CN110596009B - High-sensitivity large-area laser ultrasonic imaging method - Google Patents
High-sensitivity large-area laser ultrasonic imaging method Download PDFInfo
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- CN110596009B CN110596009B CN201911015514.3A CN201911015514A CN110596009B CN 110596009 B CN110596009 B CN 110596009B CN 201911015514 A CN201911015514 A CN 201911015514A CN 110596009 B CN110596009 B CN 110596009B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/01—Arrangements or apparatus for facilitating the optical investigation
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
- G01N21/1702—Systems in which incident light is modified in accordance with the properties of the material investigated with opto-acoustic detection, e.g. for gases or analysing solids
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
- G01N29/04—Analysing solids
- G01N29/06—Visualisation of the interior, e.g. acoustic microscopy
- G01N29/0654—Imaging
- G01N29/0681—Imaging by acoustic microscopy, e.g. scanning acoustic microscopy
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
- G01N29/22—Details, e.g. general constructional or apparatus details
- G01N29/24—Probes
- G01N29/2418—Probes using optoacoustic interaction with the material, e.g. laser radiation, photoacoustics
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
- G01N21/1702—Systems in which incident light is modified in accordance with the properties of the material investigated with opto-acoustic detection, e.g. for gases or analysing solids
- G01N2021/1708—Systems in which incident light is modified in accordance with the properties of the material investigated with opto-acoustic detection, e.g. for gases or analysing solids with piezotransducers
Abstract
The invention discloses a high-sensitivity large-area laser ultrasonic imaging method which can realize the back mode rapid laser ultrasonic imaging with simple structure, high sensitivity and large field of view. The invention selects the micro-lens array made of the piezoelectric material with high optical transmittance as the laser micro-focusing unit and the ultrasonic signal receiving unit, skillfully realizes the coaxial, confocal and integrated structure of optical and acoustic paths, eliminates the optical or acoustic multi-reflection type excitation or receiving structure, effectively improves the efficiency of laser ultrasonic excitation and the receiving sensitivity and signal-to-noise ratio, is easier to realize the miniaturization and large-area imaging of the laser ultrasonic lens, and is expected to be applied to the fields of biological identification, medical subcutaneous blood vessel imaging, material nondestructive detection and the like.
Description
Technical Field
The invention relates to an imaging method, in particular to a high-sensitivity large-area laser ultrasonic imaging method which is suitable for the fields of biological blood vessel imaging, identity recognition, nondestructive inspection of material subsurface and the like.
Background
The laser ultrasonic imaging technology is a novel nondestructive testing technology, can realize high-resolution medical or industrial detection of hundreds of micrometers to dozens of nanometers, has higher resolution and requires lower laser energy to nano focus level in a microscopic imaging mode, so that an optical excitation path and an acoustic detection path of the laser ultrasonic imaging technology generally need a coaxial confocal structure to improve the laser ultrasonic excitation and detection efficiency.
The common scheme is that a light-transmitting and sound-reflecting (or sound-transmitting and light-reflecting) element is added in a light path, and a coaxial confocal structure for laser ultrasonic excitation and detection is realized through multiple optical or acoustic reflections; in another scheme, the ultrasonic detector with a hollow structure is specially processed, and the light path is incident from the hollow structure of the ultrasonic detector. However, the existing schemes above all have the disadvantages of increased optical or acoustic reflection loss, reduced receiving area of the acoustic detector, high processing difficulty and the like, so that the sensitivity of laser ultrasonic excitation and receiving is reduced, and the volume and complexity of the system are increased by the mechanical scanning structure. On the other hand, the above structure greatly limits the size of the imaging scanning area, greatly reduces the real-time performance of the system regardless of optical scanning or mechanical scanning, and generally acquires laser ultrasonic signals in the whole depth propagation time period, so that the total data volume is huge, and the rapid and large-area laser ultrasonic imaging is difficult to realize.
Disclosure of Invention
In order to solve the problems, the invention provides a high-sensitivity large-area laser ultrasonic imaging method, which applies a micro-lens array made of a piezoelectric material with high optical transmittance to a laser ultrasonic excitation and receiving structure for high-resolution laser ultrasonic imaging, and can realize a simple structure with coaxial, confocal and small integration of optical and acoustic paths.
In order to achieve the above object, the present invention comprises the following steps:
s1: the light source emits a pulse or modulated collimated light beam, after the light beam penetrates through the micro-lens array made of the piezoelectric material with high optical transmittance, the light beam is subjected to micro-focusing by each micro-lens array element of the micro-lens array and irradiates on a sample to be detected to generate a laser ultrasonic signal;
s2: the laser ultrasonic signals are received by each micro-lens array element of the micro-lens array in a back mode, and after passing through the signal preprocessing module, the extreme values of the laser ultrasonic signals received by each micro-lens array element are read in a row-column addressing mode and stored in a computer;
s3: the laser ultrasonic signal extremum received by each micro lens array element is directly projected and imaged, so that large-area, two-dimensional and rapid laser ultrasonic imaging of the optical absorption difference of the tested sample is realized.
