Beacon transmission branch of air-to-ground laser communication optical system

Abstract

The present application discloses a beacon transmission branch of an air-to-ground laser communication optical system. The beacon transmission branch of the air-to-ground laser communication optical system includes a beacon laser transmission light source and a lens group; wherein the lens group includes a first plano-convex cylindrical lens and a second plano-convex cylindrical lens coaxially arranged in sequence along the incident direction of the light, the first plano-convex cylindrical lens has a positive optical focal length, and the second plano-convex cylindrical lens has a positive optical focal length; the distance between the first plano-convex cylindrical lens and the second plano-convex cylindrical lens is adjustable, and during the process of adjusting the distance between the first plano-convex cylindrical lens and the second plano-convex cylindrical lens, the light beam divergence angle in the horizontal direction of the beacon transmission branch of the air-to-ground laser communication optical system is maintained at 4°. In this way, the air-to-ground laser communication optical system can change the light beam divergence angle of the beacon transmission branch of the air-to-ground laser communication optical system according to different link distance conditions, effectively improving the aiming and capture efficiency.

Description

Technical Field

[0001] The present application relates to a beacon transmission branch, and in particular to a beacon transmission branch of an air-to-ground laser communication optical system. Background Art

[0002] With the development of wireless laser communication technology, air-to-ground laser communication has emerged. Wireless laser communication has the characteristics of large bandwidth, anti-interference and security. Air-to-ground laser communication refers to the technology of using laser to transmit data between the terminal of the ground station (for example, the vehicle-mounted terminal) and the terminal of the aerial platform. Air-to-ground laser communication has the advantages of high speed, low latency and strong anti-interference ability, and is suitable for occasions requiring high bandwidth and secure communication. Wireless laser communication applied to vehicle-mounted terminals is conducive to enhancing communication guarantee capabilities and reducing electromagnetic environment requirements. It has a far-reaching impact on the use of ground terminal communication methods and plays an increasingly important role in future information transmission.

[0003] The air-to-ground laser communication optical system is the core component responsible for the task of light beam emission and reception. Its main functions are: to ensure the quality of the receiving light beam of the ground laser communication device, so that the ground vehicle-mounted terminal can quickly aim and capture the airborne terminal of the aerial platform, and receive sufficient downlink signal light to ensure the imaging quality of the ground laser communication device; to ensure the quality of the receiving light beam of the aerial platform's laser communication device, so that the aerial platform's laser communication device can quickly aim and capture the ground vehicle-mounted terminal, accurately determine the position of the ground vehicle-mounted terminal, and receive sufficient uplink signal light to ensure the imaging quality of the aerial platform's laser communication device; and then realize the establishment of a laser communication link between the ground station and the aerial platform (i.e., link establishment).

[0004] In the air-to-ground laser communication optical system, the beacon light emission branch plays a vital role. Specifically, the beacon light emission branch uses low-power visible light or near-infrared light as beacon light to provide a stable and easily identifiable target point. The ground station and the aerial platform can quickly and accurately complete the initial alignment operation by detecting the beacon light emitted by each other, thus laying the foundation for subsequent precise aiming and capture. Once the initial connection is established between the terminal of the ground station and the terminal of the aerial platform, it is necessary to maintain precise alignment between the two terminals during data transmission. The beacon light can be used as a feedback signal to help the two terminals adjust their respective attitudes and directions in real time to compensate for position deviations caused by atmospheric disturbances, equipment movement and other factors, and ensure the stability of the communication link.

[0005] As an independent branch in the air-to-ground laser communication optical system, within a certain range, the larger the divergence angle of the beacon light of the beacon light transmitting branch, the easier it is to aim, capture and track paired terminals during the rapid link establishment process.

[0006] In the process of rapid link establishment, the air-to-ground laser communication optical system needs to maintain high probability capture and high-precision tracking, which requires a highly stable optical system. It is very difficult for an overly complex optical system to maintain rapid aiming, capture, and tracking in complex environments such as vibration, high and low temperatures, high wind speeds, aerodynamic effects, and atmospheric turbulence. The beacon light emitted by the transmitter of the traditional beacon transmission branch is usually designed as a circular beam. In the actual test process, it was found that the beacon light is restricted by the complex environment and the optical axis is prone to deviation; and because the divergence angle of the circular beam is designed as follows: the azimuth divergence angle and the pitch divergence angle are the same and small, it is difficult to capture the beacon light in a short time based on the existing control strategy, and the circular beam is energy-limited when transmitted over long distances, resulting in the energy received by the opposite terminal being lower than the sensitivity of the detector and unable to be captured. The above situation greatly reduces the efficiency of aiming and capture and prolongs the communication link establishment time. Summary of the invention

[0007] One advantage of the present application is that it provides a beacon transmitting branch of an air-to-ground laser communication optical system, wherein the shape of the beacon light of the beacon transmitting branch of the air-to-ground laser communication optical system is designed to be rectangular or bar-shaped, which can provide a larger capture range and better energy distribution, thereby reducing the dependence on precise optical axis alignment, and can to a certain extent avoid the problem of repeatedly correcting the optical axis of the beacon transmitting branch of the air-to-ground laser communication optical system, saving test time and improving application and test efficiency.

