CN1831528A - Measuring method for pulse response of ultrasonic transducer based on optoacoustic effect - Google Patents

Abstract

A method for measuring pulse response of ultrasonic transverter based on optoacoustic effect includes using a beam of pulse laser to illuminate a standard absorption body uniformly for exciting ultrasound, receiving said ultrasonic signal by ultrasonic transverter and converting ultrasonic signal to be electric signal, deriving out pulse response of ultrasonic transverter by carrying out inverse convolution - operation with electric signal generated by transverter and time distribution function of incoming laser as well as absorption coefficient distribution of standard absorption body.

Description

Measuring method based on the ultrasonic transducer impulse response of optoacoustic effect

Technical field

The invention belongs to the parameter detecting technical field of ultrasonic transducer, particularly a kind of measuring method of the ultrasonic transducer impulse response based on optoacoustic effect.

Background technology

Ultrasonic detecting technology has been widely used in the engineering fields such as fault of construction detection, location and monitoring of structures internal injury process, research material mechanism of fracture.Yet present many laboratories and site test still adopt off-gauge or not proven ultrasonic transducer and equipment, and the measurement result that causes being difficult to the different experiments chamber compares, and also is difficult to draw quantitative experimental result.Therefore, the characteristic of measurement and demarcation ultrasonic transducer is one of important content of the quantitative acoustics Dynamic Non-Destruction Measurement of development, also is simultaneously the basis of estimating and improving transducer characteristics, and this work had been the transducer user both, has also been paid close attention to by the fabricator.

The impulse response of ultrasonic transducer is one of the most basic parameter of ultrasonic transducer, ultrasonic transducer changes ultrasound wave into electric signal, the electric signal that produces equals the convolution of the ultrasonic and transducer impulse response of incident, so will accurately obtain to be measured ultrasonic, just must know the impulse response of ultrasonic transducer, by the contrary convolution algorithm of ultrasonic transducer electric signal and impulse response, can obtain to be measured ultrasonic.But, at present, because technology is limit, all ultrasonic transducer manufacturers can't provide the impulse response of ultrasonic transducer, and the Frequency for Ultrasonic Energy Transducer response can only be provided, and frequency response is the mould of impulse response, determines by the standard sine ultrasound wave of input different frequency.

Summary of the invention

In order to solve above-mentioned the deficiencies in the prior art part, the object of the present invention is to provide a kind of measuring method of the ultrasonic transducer impulse response based on optoacoustic effect.This method is simple to operate, can provide the impulse response of ultrasonic transducer fast.

The present invention is achieved through the following technical solutions, and comprises the steps: based on the measuring method of the ultrasonic transducer impulse response of optoacoustic effect

With standard absorber excitation ultrasound of a bundle of pulsed laser uniform irradiation, ultrasonic transducer to be measured receives this ultrasonic signal, and changes electric signal e (t) into, and then the impulse response h (t) of ultrasonic transducer is $h\left(t\right)=e\left(t\right)\&CircleTimes;[\frac{\mathrm{<figure-callout\; id="2"\; label="c\; L"\; filenames="A20061003420600071.png"\; state="\{\{state\}\}">c</figure-callout>}}{L}2\mathrm{aR}\sin \left(\mathrm{\&theta;}\right)*I^{\&prime;}\left(t\right){]}_{\mathrm{\&theta;}=\mathrm{arc}\left(\frac{L-\mathrm{ct}}{R}\right)},$ Wherein a is the absorption coefficient of standard absorber, R is the radius of standard absorber, c is the velocity of sound, t is the time, L is a ultrasonic transducer to be measured distance apart from the standard absorber center,  represents contrary convolution algorithm, and I ' (t) is the first order derivative of photoelectric sensor measurement incident laser time distribution function I (t).

In order to realize the present invention better, the pulsewidth of described pulse laser is 1 microsecond～1 nanosecond.Described standard absorber is the thin column of uniform absorption; Described standard absorption body and function stained gel is made, and is prepared from as follows: 1 of 100 milliliters in water, agar 5 grams, ink, be heated to boiling, and natural cooling forms; The height of described standard absorber is 0.5～1 millimeter, and the diameter of standard absorber is 5 millimeters～10 millimeters.Described ink can be each chromatic ink such as red, yellow, blue, black.

