Laser communication system and method thereof

Abstract

The invention provides a laser communication system and method, and relates to the technical field of laser communication. The laser communication system comprises a first light beam transceiving device, a relay imaging device and a second light beam transceiving device, the first light beam transmitting-receiving device, the relay imaging device and the second light beam transmitting-receiving device are arranged along the light path propagation direction; the first light beam transceiving device comprises a light source and / or a receiver; under the condition that a first light beam receiving and transmitting device comprises a light source and a receiver and in the process that light beams are transmitted in the first direction, the first light beam receiving and transmitting device is used for collimating laser emitted by the light source, outputting parallel light and conducting deflection scanning on the parallel light to obtain deflected light beams; the relay imaging device is used for receiving the deflected light beam from the first light beam transceiving device and forming a first intermediate image plane; and the second light beam receiving and transmitting device is used for receiving the first intermediate image plane from the relay imaging device and transmitting the first intermediate image plane to a free space, so that stable and accurate laser communication is realized.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of laser communication, in particular to a laser communication system and a method thereof. BACKGROUND

[0002] Space laser communication relies on extremely narrow beams to transmit directly in the atmosphere or between stars, and naturally has the ability of high speed, free spectrum, anti-interception and anti-electromagnetic interference, and is therefore regarded as the preferred means of high-speed backbone link between star-ground and interstellar. Traditional systems generally use a "single alignment, point-to-point" link establishment mode: the terminal aligns the transceiver telescope with the cooperative node by means of a precise two-dimensional turntable or gimbal, and completes acquisition, tracking and alignment (ATP) to maintain communication. This mode has been fully verified to be feasible in scenarios with a small number of nodes, short task cycles and relatively stable orbits.

[0003] However, the existing method has the following disadvantages: narrow field of view, difficult to expand, large aperture of the telescope of the traditional terminal, beam divergence angle in the order of micro-radians, resulting in single alignment with only one target, if multiple satellites are to be connected simultaneously, multiple sets of independent terminals must be rotated or configured, the SWaP (size, weight and power) increases linearly with the number of nodes, and the "one satellite with multiple chains" requirement cannot be directly met; central obscuration and bulky structure, most coaxial Cassegrain or off-axis reflective optical paths require secondary mirrors, turning mirrors and coarse-fine two-stage ATP mechanisms, the optical path is folded multiple times, and the height dimension is "locked" above several hundred millimeters; at the same time, the secondary mirror and its support inevitably produce central obscuration, which not only loses the equivalent aperture, but also raises the sidelobe, reducing the receiving sensitivity; miniaturization and wide angle conflict, in order to obtain a capture range of ±10° or even several tens of degrees, the existing scheme either adds a wide-angle lens group in front of the telescope or uses a spherical whole window + multi-detector splicing, but both bring additional aberration, complex installation and adjustment and mass cost; the wide-angle lens group further lengthens the optical path, which directly conflicts with the "compressed height" goal. The multi-node synchronous communication mechanism is missing, even if a "one-to-many" field of view is achieved through multi-terminal splicing, each terminal still needs to be independently ATP, and the optical aperture, laser and detector cannot be shared, resulting in low resource reuse rate; and when multiple points are connected simultaneously, the same frequency beams interfere with each other inside the terminal, and there is a lack of efficient space-wavelength isolation means. Orbit disturbance and alignment load, the relative speed of low-orbit constellation is high, and the angular rate can reach dozens of milliseconds per second, the traditional "narrow beam + high gain" scheme requires high ATP bandwidth and frequent micro-movement of the execution mechanism, which causes significant mechanical wear and power consumption, and it is difficult to meet the >7-year long-life mission. SUMMARY Therefore, the purpose of the embodiments of the present application is to provide a laser communication system and a method thereof to improve the above-mentioned problems in the prior art.

[0004] In a first aspect, the embodiments of the present application provide a laser communication system, comprising: a first beam transceiver, a relay imaging device, and a second beam transceiver; the first beam transceiver, the relay imaging device, and the second beam transceiver are arranged along a light path propagation direction; the light path propagation direction is reversible; the first beam transceiver comprises a light source and / or a receiver; in the case that the first beam transceiver comprises the light source and the receiver, and during transmission of a light beam in a first direction: the first beam transceiver is configured to collimate laser light emitted by the light source and output parallel light, and deflect and scan the parallel light to obtain a deflected light beam; the relay imaging device is configured to receive the deflected light beam from the first beam transceiver and form a first intermediate image plane; the second beam transceiver is configured to receive the first intermediate image plane from the relay imaging device and emit it to free space; during transmission of a light beam in a second direction: the second beam transceiver is configured to receive a light beam from free space and transmit it to the relay imaging device; the relay imaging device is configured to relay the light beam from the second beam transceiver and form a second intermediate image plane; and the first beam transceiver is configured to couple the received scanned light beam to a target surface of the receiver.

[0005] In the above implementation process, the relay imaging device forms a first intermediate image plane and a second intermediate image plane in a bidirectional light path, respectively, so that the first beam transceiver can realize large field coverage under low-order deflection scanning conditions, and the received light beam is coupled to the target surface of the receiver after relay imaging and beam shrinking, which significantly reduces the dependence on high-precision tracking; at the same time, the first beam transceiver and the second beam transceiver are integrated for receiving and transmitting by using the reversible characteristics of the light path, which effectively compresses the volume, weight, and power consumption of the system.

[0006] Optionally, the first beam transceiver comprises a beam shaping module and a beam scanning module; the beam scanning module is optically connected to the relay imaging device; the beam shaping module is optically connected to the receiver or the light source; the beam scanning module is arranged between the beam shaping module and the relay imaging device, and is configured to change the propagation direction of a light beam; and the beam shaping module is configured to collimate a light beam emitted by the light source during transmission of the light beam in a first direction, or converge and couple a light beam from the beam scanning module to the receiver during transmission of the light beam in a second direction.

[0007] In the implementation process, the light beam shaping module and the light beam scanning module are arranged separately, the light beam scanning module only needs to complete small-angle deflection to send the collimated parallel light into the relay imaging device, thereby greatly reducing the inertia of the scanner; meanwhile, the light beam shaping module converges the received light beam, so that the image spot at the second intermediate image plane directly matches the target surface of the receiver, thereby further reducing the number of elements and the length of the optical path, and realizing a lightweight and low insertion loss bidirectional laser communication link.

[0008] Optionally, the light beam shaping module comprises: a first shaping element, a second shaping element, and a third shaping element; the first shaping element is configured to receive and initially collimate the laser emitted by the light source during transmission of the light beam in a first direction, or converge and couple the light beam from the second shaping element to the receiver during transmission of the light beam in a second direction; the second shaping element is configured to correct aberration and shape the light beam processed by the first shaping element during transmission of the light beam in the first direction, or correct aberration and shape the light beam processed by the third shaping element during transmission of the light beam in the second direction; and the third shaping element is configured to output the collimated parallel light to the light beam scanning module during transmission of the light beam in the first direction, or receive the parallel light from the light beam scanning module and start converging to the relay imaging device during transmission of the light beam in the second direction.

[0009] In the implementation process, the first shaping element, the second shaping element, and the third shaping element are cascaded along the optical path. On the light source side, the first shaping element initially collimates the divergent laser, the second shaping element corrects aberration and shapes the light beam, and the third shaping element outputs high-quality parallel light into the light beam scanning module, thereby ensuring the wavefront consistency and far-field energy concentration in the scanning field of view. On the receiving side, the third shaping element reversely receives the parallel light from the light beam scanning module, the second shaping element corrects aberration again, and the first shaping element finally couples the converging light spot to the target surface of the receiver, thereby realizing aberration balance and efficient coupling of the same set of optical elements in the forward and reverse directions, significantly reducing the number of lenses, shortening the axial size, and reducing the total insertion loss of the system.

