An ultrahigh frequency vibration measuring device

Abstract

An ultra-high frequency vibration measurement device relates to the field of laser coherent detection technology, solving the problems of easy damage to the surface of micro-nano devices and low measurement frequency. The device includes a master-slave laser, a first fiber coupler for coupling the laser emitted by the master laser into the fiber and splitting it into a local oscillator beam and a signal beam. The signal beam and the laser emitted by the slave laser serve as inputs to an optical phase-locked loop (PLL) system. The optical PLL system, a first fiber collimator, a polarizing prism, a transceiver lens, and a vibrating target are sequentially arranged. The echo signal from the vibrating target and the local oscillator beam are transmitted together via a second fiber coupler to a balanced photodetector. The balanced photodetector mixes the echo signal and the local oscillator beam to form a photocurrent signal. A digital signal processing system calculates the target vibration information based on the photocurrent signal and a phase de-phase algorithm. This invention can generate ultra-high frequency dynamic carrier signals from MHz to GHz, and can also measure the vibration characteristics of the target in real time, with a measurement frequency reaching GHz.

Description

Technical Field

[0001] This invention relates to the field of laser coherent detection technology, specifically to an ultra-high frequency vibration measurement device. Background Technology

[0002] Ultra-high frequency (UHF) micro- and nano-devices based on micro- and nano-electro-mechanical systems (MEMS) technology, such as micro- and nano-resonators, RF-MEMS, and surface acoustic wave (SAW) devices, are widely used in life sciences, mobile communications, radio frequency identification (RFID), and automotive electronics. Non-contact measurement of target vibration characteristics typically employs high-precision, interference-resistant, and high signal-to-noise ratio laser Doppler vibration measurement methods. However, in traditional laser Doppler vibration measurement devices, when the driving frequency of the acousto-optic modulation device reaches GHz, the acousto-optic diffraction efficiency decreases, making it difficult to apply in the field of UHF vibration measurement. Furthermore, the range of carrier frequencies limits the measurement of vibration characteristics of UHF micro- and nano-devices.

[0003] Currently, methods for measuring ultra-high frequency micro-vibration targets include atomic force microscopy, optical probes, and stroboscopic white light interferometers. Atomic force microscopy and optical probes require the probe tip to be in continuous contact with the device surface during scanning, which can easily damage the surface of micro- and nano-devices. Furthermore, they can only measure the static morphology of micro- and nano-devices and cannot measure the vibration characteristics of the target in real time. Stroboscopic white light interferometers require the measurement system to be strictly mechanically stable to eliminate the cumulative errors caused by time drift and environmental fluctuations. However, due to the limitations of supercontinuum spectral light sources, the measurement frequency is difficult to reach GHz.

[0004] Therefore, there is an urgent need for a vibration measurement device that is not likely to cause damage to the surface of micro-nano devices and can measure frequencies up to GHz. Summary of the Invention

[0005] In view of the above problems, the present invention provides an ultra-high frequency vibration measurement device.

[0006] The technical solution adopted by this invention to solve the technical problem is as follows:

[0007] An ultra-high frequency vibration measurement device includes a master laser, a slave laser, a first fiber coupler, an optical phase-locked loop system, a first fiber collimator, a polarizing prism, a second fiber collimator, a transceiver lens, a second fiber coupler, a balanced photodetector, and a digital signal processing system connected to the balanced photodetector. The first fiber coupler couples the laser emitted by the master laser into the fiber and splits it into a local oscillator beam and a signal beam. The signal beam and the laser emitted by the slave laser serve as inputs to the optical phase-locked loop system. The carrier signal output from the optical phase-locked loop system sequentially passes through the first fiber collimator for collimation, the polarizing prism for transmission, and the transceiver lens for transmission before illuminating the vibrating target to obtain an echo signal. The echo signal sequentially passes through the transceiver lens for transmission, the polarizing prism for reflection, and the second fiber collimator for coupling, before being transmitted together with the local oscillator beam via the second fiber coupler to the balanced photodetector. The balanced photodetector mixes the echo signal and the local oscillator beam to form a photocurrent signal. The digital signal processing system calculates the target vibration information based on the photocurrent signal and a phase de-phase algorithm.

