A method for positioning and anomaly detection of a separated coupled cavity laser system

Abstract

The application relates to a positioning and anomaly detection method of a separated coupled cavity laser system, the separated coupled cavity laser system comprising a transmitting end and multiple receiving ends, the method comprising the following steps: S1, controlling a pump source to emit laser; S2, setting the pump source to emit low-power laser, and acquiring ID information of all the receiving ends; S3, performing handshaking; S4, setting the pump source to emit high-power laser, and splitting the laser; S5, calculating the distance between the transmitting end and the receiving end based on a ToF measurement module; S6, determining the actual arrival angle alpha2 of the receiving end according to an AOA measurement module; and S7, positioning the receiving end according to the distance measured in S5 and the arrival angle alpha2, and simultaneously detecting the abnormal state in the transmission channel when the transmitting end and the receiving end are relatively static. Compared with the prior art, the application has the advantages of realizing one-to-many energy transmission, communication and positioning, supporting intelligent control and detection of the transmitting end on the multiple receiving ends and the like.

Description

Technical Field

[0001] This invention relates, and in particular, to a method for positioning and anomaly detection in a split-cavity laser system. Background Technology

[0002] In complex and dynamic scenarios, intelligent perception and collaboration of unmanned devices such as drones, industrial robots, and modular satellites are key research areas in wireless ad hoc networks and autonomous intelligent systems. These areas particularly focus on how to ensure the energy expenditure required for a single node to maintain its computing and communication capabilities, and how to achieve high-precision, high-dynamic, autonomous collaboration among heterogeneous nodes. The fundamental research and technologies involved mainly include new methods and systems for "energy transmission, communication, perception, and positioning" based on acoustic, electronic, and optical (visual / laser) technologies.

[0003] For the application requirement of "high-power, high-security self-aligned power transfer positioning from 'easily accessible energy nodes' to 'difficult-to-access energy nodes'", traditional research mainly focuses on two aspects: "power transfer and communication integration" and "communication and positioning integration", with less attention paid to power transfer and positioning integration. Research on power transfer and communication integration primarily focuses on wireless power-carrying communication technologies emphasizing communication, with less research on technologies that simultaneously transmit energy information. Research on communication and positioning integration has attracted widespread interest from industry and academia with the development of sensor integration, and is generally divided into communication-assisted positioning and positioning-assisted communication. However, the above research cannot meet the following requirement: high-power, high-security self-aligned power transfer positioning from "easily accessible energy nodes" to "difficult-to-access energy nodes".

[0004] In recent years, intracavity laser wireless transmission technology has made progress in high-power energy transmission and simultaneous data and energy transmission. Furthermore, the sensitive response of intracavity lasers to foreign objects also gives them significant sensing and measurement capabilities. However, existing related work either relies on approximate modeling based on an external cavity mirror with extremely low reflectivity (weak feedback condition), which does not conform to the typical structural characteristics of a split-coupled-cavity laser system (the external cavity mirror has relatively high reflectivity, constituting a strong feedback condition); or it employs a non-split structure (the external cavity is located at the transmitter), using external laser ranging, which makes it difficult to guarantee laser radiation safety. Secondly, the relevant positioning methods are not closely integrated with the theoretical analysis model of intracavity laser transmission in free space, and have high requirements for an interference-free environment, failing to effectively solve the problem of positioning using intracavity lasers in complex dynamic scenarios. Summary of the Invention

[0005] The purpose of this invention is to provide a positioning and anomaly detection method for a split-coupled cavity laser system to solve the problem of positioning using intracavity lasers in complex dynamic scenarios.

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] A method for localization and anomaly detection in a split-cavity laser system is disclosed. The split-cavity laser system includes a transmitter and multiple receivers. The main resonant cavity is located at the transmitter, and the free-space resonant cavity is located between the transmitter and receivers. The transmitter is equipped with an image sensor, an ID demodulation module, a retroreflector, a polarization modulator, a polarization beam splitter, a beam splitter, an AOA measurement module, and a ToF measurement module. The receivers are equipped with an LCD shutter modulator, a retroreflector, an energy receiver, and a microprocessor.

[0008] The method includes the following steps:

[0009] S1. Control the pump source to emit laser light. The laser light propagates in the main resonant cavity through the retroreflector. A gain medium is placed between the retroreflectors on both sides of the main resonant cavity. After passing through the main resonant cavity, the laser light enters the free space resonant cavity and propagates between the transmitting end and the receiving end of the free space resonant cavity through the retroreflector. At the same time, it is emitted towards the outside of the free space resonant cavity at the receiving end.

[0010] S2. Set the pump source to emit low-power laser, apply voltage to the LCD shutter modulator, and by changing the voltage, each LCD shutter modulator sends a modulation signal with the corresponding ID information of the corresponding receiver. The transmitter obtains the ID information of all receivers based on the presence or absence of the laser spot in the free space resonant cavity received by the image sensor and the demodulation of the modulation signal by the ID demodulation module.

