Full-automatic capturing and tracking system based on four-quadrant detector

Abstract

The invention discloses a full-automatic capturing and tracking system based on a four-quadrant detector, and belongs to the technical field of space laser communication servo tracking. The problem that an existing space laser communication system is prone to being failed in capturing and non-convergent in tracking under the condition of radio frequency interference and without auxiliary guidance is solved. The system comprises a master communication terminal and a slave communication terminal, the master communication terminal and the slave communication terminal have the same structure, the master communication terminal and the slave communication terminal cooperate together to complete full-automatic capture, and after full-automatic capture is completed, the master communication terminal and the slave communication terminal perform corresponding data transmission, that is, a tracking mode is entered. The main communication terminal comprises a reflector system, a beacon transmitting antenna, a transmission-type optical antenna, a beacon laser, a signal processing board, a fine tracking servo controller, a fine tracking fast reflecting mirror, a first reflector, a coarse / fine tracking camera, a first convergent lens, an energy spectroscope, a four-quadrant detector, a second convergent lens and a first wavelength spectroscope.

Description

Technical Field

[0001] The invention belongs to the technical field of space laser communication servo tracking, and in particular relates to a full-automatic capture and tracking system based on a four-quadrant detector. Background Art

[0002] Space laser communication, with its high bandwidth, low latency, and strong anti-interference capabilities, has gradually become the core means to solve the "last mile of optical fiber" problem. However, due to the small beam divergence angle and difficulty in capture and alignment of space laser communication, especially in the case of radio frequency silence and electromagnetic interference, the capture and link establishment of space laser communication systems are seriously affected. At the same time, in existing space laser communication systems, low-bandwidth radio frequency services are usually used as auxiliary command transmission links for dual-end capture and convergence tracking. In the real battlefield and under radio frequency interference, capture failure and non-convergence of tracking are prone to occur without auxiliary guidance. Summary of the invention

[0003] In order to solve the problem that the existing space laser communication system is prone to capture failure and tracking non-convergence when there is no auxiliary guidance under the condition of radio frequency interference, the present invention provides a fully automatic capture and tracking system based on a four-quadrant detector.

[0004] The system includes a master communication terminal and a slave communication terminal. The master communication terminal and the slave communication terminal have the same structure. The master communication terminal and the slave communication terminal cooperate to complete full-automatic capture. After the full-automatic capture is completed, the master communication terminal and the slave communication terminal perform corresponding data transmission, that is, enter the tracking mode. The master communication terminal includes a reflector system, a beacon transmitting antenna, a transmission optical antenna, a beacon laser, a signal processing board, a fine tracking servo controller, a fine tracking fast reflection mirror, a first reflector, a coarse / fine tracking camera, a first converging lens, an energy spectroscope, a four-quadrant detector, a second converging lens and a first wavelength spectroscope; After passing through the reflector system, the incident light enters the transmission optical antenna for beam reduction, and then enters the fine tracking fast reflex mirror through the first reflector. The fine tracking fast reflex mirror reflects the light beam to the energy spectrometer. The energy spectrometer divides the light beam into two beams in proportion. One beam passes through the first converging lens and enters the coarse / fine tracking camera, and the other beam enters the first wavelength spectrometer. The first wavelength spectrometer reflects part of the light beam and enters the second converging lens. After being emitted, it enters the four-quadrant detector. The coarse / fine tracking camera and the four-quadrant detector are both connected to the signal processing board, and the signal processing board is also connected to the beacon laser, the fine tracking servo controller and the reflector system respectively. The fine tracking servo controller controls the movement of the fine tracking fast reflex mirror.

[0005] Furthermore, the reflector system includes a first reflector and a second reflector, and the first reflector and the second reflector are driven to rotate by a pitch motor at the same time, and the first reflector is driven to rotate by an azimuth motor.

[0006] Furthermore, the main communication terminal also includes a second wavelength spectrometer, a third converging lens, a pre-optical amplifier and an avalanche photodetector. The light beam transmitted by the first wavelength spectrometer enters the second wavelength spectrometer, is reflected into the third converging lens, and then is emitted, and enters the avalanche photodetector after passing through the pre-optical amplifier.