[0008] The beneficial effects of this invention are:

[0009] This invention provides an ultra-high frequency vibration measurement device that combines optical phase-locked loop and laser Doppler vibration measurement technology. It can not only generate ultra-high frequency dynamic carrier signals from MHz to GHz, but also measure the vibration characteristics of the target in real time. The measurement frequency can reach GHz, and it can ensure that the surface of micro and nano devices is not damaged. Attached Figure Description

[0010] Figure 1 This is a schematic diagram of the structure of an ultra-high frequency vibration measurement device according to the present invention.

[0011] Figure 2 This is a schematic diagram of the optical phase-locked loop structure of an ultra-high frequency vibration measurement device according to the present invention.

[0012] In the diagram: 1. Master laser, 2. Slave laser, 3. First fiber coupler, 4. Optical phase-locked loop system, 5. First fiber collimator, 6. Half-wave plate, 7. Polarizing prism, 8. Second fiber collimator, 9. Quarter-wave plate, 10. Transceiver lens, 11. Vibrating target, 12. Second fiber coupler, 13. Balanced photodetector, 14. Digital signal processing system, 15. Photodetector, 16. Loop filter, 17. Optical phase detector, 18. Optical voltage-controlled oscillator. Detailed Implementation

[0013] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments.

[0014] An ultra-high frequency vibration measurement device, such as Figure 1The system includes a master laser 1, a slave laser 2, a first fiber coupler 3, an optical phase-locked loop system 4, a first fiber collimator 5, a polarizing prism 7, a second fiber collimator 8, a transceiver lens 10, a second fiber coupler 12, a balanced photodetector 13, and a digital signal processing system 14 connected to the balanced photodetector 13. The first fiber coupler 3 couples the laser emitted by the master laser 1 into the optical fiber and splits it into local oscillator light (hereinafter referred to as local oscillator light signal) and signal light. The signal light and the laser emitted by the slave laser 2 together serve as the input to the optical phase-locked loop system 4, and the carrier signal serves as the input to the optical phase-locked loop system. The output of 4, the carrier signal can sequentially pass through the first fiber collimator 5 for collimation, the polarizing prism 7 for transmission, and the transceiver lens 10 for transmission before illuminating the vibrating target 11 to obtain an echo signal. The echo signal can sequentially pass through the transceiver lens 10 for transmission, the polarizing prism 7 for reflection, and the second fiber collimator 8 for coupling, and then, together with the local oscillator light, is transmitted through the second fiber coupler 12 to the balanced photodetector 13. The balanced photodetector is used to mix the echo signal and the local oscillator light to form a photocurrent signal. The digital signal processing system 14 is used to calculate the target vibration information based on the photocurrent signal and the phase dephase algorithm.

[0015] A specific ultra-high frequency vibration measurement device also includes a half-wave plate 6 and a quarter-wave plate 9.

[0016] The master laser 1 is positioned corresponding to the first fiber coupler 3. The first fiber coupler 3 is connected to the optical phase-locked loop system 4 and the second fiber coupler 12 via optical fibers. The slave laser 2 is positioned corresponding to the optical phase-locked loop system 4. The optical phase-locked loop system 4 is connected to the slave laser 2 to control the output signal frequency of the slave laser 2. The optical phase-locked loop system 4 is connected to the first fiber collimator 5 via optical fibers. The first fiber collimator 5, half-wave plate 6, polarizing prism 7, quarter-wave plate 9, transceiver lens 10, and vibrating target 11 are arranged sequentially. The transceiver lens 10 is used to transmit the beam. The second fiber collimator 8 is positioned corresponding to the polarizing prism 7. The second fiber collimator 8 is connected to the second fiber coupler 12 via optical fibers. The second fiber coupler 12 is a 2×2 fiber coupler. The input end of the second fiber coupler 12 is set to correspond to the first fiber coupler 3 and the second fiber collimator 8. The output end of the second fiber coupler 12 is set to correspond to the balanced photodetector 13. It is used to send the local oscillator light signal of the main laser 1 and the light signal (echo signal) reflected by the vibrating target 11 to the balanced photodetector 13.