[0010] Optionally, the first light beam transceiver device comprises at least one light beam scanning module.

[0011] In the implementation process, at least one light beam scanning module is configured in the first light beam transceiver device, so that the system can realize two-dimensional scanning by using single-stage or multi-stage deflection, without the need for an additional mechanical turntable to cover the target airspace. The light beam scanning module is directly located near the front focal plane of the relay imaging device, small-angle deflection is correspondingly enlarged to far-field large-angle deflection after relay imaging, thereby reducing the scanning driving power consumption and inertia while maintaining pointing accuracy and response speed, and further compressing the overall volume, weight, and power consumption.

[0012] Optionally, the first light beam transceiver device further comprises a light splitting plate; the light splitting plate is arranged between the relay imaging device and the light beam scanning module, and one light beam scanning module corresponds to at least one light splitting plate; the light splitting plate is configured to separate light beams of different wavelengths of the relay imaging device and guide them to the light beam scanning module or different light beam shaping modules.

[0013] In the above implementation process, by inserting a light splitting plate between the relay imaging device and the light beam scanning module, and ensuring that each light beam scanning module corresponds to at least one light splitting plate, the system can complete multiplexing at the intermediate image plane in the wavelength dimension at one time: when exiting, different wavelength collimated light beams enter the common relay imaging device after being combined by the same light splitting plate, reducing the rear-end optical repeated configuration; when receiving, the light splitting plate separates the multi-wavelength signals according to the wavelength, and guides them into the respective light beam shaping modules and receivers, realizing single-aperture multi-wavelength bidirectional communication. Thus, under the premise of maintaining the common optical path and common scanning architecture of the receiving / transmitting, the channel number can be linearly expanded by only adding the light splitting plate and the corresponding light beam shaping and scanning modules, without additional pointing mechanism, significantly reducing the volume, weight and alignment complexity of the multi-wavelength system.

[0014] Optionally, the second light beam transceiver device comprises a first mirror, a second mirror, a third mirror and a fourth mirror; the reflecting surface of the fourth mirror is a concave free-form surface; the reflecting surface of the third mirror is a convex free-form surface; the reflecting surface of the second mirror is a concave free-form surface; the reflecting surface of the first mirror is a plane; wherein the reflection angle of the fourth mirror to the third mirror is greater than the reflection angle of the third mirror to the second mirror; the reflection angle of the third mirror to the second mirror is greater than the reflection angle of the second mirror to the first mirror.

[0015] In the above implementation process, the second light beam transceiver device adopts a four-mirror folded light path of plane, concave, convex, concave, uses free-form surface to asymmetrically correct off-axis aberration, and realizes beam compression / expansion through the gradually decreasing reflection angles (fourth to third, third to second, second to first): the concave free-form surface fourth mirror first receives the wide beam from the free space at a large angle, preliminarily converges and reduces the incident height; the convex free-form surface third mirror then further compresses the light beam at a medium angle, while introducing negative aberration to balance the system spherical aberration; the concave free-form surface second mirror finely corrects the field curvature and distortion at a small angle; and finally, the plane first mirror outputs the quasi-telecentric light beam to the relay imaging device at the smallest folding angle. The gradually decreasing reflection angle design significantly reduces the mirror blocking and beam clipping, balances the large field of view and high image quality, and shortens the axial size under the same focal length, realizing a lightweight, large-aperture, non-blocking far-field receiving / transmitting interface.

[0016] Optionally, the relay imaging device comprises a first lens, a second lens, a third lens, a fourth lens and a fifth lens; the first lens is optically connected with the second beam transceiver; the other end of the first lens is optically connected with the second lens; the other end of the second lens is optically connected with the third lens; the other end of the third lens is optically connected with the fourth lens; the other end of the fourth lens is optically connected with the fifth lens; the other end of the fifth lens is optically connected with the first beam transceiver.

[0017] In the implementation process, the relay imaging device adopts a cascade structure, and the first lens, the second lens, the third lens, the fourth lens and the fifth lens are sequentially arranged along the optical path from the second beam transceiver to the first beam transceiver, forming a bidirectional shared relay imaging chain: the transmitting end, the first lens receives the wide-field parallel light beam from the second beam transceiver, and the light beam is continuously converged and aberration-corrected through the second lens and the third lens, forming a first intermediate image plane between the third lens and the fourth lens, and the fourth lens and the fifth lens collimate the intermediate image plane and output it to the first beam transceiver, realizing the pre-processing of the far-field light beam; the receiving end, the fifth lens receives the scanning light beam from the first beam transceiver, and the light beam is reversely converged through the fourth lens and the third lens, forming a second intermediate image plane between the third lens and the second lens, and the second lens and the first lens collimate the light beam and output it to the second beam transceiver, completing the compression and aberration balance of the far-field signal.

[0018] Optionally, the first lens is a meniscus lens, the second lens is a convex lens, the third lens is a double convex lens, the fourth lens is a double cemented lens, and the fifth lens is a meniscus lens.

[0019] In the implementation process, the five lenses of the relay imaging device adopt symmetrical power distribution: the first lens introduces negative power in the form of meniscus, expands the aperture of the incident light beam and preliminarily corrects the field curvature; the second lens provides positive power in the form of convex lens, forms a telephoto front group with the first lens, and shortens the total length of the system; the third lens adopts a double convex structure to bear the main positive power, and generates a near-axis focal point with low spherical aberration and low coma near the first intermediate image plane / second intermediate image plane; the fourth lens uses a double cemented lens to directly offset chromatic aberration and secondary spectrum through positive and negative power cementing; the fifth lens again provides negative power in the form of meniscus, symmetrically matches the first lens, balances distortion and Petzval sum, and makes the wavefront of the full field of view uniform and consistent.

[0020] In a second aspect, the embodiments of the present application provide a laser communication method, which is based on the laser communication system described above. The laser communication system comprises a first beam transceiver, a relay imaging device and a second beam transceiver. In the case that the first beam transceiver comprises the light source and the receiver, and in the process of transmitting the light beam along a first direction: the light beam transmitted by the first beam transceiver is collimated into parallel light, and the parallel light is deflected and scanned to obtain a deflected light beam; in the case of obtaining the deflected light beam, the relay imaging device receives the deflected light beam and forms a first intermediate image plane; in the case of obtaining the first intermediate image plane, the second beam transceiver receives the first intermediate image plane and emits it into a target field of view in free space at a predetermined beam divergence angle; in the process of transmitting the light beam along a second direction: the second beam transceiver receives the light beam from the target field of view in free space; in the case that the second beam transceiver receives the light beam from the target field of view in free space, the relay imaging device relays the received light beam and forms a second intermediate image plane; in the case of forming the second intermediate image plane, the first beam transceiver receives the second intermediate image plane from the relay imaging device and couples it to the target surface of the receiver.

[0021] In the above implementation process, in the emission stage, the first beam transceiver collimates the light source light beam into parallel light and completes deflection and scanning; the relay imaging device receives the deflected light beam and forms a first intermediate image plane; the second beam transceiver emits the first intermediate image plane into a target field of view in free space at a set beam divergence angle. In the receiving stage, the second beam transceiver captures the light beam from the target field of view in free space; the relay imaging device relays the captured light beam and forms a second intermediate image plane; the first beam transceiver couples the second intermediate image plane to the target surface of the receiver, and completes signal reception. Thus, bidirectional communication is realized by using the same optical path, the intermediate image plane reduces the scanning and tracking accuracy requirements, and the system is simple, light and reliable.