[0011] S3. Determine whether the receiving end corresponding to the ID information is an authorized target receiving end. If so, continue to communicate with the receiving end and complete the handshake. Otherwise, stop communicating with the receiving end. For authorized target receiving ends, execute S4.

[0012] S4. Set up a pump source to emit a high-power laser. The transmitting end acquires the intracavity laser of the free space resonant cavity emitted by the target receiving end. The intracavity laser passes through a polarization modulator and a polarization beam splitter and is divided into a reference signal X(t) and a signal to be measured Y(t). The signal to be measured Y(t) passes through the beam splitter, with one part entering the ToF measurement module and the other part entering the image sensor.

[0013] S5. Calculate the cross-correlation function between the reference signal X(t) and the signal Y(t) to be measured based on the ToF measurement module, extract the time delay corresponding to the peak value in the cross-correlation curve, and obtain the distance L2 between the transmitter and receiver.

[0014] S6, the AOA measurement module calculates the theoretical field of view of the transmitter based on the analysis model of the split-coupled cavity laser system, determines the mapping relationship between the field of view and the pixel position of the image sensor, obtains the pixel position of the centroid of the laser spot by the algorithm of the intracavity laser spot and the centroid of the spot actually perceived on the image sensor, and determines the actual angle of arrival α2 of the receiver based on the mapping relationship.

[0015] S7. Based on the distance L2 measured in S5 and the actual angle of arrival α2 corresponding to the receiver, locate the receiver. Simultaneously, substitute the distance L2 and angle of arrival α2 into the analysis model of the split-coupled cavity laser system to determine the theoretically corresponding parameters of the analysis model. Compare the theoretical parameters with the actual parameters measured by the image sensor, AOA measurement module, ToF measurement module, and power meter to detect abnormal states in the transmission channel when the transmitter and receiver are relatively stationary. The theoretically corresponding parameters include the output power.

[0016] Furthermore, the analytical model of the split-coupled cavity laser system includes four retroreflectors, which are divided into two groups of two. The first group of retroreflectors forms the main resonant cavity corresponding to the main resonant cavity of S1, and the second group of retroreflectors forms the free space resonant cavity corresponding to the free space resonant cavity of S1.

[0017] Each retroreflector consists of a plane mirror and a lens.

[0018] Furthermore, the theoretical field of view FoV ∈ (-α) at ​​the transmitter 2,max α 2,max ), α2 represents the incident angle of the laser in the free-space resonant cavity, i.e., the angle of arrival, α 2,max The maximum range of α2 is represented by the following process for calculating the theoretical field of view of the transmitter:

[0019] The first step is to determine the pump power P when the pump source emits high-power laser light. in ;

[0020] The second step is to search for the output laser power P. out The angle reached when = 0;

[0021] The third step is to determine the theoretical field of view (FoV) of the transmitter based on the angle of arrival obtained from the search.

[0022] Furthermore, in the analysis model, the intracavity laser of the main resonant cavity is projected onto the image sensor with an incident angle of α1. At this time, the mapping relationship between the field of view and the pixel position of the image sensor is determined based on the incident angle α1 and the distance from the beam splitter to the image sensor.

[0023] Furthermore, after calculating the theoretical field of view in S6, it is determined whether the sensing range of the image sensor is greater than the theoretical field of view. If so, S6 continues to be executed; otherwise, the sensing range of the image sensor is adjusted until it is greater than the theoretical field of view.

[0024] Furthermore, the cross-correlation function is:

[0025]

[0026] in, This represents the cross-correlation operation, where k is the normalization coefficient, δ represents the cross-correlation curve function between the reference signal and the signal under test, and R... xy (τ) represents the cross-correlation function, τ represents the time delay, X(t) represents the reference signal, and Y(t) represents the signal to be measured.

[0027] Furthermore, the distance between the transmitter and receiver is:

[0028] L2=cτ / 2n air

[0029] Where c is the speed of light, n air τ is the refractive index in the optical path of the free-space resonant cavity, and τ represents the time delay.

[0030] Furthermore, after the handshake, the laser beam outside the free-space resonant cavity of the receiving end is directed towards the information receiver of the transmitting end. The microprocessor obtains information from the transmitting end based on the information receiver of the transmitting end. The energy receiver connects the microprocessor and the information receiver of the transmitting end. The energy receiver receives the energy of the laser beam outside the cavity and supplies power to the microprocessor and the information receiver of the transmitting end.

[0031] Furthermore, after comparing the actual and measured parameters, if an anomaly occurs in the transmission channel when the transmitter and receiver are relatively stationary, a control signal is sent to the gain medium or polarization modulator at the transmitter to control the pump power supplied to the gain medium, or to control the polarization modulator to send an anomaly warning message to the receiver.

[0032] Furthermore, the LCD shutter modulator includes two linear polarizers and a liquid crystal. The linear polarizers selectively block the light beam incident on them, and the liquid crystal layer acts as a modulator to rotate the polarization direction of the polarized light beam. When no voltage is applied, the LCD shutter modulator closes, the display turns black and is completely opaque, corresponding to the modulation signal "0". When voltage is applied, the shutter opens and becomes transparent, corresponding to the modulation signal "1".