[0008] Another advantage of the present application is that it provides a beacon transmitting branch of an air-to-ground laser communication optical system, wherein the beacon transmitting branch of the air-to-ground laser communication optical system can adjust the divergence angle of the beacon light in the vertical direction, so that the air-to-ground laser communication optical system can change the light beam divergence angle of the beacon transmitting branch of the air-to-ground laser communication optical system according to different link distance conditions, effectively improve the aiming and capturing efficiency, shorten the link establishment time, and improve the tracking stability of the air-to-ground laser communication optical system to meet the requirements of high probability capture and high precision tracking.

[0009] Another advantage of the present application is that it provides a beacon transmission branch of an air-to-ground laser communication optical system, wherein the beacon transmission branch of the air-to-ground laser communication optical system adopts a relatively simplified optical system and is relatively stable.

[0010] Another advantage of the present application is that it provides a beacon transmitting branch of an air-to-ground laser communication optical system, wherein the lens group of the beacon transmitting branch of the air-to-ground laser communication optical system adopts two plano-convex cylindrical lenses with a small number of lenses, so that the optical length of the beacon transmitting branch of the air-to-ground laser communication optical system is shorter, the volume is smaller, and the weight is lighter, and the layout space occupied by the air-to-ground laser communication optical system can be saved.

[0011] According to one aspect of the present application, a beacon transmission branch of an air-to-ground laser communication optical system is provided, which includes: a beacon laser transmission light source and a lens group;

[0012] Wherein, the lens group comprises a first plano-convex cylindrical lens and a second plano-convex cylindrical lens coaxially arranged in sequence along the incident direction of light, the first plano-convex cylindrical lens has positive focal power, and the second plano-convex cylindrical lens has positive focal power;

[0013] The distance between the first plano-convex cylindrical lens and the second plano-convex cylindrical lens is adjustable, and during the process of adjusting the distance between the first plano-convex cylindrical lens and the second plano-convex cylindrical lens, the light beam divergence angle in the horizontal direction of the beacon transmitting branch of the air-to-ground laser communication optical system is maintained at 4°.

[0014] In one embodiment of the beacon transmitting branch of the air-to-ground laser communication optical system described in the present application, the distance between the first plano-convex cylindrical lens and the second plano-convex cylindrical lens is linearly negatively correlated with the beam divergence angle in the vertical direction of the beacon transmitting branch of the air-to-ground laser communication optical system.

[0015] In one embodiment of the beacon transmitting branch of the air-to-ground laser communication optical system described in the present application, when the distance between the first plano-convex cylindrical lens and the second plano-convex cylindrical lens is 0.014 mm, the light beam divergence angle in the vertical direction of the beacon transmitting branch of the air-to-ground laser communication optical system is 1°, and when the distance between the first plano-convex cylindrical lens and the second plano-convex cylindrical lens is 0.925 mm, the light beam divergence angle in the vertical direction of the beacon transmitting branch of the air-to-ground laser communication optical system is 0°.

[0016] In one embodiment of the beacon transmitting branch of the air-to-ground laser communication optical system described in the present application, the entrance pupil position of the beacon transmitting branch of the air-to-ground laser communication optical system is arranged between the beacon laser transmitting light source and the first plano-convex cylindrical lens, and is located at the first plano-convex cylindrical lens. The entrance pupil position of the beacon transmitting branch of the air-to-ground laser communication optical system is the entrance position of the light beam entering the lens group.

[0017] In one embodiment of the beacon transmitting branch of the air-to-ground laser communication optical system described in the present application, the rotation radius of the front surface of the first plano-convex cylindrical lens is greater than 5 mm and less than 6 mm, the curvature radius of the rear surface of the first plano-convex cylindrical lens is infinite, and the center thickness is greater than 2 mm and less than 4 mm.

[0018] In an embodiment of the beacon emission branch of the air-to-ground laser communication optical system according to the present application, the rotation radius of the front surface of the second plano-convex cylindrical lens is greater than 4 mm and less than 5 mm, the curvature radius of the rear surface of the second plano-convex cylindrical lens is infinite, and the central thickness is greater than 1 mm and less than 3 mm.

[0019] In an embodiment of the beacon emission branch of the air-to-ground laser communication optical system according to the present application, the refractive indices of the optical materials of the first plano-convex cylindrical lens and the second plano-convex cylindrical lens are both 1.51680, and the dispersion coefficients of the optical materials are both 64.17.

[0020] In an embodiment of the beacon emission branch of the air-to-ground laser communication optical system according to the present application, the distance between the exit surface of the beacon laser emission light source and the first plano-convex cylindrical lens is 4 mm < L1 < 6 mm, and the distance between the first plano-convex cylindrical lens and the second plano-convex cylindrical lens is 0 mm < L2 < 1 mm.

[0021] In an embodiment of the beacon emission branch of the air-to-ground laser communication optical system according to the present application, the numerical aperture of the beacon laser emission light source is 0.14, and the first plano-convex cylindrical lens and the second plano-convex cylindrical lens are made of the same type of glass, and the type is N-BK7.

