CN117040626A - Wireless optical communication tracking and positioning method and system - Google Patents
Wireless optical communication tracking and positioning method and system Download PDFInfo
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- CN117040626A CN117040626A CN202310895323.0A CN202310895323A CN117040626A CN 117040626 A CN117040626 A CN 117040626A CN 202310895323 A CN202310895323 A CN 202310895323A CN 117040626 A CN117040626 A CN 117040626A
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- 230000005540 biological transmission Effects 0.000 claims abstract description 54
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
- H04B10/11—Arrangements specific to free-space transmission, i.e. transmission through air or vacuum
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
- H04B10/50—Transmitters
- H04B10/501—Structural aspects
- H04B10/503—Laser transmitters
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
- H04B10/60—Receivers
- H04B10/66—Non-coherent receivers, e.g. using direct detection
- H04B10/67—Optical arrangements in the receiver
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02D—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN INFORMATION AND COMMUNICATION TECHNOLOGIES [ICT], I.E. INFORMATION AND COMMUNICATION TECHNOLOGIES AIMING AT THE REDUCTION OF THEIR OWN ENERGY USE
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- Y02D30/70—Reducing energy consumption in communication networks in wireless communication networks
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Abstract
The invention belongs to the technical field of laser communication, and relates to a wireless optical communication tracking and positioning method and system. The method comprises the following steps: s1, realizing time-sharing receiving of incident light in different areas, and converting a received optical signal into an electric signal; s2, processing the electric signals, and calculating the spot position and deviation angle information of incident light to obtain deflection execution quantity; and step S3, carrying out posture adjustment on the optical receiving module according to the deflection execution amount so as to ensure that the optical receiving module is aligned with incident light and realize laser communication. The invention uses a transmission type liquid crystal panel to replace a four-quadrant detector, and is matched with a rotating wheel and an optical detector to serve as an optical receiving unit; the four areas of the transmission type liquid crystal panel are controlled to periodically transmit light, and the light is homogenized through the rotating wheel and falls into the optical detector; the problem that the four-quadrant detector can only be used as a position sensitive detector is solved, and the production cost is reduced.
Description
Technical Field
The invention belongs to the technical field of laser communication, and relates to a wireless optical communication tracking and positioning method and system.
Background
It is known in the art that in an underwater wireless optical communication system, point-to-point communication is usually performed, and in an underwater channel, due to interference such as absorption scattering, turbulence and bubbles, a target light beam is easily separated from the detection range of a receiver, and a laser tracking and positioning system is usually used at the light receiving end to realize accurate alignment of the light beam. At present, a four-quadrant detector is generally used as a position sensitive detector in a laser tracking and positioning system to detect two-dimensional position information of a target beam, and the position of a facula centroid is determined through a four-quadrant positioning algorithm to determine the angle of incident light, so that tracking and positioning of the laser communication system are realized.
The existing four-quadrant detector is an optical detection device which divides a circular or square photosensitive surface into a plurality of quadrant areas which are mutually isolated, equal in area, identical in shape and symmetrical in position by utilizing a photoetching technology. Under ideal conditions, each quadrant of the four-quadrant detector has the same photoelectric characteristic, and under uniform light spot irradiation, photocurrents generated by each quadrant are equal, and the photocurrents are amplified through a later-stage circuit, so that obtained voltage signals are equal. When the target position deviates from the optical axis, the light spot formed on the photosensitive surface of the detector deviates from the center of the device through the optical system, so that the received light energy of each quadrant is different, and different photocurrents are output. The specific deviation position of the light spot is determined by comparing the current of each quadrant, so that the azimuth information of the target is calculated.
However, using a four-quadrant detector as an optical communication detector mainly has the following problems: 1) The diameter of the four-quadrant photosurface is only 1cm at most, and when the photosurface cannot be irradiated by light spots, the four-quadrant detector cannot work; 2) If the target light spot deviates from a quadrant, only the quadrant has output, and the other quadrant outputs 0, so that the specific position of the light spot in the quadrant cannot be judged from the quadrant output, and the light spot positioning fails. In view of this, the present invention has been made.
Disclosure of Invention
The invention aims to overcome the defects of the prior art, and provides a wireless optical communication tracking and positioning method and system, which solve the problems of narrow detection range and light spot positioning failure of a four-quadrant detector and reduce the cost.
In order to achieve the above purpose, the present invention provides the following technical solutions:
in one aspect, the invention provides a wireless optical communication tracking and positioning method, which specifically comprises the following steps:
s1, realizing time-sharing receiving of incident light in different areas, and converting a received optical signal into an electric signal;
s2, processing the electric signals, and calculating the spot position and deviation angle information of the incident light to obtain deflection execution quantity;
and step S3, carrying out posture adjustment on the optical receiving module according to the deflection execution amount so as to ensure that the optical receiving module is aligned with incident light and realize laser communication.