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] This invention establishes an analytical model to reveal the energy transfer efficiency and field of view of a split-coupled cavity laser system. Closely integrated with the theoretical analysis model of free-space transmission, it proposes a sensing-computation fusion technology scheme that integrates positioning perception with the intracavity laser analysis model. Based on the intracavity laser analysis model, the theoretical field of view is simulated to determine the position of the receiver. While achieving positioning, it can also simulate the theoretical output power and detect whether there are abnormal states in the transmission channel when the transmitter and receiver are relatively stationary. This enables one-to-many energy transfer, communication, and positioning, supports intelligent control and detection of multiple receivers by the transmitter, and effectively solves the problem of positioning using intracavity lasers in complex dynamic scenarios. Attached Figure Description

[0035] Figure 1 This is a flowchart of the present invention;

[0036] Figure 2 This is a system structure diagram of the present invention;

[0037] Figure 3 This is a schematic diagram illustrating the principle of ID information acquisition at the receiving end of the present invention.

[0038] Figure 4 This is a schematic diagram of the intracavity laser ToF distance measurement principle based on chaotic laser correlation method of the present invention;

[0039] Figure 5 This is a schematic diagram of the analytical model of the split-cavity laser system (DCCL) of the present invention, wherein, Figure 5 (a) is a schematic diagram of the coordinate system and system structure used in the simulation of a split-cavity laser system (DCCL); Figure 5 (b) is a diagram of the equivalent reflective area of ​​the CCR cat's eye retroreflective structure; Figure 5 (c) is a diagram of a split-cavity laser system. Detailed Implementation

[0040] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0041] Definitions:

[0042] DCCL: Split-cavity laser system;

[0043] AOA: Angle of arrival;

[0044] LCD: liquid crystal;

[0045] ToF: Time-of-Flight ranging;

[0046] CMOS: Complementary Metal-Oxide-Semiconductor, which can be used as a sensor.

[0047] Simultaneous signal and energy transmission using intracavity lasers in a split-cavity laser system requires overcoming the bottlenecks of real-time alignment and high-power secure transmission with narrow beams facing mobile receivers in traditional methods. Furthermore, it necessitates overcoming dynamic interference from free-space resonant cavities and intracavity laser oscillation interference under strong external cavity feedback conditions. Based on this, it is hoped that intracavity laser signal and energy transmission technology can achieve significant improvements in three aspects: adaptive alignment, eye safety, and communication security (preventing wireless channel eavesdropping). This invention addresses split-cavity laser systems and proposes a method for positioning and anomaly detection in such systems. The flowchart of the method is shown below. Figure 1 As shown.

[0048] In terms of positioning and sensing, this invention realizes the angle of arrival (AOA) estimation calculation based on self-alignment features and the ranging calculation based on the hybrid laser correlation method. Regarding the intracavity laser analysis model, this invention establishes a simultaneous analysis model combining laser resonator mode analysis and gain simulation based on the rate equation. The split-coupled-cavity laser system (DCCL) analysis model is deployed at the transmitter end of the system. The application of the DCCL analysis model relies on information such as the free-space resonator length L2 and angle of arrival provided by the positioning and sensing method. This invention utilizes the sensed receiver position information to achieve real-time calculation of the intracavity laser analysis model, supporting dynamic analysis of signal and energy transmission channels, and enabling positioning and anomaly detection.

[0049] The structural diagram of the split-cavity laser system proposed in this invention is shown below. Figure 2 As shown, the system includes a transmitter and multiple receivers. The main resonant cavity is located at the transmitter, and a free-space resonant cavity is located between the transmitter and receivers. The transmitter is equipped with an image sensor, an ID demodulation module, a retroreflector, a polarization modulator, a polarization beam splitter, a beam splitter, an AOA measurement module, and a ToF measurement module. The receivers are equipped with an LCD shutter modulator, a retroreflector, an energy receiver, and a microprocessor. The transmitter also includes a fusion unit for deploying the split-cavity laser system (DCCL) analysis model.

[0050] In terms of positioning, this invention proposes to prioritize a spatially separated, energy-data transfer scheme using a split-cavity laser system to achieve monocular positioning. In the proposed positioning method, in addition to passively obtaining the receiver's three-dimensional spatial coordinates through Time-of-Flight (ToF) distance measurement and Angle-of-Arrival (AoA) angle measurement, it can also simultaneously transfer energy to the receiver, enabling information processing and cold start of the transmitting unit at the receiver, thereby obtaining information actively transmitted by the receiver (such as the receiver ID), supporting interoperability between unmanned devices. The receiver ID information is mainly transmitted in reverse from the receiver to the transmitter through an LCD shutter modulator and an ID demodulation module. Based on the ID information, the proposed monocular positioning method can achieve one-to-many energy transfer, communication, and positioning within the transmitter's field of view (FoV), supporting intelligent control of multiple receivers by the transmitter.