Described pulse laser incident direction is parallel with the short transverse of standard absorber, and promptly the pulse laser incident direction is vertical with the bottom surface of standard absorber.The normal direction of described ultrasonic transducer measurement face is parallel with the bottom surface of standard absorber, and ultrasonic transducer and standard absorber are positioned at same plane.Described standard absorber and ultrasonic transducer all place water, to reach the acoustic impedance coupling.

Measurement mechanism based on the ultrasonic transducer impulse response of optoacoustic effect is made up of pulsed laser, diffusion sheet, standard absorber, ultrasonic transducer, data acquisition card and computing machine, the laser that pulsed laser sends is diffused as the uniform light of illumination by diffusion sheet, the irradiation standard absorber, accept ultrasonic signal with ultrasonic transducer to be measured and pass to computing machine by data acquisition card, described standard absorber and ultrasonic transducer all place tank.

The present invention is according to the optoacoustic effect theory, and when with the pulsed laser irradiation absorber, absorbent body luminous energy causes temperature rise, and temperature rise causes thermal expansion and produces ultrasound wave, optoacoustic effect that Here it is.(the point source absorber: volume is infinitesimal absorber) is designated as P apart from the ultrasonic signal at point source r0 place when with point source absorber of pulsed laser irradiation _Point(t), $P_{\mathrm{point}}\left(t\right)=\frac{a}{r_0}{I}^{\&prime;}(t-\frac{r_0}{c}),$ A is the absorption coefficient of point source absorber, and t express time, c are the velocities of sound, the first order derivative of I ' expression incident laser time distribution function.Suppose with ultrasonic transducer and survey this ultrasonic signal, h (t) is the impulse response of ultrasonic transducer, then the electric signal e that detects of ultrasonic transducer _Point(t) can be expressed as e _Point(t)=P _Point(t) * h (t), convolution represented in asterisk.Be distributed as the absorber of A (t) for an absorption coefficient, can be regarded as the stack of many point source absorbers, the ultrasonic signal P (t) that such absorber produces can be regarded as the stack of the ultrasonic signal that many point source absorbers produce:

$P\left(t\right)=P_{\mathrm{point}}\left(t\right)*\&Integral;\&Integral;A(\mathrm{ct},\mathrm{\&theta;},\mathrm{\&phi;}){\left(\mathrm{ct}\right)}^2\sin \mathrm{\&theta;d\&theta;d\&phi;}=(\frac{1}{t}\&Integral;\&Integral;A(\mathrm{ct},\mathrm{\&theta;},\mathrm{\&phi;}){\left(\mathrm{ct}\right)}^2\sin \mathrm{\&theta;d\&theta;d\&phi;})*I^{\&prime;}\left(t\right)$

T express time, c are the velocities of sound, and θ and φ are respectively polar angle and the position angle in the spherical coordinates.With impulse response is that the ultrasonic transducer of h (t) is surveyed this ultrasonic signal, and then the electric signal e (t) of Chan Shenging is:

$e\left(t\right)=(\frac{1}{t}\&Integral;\&Integral;A(\mathrm{ct},\mathrm{\&theta;},\mathrm{\&phi;}){\left(\mathrm{ct}\right)}^2\sin \mathrm{\&theta;d\&theta;d\&phi;})*I^{\&prime;}\left(t\right)*h\left(t\right)$ (formula 1)

