System for measuring absolute distance and relative displacement fusion of space optical assemblies

Abstract

The application provides a kind of absolute distance and relative displacement fusion measurement system of space optical assembly, including frequency difference lock switching module, heterodyne light splitting frequency shift module, interference measurement module and signal processing module;Frequency difference lock switching module alternately outputs master laser and slave laser with fixed frequency difference;Heterodyne light splitting frequency shift module splits and shifts frequency to master laser or slave laser, and outputs master measurement light and master reference light with fixed heterodyne frequency, or slave measurement light and slave reference light;Interference measurement module carries out heterodyne interference measurement to measurement target using master measurement light and master reference light or slave measurement light and slave reference light, and outputs master measurement interference light beat signal and master reference interference light beat signal, or slave measurement interference light beat signal and slave reference interference light beat signal;Signal processing module calculates the absolute distance information and relative distance information of measurement target.The application can simultaneously carry out absolute and relative distance measurement by alternately outputting laser with different working frequencies.

Description

Technical Field

[0001] This invention belongs to the field of spacecraft precision measurement, and specifically relates to a measurement system that integrates the absolute distance and relative displacement of space optical components. Background Technology

[0002] With the increasing demands of high-resolution remote sensing missions, the ability of satellite cameras to monitor the positions of their main components throughout the mission cycle is becoming increasingly urgent, leading to the need for precise measurement of the distances between these main components. This requirement has two characteristics: 1. Both absolute and relative measurements must be considered: Measurement requirements include absolute distance measurements within the centimeter range and relative distance measurements over long periods; 2. High measurement accuracy: In typical large-aperture systems, the measurement accuracy of absolute distance changes in the main optical components needs to be better than the micrometer level, and the relative monitoring accuracy needs to reach the nanometer level.

[0003] In existing high-precision space optical measurements, dual-frequency laser heterodyne interferometry has stable accuracy capabilities. However, heterodyne interferometry is a relative measurement, and the system is sensitive to the relative displacement change relative to the initial measurement point. For applications requiring absolute distance accuracy, ground systems can use methods such as multi-heterodyne cascade method to extend the measurement range, frequency-modulated continuous wave distance measurement method, and femtosecond frequency comb absolute ranging method developed in recent years. However, these methods all face pressures on measurement accuracy, system complexity, and reliability for space measurements. Summary of the Invention

[0004] The technical problem solved by this invention is to overcome the shortcomings of the prior art and provide a measurement system that fuses the absolute distance and relative displacement of a space optical component, which has high precision and high reliability.

[0005] The technical solution of this invention is:

[0006] A measurement system for fusing absolute distance and relative displacement of a space optical component includes a frequency difference locking switching module, a heterodyne beam splitting frequency shifting module, an interferometric measurement module, and a signal processing module;

[0007] Frequency difference locking switching module: alternately outputs master laser and slave laser with a fixed frequency difference;

[0008] Heterodyne beam splitting and frequency shifting module: splits and shifts the frequency of the master laser or slave laser, and outputs master measurement light and master reference light, or slave measurement light and slave reference light with fixed heterodyne frequencies;

[0009] Interferometric measurement module: Performs heterodyne interferometric measurement on the target using the master measurement light and master reference light, or the slave measurement light and slave reference light, and outputs the master measurement interferometric beam signal and master reference interferometric beam signal, or the slave measurement interferometric beam signal and slave reference interferometric beam signal;

[0010] Signal processing module: Calculates the relative distance information of the target using the main measurement interferometric optical beat signal and the main reference interferometric optical beat signal, or from the measurement interferometric optical beat signal and the reference interferometric optical beat signal; calculates the absolute distance information of the target using the main measurement interferometric optical beat signal, the main reference interferometric optical beat signal, the measurement interferometric optical beat signal, and the reference interferometric optical beat signal.

