ZYNQ-based phase modulation laser interference displacement measurement system and method

Abstract

The invention relates to a ZYNQ-based phase modulation laser interference displacement measurement system and method, and belongs to the field of phase modulation laser interference displacement measurement, the system comprises a laser acquisition system, a data processing system and an upper computer; the laser acquisition system comprises a laser, a measurement target, a beam splitter prism and a photoelectric detector; the data processing system comprises a ZYNQ chip, an ADC module, a DAC module and a network transmission module; laser emitted by the laser device is divided into two paths of light after passing through the beam splitter prism; by using the ZYNQ, the ADC acquisition module, the DAC output module and the PC upper computer, the data acquisition and processing cost is reduced, and measurement information can be fed back in real time; due to the fact that a phase generation demodulation algorithm based on Kalman filtering is used, the operation speed is high, and the measurement precision is high.

Description

Technical Field

[0001] The present invention relates to the technical field of laser interferometry displacement measurement, and in particular to a ZYNQ-based phase-modulated laser interferometry displacement measurement system and method. Background Art

[0002] With the continuous development of the chip manufacturing industry, achieving nanometer-precision displacement measurement over a large range is an urgent problem to be solved in order to improve the current chip manufacturing level. In the field of nano-measurement, laser interferometry technology stands out due to its advantages of high measurement accuracy, fast speed, and wide range. In laser interferometry technology, measurement technology represented by phase-modulated single-frequency laser interferometers has the advantages of simple structure and non-contact measurement and is widely used. Traditional laser interferometers cannot measure large-scale displacements while ensuring measurement accuracy, and the proposed methods have problems such as cumbersome implementation and high computational cost. Summary of the invention

[0003] A ZYNQ-based phase-modulated laser interferometry displacement measurement system, the system comprising:

[0004] Laser acquisition system, data processing system, PC host computer; the laser acquisition system is connected to the data processing system in communication, and the data processing system is connected to the PC host computer in communication; wherein:

[0005] The laser acquisition system includes a laser, a measurement target, an EOM, a beam splitter, and a photoelectric detector. The laser emitted by the laser is divided into two beams after passing through the beam splitter. One beam is transmitted light and enters the measurement target and is reflected. The other beam is reflected light and enters the reference corner cube prism and is reflected. The corner cube prism is installed on the EOM and is controlled by the EOM to perform sinusoidal motion. The two beams of light converge at the beam splitter prism to produce interference, which is detected by the photoelectric detector. The photoelectric detector is connected to the data processing system.

[0006] The data processing system includes ZYNQ, ADC module, DAC module and Gigabit network port module; the ADC module is connected to the photodetector and ZYNQ respectively; the AD module collects the laser interference signal transmitted by the photodetector, and outputs the waveform signal from the laser interference to ZYNQ, and the interference signal waveform is restored by ZYNQ through the phase generation carrier demodulation algorithm based on Kalman filtering; the DAC module is connected to EOM and ZYNQ, and generates and outputs a sinusoidal modulation signal to EOM through DDR3; the Gigabit network port module is connected to a PC host computer to display the laser interference signal and displacement data.

[0007] The PC host computer displays the laser interference waveform signal and the displacement waveform, and calculates the displacement information of the measurement target based on the laser interference waveform signal and the restored interference waveform signal. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 This is a schematic diagram of the structure of the ZYNQ phase-modulated laser interferometry displacement measurement system of the present invention;

[0009] Figure 2 This is a schematic diagram of the flow of the ZYNQ phase-modulated laser interferometry displacement measurement system of the present invention;

[0010] Figure 3 This is a flow chart for calculating laser interference signal parameters based on Kalman filter algorithm;

[0011] Figure 4 Schematic diagram of the laser interference signal waveform after modulation;

[0012] Figure 5 is a schematic diagram of the demodulated laser interference signal waveform;

[0013] Figure 6 This is the error diagram of micron-level step displacement measurement. DETAILED DESCRIPTION

[0014] The present invention is further described in detail below with reference to the accompanying drawings and embodiments.