Further, in the step S1, time-sharing receiving of the incident light in different areas is implemented, which specifically includes:
step S1.1, controlling the focal length of the electric control zoom lens through voltage to enable the focal length to be equal to the distance between the transmission type liquid crystal panel and the electric control zoom lens, and converging incident light to the transmission type liquid crystal panel through the electric control zoom lens; rotating the rotating wheel to enable incident light to pass through the scattering area to reach the optical detector;
s1.2, realizing time-sharing receiving of incident light irradiated to an optical detector after passing through different areas of the transmission type liquid crystal panel by controlling the transmittance change of the different areas of the transmission type liquid crystal panel; the different areas comprise four areas which are mutually isolated, equal in area, identical in shape and symmetrical in position and divide the transmission type liquid crystal panel.
Further, the step S2 specifically includes:
s2.1, amplifying the electric signal by a signal amplifying circuit;
s2.2, sampling the amplified electric signals by an A/D sampling circuit and calculating the light spot intensities of different areas;
and S2.3, calculating the spot position and the deviation angle information of the incident light according to the spot intensity.
Further, the step S2.3 specifically includes:
s2.3.1, converging the incident light by an optical lens, focusing the incident light into light spots on a plane where the transmissive liquid crystal panel is located, dividing the laser to be measured by the transmissive liquid crystal panel through A, B, C, D four quadrants, and converting the received light intensity into photocurrents to be respectively recorded as I A 、I B 、I c 、I D The magnitude of the photocurrent is in direct proportion to the light spot area and the illumination intensity;
step S2.3.2, calculating relative offsets Δx and Δy of the light spot center on the transmissive liquid crystal panel, where the calculation formula is as follows:
wherein k is a coefficient;
step S2.3.3, calculating the included angle θ between the incident light and the optical axis according to the relative offsets Δx and Δy, and recording the included angles between the projection light of the incident light on the xoz plane and the projection light of the incident light on the yoz plane and the optical axis as Δθ respectively x 、△θ y The included angles theta and delta theta x 、△θ y The calculation formulas of (a) are respectively as follows:
Δθ x ＝arctan(Δx/f)
Δθ y ＝arctan(Δy/f)
wherein f is the distance between the transmissive liquid crystal panel and the optical lens.
Further, the step S3 specifically includes:
s3.1, transmitting the deflection execution amount into a mechanical servo driving module, and generating a time sequence pulse signal to control the mechanical servo module to act according to the received deflection execution amount by the mechanical servo driving module;
s3.2, the mechanical servo module controls the optical receiving module to rotate according to the received deflection execution amount so as to ensure that incident light falls into the optical center of the optical receiving module;
step S3.3, controlling the focal length of the electric control zoom lens through voltage to enable the focal length to be equal to the distance between the transmission type liquid crystal panel and the optical detector; the rotating wheel is rotated to enable incident light to pass through the full-transmission area to reach the optical detector, and the system enters a communication stage.
On the other hand, the invention also provides a system applying the wireless optical communication tracking and positioning method, which can ensure the effectiveness of light spot positioning through multiple times of segmentation of the liquid crystal panel and can eliminate the problem that the four-quadrant detector fails when the light spot is positioned at one or two image points. The system comprises an optical receiving module for receiving optical signals, and a signal processing module connected with the optical receiving module, wherein the signal processing module is connected with the optical receiving module sequentially through a mechanical servo driving module and a mechanical servo module;
the optical receiving module comprises an optical lens, a transmission type liquid crystal panel, a rotating wheel and an optical detector which are sequentially distributed; the optical lens is used for converging incident light into the transmission type liquid crystal panel in the extraction stage; for converging incident light to an optical detector during a communication phase; the transmission type liquid crystal panel realizes time-sharing receiving of optical signals in different areas by controlling the transmittance change of different areas; the rotating wheel is used for homogenizing the transmitted light signals; the optical detector is used for receiving the transmitted light signal after light homogenization and converting the received light signal into an electric signal;
the signal processing module comprises a signal amplifying circuit, an A/D sampling circuit and a signal processing circuit which are connected in sequence; the signal amplifying circuit is connected with the optical detector and is used for amplifying the received electric signals; the A/D sampling circuit is used for sampling the amplified electric signals in different areas to obtain amplitude information of multiple paths of signals, further calculating the light spot intensity falling into each area, and then obtaining the light spot position of the incident light; the signal processing circuit calculates the incident angle and the direction component of the incident light according to the received light spot position of the incident light, and controls the mechanical servo module to deflect corresponding angles according to the incident angle and the direction component so as to realize alignment.
