CN103471998B - Thermoplastic material reflection and transmission coefficients laser measurement system - Google Patents
Thermoplastic material reflection and transmission coefficients laser measurement system Download PDFInfo
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- CN103471998B CN103471998B CN201310373174.8A CN201310373174A CN103471998B CN 103471998 B CN103471998 B CN 103471998B CN 201310373174 A CN201310373174 A CN 201310373174A CN 103471998 B CN103471998 B CN 103471998B
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Abstract
The present invention discloses a kind of thermoplastic material reflection and transmission coefficients laser measurement system.There is certain error in current nautical receiving set mensuration.Test bracket is placed in pond by the present invention, test bracket is placed with test sample, places acoustic absorbant in the below of test bracket, and the focused transducer be arranged on mechanical positioning mechanism is just arranged test sample.The signal of function generator inputs to power amplifier, through amplifying rear drive focused transducer to pulses of radiation sound wave in aqueous medium.Laser vibration measurer is placed on outside pond, the laser beam that laser vibration measurer sends is by being placed in lens entrance on basin side wall in aqueous medium, and being reflected back laser vibration measurer through catoptron, the output signal of laser vibration measurer is input to digital oscilloscope after prime amplifier.The feature of the non-cpntact measurement that the present invention utilizes vibration measurement with laser method to have carries out the measurement of transducer acoustic field characterisitic parameter, overcomes the interference effect to sound field when using nautical receiving set to measure.
Description
Technical field
The invention belongs to acoustic measuring technique field, relate to a kind of thermoplastic material reflection and transmission coefficients laser measurement system.
Background technology
In industry and medical ultrasound equipment development process and scientific research activity, need the different acoustics passive material of use to realize the transmission of sound wave, reflection or absorption function.Except the physical parameters such as density, the velocity of sound, hardness, the reflection and transmission coefficients of the parameter having a considerable influence to acoustic equipment performance mainly material, therefore must measure it accurately.
All the time, the measurement of the acoustical parameter such as material reflects and transmission coefficient is all undertaken by use acoustic sensor (nautical receiving set).During measurement, nautical receiving set is needed to be placed in sound field to be measured, first the sound radiation pressure value that transmitting transducer produces is measured, then test sample is placed in known sound field, utilize nautical receiving set to measure reflecting acoustic pressure amplitude and the transmission acoustic pressure amplitude of sample, just can calculate reflection coefficient and the transmission coefficient parameter of material.
Because nautical receiving set has certain bulk, be placed in sound field and can produce diffraction to incident acoustic wave, particularly when nautical receiving set and test sample between close together time, the multiple reflections of sound wave between the two can be caused, had a strong impact on the Measurement accuracy to reflected signal and transmission signal.And along with the rising of survey frequency, the diffraction impact that nautical receiving set produces can constantly increase, therefore, the measurement using nautical receiving set to carry out thermoplastic material acoustic characteristic has inevitable defect.
Summary of the invention
The present invention is devoted to overcome use nautical receiving set and carries out the intrinsic shortcoming of material acoustics feature measurement, the untouchable feature had by application vibration measurement with laser technology, eliminates the interference effect to sound field when using nautical receiving set to measure; Meanwhile, to the space integral effect of plane sound wave when the High Strength Plane sound wave utilizing focused transducer to produce in the present invention and laser measurement, improve the signal to noise ratio (S/N ratio) measured, enhance the measurement capability to all kinds of acoustical material.
The technical scheme that technical solution problem of the present invention is taked is:
The present invention includes function generator, power amplifier, mechanical positioning mechanism, digital oscilloscope, prime amplifier, laser vibration measurer, focused transducer, catoptron, acoustic absorbant, pond and test bracket.
Test bracket is placed in pond, test bracket is placed with test sample, places acoustic absorbant in the below of test bracket, and the focused transducer be arranged on mechanical positioning mechanism is just arranged test sample.
The signal of function generator inputs to power amplifier, through amplifying rear drive focused transducer to pulses of radiation sound wave in aqueous medium.