[0015] In one embodiment, Figure 1As shown, a phase-modulated laser interferometric displacement measurement system based on ZYNQ is provided, including a laser acquisition system, a data processing system, and a display screen; the laser acquisition system is connected to the data processing system in communication, and the data processing system is connected to the PC host computer in communication; wherein: the laser acquisition system includes a laser 1, a beam splitter prism 2, a measurement target 3, an EOM4, and a photodetector 5; the laser emitted by the laser 1 is divided into two paths of light after passing through the beam splitter prism 2, one path is the transmitted light that enters the measurement target 3 and is reflected; the other path is the reflected light that enters the reference corner cube prism and is reflected, the corner cube prism is installed on the EOM4 and is controlled by the EOM4 to perform sinusoidal motion, the two beams of light converge at the beam splitter prism to generate interference, and are detected by the photodetector 5. The photodetector 5 is connected to the data processing system. The data processing system includes ZYNQ 6, AD module 7, DAC module 8, DDR module 9, and Gigabit network port module 10; the ADC module 7 and the DAC module 8 are connected to the photodetector 5 and ZYNQ6 respectively; the AD module 7 collects the laser interference signal transmitted by the photodetector 5, and outputs the waveform signal of the laser interference to ZYNQ 6, and the interference signal waveform is restored by the phase generation carrier demodulation algorithm based on Kalman filtering through ZYNQ 6; the PC host computer 11 is connected to the Gigabit network port module 10, displays the waveform signal of the laser interference and the displacement waveform, and calculates the displacement information of the measurement target based on the waveform signal of the laser interference and the restored interference waveform signal.

[0016] In one embodiment, the laser emitted by the laser is divided into two beams after passing through a beam splitter prism. One beam is transmitted light and enters the measurement target and is reflected; the other beam is reflected light and enters a reference corner cube prism and is reflected. The corner cube prism is mounted on the EOM and is controlled by the EOM to perform sinusoidal motion. The two beams of light converge at the beam splitter prism to produce interference, which is detected by a photodetector.

[0017] In one embodiment, the laser may be a helium-neon laser, wherein the laser is not only a light source but also a sensitive element, so that the entire ZYNQ-based phase-modulated laser interferometric displacement measurement system has a simple and compact structure and the optical path is easy to align.

[0018] In one embodiment, a BNC interface is provided on the photodetector; an SMA interface is provided on the AD module; and the photodetector transmits the interference signal from the SMA interface to the AD module via the BNC interface.

[0019] In one embodiment, ZYNQ includes a PS end and a PL end; the PS end drives and controls the ADC module connected to the PL end to collect the laser interference signal waveform, transmits it to the DDR of the PS end through AXI-DMA, and corrects the data in the DDR and restores the laser interference signal waveform.

[0020] In one embodiment, Figure 1 As shown, a phase-modulated laser interferometer displacement measurement system based on ZYNQ is provided, which also includes a DAC module; ZYNQ generates a phase-modulated carrier signal through DDR3, and transmits the signal through the DAC module and acts on the EOM.

[0021] In one embodiment, Figure 2 As shown, a phase-modulated laser interferometry displacement measurement method based on ZYNQ is provided, and the specific steps include:

[0022] Step 52, the laser emitted by the laser is divided into two beams after passing through the beam splitter prism. One beam is the transmitted light that enters the measurement target and is reflected; the other beam is the reflected light that enters the reference corner cube prism and is reflected. The corner cube prism is installed on the EOM and is controlled by the EOM to perform sinusoidal motion. The two beams of light converge at the beam splitter prism to produce interference, which is detected by the photoelectric detector.

[0023] Step 54, ZYNQ generates a phase modulated carrier signal through DDR3, and passes the DAC module to attach the signal and act on the EOM.

[0024] Step 56, the photodetector sends the laser interference signal to the AD module, and the AD module transmits the laser interference waveform signal to the DDR at the PS end of ZYNQ.

[0025] Step 58, ZYNQ performs signal processing and correction on the data in DDR to restore the laser interference signal waveform.

[0026] In step 60, ZYNQ transmits the laser interference waveform signal and the displacement waveform to a PC host computer for display, and calculates the displacement information of the measurement target based on the laser interference waveform signal and the restored interference waveform signal.

