Traceability method and device for a broadband laser vibrometer calibration device

Abstract

A traceability method and device for a broadband laser vibrometer calibration device disclosed by the present invention belong to the technical field of optoelectronic measurement. The device of the present invention includes a laser vibrometer, a first polarization beam splitter, a first acousto-optic modulator, a λ / 4 wave plate, a second polarization beam splitter, a λ / 2 wave plate, a second acousto-optic modulator, a concave mirror, a first sine signal source, an FM signal source, a second sine signal source, a plane mirror, a third polarization beam splitter, a photodetector, a filter amplifier, a data acquisition system, and an electronic computer. The present invention uses the laser frequency and the measurement laser for calibrating the laser vibrometer to perform heterodyne beat frequency, completing the down-conversion of the optical frequency signal; there is no need to use external resources to obtain the FM signal waveform in the radio frequency range. After using the data acquisition system to collect the FM signal in this radio frequency range, the standard vibration quantity value and vibration frequency value reproduced by the broadband laser vibrometer calibration device are obtained by using the FM signal demodulation method, realizing the effective traceability of its quantity value.

Description

Technical Field

[0001] The present invention relates to a traceability method and device for a broadband laser vibrometer calibration device, belonging to the technical field of optoelectronic measurement. Background Art

[0002] A laser vibrometer is a general and fundamental vibration and shock measurement instrument, which is a measurement instrument with high precision, non-contact, and no additional interference and influence on the measured object. Its metrological calibration and performance evaluation have always been difficult problems in the industry. The main reasons are as follows: 1) Its excitation is the amount of motion (displacement, velocity, acceleration), and the measurement principle used is based on the laser Doppler effect. It needs to perceive physical motion through the change of optical frequency, and the output is given in the form of electrical signal data, involving different aspects such as mechanical motion, optical frequency control, and electronic measurement. 2) Since the frequency range and accuracy of optoelectronic measurement are much higher than those of mechanical motion quantities, there has always been a lack of a suitable excitation source for its metrological calibration and performance evaluation, and it is very difficult to find a device and equipment that meet the requirements. 3) Usually, its metrological calibration is carried out by exciting with a "standard vibration table" and measuring the quantity value with a "standard laser vibrometer" to calibrate other laser vibrometers. Since the vibration table is a physical motion device of an electromechanical structure, limited by physical principles, mechanical principles, etc., and limitations such as materials and mechanical processing capabilities, compared with this optoelectronic measurement instrument of a laser vibrometer, its stability is not easy to reach a very high level, the frequency band is narrow, and the amplitude can reach a relatively large quantity value at low frequencies, while in the case of high frequencies, the amplitude can only achieve a very small quantity value, and the accuracy is also low, making it difficult to meet the technical requirements for metrological traceability of broadband laser vibrometer instruments. 4) On the other hand, using a standard laser vibrometer to perform metrological traceability on other laser vibrometers itself also has technical logic problems, and the metrological calibration problem of the standard laser vibrometer itself still cannot be solved.

[0003] A broadband laser vibrometer calibration device uses a double AOM to calibrate the laser vibrometer in an optical frequency modulation manner, overcoming the problem of the ability to excite and calibrate using a mechanical vibration table, and can achieve metrological calibration of laser vibrometers with a wide vibration amplitude and a wide frequency range. However, since it is a relatively specialized instrument device, there is also a problem of how to achieve its quantity value traceability, and it is still impossible to directly perform quantity value traceability in a simple way.

[0004] The technical object of the present invention is a broadband laser vibrometer calibration device, including a laser vibrometer, a first acousto-optic modulator, a second acousto-optic modulator, a concave mirror, a first sine signal source, an FM signal source, and a second sine signal source.

[0005] The laser generated by the laser vibrometer passes through the first acousto-optic modulator and is frequency-shifted by +1 diffraction order generated by the first acousto-optic modulator controlled by the first sine signal source. Then it reaches the second acousto-optic modulator. The second sine signal source generates a sine wave signal to frequency-modulate the FM signal source, generating a modulated FM signal to control the second acousto-optic modulator. The optical frequency transmitted by the first acousto-optic modulator is frequency-shifted and modulated to generate a -1 diffraction order laser. This laser reaches the concave mirror, is reflected and focused, then returns to the second acousto-optic modulator, is frequency-shifted and modulated again by the second acousto-optic modulator, and then is frequency-shifted by the first acousto-optic modulator again and returns to the laser vibrometer, completing the simulation process of vibrating and exciting the laser vibrometer with the sine waveform generated by the second sine signal source. Summary of the Invention