[0017] The laser emitted from the main laser 1 is coupled by the first fiber coupler 3 and split into two beams. One beam is transmitted as a signal beam to the optical phase-locked loop system 4, and the other beam is transmitted as a local oscillator beam to the second fiber coupler 12. The laser emitted from laser 2 is also transmitted to the optical phase-locked loop system 4, where the laser beam from the main laser and the laser beam from the laser 2 generates an ultra-high frequency carrier signal. When the loop is operating stably, the frequency of the laser beam emitted from laser 2 always tracks the frequency of the main laser 1 under the action of the optical phase-locked loop system, and the frequency difference between the two remains dynamically stable. The laser beam emitted from laser 2, after being controlled by optical phase-locked loop system 4, is output to the first fiber collimator 5. After being collimated by the first fiber collimator 5, it is incident on half-wave plate 6, polarized by half-wave plate 6, transmitted through polarizing prism 7, polarized by quarter-wave plate 9, and enters transceiver lens 10. It then illuminates the vibrating target 11 and is reflected to obtain an echo signal. The echo signal carries the target vibration information. The echo signal is transmitted by transceiver lens 10 to quarter-wave plate 9 for polarization maintenance, reflected by polarizing prism 7 to the second fiber collimator 8, collimated by the second fiber collimator 8, and then to the second fiber coupler 12. The second fiber coupler 12 transmits the local oscillator signal emitted by the first fiber coupler 3 to the second fiber coupler 12. The echo signals collimated by the light and the second fiber collimator 8 are both sent to the balanced photodetector 13. Mixing occurs on the photosensitive surface of the balanced photodetector, forming a photocurrent signal. This photocurrent signal then enters the digital signal processing system 14. The digital signal processing system 14 receives the photocurrent signal and calculates the target vibration information according to the phase decoupling algorithm. Specifically, in the digital signal processing system, the photocurrent signal carrying the target vibration information is used to generate a pair of orthogonal baseband signals through orthogonal demodulation technology. Then, the arctangent demodulation algorithm is used to perform arctangent operations on the two baseband signals. After phase unwrapping and bandpass filtering, real-time measurement of the ultra-high frequency vibration signal can be achieved to obtain the target vibration information. Using the arctangent demodulation algorithm to accurately demodulate the echo light carrying the target vibration information enables high-precision extraction of the ultra-high frequency target vibration characteristics.

[0018] The optical phase-locked loop system 4 can achieve dynamic synchronization between the output signal frequency of the slave laser 2 and the output signal frequency of the master laser 1. The optical phase-locked loop system 4 can adjust the output signal frequency of the slave laser 2. The working principle of the optical phase-locked loop system 4 is shown in the figure below. Figure 2 The master laser 1 and slave laser 2 are mixed on the photosensitive surface of the photodetector 15 to obtain a mixed signal. The optical phase detector 17 compares the phase of the mixed signal with the reference signal generated by the optical voltage-controlled oscillator 18 and outputs a voltage signal v corresponding to the phase difference between the two. d Loop filter 16 pairs of voltage signals v d A control signal i is generated by performing filtering, integration, and other processing. c control signal i cThe output frequency of laser 2 is adjusted, and the optical signal output from laser 2 is sent to optical phase detector 17 for phase comparison, forming a closed loop. When the loop is operating stably, the mixed signal generated by the main laser 1 and the slave laser 2 always tracks the frequency of the reference signal generated by the optical voltage-controlled oscillator 18. Theoretically, their frequencies are consistent, and the output voltage of optical phase detector 17 reaches its minimum and remains constant. When the reference signal frequency changes, the mixed signal will automatically track the reference signal frequency within a certain range under the action of the phase-locked loop, thereby achieving dynamic synchronization between slave laser 2 and main laser 1. Thus, this invention utilizes optical phase-locked loop technology with two independent lasers to generate an ultra-high frequency carrier signal.

[0019] Both the master laser 1 and the slave laser 2 are distributed feedback fiber lasers with mode-hopping-free performance. The master laser 1 emits a laser beam, which is split into two in a power ratio of 1:9 after passing through the first fiber coupler 3. The lower-power laser beam is used as the local oscillator signal, and the higher-power part passes through the second fiber coupler 12 and enters the optical phase detector 17 together with the laser beam emitted by the slave laser 2.