[0011] Preferably, the frequency difference locking module includes a master laser, a first unpolarized beam splitter cube, a first switching AOM, a slave laser, a second unpolarized beam splitter cube, a second switching AOM, an unpolarized beam combiner cube, a first photodetector, and a phase-locked loop;

[0012] The laser emitted by the master laser is reflected by the first non-polarized beam splitter cube to form laser A, and transmitted to form the master laser. The laser emitted by the slave laser is transmitted by the second non-polarized beam splitter cube to form laser B, and reflected to form the slave laser. Laser A and laser B are combined by a non-polarized beam combiner cube to form laser C, which is incident on the first photodetector to form a detection signal. The phase-locked loop adjusts the laser frequency output by the slave laser according to the detection signal, so that the laser emitted by the slave laser and the master laser have a fixed frequency difference. The master laser is controlled by a first switching AOM, and the slave laser is controlled by a second switching AOM. By controlling the first and second switching AOMs, the master laser and the slave laser are output alternately.

[0013] Preferably, the heterodyne beam shifting module includes a fourth unpolarized beam splitter cube, a first frequency-shifting AOM, and a second frequency-shifting AOM. The main laser, after passing through the fourth unpolarized beam splitter cube, has its reflected and transmitted light shifted by the first and second frequency-shifting AOMs respectively, and is then output as the main measurement light and the main reference light. The secondary laser, after passing through the fourth unpolarized beam splitter cube, has its transmitted and reflected light shifted by the first and second frequency-shifting AOMs respectively, and is then output as the secondary measurement light and the secondary reference light.

[0014] Preferably, the interferometric measurement module includes one or more sets of interferometric measurement optical paths. Each set of interferometric measurement optical paths includes a measurement optical path and a reference optical path. The measurement optical path includes a first half-wave plate, a first polarization beam splitter cube, a fourth unpolarized cube, a quarter-wave plate, a reflector, and a measurement target mirror. The reference optical path includes a second half-wave plate, a second polarization beam splitter cube, a third half-wave plate, a fifth unpolarized cube, a sixth unpolarized cube, a second photodetector, and a third photodetector.

[0015] The main or secondary measurement light is adjusted to P-polarized light through a half-wave plate, and then its polarization state is stabilized by the first polarization beam splitter cube. It is then split into two parallel laser beams with a certain distance through the fourth non-polarization beam splitter cube. The two laser beams are transmitted through the second polarization beam splitter cube and then adjusted to circular polarization by a quarter-wave plate. One of the beams is incident on the measurement target and reflected back. It is then adjusted to S-polarized light by a quarter-wave plate and reflected by the first polarization beam splitter cube to form laser D1. The other beam is incident on the mirror and reflected back. It is then adjusted to S-polarized light by a quarter-wave plate and reflected by the first polarization beam splitter cube to form laser D2. Lasers D1 and D2 are incident on the sixth non-polarization beam splitter cube.

[0016] The main reference light or the secondary reference light is adjusted to P-polarized light through a half-wave plate, and then its polarization state is stabilized by the third polarization beam splitter cube. It is then adjusted to S-polarized light through the third half-wave plate, and then split into two parallel lasers E1 and E2 with a certain distance through the fifth unpolarized beam splitter cube. The lasers are then incident on the sixth unpolarized beam splitter cube.

[0017] The laser beam transmitted through the sixth unpolarized beam splitter cube by laser D1 and the laser beam reflected by laser E2 by the sixth unpolarized beam splitter cube are combined and incident on the second photodetector to form the main measurement interference optical beat signal or the slave measurement interference optical beat signal.

[0018] The laser beam reflected by the sixth unpolarized beam splitter cube from laser D2 and the laser beam transmitted through the sixth unpolarized beam splitter cube from laser E1 are combined and incident on the third photodetector to form either the main reference interference beat signal or the secondary reference interference beat signal.

[0019] Preferably, the signal processing module calculates the absolute distance information of the target, specifically as follows:

[0020] Absolute distance information is calculated using the following expression:

[0021]

[0022] Where x(t1) is the absolute displacement of the target measured at time t1, ω1 and ω2 are the angular frequencies of the master laser and slave laser, respectively, and c is the speed of light in vacuum. The phase of the principal measurement interferometric beat signal at time t1. The phase of the master reference interference beat signal at time t1. Let t2 be the phase of the interferometric beat signal measured at time t2. Let t2 be the phase of the beat signal from the reference interference light.