[0027] In this embodiment, during the measurement process, the laser is aimed at the measurement target, the reflected laser is returned to the laser cavity, a beam splitter is placed in the optical path, and the polarization direction of the laser beam is kept consistent with the main axis direction of the electro-optical crystal, the DAC output port is connected to the EOM, and the laser beam is sinusoidally phase modulated by the EOM. Finally, the laser beam interferes at the polarizer and the laser interference signal enters the photodetector. Then the photodetector is connected to the SMA interface of the AD module through the BNC interface, the PS end of ZYNQ drives and controls the AD module at the PL end to collect the laser interference signal, and transmits it to the DDR at the PS end through AXI-DMA, and corrects the data in the DDR, and finally transmits it to the PC host computer through the Gigabit network port, and calculates and displays the displacement information of the measurement target based on the waveform signal of the laser interference and the restored interference waveform signal.

[0028] Specifically, in one embodiment, the formula of the laser interference signal is: Where A is the DC quantity, which is proportional to the output optical power of the laser; B is the interference signal amplitude, C is the phase modulation amplitude, generally referred to as the modulation depth; ω0 is the angular frequency of the high-frequency carrier signal. is the signal to be tested; External environmental noise interference.

[0029] The output signal is expanded according to the Bessel function, mixed with the baseband and double frequency signals, and passed through a low-pass filter to obtain two orthogonal signals containing phase information:

[0030]

[0031] Where J1(C) and J2(C) represent the first-order and second-order Bessel functions respectively, and C is the phase modulation depth.

[0032] Simplify the above signal to: and

[0033] Then, the above signal is transmitted to ZYNQ's DDR for signal processing and correction. The simplified laser interference signal conforms to the elliptic equation and can be written as AX(t) 2 +CY(t) 2 +2DX(t)+2EY(t)=1

[0034] By calculating the above formula, the ellipse parameters are obtained after ellipse fitting of the orthogonal signal, the amplitude and offset of the orthogonal signal are obtained, and correction is performed. The correction formula is as follows:

[0035]

[0036] Among them, the Kalman filter algorithm is used to perform high-precision iterative estimation calculation of the ellipse parameters. The specific calculation process of the ellipse parameters is as follows: Figure 3 shown.

[0037] Finally, the accurate phase change is obtained by the inverse tangent algorithm: From this, the displacement information of the measurement target can be calculated:

[0038] In summary, the present invention provides a phase-modulated laser interferometer displacement measurement system based on ZYNQ. The system can realize high-precision displacement measurement for laser interferometer, display displacement data in real time during the measurement process, and implement the algorithm with ZYNQ, avoiding the need to realize high-precision displacement measurement only in offline mode, reducing costs, increasing flexibility, and improving work efficiency, bringing new application prospects for laser interferometer measurement technology.

[0039] The above is a detailed introduction to a ZYNQ-based phase-modulated laser interferometer displacement measurement system provided by the present invention. The above examples are provided only to help understand the method of the present invention, and are not intended to limit the scope of the present invention. The scope of the present invention is defined by the appended claims, and various equivalent substitutions and modifications made without departing from the spirit and principles of the present invention should be included in the scope of the present invention.

Claims

1. A phase-modulated laser interferometry displacement measurement system based on ZYNQ, characterized in that: The system includes: a laser acquisition system, a data processing system, and a PC host computer; the laser acquisition system is connected to the data processing system for communication, and the data processing system is connected to the PC host computer for communication; wherein: The laser acquisition system includes a laser, a measurement target, an EOM, a beam splitter prism, and a photoelectric detector; the laser emitted by the laser is divided into two beams after passing through the beam splitter prism, one beam is transmitted light and enters the measurement target and is reflected; the other beam is reflected light and enters the reference corner cube prism and is reflected. The corner cube prism is installed on the EOM and is controlled by the EOM to perform sinusoidal motion. The two beams of light converge at the beam splitter prism to generate interference, which is detected by the photoelectric detector; the photoelectric detector is connected to the data processing system; The data processing system includes ZYNQ, ADC module, DAC module, and Gigabit Ethernet port module; the ADC module is connected to the photodetector and ZYNQ respectively; the AD module collects the laser interference signal transmitted by the photodetector, and outputs the waveform signal from the laser interference to ZYNQ, and the phase generation carrier demodulation algorithm based on Kalman filtering is implemented by ZYNQ to restore the interference signal waveform; the DAC module is connected to EOM and ZYNQ, and generates and outputs a sinusoidal modulation signal to EOM through DDR3; the Gigabit Ethernet port module is connected to a PC host computer to display the laser interference signal and displacement data; The PC host computer displays the laser interference waveform signal and the displacement waveform, and calculates the displacement information of the measurement target based on the laser interference waveform signal and the restored interference waveform signal.

