ultrasonic imaging, photoacoustic imaging, thermoacoustic imaging and the like, and the imaging modes have certain requirements on the direction angle of the ultrasonic detector.

For example, photoacoustic tomography in photoacoustic imaging, the most common scanning method is to uniformly irradiate a target with pulsed laser to excite photoacoustic signals, scan the target 360 ° with a non-focused ultrasound probe to collect the photoacoustic signals, and finally obtain an image of the target object through a reconstruction algorithm. This scanning mode has high requirements on the direction angle of the ultrasound probe, and if the size of the target object is larger than or close to the direction angle, large deformation occurs at the edge of the image. In view of the above problems, many research groups at home and abroad have proposed many solutions, such as methods of using a high-performance ultrasound probe, using multiple ultrasound probes for scanning, and using a better algorithm to reconstruct images, which indeed improve the resolution of some images at the edge, but the improvement is not excessive. A further solution is to increase the azimuth angle by adding an acoustic lens in front of the ultrasound probe, which does also optimize the system to some extent, but only uses one lens for magnification, so that the azimuth angle can be magnified only two to three times, which is not enough to avoid distortion at the image edges.

Disclosure of Invention

In order to solve the problem of deformation of the edge of an image in photoacoustic tomography, the invention provides a multi-lens which can be used for amplifying the direction angle of an ultrasonic detector.

A multi-lens for magnifying the azimuth angle of an ultrasound probe, characterized in that: the multi-lens is made by tightly attaching N layers of lenses made of different materials, and the two surfaces of the multi-lens are smooth; n is more than or equal to 2, and the sound velocity of the concave material is less than that of the convex material between two adjacent lenses; and at least one of the materials has a sound velocity greater than the ambient sound velocity (e.g., water or air).

Further, since the acoustic impedance may be significantly different between different materials, which may result in significant attenuation of the acoustic signal, a thin film of a transition material is disposed between two adjacent lenses, the transition material having an acoustic impedance between the two adjacent materials.

The principle of the invention is as follows: when an acoustic signal propagates from one medium of sound velocity to another, refraction occurs. When an acoustic signal is transmitted to a lens made of a material with the minimum sound velocity from an external medium, the acoustic signal is refracted to be diffused; when the acoustic signal re-propagates into a different medium, its angle becomes larger again because of refraction. After two or more times of divergence, the effect of amplifying the direction angle of the ultrasonic detector is finally achieved. Because the acoustic impedances of different materials are different, even the difference is possibly large, the acoustic signals are lost due to reflection, and a film made of a material with the acoustic impedance between the materials is placed between the different materials, so that the effects of acoustic impedance matching and loss reduction are achieved.

Compared with the prior art, the invention has the following advantages:

(1) the method has obvious improvement on the direction angle of the ultrasonic detector, and the direction angle can be enlarged to six to seven times when no lens is used, so that the method is improved to a great extent compared with the prior method.

(2) The invention has a complete cylinder appearance without concave or convex, realizes the diffusion of ultrasonic signals by a plane, greatly improves the defect that the prior acoustic lens can not be in direct contact with a human body or needs to be coated with a large amount of ultrasonic coupling agent around the prior acoustic lens, and is very convenient to use.

(3) The device of the invention has the advantages of low price, simple manufacture and use, wide application range and easy application and popularization.

Drawings

Fig. 1 is a schematic view of an acoustic lens of embodiment 1. The parts shown in the figure are: a plano-concave lens 1-1, a plano-convex lens 1-2, and a film 1-3.

Fig. 2 is a schematic view of the acoustic lens of embodiment 2. The parts shown in the figure are: a plano-concave lens 2-1, a biconvex lens 2-2, and a film 2-3.

Fig. 3 is a schematic view of the acoustic lens of embodiment 3. The parts shown in the figure are: a plano-concave lens 3-1, a concave-convex lens 3-2, a concave-convex lens 3-3, and a plano-convex lens 3-4.

Fig. 4 is an image of a pencil lead inserted in agar using the acoustic lens of example 1.

Fig. 5 is an image of a pencil lead inserted in agar without the acoustic lens of example 1.