[0007] Furthermore, the main communication terminal also includes a pre-aiming quick-reflection mirror, a fourth focusing lens, an erbium-doped fiber amplifier and a semiconductor laser. The light beam emitted by the semiconductor laser passes through the erbium-doped fiber amplifier and enters the fourth focusing lens. After being emitted, it enters the pre-aiming quick-reflection mirror and then is transmitted through the second wavelength splitter and output along the optical path.

[0008] Furthermore, when the fully automatic capture and tracking system is used for automatic capture, the system works in three stages, namely, the capture stage, the convergence and tracking stage, and the communication fine-tuning stage.

[0009] Furthermore, the specific workflow of the capture phase is as follows: S61, master communication terminal: calculate the position and pointing angle of the slave communication terminal through the ephemeris table, and control the reflector system to perform initial pointing; S62, main communication terminal: after completing the initial pointing, the signal processing board receives feedback that the reflector system has reached the specified position, and the signal processing board controls the beacon laser to send a capture modulation signal, wherein the capture modulation signal has a pulse width of 1 μs and a pulse interval of 5 μs, and the signal processing board simultaneously controls the reflector system to synchronously start spiral scanning; S63, from the communication terminal: the signal processing board controls the reflector system to start spiral scanning. After the coarse / fine tracking camera receives the capture modulation signal sent by the main communication terminal, it sends the information to the signal processing board, and the signal processing board continues to control the reflector system to perform spiral scanning.

[0010] Furthermore, the specific workflow of the convergence tracking stage is as follows: S71, main communication terminal: when the coarse / fine tracking camera detects the light spot and the four-quadrant detector synchronously detects the energy, after the signal processing board receives the above information, the signal processing board controls the beacon laser to send a convergence tracking modulation signal, wherein the pulse width of the convergence tracking modulation signal is 1 μs and the pulse interval is 10 μs; S72, main communication terminal: the coarse / fine tracking camera outputs the miss distance to the signal processing board, and the signal processing board controls the reflector system to reduce the spiral scanning amplitude; S73, from the communication terminal: the coarse / fine tracking camera receives the convergence tracking modulation signal sent by the master communication terminal, and sends the information to the signal processing board, which simultaneously controls the reflector system to synchronously start reducing the spiral scanning amplitude; S74, main communication terminal: when the coarse / fine tracking camera detects that the light spot converges to the center area of ​​the camera, the coarse / fine tracking camera switches to a small window for fine tracking convergence; S75, from the communication terminal: when the coarse / fine tracking camera detects that the light spot converges to the central area, the coarse / fine tracking camera switches to a small window for fine tracking convergence; S76, main communication terminal: When the fine tracking convergence is completed, the four-quadrant detector performs spot center detection. At this time, the signal processing board receives the signal output by the four quadrants of the four-quadrant detector. The signal is the amplitude and information of the opposite side convergence tracking signal.

[0011] Furthermore, the specific workflow of the communication fine-tuning stage is as follows: S81, main communication terminal: when it is detected that the signal amplitudes output by the four quadrants of the four-quadrant detector are the same, the signal processing board controls the beacon laser to send a communication fine-tuning modulation signal, wherein the pulse width of the communication fine-tuning modulation signal is 1 μs and the pulse interval is 15 μs; S82, main communication terminal: when the signal received by the avalanche photodetector gradually increases, the fine tracking servo controller controls the fine tracking fast reflection mirror to make fine adjustments, and the signal processing board continues to control the beacon laser to send a communication fine adjustment modulation signal; S83, from the communication terminal: after receiving the communication fine-tuning modulation signal, the fine tracking servo controller controls the fine tracking fast reflection mirror to perform fine-tuning; S84, main communication terminal: when the signal received by the avalanche photodetector decreases, the signal processing board controls the beacon laser to send a continuous "1" signal and stops fine-tuning the fast-reflection mirror; S85, slave communication terminal: after receiving continuous "1" signals, stop fine tracking and fine adjustment of the fast reflection mirror, and the master communication terminal and the slave communication terminal complete automatic capture.

