High-directivity diaphragm optical test system and test method thereof

Abstract

The invention belongs to the technical field of underwater acoustic measurement, and particularly relates to a high-directivity diaphragm optical test system and a test method thereof.The high-directivity diaphragm optical test system comprises a transmitting transducer, a diaphragm array, light-transmitting glass, a laser vibration meter, a high-precision optical positioning and moving mechanism and a data acquisition and analysis module. Through sound field scanning and post signal processing and correction, the system can have an extremely narrow beam width in a specific frequency range, realizes directional measurement of a high-frequency transducer, and can effectively suppress the influence of other multipath reflection on measurement due to the extremely narrow beam width.

Description

Technical Field

[0001] The invention belongs to the technical field of underwater acoustic measurement, and in particular relates to a high-directivity diaphragm optical testing system and a testing method thereof. Background Art

[0002] With the development of hydroacoustic technology, hydroacoustic measurement plays an important role in ensuring the performance indicators and normal use of hydroacoustic equipment. The free field is the sound field closest to the actual working environment of hydroacoustic equipment such as transducers and hydrophones. Therefore, the research on free field calibration plays an important role in ensuring the development and practical application of hydroacoustic transducers and hydrophones.

[0003] The transmitting response of the transmitting transducer is the most commonly used technical indicator for evaluating the performance of the transducer, and its performance is usually measured in an experimental water pool. High-frequency transmitting transducers are widely used in underwater acoustics, ultrasound, medical and other fields, and the accuracy of their acoustic performance will directly affect their final application effect. For a long time, high-frequency underwater acoustic fields have been often measured by hydrophones, and there are two problems with measuring with hydrophones: 1) The hydrophone itself has a certain volume, and the sound pressure measured by the hydrophone is the average value around the hydrophone's own sound field. This method has the problem of low resolution; 2) Some transmitting transducers have high directivity, and a simple hydrophone cannot achieve high-precision resolution of the beam. The optical method is a non-contact underwater acoustic measurement test method with high measurement accuracy, which is suitable for high-frequency measurement of underwater acoustic pressure. To this end, optical metrology test methods have been studied at home and abroad. The metrology institutes of countries such as the United Kingdom and Germany have established high-frequency ultrasonic and underwater acoustic national standards in laboratories based on the optical method, with the highest frequency reaching 60MHz, which has further expanded the measurement frequency range of the optical method.

[0004] These methods have achieved the measurement of high-frequency transducers and hydrophone water acoustic parameters to a certain extent. At present, the development and application demand of high-directional transducers is becoming more and more obvious, and traditional measurement methods still have problems such as poor measurement accuracy and low spatial resolution. Summary of the invention

[0005] In view of the technical difficulty that the directivity of the high-frequency transmitting transducer is narrow and cannot be measured using traditional hydrophones, the present invention proposes the following technical solutions:

[0006] A high-directivity diaphragm optical test system comprises a transmitting transducer, a diaphragm array, light-transmitting glass, a laser vibrometer, a high-precision optical positioning and motion mechanism, and a data acquisition and analysis module. The laser vibrometer generates a laser beam, which is focused to the center of the diaphragm array through the light-transmitting glass. The laser vibrometer is used to detect the vibration of the center of the diaphragm array, and the laser vibrometer is installed on the high-precision optical positioning and motion mechanism. The high-precision optical positioning and motion mechanism drives the laser vibrometer to realize three-dimensional motion and angular rotation. The data acquisition and analysis module is used to collect data from the laser vibrometer, control the motion of the high-precision optical positioning and motion mechanism, and calculate and analyze the test data.

[0007] Furthermore, the three-dimensional positioning repetition accuracy of the high-precision optical positioning and motion mechanism is L≤λ / 10, where λ is the wavelength.

[0008] Furthermore, the scanning area of ​​the laser vibrometer on the diaphragm array is a rectangular area, the number of scanning points for each side of the rectangular area is n, n≥20, and the number of scanning points is not less than 400.

[0009] Furthermore, the short side of the rectangular area is represented by x, and the spatial position of each scanning point in the short side direction is x i , i = 1, 2, 3, ..., the distance between adjacent scanning points in the short side direction is Δx, x = n·Δx, ​​the long side of the rectangular area is y, and the spatial position of each scanning point in the long side direction is y i , i=1,2,3,…, the distance between adjacent scanning points in the long side direction is Δy, y=n·Δy.

[0010] Furthermore, during the scanning process of the laser vibrometer, the signal of each scanning point is kept synchronous over time, and the initial phase is kept consistent.