[0051] The localization and anomaly detection method of the present invention includes the following steps:

[0052] S1. Control the pump source to emit laser light. The laser light propagates in the main resonant cavity through the retroreflector. A gain medium is placed between the retroreflectors on both sides of the main resonant cavity. After passing through the main resonant cavity, the laser light enters the free space resonant cavity and propagates between the transmitting end and the receiving end of the free space resonant cavity through the retroreflector. At the same time, it is emitted towards the outside of the free space resonant cavity at the receiving end.

[0053] S2. Set the pump source to emit low-power laser, apply voltage to the LCD shutter modulator, and by changing the voltage, each LCD shutter modulator sends a modulation signal with the corresponding ID information of the corresponding receiver. The transmitter obtains the ID information of all receivers based on the presence or absence of the laser spot in the free space resonant cavity received by the image sensor and the demodulation of the modulation signal by the ID demodulation module.

[0054] S3. Determine whether the receiving end corresponding to the ID information is an authorized target receiving end. If so, continue to communicate with the receiving end and complete the handshake. Otherwise, stop communicating with the receiving end. For authorized target receiving ends, execute S4.

[0055] S4. Set up a pump source to emit a high-power laser. The transmitting end acquires the intracavity laser of the free space resonant cavity emitted by the target receiving end. The intracavity laser passes through a polarization modulator and a polarization beam splitter and is divided into a reference signal X(t) and a signal to be measured Y(t). The signal to be measured Y(t) passes through the beam splitter, with one part entering the ToF measurement module and the other part entering the image sensor.

[0056] S5. Calculate the cross-correlation function between the reference signal X(t) and the signal Y(t) to be measured based on the ToF measurement module, extract the time delay corresponding to the peak value in the cross-correlation curve, and obtain the distance L2 between the transmitter and receiver.

[0057] S6, the AOA measurement module calculates the theoretical field of view of the transmitter based on the analysis model of the split-coupled cavity laser system, determines the mapping relationship between the field of view and the pixel position of the image sensor, obtains the pixel position of the centroid of the laser spot by the algorithm of the intracavity laser spot and the centroid of the spot actually perceived on the image sensor, and determines the actual angle of arrival α2 of the receiver based on the mapping relationship.

[0058] S7. Based on the distance L2 measured in S5 and the actual angle of arrival α2 corresponding to the receiver, locate the receiver. Simultaneously, substitute the distance L2 and angle of arrival α2 into the analysis model of the split-coupled cavity laser system to determine the theoretically corresponding parameters of the analysis model. Compare the theoretical parameters with the actual parameters measured by the image sensor, AOA measurement module, ToF measurement module, and power meter to detect abnormal states in the transmission channel when the transmitter and receiver are relatively stationary. The theoretically corresponding parameters include the output power.

[0059] The principle of obtaining the receiver ID information of S2 is as follows:

[0060] The receiver's ID information is primarily transmitted uplink from the receiver to the transmitter via an LCD shutter modulator and ID demodulation module. The LCD shutter comprises two linear polarizers and a liquid crystal. According to Malus's law, a linear polarizer can selectively block a beam of light incident upon it. If the incident angle θ = 0°, the incident beam can pass through the linear polarizer; if θ = 90°, the incident beam is blocked. The liquid crystal layer acts as a modulator, rotating the polarization direction of the polarized beam. Typically, without applied voltage, the liquid crystal layer rotates the beam's polarization direction by 90 degrees, thus blocking the beam; conversely, with applied voltage, the liquid crystal layer does not rotate the beam's polarization direction, thus maintaining the beam. Therefore, the LCD shutter is "closed" (display black and completely opaque) when no voltage is applied, and "opened" (becomes transparent) when voltage is applied.

[0061] Based on the above principle, this invention employs an on-off keying (OOK) modulation scheme. At the receiving end, ID information is transmitted by changing the voltage applied to the LCD shutter: if the LCD shutter is open, the corresponding modulation signal is "1"; if the LCD shutter is closed, the corresponding modulation signal is "0". This allows ID information to be acquired at the transmitting end's CMOS image sensor by detecting the presence or absence of an intracavity laser spot and using an ID demodulation module. It is known that the information transmission rate from the receiving end to the transmitting end depends on the LCD's switching speed. A schematic diagram of the ID information transmission principle at the receiving end is shown below. Figure 3 As shown.

[0062] S2's low-power laser meets the eye safety requirements of laser safety standards such as IEC 60825-1-2014, with a typical power density of less than 5 mW / cm². 2.

[0063] The typical power density of the high-power laser in S4 is greater than 5 mW / cm². 2 .

