A calibration and traceability device for concave mirror reflection focusing laser vibrometer

Abstract

A calibration and traceability device for a concave mirror reflection focusing type laser vibrometer disclosed by the present invention belongs to the technical field of optoelectronic measurement. By virtue of the original structural features of the "calibration device for a concave mirror reflection focusing type laser vibrometer" to be traced, the laser in the intermediate link is used as the demodulation object, the laser frequency control signal waveform of the optical frequency modulator is obtained, the modulation waveform information is extracted, and the signal waveform sequence is obtained by means of high-speed data acquisition and quantization technology. The instantaneous frequency of the laser frequency control signal waveform is accurately demodulated in a digital manner, and then the vibration velocity waveform and vibration acceleration waveform as standards are obtained, so as to realize the value traceability of the sinusoidal waveform modulation signal to the superior parameters through the data acquisition system. The present invention uses the digital demodulation principle and method, can obtain good convergence, has high measurement accuracy, and has good self-adaptability to the situation where the carrier is non-stationary and the amplitude envelope changes violently.

Description

Technical Field

[0001] The present invention relates to a calibration and traceability device for a concave mirror reflection focusing type laser vibrometer, 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 is necessary 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 values, there has always been a lack of a suitable excitation source for its metrological calibration and performance evaluation, and it is 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 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 value at low frequencies. In the case of high frequencies, the amplitude can only achieve a very small value, and the accuracy is also low, and it is not easy to meet the technical requirements for metrological traceability of laser vibration measurement. Although a standard laser vibrometer is used for metrological calibration, the uncertainty caused by the characteristics of the vibration table and the limitations caused by its amplitude and frequency range are still the main problems existing in the metrological calibration of laser vibrometers. 4) On the other hand, when using a standard laser vibrometer to perform metrological traceability on other laser vibrometers, there is still a logical problem that the metrological calibration problem of the standard laser vibrometer itself still cannot be solved.

[0003] "A calibration device for a concave mirror reflection focusing type laser vibrometer" is a special device designed and invented specifically for the metrological calibration and performance evaluation of laser vibrometers. It can perform frequency modulation on the laser emitted by the laser vibrometer to be evaluated in a sine waveform optical frequency modulation mode, so as to realize the excitation of the laser vibrometer to be evaluated in a sine waveform manner. Since it has gone through the optical frequency modulation link, whether the sine waveform used as the actual excitation maintains the technical characteristics of the original electronic signal waveform needs to be realized in a metrological calibration manner. However, it cannot be simply operated by direct measurement with existing measuring instruments to achieve metrological calibration and traceability, thus leading to the traceability problem of "a calibration device for a concave mirror reflection focusing type laser vibrometer". Summary of the Invention

[0004] The main object of the present invention is to provide a calibration and traceability device for a concave mirror reflection focusing type laser vibrometer. Based on the technology of "a calibration device for a concave mirror reflection focusing type laser vibrometer", through the precise demodulation of the waveform of the modulated laser signal in the optical frequency modulation device, the demodulation result of its sine waveform is obtained, and the traceability of "a calibration device for a concave mirror reflection focusing type laser vibrometer" is realized through the index parameters of the data acquisition system. The present invention has the advantages of compact and small structure, easy system integration, good convergence, good stability and high accuracy.

[0005] The object of the present invention is achieved by the following technical solutions:

[0006] A calibration and traceability device for a concave mirror reflection focusing type laser vibrometer of the present invention includes a laser vibrometer, a first λ / 2 wave plate, a second λ / 2 wave plate, a third λ / 2 wave plate, a fourth λ / 2 wave plate, a fifth λ / 2 wave plate, a first polarization beam splitter, a second polarization beam splitter, a third polarization beam splitter, a fourth polarization beam splitter, a first concave mirror, a second concave mirror, a first plane mirror, a second plane mirror, a third plane mirror, a fourth plane mirror, a first acousto-optic modulator, a second acousto-optic modulator, an FM signal source, a first sine signal source, a second sine signal source, a photodetector, a filter amplifier, a data acquisition system and an electronic computer.

[0007] The laser generated by the laser vibrometer passes through the first polarization beam splitter, the second polarization beam splitter, and the first λ / 2 wave plate in sequence and reaches the first acousto-optic modulator. The first sine signal source generates the required sine waveform modulation signal to control the first acousto-optic modulator, shift the frequency of the laser signal coming from the direction of the first λ / 2 wave plate, and generate the -1st order diffracted light, which is then reflected and focused by the first concave mirror, returns to the first acousto-optic modulator to continue frequency shifting, then passes through the first λ / 2 wave plate, is reflected by the second polarization beam splitter, passes through the fourth λ / 2 wave plate, and is divided into two paths after passing through the third polarization beam splitter.