[0023] Preferably, the signal processing module calculates the relative distance information of the target, specifically as follows:

[0024] Relative distance information is calculated using the following expression:

[0025]

[0026] or

[0027]

[0028] Where x(t2) is the absolute displacement of the target measured at time t2, and x(0) is the absolute displacement of the target measured at time 0. The phase of the principal measurement interferometric beat signal at time 0. The phase of the master reference interference beat signal at time 0. The phase of the interferometric beat signal at time 0 is the phase of the signal. The phase of the reference interference light beat signal at time 0.

[0029] Preferably, t2 and t1 satisfy: t2-t1 = the period of alternating output of master and slave lasers.

[0030] Preferably, the frequency difference between the master laser and the slave laser output by the frequency difference locking switching module is in the range of 1 GHz to 10 GHz, and the frequency difference error range is 1 Hz to 10 Hz.

[0031] Preferably, the frequency difference locking switching module outputs an alternation frequency of 1 to 1000 Hz between the master laser and the slave laser.

[0032] Preferably, the heterodyne frequency between the measurement light and the reference light output by the heterodyne beam-shifting module is 1 kHz to 10 MHz.

[0033] The advantages of this invention compared to the prior art are:

[0034] (1) This invention generates a virtual composite wavelength by alternately outputting lasers with different working frequencies to perform absolute distance measurement, while each working frequency of laser can also perform relative distance measurement, thus enabling simultaneous absolute and relative distance measurement.

[0035] (2) The modular measurement channels can be used to determine the required number of channels as needed, and multi-channel sampling and measurement can be performed simultaneously. Attached Figure Description

[0036] Figure 1 This is a schematic diagram of the measurement system structure for fusing absolute distance and relative displacement of the space optical component of the present invention.

[0037] Figure 2 This is a schematic diagram of the frequency difference locking switching module and the heterodyne beam splitting frequency shifting module of the present invention;

[0038] Figure 3This is a schematic diagram of the interferometric measurement module of the present invention. Detailed Implementation

[0039] To make the objectives, technical solutions, and advantages of the present invention clearer, the specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples.

[0040] A measurement system that fuses absolute distance and relative displacement of a space optical component, such as Figure 1 As shown, it includes a frequency difference locking switching module, a heterodyne beam-shifting module, an interferometric measurement module, and a signal processing module.

[0041] The frequency difference locking module generates a master laser and a slave laser with a fixed frequency difference and outputs them alternately.

[0042] Specifically, such as Figure 2 As shown, the frequency difference locking module includes a master laser, a slave laser, a first isolator, a first unpolarized beam splitter cube, a first switching AOM, a slave laser, a second isolator, a second switching AOM, a second unpolarized beam splitter cube, a polarized beam combiner cube, a first photodetector, and a phase-locked loop; the AOM is an acousto-optic modulator.

[0043] The master laser and slave laser are single-frequency lasers. The laser emitted by the master laser passes through a first isolator to prevent stray light backflow from causing laser frequency instability, and is then split into reflected light A1 and transmitted light A2 by a first non-polarized beam splitter cube. The laser emitted by the slave laser passes through a second isolator, and is then split into reflected light B1 and transmitted light B2 by a second non-polarized beam splitter cube. A1 and B2 are combined by a polarized beam combining cube and interfere with each other. This interference is detected by a first photodetector and forms an electrical signal that is input into a phase-locked loop (PLL). The PLL adjusts the laser frequency output by the slave laser according to the electrical signal, so that the laser output by the slave laser and the master laser have a fixed frequency difference.

[0044] Furthermore, the frequency difference between the laser emitted by the master laser and the slave laser is a fixed value between 1 GHz and 10 GHz, and the error range of the frequency difference is 1 Hz to 10 Hz.