[0064] In S5, the principle of intracavity laser ToF distance measurement is as follows:

[0065] The intracavity laser ToF distance measurement scheme proposed in this invention is as follows: Figure 4 As shown. Intracavity laser is a special type of chaotic laser. This scheme intends to adopt the hybrid laser correlation method for ranging, utilizing the correlation characteristics of the two intracavity laser waveforms—the reference signal and the signal to be measured—to measure the distance at the receiving end. Figure 4 In this context, τ represents the delay time of the signal under test relative to the reference signal. The cross-correlation function of the two signals is as follows:

[0066]

[0067] in, The cross-correlation operation is represented by k, which is the normalization coefficient, and δ, which represents the cross-correlation curve function between the reference signal and the signal under test. The distance to the receiver can be obtained by extracting the time delay τ corresponding to the peak value in the cross-correlation curve.

[0068] L2=cτ / 2n air

[0069] c is the speed of light, n air This refers to the refractive index of the optical path in the free-space resonant cavity. Multiple circuit delays must also be considered in the ToF distance measurement scheme. The correlation curve characteristics of the two intracavity lasers are crucial for achieving distance measurement; errors caused by atmospheric disturbances can be mitigated by n... air And so on.

[0070] In S6, the principle for measuring the angle of arrival AOA, i.e., α2, is as follows:

[0071] This invention captures the change in laser spot size within a free-space resonant cavity on the transmitter side using a CMOS image sensor, as the receiver moves. It then utilizes a centroid algorithm and a split-cavity laser system (DCCL) analysis model to measure the angle of arrival (AoA). First, the theoretical field of view (FoV) of the transmitter is obtained using the DCCL analysis model, and the sensing range of the CMOS image sensor is estimated to meet the requirements for AoA measurement. Next, the theoretical analysis model is used to establish a mapping relationship between the receiver's movement angle and the pixel positions on the CMOS image sensor. Finally, the pixel position of the laser spot's centroid is obtained using a centroid algorithm (such as a wavelet adaptive threshold centroid algorithm) on the CMOS image sensor, and the receiver's movement angle is estimated based on the aforementioned mapping relationship.

[0072] The analysis model of the split-cavity laser system is deployed in the inductive-computation fusion unit. The inductive-computation fusion unit processes the information flow of the system and supports online calculation of the deployed split-cavity laser system (DCCL) analysis model. The inductive-computation fusion unit can also deploy a small-sample continuous learning module for the sensed spot information to learn various implicit information of the spot in real-world scenarios, such as foreign object intrusion and abnormal operating status of the receiver.

[0073] In S7, based on the distance L2 measured in S5 and the actual angle of arrival α2 corresponding to the receiver, the split-coupled cavity laser system (DCCL) analysis model deployed in the inductive fusion unit is used to calculate the theoretical field of view FoV of the transmitter in high-power operation mode when the free space resonant cavity length is L2, where FoV ∈ (-α). 2,max α 2,max The selected CMOS image sensor needs to have a sensing range greater than the theoretical field of view (FoV) of the transmitter. Then, using a split-cavity laser system (DCCL) analysis model, FoV(FoV∈(-α)) is established. 2,max α 2,max The mapping relationship between the laser spot and the pixel position on the CMOS image sensor is established. Finally, by using an algorithm (such as the wavelet adaptive threshold centroid algorithm) to truly perceive the intracavity laser spot and centroid on the CMOS image sensor, the pixel position of the spot centroid is obtained, and the AoA angle α2 at the receiving end is determined according to the aforementioned mapping relationship.

[0074] α 2,max The calculation can be achieved through the following steps: First, determine P when the system is operating stably in high-power mode. in Value; second step, search P out When α = 0, the corresponding α2; the third step is to determine the searched value as the theoretical field of view FoV of the transmitter. Simultaneously, since the laser inside the main resonant cavity of the split-coupled cavity laser system is projected onto the CMOS image sensor at an incident angle of α1, the mapping relationship between FoV and the pixel position on the CMOS image sensor in S4 is... Figure 2 Distance L from beam splitter to CMOS image sensor x It is determined together with α1.

[0075] The principle of the analytical model of the split-coupled cavity laser system of S6 and S7 is as follows:

[0076] The analytical model of a split-cavity laser system is as follows: Figure 5As shown, an analytical model of DCCL was established based on diffraction theory and rate equations to simulate beam propagation through two coupled cavities and the interaction between beam propagation loss and gain in DCCL. Using the simulation model, the output laser power can be directly calculated under given system parameters (obtained through positioning sensing), such as reflector size, input power, and movement state.

[0077] The analysis model adopts Figure 5 (a) shows a typical design of a coupled-cavity laser system. (CER) i It is a cat's eye retroreflector structure, consisting of a mirror M. i and a lens Len i Composed of multiple retroreflectors, i∈{1,2,3,4}, forming a laser resonant cavity. The focal length of each lens is f. i The spacing between the mirrors and lenses in each retroreflector is l. i CER1 and CER2 form the main resonant cavity, while CER3 and CER4 form the free-space resonant cavity. The model analysis follows:

[0078] 1) Equivalent Resonant Cavity Model: To analyze the self-alignment characteristics of a split-coupled-cavity laser system and simulate the power flow of the laser within the cavity, a double retroreflective resonant cavity including a remote receiver placed at an arbitrary location is equivalent to an FP cavity with two mirrors. The size of each mirror is equal to the equivalent reflective area of ​​the corresponding retroreflector, which can also be used to estimate the relative angle between the transceiver.