[0022] In an embodiment of the beacon emission branch of the air-to-ground laser communication optical system according to the present application, the beacon emission branch of the air-to-ground laser communication optical system is applied to an air-to-ground laser communication terminal, and the air-to-ground laser communication terminal further includes a main receiving optical antenna, a signal emission branch, a signal receiving branch, and a beacon receiving branch.

[0023] Through the understanding of the subsequent description and the drawings, the further objects and advantages of the present application will be fully embodied.

[0024] These and other objects, features, and advantages of the present application will be fully embodied through the following detailed description, drawings, and claims. Description of the Drawings

[0025] By describing the embodiments of the present application in more detail in conjunction with the drawings, the above-mentioned and other objects, features, and advantages of the present application will become more obvious. The drawings are used to provide a further understanding of the embodiments of the present application, and constitute a part of the specification. Together with the embodiments of the present application, they are used to explain the present application, and do not constitute a limitation to the present application. In the drawings, the same reference numerals generally represent the same components.

[0026] Figure 1 The schematic diagram of the framework of the air-to-ground laser communication optical system according to the embodiment of the present application is illustrated.

[0027] Figure 2 The figure shows a schematic structural diagram of the beacon transmission branch of the air-to-ground laser communication optical system according to an embodiment of the present application when the beam divergence angle in the horizontal direction is 4° and the beam divergence angle in the vertical direction is 1°.

[0028] Figure 3 The figure shows a schematic structural diagram of the beacon transmission branch of the air-to-ground laser communication optical system according to an embodiment of the present application when the beam divergence angle in the horizontal direction is 4° and the beam divergence angle in the vertical direction is 0°.

[0029] Figure 4 The figure shows a schematic diagram of the point diagram of the beacon light corresponding to the case where the beam divergence angle in the horizontal direction of the beacon transmitting branch of the air-to-ground laser communication optical system according to an embodiment of the present application is 4° and the beam divergence angle in the vertical direction is 1°.

[0030] Figure 5 The figure shows a schematic diagram of the point diagram of the beacon light corresponding to the case where the beam divergence angle in the horizontal direction of the beacon transmitting branch of the air-to-ground laser communication optical system according to an embodiment of the present application is 4° and the beam divergence angle in the vertical direction is 0°.

[0031] Figure 6 The diagram illustrates a schematic diagram of the relationship between the distance between the first plano-convex cylindrical lens and the second plano-convex cylindrical lens of the beacon transmitting branch of the air-to-ground laser communication optical system according to an embodiment of the present application and the beam divergence angle in the vertical direction of the beacon transmitting branch of the air-to-ground laser communication optical system. DETAILED DESCRIPTION

[0032] Below, the exemplary embodiments according to the present application will be described in detail with reference to the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application, and it should be understood that the present application is not limited to the exemplary embodiments described here.

[0033] It is understood that the term "one" should be understood as "at least one" or "one or more", that is, in one embodiment, the number of an element can be one, while in another embodiment, the number of the element can be multiple, and the term "one" cannot be understood as a limitation on the number. "Multiple" means greater than or equal to two.

[0034] Although ordinals such as "first," "second," and the like will be used to describe various components, those components are not limited herein. The term is used only to distinguish one component from another. For example, a first component may be referred to as a second component, and likewise, a second component may be referred to as a first component without departing from the teachings of the present application. The term "and / or" as used herein includes any and all combinations of one or more associated listed items.

[0035] The terms used herein are only used for the purpose of describing various embodiments and are not intended to be limiting. As used herein, the singular form is intended to include the plural form, unless the context clearly indicates an exception. It will also be understood that the terms "including" and / or "having" when used in this specification specify the presence of the described features, numbers, operations, components, elements, or combinations thereof, without excluding the presence or addition of one or more other features, numbers, operations, components, elements, or combinations thereof.

[0036] like Figures 1 to 6 As shown, a beacon transmission branch 10 of an air-to-ground laser communication optical system according to an embodiment of the present application is illustrated. The air-to-ground laser communication optical system beacon transmission branch 10 is applied to an air-to-ground laser communication terminal, and is used to transmit an independent beacon light to another air-to-ground laser communication terminal corresponding to the air-to-ground laser communication terminal, so that the other air-to-ground laser communication terminal corresponding to the air-to-ground laser communication terminal quickly enters the aiming, capturing, and tracking state after receiving the beacon light of the air-to-ground laser communication terminal; for the convenience of description, one of the air-to-ground laser communication terminals is defined as a first air-to-ground laser communication terminal, and another air-to-ground laser communication terminal corresponding to the air-to-ground laser communication terminal is defined as a second air-to-ground laser communication terminal; that is, one of the air-to-ground laser communication optical system beacon transmission branch 10 is applied to a first air-to-ground laser communication terminal, and is used to transmit an independent beacon light to the second air-to-ground laser communication terminal corresponding to the first air-to-ground laser communication terminal, so that the second air-to-ground laser communication terminal quickly enters the aiming, capturing, and tracking state after receiving the beacon light of the first air-to-ground laser communication terminal.