[0045] A2 is incident on the first switching AOM. When the first switching AOM is on, the main laser is output. B1 is incident on the second switching AOM. When the second switching AOM is on, the slave laser is output. By controlling the first and second switching AOMs, the main laser and the slave laser are output alternately at a certain frequency.

[0046] Furthermore, the frequency range of the alternating output of the master laser and the slave laser is 1 to 1000 Hz.

[0047] The heterodyne beam-splitting frequency shifting module receives the master laser or slave laser output from the frequency difference locking module and outputs measurement light and reference light with fixed heterodyne frequencies.

[0048] Specifically, such as Figure 2 As shown, the heterodyne beam frequency shifting module includes a third unpolarized beam splitting cube, a first frequency shifting AOM, and a second frequency shifting AOM. The main laser is split into reflected light A3 and transmitted light A4 by the third unpolarized beam splitting cube. A3 is shifted by δω1 by the first frequency shifting AOM to form the main measurement light, and A4 is shifted by δω0 by the second frequency shifting AOM to form the main reference light.

[0049] The laser beam is split into reflected light B3 and transmitted light B4 by the third non-polarized beam splitter cube. B3 is frequency-shifted by δω0 through the second frequency-shifting AOM to form the second reference light, and B4 is frequency-shifted by δω1 through the first frequency-shifting AOM to form the second measurement light.

[0050] Furthermore, the measurement light and the reference light have a fixed heterodyne frequency |δω1-δω0|, where δω1 and δω0 are between 70 and 90 MHz, and |δω1-δω0| is between 1 kHz and 10 MHz.

[0051] The measurement module receives the measurement light and reference light output from the heterodyne beam frequency shifting module to perform heterodyne interferometry measurement on the target mirror, and outputs the measurement interferometric beat signal and the reference interferometric beat signal.

[0052] Specifically, it includes N identical heterodyne interferometric measurement optical paths. The measurement light or reference light output from the heterodyne beam splitter and frequency shifter module is coupled into an optical fiber and split according to requirements to form N sets of corresponding measurement light and reference light. N is a positive integer.

[0053] Furthermore, such as Figure 3 As shown, the heterodyne interferometry measurement optical path includes a measurement optical path and a reference optical path.

[0054] The measurement optical path includes a first collimating mirror, a first half-wave plate, a first polarizing beam splitter cube, a fourth unpolarizing beam splitter cube, a second polarizing beam splitter cube, a quarter-wave plate, a reflecting mirror, and a target mirror arranged sequentially along the measurement optical axis.

[0055] The reference optical path includes a second collimating mirror, a second half-wave plate, a third polarizing beam splitter cube, a third half-wave plate, a fifth unpolarizing beam splitter cube, a sixth unpolarizing beam splitter cube, a second photodetector, and a third photodetector arranged sequentially along the reference optical axis.

[0056] The first measurement beam is incident on the first half-wave plate through a collimating lens. The half-wave plate adjusts it to P-polarized light. Then, it passes through the first polarization beam splitter cube to stabilize its polarization state, ensuring that the laser exiting the first polarization beam splitter cube is linearly polarized light with a stable polarization state. The first measurement beam is then split into two parallel laser beams with a certain distance between them by the fourth non-polarization beam splitter cube. The two laser beams are transmitted through the second polarization beam splitter cube and then pass through a quarter-wave plate, changing from linearly polarized light to circularly polarized light. One of the beams is incident on the target mirror and reflected back. After passing through the quarter-wave plate, it changes from circularly polarized light to linearly polarized light, and is also S-polarized light. It is reflected by the first polarization beam splitter cube to form laser I1. The other beam is incident on the reflector on the optical platform and reflected back. After passing through the quarter-wave plate, it changes from circularly polarized light to linearly polarized light, and is also S-polarized light. It is reflected by the first polarization beam splitter cube to form laser I2. I1 and I2 are incident on the sixth non-polarization beam splitter cube; I = 1, 2, 3...N, where I is a positive integer.