[0022] Optionally, the second beam transceiver comprises a first mirror, a second mirror, a third mirror and a fourth mirror; in the process of transmitting the light beam along a first direction: the light signal is processed by the first mirror, the second mirror, the third mirror and the fourth mirror in sequence, wherein: the first mirror is used for rough correction of aberration of the light beam from the relay imaging device; the second mirror is used for fine correction of aberration of the light beam processed by the first mirror; the third mirror is used for converging and collimating the light beam processed by the second mirror; and the fourth mirror is used for folding and emitting the light beam converged by the third mirror to free space.

[0023] In the implementation process, the outgoing light beam sequentially passes through the first mirror, the second mirror, the third mirror and the fourth mirror along the first direction to complete aberration correction and emission: the first mirror (plane) performs preliminary pointing correction and coarse correction on the light beam output by the relay imaging device; the second mirror (concave free-form surface) performs fine correction on the residual aberration to balance the spherical aberration and the coma; the third mirror (convex free-form surface) converges and collimates the light beam to control the beam divergence angle; and the fourth mirror (concave free-form surface) folds and emits the light beam to the free space to realize far-field coverage. The four mirrors are processed in stages, and the free-form surface is shared, which shortens the axial size while ensuring the wavefront quality of the outgoing light beam, and meets the requirements of light weight and high image quality.

[0024] Optionally, the second beam transceiver receives the first intermediate image plane and emits it to the target field of view in the free space at a predetermined beam divergence angle, including: controlling the scanning angle of the beam scanning module, and in the case that the deflected light beam passes through the relay imaging device and reaches the second beam transceiver, emitting it to the target field of view in the free space at a predetermined beam divergence angle.

[0025] In the implementation process, by controlling the scanning angle of the beam scanning module, the light beam processed by the relay imaging device and the first beam transceiver is emitted to the target field of view in the free space at a predetermined beam divergence angle, realizing the far-field coverage with controllable pointing.

[0026] Optionally, in the process of transmitting the light beam along the second direction: the optical signal sequentially passes through the fourth mirror, the third mirror, the second mirror and the first mirror, wherein: the fourth mirror is used to receive the light beam from the free space and fold to the third mirror; the third mirror performs preliminary collimation on the folded light beam, and the preliminary collimated light beam reaches the second mirror; the second mirror performs aberration pre-correction on the preliminary collimated light beam, and the pre-corrected light beam reaches the first mirror; and the first mirror performs main correction on the pre-corrected light beam and transmits it to the relay imaging device. In the implementation process, the receiving light beam is sequentially folded and aberration-corrected by the fourth mirror, the third mirror, the second mirror and the first mirror along the second direction, the fourth mirror (concave free-form surface) receives the free-space light beam and folds it, realizing large-aperture unobstructed incidence; the third mirror (convex free-form surface) preliminarily collimates the light beam, controlling the incidence angle and height; the second mirror (concave free-form surface) pre-corrects the aberration of the preliminarily collimated light beam, balancing the main spherical aberration and coma; the first mirror (plane) performs main correction on the residual aberration and outputs the telecentric light beam to the relay imaging device, ensuring that the subsequent relay imaging obtains a diffraction-limited wavefront. The four mirrors are processed in reverse and step by step, share the same set of free-form surface shapes, realize aberration correction and collimation of the receiving light path, and ensure high image quality and light weight under the condition of bidirectional common optical path of the system. BRIEF DESCRIPTION OF DRAWINGS

[0027] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments of the present application. It should be understood that the following drawings only show some embodiments of the present application, and therefore should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can also be obtained without creative labor on the basis of these drawings.

[0028] Figure 1 The first schematic diagram of the laser communication system provided by the embodiments of the present application; Figure 2 The second schematic diagram of the laser communication system provided by the embodiments of the present application; Figure 3 The third schematic diagram provided by the embodiments of the present application; Figure 4 The first flowchart of the laser communication method provided by the embodiments of the present application; Figure 5 The second flowchart of the laser communication method provided by the embodiments of the present application; Figure 6 The OTF modulus curve of the laser communication system provided by the embodiments of the present application; Figure 7 The spot diagram of the laser communication system provided by the embodiments of the present application.

[0029] Icons: 100-First beam transceiver; 101-Light source; 102-Receiver; 103-Beam splitter; 110-Beam shaping module; 111-First shaping element; 112-Second shaping element; 113-Third shaping element; 120-Beam scanning module; 200-Relay imaging device; 210-First lens; 220-Second lens; 230-Third lens; 240-Fourth lens; 250-Fifth lens; 300-Second beam transceiver; 310-Fourth reflector; 320-Third reflector; 330-Second reflector; 340-First reflector. Detailed Implementation

[0030] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of the embodiments of this application.

[0031] In a first aspect, embodiments of this application provide a laser communication system, please refer to... Figure 1 , Figure 1 This is a first schematic diagram of a laser communication system provided in an embodiment of this application.

[0032] The laser communication system includes: a first beam transceiver 100, a relay imaging device 200, and a second beam transceiver 300; the first beam transceiver 100, the relay imaging device 200, and the second beam transceiver 300 are arranged along the optical path propagation direction; wherein the optical path propagation direction is reversible; the first beam transceiver 100 includes a light source 101 and / or a receiver 102; when the first beam transceiver 100 includes a light source 101 and a receiver 102, and during the transmission of the beam along a first direction: the first beam transceiver 100 is used to collimate the laser emitted by the light source 101 and output parallel light, and to deflect and scan the parallel light to obtain... A deflected beam; a relay imaging device 200 is used to receive the deflected beam from the first beam transceiver 100 and form a first intermediate image plane; a second beam transceiver 300 is used to receive the first intermediate image plane from the relay imaging device 200 and transmit it into free space; during the transmission of the beam along the second direction: the second beam transceiver 300 is used to receive the beam from free space and transmit it to the relay imaging device 200; the relay imaging device 200 is used to relay the beam from the second beam transceiver 300 and form a second intermediate image plane; the first beam transceiver 100 is used to couple the received scanning beam to the target surface of the receiver 102.

[0033] In the above implementation process, the laser communication system comprises three main parts, arranged in optical path order: the first beam transceiver 100 includes a light source 101 for emitting laser light and / or a receiver 102 for detecting optical signals; that is, the first beam transceiver 100 integrates emission, collimation, deflection scanning, and reception functions. The core function of the relay imaging device 200 is imaging and relaying; it can form a clear intermediate image plane from one end of the beam and accurately transmit it to the other end. The second beam transceiver 300 is mainly responsible for interfacing with free space, emitting beams from inside the system into the air, or receiving beams from the air and guiding them into the system. The three are arranged sequentially along the optical path propagation direction, and this direction is reversible, meaning that the beam can be transmitted from the first end to the second end, and vice versa. This enables long-distance laser communication over thousands of kilometers within a wide field of view of ±15°. By using a built-in galvanometer or fast reflector instead of the coarse tracking mechanism of the traditional laser communication terminal, the aim is to overcome the problems of small field of view and large size of traditional laser communication, so as to realize omnidirectional laser communication between inter-satellite laser communication networks and thus improve the efficiency of satellite constellation construction.

