CN-121984586-A - Space laser communication method and system based on cascade liquid crystal polarization grating device

CN121984586ACN 121984586 ACN121984586 ACN 121984586ACN-121984586-A

Abstract

The invention discloses a space laser communication method and a space laser communication system based on a cascade liquid crystal polarization grating device, and relates to the technical field of space laser communication. Discrete deflection is performed based on the electronically controlled liquid crystal phase by using a cascaded liquid crystal polarization grating module to output a coarse pointing beam, and continuous angle compensation is performed by using a fine tracking deflection module. The control module generates a state code based on the coarse tracking error and looks up a table to output a grating driving signal, drives the fine tracking deflection module based on the fine tracking error, updates the state code based on the continuous compensation angle or the pointing error when the continuous compensation angle reaches the upper limit or the pointing error exceeds the limit, drives the grating to deflect discretely and resets the fine tracking deflection module to zero. The invention realizes large-scale, high-precision and stable pointing control by the cooperation of non-mechanical discrete coarse pointing and continuous fine tracking and by combining a table look-up driving, saturation unloading and pointing monitoring mechanism. The multichannel waveform pre-emphasis driving and Gray code coding are further combined, so that the transient disturbance of state switching is effectively restrained.

Inventors

LIU XIANG
Jia Zhenchuan
XIANG CHANG
ZHANG ZHUOCHENG
CHEN CHAO
LIAO XIANGLIN

Assignees

成都光致星联科技有限公司

Dates

Publication Date: 20260505
Application Date: 20260204

Claims (10)