Laser vibration measurer is placed on outside pond, the laser beam of what laser vibration measurer sent be parallel to test sample upper surface is by being placed in lens entrance on basin side wall in aqueous medium, and be reflected back laser vibration measurer through catoptron, the output signal of laser vibration measurer is input to digital oscilloscope after prime amplifier, to obtain the required signal amplitude value measured.
Described laser vibration measurer measures transmission sound pressure amplitudes that the focused transducer reflecting acoustic pressure amplitude that sound pressure amplitudes produces after focal regions diametric integration value, focus beam after tested sample on focal plane produces after focal regions diametric integration value, focus beam after tested sample respectively along the diametric integration value of focal regions, utilizes above-mentioned three integration values to complete the calculating of test sample reflection and transmission coefficients.
Beneficial effect of the present invention:
The feature of the non-cpntact measurement utilizing vibration measurement with laser method to have carries out the measurement of transducer acoustic field characterisitic parameter, overcomes the interference effect to sound field when using nautical receiving set to measure.
The high-strength focused collimated beam of sound using focused transducer to produce detects, and adds the signal to noise ratio (S/N ratio) of measurement, improves the measurement capability to acoustical material.
Utilize the acoustic pressure integration value measured by laser vibration measurer to carry out reflection coefficient and transmission coefficient calculating, overcome the measuring error that sample making is uneven produced.
Accompanying drawing explanation
Fig. 1 is thermoplastic material reflection and transmission coefficients laser method measuring principle block diagram.
Fig. 2 is that supporting structure schematic diagram measured by sample.
Fig. 3 is laser method focused transducer sound field sound pressure measurement schematic diagram.
Embodiment
Below in conjunction with accompanying drawing, the invention will be further described.
The present invention proposes and utilize vibration measurement with laser technology to carry out the technical scheme of non-intrusion measurement to material acoustics characteristic, measure the sound radiation pressure of focused transducer on focal plane by using laser vibration measurer and measure the reflection and transmission acoustic pressure that sample produces under identical sound field conditions, reflection coefficient and the transmission loss of material can be calculated exactly, overcome shortcoming intrinsic when using nautical receiving set to carry out material acoustics parameter measurement.
As depicted in figs. 1 and 2, the measuring system that the present invention is formed primarily of following apparatus equipment realizes: focused transducer 7, function generator 1, power amplifier 2, mechanical positioning mechanism 3, laser vibration measurer 6, prime amplifier 5, digital oscilloscope 4, pond 11, catoptron 8, test bracket 12 and acoustic absorbant 10 etc.
Described focused transducer adopts ball-type ceramic component to be prepared from, and sound wave, after the inside surface radiation of ball-type element, collects formation focused sound waves in its focal regions, and wave front will present plane form, acoustic pressure amplitude by Gaussian function formal distribution.
Described function generator is universal electric instrumentation, and the filler pulse ripple signal required for exportable measurement, the parameter such as frequency, wave number, recurrence interval, signal amplitude of signal can regulate according to the requirement of measuring.
Described power amplifier is universal electric instrumentation, can amplify the input signal of signal source, formation can drive the output voltage signal of acoustic transducer, and the output impedance of power amplifier should match with the input impedance of transducer and have certain bandwidth of operation.
Described mechanical navigation system is used for fixed-focus transducer, and can regulate the angle of transducer, thus changes radiated sound direction of wave travel; Can regulate the underwater penetration of transducer simultaneously, can match with the surface of test sample to make the focal plane of transducer.
Described prime amplifier is general electronic instrument equipment, amplifies the output signal of laser vibration measurer, can work, and have lower background noise in wider operating frequency range.
Described digital oscilloscope is general electronic instrument equipment, can carry out quantification treatment to the output signal of prime amplifier, demonstrate measuring-signal waveform and can calculate the amplitude size of input signal, the parameters such as oscillographic sample frequency, vertical resolution, average time can regulate according to the needs measured.
Described laser vibration measurer is universal electric instrumentation, and this equipment will give off measurement laser beam, will produce reflects laser after acting on body surface, and the vibration velocity of body surface measured by vialog by receiving reflected laser signals.