[0034] In one embodiment of this application, assuming that the first beam transceiver 100 includes both a light source 101 and a receiver 102, the system's operation is as follows: Process 1: The beam propagates along the first direction, i.e., the transmission process; the first beam transceiver 100 emits laser light and converts the diverging laser light emitted by the light source 101 into parallel light. Then, the parallel light is deflected to control the beam's direction, aiming it at a distant communication target. The relay imaging device 200 receives the deflected scanning beam from the first device, forming a first intermediate image plane. This image plane can be understood as an "intermediate focal point" or "pupil" of the deflected beam, maintaining the beam's angle and position information. The second beam transceiver 300 receives the first intermediate image plane formed by the relay imaging device 200 and effectively transmits this image plane (and its beam) into free space, towards the distant target.

[0035] Step 2: The beam propagates along the second direction, i.e., the receiving process; the second beam transceiver 300 is used to receive the laser beam from space, receiving the beam transmitted from free space from a distant communication object. At this time, the relay imaging device 200 relays the beam received by the second device, forming a second intermediate image plane. This image plane corresponds to the first intermediate image plane during transmission. The first beam transceiver 100 receives the scanning beam from the relay imaging device 200, i.e., the second intermediate image plane, and efficiently couples the received optical signal to the target surface (such as on a photodetector) of the receiver 102, completing the conversion of optical signal to electrical signal.

[0036] Through the above workflow, the relay imaging device 200 forms an intermediate image plane, which can effectively isolate the aberration and mechanical vibration of the two optical elements, making the direction of the outgoing beam more stable, and improving the efficiency of the receiving end coupling. The first transceiver device is responsible for complex deflection scanning, while the relay imaging device 200 is responsible for stable transmission. This division of labor allows the design of the scanning system (such as MEMS mirror or liquid crystal optical phased array) to focus more on performance, rather than directly facing the external environment. Because the optical path is reversible, the system can be designed very symmetrically, simplifying optical design and analysis, and the second direction can be regarded as the complete inverse process of the first direction. Through precise relay imaging, the received weak signal light can be high-quality converged on the small target surface of the receiver 102, which is crucial for improving communication sensitivity and distance.

[0037] Optionally, the first light beam transceiver device 100 comprises: a light beam shaping module 110 and a light beam scanning module 120; the light beam scanning module 120 is optically connected with the relay imaging device 200; the light beam shaping module 110 is optically connected with the receiver 102 or the light source 101; the light beam scanning module 120 is arranged between the light beam shaping module 110 and the relay imaging device 200, and is used for changing the propagation direction of the light beam; the light beam shaping module 110 is used for collimating the light beam emitted by the light source 101 during the transmission of the light beam along the first direction, or converging and coupling the light beam from the light beam scanning module 120 to the receiver 102 during the transmission of the light beam along the second direction.

[0038] In the above implementation process, the light beam shaping module 110 is located at the starting end / terminal of the device, and is directly optically connected with the light source 101 or the receiver 102, and manages the divergence and convergence of the light beam. When transmitting (first direction), it acts as a collimator to convert the divergent laser emitted by the light source 101 into high-quality parallel light, which is the basis for realizing long-distance and low-loss transmission. When receiving (second direction), it acts as a converging mirror to converge and focus the parallel light (or small-angle light beam) from the light beam scanning module 120 onto the target surface of the receiver 102 to realize efficient photoelectric conversion. The light beam scanning module 120 is arranged between the light beam shaping module 110 and the relay imaging device 200, and controls the propagation direction of the light beam, that is, realizes deflection and scanning. Whether transmitting or receiving, it controls the pointing of the optical path by changing its optical properties (such as mirror angle or optical phase).

[0039] In an embodiment of the present application, it is assumed that the first light beam transceiver device 100 contains the light source 101 and the receiver 102 at the same time, and the working process of the system is as follows in combination with the newly added modules: Process one: the light beam transmits along the first direction, that is, the transmitting process; The beam shaping module 110 receives the divergent laser light emitted from the light source 101 and shapes it into parallel light. The beam scanning module 120 receives the parallel light from the beam shaping module 110 and changes its propagation direction according to the communication requirement, achieving pointing and scanning, at this time the output is a deflected beam. Thereafter, the deflected beam enters the relay imaging device 200, and the subsequent process remains unchanged.

[0040] Process two: the light beam is transmitted in the second direction, i.e. the receiving process; The beam scanning module 120 receives the light beam from the relay imaging device 200, which also carries angle information. The beam shaping module 110 receives the light beam from the beam scanning module 120 and efficiently converges it to a very small focal point, which falls on the target surface of the receiver 102, completing the capture of the optical signal and realizing efficient photoelectric conversion.

[0041] In the above implementation process, in the receiving path, the beam scanning module 120 precedes the beam shaping module 110. This means that no matter what angle the received light is incident from, it can be corrected and directed to the beam shaping module 110 after passing through the beam scanning module 120. The beam shaping module 110 then converges it to a fixed, tiny position on the target surface of the receiver 102. This avoids the problem of the focused light spot moving back and forth on the detector target surface (referred to as "spot wandering") due to the change of the incident angle, greatly improving the coupling efficiency and receiving sensitivity.

[0042] Optionally, this structure allows different types of beam pointing technologies (such as MEMS micromirror, liquid crystal optical phased array LCoS, voice coil motor driven mirror, etc.) to be selected as needed to match the beam shaping module 110, providing flexibility for the system.

[0043] Optionally, please refer to Figure 1 , refer to Figure 2 , Figure 2 The second schematic diagram of the laser communication system provided by the embodiment of the application.

[0044] The beam shaping module 110 comprises a first shaping element 111, a second shaping element 112, and a third shaping element 113; the first shaping element 111 is used to receive and initially collimate the laser emitted by the light source 101 during the transmission of the light beam along the first direction, or to converge and couple the light beam from the second shaping element 112 to the receiver 102 during the transmission of the light beam along the second direction; the second shaping element 112 is used to correct aberration and shape the light beam during the transmission of the light beam along the first direction after the treatment of the first shaping element 111, or to correct aberration and shape the light beam during the transmission of the light beam along the second direction after the treatment of the third shaping element 113; the third shaping element 113 is used to output the collimated parallel light to the beam scanning module 120 during the transmission of the light beam along the first direction, or to receive the parallel light from the beam scanning module 120 and start converging to the relay imaging device 200 during the transmission of the light beam along the second direction.

[0045] In an embodiment of the present application, assuming that the first beam transceiver 100 simultaneously contains the light source 101 and the receiver 102, combined with the first shaping element 111, the second shaping element 112, and the third shaping element 113, the working process of the system is as follows: Process one: the light beam transmits along the first direction, i.e. the emission process, which turns the laser emitted by the light source 101 into high-quality parallel light.

[0046] The first shaping element 111 receives and initially collimates the laser emitted by the light source 101, which is usually a positive lens or a lens group, responsible for collecting the large-angle divergent light emitted by the light source 101 (such as a laser diode) and initially correcting it to a less divergent or even nearly parallel light beam, which can be understood as coarse collimation. The second shaping element 112 is used for aberration correction and beam shaping to improve the quality of the light beam. The light beam that has been initially collimated by the first element usually still has aberrations (such as spherical aberration, coma, etc.) and the light intensity distribution may be uneven (such as Gaussian distribution). The second element corrects these aberrations and shapes the light spot into the required shape (such as circular, flat-top distribution) through special optical design (such as aspheric surface, diffractive optical element, etc.), thereby obtaining a high-quality light beam close to the diffraction limit. The third shaping element 113 receives the corrected and shaped light beam and finally ensures that it is emitted in the form of perfect parallel light, which is delivered to the subsequent beam pointing module.