At S1, the light source operates at one or more wavelengths selected from the ultraviolet to infrared range.
In S1, the microlens array has high transmittance to the wavelength of the light beam emitted by the light source, and the substrate is preferably a piezoelectric single crystal or a piezoelectric composite material with high optical transmittance.
In S1, the microlens array elements are plated with electrodes, and the electrode material is preferably a tin-doped indium oxide thin film material with high optical transmittance.
In S1, the microlens array elements are preferably in a plano-convex or circular configuration.
In S1, the microlens array is preferably in a flat plate structure.
In S1, the microlens array elements may be preferably coated with an optical antireflection film in a specific spectral region.
In S1, the microlens array elements preferably have the same shape, size and optical focal length.
In S1, the arrangement of the large area array composed of the microlens array elements is preferably square.
In S1, a large-area array composed of micro-lens array elements with micron-to-centimeter-sized dimensions is embossed on the base substrate.
In S1, the regions of the substrate except the microlens array elements are coated with optical masks with high optical reflectivity, so as to prevent light beams from passing through the gaps between the microlens array elements.
The invention has the beneficial effects that:
(1) in the laser ultrasonic excitation and receiving structure, a micro-lens array made of a piezoelectric material with high optical transmittance is used as a laser micro-focusing and ultrasonic receiving module, so that optical elements in a light path are effectively reduced, a simple structure with coaxial, confocal and small integration of an optical path and an acoustic path is realized, multiple reflection attenuation of the optical path and the acoustic path is reduced, and the laser ultrasonic excitation efficiency, the receiving sensitivity and the signal-to-noise ratio are effectively improved.
(2) The micro lens array is easy to realize the cutting of a large-area flat plate structure and various array modes, realizes the large-area array laser excitation and ultrasonic receiving of a plurality of micro optical focuses, has no long time consumption of a mechanical optical or acoustic scanning mechanism, and is very suitable for the working mode that a tested sample and an ultrasonic sensor are fixed in position and laser large-area excitation laser ultrasonic signals are carried out.
(3) Because the traditional laser ultrasonic system scheme is to collect laser ultrasonic signals in the whole depth propagation time period, and when the number of receiving array elements is large, the collected data volume is large and the collection time is long, the invention adopts a row-column addressing mode to only read and store the extreme value of the laser ultrasonic signals, compared with the traditional scheme, the total data volume is greatly reduced, and the invention has the advantages of fast data collection and transmission, simple image reconstruction algorithm and the like.
Drawings
Fig. 1 is a schematic structural diagram of a high-sensitivity large-area laser ultrasonic imaging system for implementing the present invention.
FIGS. 2a and 2b are impedance spectrum and ultrasonic receiving response graph of PMNT single crystal material, respectively, and FIGS. 2c and 2d are impedance spectrum and ultrasonic receiving response graph of PMNT 1-3 piezoelectric composite material, respectively;
FIG. 3 is a graph of optical transmittance of two tin-doped indium oxide films.
Reference numerals: 1. the device comprises a light source, 2, a collimating lens, 3, a micro-lens array, 4, a signal preprocessing module, 5, a computer, 6 and a sample to be detected.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Example 1: referring to fig. 1, the high-sensitivity large-area laser ultrasonic imaging system shown in fig. 1 includes a light source 1, a light source 2, a collimating lens 3, a micro-lens array 4, a signal preprocessing module 5, a computer 6, and a sample to be measured.
A collimating lens 2 and a micro-lens array 3 are sequentially arranged under the light source 1; the sample 6 to be measured is placed below the microlens array 3.
The micro-lens array 3, the signal preprocessing module 4 and the computer 5 are electrically connected in sequence; the light source 1 and the computer 5 are in turn electrically connected.
Further, the light source 1 is an OPO laser (GWU, model versaScan/120) with tunable wavelength, the light pulse width is 10ns, the working wavelength is 410 and 2500nm, and the maximum single pulse energy is 30 mJ; the array size of the micro lens array 3 is 10mm x 10mm, the diameter of the micro lens array element is 250um, the curvature radius is 835μm, the effective focal length is less than 1.8mm, the wafer material is a PMNT single crystal material with optical transmittance, the lower diagrams 2a-2d are impedance spectra and ultrasonic receiving response diagrams of the PMNT single crystal material and the PMNT 1-3 piezoelectric composite material respectively, and the electrode material is a tin-doped indium oxide thin film with high optical transmittance. For example, the typical optical transmittance of tin-doped indium oxide film to 450nm-1100nm can reach 75% -98%, referring to FIG. 3, which is a graph of the optical transmittance of two ITO films.
Further, the acoustic coupling medium between the microlens array 3 and the sample 6 to be measured is a gas (such as air containing a certain humidity), a liquid (such as water or a condensate) or a direct contact.
Example 2:
the structure of the present embodiment is similar to that of embodiment 1, except that: the light source 1 is a pulsed Laser diode (Laser Components, model 905D4S16C), the optical pulse width is 100ns, the operating wavelength is 905nm, and the peak power is 140W.