Described test bracket is prepared from by nonmetallic materials, be made up of (structural representation is shown in Fig. 2) two annulus and four support bars.Test sample is placed on support, when measuring the transmission coefficient of sample, should ensure that laser beam is passed from the lower surface of material by the support bar of test bracket.
Described catoptron adopts optical coating flat glass eyeglass, and this catoptron will be fixed on basin side wall, for laser beam reflection is returned laser vibration measurer.
Described acoustic absorbant is formed by the Polymer materialspreparation with Wedge structure, for absorbing the sound wave of focused transducer, reduces reflective sound wave to the impact of test result.
Described test sample 9 needs to be prepared to planar wafer shape, and to ensure that reflected sound wave energy returns by former incident acoustic wave direction, the direction of propagation of transmitted acoustic pulse is not departed from.The thickness of sample should be long much smaller than Jiao of focused transducer, to ensure that the intensity distributions of focused sound waves on the upper and lower surface of sample does not have obvious change; The diameter of test sample much larger than the focal regions of focused transducer, should produce diffraction effect to avoid radiative acoustic wave in sample edge.
Test macro is as shown in Figure 1 formed by the said equipment, the reflected signal measure the radiation signal of focused transducer under identical drive signals on focal plane by utilizing laser vibration measurer, producing through sample and transmission signal, can calculate reflection coefficient and the transmission coefficient of test specimen material.
The course of work of the present invention: form measuring system by shown in Fig. 1, gets out instrumentation, injects degassed water in pond, is arranged on by focused transducer on mechanical positioning mechanism and is placed on test bracket by test sample.Acoustic absorbant is placed, for absorbing the sound wave of focused transducer in the below of test bracket.
Function generator is set and launches filler pulse signal, the frequency of filler pulse be sample treat measured frequency, much larger than the length of the reverberation time in pond, filler pulse, the cycle of filler pulse need should ensure that the sound wave gone out through transducer radiates can reach steady-state signal.The signal of function generator will be input to power amplifier, through amplifying rear drive focused transducer to pulses of radiation sound wave in aqueous medium.The angle of focused transducer will be regulated by mechanical positioning mechanism, with the surface making radiated sound wave energy impinge perpendicularly on test sample; Meanwhile, by the underwater penetration of the adjustable focused transducer of detent mechanism, the upper surface of test sample and the focal plane of focused transducer are coincided.Laser vibration measurer is placed on outside pond, and laser beam by being placed in lens entrance on basin side wall in aqueous medium, and is reflected back laser vibration measurer through catoptron.Laser beam should parallel with the upper surface of test sample, and to be separated by suitable distance with the surface of sample, can distinguish reflected signal and incident acoustic wave signal by laser vibration measurer.The output signal of laser vibration measurer is imported into digital oscilloscope after prime amplifier, to obtain the required signal amplitude value measured.In measuring process, first obtain the radiative acoustic wave intensity on focused transducer focal plane by laser vibration measurer, then measure the reflected signal produced when sample is placed on transducer focal plane; By the position of mobile laser vibration measurer, laser beam is passed from the direction paralleled with test sample lower surface, measures transmitted acoustic pulse signal.
By using the data such as the radiation signal amplitude on measured transducer focal plane, the test reflection that produces of sample and transmission signal amplitude, reflection coefficient and the transmission coefficient of detected materials just can be calculated.
Thermoplastic material reflection and transmission coefficients laser method surveying work principle:
Use laser method to measure the principle of work of thermoplastic material acoustic characteristic as shown in Figure 3, wherein, focused transducer is fixed on mechanical positioning mechanism, and acoustic axis is adjusted on z axle vertically.Laser vibration measurer is placed on to be measured outside sound field, and the laser beam given off is vertical with acoustic axis direction.Place catoptron outward in transducer radiates sound field, laser beam after inciding mirror surface along original route return laser light vialog.
When laser beam incides in sound field, due to piezooptical effect, sound wave will produce modulating action to laser.When laser vibration measurer passes the sound field of focused transducer along y direction of principal axis, according to acoustooptical interaction principle, output signal
v(
x) can be expressed as:
(1)
In formula,
=0.32 is the equivalent refraction coefficient of aqueous medium, and w is angular frequency,
p(
x,y) in sound field (
x,y) acoustic pressure of position.