1. The space laser communication method based on the cascade liquid crystal polarization grating device is characterized by comprising the following steps of: step one, an optical antenna receives an incident beam, a beam shrinking module shrinks the incident beam to obtain a beam shrinking beam, and a cascade liquid crystal polarization grating module performs phase modulation on the beam shrinking beam based on an electric control liquid crystal phase and discretely deflects and outputs a coarse pointing beam; step two, the first beam splitting module splits the coarse directional beam to obtain a coarse sampling beam, and the coarse tracking detector outputs a coarse tracking error signal to the control module based on the coarse sampling beam; Third, the fine tracking deflection module outputs a fine pointing light beam through continuous angle compensation of the coarse pointing light beam, the second splitting module splits the fine pointing light beam to obtain a fine sampling light beam, and the fine tracking detector outputs a fine tracking error signal to the control module and the pointing monitoring module based on the fine sampling light beam; step four, the control module stores a state code mapping table, generates a state code based on the coarse tracking error signal and executes table look-up output, wherein the table look-up output is based on the state code to look up a table in the state code mapping table to output a grating driving signal to the cascade liquid crystal polarization grating module; Step five, the control module calculates a continuous compensation angle based on the fine tracking error signal and calculates a continuous compensation angle absolute value, outputs a fast-reflecting mirror driving signal to the fine tracking deflection module, and the continuous compensation angle absolute value reaches the upper limit of the compensation angle of the fine tracking deflection module; And step six, the pointing monitoring module calculates a pointing error amplitude based on the fine tracking error signal, when the pointing error amplitude is larger than a pointing error threshold, the control module calculates a state code update amount based on the pointing error amplitude and updates the state code, resets the continuous compensation angle to 0 angle and outputs a fast-reflection mirror driving signal to the fine tracking deflection module, and the control module performs table look-up output based on the updated state code.
2. The space laser communication method based on the cascade liquid crystal polarization grating device, as claimed in claim 1, is characterized in that the beam shrinking module is used for shrinking the incident beam to obtain the condensed beam, and comprises a reflective telescopic system, wherein the reflective telescopic system is used for compressing the incident beam to the light-transmitting aperture range of the cascade liquid crystal polarization grating module.
3. The method for spatial laser communication based on cascaded liquid crystal polarization grating device according to claim 1, wherein the cascaded liquid crystal polarization grating module is a multi-layer stacked structure in which a plurality of electrically controlled liquid crystal half wave plate layers and a plurality of liquid crystal polarization grating LCPG layers are alternately stacked.
4. The method for spatial laser communication based on cascaded liquid crystal polarization grating device according to claim 1, wherein the cascaded liquid crystal polarization grating module performs phase modulation on the condensed beam based on the electronically controlled liquid crystal phase and discretely deflects the condensed beam to output a coarse directional beam, comprising: The coarse pointing beam deflection angle belongs to a discrete deflection angle set, and the discrete deflection angle set is set based on the grating period of the LCPG layer.
5. The space laser communication method based on the cascaded liquid crystal polarization grating device according to claim 1, wherein the first light splitting module splits the coarse directional light beam to obtain a coarse sampling light beam, and the first light splitting module is arranged between an emergent light path of the cascaded liquid crystal polarization grating module and an incident light path of the fine tracking deflection module.
6. The space laser communication method based on the cascaded liquid crystal polarization grating device, as set forth in claim 1, is characterized in that the second splitting module splits the precisely directed beam to obtain a precisely sampled beam, and comprises the second splitting module being disposed on an outgoing light path of the precisely tracking deflection module.
7. The method for spatial laser communication based on cascaded liquid crystal polarization grating device according to claim 1, wherein the fine tracking deflection module outputs the fine pointing light beam for continuous angle compensation of the coarse pointing light beam, and the method comprises a fast mirror and a fast mirror driver, wherein the fast mirror driver drives the fast mirror to perform continuous angle compensation based on a fast mirror driving signal.
8. The method for spatial laser communication based on cascaded liquid crystal polarization grating device according to claim 1, wherein the grating driving signal comprises: The grating driving signal is a multichannel voltage waveform signal, the grating driving signal comprises a first voltage waveform sub-signal and a second voltage waveform sub-signal, the first voltage waveform sub-signal is loaded on the plurality of electric control liquid crystal half wave plate layers, the second voltage waveform sub-signal is loaded on the plurality of liquid crystal polarization grating LCPG layers, the first voltage waveform sub-signal and the second voltage waveform sub-signal sequentially comprise a pre-emphasis voltage section, a steady-state voltage section and a reverse pre-emphasis voltage section when updating a state code, the voltage amplitude of the pre-emphasis voltage section is larger than that of the steady-state voltage section, and the voltage amplitude of the reverse pre-emphasis voltage section is larger than that of the steady-state voltage section.
9. The space laser communication method based on the cascaded liquid crystal polarization grating device according to claim 1, wherein the state codes are encoded by Gray codes, and the number of code bit transitions between adjacent state codes is 1.
10. The space laser communication system based on the cascading liquid crystal polarization grating device is characterized by comprising an optical antenna, a beam shrinking module, a cascading liquid crystal polarization grating module, a first light splitting module, a coarse tracking detector, a fine tracking deflection module, a second light splitting module, a fine tracking detector, a control module and a pointing monitoring module, wherein the space laser communication method based on the cascading liquid crystal polarization grating device is applied to the space laser communication system based on the cascading liquid crystal polarization grating device according to any one of claims 1-9; the first light splitting module is arranged between the emergent light path of the cascade liquid crystal polarization grating module and the incident light path of the fine tracking deflection module, and the second light splitting module is arranged on the emergent light path of the fine tracking deflection module; The coarse tracking detector is used for outputting a coarse tracking error signal to the control module based on the coarse sampling light beam obtained by the light splitting of the first light splitting module, and the fine tracking detector is used for outputting a fine tracking error signal to the control module and the pointing monitoring module based on the fine sampling light beam obtained by the light splitting of the second light splitting module; The control module is used for storing a state code mapping table, generating a state code based on the coarse tracking error signal and executing table look-up output, wherein the table look-up output is based on the state code and outputs a grating driving signal to the cascade liquid crystal polarization grating module in the state code mapping table; The control module is used for calculating a continuous compensation angle based on the fine tracking error signal, calculating the absolute value of the continuous compensation angle and outputting a fast mirror driving signal to the fine tracking deflection module, calculating the update amount of the state code based on the continuous compensation angle and updating the state code when the absolute value of the continuous compensation angle reaches the upper limit of the compensation angle of the fine tracking deflection module, resetting the continuous compensation angle to 0 angle, outputting the fast mirror driving signal to the fine tracking deflection module and executing table lookup output based on the update state code; The pointing monitoring module is used for calculating a pointing error amplitude based on the fine tracking error signal, triggering the control module to calculate a state code update amount based on the pointing error amplitude and update the state code when the pointing error amplitude is larger than a pointing error threshold value, resetting the continuous compensation angle to be 0 angle, outputting a fast mirror driving signal to the fine tracking deflection module, and executing table look-up output based on the updated state code.