If therefore with the absorber of a known absorbing coefficient distribution as standard, the laser with a known time distribution function shines simultaneously, promptly in formula 1, $(\frac{1}{t}\&Integral;\&Integral;A(\mathrm{ct},\mathrm{\&theta;},\mathrm{\&phi;}){\left(\mathrm{ct}\right)}^2\sin \mathrm{\&theta;d\&theta;d\&phi;})$ And I ' is known, so, detects the ultrasonic signal that excites with a ultrasonic transducer to be measured, and establishing the detected electric signal of ultrasonic transducer is e (t), then has $h\left(t\right)=e\left(t\right)\&CircleTimes;[(\frac{1}{t}\&Integral;\&Integral;A(\mathrm{ct},\mathrm{\&theta;},\mathrm{\&phi;}){\left(\mathrm{ct}\right)}^2\sin \mathrm{\&theta;d\&theta;d\&phi;})*I^{\&prime;}\left(t\right)].$ Under experimental establishment of the present invention, $\&Integral;\&Integral;A(\mathrm{ct},\mathrm{\&theta;},\mathrm{\&phi;}){\left(\mathrm{ct}\right)}^2\sin \mathrm{\&theta;d\&theta;d\&phi;}=2\mathrm{aR}\sin \left(\mathrm{\&theta;}\right){|}_{\mathrm{\&theta;}=\mathrm{arc}\left(\frac{L-\mathrm{ct}}{R}\right)}$ (∫ ∫ A (ct, θ, φ) (ct) ²Sin θ d θ d φ represents the surface integral to absorber, and the centre of sphere is the receiving plane of ultrasonic transducer, and spherical radius is ct; For the standard absorber among the present invention, can be reduced to plane camber line integration, and because sample and detector are far away, the camber line integration can be approximately the straight line integration, because sample is even absorber, equal constant a simultaneously so establish the absorption coefficient distribution function, so $\&Integral;\&Integral;A(\mathrm{ct},\mathrm{\&theta;},\mathrm{\&phi;}){\left(\mathrm{ct}\right)}^2\sin \mathrm{\&theta;d\&theta;d\&phi;}=2\mathrm{aR}\sin \left(\mathrm{\&theta;}\right){|}_{\mathrm{\&theta;}=\mathrm{arc}\left(\frac{L-\mathrm{ct}}{R}\right)}),$ R represents the radius of standard absorber, and a represents absorption coefficient, establishes L and be ultrasonic transducer to be measured distance apart from the standard absorber center, because in this experimental establishment, L is much larger than the size of standard absorber, so Can be approximated to be

So $h\left(t\right)=e\left(t\right)\&CircleTimes;[\frac{\mathrm{<figure-callout\; id="2"\; label="c\; L"\; filenames="A20061003420600071.png"\; state="\{\{state\}\}">c</figure-callout>}}{L}2\mathrm{aR}\sin \left(\mathrm{\&theta;}\right)*I^{\&prime;}\left(t\right){]}_{\mathrm{\&theta;}=\mathrm{arc}\left(\frac{L-\mathrm{ct}}{R}\right)},$  represents contrary convolution algorithm, can calculate the impulse response h (t) of ultrasonic transducer, theoretical foundation of the present invention that Here it is.

The present invention compared with prior art has the following advantages and beneficial effect:

The inventive method theory is clear, and is simple to operate, can provide impulse response, both comprised the intensity distributions of ultrasonic transducer acoustic-electric conversion, comprises the PHASE DISTRIBUTION of acoustic-electric conversion again.The present invention is based on optoacoustic effect and measure the impulse response that the method for ultrasonic transducer impulse response can be measured ultrasonic transducer more accurately, the performance of raising ultrasonic transducer and the use of ultrasonic transducer all there are important meaning, have good industrial prospect.

Description of drawings

Fig. 1 is a measurement mechanism side view of the present invention.

Fig. 2 is a measurement mechanism vertical view of the present invention.

Embodiment

The present invention is described in further detail below in conjunction with drawings and Examples.