[0008] One path is the reflected light, which passes through the third λ / 2 wave plate after being reflected by the third polarization beam splitter and reaches the second acousto-optic modulator. The second sine signal source generates the required sine waveform modulation signal to frequency modulate the FM signal source to generate the modulated FM signal. By controlling the second acousto-optic modulator, the laser coming from the third λ / 2 wave plate is frequency shifted and modulated to generate the +1st order diffracted laser, which is reflected and focused by the second concave mirror, returns to the second acousto-optic modulator to be frequency shifted and modulated again, passes through the third λ / 2 wave plate and the third polarization beam splitter in sequence, is reflected by the plane mirror, passes through the second λ / 2 wave plate, and reaches the first polarization beam splitter and is divided into two beams of light:

[0009] One beam is the reflected light, which returns to the calibrated laser vibrometer after being reflected by the first polarization beam splitter for measurement and processing, completing the simulation process of vibrating the laser vibrometer with the sine waveform generated by the second sine signal source.

[0010] The other beam is the transmitted light. After passing through the first polarization beam splitter, it is reflected by the fourth plane mirror, passes through the fourth polarization beam splitter, and is combined and beat with the laser from the fifth λ / 2 wave plate.

[0011] Another path is the transmitted light. After being reflected by passing through the third polarization beam splitter, it is successively reflected by the second plane mirror and the third plane mirror, passes through the fifth λ / 2 wave plate, reaches the fourth polarization beam splitter, is reflected by the fourth polarization beam splitter, and is combined and beat with the laser coming from the direction of the fourth plane mirror, reaches the photodetector, is received by the photodetector and converted into an RF FM electrical signal. This electrical signal is amplified by a filter amplifier, reaches the data acquisition system for acquisition and storage to obtain the signal waveform, is transmitted to an electronic computer for waveform demodulation processing, and obtains the demodulation result of the sine waveform for modulation output by the second sine signal source. Thus, the quantity value traceability of the sine waveform modulation signal to the superior parameter through the data acquisition system is realized, that is, the traceability of the concave mirror reflection focusing type laser vibrometer calibration device is realized.

[0012] Beneficial effects:

[0013] 1. A concave mirror reflection focusing type laser vibrometer calibration and traceability device disclosed by the present invention fully utilizes the original structural characteristics of the "concave mirror reflection focusing type laser vibrometer calibration device" to be traced, uses the intermediate laser as the demodulation object, extracts the modulation waveform information, and outputs the standard vibration quantity value reproduced in the optical frequency modulation mode, thereby completing the traceability of the "concave mirror reflection focusing type laser vibrometer calibration device", significantly simplifying the volume, structure and the used optoelectronic components of the system, making the structure more compact and small, and being easy for system integration.

[0014] 2. Regarding the demodulation of the frequency modulation signal waveform, a concave mirror reflection focusing type laser vibrometer calibration and traceability device disclosed by the present invention uses the digital demodulation principle and method. Compared with the hardware method, the present invention can obtain good convergence, has high measurement accuracy, and has good self - adaptability to the situation where the carrier is non - stationary and the amplitude envelope changes violently.

[0015] 3. A concave mirror reflection focusing type laser vibrometer calibration device disclosed by the present invention obtains the laser frequency control signal waveform of the optical frequency modulator, obtains the signal waveform sequence by means of high - speed data acquisition and quantization technology, realizes the precise demodulation of the instantaneous frequency of the laser frequency control signal waveform in a digital manner, and then obtains the vibration velocity waveform and vibration acceleration waveform as standards, and finally solves the problems of dynamic measurement and quantity value traceability of the laser vibrometer itself.

[0016] 4. A calibration device for a concave mirror reflection focusing type laser vibrometer disclosed by the present invention traces the magnitude of a linear motion signal (linear motion speed, linear motion acceleration) to a frequency magnitude through frequency modulation and demodulation techniques. Therefore, in principle, it has higher measurement accuracy and stability than mechanical motion excitation. Because the frequency magnitude is a physical quantity with the highest measurement accuracy that people can achieve in today's metrology industry, far higher than any other physical quantity. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic structural diagram of a calibration device for a concave mirror reflection focusing type laser vibrometer disclosed by the present invention.