[0057] The first reference beam is incident on the second half-wave plate through a collimating lens. The half-wave plate adjusts it to P-polarized light. Then it passes through the third polarization beam splitter cube to stabilize its polarization state, so that the laser exiting the third polarization beam splitter cube is a linearly polarized light with a stable polarization state. After passing through the third half-wave plate, the P-polarized light is converted to S-polarized light. The first measurement beam is split into two parallel beams, I3 and I4, with a certain distance between them, by the fifth unpolarized beam splitter cube and then incident on the sixth unpolarized beam splitter cube.

[0058] The laser beam transmitted through the sixth unpolarized beam splitter cube I1 and the laser beam reflected by the sixth unpolarized beam splitter cube I4 are combined and incident on the second photodetector PD. MI Above, a measurement interference optical beat signal is formed.

[0059] The laser beam reflected by I2 through the sixth unpolarized beam-splitting cube and the laser beam transmitted by I3 through the sixth unpolarized beam-splitting cube are combined and incident on the third photodetector PD. RI This forms a reference interference optical beat signal.

[0060] When the incident laser is the main measurement light and the main reference light, it forms the main measurement interference light beat signal and the main reference interference light beat signal; when the incident laser is the slave measurement light and the slave reference light, it forms the slave measurement interference light beat signal and the slave reference interference light beat signal.

[0061] When the incident laser is the main measurement light and the main reference light, PD MI The laser components at that location include:

[0062] Laser I1 transmitted through the sixth unpolarized beam-splitting cube:

[0063]

[0064] Laser I4 reflected by the sixth unpolarized beam splitter cube:

[0065]

[0066] The main measurement interference beat signal is obtained after interferometry of two laser beams:

[0067]

[0068] The frequency is: δω1-δω0;

[0069] The phase is:

[0070] When the incident laser is from the measurement light and from the reference light, PD MI The laser components at that location include: laser light transmitted through the sixth unpolarized beam-splitter cube of I1:

[0071]

[0072] Laser I4 reflected by the sixth unpolarized beam splitter cube:

[0073]

[0074] The interference of two laser beams yields the measurement interference beat signal:

[0075]

[0076] The frequency is: δω1-δω0;

[0077] The phase is:

[0078] Where E represents the electric field intensity of the laser, A represents the amplitude of the light, z represents the geometric optical path length of the laser propagation, t represents time, and ω1 and ω2 represent the angular frequencies of the laser emitted by the master and slave lasers, respectively. The laser phase is represented by e, the natural logarithm by i, and the imaginary unit by π. The subscripts "master" and "slave" indicate that the light source is the master laser and the light source is the slave laser, respectively. I represents the I-th heterodyne interferometry optical path. PD MI The second photodetector represents the I-th heterodyne interferometry measurement optical path. The measurement light I represents the laser transmitted through the sixth unpolarized beam splitter cube via I1, and the reference light I represents the laser reflected through the sixth unpolarized beam splitter cube via I4.

[0079] Signal processing module: Calculates the relative distance information of the target using the main measurement interferometric optical beat signal and the main reference interferometric optical beat signal, or from the measurement interferometric optical beat signal and the reference interferometric optical beat signal; calculates the absolute distance information of the target using the main measurement interferometric optical beat signal, the main reference interferometric optical beat signal, the measurement interferometric optical beat signal, and the reference interferometric optical beat signal.

[0080] Specifically, at time t1, the first switch turns the AOM on, the second switch turns the AOM off, and the main laser is output. The signal processing module acquires the main measurement interference beat signal and the main reference interference beat signal, and uses a multi-channel phase meter to perform phase detection to obtain the phase of the main measurement interference beat signal and the phase of the main reference interference beat signal at time t1.

[0081] At time t2, the first switching AOM is off, and the second switching AOM is on. The output is obtained from the laser signal processing module, which acquires the measurement interference optical beat signal and the reference interference optical beat signal. A multi-channel phase meter is used for phase detection to obtain the phase of the measurement interference optical beat signal and the phase of the reference interference optical beat signal at time t2.