[0079] For a CER i , i∈{1,2,3,4},l i =f i The coupling cavity design, at an angle α i The incident beam at CER i The equivalent reflecting surface on it can be represented as:

[0080]

[0081] Where r c Lenses and mirrors in CER i The radius in (0, a) i (a = a) are the center coordinates of the lens aperture shifted due to the angle of the incident beam, where:

[0082] a i =2f tan α i (2)

[0083] Therefore, as Figure 5In (a), the incident angle α1 of the laser in the cavity between CER1 and CER2, and the incident angle α2 of the laser in the cavity between CER3 and CER4, are given for each CER... i The equivalent reflecting surface can be based on f i and α 1,2 Calculate a separately i Indicates, such as Figure 5 As shown in (b). Furthermore, the new optical axis in the equivalent FP cavity is the line connecting the centers of the two equivalent reflecting surfaces, and the transmission distance is equal to the original transmission distance divided by cosα. i .

[0084] 2) Beam propagation in the coupled cavity: Figure 5 (c) describes the equivalent coupled cavity, where M' i CER i The equivalent reflecting surface. M' i Having r i and t i The amplitude reflectivity and transmittance, where |r i | 2 +|t i | 2 =1. Unlike existing intracavity laser systems formed by a single resonant cavity, in a split-coupled-cavity laser system, the strong feedback of the free-space cavity is imposed on the main resonant cavity. Therefore, the main resonant cavity remains resonant, and the free-space cavity remains anti-resonant, with the free-space cavity providing the maximum reflectivity to the main resonant cavity. For the main resonant cavity, in a given iteration, the guessed field on M'1 is E A,n The beam then propagates to M'2, where it is reflected and transmitted. Furthermore, the beam from the free-space cavity is fed back into the main resonant cavity after being fed back by M'4. Meanwhile, for the free-space cavity, the guessed field on M'3 is E. B,n It also propagates to M'4. Part of the beam propagates through M'4, forming the output beam. By analyzing this process and using a self-consistent equation for the round-trip propagation of a beam, we can derive two iterative relationships. Through these two iterative relationships (equation (3)), we can find the steady-state solutions for the main resonant cavity and the free-space resonant cavity, respectively:

[0085]

[0086] in It is an operator that describes the round-trip propagation within the main resonant cavity. It is an operator that describes round-trip propagation within a free-space resonant cavity. It is an operator describing unidirectional propagation from M'1 to M'2 and through M'2. It is an operator describing the propagation of the beam from M'3 to M'1. Specifically, and i∈{1, 2, 3, 4} are the reflection and transmission operators, respectively:

[0087]

[0088] The imaginary unit j represents the reflective properties of the mirror. and These are the propagation operators for the main resonant cavity and the free-space resonant cavity, respectively, and they are solutions for paraxial diffraction. We use a unified operator. The operation m∈{A, B} can be represented as follows:

[0089]

[0090] Where L m These represent the lengths of the main cavity and the free space cavity, respectively. and These represent the Fast Fourier Transform (FFT) and the Inverse Fast Fourier Transform (IFFT), respectively. (f x ,f y ) is the spatial frequency coordinate, and λ is the wavelength of the intracavity laser beam.

[0091] The Fox-Li algorithm is used to iterate over formula (3), E A,n (x,y) and E B,n (x, y) will all converge to a steady state. In this state, the iteration error (residual) of the intracavity laser field simulation no longer changes. In the simulation, the residual is the normalized difference in field values ​​between each iteration. For a typical intracavity beam field parameter E, the mathematical definition of this residual is:

[0092]

[0093] Where p and q are exponents corresponding to the spatial grid, and n is the number of simulation iterations, each step corresponding to one round-trip propagation process of the laser in the cavity.

[0094] 3) Gain Process Simulation: The above derivation focuses on obtaining the steady-state mode in a bare cavity (without a gain medium or without a gain process). However, gain process simulation is also crucial for system evaluation. Based on the gain process simulation, we can obtain the system's output laser power. Therefore, here we also incorporate the gain process simulation into the propagation process of the intracavity laser beam. For each iteration, the beam field is updated by the gain medium as long as it passes through the gain medium. After incorporating the gain process into the rate equation, the refresh process of the intracavity laser beam field E at the gain medium is summarized as follows:

[0095]

[0096] Where, c0 = 3 × 108 m / s is the speed of light in free space, ∈0=8.85×10 12 F / m is the vacuum permittivity, l g It is the length of the gain medium, g0 is determined by the pump efficiency η c Pump power P in Gain dielectric volume V and I S Calculated small gain coefficient:

[0097]

[0098] Equation (8) represents the relationship between the pump power entering the system and the beam power amplification within the cavity.