When laser beam is through the focal plane of focused transducer, as establish the focal regions of transducer be in (
y 1 , y 2 ) interval in, in focal regions, the mean value of sound pressure amplitudes is A
0, then the output of laser vibration measurer can approximate representation be:
(2)
Therefore, the output of laser vibration measurer is directly proportional to the average sound pressure amplitude in focal regions, focal regions diameter.
Test sample is placed in the focal regions of focused transducer, and the focal plane of its upper surface and transducer is coincided, by adjusting the position of laser vibration measurer, laser beam being skipped over along the direction paralleled with test sample upper surface, the reflective sound wave that material upper surface produces can be detected.If the average sound pressure amplitude of this reflective sound wave in focal regions is A
1, then the output of laser vibration measurer can be expressed as:
（3）
The position of adjustment laser vibration measurer, makes laser beam skip over along the direction paralleled with test sample lower surface, can detect the transmitted acoustic pulse of sample lower surface.If the average sound pressure amplitude of transmitted acoustic pulse in focal regions is A
2, then the output of laser vibration measurer can be expressed as:
（4）
According to the definition of reflection coefficient and transmission coefficient, the reflection coefficient of test sample can be drawn
rand transmission coefficient
tcomputing formula can be expressed as:
；
（5）
Therefore, by using laser vibration measurer, the sound radiation pressure intensity of measurement transducer on focal plane, the test reflection that produces of sample and transmission signal, just can calculate reflection coefficient and the transmission coefficient of detected materials respectively.
Above-mentioned embodiment is used for explaining and the present invention is described, instead of pin limits the invention, and in the protection domain of spirit of the present invention and claim, any amendment make the present invention and change, all fall into protection scope of the present invention.
Claims (8)
1. thermoplastic material reflection and transmission coefficients laser measurement system, is characterized in that: comprise function generator, power amplifier, mechanical positioning mechanism, digital oscilloscope, prime amplifier, laser vibration measurer, focused transducer, catoptron, acoustic absorbant, pond and test bracket;
Test bracket is placed in pond, test bracket is placed with test sample, places acoustic absorbant in the below of test bracket, and the focused transducer be arranged on mechanical positioning mechanism is just arranged test sample;
The signal of function generator inputs to power amplifier, through amplifying rear drive focused transducer to pulses of radiation sound wave in aqueous medium;
Laser vibration measurer is placed on outside pond, the laser beam of what laser vibration measurer sent be parallel to test sample upper surface is by being placed in lens entrance on basin side wall in aqueous medium, and be reflected back laser vibration measurer through catoptron, the output signal of laser vibration measurer is input to digital oscilloscope after prime amplifier, to obtain the required signal amplitude value measured;
Described laser vibration measurer measures transmission sound pressure amplitudes that the focused transducer reflecting acoustic pressure amplitude that sound pressure amplitudes produces after focal regions diametric integration value, focus beam after tested sample on focal plane produces after focal regions diametric integration value, focus beam after tested sample respectively along the diametric integration value of focal regions, utilizes above-mentioned three integration values to complete the calculating of test sample reflection and transmission coefficients;
Described function generator launches filler pulse signal, the frequency of filler pulse be test sample treat measured frequency, the length of cycle of filler pulse much larger than reverberation time in pond, filler pulse should ensure that the sound wave that line focus transducer radiates goes out can reach steady-state signal.
2. thermoplastic material reflection and transmission coefficients laser measurement system according to claim 1, is characterized in that: the output impedance of described power amplifier and the input impedance of focused transducer match and has certain bandwidth of operation.
3. thermoplastic material reflection and transmission coefficients laser measurement system according to claim 1, it is characterized in that: described mechanical positioning mechanism is used for fixed-focus transducer, and the angle of focused transducer is regulated, thus change radiated sound direction of wave travel; The underwater penetration of focused transducer is regulated simultaneously, can coincide with the upper surface of test sample to make the focal plane of focused transducer.