[0047] Process two: the light beam is transmitted in the second direction, i.e. the receiving process, and the received parallel light is efficiently converged on the target surface of the receiver 102. Note that at this time the optical path is completely reversible, and the functions of the elements are also reversed. The third shaping element 113 receives the parallel light from the light beam pointing module and initiates convergence. The third shaping element 113 first receives the incident parallel light with angular information and begins to converge it. As in the emission process, the second shaping element 112 is used for aberration correction and beam shaping, which corrects the aberrations that can be introduced in the front optical system (including free-space transmission and relay imaging device 200), ensuring that the converged light spot is as close as possible to the ideal diffraction limit point, laying the foundation for the final efficient coupling. The first shaping element 111 receives the corrected convergent light beam and finally focuses it precisely on a very small light spot that falls exactly in the center of the sensitive target surface of the receiver 102 (such as an APD or PIN photodiode).

[0048] In the above implementation process, it is ensured that the optical path is symmetrical and optimized in both directions. The same optical system used to produce a perfect light beam in emission can also provide perfect focusing in reception. Through aberration correction by the second element, the signal light can be converged into a smaller and sharper focal point in reception, greatly improving the efficiency of coupling to the target surface of the micro receiver 102, thereby directly improving the reception sensitivity and maximum communication distance of the system.

[0049] In an embodiment of the present application, the first shaping element 111, the second shaping element 112 and the third shaping element 113 are meniscus lenses, and the diameter of the collimated light beam is 48-50 mm. The center distance between the first shaping element 111 and the second shaping element 112 is 59.5-61.5 mm, and the center distance between the second shaping element 112 and the third shaping element 113 is 49.5-50.5 mm.

[0050] Optionally, please refer to Figure 2 , refer to Figure 3 , Figure 3 the third schematic diagram of the laser communication system provided by the embodiment of the present application.

[0051] The first light beam transceiver device 100 at least includes one light beam scanning module 120.

[0052] In the above implementation process, in free space laser communication, the two parties of communication can be in a high-speed relative motion state (such as between satellites, between satellites and ground stations). The core role of the beam scanning module 120 is to overcome this relative motion and achieve and maintain optical alignment. Before the communication starts, the system needs to scan the transmission beacon light in an uncertain spatial range to find and cover the position of the opposite receiving end. Once the initial connection is established, the beam scanning module 120 will make fine adjustments to accurately align the communication beam to the opposite side. During the communication process, the scanning module needs to real-time and dynamically fine-tune the beam direction to continuously lock the moving target and compensate for platform vibration and orbit changes. From the optical function, the beam scanning module 120 controls the propagation direction of the light beam by changing its optical state (such as the physical angle of the mirror or the phase distribution of the optical phased array). In the transmission path, the collimated parallel light from the beam forming module 110 is deflected to the correct exit angle, so that it can pass through the relay imaging device 200 and the second beam transceiver device 300 to the target. In the receiving path, the signal light incident from a certain angle and transmitted through the relay imaging device 200 is correctly guided to the receiving light path and finally coupled to the receiver 102.

[0053] In an embodiment of the present application, taking a fast mirror as an example, when the scanning angle is 45°, the corresponding central 0 field of view is emitted, when the scanning angle is 38°, the 15° field of view is emitted, and the maximum communication distance of the laser communication system is 1500km, and the fiber coupling efficiency is greater than 50%.

[0054] The link margin calculation of space laser communication is calculated by the following formula:

[0055] Wherein, is the received power of the probe; is the transmission power of the light source 101; is the efficiency of the transceiver optical unit; L r is the space transmission loss, and its expression is: , wherein is the receiving aperture, is the laser beam divergence angle, is the link distance; is the power loss caused by the channel; is PAT the power loss caused by the alignment mismatch; is the receiving optical system efficiency.

[0056] Further, based on the link calculation formula, the 1500km laser communication link is calculated, and the calculation result is as follows:

[0057] The laser communication system provided by the embodiment of the application adopts a free-form surface design to compensate for various aberrations caused by the tilting of the mirror, and the image plane size of the off-axis reflective optical antenna is equal to the image plane size of the relay system. According to the link calculation result, the entrance pupil diameter is 80 mm, and the focal length is 350 mm.

[0058] Optionally, the first beam transceiver device 100 further comprises a beam splitter 103; the beam splitter 103 is arranged between the relay imaging device 200 and the beam scanning module 120, and one beam scanning module 120 corresponds to at least one beam splitter 103; the beam splitter 103 is configured to separate the beams of different wavelengths of the relay imaging device 200 and guide the beams to the beam scanning module 120 or different beam forming modules 110.

[0059] In the above implementation process, the beam splitter 103 transmits the light of a specific wavelength and reflects the light of another specific wavelength, and the core capability is to filter and route the beams based on the wavelengths. By separating the light of different wavelengths, the system can process multiple independent communication channels or functions at the same time.

[0060] In one embodiment of the application, the system uses two wavelengths, (e.g., 1550 nm) for transmission, (e.g., 1064 nm) for reception. The transmission path (first direction), the beam from the beam scanning module 120 is incident on the beam splitter 103, the beam splitter 103 reflects and redirects it, and the beam is transmitted through the relay imaging device 200. The reception path (second direction), the beam from the outside passes through the relay imaging device 200 and reaches the beam splitter 103, the beam splitter 103 transmits and allows it to pass directly and be guided to the receiving optical path. In this way, the transmission and reception work simultaneously and do not interfere with each other, share the same main optical aperture (relay imaging device 200 and second beam transceiver device 300), and greatly simplify the terminal structure.

[0061] Optionally, the system can use multiple beam splitters 103 to form a filter network, separate three or more wavelengths, and thus establish multiple parallel communication links, multiply the communication capacity, and allow the system to integrate multiple independent transceiver units as needed, with each unit responsible for a specific wavelength and task, enhancing the flexibility and scalability of the system.

[0062] Optionally, the second light beam transceiver 300 comprises a first mirror 340, a second mirror 330, a third mirror 320 and a fourth mirror 310; the reflecting surface of the fourth mirror 310 is a concave free-form surface; the reflecting surface of the third mirror 320 is a convex free-form surface; the reflecting surface of the second mirror 330 is a concave free-form surface; the reflecting surface of the first mirror 340 is a plane; wherein the reflecting angle of the fourth mirror 310 to the third mirror 320 is greater than the reflecting angle of the third mirror 320 to the second mirror 330; the reflecting angle of the third mirror 320 to the second mirror 330 is greater than the reflecting angle of the second mirror 330 to the first mirror 340.

[0063] In the above implementation process, the first mirror 340 is a plane mirror, mainly serving as light path folding and final steering. As the last mirror, it steers the light beam from the second mirror 330 to a specific angle, and finally to free space; its plane design does not change the convergence or divergence characteristics of the light beam, only changes the direction, making the system layout more flexible, and the direction of the final outgoing light can be easily adjusted to adapt to different installation platforms.

[0064] In the above implementation process, the second mirror 330 is a concave free-form surface, which serves as the main mirror and has the ability to converge light beams. The second mirror 330 is the main light power contributor of the system, which determines the basic focal length and aperture of the system, and its purpose is to correct aberrations such as coma and astigmatism generated by the entire system (especially when used off-axis).

[0065] In the above implementation process, the third mirror 320 is a convex free-form surface, which serves as a secondary mirror and usually forms a Cassegrain or Gregorian mirror group with the main mirror (the second mirror 330). The third mirror 320, as a convex mirror, serves to expand the beam or along the long focal length, and also uses a free-form surface to work with the main mirror to further correct aberrations.