[0099] Finally, the beam field distribution converges according to expression (6) after amplification and loss within the cavity. Assuming the steady-state beam field distribution on M'4 is E4(x,y) and the intensity distribution is I4(x,y), which can be obtained from formula (8), we can calculate the output laser power on M'4 using the following expression:

[0100]

[0101] in This is the transmittance of M'4.

[0102] 4) Field of view (FoV): Figure 5 (a) The maximum range of the incident angle α2 of the laser in the cavity between CER3 and CER4 (-α 2,max α 2,max The field of view (FoV) of the transmitter is determined by α2. On the other hand, for a split-cavity laser system (DCCL) with other system parameters (such as reflectivity, cavity length, and gain medium characteristic parameters) fixed, a larger α2 results in greater system loss (making it more difficult for the gain medium to pump effectively). The maximum range of α2 (-α...) 2,max α 2,max From equation (8), P in Maximum range (-α) 2,max α 2,max P can be found by combining equations (7), (8), and (9). in When P is a constant, out The α2 corresponding to =0 is obtained.

[0103] The overall workflow of a split-cavity laser system is as follows:

[0104] To help the DCCL system adaptively sense the status of the transmission channel (i.e., foreign object intrusion detection), based on the spatial separation data-energy simultaneous transmission scheme (with low power density laser power density in the peripheral cavity serving as a protective optical field), the high-power-density intracavity laser inside the transmission channel is designed to operate in a "high-low power time slot switching" mode. In high-power mode, the receiver and transmitter are in normal data-energy simultaneous transmission operation. In low-power mode, the transmitter and receiver are in a mutual recognition handshake state, at which point the transmitter transmits low-power intracavity laser to an unknown receiver to drive the LCD of the target receiver.

[0105] The LCD on the target receiver is located on the CER4 retroreflector and achieves OOK modulation via a low-power intracavity laser pass-through switch. The target receiver can send predefined information (such as ID information) to the transmitter to confirm whether the transmitter is aligned with the authorized target receiver. Finally, once the target receiver and transmitter have established a handshake, the system activates high-power mode.

[0106] In high-power mode, the distance between the transmitter and the target receiver is first determined, and then the angle of arrival is estimated using CMOS. Simultaneously, the transmitter transmits high-power energy to the target receiver. During system operation, the distance measurement information and the angle of arrival estimation information are transmitted to the inductive-computation fusion unit, supporting the calculation of the split-coupled cavity laser system (DCCL) analysis model deployed within it. In the inductive-computation fusion unit, the DCCL analysis model is used to calculate the intracavity laser signal, which can be used to analyze foreign object intrusion, abnormal receiver operation, etc.

[0107] The split-coupled-cavity laser system of the present invention includes the following core subsystems: a split-coupled-cavity laser system, a receiver-end energy and information receiving system, and a transmitter-end positioning and sensing system.

[0108] A split-cavity laser system consists of a main resonant cavity (composed of a pump source, gain medium, and retroreflectors) and a free-space resonant cavity (composed of retroreflectors). The main resonant cavity is located at the transmitter end of the system and has two key design considerations: 1) the selection of the activation material, which can be a thin Nd:YVO4 gain medium, excited by an 808nm laser pump system; 2) the reflectivity design of the retroreflectors CER2 and CER3, which must meet the system's requirements for secure energy transfer and sensing / positioning (this can be calculated using a split-cavity laser system (DCCL) analysis model, followed by fabrication and coating). The energy transfer / communication / positioning carrier (intracavity laser) in the free-space resonant cavity propagates in free space, with one end mirror CER4 integrated at the receiver end.

[0109] The receiving end mainly includes an energy receiver, an information receiver, and a computing unit. Based on the design of a simultaneous energy and data transmission scheme, the energy receiver and information receiver employ various combination methods to achieve simultaneous energy conversion and information decoding. The energy receiver can use laser photovoltaic cells, such as Si cells or GaAs cells, achieving a conversion efficiency of 20%–30% for the 1064nm band and over 50% for the 800nm ​​band.

[0110] The information receiver can employ a photodiode (PD) or an avalanche photodiode (APD), with the computing unit integrated within the receiver to process the information stream at the receiving end. In the transmitter-side positioning and sensing system, information modulation is achieved based on a polarization modulator and a polarization beamsplitter. After passing through the beamsplitter, a portion of the light enters the Time-of-Flight (ToF) measurement module to complete distance measurement, while the remaining light enters a photosensitive element such as a CMOS or CCD to complete AoA (Aspect-of-Attribution) measurement and ID (Index Demodulation). This system also requires an information processing module and a sensing-computing fusion unit to process the information stream, supporting online calculations of the deployed mobility safety theoretical analysis model and the data-energy simultaneous transmission analysis model. The sensing-computing fusion unit can also deploy a small-sample continuous learning module for the sensed light spot information to learn various implicit information about the light spot in real-world scenarios, such as foreign object intrusion or abnormal receiver operating conditions.

[0111] The preferred embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of the present invention without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning, or limited experimentation on the basis of existing technology should be within the scope of protection defined by the claims.