[0018] Wherein: 1 - laser vibrometer, 2 - first polarization beam splitter, 3 - second polarization beam splitter, 4 - first λ / 2 wave plate, 5 - first acousto-optic modulator, 6 - first concave mirror, 7 - first sine signal source, 8 - second λ / 2 wave plate, 9 - first plane mirror, 10 - third polarization beam splitter, 11 - third λ / 2 wave plate, 12 - second acousto-optic modulator, 13 - second concave mirror, 14 - FM signal source, 15 - second sine signal source, 16 - fourth λ / 2 wave plate, 17 - second plane mirror, 18 - third plane mirror, 19 - fifth λ / 2 wave plate, 20 - fourth plane mirror, 21 - fourth polarization beam splitter, 22 - photodetector, 23 - filter amplifier, 24 - data acquisition system, 25 - electronic computer. SPECIFIC EMBODIMENTS

[0019] In order to better illustrate the purpose and advantages of the present invention, the following further describes the content of the invention with reference to the drawings and examples.

[0020] Embodiment 1:

[0021] As Figure 1 shown, a calibration and traceability device for a concave mirror reflection focusing type laser vibrometer disclosed in this embodiment includes a laser vibrometer 1, a first λ / 2 wave plate 4, a second λ / 2 wave plate 8, a third λ / 2 wave plate 11, a fourth λ / 2 wave plate 16, a fifth λ / 2 wave plate 19, a first polarization beam splitter 2, a second polarization beam splitter 3, a third polarization beam splitter 10, a fourth polarization beam splitter 21, a first concave mirror 6, a second concave mirror 13, a first plane mirror 9, a second plane mirror 17, a third plane mirror 18, a fourth plane mirror 20, a first acousto-optic modulator 5, a second acousto-optic modulator 12, an FM signal source 14, a first sine signal source 7, a second sine signal source 15, a photodetector 22, a filter amplifier 23, a data acquisition system 24, an electronic computer 25, etc.

[0022] The working method of a calibration and traceability device for a concave mirror reflection focusing type laser vibrometer disclosed in this embodiment is as follows:

[0023] The laser generated by the laser vibrometer 1 passes through the first polarization beam splitter 2, the second polarization beam splitter 3, and the first λ / 2 wave plate 4 in sequence, and reaches the first acousto-optic modulator 5. The first sine signal source 7 generates the required sine waveform modulation signal to control the first acousto-optic modulator 5, shift the frequency of the laser signal coming from the direction of the first λ / 2 wave plate 4, and generate the -1st order diffracted light, which is then reflected and focused by the first concave mirror 6, returns to the first acousto-optic modulator 5 to continue frequency shifting, then passes through the first λ / 2 wave plate 4, is reflected by the second polarization beam splitter 3, passes through the fourth λ / 2 wave plate 16, and is divided into two paths after passing through the third polarization beam splitter 10.

[0024] One path is the reflected light, which passes through the third λ / 2 wave plate 11 after being reflected by the third polarization beam splitter 10, reaches the second acousto-optic modulator 12. The second sine signal source 15 generates the required sine waveform modulation signal to frequency modulate the FM signal source 14 to generate the modulated FM signal. By controlling the second acousto-optic modulator 12, the laser coming from the third λ / 2 wave plate 11 is frequency shifted and modulated to generate the +1st order diffracted laser, which is reflected and focused by the second concave mirror 13, returns to the second acousto-optic modulator 12 to be frequency shifted and modulated again, passes through the third λ / 2 wave plate 11 and the third polarization beam splitter 10 in sequence, is reflected by the plane mirror 9, passes through the second λ / 2 wave plate 8, and reaches the first polarization beam splitter 2 and is divided into two beams of light.

[0025] One beam is the reflected light, which returns to the calibrated laser vibrometer 1 after being reflected by the first polarization beam splitter 2 for measurement and processing, completing the simulation process of vibrating the laser vibrometer 1 with the sine waveform generated by the second sine signal source 15.

[0026] The other beam is the transmitted light, which passes through the first polarization beam splitter 2, is reflected by the fourth plane mirror 20, passes through the fourth polarization beam splitter 21, and is combined and beat with the laser coming from the direction of the fifth λ / 2 wave plate 19.

[0027] Another path is the transmitted light. After passing through the third polarization beam splitter 10 and being reflected, it successively passes through the reflections of the second plane mirror 17 and the third plane mirror 18, passes through the fifth λ / 2 wave plate 19, reaches the fourth polarization beam splitter 21. After being reflected by the fourth polarization beam splitter 21, it is combined with the laser coming from the direction of the fourth plane mirror 20 and beat, reaches the photodetector 22, is received by the photodetector 22 and converted into a radio frequency FM electrical signal. This electrical signal is amplified by the filter amplifier 23, reaches the data acquisition system 24 for acquisition and storage to obtain the signal waveform, is transmitted to the electronic computer 25, and the waveform demodulation process is carried out to obtain the demodulation result of the sine waveform for modulation output by the second sine signal source 15. Thus, the quantity traceability of the sine waveform modulation signal to the higher-level parameters through the data acquisition system is realized, that is, the traceability of the concave mirror reflection focusing type laser vibration measuring instrument calibration device is realized.