[0082] Then the relative absolute distance information at time t1 is:

[0083] Relative distance information:

[0084]

[0085] or

[0086]

[0087] Absolute distance information:

[0088]

[0089] In the formula, x represents the distance being measured, c represents the speed of light in a vacuum, and x I (0) indicates the absolute displacement of the target measured at time 0. This indicates the phase of the principal measurement interferometric beat signal at time 0. This indicates the phase of the master reference interference beat signal at time 0. This indicates the phase of the measured interferometric beat signal at time 0. This indicates the phase of the optical beat signal from the reference interference at time 0.

[0090] The contents not described in detail in this specification are common knowledge to those skilled in the art.

Claims

1. A measurement system for fusing absolute distance and relative displacement of a space optical component, characterized in that, It includes a frequency difference locking switching module, a heterodyne beam splitting frequency shifting module, an interferometric measurement module, and a signal processing module; Frequency difference locking switching module: alternately outputs master laser and slave laser with a fixed frequency difference; Heterodyne beam splitting and frequency shifting module: splits and shifts the frequency of the master laser or slave laser, and outputs master measurement light and master reference light, or slave measurement light and slave reference light with fixed heterodyne frequencies; Interferometric measurement module: Performs heterodyne interferometric measurement on the target using the master measurement light and master reference light, or the slave measurement light and slave reference light, and outputs the master measurement interferometric beam signal and master reference interferometric beam signal, or the slave measurement interferometric beam signal and slave reference interferometric beam signal; Signal processing module: Calculates the relative distance information of the target using the main measurement interferometric optical beat signal and the main reference interferometric optical beat signal, or from the measurement interferometric optical beat signal and the reference interferometric optical beat signal; calculates the absolute distance information of the target using the main measurement interferometric optical beat signal, the main reference interferometric optical beat signal, the measurement interferometric optical beat signal, and the reference interferometric optical beat signal. The frequency difference locking switching module includes a master laser, a first unpolarized beam splitter cube, a first switching AOM, a slave laser, a second unpolarized beam splitter cube, a second switching AOM, an unpolarized beam combiner cube, a first photodetector, and a phase-locked loop; The laser emitted by the master laser is reflected by the first non-polarized beam splitter cube to form laser A, and transmitted to form the master laser. The laser emitted by the slave laser is transmitted by the second non-polarized beam splitter cube to form laser B, and reflected to form the slave laser. Laser A and laser B are combined by a non-polarized beam combiner cube to form laser C, which is incident on the first photodetector to form a detection signal. The phase-locked loop adjusts the laser frequency output by the slave laser according to the detection signal, so that the laser emitted by the slave laser and the master laser have a fixed frequency difference. The master laser is controlled by a first switching AOM, and the slave laser is controlled by a second switching AOM. By controlling the first and second switching AOMs, the master laser and the slave laser are output alternately.

2. The measurement system for fusing absolute distance and relative displacement of a space optical component according to claim 1, characterized in that, The heterodyne beam frequency shifting module includes a third unpolarized beam splitter cube, a first frequency shifting AOM, and a second frequency shifting AOM. The main laser, after passing through the third unpolarized beam splitter cube, has its reflected and transmitted light shifted by the first and second frequency shifting AOMs respectively, and is then output as the main measurement light and the main reference light. The secondary laser, after passing through the third unpolarized beam splitter cube, has its transmitted and reflected light shifted by the first and second frequency shifting AOMs respectively, and is then output as the secondary measurement light and the secondary reference light.