[0037] Specifically, Figure 1 As shown, the air-to-ground laser communication terminal (the first air-to-ground laser communication terminal or the second air-to-ground laser communication terminal) in the present application includes a main receiving optical antenna 20, a signal transmitting branch 30, a signal receiving branch 40, the air-to-ground laser communication optical system beacon transmitting branch 10 and a beacon receiving branch 50.

[0038] The main receiving optical antenna 20 is used to receive the signal beam emitted by another air-to-ground laser communication terminal, and send it to the relay optical path unit after beam reduction; it is also used to receive the signal beam emitted by the relay optical path unit, expand and collimate it, and then transmit it to another air-to-ground laser communication terminal; for example, the main receiving optical antenna 20 of the first air-to-ground laser communication terminal is used to receive the signal beam emitted by the second air-to-ground laser communication terminal, and send it to the relay optical path unit of the first air-to-ground laser communication terminal after beam reduction; it is also used to receive the signal beam emitted by the relay optical path unit of the first air-to-ground laser communication terminal, expand and collimate it, and then transmit it to the second air-to-ground laser communication terminal. The main receiving optical antenna 20 includes an antenna primary mirror 21, an antenna secondary mirror 22, and a fast reflection mirror 23. The antenna primary mirror 21 is opposite to the antenna secondary mirror 22, and is suitable for receiving the light reflected by the antenna secondary mirror 22 on the light reflection path of the antenna secondary mirror 22; the antenna secondary mirror 22 is suitable for receiving the light reflected by the fast reflection mirror 23 on the light reflection path of the fast reflection mirror 23.

[0039] The signal transmission branch 30 is used to transmit signal light, wherein the signal transmission branch 30 includes a signal transmission light source 31, a signal light transmission lens 32, a dichroic mirror 33 and a beam splitter 34. The signal transmission light source 31 is used to emit signal light; the signal light transmission lens 32 is on the light emission path of the signal transmission light source 31; the dichroic mirror 33 is on the light emission path of the signal light emission lens 32 and on the light reflection path of the fast reflection mirror 23; the beam splitter 34 is on the light emission path of the dichroic mirror 33 and on the light reflection path of the fast reflection mirror 23. The emitted signal light is collimated by the signal light emission lens 32, and then reflected by the dichroic mirror 33 to the quick reflection mirror 23, and the signal emission branch 30 is emitted after passing through the antenna secondary mirror 22 and the antenna primary mirror 21; for example, the signal light emitted by the signal emission branch 30 of the first air-to-ground laser communication terminal is collimated by the signal light emission lens 32 of the first air-to-ground laser communication terminal, and then reflected by the dichroic mirror 33 of the first air-to-ground laser communication terminal to the quick reflection mirror 23 of the first air-to-ground laser communication terminal, and then emitted to the second air-to-ground laser communication terminal through the antenna secondary mirror 22 and the antenna primary mirror 21 of the first air-to-ground laser communication terminal.

[0040] The signal receiving branch 40 is used to receive the signal light emitted by another air-to-ground laser communication terminal, wherein the signal receiving branch 40 includes a first filter 41, a signal light receiving lens 42 and a first communication detector 43. The first filter 41 is on the light emission path of the spectroscope 34; the signal light receiving lens 42 is on the light emission path of the first filter 41; the first communication detector 43 is on the light emission path of the signal light receiving lens 42; wherein the first communication detector 43 can be an avalanche photodiode (APD) detector or other types of detectors.

[0041] Specifically, the signal light from another air-to-ground laser communication terminal is focused by the antenna main mirror 21 of the main receiving optical antenna 20, reflected by the fast reflection mirror 23, and then passes through the color separation mirror 33 and the beam splitter 34, filtered by the first filter 41, and focused by the signal light receiving lens 42, and is received by the first communication detector 43 and converted into an electrical signal and transmitted to the data processing unit; for example, the signal light from the second air-to-ground laser communication terminal is focused by the antenna main mirror 21 of the main receiving optical antenna 20 of the first air-to-ground laser communication terminal, reflected by the fast reflection mirror 23 of the first air-to-ground laser communication terminal, and then passes through the color separation mirror 33 and the beam splitter 34 of the first air-to-ground laser communication terminal, filtered by the first filter 41 of the first air-to-ground laser communication terminal, and focused by the signal light receiving lens 42, and is received by the first communication detector 43 of the first air-to-ground laser communication terminal and converted into an electrical signal and transmitted to the data processing unit.

[0042] The beacon receiving branch 50 is used to receive beacon light. The beacon receiving branch 50 includes a second filter 51, a beacon light receiving lens 52 and a second communication detector 53. The second filter 51 is on the light output path of the spectroscope 34; the beacon light receiving lens 52 is on the light output path of the second filter 51; the second communication detector 53 is on the light output path of the beacon light receiving lens 52; wherein, the second communication detector 53 can be a charge coupled device (CCD) detector, a complementary metal oxide semiconductor (CMOS) detector, or other types of detectors.