Further, in the system, the deflection execution amount of the mechanical servo module is transmitted to the mechanical servo driving module, the mechanical servo module drives the mechanical servo module according to the deflection execution amount data, and the mechanical servo module controls the optical receiving module to rotate, so that an incident light spot falls into the optical center position (the center of the transmission type liquid crystal panel and the center of the optical detector) of the optical receiving module, and the laser communication is realized, and the specific process is as follows:
the mechanical servo module is connected with the signal processing module, and the signal processing module outputs deflection execution amount information of the mechanical servo module and transmits the deflection execution amount information to the mechanical servo driving module;
the mechanical servo driving module receives the deflection executing information and generates a certain time sequence pulse signal according to the deflection executing information so as to control the mechanical servo module;
the mechanical servo module is connected with the mechanical servo driving module and used for receiving deflection execution information from the mechanical servo driving module and controlling the optical receiving module to rotate;
the optical receiving module is connected with the mechanical servo module, and the mechanical servo module drives the optical receiving module to deflect so that an incident light spot falls into the optical center position (the center of the transmission type liquid crystal panel and the center of the optical detector) of the optical receiving module;
after the optical receiving module deflects to realize laser alignment, the electric control zoom lens focuses on the receiving surface of the point detector, and the rotating wheel is controlled to enable light to directly pass through without light homogenizing, so that laser communication tracking and positioning are realized.
Further, the transmissive liquid crystal panel includes a liquid crystal driving module whose power supply is varied at time intervals t, thereby realizing transmittance variation of A, B, C, D four quadrants in the transmissive liquid crystal panel.
Further, the optical lens adopts an electric control zoom lens; in the tracking stage, the focal length of the electric control zoom lens is controlled to be equal to the distance between the transmission type liquid crystal panel and the electric control zoom lens; in the communication stage, the focal length of the electronically controlled zoom lens is controlled to be equal to the distance between the transmission type liquid crystal panel and the optical detector.
Further, the rotating wheel consists of two equally divided semicircular wheels, one semicircular wheel consists of an optical scattering sheet, the other semicircular wheel is an optical full-transparent glass sheet, and no scattering effect is caused on light.
Compared with the prior art, the technical scheme provided by the invention has the following beneficial effects:
the system uses a transmission type liquid crystal panel to replace a four-quadrant detector, and is matched with a rotating wheel and an optical detector to serve as an optical receiving unit; the four areas of the transmission type liquid crystal panel are controlled to periodically transmit light, and the light is homogenized through the rotating wheel and falls into the optical detector; the system can work in two working modes of light spot positioning and communication, solves the problem that the four-quadrant detector can only be used as a position sensitive detector, reduces the production cost and simplifies the communication system composition. The transmission type liquid crystal panel is divided for multiple times, so that the effectiveness of light spot positioning can be ensured, and the problem that the four-quadrant detector fails when light spots are positioned at one or two image points can be solved. Meanwhile, the received optical signals are converted into electric signals by utilizing an optical detector, and the electric signals are processed by a signal amplifying circuit, an A/D sampling circuit and a signal processing circuit in sequence, so that the spot position of the incident light and the deflection execution amount of the mechanical servo module are calculated and obtained; and the deflection execution amount is fed back to the mechanical servo driving module, and the mechanical servo driving module generates a time sequence pulse signal according to the received deflection execution amount to control the mechanical servo module to act and further control the optical receiving module to rotate so as to ensure that incident light falls into the center position of the optical detector and complete tracking.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate principles of the invention and together with the description, serve to explain the principles of the invention.
In order to more clearly illustrate the embodiments of the invention or the technical solutions of the prior art, the drawings which are used in the description of the embodiments or the prior art will be briefly described, and it will be obvious to a person skilled in the art that other drawings can be obtained from these drawings without inventive effort.
FIG. 1 is a flow chart of a wireless optical communication tracking and positioning method provided by the invention;
FIG. 2 is a schematic block diagram of a wireless optical communication tracking and positioning system provided by the invention;
FIG. 3 is a schematic view of a rotor structure according to the present invention;
fig. 4 is a schematic diagram of a transmissive liquid crystal panel according to the present invention;
fig. 5 (a) and fig. 5 (b) are schematic diagrams of four-quadrant detection of a transmissive liquid crystal panel according to embodiment 1 of the present invention;
fig. 6 is a schematic diagram of four area detection of a transmissive liquid crystal panel according to embodiment 2 of the present invention;
FIG. 7 (a) is a schematic diagram of a four-quadrant detection method according to embodiment 3 of the present invention;
fig. 7 (b) is another schematic diagram of subdivision four-quadrant detection provided in embodiment 3 of the present invention.
Detailed Description
Reference will now be made in detail to exemplary embodiments, examples of which are illustrated in the accompanying drawings. When the following description refers to the accompanying drawings, the same numbers in different drawings refer to the same or similar elements, unless otherwise indicated. The implementations described in the following exemplary examples do not represent all implementations consistent with the invention. Rather, they are merely examples of systems, methods, and so forth that are consistent with aspects of the invention as detailed in the accompanying claims.
The present invention will be described in further detail below with reference to the drawings and examples for better understanding of the technical solutions of the present invention to those skilled in the art.
Example 1
Referring to fig. 1, the embodiment provides a wireless optical communication tracking and positioning method, which specifically includes:
s1, realizing time-sharing receiving of incident light in different areas, and converting a received optical signal into an electric signal;
s2, processing the electric signals, and calculating the spot position and deviation angle information of incident light to obtain deflection execution quantity;
and step S3, carrying out posture adjustment on the optical receiving module according to the deflection execution amount so as to ensure that the optical receiving module is aligned with the received light and realize laser communication.