3. The measurement system for fusing absolute distance and relative displacement of a space optical component according to claim 2, characterized in that, The interferometric measurement module includes one or more sets of interferometric measurement optical paths. Each set of interferometric measurement optical paths includes a measurement optical path and a reference optical path. The measurement optical path includes a first half-wave plate, a first polarization beam splitter cube, a fourth non-polarization beam splitter cube, a quarter-wave plate, a reflector, and a measurement target mirror. The reference optical path includes a second half-wave plate, a second polarization beam splitter cube, a third half-wave plate, a fifth non-polarization beam splitter cube, a sixth non-polarization beam splitter cube, a second photodetector, and a third photodetector. The main or secondary measurement light is adjusted to P-polarized light through a half-wave plate, and then its polarization state is stabilized by the first polarization beam splitter cube. It is then split into two parallel laser beams with a certain distance through the fourth non-polarization beam splitter cube. The two laser beams are transmitted through the second polarization beam splitter cube and then adjusted to circular polarization by a quarter-wave plate. One of the beams is incident on the measurement target and reflected back. It is then adjusted to S-polarized light by a quarter-wave plate and reflected by the first polarization beam splitter cube to form laser D1. The other beam is incident on the mirror and reflected back. It is then adjusted to S-polarized light by a quarter-wave plate and reflected by the first polarization beam splitter cube to form laser D2. Lasers D1 and D2 are incident on the sixth non-polarization beam splitter cube. The main reference light or the secondary reference light is adjusted to P-polarized light through a half-wave plate, and then its polarization state is stabilized by the third polarization beam splitter cube. It is then adjusted to S-polarized light through the third half-wave plate, and then split into two parallel lasers E1 and E2 with a certain distance through the fifth unpolarized beam splitter cube, and then incident on the sixth unpolarized beam splitter cube. The laser beam transmitted through the sixth unpolarized beam splitter cube by laser D1 and the laser beam reflected by laser E2 by the sixth unpolarized beam splitter cube are combined and incident on the second photodetector to form the main measurement interference optical beat signal or the slave measurement interference optical beat signal. The laser beam reflected by the sixth unpolarized beam splitter cube from laser D2 and the laser beam transmitted by the sixth unpolarized beam splitter cube from laser E1 are combined and incident on the third photodetector to form either the main reference interference beat signal or the secondary reference interference beat signal.

4. The measurement system for fusing absolute distance and relative displacement of a space optical component according to claim 3, characterized in that, The signal processing module calculates the absolute distance information of the target, specifically: Absolute distance information is calculated using the following expression: = in, for Continuously measure the absolute displacement of the target. These are the angular frequencies of the master laser and the slave laser, respectively. The speed of light in a vacuum for The phase of the primary measurement interferometric beat signal at any given moment. for Phase of the primary reference interference optical beat signal at time. for The phase of the interferometric optical beat signal is measured at any given moment. for The phase of the reference interference light beat signal at any given moment.

5. The measurement system for fusing absolute distance and relative displacement of a space optical component according to claim 4, characterized in that, The signal processing module calculates the relative distance information of the target, specifically: Relative distance information is calculated using the following expression: or in, for Continuously measure the absolute displacement of the target. The absolute displacement of the target is measured at time 0. The phase of the principal measurement interferometric beat signal at time 0. The phase of the master reference interference beat signal at time 0. The phase of the interferometric beat signal at time 0 is the phase of the signal. The phase of the reference interference light beat signal at time 0.

6. The measurement system for fusing absolute distance and relative displacement of a space optical component according to claim 5, characterized in that, : =The cycle of alternating output of master and slave lasers.

7. A measurement system for fusing absolute distance and relative displacement of a space optical component according to any one of claims 1 to 6, characterized in that, The frequency difference between the master laser and the slave laser output by the frequency difference locking switching module ranges from 1 GHz to 10 GHz, and the frequency difference error ranges from 1 Hz to 10 Hz.

8. A measurement system for fusing absolute distance and relative displacement of a space optical component according to any one of claims 1 to 6, characterized in that, The frequency difference locking switching module outputs a master laser and a slave laser with an alternation frequency of 1~1000Hz.

9. A measurement system for fusing absolute distance and relative displacement of a space optical component according to any one of claims 1 to 6, characterized in that, The heterodyne frequency between the measurement light and the reference light output by the heterodyne beam splitter frequency shifter is 1 kHz to 10 MHz.

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