[0043] Specifically, the beacon light from another air-to-ground laser communication terminal is focused by the antenna main mirror 21 of the main receiving optical antenna 20, reflected by the fast reflection mirror 23, and then passed through the color separation mirror 33, reflected by the beam splitter 34, filtered by the second filter 51, focused by the beacon light receiving lens 52, received by the second communication detector 53, converted into an electrical signal and transmitted to the control unit; for example, the beacon light from the second air-to-ground laser communication terminal is focused by the antenna main mirror 21 of the main receiving optical antenna 20 of the first air-to-ground laser communication terminal, reflected by the fast reflection mirror 23 of the first air-to-ground laser communication terminal, and then passed through the color separation mirror 33 of the first air-to-ground laser communication terminal, reflected by the beam splitter 34 of the first air-to-ground laser communication terminal, filtered by the second filter 51 of the first air-to-ground laser communication terminal, focused by the beacon light receiving lens 52, received by the second communication detector 53 of the first air-to-ground laser communication terminal, converted into an electrical signal and transmitted to the control unit. After data processing, the control unit feeds back the measured target deviation to the fast-reflection mirror 23 driver and the coarse-aiming servo turntable, thereby further completing aiming, capturing, tracking and docking.

[0044] The beacon transmission branch 10 of the air-to-ground laser communication optical system includes a beacon laser emission light source 11 and a beacon light emission lens. The beacon laser emission light source 11 is used to emit beacon light; the beacon light emission lens includes a lens group 12 on the light emission path of the beacon laser emission light source 11.

[0045] The wavelength of the beacon light emitted by the beacon laser emission light source 11 is about 1550nm. Accordingly, the working wavelength of the beacon emission branch 10 of the air-to-ground laser communication optical system is about 1550nm. The numerical aperture of the beacon laser emission light source 11 is 0.14.

[0046] As mentioned above, in the process of rapid link establishment, the air-to-ground laser communication optical system needs to maintain high probability capture and high-precision tracking, which requires a highly stable optical system. It is very difficult for an overly complex optical system to maintain rapid aiming, capture, and tracking in complex environments such as vibration, high and low temperatures, high wind speeds, aerodynamic effects, and atmospheric turbulence; based on this, the air-to-ground laser communication optical system beacon transmission branch 10 of the present application adopts a relatively simplified optical system, which is relatively stable. The lens group 12 of the air-to-ground laser communication optical system beacon transmission branch 10 adopts two plano-convex cylindrical lenses with a small number of lenses, so that the optical length of the air-to-ground laser communication optical system beacon transmission branch 10 is shorter, the volume is smaller, and the weight is lighter, and the layout space occupied by the air-to-ground laser communication optical system can be saved.

[0047] Accordingly, if Figure 2As shown, the lens group 12 includes a first plano-convex cylindrical lens 121 and a second plano-convex cylindrical lens 122 arranged coaxially in sequence along the light incident direction. The first plano-convex cylindrical lens 121 has a positive optical power and is used for beam narrowing, that is, converging the light beam; the second plano-convex cylindrical lens 122 has a positive optical power and is used for beam expanding, that is, diverging the light beam.

[0048] The first plano-convex cylindrical lens 121 and the second plano-convex cylindrical lens 122 are made of the same type of glass. In an example of the present application, the first plano-convex cylindrical lens 121 and the second plano-convex cylindrical lens 122 are made of glass with the model N-BK7, and the research, development and processing costs are relatively low.

[0049] In the present application, the direction close to the object side is defined as the front, and the direction close to the image side is defined as the back.

[0050] In the embodiment of the present application, the rotational radius of the front surface of the first plano-convex cylindrical lens 121 is greater than 5 mm and less than 6 mm, the curvature radius of the back surface of the first plano-convex cylindrical lens 121 is infinite, and the central thickness is greater than 2 mm and less than 4 mm.

[0051] The rotational radius of the front surface of the second plano-convex cylindrical lens 122 is greater than 4 mm and less than 5 mm, the curvature radius of the back surface of the second plano-convex cylindrical lens 122 is infinite, and the central thickness is greater than 1 mm and less than 3 mm.

[0052] The refractive indices of the optical materials of the first plano-convex cylindrical lens 121 and the second plano-convex cylindrical lens 122 are both 1.51680, and the dispersion coefficients of the optical materials are both 64.17.

[0053] The distance between the exit surface of the beacon laser emission light source 11 and the first plano-convex cylindrical lens 121 satisfies 4 mm < L1 < 6 mm, and the distance between the first plano-convex cylindrical lens 121 and the second plano-convex cylindrical lens 122 satisfies 0 mm < L2 < 1 mm.

[0054] In an example of the present application, the numerical aperture of the beacon laser emission light source 11 is 0.14, and the working wavelength is 1550 nm; the rotational radius of the front surface of the first plano-convex cylindrical lens 121 is 5.220 mm, the curvature radius of the back surface of the first plano-convex cylindrical lens 121 is infinite, and the central thickness of the first plano-convex cylindrical lens 121 is 3 mm; the rotational radius of the front surface of the second plano-convex cylindrical lens 122 is 4.313 mm, the curvature radius of the back surface of the second plano-convex cylindrical lens 122 is infinite, and the central thickness of the second plano-convex cylindrical lens 122 is 2 mm; the distance between the beacon laser emission light source 11 and the first plano-convex cylindrical lens 121 is 5 mm.