As shown in Figure 1 and Figure 2, measurement mechanism of the present invention is made up of pulsed laser 1 (pulsewidth of pulsed laser is 1 microsecond～1 nanosecond), diffusion sheet 3, standard absorber 4, ultrasonic transducer 5, data acquisition card and computing machine 6.By the laser beam 2 that pulsed laser 1 produces, process diffusion sheet 3 becomes the hot spot 9 of uniform irradiation, and (standard absorber is prepared from irradiation standard absorber 4 as follows: 100 milliliters in water, agar 5 grams, 1 of black ink (0.5 milliliter) is heated to boiling, and natural cooling forms; Standard absorber is the thin column of uniform absorption, and the height of standard absorber is 0.5～1 millimeter, and the diameter of standard absorber is 5 millimeters～10 millimeters).The pulse laser incident direction is parallel with the short transverse of standard absorber 4, and promptly the pulse laser incident direction is vertical with the bottom surface of standard absorber 4.The ultrasonic usefulness that excites ultrasonic transducer 5 to be measured receives, and changes electric signal into, and the electric signal e (t) that records passes to computing machine 6 by data acquisition card, just can draw the impulse response h (t) of ultrasonic transducer 5, $h\left(t\right)=e\left(t\right)\&CircleTimes;[\frac{\mathrm{<figure-callout\; id="2"\; label="c\; L"\; filenames="A20061003420600071.png"\; state="\{\{state\}\}">c</figure-callout>}}{L}2\mathrm{aR}\sin \left(\mathrm{\&theta;}\right)*I^{\&prime;}\left(t\right){]}_{\mathrm{\&theta;}=\mathrm{arc}\left(\frac{L-\mathrm{ct}}{R}\right)},$ Wherein a is the absorption coefficient of standard absorber 4, R is the radius of standard absorber 4, and c is the velocity of sound, and L is a ultrasonic transducer to be measured distance apart from the standard absorber center,  represents contrary convolution algorithm, and I ' (t) is the first order derivative of photoelectric sensor measurement incident laser time distribution function I (t).The normal direction of ultrasonic transducer 5 measurement faces is parallel with the bottom surface of standard absorber 4, and ultrasonic transducer 5 is positioned at same plane with standard absorber 4.Standard absorber 4 and ultrasonic transducer 5 to be measured place tank 8, be full of water 7 in the tank 8,95% of standard absorber 4 is a water, so the density of the density of standard absorber 4 and water is very approaching, therefore ultrasound wave can not produce reflection on the surface of standard absorber 4, reaches the acoustic impedance coupling.

Claims (8)

1, a kind of measuring method of the ultrasonic transducer impulse response based on optoacoustic effect is characterized in that comprising the steps:

With standard absorber excitation ultrasound of a bundle of pulsed laser uniform irradiation, ultrasonic transducer to be measured receives this ultrasonic signal, and changes electric signal e (t) into, and then the impulse response h (t) of ultrasonic transducer is $h\left(t\right)=e\left(t\right)\&CircleTimes;{[\frac{c}{L}2\mathrm{aR}\sin \left(\mathrm{\&theta;}\right)*l^{\&prime;}\left(t\right)]}_{\mathrm{\&theta;}=\mathrm{arc}\left(\frac{L-\mathrm{ct}}{R}\right)},$ Wherein a is the absorption coefficient of standard absorber, R is the radius of standard absorber, and c is the velocity of sound, and L is a ultrasonic transducer to be measured distance apart from the standard absorber center,  represents contrary convolution algorithm, and I ' (t) is the first order derivative of photoelectric sensor measurement incident laser time distribution function I (t).

2, the measuring method of the ultrasonic transducer impulse response based on optoacoustic effect according to claim 1 is characterized in that the pulsewidth of described pulse laser is 1 microsecond～1 nanosecond.

3, the measuring method of the ultrasonic transducer impulse response based on optoacoustic effect according to claim 1 is characterized in that described standard absorber is the thin column of uniform absorption.

4, the measuring method of the ultrasonic transducer impulse response based on optoacoustic effect according to claim 3, it is characterized in that, described standard absorber is prepared from as follows: 1 of 100 milliliters in water, agar 5 grams, ink, be heated to boiling, and natural cooling forms.

5, the measuring method of the ultrasonic transducer impulse response based on optoacoustic effect according to claim 3 is characterized in that described thin column height is 0.5～1 millimeter, and diameter is 5 millimeters～10 millimeters.

6, the measuring method of the ultrasonic transducer impulse response based on optoacoustic effect according to claim 1, it is characterized in that, described pulse laser incident direction is parallel with the short transverse of standard absorber, and promptly the bottom surface of pulse laser incident direction and standard absorber is vertical.

7, the measuring method of the ultrasonic transducer impulse response based on optoacoustic effect according to claim 1 is characterized in that, it is parallel with the bottom surface of standard absorber that described ultrasonic transducer is measured the normal direction of face.

8, the measuring method of the ultrasonic transducer impulse response based on optoacoustic effect according to claim 1 is characterized in that described standard absorber and ultrasonic transducer all place water.

Images