[0066] In the above implementation process, the fourth mirror 310 is a concave free-form surface, which is the first mirror in the first direction of the light path and directly receives the light beam from the relay imaging device 200. Its concave surface starts to preliminarily converge and control the light beam. The presence of the fourth mirror 310 allows the light path to be folded for the second time and provides additional degrees of freedom for further aberration correction.

[0067] In the implementation process, the reflection angles of the fourth mirror 310 to the third mirror 320 are greater than the reflection angles of the third mirror 320 to the second mirror 330, which are greater than the reflection angles of the second mirror 330 to the first mirror 340. Taking the first direction as an example, this is a process of expanding the light path. The propagation of the light beam inside the system is gradually from a compact and large-angle folded state to a more gentle and ready-to-exit state. It can be ensured that all mirrors do not block the incident or outgoing light beam, realizing an unobstructed aperture, which is the key to obtaining a high-quality wavefront and a clear light beam. At the same time, the entire telescope system can be made very compact while ensuring a long enough equivalent focal length and a large aperture. In addition, different reflection angles will produce different aberrations, and through this gradual change, free-form surfaces can be used to better balance and correct these aberrations.

[0068] In an embodiment of the present application, the field of view angle that the second light beam transceiver device 300 can realize is , the half image height is , the divergence angle is The specific indicators are as follows:

[0069] Optionally, the relay imaging device 200 comprises a first lens 210, a second lens 220, a third lens 230, a fourth lens 240, and a fifth lens 250; the first lens 210 is optically connected with the second light beam transceiver device 300; the other end of the first lens 210 is optically connected with the second lens 220; the other end of the second lens 220 is optically connected with the third lens 230; the other end of the third lens 230 is optically connected with the fourth lens 240; the other end of the fourth lens 240 is optically connected with the fifth lens 250; and the other end of the fifth lens 250 is optically connected with the first light beam transceiver device 100.

[0070] In the implementation process, the five lenses provide a large number of degrees of freedom (curvature, thickness, material, spacing, etc.), which can finely correct various monochromatic aberrations such as spherical aberration, coma, astigmatism, field curvature, and distortion, and ensure that the quality of the transmitted light beam wavefront approaches the diffraction limit. This is crucial for maintaining the quality of the laser beam and efficient coupling. Through complex settings, the system can be telecentric in both the object and image planes, which maximizes the reduction of focusing errors.

[0071] Optionally, the first lens 210 is a meniscus lens, the second lens 220 is a convex lens, the third lens 230 is a double convex lens, the fourth lens 240 is a double cemented lens, and the fifth lens 250 is a meniscus lens.

[0072] In the above implementation process, the first lens 210 is a meniscus lens, which is usually placed near the stop (or system aperture pupil). Its main role is to correct the field curvature and astigmatism of the system to a large extent. The meniscus lens lays the foundation for the correction of subsequent lenses by introducing aberrations of opposite signs. As the first lens, it first contacts the light beam from the second beam transceiver 300, and its meniscus shape helps to smooth the incidence angle of the light rays and reduce high-order aberrations. The second lens 220 is a convex lens, which provides a major positive power and undertakes most of the converging light rays' ability (positive power) of the entire relay system. It cooperates with the first meniscus lens to form an intermediate image plane. At the same time, it also produces certain spherical and coma aberrations, which need to be corrected by subsequent lenses. The third lens 230 is a biconvex lens. The biconvex lens is a powerful positive lens. It further contributes to the power and helps to control the focal length of the system. Its symmetrical or nearly symmetrical design helps to reduce distortion and ensure accurate reproduction of object shape. In the optical path, it is usually located near the intermediate image plane and is responsible for guiding the light beam to the correct path and working in cooperation with the front and rear lenses to balance the spherical and coma aberrations. The fourth lens 240 is a doublet lens, which is composed of two lenses made of different materials (for example, one is crown glass and the other is flint glass). It can correct the axial chromatic aberration and the magnification chromatic aberration by taking advantage of the difference in dispersion characteristics of different glasses. Even if laser communication mainly uses monochromatic light, if the system needs to handle different wavelengths of beacon light and communication light (such as 808nm beacon light and 1550nm communication light) at the same time, chromatic aberration correction is crucial. Moreover, it can also further finely correct residual spherical aberration. The fifth lens 250 is also a meniscus lens, which is used as the last lens to further flatten the image field and ensure that the final image plane (i.e. the plane where the beam scanning module 120 or the receiver 102 is located) is flat. At the same time, its shape can well control the angle of the chief ray, which is the key to realizing the design of the image telecentricity. Image telecentricity means that the chief ray is parallel to the optical axis in the image plane, which can ensure that the light spot focused on the target surface of the receiver 102 does not move when the beam scanning module 120 is deflected, greatly improving the receiving coupling efficiency.

[0073] In an embodiment of the present application, the specific indicators of the relay imaging device 200 are shown in the following table:

[0074] In a second aspect, the embodiments of the present application provide a laser communication method, please refer to Figure 4 and Figure 5 , Figure 4 the first flowchart of the laser communication method provided by the embodiments of the present application, Figure 5 the second flowchart of the laser communication method provided by the embodiments of the present application.

[0075] The laser communication method is based on the laser communication system described above; the laser communication system comprises a first beam transceiver device 100, a relay imaging device 200 and a second beam transceiver device 300; in the case where the first beam transceiver device 100 comprises a light source 101 and a receiver 102, and in the process of transmitting the light beam along a first direction: the light beam transmitted by the first beam transceiver device 100 is collimated into parallel light, and the parallel light is deflected and scanned to obtain a deflected light beam; in the case where the deflected light beam is obtained, the relay imaging device 200 receives the deflected light beam and forms a first intermediate image plane; in the case where the first intermediate image plane is obtained, the second beam transceiver device 300 receives the first intermediate image plane and emits it into a target field of view in free space at a predetermined beam divergence angle; in the process of transmitting the light beam along a second direction: the second beam transceiver device 300 receives the light beam from the target field of view in free space; in the case where the second beam transceiver device 300 receives the light beam from the target field of view in free space, the received light beam is relayed by the relay imaging device 200 and a second intermediate image plane is formed; in the case where the second intermediate image plane is formed, the first beam transceiver device 100 receives the second intermediate image plane from the relay imaging device 200 and couples it to the target surface of the receiver 102.

[0076] In the above implementation process, flow one: the light beam is transmitted along a first direction, and the laser communication system is used for transmitting signals. The purpose of this process is to convert the local electrical signal (drive the light source 101) into an optical signal and accurately transmit it to the remote target in free space. The divergent light emitted by the light source 101 (such as a laser diode) is collimated into high-quality parallel light by the beam shaping module 110 (three shaping elements). The parallel light is transmitted to the beam scanning module 120, which dynamically deflects the light beam according to the control instruction, so that it points to the intended direction. The deflected light beam from the beam scanning module 120 enters the relay imaging device 200 (five lens groups). One of the core functions of this device is to form a first intermediate image plane, which optically isolates aberrations, determines the field of view and provides a reference point for the relayed light beam. The light beam output by the relay device is received by the second beam transceiver device 300 (four mirror system). This device, as the main telescope, finally emits the light beam at a predetermined beam divergence angle. If the beam divergence angle is too small, it is extremely difficult to align and prone to link interruption due to jitter; if the beam divergence angle is too large, the energy is dispersed, and the transmission distance and speed are limited. The target field of view indicates the spatial range that the light beam needs to cover, which corresponds to the deflection range of the scanning module.