The invention also provides a method for imaging by using the device, which comprises the following steps:
s1: the light source 1 emits a pulse or modulated light beam, and after being collimated by the collimating lens 2, the light beam is irradiated on a tested sample 6 by the micro-focusing of the micro-lens array 3 to generate a laser ultrasonic signal;
s2: the laser ultrasonic signals are received by each micro-lens array element of the micro-lens array 3 in a back mode, and after passing through the signal preprocessing module 4, the extreme values of the laser ultrasonic signals are read in a row-column addressing mode and stored in the computer 6;
s3: the extreme value of the laser ultrasonic signal received by each micro-lens array element is directly projected and imaged (wherein the spatial position of projection is determined by the row sequence number and the space of each micro-lens array element), so that large-area, two-dimensional and rapid laser ultrasonic imaging of the optical absorption difference of the tested sample is realized.
It should be noted that although embodiments of the present invention have been shown and described herein, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.
Claims (10)
1. A high-sensitivity large-area laser ultrasonic imaging method is characterized by comprising the following steps:
s1: the light source emits a pulse or modulated collimated light beam, after the light beam penetrates through the micro-lens array made of the piezoelectric material with high optical transmittance, the light beam is subjected to micro-focusing by each micro-lens array element of the micro-lens array and irradiates on a sample to be detected to generate a laser ultrasonic signal;
s2: the laser ultrasonic signals are received by each micro-lens array element of the micro-lens array in a back mode, and after passing through the signal preprocessing module, the extreme values of the laser ultrasonic signals received by each micro-lens array element are read in a row-column addressing mode and stored in a computer;
s3: the laser ultrasonic signal extremum received by each micro lens array element is directly projected and imaged, so that large-area, two-dimensional and rapid laser ultrasonic imaging of the optical absorption difference of the tested sample is realized.
2. The high-sensitivity large-area laser ultrasonic imaging method according to claim 1, wherein: at S1, the light source operates at one or more wavelengths selected from the ultraviolet to infrared range.
3. The high-sensitivity large-area laser ultrasonic imaging method according to claim 1, wherein: in S1, the microlens array has high transmittance to the wavelength of the light beam emitted by the light source, and the base substrate is made of a piezoelectric single crystal or a piezoelectric composite material having high optical transmittance.
4. The high-sensitivity large-area laser ultrasonic imaging method according to claim 1, wherein: in S1, the microlens array elements are plated with electrodes, and the electrode material is selected from tin-doped indium oxide thin film material with high optical transmittance.
5. The high-sensitivity large-area laser ultrasonic imaging method according to claim 1, wherein: in S1, the microlens array element is selected to be of a plano-convex or circular structure.
6. The high-sensitivity large-area laser ultrasonic imaging method according to claim 1, wherein: in S1, the microlens array is selected from a flat plate structure and an optical antireflection film that can be plated with a specific spectral region.
7. The high-sensitivity large-area laser ultrasonic imaging method according to claim 1, wherein: in S1, the microlens array elements are selected to have the same shape, size and optical focal length.
8. The high-sensitivity large-area laser ultrasonic imaging method according to claim 1, wherein: in S1, the arrangement of the large area array composed of the microlens array elements is selected to be square.
9. The high-sensitivity large-area laser ultrasonic imaging method according to claim 3, wherein: in S1, a large-area array composed of micro-lens array elements with micron-scale to centimeter-scale dimensions is embossed on the substrate.
10. The high-sensitivity large-area laser ultrasonic imaging method according to claim 9, wherein: in S1, the regions of the substrate except the microlens array elements are coated with optical masks with high optical reflectivity, so as to prevent light beams from passing through the gaps between the microlens array elements.
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| CN112285506A (en) * | 2020-10-27 | 2021-01-29 | 国网重庆市电力公司电力科学研究院 | Laser ultrasonic focusing detection imaging system |
| CN116999726B (en) * | 2023-10-08 | 2023-12-12 | 深圳市丛峰科技有限公司 | Micro-focusing ultrasonic diagnosis and treatment equipment and method |
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| JPH1010459A (en) * | 1996-06-19 | 1998-01-16 | Sony Corp | Variable focus lens |
| JPH11147324A (en) * | 1997-11-17 | 1999-06-02 | Minolta Co Ltd | Optical recording apparatus |
| CN100571626C (en) * | 2008-07-03 | 2009-12-23 | 刘国栋 | Light sound ultrasonic excitation and sensing integrated checkout gear |
| KR20150046637A (en) * | 2013-10-22 | 2015-04-30 | 삼성전자주식회사 | Wideband ultrasonic probe for photoacoustic image and ultrasound image |
| CN106333650B (en) * | 2016-09-26 | 2019-05-07 | 华南师范大学 | A kind of multiple dimensioned opto-acoustic microscopic imaging devices and methods therefor |
| CN107216149A (en) * | 2017-06-22 | 2017-09-29 | 盐城工学院 | A kind of transparent lead-free piezoceramic material and preparation method thereof |
| CN108042110A (en) * | 2017-12-22 | 2018-05-18 | 深圳先进技术研究院 | Multi-modality imaging system |
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