2. The ZYNQ-based phase-modulated laser interferometry displacement measurement system according to claim 1, characterized in that: The laser is a helium-neon laser.

3. The ZYNQ-based phase-modulated laser interferometry displacement measurement system according to claim 1, characterized in that: The photoelectric detector is provided with a BNC interface; the AD module is provided with an SMA interface; the photoelectric detector transmits the self-mixing interference signal from the SMA interface to the AD module through the BNC interface.

4. The ZYNQ-based phase-modulated laser interferometry displacement measurement system according to claim 1, characterized in that: ZYNQ includes PS and PL ends. The PS end drives and controls the ADC module connected to the PL end to collect the laser interference signal waveform, transmits it to the DDR of the PS end through AXI-DMA, and corrects the data in the DDR and restores the laser interference signal waveform.

5. The ZYNQ-based phase-modulated laser interferometry displacement measurement system according to claim 1, characterized in that: ZYNQ generates a phase modulated carrier signal through DDR3, and passes the auxiliary signal through the DAC module and acts on the EOM.

6. A phase-modulated laser interferometry displacement measurement method based on ZYNQ, characterized in that: The method comprises: The laser emitted by the laser is divided into two beams after passing through the beam splitter prism. One beam is the transmitted light that enters the measurement target and is reflected; the other beam is the reflected light that enters the reference corner cube prism and is reflected. The corner cube prism is installed on the EOM and is controlled by the EOM to make sinusoidal motion. The two beams of light converge at the beam splitter prism to produce interference, which is detected by the photodetector. The AD module collects the laser interference signal transmitted by the photodetector, and outputs the waveform signal from the laser interference to ZYNQ, and restores the interference signal waveform by implementing the phase generation carrier demodulation algorithm based on Kalman filtering through ZYNQ; the DAC module generates and outputs a sinusoidal modulation signal to EOM through DDR3; The PC host computer displays the laser interference waveform signal and the displacement waveform, and calculates the displacement information of the measurement target based on the laser interference waveform signal and the restored interference waveform signal.

7. The ZYNQ-based phase-modulated laser interferometry displacement measurement method according to claim 6, characterized in that: The formula of the laser interference signal is: Where A is the DC quantity, which is proportional to the output optical power of the laser; B is the interference signal amplitude, C is the phase modulation amplitude, generally referred to as the modulation depth; ω0 is the angular frequency of the high-frequency carrier signal; is the signal to be tested; External environmental noise interference.

8. The ZYNQ-based phase-modulated laser interferometry displacement measurement method according to claim 6, characterized in that: The laser interference signal is transmitted to ZYNQ's DDR for signal processing and correction. The simplified laser interference signal conforms to the elliptic equation and can be written as AX(t) 2 +CY(t) 2 +2DX(t)+2EY(t)=1.

9. The ZYNQ-based phase-modulated laser interferometry displacement measurement method according to claim 6, characterized in that: The Kalman filter algorithm is used to iteratively estimate and calculate the ellipse parameters with high precision. The orthogonal signal is fitted with an ellipse to obtain the ellipse parameters, and the amplitude and offset of the orthogonal signal are obtained and corrected. The correction formula is as follows:

10. The ZYNQ-based phase-modulated laser interferometry displacement measurement method according to claim 6, characterized in that: Finally, the accurate phase change is obtained by the inverse tangent algorithm: From this, the displacement information of the measurement target can be calculated:

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