Detailed Description

Example 1 simple acoustic lens construction of the invention

FIG. 1 is a simple acoustic lens of the present invention, which is a plano-concave lens 1-1 made of polydimethylsiloxane (sound velocity of 950m/s), and the curvature of the concave surface of the lens is 28.6m^-1Epoxy resin 301 (sound velocity 2600m/s) was made into plano-convex lens 1-2. Since the acoustic impedance difference between the PDMS and the epoxy 301 is large and the acoustic signal is largely lost due to reflection when passing through the boundary, the thin film 1-3 with a thickness of 0.1mm is made of paraffin and attached between the two lenses. The finally finished ultrasonic lens is a cylinder and can play a role in diffusing ultrasonic signals.

EXAMPLE 2 two-sided Acoustic diffuser lens Structure of the present invention

Fig. 2 shows a two-side diverging acoustic lens structure of the present invention, which is similar to embodiment 1 and can be regarded as an acoustic lens combination of two embodiments 1. The plano-concave lens 2-1 is made of polydimethylsiloxane with low sound velocity, the biconvex lens 2-2 is made of epoxy resin 301 with high sound velocity, and transition layer films 2-3 made of paraffin are added to adjacent interfaces of the two lenses. This structure can make the directivity angle of the ultrasonic probe larger than that of the acoustic lens in embodiment 1. Furthermore, the acoustic lenses in the first embodiment can be combined in different orders, so as to achieve the functions of extending the acoustic focal length.

EXAMPLE 3 multilayer Acoustic lens of the present invention

FIG. 3 is a schematic diagram of a multilayer acoustic lens of the present invention, which is a plano-concave lens 3-1 made of polydimethylsiloxane (sound velocity of 950m/s), and has a concave surface with a curvature of 28.6m^-1(ii) a The meniscus lens 3-2 was made with paraffin wax (sound velocity of 2210m/s) and had a convex curvature of 28.6m^-1Concave curvature of 25m^-1(ii) a The meniscus lens 3-3 was made of epoxy 301 (acoustic velocity 2600m/s) with a convex curvature of 25m^-1Concave curvature of 22.2m^-1(ii) a Finally, the plano-convex lens 3-4 is made of organic glass (the sound velocity is 2692m/s), and the curvature of the convex surface of the plano-convex lens is 22.2m^-1. In this embodiment, since a multi-layer structure is adopted, the sound velocity is sequentially increased, and a transition layer may not be added.

Photoacoustic imaging experiment and contrast using the invention

The experimental steps are as follows:

(1) cylindrical agar is made, and pencil leads with the diameter of 0.5mm are inserted at the surface of the agar in a cross shape.

(2) Laser is uniformly irradiated on the surface of the agar, and an ultrasonic detector is used for rotating by one circle by taking the agar as a center to acquire photoacoustic signals.

(3) And carrying out data processing on the acquired photoacoustic signals by using Matlab software through a computer to obtain an image of the target object in the scanning area.

(4) The acoustic lens of example 1 was added to the ultrasound probe and the above procedure was repeated.

The results obtained without using the ultrasonic lens in example 1 are shown in fig. 5, and the results obtained with the ultrasonic lens are shown in fig. 4, and it is apparent that the pencil lead image at the edge is deformed significantly when the ultrasonic lens is not used. The pencil lead image at the edge is completely free of distortion after the use of the ultrasonic lens.

Claims

1. A multi-lens for magnifying the azimuth angle of an ultrasound probe, characterized in that: the multi-lens is cylindrical and is divided into a double-convex sound lens or a multi-layer sound lens;

the double-convex acoustic lens comprises an epoxy resin double-convex lens in the middle layer and polydimethylsiloxane concave lenses symmetrically arranged on two sides of the double-convex lens, and a transition layer film made of paraffin is added to an adjacent interface;

the multilayer acoustic lens comprises a first plano-concave lens, a second concave-convex lens, a third concave-convex lens and a fourth plano-convex lens which are sequentially stacked; the first plano-concave lens material is polydimethylsiloxane, and the curvature of the concave surface of the first plano-concave lens material is 28.6m^-1(ii) a The second meniscus lens is made of paraffin wax and has a convex curvature of 28.6m^-1Concave curvature of 25m^-1(ii) a The third concave-convex lens is made of epoxy resin and has a convex curvature of 25m^-1Concave curvature of 22.2m^-1(ii) a The fourth plano-convex lens is made of organic glass, and the curvature of the convex surface of the fourth plano-convex lens is 22.2m^-1。