[0055] It is worth mentioning that, as mentioned above, the beacon light emitted by the transmitter of the traditional beacon transmission branch is usually designed as a circular beam. In the actual test process, it was found that the beacon light is restricted by the complex environment and is prone to optical axis deviation; and because the divergence angle of the circular light beam is designed as follows: the azimuth divergence angle and the pitch divergence angle are the same and small, it is difficult to capture the beacon light in a short time based on the existing control strategy, and the circular light beam is energy-limited when transmitted over long distances, resulting in the energy received by the opposite terminal being lower than the sensitivity of the detector and unable to be captured; based on this, the present application proposes that the beacon light can be designed as a rectangular or strip-shaped beam, such as Figure 4 and Figure 5 As shown; and further, the divergence angle of the beacon light in the vertical direction can be adjusted by adjusting the distance between the first plano-convex cylindrical lens 121 and the second plano-convex cylindrical lens 122, that is, the divergence angle of the light beam in the vertical direction of the beacon transmitting branch 10 of the air-to-ground laser communication optical system; the shape of the beacon light changes accordingly.

[0056] Designing the shape of the beacon light of the beacon transmitting branch 10 of the air-to-ground laser communication optical system to be rectangular or bar-shaped can provide a larger capture range and better energy distribution, thereby reducing the reliance on precise optical axis alignment. The rectangular or bar-shaped beacon light allows a certain degree of optical axis deviation in design without significantly affecting the communication quality, so there is no need to consider the problem of optical axis deviation too much, and can avoid the problem of repeated correction of the optical axis of the beacon transmitting branch 10 of the air-to-ground laser communication optical system to a certain extent, saving test time, improving application and test efficiency, and is used in application scenarios where a stable communication link needs to be quickly established under complex environmental conditions. By optimizing the beam shape of the beacon light, not only can the aiming and capturing efficiency of the air-to-ground laser communication terminal be improved, but also the reliance on the high-precision alignment system can be reduced, simplifying the design difficulty of the overall air-to-ground laser communication system. Furthermore, the beam divergence angle of the beacon transmitting branch 10 of the air-to-ground laser communication optical system can be changed according to different link distance working conditions, which can effectively improve the aiming and capturing efficiency, shorten the link establishment time, and improve the tracking stability of the air-to-ground laser communication optical system, meeting the requirements of high probability capture and high-precision tracking.

[0057] The shape of the beacon light of the beacon transmitting branch 10 of the air-to-ground laser communication optical system is designed to be rectangular or bar-shaped, which can provide a larger capture range, which is specifically reflected in the angle coverage and environmental adaptability. In terms of angle coverage, the shape of the beacon light of the beacon transmitting branch 10 of the air-to-ground laser communication optical system is designed to be rectangular or bar-shaped, which can provide a larger divergence angle in a specific direction. For example, a 4°×1° strip beam has a divergence angle of 4° in the horizontal direction and a divergence angle of only 1° in the vertical direction. This means that even if there is a certain optical axis offset, the receiving end can still capture the signal within a wider angle range; the larger divergence angle provides additional tolerance space, allowing the optical axis to deviate from the ideal position within a certain range without affecting the communication quality. This redundancy is very useful for dealing with minor displacements caused by atmospheric disturbances, equipment vibrations, etc. In terms of environmental adaptability, in practical applications, especially under variable atmospheric conditions (such as wind speed changes, temperature fluctuations, etc.), the optical axis may be slightly offset. The design of rectangular or strip beams enables the system to better adapt to these changes and reduce the risk of communication interruption due to environmental factors.

[0058] The shape of the beacon light of the beacon transmitting branch 10 of the air-to-ground laser communication optical system is designed to be rectangular or strip-shaped, which can provide better energy distribution, which is specifically reflected in energy concentration and diffusion and reducing energy loss. In terms of energy concentration and diffusion, rectangular or strip-shaped light beams can optimize energy distribution, and can expand energy distribution in another direction while maintaining high resolution in a certain direction. For example, a wider divergence angle in the horizontal direction can ensure that enough energy covers the effective area of ​​the receiving end, while a smaller divergence angle in the vertical direction ensures higher energy density and signal strength. Rectangular or strip-shaped light beams can also improve the receiving efficiency. By reasonably designing the shape of the light beam, more light energy can be concentrated in the effective area of ​​the receiving end, thereby improving the overall receiving efficiency. This is particularly important for long-distance communication, because during long-distance transmission, the light beam will naturally diffuse, resulting in energy attenuation. In terms of reducing energy loss, rectangular or strip-shaped light beams can concentrate more energy in key directions by directional diffusion, thereby reducing energy loss and improving the success rate of long-distance communication.