[0077] Process two: the light beam is transmitted along the second direction, and the laser communication system is used to receive the signal, the purpose of this process is to capture the weak light signal from the remote target and convert it back to the local electrical signal efficiently. As the second beam transceiver device 300 of the main telescope, it collects the extremely weak light signal from the remote target with its large aperture, and its target field of view defines the spatial angular range in which it can receive the signal. The captured light beam is transmitted back to the system through the relay imaging device 200, which also forms a second intermediate image plane, ensuring that the light beam is relayed with high quality and correcting any aberrations that may exist. The light beam scanning module 120 receives the light beam from the relay device. Since the optical path is reversible, it now functions as a symmetrical reverse deflection. The light beam then enters the light beam shaping module 110, which now acts as a converging mirror, precisely focusing and coupling the light beam onto the tiny target surface of the receiver 102 (such as a photodiode), which converts the light signal into an electrical signal for subsequent circuit demodulation and decoding.

[0078] Optionally, the second beam transceiver device 300 comprises: a first mirror 340, a second mirror 330, a third mirror 320, and a fourth mirror 310; during the process of transmitting the light beam along the first direction: the light signal is processed by the first mirror 340, the second mirror 330, the third mirror 320, and the fourth mirror 310 in turn, wherein: the first mirror 340 is used to perform coarse correction of aberrations of the light beam from the relay imaging device 200; the second mirror 330 is used to perform fine correction of aberrations of the light beam processed by the first mirror 340; the third mirror 320 is used to converge and collimate the light beam processed by the second mirror 330; and the fourth mirror 310 is used to fold and emit the light beam converged by the third mirror 320 to free space.

[0079] In the above implementation process, the function of each mirror is single and clear, and this decoupling allows independent optimization of each function. The complex aberration correction task is assigned to different elements, following the principle of coarse first and fine second, avoiding the difficulty of a single optical surface bearing too much correction task and introducing high-level aberrations, thereby achieving a globally optimal aberration balance. Through this division of labor, long equivalent focal length, large aperture and high imaging quality can be achieved in a very compact physical space through the folding of the multi-mirror optical path and precise aberration control.

[0080] Optionally, the second beam transceiver device 300 receives the first intermediate image plane and emits it into the target field of view in free space with a predetermined beam divergence angle, comprising: controlling the scanning angle of the light beam scanning module 120, and in the case of deflecting the light beam through the relay imaging device 200 and reaching the second beam transceiver device 300, emitting it into the target field of view in free space with a predetermined beam divergence angle.

[0081] In the above implementation process, the relay imaging device 200 is a high-quality imaging system, which forms an object image conjugate relationship between the position (system pupil) of the beam scanning module 120 and the exit aperture of the second beam transceiver device 300. This means that the angular deflection of the scanning module will be transmitted and amplified in a highly linear and deterministic manner, ultimately converted into a spatial pointing change of the exit beam of the second beam transceiver device 300. The entire optical path system is like a fixed function, the input is the deflection angle of the scanning module, and the output is the pointing of the exit beam. The beam divergence angle is mainly determined by the focal length of the optical system and the aperture of the incident beam. The beam shaping module 110 and the relay imaging device 200 jointly determine the beam divergence angle of the transmitted beam and fix it at an optimal value. The deflection of the beam scanning module 120 only changes the direction of the beam, but does not change its beam divergence angle.

[0082] Optionally, wherein, during the transmission of the light beam along the second direction: the optical signal is processed in sequence by the fourth mirror 310, the third mirror 320, the second mirror 330 and the first mirror 340, wherein: the fourth mirror 310 is used to receive the light beam from the free space and fold to the third mirror 320; the third mirror 320 performs preliminary collimation on the folded light beam, and the preliminary collimated light beam is transmitted to the second mirror 330; the second mirror 330 performs aberration pre-correction on the preliminary collimated light beam, and the pre-corrected light beam is transmitted to the first mirror 340; the first mirror 340 performs main correction of aberration on the pre-corrected light beam and transmits it to the relay imaging device 200. In the above implementation process, the beam path is transmitted from the free space to the fourth mirror 310, the fourth mirror 310 captures the incident light beam from the free space and changes its propagation direction, guiding it to the third mirror 320, the third mirror 320 converts the divergent light beam from the fourth mirror into a nearly parallel light beam, and transmits the parallel light beam to the second mirror 330, the second mirror 330 compensates part of the optical aberration (such as spherical aberration, coma, etc.) in advance, and transmits the light beam to the first mirror 340, and the first mirror 340 transmits to the relay imaging device 200.

[0083] Please refer to Figure 6 , Figure 6The OTF modulus curve of the laser communication system provided in this application embodiment; the horizontal axis (spatial frequency, unit: period / mm) represents the "density of detail" in the image, the larger the value, the finer the detail (for example, 100 periods / mm means there are 100 alternating black and white lines per millimeter). The vertical axis (OTF modulus) represents the optical system's ability to transmit "contrast" at the corresponding spatial frequency, with a value ranging from 0 to 1. The closer the modulus is to 1, the better the system transmits contrast at that frequency; when the modulus is 0, the system cannot transmit the details at that frequency. The downward trend of the curve reflects that the lower the resolution limit spatial frequency of the optical system (the coarser the detail), the closer the OTF modulus is to 1, and the more lossless the system can transmit contrast (such as large object outlines); as the spatial frequency increases (the finer the detail), the OTF modulus gradually decreases, and when the modulus approaches 0, the corresponding spatial frequency is the system's cutoff frequency (around 120 periods / mm in this figure) - details beyond this frequency cannot be distinguished by the system.

[0084] Please see Figure 7 , Figure 7 A dot diagram illustrating the laser communication system provided in the embodiments of this application. Field of view Field of view and Optical quality of the field of view. The dense points in the diagram are the set of intersections of light rays on the image plane after passing through the optical system. The more concentrated the distribution of points, the sharper the image formed by the optical system, and the smaller the aberrations (such as spherical aberration, coma, astigmatism, etc.); the more dispersed the distribution of points, the greater the aberrations, and the blurrier the image.

[0085] In summary, this application provides a laser communication system and method, relating to the field of laser communication technology. The laser communication system includes: a first beam transceiver 100, a relay imaging device 200, and a second beam transceiver 300; the first beam transceiver 100, the relay imaging device 200, and the second beam transceiver 300 are arranged along the optical path propagation direction; the first beam transceiver 100 includes a light source 101 and / or a receiver 102; when the first beam transceiver 100 includes a light source 101 and a receiver 102, and during the transmission of the beam along a first direction: the first beam transceiver 100 collimates the laser emitted by the light source 101 to output parallel light, and deflects and scans the parallel light to obtain a deflected beam; the relay imaging device 200 receives the deflected beam from the first beam transceiver 100 and forms a first intermediate image plane; the second beam transceiver 300 receives the first intermediate image plane from the relay imaging device 200 and transmits it into free space, achieving stable and precise laser communication.

[0086] In several embodiments provided in the present application, it should be understood that the disclosed apparatus can also be implemented by other means. The apparatus embodiments described above are only illustrative, for example, the block diagram in the accompanying drawings shows the possible implementation architecture, function and operation of the apparatus according to the embodiments of the present application. It should also be noted that in some alternative implementation manners, the functions labeled in the blocks can also occur in different order from that labeled in the accompanying drawings. For example, two consecutive blocks can actually be executed substantially in parallel, and they can also be executed in reverse order depending on the functions involved. It should also be noted that each block in the block diagram, and the combination of the block diagram, can be implemented by a dedicated hardware-based system performing the specified functions or actions, or can be implemented by a combination of dedicated hardware and computer instructions.