[0012] The beneficial effects of the system described in the present invention are as follows: it is proposed to modulate beacon light, modulate capture, tracking, communication and other command information in the beacon light, use a four-quadrant detector as an optical command information detector for capture and convergence tracking, and coordinate the controller with the coarse servo motor control and fine servo control to achieve fully automatic capture and tracking, effectively avoiding the difficulty of space laser communication system in capturing and establishing a link under RF silence and electromagnetic interference; at the same time, the traditional coarse capture and fine capture process is adjusted and refined, split into capture stage, convergence tracking stage and communication fine-tuning stage, so that the terminal alignment is more accurate. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a structural diagram of a fully automatic capture and tracking system based on a four-quadrant detector according to an embodiment of the present invention; Figure 2It is a schematic diagram of modulation signals at different stages of a fully automatic acquisition and tracking system based on a four-quadrant detector according to an embodiment of the present invention; Figure 3 This is a workflow diagram of a fully automatic capture and tracking system based on a four-quadrant detector described in an embodiment of the present invention. DETAILED DESCRIPTION

[0014] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the protection scope of the present invention.

[0015] Embodiment 1, This embodiment provides a fully automatic capture and tracking system based on a four-quadrant detector. The system structure diagram is shown in FIG. Figure 1 As shown, the system includes a master communication terminal and a slave communication terminal, the structures of the master communication terminal and the slave communication terminal are the same, the master communication terminal and the slave communication terminal cooperate to complete the full-automatic capture, after the full-automatic capture is completed, the master communication terminal and the slave communication terminal perform corresponding data transmission, that is, enter the tracking mode, the system includes a reflector system 0, a beacon transmitting antenna 3, a transmission optical antenna 4, a beacon laser 5, a signal processing board 6, a fine tracking servo controller 7, a fine tracking fast reflection mirror 8, a first reflector 9, a coarse / fine tracking camera 10, a first converging lens 11, an energy spectroscope 12, a four-quadrant detector 13, a second converging lens 14 and a first wavelength spectroscope 15; After passing through the reflector system 0, the incident light enters the transmission optical antenna 4 for beam reduction, and then enters the fine tracking fast reflex mirror 8 through the first reflector 9. The fine tracking fast reflex mirror 8 reflects the light beam to the energy spectroscope 12. The energy spectroscope 12 divides the light beam into two beams in proportion. One beam passes through the first converging lens 11 and enters the coarse / fine tracking camera 10, and the other beam enters the first wavelength spectroscope 15. The first wavelength spectroscope 15 reflects part of the light beam and enters the second converging lens 14. After being emitted, it enters the four-quadrant detector 13. The coarse / fine tracking camera 10 and the four-quadrant detector 13 are both connected to the signal processing board 6, and the signal processing board 6 is also connected to the beacon laser 5, the fine tracking servo controller 7 and the reflector system 0 respectively. The fine tracking servo controller 7 controls the movement of the fine tracking fast reflex mirror 8.

[0016] The reflector system 0 includes a first reflector 1 and a second reflector 2. The first reflector 1 and the second reflector 2 are simultaneously driven to rotate by a pitch motor, and the first reflector 1 is driven to rotate by an azimuth motor.

[0017] Embodiment 2, This embodiment is a further limitation of the embodiment 1, wherein the main communication terminal further comprises a second wavelength spectroscope 16, a third convergent lens 17, a pre-optical amplifier 22 and an avalanche photodetector 24, the light beam transmitted by the first wavelength spectroscope 15 enters the second wavelength spectroscope 16, reflects into the third convergent lens 17 and then exits, and enters the avalanche photodetector 24 after passing through the pre-optical amplifier 22; the main communication terminal further comprises an advance aiming fast reflection mirror 18, a fourth convergent lens 19, an erbium-doped fiber amplifier 23 and a semiconductor laser 25, the light beam emitted by the semiconductor laser 25 enters the fourth convergent lens 19 after passing through the erbium-doped fiber amplifier 23, enters the advance aiming fast reflection mirror 18 after exiting, and then transmits through the second wavelength spectroscope 16 and outputs along the optical path; the above devices are mainly used for the main communication terminal and the slave communication terminal to perform corresponding data transmission after completing the fully automatic capture. In addition, it also comprises a communication receiving optical fiber fixing frame 20 and a communication transmitting optical fiber fixing frame 21 for fixing optical fibers.

[0018] Embodiment 3, This embodiment is a further limitation of the embodiment 1. When the fully automatic capture and tracking system is used for automatic capture, the system works in three stages, namely, the capture stage, the convergence and tracking stage, and the communication fine-tuning stage. In different stages, the master communication terminal will transmit different modulation signals, and the slave communication terminal will make corresponding adjustments according to the different modulation signals. The specific modulation signals in different stages are as follows: Figure 2 shown.