[0059] The shape of the beacon light of the beacon transmitting branch 10 of the air-to-ground laser communication optical system is designed to be rectangular or strip-shaped, which can reduce the dependence on precise optical axis alignment, which is specifically reflected in the two aspects of simplifying the alignment process and enhancing dynamic response. Rectangular or strip-shaped light beams can reduce the difficulty of alignment, and their non-circular symmetry means that they do not need to be strictly aligned like circular light beams to achieve effective communication, which greatly simplifies the process of initial alignment and subsequent tracking, and reduces the complexity and cost of the system; rectangular or strip-shaped light beams can also improve fault tolerance. Since rectangular or strip-shaped light beams have a large divergence angle, even if the optical axis is offset to a certain extent, the receiving end can still receive sufficient signal strength, thereby improving the fault tolerance and robustness of the system. In terms of enhancing dynamic response, rectangular or strip-shaped light beams can be quickly adjusted and compensated. When the optical axis is offset, the rectangular or strip-shaped light beam can quickly compensate for the deviation by adjusting its pointing direction without frequently adjusting the posture of the entire system. This flexibility makes the tracking algorithm simpler and more efficient, and further reduces the error caused by the deviation of the optical axis.

[0060] Accordingly, the distance between the first plano-convex cylindrical lens 121 and the second plano-convex cylindrical lens 122 is adjustable, such as Figure 2 and Figure 3 As shown, during the process of adjusting the distance between the first plano-convex cylindrical lens 121 and the second plano-convex cylindrical lens 122, the light beam divergence angle in the horizontal direction of the beacon transmitting branch 10 of the air-to-ground laser communication optical system is maintained at 4°.

[0061] Table 1 below shows the beam divergence angles in the horizontal and vertical directions of the beacon transmitting branch 10 of the air-to-ground laser communication optical system under different link distance conditions, as well as the distance between the first plano-convex cylindrical lens 121 and the second plano-convex cylindrical lens 122.

[0062] The distance between the first plano-convex cylindrical lens 121 and the second plano-convex cylindrical lens 122 is linearly negatively correlated with the beam divergence angle in the vertical direction of the beacon transmitting branch 10 of the air-to-ground laser communication optical system, such as Figure 6 shown.

[0063] Table 1

[0064]

[0065] When adjusting the vertical beam divergence angle of the beacon transmitting branch 10 of the air-to-ground laser communication optical system under different link distance conditions, the translation distance interval of the second plano-convex cylindrical lens 122 under each condition can be designed to basically form an arithmetic progression, which can achieve rapid switching, thereby quickly establishing aiming, capturing and tracking links.

[0066] The distance between the exit surface of the beacon laser emission light source 11 and the first plano-convex cylindrical lens 121 satisfies 4mm < L1 < 6mm, and the distance between the first plano-convex cylindrical lens 121 and the second plano-convex cylindrical lens 122 satisfies 0mm < L2 < 1mm. The distance between the exit surface of the beacon laser emission light source 11 and the first plano-convex cylindrical lens 121 refers to the distance between the exit surface of the beacon laser emission light source 11 and the incident surface of the first plano-convex cylindrical lens 121. The distance between the first plano-convex cylindrical lens 121 and the second plano-convex cylindrical lens 122 refers to the distance between the exit surface of the first plano-convex cylindrical lens 121 and the incident surface of the second plano-convex cylindrical lens 122.

[0067] When the distance between the first plano-convex cylindrical lens 121 and the second plano-convex cylindrical lens 122 is 0.014mm, the beam divergence angle in the vertical direction of the beacon emission branch 10 of the air-to-ground laser communication optical system is 1°. When the distance between the first plano-convex cylindrical lens 121 and the second plano-convex cylindrical lens 122 is 0.925mm, the beam divergence angle in the vertical direction of the beacon emission branch 10 of the air-to-ground laser communication optical system is 0°. The distance between the first plano-convex cylindrical lens 121 and the second plano-convex cylindrical lens 122 can be freely and continuously adjusted between 0.014mm and 0.925mm to achieve free switching between rectangular beams and long strip beams.

[0068] The entrance pupil position of the beacon emission branch 10 of the air-to-ground laser communication optical system is located between the beacon laser emission light source 11 and the first plano-convex cylindrical lens 121. Specifically, the entrance pupil position of the beacon emission branch 10 of the air-to-ground laser communication optical system can be located at the first plano-convex cylindrical lens 121.

[0069] Correspondingly, in an example of the present application, the beacon emission branch 10 of the air-to-ground laser communication optical system further includes an aperture stop. The aperture stop is disposed between the beacon laser emission light source 11 and the first plano-convex cylindrical lens 121 and is used to limit the effective aperture of the beam incident on the lens group 12, that is, the entrance pupil diameter. The aperture stop can be disposed adjacent to the first plano-convex cylindrical lens 121 on the object side of the first plano-convex cylindrical lens 121.