Further, in the step S1, time-sharing receiving of the incident light in different areas is implemented, which specifically includes:
s1.1, incident light is converged to a transmission type liquid crystal panel through an optical lens;
s1.2, realizing time-sharing receiving of incident light in different areas by controlling the transmittance change of different areas of the transmission type liquid crystal panel; the different areas comprise A, B, C, D quadrants which are mutually isolated, equal in area, identical in shape and symmetrical in position and divide the transmission type liquid crystal panel.
Further, the step S2 specifically includes:
s2.1, amplifying the electric signal by a signal amplifying circuit;
s2.2, sampling the amplified electric signals by an A/D sampling circuit and calculating the light spot intensities of different areas;
and S2.3, calculating the spot position and the deviation angle information of the incident light according to the spot intensity.
Further, as shown in fig. 5, the step S2.3 specifically includes:
s2.3.1, converging the incident light by an optical lens, focusing the incident light into light spots on a plane where the transmissive liquid crystal panel is located, dividing the laser to be measured by the transmissive liquid crystal panel through A, B, C, D four quadrants, converting the received light intensity into photocurrents, and recording the photocurrents as I A 、I B 、I c 、I D The magnitude of the photocurrent is in direct proportion to the light spot area and the illumination intensity;
step S2.3.2, calculating relative offsets Δx and Δy of the light spot center on the transmissive liquid crystal panel, where the calculation formula is as follows:
k is a coefficient, where k in this embodiment is equal to a radius of a light spot on a plane of the transmissive liquid crystal panel;
step S2.3.3, calculating the included angle θ between the incident light and the optical axis according to the relative offsets Δx and Δy, and recording the included angles between the projection light of the incident light on the xoz plane and the projection light of the incident light on the yoz plane and the optical axis as Δθ respectively x 、△θ y The included angles theta and delta theta x 、△θ y The calculation formulas of (a) are respectively as follows:
Δθ x ＝arctan(Δx/f)
Δθ y ＝arctan(Δy/f)
wherein f is the distance between the transmissive liquid crystal panel and the optical lens.
Further, the step S3 specifically includes:
s3.1, transmitting the deflection execution amount into a mechanical servo driving module, and generating a time sequence pulse signal to control the mechanical servo module to act according to the received deflection execution amount by the mechanical servo driving module;
s3.2, the mechanical servo module controls the optical receiving module to rotate according to the received deflection execution amount so as to ensure that incident light falls into the optical center (the center of the transmission type liquid crystal panel and the center of the optical detector) of the optical receiving module;
step S3.3, controlling the focal length of the electric control zoom lens through voltage to enable the focal length to be equal to the distance between the transmission type liquid crystal panel and the optical detector; the rotating wheel is rotated to enable incident light to pass through the full-transmission area to reach the optical detector, and the system enters a communication stage.
Example 2
On the basis of embodiment 1, this embodiment also provides a wireless optical communication tracking positioning method, which is different from embodiment 1 in the calculation process of step S2.3.
The transmissive liquid crystal panel is divided into four new areas A1, B1, C1 and D1, and the coordinates in the four new areas form an included angle of 45 ° with the original coordinates (four-quadrant coordinates), as shown in fig. 6. The transmittance of four areas A1, B1, C1, D1 in the period T is 0: i.e. between 0 and t 1 The transmittance of the area A1 of the transmission type liquid crystal panel is controlled to be 0 in a time period, and the transmittance of the areas B1, C1 and D1 are all 1; at t 1 -t 2 The transmittance of the B1 region of the transmission type liquid crystal panel is controlled to be 0 in a time period, and the transmittance of the A1 region, the C1 region and the D1 region of the transmission type liquid crystal panel are all 1; at t 2 -t 3 The transmittance of the C1 area of the transmission type liquid crystal panel is controlled to be 0 in a time period, and the transmittance of the A1 area, the B1 area and the D1 area are all 1; at t 3 -t 4 The transmittance of the region of the time zone control transmission type liquid crystal panel D1 is 0, and the transmittance of the regions A1, B1 and C1 are all 1.
The step S2.3 specifically includes:
s2.3.1, converging the incident light through an optical lens, focusing the incident light into light spots on a plane where a transmissive liquid crystal panel is located, dividing the laser to be measured by the transmissive liquid crystal panel through four quadrants A1, B1, C1 and D1, converting the received light intensity into photocurrents, and recording the photocurrents as I respectively 1 、I 2 、I 3 、I 4 The magnitude of the photocurrent is in direct proportion to the light spot area and the illumination intensity;
step S2.3.2, calculating relative offsets Δx and Δy of the light spot center on the transmissive liquid crystal panel, where the calculation formula is as follows:
where k is a coefficient, and in this embodiment, k is equal to the spot diameter on the plane of the transmissive liquid crystal panel.
It should be noted that the size and resolution of the transmissive liquid crystal panel can be selected according to the area of the incident light spot. The light spot positioning algorithm is similar to a diagonal algorithm, and the sensitivity is high when the light spot is positioned at the center of the light spot.