[0019] like Figure 3 This is a work flow chart of the fully automatic capture and tracking system of the present invention, wherein QD represents the four-quadrant detector 13, and APD represents the avalanche photodetector 24. The entire work flow can be completed automatically without human judgment.

[0020] The specific workflow of the capture phase is as follows: S1, master communication terminal: calculate the position and pointing angle of the slave communication terminal through the ephemeris table, and control the reflector system 0 for initial pointing; S2, main communication terminal: after completing the initial pointing, the signal processing board 6 receives feedback that the reflector system 0 has reached the specified position. At this time, the coarse / fine tracking camera 10 and the four-quadrant detector 13 have not received any optical signals. The signal processing board 6 controls the beacon laser 5 to send a capture modulation signal. The capture modulation signal has a pulse width of 1 μs and a pulse interval of 5 μs. The signal processing board 6 also controls the reflector system 0 to synchronously start spiral scanning. S3. From the communication terminal: the signal processing board 6 controls the reflector system 0 to start spiral scanning. After the coarse / fine tracking camera 10 receives the capture modulation signal sent by the main communication terminal, it sends the information to the signal processing board 6. The signal processing board 6 continues to control the reflector system 0 to perform spiral scanning. At this point, both ends perform spiral scanning in the capture uncertainty area.

[0021] The specific workflow of the convergence tracking stage is as follows: S1, main communication terminal: when the coarse / fine tracking camera 10 detects the light spot and the four-quadrant detector 13 synchronously detects the energy, the light spot is at the edge of the target surface of the coarse / fine tracking camera 10 or one of the four-quadrant detectors 13; after the signal processing board 6 receives the above information, the signal processing board 6 controls the beacon laser 5 to send a convergence tracking modulation signal, wherein the pulse width of the convergence tracking modulation signal is 1 μs and the pulse interval is 10 μs; S2, main communication terminal: the coarse / fine tracking camera 10 outputs the miss distance to the signal processing board 6, and the signal processing board 6 controls the reflector system 0 to reduce the spiral scanning amplitude; S3, from the communication terminal: the coarse / fine tracking camera 10 receives the convergence tracking modulation signal sent by the main communication terminal, and sends the information to the signal processing board 6, which simultaneously controls the reflector system 0 to synchronously start reducing the spiral scanning amplitude; S4, main communication terminal: when the coarse / fine tracking camera 10 detects that the light spot converges to the center area of ​​the camera, the coarse / fine tracking camera 10 switches to a small window for fine tracking convergence; S5, from the communication terminal: when the coarse / fine tracking camera 10 detects that the light spot converges to the central area, the coarse / fine tracking camera 10 switches to a small window for fine tracking convergence; S6, main communication terminal: When the fine tracking convergence is completed, the four-quadrant detector 13 performs spot center detection. At this time, the signal processing board 6 receives the signals output by the four quadrants of the four-quadrant detector 13, and the signals are the amplitude and information of the opposite side convergence tracking signal.

[0022] The specific workflow of the communication fine-tuning stage is as follows: S1, main communication terminal: when it is detected that the signal amplitudes outputted by the four quadrants of the four-quadrant detector 13 are the same, the signal processing board 6 controls the beacon laser 5 to send a communication fine-tuning modulation signal, wherein the pulse width of the communication fine-tuning modulation signal is 1 μs and the pulse interval is 15 μs; S2, main communication terminal: when the signal received by the avalanche photodetector 24 gradually increases, the fine tracking servo controller 7 controls the fine tracking fast reflection mirror 8 to make fine adjustments, and the signal processing board 6 continues to control the beacon laser 5 to send a communication fine adjustment modulation signal; S3, from the communication terminal: after receiving the communication fine-tuning modulation signal, the fine tracking servo controller 7 controls the fine tracking fast reflection mirror 8 to perform fine-tuning; S4, main communication terminal: when the signal received by the avalanche photodetector 24 decreases, the signal processing board 6 controls the beacon laser 5 to send a continuous "1" signal and stops the fine tracking of the fast reflection mirror 8; S5, slave communication terminal: after receiving continuous "1" signals, stop fine tracking and fine adjustment of the fast-reflection mirror 8, and the master communication terminal and the slave communication terminal complete automatic capture.