[0006] Aiming at the problem of quantity traceability of "a broadband laser vibrometer calibration device", the main purpose of the present invention is to provide a traceability method and device for a broadband laser vibrometer calibration device, obtaining the laser Doppler vibration signal reproduced by the "broadband laser vibrometer calibration device" by means of heterodyne laser measurement, then demodulating the analog "vibration quantity signal waveform" by means of waveform measurement and FM signal demodulation, obtaining the standard value of the vibration parameter, and tracing it to the time-frequency quantity value through the data acquisition system, so as to realize the quantity traceability of the "broadband laser vibrometer calibration device".

[0007] The object of the present invention is achieved by the following technical solutions:

[0008] A traceability method for a broadband laser vibrometer calibration device disclosed by the present invention obtains the laser Doppler vibration signal reproduced by the broadband laser vibrometer calibration device by means of heterodyne laser measurement, then demodulates the analog "vibration quantity signal waveform" by means of waveform measurement and FM signal demodulation, obtains the standard value of the vibration parameter, and traces it to the time-frequency quantity value through the data acquisition system, so as to realize the quantity traceability of the broadband laser vibrometer calibration device.

[0009] A traceability device for a broadband laser vibrometer calibration device disclosed by the present invention includes a laser vibrometer, a first polarization beam splitter, a first acousto-optic modulator, a λ / 4 wave plate, a second polarization beam splitter, a λ / 2 wave plate, a second acousto-optic modulator, a concave mirror, a first sine signal source, an FM signal source, a second sine signal source, a plane mirror, a third polarization beam splitter, a photodetector, a filter amplifier, a data acquisition system, and an electronic computer.

[0010] The laser generated by the laser vibrometer passes through the first polarization beam splitter and reaches the first acousto-optic modulator. The first acousto-optic modulator controlled by the sine signal generated by the first sine signal source frequency-shifts the laser coming from the first polarization beam splitter by +1 diffraction order, then passes through the λ / 4 wave plate and reaches the second polarization beam splitter where it is divided into two paths.

[0011] One path is transmitted light, which reaches the second acousto-optic modulator. The second sine wave signal source generates a sine wave with frequency Ω, frequency-modulates the FM signal source to obtain a frequency-modulated FM signal to control the second acousto-optic modulator, and performs optical frequency modulation on the laser signal transmitted from the second polarization beam splitter at the -1 diffraction order to obtain frequency-modulated laser light that reaches the concave mirror, is reflected and focused back to the second acousto-optic modulator, and after being modulated again, successively passes through the second polarization beam splitter, the λ / 4 wave plate, and the first acousto-optic modulator, and reaches the first polarization beam splitter, where it is split into two beams.

[0012] One beam directly passes through the first polarization beam splitter and returns to the laser vibrometer, where it is used for laser vibrometer calibration.

[0013] The other beam is reflected by the plane mirror and successively passes through the λ / 2 wave plate and the third polarization beam splitter, where it is combined with and beat-interfered with the laser light that comes from the second polarization beam splitter and is reflected by the third polarization beam splitter.

[0014] Another path of light split off by the reflection of the second polarization beam splitter is reflected by the third polarization beam splitter and is combined with and beat-interfered with the laser light that comes from the direction of the λ / 2 wave plate and passes through the third polarization beam splitter, and reaches the photodetector, where the radio frequency FM signal after beating is read by the photodetector. This radio frequency FM signal is filtered, amplified by the filter amplifier, data-collected by the data acquisition system of the data acquisition system, enters the electronic computer, and after using the FM signal demodulation algorithm, the standard vibration quantity value and vibration frequency value reproduced by "a broadband laser vibrometer calibration device" are obtained, so as to effectively trace the quantity value of the broadband laser vibrometer calibration device.

[0015] Preferably, the first polarization beam splitter and the second polarization beam splitter are respectively used to extract the vibration laser signal and the frequency-shifted laser signal for beam combination and beat to obtain the FM signal waveform in the radio frequency range.

[0016] Preferably, for the used first acousto-optic modulator and the second acousto-optic modulator, their frequency shift and modulation can not only work respectively at the ±1 diffraction order, but also work at other arbitrary diffraction orders such as the ±2 diffraction order and the ±3 diffraction order.