[0028] 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 modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A calibration traceability device for a concave mirror reflection focusing type laser vibrometer, characterized in that: it includes a laser vibrometer (1), a first λ / 2 wave plate (4), a second λ / 2 wave plate (8), a third λ / 2 wave plate (11), a fourth λ / 2 wave plate (16), a fifth λ / 2 wave plate (19), a first polarization beam splitter (2), a second polarization beam splitter (3), a third polarization beam splitter (10), a fourth polarization beam splitter (21), a first concave mirror (6), a second concave mirror (13), a first plane mirror (9), a second plane mirror (17), a third plane mirror (18), a fourth plane mirror (20), a first acousto-optic modulator (5), a second acousto-optic modulator (12), an FM signal source (14), a first sine signal source (7), a second sine signal source (15), a photodetector (22), a filter amplifier (23), a data acquisition system (24) and an electronic computer (25); The laser generated by the laser vibrometer (1) passes through the first polarization beam splitter (2), the second polarization beam splitter (3), and the first λ / 2 wave plate (4) in sequence and reaches the first acousto-optic modulator (5). The first sine signal source (7) generates the required sine waveform modulation signal to control the first acousto-optic modulator (5) to shift the frequency of the laser signal coming from the direction of the first λ / 2 wave plate (4) and generate the -1st order diffracted light, which is then reflected and focused by the first concave mirror (6), returns to the first acousto-optic modulator (5) to continue frequency shifting, then passes through the first λ / 2 wave plate (4), is reflected by the second polarization beam splitter (3), passes through the fourth λ / 2 wave plate (16), and is divided into two paths after passing through the third polarization beam splitter (10); One path is the reflected light, which passes through the third λ / 2 wave plate (11) after being reflected by the third polarization beam splitter (10) and reaches the second acousto-optic modulator (12). The second sine signal source (15) generates the required sine waveform modulation signal to frequency modulate the FM signal source (14) to generate the modulated FM signal. By controlling the second acousto-optic modulator (12), the laser coming from the third λ / 2 wave plate (11) is frequency shifted and modulated to generate the +1st order diffracted laser, which is reflected and focused by the second concave mirror (13), returns to the second acousto-optic modulator (12) to be frequency shifted and modulated again, passes through the third λ / 2 wave plate (11) and the third polarization beam splitter (10) in sequence, is reflected by the plane mirror 9, passes through the second λ / 2 wave plate (8), and reaches the first polarization beam splitter (2) and is divided into two beams of light: One beam is the reflected light, which returns to the laser vibrometer (1) to be calibrated after being reflected by the first polarization beam splitter (2) for measurement and processing, completing the simulation process of vibrating the laser vibrometer (1) with the sine waveform generated by the second sine signal source (15); The other beam is the transmitted light, which after passing through the first polarization beam splitter (2), is reflected by the fourth plane mirror (20), passes through the fourth polarization beam splitter (21), and is combined and beat with the laser coming from the direction of the fifth λ / 2 wave plate (19); The other path is the transmitted light. After passing through the third polarization beam splitter (10) and being reflected, it successively passes through the reflections of the second plane mirror (17) and the third plane mirror (18), passes through the fifth λ / 2 wave plate (19), reaches the fourth polarization beam splitter (21). After being reflected by the fourth polarization beam splitter (21), it is combined with and beat with the laser coming from the direction of the fourth plane mirror (20), reaches the photodetector (22), is received by the photodetector (22) and converted into an RF FM electrical signal. This electrical signal is amplified by the filter amplifier (23), reaches the data acquisition system (24) for acquisition and storage to obtain the signal waveform, and is transmitted to the electronic computer (25) for waveform demodulation processing to obtain the demodulation result of the sine waveform for modulation output by the second sine signal source (15). Thus, the quantity value of the sine waveform modulation signal is traced back to the superior parameter through the data acquisition system, that is, the traceability of the concave mirror reflection focusing type laser vibrometer calibration device is realized.

2. A concave mirror reflection focusing type laser vibrometer calibration and traceability device according to claim 1, characterized in that: The laser frequency control signal waveform of the optical frequency modulator is obtained. By means of high-speed data acquisition and quantization technology, a signal waveform sequence is obtained, and the instantaneous frequency of the laser frequency control signal waveform is accurately demodulated in a digital manner, and then the vibration velocity waveform and vibration acceleration waveform as standards are obtained, so as to realize the dynamic measurement and quantity value traceability of the laser vibrometer itself.

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