[0020] This invention proposes an ultra-high frequency vibration measurement device that combines optical phase-locked loop 4 and laser Doppler vibration measurement technology. It generates an ultra-high frequency dynamic carrier signal to replace the traditional acousto-optic modulation device with low diffraction efficiency. It can measure the vibration characteristics of the target in real time, and the measurement frequency can reach GHz, while ensuring that the surface of micro and nano devices is not damaged.

[0021] This invention solves the problem of generating ultra-high frequency carrier signals by using feedback control of electrical signals to achieve phase locking between two independent lasers and maintain the dynamic stability of their frequency difference. The ultra-high frequency dynamic carrier signal generation method based on an optical phase-locked loop can not only generate ultra-high frequency dynamic carrier signals from MHz to GHz, but also achieve precise control of the carrier signal frequency stability at the optical end using high-precision negative feedback control of the optical phase-locked loop's electrical signals. This enables high-precision real-time vibration measurement within the ultra-high frequency range of MHz to GHz.

[0022] The use of waveplates combined with polarizing prisms avoids crosstalk between the carrier signal and the echo signal emitted by the optical phase-locked loop system 4, thereby reducing random phase jitter of the photocurrent signal. This method not only ensures the isolation of the system, but also ensures that the echo signal and the local oscillator signal have the same polarization direction. At the same time, the balanced detection method can suppress relative intensity noise.

[0023] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. An ultrahigh frequency vibration measuring device, characterized by comprising: The application relates to a laser Doppler vibration measurement system, which comprises a master laser (1), a slave laser (2), a first fiber coupler (3), an optical phase-locked loop system (4), a first fiber collimator (5), a polarization prism (7), a second fiber collimator (8), a transceiver lens (10), a second fiber coupler (12), a balanced photodetector (13) and a digital signal processing system (14) connected with the balanced photodetector (13), the first fiber coupler (3) is used for coupling laser emitted by the master laser (1) into an optical fiber and dividing the laser into local light and signal light, the signal light and laser emitted by the slave laser (2) are used as inputs of the optical phase-locked loop system (4) together, a carrier signal output by the optical phase-locked loop system (4) can be sequentially collimated by the first fiber collimator (5), transmitted by the transceiver lens (10) after being transmitted by the polarization prism (7), and irradiated on a vibrating target (11) to obtain a return signal, the return signal can be sequentially transmitted by the transceiver lens (10), reflected by the polarization prism (7) and coupled by the second fiber collimator (8), and then transmitted to the balanced photodetector (13) by the second fiber coupler (12) together with the local light; the balanced photodetector is used for mixing the return signal and the local light to form a photocurrent signal; and the digital signal processing system (14) is used for calculating target vibration information according to the photocurrent signal and a phase demodulation algorithm.

2. A device for measuring vibrations at ultra-high frequencies as claimed in claim 1, characterized in that The application further comprises a half-wave plate (6) and a 1 / 4 wave plate (9), and the first fiber collimator (5), the half-wave plate (6), the polarization prism (7), the second fiber collimator (8), the 1 / 4 wave plate (9) and the transceiver lens (10) are sequentially arranged.

3. A device for measuring vibrations at ultra-high frequencies as claimed in claim 1, wherein, The polarization direction of the return signal is the same as that of the local light.

4. A device for measuring vibrations at ultra-high frequencies as claimed in claim 1, wherein, The master laser (1) and the slave laser (2) are both distributed feedback fiber lasers.

5. A device for measuring vibrations at ultra-high frequencies as claimed in claim 1, wherein, The laser emitted by the master laser (1) is divided into the local light and the signal light according to a power ratio of 1:9 after passing through the first fiber coupler (3).

6. A device for measuring vibrations at ultra-high frequencies as claimed in claim 1, wherein, The digital signal processing system (14) obtains a pair of quadrature baseband signals by processing the photocurrent signal through a quadrature demodulation method, performs arctangent operation on the pair of quadrature baseband signals by using an arctangent demodulation algorithm, and obtains target vibration information after phase unwrapping and band-pass filtering.

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