[0017] Beneficial effects:

[0018] 1. A traceability method and device for a broadband laser vibrometer calibration device disclosed by the present invention utilize the laser frequency existing inside the original "broadband laser vibrometer calibration device" and the measurement laser for calibrating the laser vibrometer to perform heterodyne beat frequency, complete the down-conversion behavior of the optical frequency signal, without the need to utilize external resources anymore, and then obtain the FM signal waveform within the radio frequency range. After effectively collecting the FM signal within this radio frequency range using a data acquisition system, the standard vibration quantity value and vibration frequency value reproduced by the "broadband laser vibrometer calibration device" are obtained by using the FM signal demodulation method, thereby achieving the goal of effectively tracing the quantity value thereof.

[0019] 2. A traceability method and device for a broadband laser vibrometer calibration device disclosed by the present invention use the radio frequency parameters of the data acquisition system to realize the quantity value traceability of the "broadband laser vibrometer calibration device". Since the radio frequency quantity value can currently easily reach several tens of gigahertz, which is much higher than the frequency range reproduced by the broadband laser vibrometer and its calibration device, therefore, using the present invention can solve the quantity value traceability problem of any "broadband laser vibrometer calibration device" under the current technical conditions; in addition, the present invention also has the technical advantages of a simple optical path, accurate and reliable quantity value. Brief Description of the Drawings

[0020] Figure 1 It is a schematic structural diagram of a traceability device for a broadband laser vibrometer calibration device of the present invention.

[0021] Wherein: 1 - laser vibrometer, 2 - first polarization beam splitter, 3 - first acousto-optic modulator, 4 - λ / 4 wave plate, 5 - second polarization beam splitter, 6 - λ / 2 wave plate, 7 - second acousto-optic modulator, 8 - concave mirror, 9 - first sine signal source, 10 - FM signal source, 11 - second sine signal source, 12 - plane mirror, 13 - third polarization beam splitter, 14 - photodetector, 15 - filter amplifier, 16 - data acquisition system, 17 - electronic computer. Detailed Embodiments

[0022] In order to better illustrate the purpose and advantages of the present invention, the following further describes the content of the invention in conjunction with the drawings and examples.

[0023] Embodiment 1:

[0024] A traceability method for a broadband laser vibrometer calibration device disclosed in this embodiment obtains the laser Doppler vibration signal reproduced by the "broadband laser vibrometer calibration device" in an external heterodyne laser measurement manner, and then demodulates the analog "vibration quantity value signal waveform" in a waveform measurement and FM signal demodulation manner to obtain the standard value of the vibration parameter, and trace it to the time frequency quantity value through the data acquisition system, thereby realizing the quantity value traceability of the "broadband laser vibrometer calibration device".

[0025] The described broadband laser vibrometer calibration device includes a laser vibrometer, a first acousto-optic modulator, a second acousto-optic modulator, a concave mirror, a first sine signal source, an FM signal source, and a second sine signal source.

[0026] The laser generated by the laser vibrometer passes through the first acousto-optic modulator and is frequency-shifted by +1 order diffraction generated by the first acousto-optic modulator controlled by the first sine signal source, and then reaches the second acousto-optic modulator. The second sine signal source generates a sine wave signal to frequency-modulate the FM signal source, generating a modulated FM signal to control the second acousto-optic modulator, frequency-shifting and modulating the optical frequency transmitted by the first acousto-optic modulator to generate -1 order diffraction laser. This laser reaches the concave mirror, is reflected and focused, then returns to the second acousto-optic modulator, is frequency-shifted and modulated again by the second acousto-optic modulator, and then passes through the first acousto-optic modulator for frequency-shifting and returns to the laser vibrometer, completing the simulation process of vibrating the laser vibrometer with the sine waveform generated by the second sine signal source.

[0027] Embodiment 2:

[0028] As Figure 1 shown, this embodiment discloses a traceability method for a broadband laser vibrometer calibration device, which is implemented based on the traceability device of the described broadband laser vibrometer calibration device. The traceability device of the described broadband laser vibrometer calibration device is composed of a laser vibrometer 1, a first polarization beam splitter 2, a first acousto-optic modulator 3, a λ / 4 wave plate 4, a second polarization beam splitter 5, a λ / 2 wave plate 6, a second acousto-optic modulator 7, a concave mirror 8, a first sine signal source 9, an FM signal source 10, a second sine signal source 11, a plane mirror 12, a third polarization beam splitter 13, a photodetector 14, a filter amplifier 15, a data acquisition system 16, and an electronic computer 17.