Example 3
On the basis of embodiment 1, this embodiment also provides a system applying the above wireless optical communication tracking positioning method, and, as shown in fig. 2, the system includes an optical transmitting device, an optical receiving module for receiving an optical signal, and a signal processing module connected to the optical receiving module, where the signal processing module is sequentially connected to the optical receiving module through a mechanical servo driving module and a mechanical servo module.
Further, the light emitting device adopts an incoherent light source such as laser or LED, preferably a 532nm LD light source, and blue-green light is located in an optical window in an underwater environment and is usually used as an emitting light source in the field of underwater wireless optical communication.
Further, the optical receiving module is used for focusing and time-sharing receiving of the laser to be detected and comprises an optical lens, a transmission type liquid crystal panel, a rotating wheel and an optical detector which are distributed in sequence;
preferably, the optical lens adopts an electrically controlled zoom lens, and the light source to be tested is focused in the area of the transmission type liquid crystal panel in the extraction stage, and the working principle is as follows: in an underwater wireless optical communication link, the laser beam to be measured is approximately parallel light when reaching a receiving end. The parallel light to be measured passes through the electric control zoom lens, and the optical transmission line is changed. The laser passing through the center of the lens has small change, the light near the edge is refracted towards the axial direction of the lens, and finally the laser to be measured forms a light spot to be mapped in the receiving plane of the transmission type liquid crystal panel.
Preferably, a transmissive liquid crystal panel is employed as the electro-optical elementThe position sensitive receiving device, as shown in fig. 5 (a), divides the whole transmissive liquid crystal panel into four quadrants when tracking the spot position for the first time, and realizes time-sharing receiving by adjusting, as shown in fig. 5 (b), at 0-t 1 ，t 1 -t 2 ,t 2 -t 3 ,t 3 -t 4 In the time period, the A, B, C, D quadrants respectively and sequentially enable light rays to pass through, so that the light signals in different quadrants are received, and the specific process is as follows:
firstly, controlling the power supply of the liquid crystal driving module to change at time t, wherein t=t 1 -0＝t 2 -t 1 ＝t 3 -t 2 ＝t 4 -t 3 ，T＝t 4 -0 the supply voltage varies periodically with T;
the transmissivity of the four quadrants of the transmissive liquid crystal panel A, B, C, D is controlled to change by utilizing the power supply of the liquid crystal driving module, and the transmissivity is changed within 0-t 1 The transmittance of the A quadrant of the transmission type liquid crystal panel is controlled to be 1, and the transmittance of the B and C, D areas is controlled to be 0 in a time period; at t 1 -t 2 The transmittance of the B quadrant of the transmission type liquid crystal panel is controlled to be 1 in a time period, and the transmittance of the A and C, D areas is controlled to be 0; at t 2 -t 3 The transmission rate of the C quadrant of the transmission type liquid crystal panel is controlled to be 1 in a time period, and the transmission rate of the A and B, D areas is controlled to be 0; at t 3 -t 4 The transmission rate of the D quadrant of the transmission type liquid crystal panel is controlled to be 1 in a time period, and the transmission rate of the A and B, C areas is controlled to be 0;
after a period T, the entire liquid crystal plane receives the optical signal completely, because the voltage change time interval is short, and the optical signals received by the four quadrants can be regarded as components of the same light beam. Specifically, the receiving principle of the transmissive liquid crystal panel is as follows: the transmissive liquid crystal panel is in effect an amplitude type spatial light modulator (Spatial Light Modulator, SLM). The liquid crystal panel material has an electro-optical property, and can modulate the amplitude of light when a voltage is applied to the liquid crystal panel. The liquid crystal material commonly used is enclosed between two glass substrates coated with a transparent conductive film, a device called a liquid crystal cell, the principle of which is shown in fig. 4.
When a linearly polarized light passes through the liquid crystal cell, the polarization direction will be along with the twist state of the liquid crystal moleculesWhen a constant voltage is applied to the substrates, the liquid crystal molecules are deflected in the longitudinal direction, and the vibration direction of the linearly polarized light changes with the change of the deflection angle. In this way, first, a polarizer and an analyzer are placed on both sides of the liquid crystal cell, and the polarization directions of the polarizer and the analyzer are perpendicular to each other, as shown in figure 4,the amplitude modulation of the light can be achieved by controlling the amount of voltage applied across the cell to control the light passing rate. When no electric field is applied, the emergent light intensity is weakest, when a certain electric field is applied, the liquid crystal molecules incline along the direction of the electric field, the polarization direction of the light also deflects along the direction of the liquid crystal molecules, at the moment, the polarization direction of the light is no longer perpendicular to the polarization analyzer, certain light can penetrate the polarization analyzer, and the intensity of the light changes along with the size of the electric field.