4. thermoplastic material reflection and transmission coefficients laser measurement system according to claim 1, it is characterized in that: described focused transducer adopts ball-type ceramic component to be prepared from, sound wave is after the inside surface radiation of ball-type ceramic component, in its focal regions, collect formation focused sound waves, wave front presents plane form, acoustic pressure amplitude by Gaussian function formal distribution.
5. thermoplastic material reflection and transmission coefficients laser measurement system according to claim 1, is characterized in that: described catoptron adopts optical coating flat glass eyeglass.
6. thermoplastic material reflection and transmission coefficients laser measurement system according to claim 1, it is characterized in that: described acoustic absorbant is formed by the Polymer materialspreparation with Wedge structure, for absorbing the sound wave of focused transducer, reduce reflective sound wave to the impact of test result.
7. thermoplastic material reflection and transmission coefficients laser measurement system according to claim 1, it is characterized in that: described test bracket is prepared from by nonmetallic materials, be made up of two annulus and four support bars, test sample is placed on test bracket, when measuring the transmission coefficient of sample, guarantee laser beam is passed from the lower surface of material by the support bar of test bracket.
8. thermoplastic material reflection and transmission coefficients laser measurement system according to claim 1, it is characterized in that: described test sample is planar wafer shape, to ensure that reflected sound wave energy returns by former incident acoustic wave direction, the direction of propagation of transmitted acoustic pulse is not departed from; The thickness of test sample should be long much smaller than Jiao of focused transducer, to ensure that the intensity distributions of focused sound waves on the upper and lower surface of sample does not have obvious change; The diameter of test sample much larger than the focal regions of focused transducer, should produce diffraction effect to avoid radiative acoustic wave in sample edge.
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| CN201310373174.8A CN103471998B (en) | 2013-08-23 | 2013-08-23 | Thermoplastic material reflection and transmission coefficients laser measurement system |
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| CN201310373174.8A CN103471998B (en) | 2013-08-23 | 2013-08-23 | Thermoplastic material reflection and transmission coefficients laser measurement system |
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| CN105050020B (en) * | 2015-07-31 | 2018-02-27 | 浙江省计量科学研究院 | Free found field device based on optics non-destructive monitoring technology |
| CN108007552A (en) * | 2017-10-11 | 2018-05-08 | 中国船舶重工集团公司第七〇五研究所 | Underwater sound transmitting transducer acoustical behavior measuring method under a kind of high hydrostatic pressure |
| CN110608795B (en) * | 2018-06-14 | 2024-06-11 | 重庆海扶医疗科技股份有限公司 | Dynamic sound pressure detection device and dynamic sound pressure detection method |
| EP3897391B1 (en) * | 2018-12-18 | 2023-11-15 | Insightec Ltd. | Echo-based focusing correction |
| CN111505609B (en) * | 2020-03-26 | 2023-09-12 | 中国船舶重工集团公司第七一五研究所 | Method for measuring absolute sound pressure of ultrasonic transducer |
| CN114295724A (en) * | 2021-12-29 | 2022-04-08 | 电子科技大学(深圳)高等研究院 | Sound wave test tube |
| CN114659608A (en) * | 2022-02-20 | 2022-06-24 | 中国船舶重工集团公司第七一五研究所 | Focal length measuring system and method for planar focusing transducer |
| CN115276829B (en) * | 2022-08-05 | 2023-04-14 | 天津大学 | Laser-induced acoustic transducer system based on acoustic super surface |
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| US7251196B1 (en) * | 2005-05-31 | 2007-07-31 | The United States Of America As Represented By The Secretary Of The Navy | Passive optical detection of underwater sound |
| JP2010002415A (en) * | 2008-05-20 | 2010-01-07 | National Institute Of Advanced Industrial & Technology | Method for measuring sound pressure intensity distribution of ultrasonic wave, method and device of measuring energy density distribution of ultrasonic wave |
| CN102141427B (en) * | 2010-12-02 | 2013-09-11 | 中国船舶重工集团公司第七一五研究所 | Method for detecting sound field parameter in fluid medium by using laser vibrometer |
| CN203414165U (en) * | 2013-08-23 | 2014-01-29 | 中国计量学院 | Laser measurement system for reflection and transmission coefficients of ultrasonic materials |
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