[0029] The laser generated by the laser vibrometer 1 passes through the first polarization beam splitter 2 and reaches the first acousto-optic modulator 3. The first acousto-optic modulator 3 controlled by the sine signal generated by the first sine signal source 9 frequency-shifts the laser coming from the first polarization beam splitter 2 by +1 diffraction order, then passes through the λ / 4 wave plate 4 and reaches the second polarization beam splitter 5, where it is split into two paths.

[0030] One path is the transmitted light, which reaches the second acousto-optic modulator 7. The second sine signal source 11 generates a sine wave with frequency Ω, frequency-modulates the FM signal source 10 to obtain a frequency-modulated FM signal to control the second acousto-optic modulator 7, performs optical frequency modulation on the laser signal transmitted from the second polarization beam splitter 5 at the -1 diffraction order, obtains a frequency-modulated laser that reaches the concave mirror 8, is reflected and focused back to the second acousto-optic modulator 7, and after being modulated again, successively passes through the second polarization beam splitter 5, the λ / 4 wave plate 4, and the first acousto-optic modulator 3, and reaches the first polarization beam splitter 2, where it is split into two beams.

[0031] One beam directly passes through the first polarization beam splitter 2 and returns to the laser vibrometer 1, where it is used for the calibration of the laser vibrometer.

[0032] The other beam is reflected by the plane mirror 12 and successively passes through the λ / 2 wave plate 6 and the third polarization beam splitter 13, where it is combined with and beat-interferes with the laser beam that comes from the second polarization beam splitter 5 and is reflected by the third polarization beam splitter 13 at the third polarization beam splitter 13.

[0033] Another path of light split by the second polarization beam splitter 5 is reflected by the third polarization beam splitter 13, combined with and beat-interferes with the laser beam that comes from the direction of the λ / 2 wave plate 6 and passes through the third polarization beam splitter 13, reaches the photodetector 14, and the radio-frequency FM signal after beat is read by the photodetector 14. This radio-frequency FM signal is filtered and amplified by the filter amplifier 15, data is collected by the data acquisition system 16 of the data acquisition system, enters the electronic computer 17, and after using the FM signal demodulation algorithm, the standard vibration quantity value and vibration frequency value reproduced by "a broadband laser vibrometer calibration device" are obtained, thus achieving the goal of effectively tracing the quantity value thereof.

[0034] The above specific description further details the purpose, technical solution, and beneficial effects of the invention. It should be understood that the above is only a specific embodiment of the present invention and is not used to limit the protection scope of the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A traceability method for a calibration device of a broadband laser vibrometer, characterized in that: Obtain the laser Doppler vibration signal reproduced by "a broadband laser vibrometer calibration device" through a heterodyne laser measurement method, then demodulate the analog "vibration quantity signal waveform" through waveform measurement and FM signal demodulation methods to obtain the standard value of the vibration parameter, and trace it to the time-frequency quantity value through the data acquisition system, so as to realize the quantity value traceability of "a broadband laser vibrometer calibration device"; The described broadband laser vibrometer calibration device includes a laser vibrometer (1), a first acousto-optic modulator (3), a second acousto-optic modulator (7), a concave mirror (8), a first sine signal source (9), an FM signal source (10), and a second sine signal source (11); The laser generated by the laser vibrometer passes through the first acousto-optic modulator (3) and is frequency-shifted by +1 order diffraction generated by the first acousto-optic modulator (3) controlled by the first sine signal source (9), and then reaches the second acousto-optic modulator (7). The second sine signal source (11) generates a sine wave signal to frequency-modulate the FM signal source (10) to generate a modulated FM signal to control the second acousto-optic modulator (7), frequency-shift and modulate the optical frequency transmitted by the first acousto-optic modulator (3) to generate a -1 order diffraction laser. This laser reaches the concave mirror (8) and is reflected and focused, then returns to the second acousto-optic modulator (7), is frequency-shifted and modulated again by the second acousto-optic modulator (7), and then passes through the first acousto-optic modulator (3) for frequency-shifting and returns to the laser vibrometer (1), completing the simulation process of vibrating the laser vibrometer (1) with the sine waveform generated by the second sine signal source (11).