[0011] Furthermore, the spatial gain function of any of the scanning points can be expressed as

[0012]

[0013] Where k is the acoustic wave number, θ and is the spatial angle.

[0014] Furthermore, there is a certain difference in the vibration of any particle on the diaphragm array, which is represented by a correction coefficient W(x, y). The coefficient is obtained through the size relationship of the diaphragm array to correct the vibration error of any particle.

[0015] A testing method using the highly directional film optical testing system comprises the following steps:

[0016] S1. Fix the transmitting transducer on the measuring bracket so that the main axis direction of the transmitting transducer is aligned with the center of the diaphragm array, and the diaphragm array is perpendicular to the main axis direction of the transmitting transducer;

[0017] S2. Align the laser vibrometer to the center of the diaphragm array. Align the laser beam generated by the laser vibrometer to the center of the diaphragm array. Note that this position is the origin (0,0). After the laser beam is focused to the center of the diaphragm array and reflected back to the laser vibrometer, the vibration velocity of the particle at the origin of the diaphragm array is measured.

[0018] S3, control the transmitting transducer to generate a pulse sound wave, at which time the open circuit voltage of the laser vibrometer is U(0,0), and the particle velocity in the sound field is V(0,0)=U(0,0)×K, where K is the conversion coefficient of the laser vibrometer;

[0019] S4, control the high-precision optical positioning and motion mechanism to make the laser vibrometer scan in the (x, y) plane, and the laser beam is aligned with the diaphragm array P(x i ,y i ) position, the laser vibrometer outputs U(x i ,y i ), at this time the sound field P(x i ,y i ) position particle velocity is V(x i ,y i )=K·U(x i ,y i )·W(x i ,y i );

[0020] S5. The signals are superimposed and processed to obtain the vibration velocities of the center point in the horizontal and vertical directions as follows: and

[0021] S6. Further, the vibration velocity in the main axis direction of the transmitting transducer is V=V(x) / n(x direction)V=V(y) / n(y direction), and the vibration velocity in any direction is

[0022] In general, the above technical solutions conceived by the present invention can achieve the following beneficial effects compared with the prior art:

[0023] By using the test system of the present invention, the underwater radiation sound field of the high-frequency transmitting transducer can be measured in a free field. Through sound field scanning and subsequent signal processing and correction, an extremely narrow beam width can be obtained within a specific frequency range to achieve the measurement of the directivity of the high-frequency transducer. At the same time, due to the extremely narrow beam width, the system can effectively suppress the influence of other multipath reflected waves on the measurement. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 A system structure diagram of a high-directivity diaphragm optical testing system of the present invention;

[0025] Figure 2 This is a measurement result diagram of the high directivity of the high-frequency transducer under the diaphragm array of the present invention.

[0026] The following are marked in the figure:

[0027] 1-transmitting transducer, 2-diaphragm array, 3-laser beam, 4-light-transmitting glass, 5-laser vibrometer, 6-high-precision optical positioning and motion mechanism. DETAILED DESCRIPTION

[0028] The following is a clear and complete description of the technical solutions in the embodiments of the present application in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of them. Based on the embodiments, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0029] Combined with Figure 1 As shown, a high-directivity diaphragm optical test system includes a transmitting transducer 1, a diaphragm array 2, a light-transmitting glass 4, a laser vibrometer 5, a high-precision optical positioning and motion mechanism 6, and a data acquisition and analysis module. The laser vibrometer 5 generates a laser beam 3, and the laser beam 3 is focused to the center of the diaphragm array 2 through the light-transmitting glass 4. The laser vibrometer 5 is used to detect the vibration of the center of the diaphragm array 2, and the laser vibrometer 5 is installed on the high-precision optical positioning and motion mechanism 6. The high-precision optical positioning and motion mechanism 6 drives the laser vibrometer 5 to achieve three-dimensional movement and angular rotation. The data acquisition and analysis module is used to collect data from the laser vibrometer 5, control the movement of the high-precision optical positioning and motion mechanism 6, ensure that it can achieve scanning, and calculate and analyze subsequent test data. Among them, the transmitting transducer 1 is a transducer to be measured that can emit high-frequency sound waves, the diaphragm array 2 is a diaphragm that vibrates freely with the sound field, and the vibrating diaphragm is used to sense the vibration of the sound field. The diaphragm resonates with the sound field particles in a certain small area. The laser vibrometer 5 generates a laser beam 3 that is focused on the diaphragm array 2, and then the laser vibrometer 5 measures the vibration velocity of the diaphragm array 2. The high-precision optical positioning and motion mechanism 6 can realize precise positioning and control of the laser vibrometer 5.