Further, the signal processing module comprises a signal amplifying circuit, an A/D sampling circuit and a signal processing circuit which are connected in sequence, and the analog-to-digital conversion of the measurement signal and the calculation of the position and the deviation angle of the light spot are mainly completed. Specifically, the signal amplifying circuit is connected with the optical detector and is used for amplifying the received electric signal; the A/D sampling circuit is used for sampling the amplified electric signals in different areas to obtain amplitude information of multiple paths of signals, further calculating the light spot intensity falling into each area, and then obtaining the light spot position of the incident light; the signal processing circuit calculates the incident angle and the direction component of the incident light according to the received light spot position of the incident light, and controls the mechanical servo module to deflect by a corresponding angle (namely, the deflection execution amount) according to the incident angle and the direction component, thereby controlling the laser probe in the optical receiving module to adjust the gesture and ensuring that the incident light falls into the optical center position (the center of the transmission type liquid crystal panel and the center of the optical detector) of the optical receiving module.
Preferably, in the optical communication system, the light intensity input by the receiving end sometimes does not meet the requirement of signal acquisition, and the signal amplifying circuit amplifies the photocurrent signal output by the optical detector (which converts the optical signal into a voltage signal), so as to improve the adaptability of the whole communication system. The signal amplifying circuit must be a low noise amplifying device in consideration of the very small received signal during long-range communication.
In summary, the system based on the wireless optical communication tracking and positioning method has the following specific working procedures:
step I, incident light rays (laser light sources) are converged into a transmission type liquid crystal panel through an electric control zoom lens, a liquid crystal driving module controls the transmittance of four quadrants of the liquid crystal panel A, B, C, D to change rapidly, a rotating wheel (a scattering sheet is adopted and is combined with the view shown in fig. 3) is started to work so as to homogenize transmission light signals, and four paths of light intensity signals received by an optical detector (a point detector) can be regarded as light signals of the same light beam and the same time;
step II, the point detector transmits the received electric signals to a signal processing module to realize the processing of mechanical servo deflection execution data and communication related data in the amplifying, collecting, facula position calculating and tracking stages of the electric signals, namely four paths of light intensity signals are amplified by a signal amplifying circuit, the facula intensities of four quadrants of A, B, C, D are acquired and calculated by an A/D sampling circuit, the facula center position and the optical system parameter information are calculated according to an azimuth calculation method, and the signal processing circuit calculates incidence deflection angle information according to the facula position and the optical system parameter information of incident light to obtain the mechanical servo deflection execution quantity;
step III, transmitting the mechanical servo deflection execution amount information to a mechanical servo control module to obtain a certain time sequence pulse signal to control the mechanical servo module to deflect;
IV, the mechanical servo module drives the optical receiving module to deflect, so that a point detector in the optical receiving module is aligned to the incident light direction, and a light spot falls into the center of the transmission type liquid crystal panel;
and V, aligning the laser probe with the optical receiving module, focusing the electric control zoom lens on the optical detector, and controlling the rotating wheel to enable light to directly pass through without uniform light so as to perform optical communication.
In some embodiments, the specific steps of the step ii are as follows:
II-1, the electric signal received by the point detector is firstly transmitted to a signal amplifying circuit to amplify the signal so as to adapt to the requirement of a subsequent signal processing circuit;
II-2, a signal processing circuit samples the amplified light intensity signals of four quadrants A, B, C, D to obtain amplitude information of the four paths of signals, calculates the light spot intensity falling into each quadrant, and calculates the light spot position and the deflection angle information of the incident laser according to an azimuth calculation method;
and II-3, processing the obtained spot position information and the optical system parameters, and calculating the incidence angle and the direction component of the beam with measurement to obtain the deflection execution quantity of the mechanical servo module.
Specifically, if the four quadrant light spot intensities collected in step ii-2 are all not zero (i.e. the light spot falls into four quadrants), and the three quadrant light spot intensities are all not zero (i.e. the light spot falls into three quadrants), tracking and positioning are performed according to the conventional tracking method, and the subsequent steps (step iii, step iv, and step v) are sequentially executed.
If the light spot intensity in the four quadrants acquired in the step II-2 is not 0, the light spot falls into one of the four quadrants; or if the two values of the light spot intensities in the four quadrants acquired in the step II-2 are not 0, the light spot falls into a certain two quadrants (adjacent) in the four quadrants, and tracking is continued, specifically:
II-2-1, dividing the single quadrant or two adjacent quadrants where the light spots fall into four quadrants again, controlling the single quadrant of the subdivided four quadrants to periodically transmit light, and calculating the specific position of the light spots in the original single quadrant or two adjacent quadrants;
step II-2-2, if the light spots are distributed in a single quadrant or each quadrant (four quadrants after subdivision) of two adjacent quadrants, entering step II-3 and sequentially executing subsequent steps (step III, step IV and step V); if the light spots are still distributed in a single quadrant or two quadrants of the subdivided four quadrants, repeating the step II-2-1 until the light spots fall into each quadrant of the newly subdivided four quadrants, entering the step II-3, and sequentially executing the subsequent steps (step III, step IV and step V).