[0023] Tracking and communication are not coaxial, resulting in the communication receiving energy not reaching the peak after tracking to the center of the light spot on the image. Therefore, it is necessary to scan the receiving energy peak and enter the communication fine-tuning stage. The energy received by the avalanche photodetector 24 is used as feedback to fine-tune the precise tracking fast-reflection mirror to maximize the communication energy.

[0024] Embodiment 4, This embodiment is a further limitation of Embodiment 1. After the full-automatic capture is completed, the master communication terminal and the slave communication terminal perform corresponding data transmission. At this time, the communication receiving link of the master communication terminal is a link composed of the second wavelength spectrometer 16, the third converging lens 17, the pre-optical amplifier 22 and the avalanche photodetector 24; at this time, the communication transmitting link of the master communication terminal is a link composed of the erbium-doped fiber amplifier 23, the fourth converging lens 19, the advance aiming fast reflection mirror 18 and the second wavelength spectrometer 16.

Claims

1. A fully automatic capture and tracking system based on a four-quadrant detector, the system comprising a master communication terminal and a slave communication terminal, the master communication terminal and the slave communication terminal having the same structure, the master communication terminal and the slave communication terminal cooperate to complete fully automatic capture, after completing fully automatic capture, the master communication terminal and the slave communication terminal perform corresponding data transmission, i.e. enter a tracking mode, characterized in that: The main communication terminal comprises a reflector system (0), a beacon transmitting antenna (3), a transmissive optical antenna (4), a beacon laser (5), a signal processing board (6), a fine tracking servo controller (7), a fine tracking fast reflection mirror (8), a first reflector (9), a coarse / fine tracking camera (10), a first converging lens (11), an energy spectroscope (12), a four-quadrant detector (13), a second converging lens (14) and a first wavelength spectroscope (15); After passing through the reflector system (0), the incident light enters the transmission optical antenna (4) for beam contraction, and then enters the fine tracking fast reflection mirror (8) through the first reflector (9). The fine tracking fast reflection mirror (8) reflects the light beam to the energy beam splitter (12). The energy beam splitter (12) divides the light beam into two beams in proportion. One beam passes through the first converging lens (11) and enters the coarse / fine tracking camera (10), and the other beam enters the first wavelength beam splitter (15). The first wavelength beam splitter (15) reflects part of the light beam and enters the second converging lens (14). After exiting, the light beam enters the four-quadrant detector (13). The coarse / fine tracking camera (10) and the four-quadrant detector (13) are both connected to the signal processing board (6). The signal processing board (6) is also connected to the beacon laser (5), the fine tracking servo controller (7) and the reflector system (0) respectively. The fine tracking servo controller (7) controls the movement of the fine tracking fast reflection mirror (8).

2. The fully automatic capture and tracking system based on a four-quadrant detector according to claim 1 is characterized in that: The reflector system (0) comprises a first reflector (1) and a second reflector (2), wherein the first reflector (1) and the second reflector (2) are driven to rotate by a pitch motor at the same time, and the first reflector (1) is driven to rotate by an azimuth motor.

3. The fully automatic capture and tracking system based on the four-quadrant detector according to claim 2 is characterized in that: The main communication terminal further comprises a second wavelength spectroscope (16), a third converging lens (17), a pre-optical amplifier (22) and an avalanche photodetector (24); the light beam transmitted by the first wavelength spectroscope (15) is incident on the second wavelength spectroscope (16), reflected into the third converging lens (17), and then emitted, passing through the pre-optical amplifier (22) and then entering the avalanche photodetector (24).

4. The fully automatic capture and tracking system based on a four-quadrant detector according to claim 3 is characterized in that: The main communication terminal further comprises a pre-aiming quick-reflection mirror (18), a fourth focusing lens (19), an erbium-doped fiber amplifier (23) and a semiconductor laser (25); a light beam emitted by the semiconductor laser (25) passes through the erbium-doped fiber amplifier (23) and then enters the fourth focusing lens (19), and then enters the pre-aiming quick-reflection mirror (18) and then is transmitted through the second wavelength splitter (16) and output along the optical path.