[0030] In addition, the laser beam 3 has a smaller focus after being focused by the light-transmitting glass 4, and can measure the particle vibration at any point in space. The size of the focus is usually less than 1 mm, thereby achieving high-resolution measurement.

[0031] Specifically, the three-dimensional positioning repetition accuracy of the high-precision optical positioning and motion mechanism 6 is L≤λ / 10, where λ is the wavelength.

[0032] Specifically, the scanning area of ​​the laser vibrometer 5 on the diaphragm array 2 is a rectangular area, the number of scanning points of each side of the rectangular area is n, n≥20, and the number of scanning points is not less than 400.

[0033] Specifically, the short side of the rectangular area is represented by x, and the spatial position of each scanning point in the short side direction is x i , i = 1, 2, 3, ..., the distance between adjacent scanning points in the short side direction is Δx, x = n·Δx, ​​the long side of the rectangular area is y, and the spatial position of each scanning point in the long side direction is y i , i=1,2,3,…, the distance between adjacent scanning points in the long side direction is Δy, y=n·Δy.

[0034] Specifically, during the scanning process of the laser vibrometer 5 , the signal of each scanning point is kept synchronous over time, and the initial phase is kept consistent.

[0035] Specifically, the spatial gain function of any of the scanning points can be expressed as

[0036]

[0037] Where k is the acoustic wave number, θ and is the spatial angle.

[0038] Specifically, there is a certain difference in the vibration of any particle on the diaphragm array 2, which is represented by a correction coefficient W (x, y). The coefficient is obtained through the size relationship of the diaphragm array 2 to correct the vibration error of any particle.

[0039] A testing method using the highly directional film optical testing system comprises the following steps:

[0040] S1, fix the transmitting transducer 1 on the measuring bracket, align the main axis direction of the transmitting transducer 1 with the center of the diaphragm array 2, and the diaphragm array 2 is perpendicular to the main axis direction of the transmitting transducer 1. At this time, the transmitting transducer 1 and the diaphragm array 2 are both fixed in water;

[0041] S2, align the laser vibrometer 5 with the center of the diaphragm array 2, align the laser beam 3 generated by the laser vibrometer 5 with the center of the diaphragm array 2, and the diaphragm array 2 is perpendicular to the laser emission direction of the laser vibrometer 5, so that the laser can be reflected from the diaphragm array 2 back to the laser vibrometer 5, and the laser beam 3 is focused to the center of the diaphragm array 2 and reflected back to the laser vibrometer 5, so as to measure the vibration velocity of the particle at the origin position of the diaphragm array 2. At this time, the coordinate of the particle at the origin position of the diaphragm array 2 is P(0,0);

[0042] S3, controlling the transmitting transducer 1 to generate a pulse signal in the underwater sound field, at which time the open circuit voltage of the laser vibrometer 5 is U(0,0), and the particle velocity in the sound field is V(0,0)=U(0,0)×K, where K is the conversion coefficient of the laser vibrometer 5;

[0043] S4, control the high-precision optical positioning and motion mechanism 6 to make the laser vibrometer 5 scan in the (x, y) plane, and the laser beam 3 is aligned with P (x) in the diaphragm array 2 in turn. i ,y i ) position, the laser vibrometer 5 outputs U(x i ,y i ), at this time the sound field P(x i ,y i ) position particle velocity is V(x i ,y i )=K·U(x i ,y i )·W(x i ,y i );

[0044] S5. The signals are superimposed and processed to obtain the vibration velocities of the center point in the horizontal and vertical directions as follows: and

[0045] S6. Further, the vibration velocity in the main axis direction of the transmitting transducer 1 is V=V(x) / n(x direction)V=V(y) / n(y direction), and the vibration velocity in any direction is

[0046] As attached Figure 2 As shown in the figure, the measurement result of the directivity of the transmitting transducer 1 under the diaphragm array 2 is that when the transmitting transducer 1 is at the main beam opening angle at the frequency point of 10MHz, its beam angle is about 0.25° under the condition of attenuation within 6dB. The system has an extremely narrow beam width within a specific frequency range and can measure the directivity of high-frequency transducers. At the same time, due to the extremely narrow beam width, the system can effectively suppress the influence of other multipath reflections on the measurement.