In order to better understand the continuous tracking process, the example of a spot falling in quadrant a and the example of a spot falling in quadrant A, B are described.
(1) The light spot falls into quadrant a: in step ii-2, the spot detector receives a quadrant spot with an intensity value other than 0, and the other three quadrants have intensity values all zero, see fig. 7 (a), and the specific tracking process is as follows:
(a) In the primary light spot position tracking process, a signal processing module calculates and obtains I in four paths of light intensity signals A ＞0、I B ＝I C ＝I D =0, then the spot falls completely in quadrant a;
(b) Taking the position center point of the quadrant A as the origin of coordinates, subdividing the coordinate into four quadrants, namely 1, 2, 3 and 4 quadrants, and periodically transmitting light for position tracking in the four quadrants as shown in fig. 7 (a); when the spot position is calculated, the offset of the spot relative to the center position of the quadrant a needs to be added to the offset of the spot relative to the entire transmissive liquid crystal panel, namely:
Δx＝Δx a +a
Δy＝Δy a +b
in the above, deltax a And Deltay a The position offset of the subdivision four-quadrant division of the A quadrant is that of the central position of the A quadrant.
(c) If the light spot falls into four sub-quadrants (1, 2, 3 and 4), executing the step II-3 and executing the subsequent steps (step III, step IV and step V) in sequence to rotate the optical receiving module; if the light spot still falls into a single quadrant or two quadrants, the quadrants of the quadrants are re-performed until the light spot falls into each quadrant of the next subdivided four quadrants, the optical receiving module rotates, tracking is finished, and laser communication is performed.
(2) The spot falls into quadrant A, B: in step II-2, the spot detector receives a light spot with a light spot intensity value of A, B quadrant which is not zero and a light spot with a light spot intensity value of C, D quadrant which is zero, and the light spot falls between two quadrants, namely adjacent A, B quadrants, as shown in fig. 7 (b); during primary spot position tracking, one of the spot center positions x or y can be determined, and then four-quadrant segmentation is performed on two quadrants to perform position tracking, wherein the specific tracking process is as follows:
(d) The light spot falls into A, B quadrant I A ＞0、I B ＞0，I C ＝I D =0, i.e. the spot is on the y-axis positive half-axis;
(e) The offset delta x of the central position of the light spot relative to the y axis is calculated during the primary light spot position tracking, the A, B quadrant is further subdivided into four quadrants (5, 6, 7 and 8 quadrants), and the four quadrants periodically transmit light for position tracking;
(f) The calculation of the light spot position is carried out, and the offset of the light spot relative to the y-axis on the whole liquid crystal panel is added with the offset of the center position of the AB quadrant, namely:
Δy＝Δy a +b
Δy a for the position offset of four-quadrant segmentation by using the AB quadrant, b is the offset of the central position of the AB quadrant relative to the x-axis;
(g) If the light spot falls into four sub-quadrants (5, 6, 7 and 8), executing the step II-3 and sequentially executing the subsequent steps (step III, step IV and step V) to rotate the optical receiving module; if the light spot still falls into a single quadrant or two quadrants, the quadrants of the quadrants are re-performed until the light spot falls into each quadrant of the next subdivided four quadrants, the optical receiving module rotates, tracking is finished, and laser communication is performed.
In summary, the system provided by the invention uses a transmission type liquid crystal panel to replace a four-quadrant detector, and is matched with a rotating wheel and an optical detector to serve as an optical receiving unit; the four areas of the transmission type liquid crystal panel are controlled to periodically transmit light, and the light is homogenized through the rotating wheel and falls into the optical detector; the problem that the four-quadrant detector can only be used as a position sensitive detector is solved, and the production cost is reduced. Meanwhile, the received optical signals are converted into electric signals by utilizing an optical detector, and the electric signals are processed by a signal amplifying circuit, an A/D sampling circuit and a signal processing circuit in sequence, so that the spot position of the incident light and the deflection execution amount of the mechanical servo module are calculated and obtained; and feeding back the deflection execution amount to the mechanical servo driving module, and generating a time sequence pulse signal according to the received deflection execution amount by the mechanical servo driving module to control the mechanical servo module to act so as to further control the rotation of the optical receiving module, thereby ensuring that incident light falls into the optical center position of the optical receiving module and completing tracking.
The foregoing is only a specific embodiment of the invention to enable those skilled in the art to understand or practice the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention.
It will be understood that the invention is not limited to what has been described above and that various modifications and changes may be made without departing from the scope thereof. The scope of the invention is limited only by the appended claims.
Claims (10)
1. The wireless optical communication tracking and positioning method is characterized by comprising the following steps:
s1, realizing time-sharing receiving of incident light in different areas, and converting a received optical signal into an electric signal;
s2, processing the electric signals, and calculating the spot position and deviation angle information of incident light to obtain deflection execution quantity;
and step S3, carrying out posture adjustment on the optical receiving module according to the deflection execution amount so as to ensure that the optical receiving module is aligned with incident light and realize laser communication.