5. The fully automatic capture and tracking system based on a four-quadrant detector according to claim 4 is characterized in that: When the fully automatic capture and tracking system is used for automatic capture, the system works in three stages, namely, the capture stage, the convergence and tracking stage, and the communication fine-tuning stage.

6. The fully automatic capture and tracking system based on a four-quadrant detector according to claim 5, characterized in that: The specific workflow of the capture phase is as follows: S61, the master communication terminal: calculates the position and pointing angle of the slave communication terminal through the ephemeris table, and controls the reflector system (0) to perform initial pointing; S62, main communication terminal: after completing the initial pointing, the signal processing board (6) receives feedback that the reflector system (0) has reached the designated position, and the signal processing board (6) controls the beacon laser (5) to send a capture modulation signal, wherein the capture modulation signal has a pulse width of 1 μs and a pulse interval of 5 μs, and the signal processing board (6) simultaneously controls the reflector system (0) to synchronously start spiral scanning; S63, from the communication terminal: the signal processing board (6) controls the reflector system (0) to start spiral scanning, and after the coarse / fine tracking camera (10) receives the capture modulation signal sent by the main communication terminal, it sends the information to the signal processing board (6), and the signal processing board (6) continues to control the reflector system (0) to perform spiral scanning.

7. The fully automatic capture and tracking system based on a four-quadrant detector according to claim 6, characterized in that: The specific workflow of the convergence tracking stage is as follows: S71, main communication terminal: when the coarse / fine tracking camera (10) detects a light spot and the four-quadrant detector (13) synchronously detects energy, after the signal processing board (6) receives the above information, the signal processing board (6) controls the beacon laser (5) to send a convergence tracking modulation signal, wherein the pulse width of the convergence tracking modulation signal is 1 μs and the pulse interval is 10 μs; S72, main communication terminal: the coarse / fine tracking camera (10) outputs the miss amount to the signal processing board (6), and the signal processing board (6) controls the reflector system (0) to reduce the spiral scanning amplitude; S73, from the communication terminal: the coarse / fine tracking camera (10) receives the convergence tracking modulation signal sent by the main communication terminal, and sends the information to the signal processing board (6), and the signal processing board (6) simultaneously controls the reflector system (0) to synchronously start reducing the spiral scanning amplitude; S74, main communication terminal: when the coarse / fine tracking camera (10) detects that the light spot converges to the center area of ​​the camera, the coarse / fine tracking camera (10) switches to a small window for fine tracking convergence; S75, from the communication terminal: when the coarse / fine tracking camera (10) detects that the light spot converges to the central area, the coarse / fine tracking camera (10) switches to a small window for fine tracking convergence; S76, main communication terminal: When the fine tracking convergence is completed, the four-quadrant detector (13) performs spot center detection. At this time, the signal processing board (6) receives the signals output by the four quadrants of the four-quadrant detector (13), and the signals are the amplitude and information of the opposite side convergence tracking signal.

8. The fully automatic capture and tracking system based on a four-quadrant detector according to claim 7, characterized in that: The specific workflow of the communication fine-tuning stage is as follows: S81, main communication terminal: when it is detected that the signal amplitudes outputted by the four quadrants of the four-quadrant detector (13) are the same, the signal processing board (6) controls the beacon laser (5) to send a communication fine-tuning modulation signal, wherein the pulse width of the communication fine-tuning modulation signal is 1 μs and the pulse interval is 15 μs; S82, main communication terminal: when the signal received by the avalanche photodetector (24) gradually increases, the fine tracking servo controller (7) controls the fine tracking fast reflection mirror (8) to perform fine adjustment, and the signal processing board (6) continues to control the beacon laser (5) to send a communication fine adjustment modulation signal; S83, from the communication terminal: after receiving the communication fine-tuning modulation signal, the fine tracking servo controller (7) controls the fine tracking fast reflection mirror (8) to perform fine-tuning; S84, main communication terminal: when the signal received by the avalanche photodetector (24) decreases, the signal processing board (6) controls the beacon laser (5) to send a continuous "1" signal and stops the fine tracking fast reflection mirror (8) from fine-tuning; S85, slave communication terminal: after receiving continuous "1" signals, stop fine tracking and fine adjustment of the fast reflection mirror (8), and the master communication terminal and the slave communication terminal complete automatic capture.

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