[0047] The above are only preferred implementations of the present invention, but the protection scope of the present invention is not limited thereto, and any modification and replacement based on the technical solutions and inventive concepts provided by the present invention should be covered within the protection scope of the present invention.

Claims

1. A high-directivity film optical testing system, characterized in that: The invention comprises a transmitting transducer (1), a diaphragm array (2), a light-transmitting glass (4), a laser vibrometer (5), a high-precision optical positioning and motion mechanism (6), and a data acquisition and analysis module. The laser vibrometer (5) generates a laser beam (3). The laser beam (3) is focused to the center of the diaphragm array (2) through the light-transmitting glass (4). The laser vibrometer (5) is used to detect the vibration of the center of the diaphragm array (2). The laser vibrometer (5) is installed on the high-precision optical positioning and motion mechanism (6). The high-precision optical positioning and motion mechanism (6) drives the laser vibrometer (5) to realize three-dimensional motion and angular rotation. The data acquisition and analysis module is used to collect data of the laser vibrometer (5), control the motion of the high-precision optical positioning and motion mechanism (6), and calculate and analyze the test data.

2. The high-directivity film optical testing system according to claim 1, characterized in that: The high-precision optical positioning and motion mechanism (6) has a three-dimensional positioning repetition accuracy of L≤λ / 10, where λ is the wavelength.

3. The high-directivity film optical testing system according to claim 2, characterized in that: The scanning area of ​​the laser vibrometer (5) on the diaphragm array (2) is a rectangular area, the number of scanning points for each side of the rectangular area is n, n≥20, and the number of scanning points is not less than 400.

4. The high-directivity film optical testing system according to claim 3, characterized in that: The short side of the rectangular area is represented by x, and the spatial position of each scanning point in the short side direction is x i , i = 1, 2, 3, ..., the distance between adjacent scanning points in the short side direction is Δx, x = n·Δx, ​​the long side of the rectangular area is y, and the spatial position of each scanning point in the long side direction is y i , i=1,2,3,…, the distance between adjacent scanning points in the long side direction is Δy, y=n·Δy.

5. The high-directivity film optical testing system according to claim 3, characterized in that: During the scanning process of the laser vibrometer (5), the signal of each scanning point is kept synchronous over time, and the initial phase is kept consistent.

6. The high-directivity film optical testing system according to claim 3, characterized in that: The spatial gain function of any scanning point can be expressed as Where k is the acoustic wave number, θ and is the spatial angle.

7. The high-directivity film optical testing system according to claim 1, characterized in that: There is a certain difference in the vibration of any particle on the diaphragm array (2), which is represented by a correction coefficient W (x, y). The coefficient is obtained through the size relationship of the diaphragm array (2) to achieve correction of the vibration error of any particle.

8. A testing method using the high-directivity film optical testing system according to any one of claims 1 to 7, characterized in that: The following steps are involved: S1. Fixing the transmitting transducer (1) on a measuring bracket so that the main axis direction of the transmitting transducer (1) is aligned with the center of the diaphragm array (2), and the main axis directions of the diaphragm array (2) and the transmitting transducer (1) are perpendicular; S2, aligning the laser vibrometer (5) with the center of the diaphragm array (2), aligning the laser beam (3) generated by the laser vibrometer (5) with the center of the diaphragm array (2), and recording the position here as the origin (0,0), and focusing the laser beam (3) to the center of the diaphragm array (2) and reflecting back to the laser vibrometer (5), thereby realizing the measurement of the vibration velocity of the particle at the origin position of the diaphragm array (2); S3, controlling the transmitting transducer (1) to generate a pulse sound wave, at which time the open circuit voltage of the laser vibrometer (5) is U(0,0), and at which time the particle velocity in the sound field is V(0,0)=U(0,0)×K, where K is the conversion coefficient of the laser vibrometer (5); S4, control the high-precision optical positioning and motion mechanism (6) to make the laser vibrometer (5) scan in the (x, y) plane, and the laser beam (3) is sequentially aligned with the diaphragm array (2) P (x i ,y i ) position, the laser vibrometer (5) outputs U(x i ,y i ), at this time the sound field P(x i ,y i ) position particle velocity is V(x i ,y i )=K·U(x i ,y i )·W(x i ,y i ); S5. The signals are superimposed and processed to obtain the vibration velocities of the center point in the horizontal and vertical directions as follows: and S6. Further, the vibration velocity in the main axis direction of the transmitting transducer (1) is V=V(x) / n(x direction)V=V(y) / n(y direction), and the vibration velocity in any direction is

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