2. The method of claim 1, wherein the step S1 is implemented to receive the incident light in different areas in a time-sharing manner, and specifically includes:
s1.1, incident light is converged to a transmission type liquid crystal panel through an optical lens;
s1.2, realizing time-sharing receiving of incident light in different areas by controlling the transmittance change of different areas of the transmission type liquid crystal panel; the different areas comprise four areas which are mutually isolated, equal in area, identical in shape and symmetrical in position and divide the transmission type liquid crystal panel.
3. The method for tracking and positioning wireless optical communication according to claim 1, wherein the step S2 specifically includes:
s2.1, amplifying the electric signal by a signal amplifying circuit;
s2.2, sampling the amplified electric signals by an A/D sampling circuit and calculating the light spot intensities of different areas;
and S2.3, calculating the spot position and the deviation angle information of the incident light according to the spot intensity.
4. The wireless optical communication tracking positioning method according to claim 3, wherein the step S2.3 specifically includes:
s2.3.1, converging the incident light by an optical lens, focusing the incident light into light spots on a plane where the transmissive liquid crystal panel is located, dividing the laser to be measured by the transmissive liquid crystal panel through A, B, C, D four quadrants, converting the received light intensity into photocurrents, and recording the photocurrents as I A 、I B 、I c 、I D The magnitude of the photocurrent is in direct proportion to the light spot area and the illumination intensity;
step S2.3.2, calculating relative offsets Δx and Δy of the light spot center on the transmissive liquid crystal panel, where the calculation formula is as follows:
wherein k is a coefficient;
step S2.3.3, calculating the included angle θ between the incident light and the optical axis according to the relative offsets Δx and Δy, and recording the included angles between the projection light of the incident light on the xoz plane and the projection light of the incident light on the yoz plane and the optical axis as Δθ respectively x 、△θ y The sum ofThe included angles theta and delta theta x 、△θ y The calculation formulas of (a) are respectively as follows:
Δθ x ＝arctan(Δx/f)
Δθ y ＝arctan(Δy/f)
wherein f is the distance between the transmissive liquid crystal panel and the optical lens.
5. The method according to claim 1, wherein the step S3 of performing posture adjustment on the optical receiving module according to the deflection execution amount to ensure alignment between the optical receiving module and the received light, specifically comprises:
s3.1, transmitting the deflection execution amount into a mechanical servo driving module, and generating a time sequence pulse signal to control the mechanical servo module to act according to the received deflection execution amount by the mechanical servo driving module;
and S3.2, the mechanical servo module controls the optical receiving module to rotate according to the received deflection execution amount so as to ensure that the incident light spots fall into the optical center of the optical receiving module.
6. A system for applying the wireless optical communication tracking and positioning method according to any one of claims 1 to 5, wherein the system comprises an optical receiving module for receiving an optical signal, and a signal processing module connected with the optical receiving module, and the signal processing module is connected with the optical receiving module sequentially through a mechanical servo driving module and a mechanical servo module;
the optical receiving module comprises an optical lens, a transmission type liquid crystal panel, a rotating wheel and an optical detector which are distributed in sequence:
the optical lens is used for converging incident light into the transmission type liquid crystal panel in the extraction stage; for converging incident light to an optical detector during a communication phase;
the transmission type liquid crystal panel realizes time-sharing receiving of optical signals in different areas by controlling the transmittance change of different areas;
the rotating wheel is used for homogenizing the transmitted light signals;
the optical detector is used for receiving the transmitted light signal after light homogenization and converting the received light signal into an electric signal;
the signal processing module comprises a signal amplifying circuit, an A/D sampling circuit and a signal processing circuit which are connected in sequence:
the signal amplifying circuit is connected with the optical detector and is used for amplifying the received electric signals;
the A/D sampling circuit is used for sampling the amplified electric signals in different areas to obtain amplitude information of multiple paths of signals, further calculating the light spot intensity falling into each area, and then obtaining the light spot position of the incident light;
the signal processing circuit calculates the incident angle and the direction component of the incident light according to the received light spot position of the incident light, and controls the mechanical servo module to deflect corresponding angles according to the incident angle and the direction component so as to realize alignment.
7. The system of claim 6, wherein the transmissive liquid crystal panel comprises a liquid crystal drive module, a power supply of the liquid crystal drive module being varied at time intervals t to enable transmittance variation of four regions A, B, C, D in the transmissive liquid crystal panel.
8. The system of claim 6, wherein the wheel is comprised of equally divided two half-round wheels, one half-round wheel being comprised of an optical diffuser and the other half-round wheel being an optical full-transmission glass sheet.
9. The system of claim 6, wherein the optical lens employs an electronically controlled zoom lens.
10. The system of claim 9, wherein the system comprises two modes of operation: the tracking stage and the communication stage, wherein in the tracking stage, the focal length of the electric control zoom lens is controlled to be equal to the distance between the transmission type liquid crystal panel and the electric control zoom lens; in the communication stage, the focal length of the electronically controlled zoom lens is controlled to be equal to the distance between the transmission type liquid crystal panel and the optical detector.
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