Description

Space laser communication method and system based on cascade liquid crystal polarization grating device Technical Field The invention relates to the field of space laser communication, in particular to a space laser communication method and system based on a cascade liquid crystal polarization grating device. Background Spatial laser communication link establishment and maintenance typically relies on cooperative control of acquisition, coarse tracking and fine tracking. The coarse pointing link usually adopts a turntable, a cradle head or a mechanical scanning mechanism to realize large-scale pointing, and has the problems of limited inertia and response speed, limited service life and reliability, micro-vibration coupling and the like. The fine tracking link usually adopts fine tracking deflection modules such as a quick reflector and the like to realize high-bandwidth continuous angle compensation, but the fine tracking deflection module has limited compensation angle range, and when coarse pointing deviation is large or external disturbance is strong, the fine tracking deflection module easily reaches the upper limit of the compensation angle, so that the stability of a closed loop is reduced and even a chain is lost. To overcome the limitations of mechanical beam steering, the industry is beginning to explore non-mechanical beam deflection techniques based on electronically controlled non-devices. The liquid crystal phase regulating device, especially the liquid crystal polarization grating, has good application prospect. The device regulates the arrangement of liquid crystal molecules by changing an external electric field, so that the phase of incident light is modulated, the deflection of light beams is realized, and the device has the potential advantages of no inertia, flexible control, low power consumption and the like. However, when the method is used for directional control of space laser communication, a deterministic driving of discrete deflection states, a mapping relation between discrete states and control signals, unloading and coarse directional take-over during fine tracking compensation saturation, and a monitoring trigger mechanism of abnormal directional errors are needed to be solved, so that continuity and stability of a directional control process are ensured. Disclosure of Invention The present invention has been made to solve one of the above-mentioned problems occurring in the prior art. Specifically, the invention is realized by the following technical scheme: the space laser communication method based on the cascade liquid crystal polarization grating device comprises the following steps: step one, an optical antenna receives an incident beam, a beam shrinking module shrinks the incident beam to obtain a beam shrinking beam, and a cascade liquid crystal polarization grating module performs phase modulation on the beam shrinking beam based on an electric control liquid crystal phase and discretely deflects and outputs a coarse pointing beam; step two, the first beam splitting module splits the coarse directional beam to obtain a coarse sampling beam, and the coarse tracking detector outputs a coarse tracking error signal to the control module based on the coarse sampling beam; Third, the fine tracking deflection module outputs a fine pointing light beam through continuous angle compensation of the coarse pointing light beam, the second splitting module splits the fine pointing light beam to obtain a fine sampling light beam, and the fine tracking detector outputs a fine tracking error signal to the control module and the pointing monitoring module based on the fine sampling light beam; step four, the control module stores a state code mapping table, generates a state code based on the coarse tracking error signal and executes table look-up output, wherein the table look-up output is based on the state code to look up a table in the state code mapping table to output a grating driving signal to the cascade liquid crystal polarization grating module; Step five, the control module calculates a continuous compensation angle based on the fine tracking error signal and calculates a continuous compensation angle absolute value, outputs a fast-reflecting mirror driving signal to the fine tracking deflection module, and the continuous compensation angle absolute value reaches the upper limit of the compensation angle of the fine tracking deflection module; And step six, the pointing monitoring module calculates a pointing error amplitude based on the fine tracking error signal, when the pointing error amplitude is larger than a pointing error threshold, the control module calculates a state code update amount based on the pointing error amplitude and updates the state code, resets the continuous compensation angle to 0 angle and outputs a fast-reflection mirror driving signal to the fine tracking deflection module, and the control module performs table look-up output based on the upda