[0087] In addition, each functional module in the embodiments of the present application can be integrated together to form an independent part, or each module can exist independently, or two or more modules can be integrated to form an independent part.

[0088] The above only describes the embodiments of the present application and does not limit the protection scope of the present application. For those skilled in the art, the present application can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application. It should be noted that similar reference numerals and letters represent similar items in the following drawings, so once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings.

[0089] The above only describes the embodiments of the present application and does not limit the protection scope of the present application. For those skilled in the art, the present application can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application. It should be noted that similar reference numerals and letters represent similar items in the following drawings, so once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings.

[0090] It should be noted that in this paper, relationship terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between the entities or operations. Moreover, the terms "include", "contain" or any other variant thereof are intended to cover non-exclusive inclusion, so that the process, method, article or device including a series of elements not only includes those elements, but also includes other elements not explicitly listed or inherent to such process, method, article or device. Without more limitation, the elements defined by the statement "include" do not exclude the presence of other identical elements in the process, method, article or device including the elements.

Claims

1. A laser communication system, characterized in that, The laser communication system includes: a first beam transceiver, a relay imaging device, and a second beam transceiver. The first beam transceiver, the relay imaging device, and the second beam transceiver are arranged along the optical path propagation direction; wherein the optical path propagation direction is reversible; The first beam transceiver includes a light source and / or a receiver; When the first beam transceiver includes the light source and the receiver, and during the transmission of the beam along the first direction: The first beam transceiver is used to collimate the laser emitted by the light source and output parallel light, and to deflect and scan the parallel light to obtain a deflected beam. The relay imaging device is used to receive the deflected beam from the first beam transceiver and form a first intermediate image plane; The second beam transceiver is used to receive the first intermediate image plane from the relay imaging device and transmit it into free space; During the propagation of the light beam along the second direction: The second beam transceiver is used to receive beams from free space and transmit them to the relay imaging device; The relay imaging device is used to relay the beam from the second beam transceiver device and form a second intermediate image plane. The first beam transceiver is used to couple the received scanning beam to the receiver target surface.

2. The laser communication system according to claim 1, characterized in that, The first beam transceiver includes: a beam shaping module and a beam scanning module; The beam scanning module is optically connected to the relay imaging device; the beam shaping module is optically connected to the receiver or the light source. The beam scanning module is disposed between the beam shaping module and the relay imaging device, and is used to change the propagation direction of the beam; The beam shaping module is used to collimate the beam emitted by the light source during the transmission of the beam along the first direction, or to converge and couple the beam from the beam scanning module to the receiver during the transmission of the beam along the second direction.

3. The laser communication system according to claim 2, characterized in that, The beam shaping module includes: a first shaping element, a second shaping element, and a third shaping element; The first shaping element is used to receive and initially collimate the laser emitted by the light source during the transmission of the light beam along the first direction, or to converge and couple the light beam from the second shaping element to the receiver during the transmission of the light beam along the second direction. The second shaping element is used to perform aberration correction and beam shaping on the beam processed by the first shaping element during the transmission of the beam along the first direction; or to perform aberration correction and beam shaping on the beam processed by the third shaping element during the transmission of the beam along the second direction. The third shaping element is used to output collimated parallel light to the beam scanning module during the transmission of the beam along the first direction, or to receive parallel light from the beam scanning module and initiate convergence to the relay imaging device during the transmission of the beam along the second direction.

4. The laser communication system according to claim 2, characterized in that, The first beam transceiver also includes: a beam splitter; The beam splitter is disposed between the relay imaging device and the beam scanning module, and each beam scanning module corresponds to at least one beam splitter; The beam splitter is configured to separate beams of different wavelengths from those of the relay imaging device and guide them to the beam scanning module or different beam shaping modules.

5. The laser communication system according to claim 1, characterized in that, The second beam transceiver includes: First reflecting mirror, second reflecting mirror, third reflecting mirror, and fourth reflecting mirror; The fourth reflecting mirror has a concave freeform surface as its reflecting surface; the third reflecting mirror has a convex freeform surface as its reflecting surface; the second reflecting mirror has a concave freeform surface as its reflecting surface; and the first reflecting mirror has a flat surface as its reflecting surface. Wherein, the reflection angle from the fourth reflector to the third reflector is greater than the reflection angle from the third reflector to the second reflector; and the reflection angle from the third reflector to the second reflector is greater than the reflection angle from the second reflector to the first reflector.

6. The laser communication system according to claim 1, characterized in that, The relay imaging device includes: a first lens, a second lens, a third lens, a fourth lens, and a fifth lens; The first lens is optically connected to the second beam transceiver; the other end of the first lens is optically connected to the second lens. The other end of the second lens is optically connected to the third lens; the other end of the third lens is optically connected to the fourth lens. The other end of the fourth lens is optically connected to the fifth lens; the other end of the fifth lens is optically connected to the first beam transceiver.

7. A laser communication method, characterized in that, The laser communication method is based on the laser communication system according to any one of claims 1 to 6; the laser communication system includes: a first beam transceiver, a relay imaging device, and a second beam transceiver. When the first beam transceiver includes the light source and the receiver, and during the transmission of the beam along the first direction: The beam transmitted by the first beam transceiver is collimated into parallel light, and the parallel light is deflected and scanned to obtain a deflected beam. When the deflected beam is obtained, the relay imaging device receives the deflected beam and forms a first intermediate image plane; In the case of obtaining the first intermediate image plane, the second beam transceiver receives the first intermediate image plane and transmits it into the target field of view in free space at a predetermined beam divergence angle. During the propagation of the light beam along the second direction: The second beam transceiver receives beams from within the field of view of a target in free space; When the second beam transceiver receives a beam from the field of view of the target in free space, the received beam is relayed through the relay imaging device to form a second intermediate image plane. In the case of forming the second intermediate image plane, the first beam transceiver receives the second intermediate image plane from the relay imaging device and couples it to the target surface of the receiver.

8. The method according to claim 7, characterized in that, The second beam transceiver includes: a first reflector, a second reflector, a third reflector, and a fourth reflector; During the propagation of the light beam along the first direction: The optical signal is processed sequentially by the first reflector, the second reflector, the third reflector, and the fourth reflector, wherein: The first reflector is used to perform coarse aberration correction on the beam from the relay imaging device; The second mirror is used to perform fine aberration correction on the beam processed by the first mirror; The third reflecting mirror is used to converge and collimate the light beam processed by the second reflecting mirror; The fourth reflector is used to refract the light beam that has been focused by the third reflector and emit it into free space.

9. The method according to claim 8, characterized in that, in, During the propagation of the light beam along the second direction: The optical signal is processed sequentially by the fourth, third, second, and first reflecting mirrors, wherein: The fourth reflector is used to receive light beams from free space and refract them to the third reflector; The folded beam from the third reflecting mirror is initially collimated, and the initially collimated beam is then directed to the second reflecting mirror. The second mirror performs aberration pre-correction on the initially collimated beam, and the pre-corrected beam is then sent to the first mirror. The first reflecting mirror performs aberration correction on the pre-corrected beam and transmits it to the relay imaging device.

10. The method according to claim 7, characterized in that, The second beam transceiver receives the first intermediate image plane and transmits it into the target field of view in free space at a predetermined beam divergence angle, including: The scanning angle of the beam scanning module is controlled so that, when the deflected beam passes through the relay imaging device and reaches the second beam transceiver device, it is emitted into the target field of view in free space with a predetermined beam divergence angle.

Images