[0070] In summary, the beacon transmitting branch 10 of the air-to-ground laser communication optical system according to the embodiment of the present application is explained. The beacon transmitting branch 10 of the air-to-ground laser communication optical system designs the shape of the beacon light to be rectangular or bar-shaped, which can provide a larger capture range and better energy distribution, thereby reducing the dependence on precise optical axis alignment, and can avoid the problem of repeatedly correcting the optical axis of the beacon transmitting branch 10 of the air-to-ground laser communication optical system to a certain extent, saving test time and improving application and test efficiency. Furthermore, the beacon transmitting branch 10 of the air-to-ground laser communication optical system can adjust the divergence angle of the beacon light in the vertical direction, so that the air-to-ground laser communication optical system can transform the beam divergence angle of the beacon transmitting branch 10 of the air-to-ground laser communication optical system according to different link distance conditions, effectively improve the aiming and capturing efficiency, shorten the link establishment time, and improve the tracking stability of the air-to-ground laser communication optical system, meeting the requirements of high probability capture and high-precision tracking. In addition, the beacon transmitting branch 10 of the air-to-ground laser communication optical system adopts a relatively simplified optical system, which is relatively stable.

[0071] The present application and its implementation methods are described above, and such description is not restrictive. The drawings show only one implementation method of the present application, and the actual structure is not limited thereto. In short, if ordinary technicians in the field are inspired by it and design structural methods and embodiments similar to the technical solution without creative design without departing from the inventive purpose of the present application, they should all fall within the protection scope of the present application.

Claims

1. A beacon transmission branch of an air-to-ground laser communication optical system, characterized in that: Comprising: A beacon laser emission light source and a lens group; Wherein, the lens group includes a first plano-convex cylindrical lens and a second plano-convex cylindrical lens arranged coaxially in sequence along the light incident direction. The first plano-convex cylindrical lens has a positive optical power, and the second plano-convex cylindrical lens has a positive optical power; The distance between the first plano-convex cylindrical lens and the second plano-convex cylindrical lens is adjustable. During the process of adjusting the distance between the first plano-convex cylindrical lens and the second plano-convex cylindrical lens, the beam divergence angle in the horizontal direction of the beacon emission branch of the air-to-ground laser communication optical system remains 4°; Wherein, the distance between the first plano-convex cylindrical lens and the second plano-convex cylindrical lens is linearly negatively correlated with the beam divergence angle in the vertical direction of the beacon emission branch of the air-to-ground laser communication optical system.

2. The beacon transmission branch of the air-to-ground laser communication optical system according to claim 1 is characterized in that: When the distance between the first plano-convex cylindrical lens and the second plano-convex cylindrical lens is 0.014 mm, the beam divergence angle in the vertical direction of the beacon emission branch of the air-to-ground laser communication optical system is 1°. When the distance between the first plano-convex cylindrical lens and the second plano-convex cylindrical lens is 0.925 mm, the beam divergence angle in the vertical direction of the beacon emission branch of the air-to-ground laser communication optical system is 0°.

3. The beacon transmission branch of the air-to-ground laser communication optical system according to claim 1, characterized in that: The entrance pupil position of the beacon emission branch of the air-to-ground laser communication optical system is set between the beacon laser emission light source and the first plano-convex cylindrical lens and is located at the first plano-convex cylindrical lens. The entrance pupil position of the beacon emission branch of the air-to-ground laser communication optical system is the entrance position where the beam enters the lens group.

4. The beacon transmission branch of the air-to-ground laser communication optical system according to claim 1, characterized in that: The rotational radius of the front surface of the first plano-convex cylindrical lens is greater than 5 mm and less than 6 mm, the curvature radius of the rear surface of the first plano-convex cylindrical lens is infinite, and the central thickness is greater than 2 mm and less than 4 mm.

5. The beacon transmission branch of the air-to-ground laser communication optical system according to claim 1, characterized in that: The rotational radius of the front surface of the second plano-convex cylindrical lens is greater than 4 mm and less than 5 mm, the curvature radius of the rear surface of the second plano-convex cylindrical lens is infinite, and the central thickness is greater than 1 mm and less than 3 mm.

6. The beacon transmission branch of the air-to-ground laser communication optical system according to claim 1, characterized in that: The refractive indices of the optical materials of the first plano-convex cylindrical lens and the second plano-convex cylindrical lens are both 1.51680, and the optical material dispersion coefficients are both 64.

17.

7. The beacon transmission branch of the air-to-ground laser communication optical system according to claim 1, characterized in that: The distance between the emission surface of the beacon laser emission light source and the first plano-convex cylindrical lens is 4 mm < L1 < 6 mm, and the distance between the first plano-convex cylindrical lens and the second plano-convex cylindrical lens is 0 mm < L2 < 1 mm.

8. The beacon transmission branch of the air-to-ground laser communication optical system according to claim 1, characterized in that: The numerical aperture of the beacon laser emission light source is 0.14, and the first plano-convex cylindrical lens and the second plano-convex cylindrical lens are made of the same type of glass, and the type is N-BK7.

9. The beacon transmission branch of the air-to-ground laser communication optical system according to claim 1, characterized in that: The beacon emission branch of the air-to-ground laser communication optical system is applied to an air-to-ground laser communication terminal, and the air-to-ground laser communication terminal further includes a main receiving optical antenna, a signal emission branch, a signal receiving branch, and a beacon receiving branch.

Images