2. Traceability device for a broadband laser vibrometer calibration device, characterized in that: It includes a laser vibrometer (1), a first polarization beam splitter (2), a first acousto-optic modulator (3), a λ / 4 wave plate (4), a second polarization beam splitter (5), a λ / 2 wave plate (6), a second acousto-optic modulator (7), a concave mirror (8), a first sine signal source (9), an FM signal source (10), a second sine signal source (11), a plane mirror (12), a third polarization beam splitter (13), a photodetector (14), a filter amplifier (15), a data acquisition system (16), and an electronic computer (17); The laser generated by the laser vibrometer (1) passes through the first polarization beam splitter (2) and reaches the first acousto-optic modulator (3). The first acousto-optic modulator (3) controlled by the sine signal generated by the first sine signal source (9) frequency-shifts the laser coming from the first polarization beam splitter (2) by +1 diffraction order, then passes through the λ / 4 wave plate (4), and after reaching the second polarization beam splitter (5), is split into two paths; One path is the transmitted light, which reaches the second acousto-optic modulator (7). The second sine signal source (11) generates a sine wave with frequency W, frequency-modulates the FM signal source (10) to obtain a frequency-modulated FM signal to control the second acousto-optic modulator (7), and performs optical frequency modulation on the laser signal transmitted from the second polarization beam splitter (5) at the -1 diffraction order to obtain frequency-modulated laser light that reaches the concave mirror (8), is reflected and focused back to the second acousto-optic modulator (7), and after being modulated again, passes through the second polarization beam splitter (5), λ / 4 wave plate (4), and first acousto-optic modulator (3) in sequence, and reaches the first polarization beam splitter (2), where it is split into two beams; One beam directly passes through the first polarization beam splitter (2) and returns to the laser vibrometer (1) to be used for the calibration of the laser vibrometer; The other beam is reflected by the plane mirror (12) and passes through the λ / 2 wave plate (6) and the third polarization beam splitter (13) in sequence, and at the third polarization beam splitter (13), it is combined with the laser light from the second polarization beam splitter (5) that is reflected by the third polarization beam splitter (13) for beat-frequency interference; The other path of light reflected and separated by the second polarization beam splitter (5) is reflected by the third polarization beam splitter (13) and combined with the laser light coming from the direction of the λ / 2 wave plate (6) and passing through the third polarization beam splitter (13) for beat-frequency interference, and reaches the photodetector (14). The photodetector (14) reads the radio-frequency FM signal after beat frequency. This radio-frequency FM signal passes through the filter amplifier (15) for filtering and amplification, is collected by the data acquisition system (16), enters the electronic computer (17), and after using the FM signal demodulation algorithm, the standard vibration quantity value and vibration frequency value reproduced by "a broadband laser vibrometer calibration device" are obtained, thereby realizing the effective traceability of the quantity value of the broadband laser vibrometer calibration device; The described broadband laser vibrometer calibration device includes a laser vibrometer (1), a first acousto-optic modulator (3), a second acousto-optic modulator (7), a concave mirror (8), a first sine signal source (9), an FM signal source (10), and a second sine signal source (11); The laser generated by the laser vibrometer passes through the first acousto-optic modulator (3) and is frequency-shifted by +1 diffraction order generated by the first acousto-optic modulator (3) controlled by the first sine signal source (9), and then reaches the second acousto-optic modulator (7). The second sine signal source (11) generates a sine wave signal to frequency-modulate the FM signal source (10) to generate a frequency-modulated FM signal to control the second acousto-optic modulator (7), frequency-shift and modulate the optical frequency transmitted from the first acousto-optic modulator (3) to generate -1 diffraction order laser light. This laser light reaches the concave mirror (8), is reflected and focused, and then returns to the second acousto-optic modulator (7), and is frequency-shifted and modulated again by the second acousto-optic modulator (7). Then, it is frequency-shifted by the first acousto-optic modulator (3) again and returns to the laser vibrometer (1), completing the simulation process of vibrating the laser vibrometer (1) with the sine waveform generated by the second sine signal source (11).

3. The traceability device of a broadband laser vibrometer calibration device according to claim 2, characterized in that: The vibration laser signal is extracted using the first polarization beam splitter (2), and the frequency-shifted laser signal is extracted using the second polarization beam splitter (5), and then they are combined and beat to obtain the FM signal waveform in the radio frequency range.

4. The traceability device of a broadband laser vibrometer calibration device according to claim 2, characterized in that: For the used first acousto-optic modulator (3) and second acousto-optic modulator (7), their frequency shifting and modulation can not only work separately at the ±1st diffraction order, but also at the ±2nd diffraction order and ±3rd diffraction order.

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