Claims

1. A method for positioning and anomaly detection in a split-cavity laser system, characterized in that, The split-cavity laser system includes a transmitter and multiple receivers. The main resonant cavity is located at the transmitter, and the free-space resonant cavity is located between the transmitter and receivers. The transmitter is equipped with an image sensor, an ID demodulation module, a retroreflector, a polarization modulator, a polarization beam splitter, a beam splitter, an AOA measurement module, and a ToF measurement module. The receiver is equipped with an LCD shutter modulator, a retroreflector, an energy receiver, and a microprocessor. The method includes the following steps: S1. Control the pump source to emit laser light. The laser light propagates in the main resonant cavity through the retroreflector. A gain medium is placed between the retroreflectors on both sides of the main resonant cavity. After passing through the main resonant cavity, the laser light enters the free space resonant cavity and propagates between the transmitting end and the receiving end of the free space resonant cavity through the retroreflector. At the same time, it is emitted towards the outside of the free space resonant cavity at the receiving end. S2. Set the pump source to emit low-power laser, apply voltage to the LCD shutter modulator, and by changing the voltage, each LCD shutter modulator sends a modulation signal with the corresponding ID information of the corresponding receiver. The transmitter obtains the ID information of all receivers based on the presence or absence of the laser spot in the free space resonant cavity received by the image sensor and the demodulation of the modulation signal by the ID demodulation module. S3. Determine whether the receiving end corresponding to the ID information is an authorized target receiving end. If so, continue to communicate with the receiving end and complete the handshake. Otherwise, stop communicating with the receiving end. For authorized target receiving ends, execute S4. S4. Set up a pump source to emit a high-power laser. The transmitting end acquires the intracavity laser of the free space resonant cavity emitted by the target receiving end. The intracavity laser passes through a polarization modulator and a polarization beam splitter and is divided into a reference signal X(t) and a signal to be measured Y(t). The signal to be measured Y(t) passes through the beam splitter, with one part entering the ToF measurement module and the other part entering the image sensor. S5. Calculate the cross-correlation function between the reference signal X(t) and the signal Y(t) to be measured based on the ToF measurement module, extract the time delay corresponding to the peak value in the cross-correlation curve, and obtain the distance L2 between the transmitter and receiver. S6, the AOA measurement module calculates the theoretical field of view of the transmitter based on the analysis model of the split-coupled cavity laser system, determines the mapping relationship between the field of view and the pixel position of the image sensor, obtains the pixel position of the centroid of the laser spot by the algorithm of the intracavity laser spot and the centroid of the spot actually perceived on the image sensor, and determines the actual angle of arrival α2 of the receiver based on the mapping relationship. S7. Based on the distance L2 measured in S5 and the actual angle of arrival α2 corresponding to the receiver, locate the receiver. Simultaneously, substitute the distance L2 and angle of arrival α2 into the analysis model of the split-coupled cavity laser system to determine the theoretically corresponding parameters of the analysis model. Compare the theoretical parameters with the actual parameters measured by the image sensor, AOA measurement module, ToF measurement module, and power meter to detect abnormal states in the transmission channel when the transmitter and receiver are relatively stationary. The theoretically corresponding parameters include the output power.

2. The method for positioning and anomaly detection in a split-cavity laser system according to claim 1, characterized in that, The analytical model of the split-coupled cavity laser system includes four retroreflectors, which are divided into two groups of two. The first group of retroreflectors forms the main resonant cavity corresponding to the main resonant cavity of S1, and the second group of retroreflectors forms the free space resonant cavity corresponding to the free space resonant cavity of S1. Each retroreflector consists of a plane mirror and a lens.

3. The method for positioning and anomaly detection in a split-cavity laser system according to claim 2, characterized in that, The theoretical field of view FoV∈(-α) at ​​the transmitter 2,max α 2,max ), α2 represents the incident angle of the laser in the free-space resonant cavity, i.e., the angle of arrival, α 2,max The maximum range of α2 is represented by the following process for calculating the theoretical field of view of the transmitter: The first step is to determine the pump power P when the pump source emits high-power laser light. in ; The second step is to search for the output laser power P. out The angle reached when = 0; The third step is to determine the theoretical field of view (FoV) of the transmitter based on the angle of arrival obtained from the search.

4. The method for positioning and anomaly detection in a split-cavity laser system according to claim 2, characterized in that, In the analysis model, the laser inside the main resonant cavity is projected onto the image sensor at an incident angle of α1. At this time, the mapping relationship between the field of view and the pixel position of the image sensor is determined based on the incident angle α1 and the distance from the beam splitter to the image sensor.

5. The method for positioning and anomaly detection in a split-cavity laser system according to claim 1, characterized in that, After calculating the theoretical field of view in S6, it is determined whether the sensing range of the image sensor is greater than the theoretical field of view. If so, S6 continues to be executed; otherwise, the sensing range of the image sensor is adjusted until it is greater than the theoretical field of view.

6. The method for positioning and anomaly detection of a split-cavity laser system according to claim 1, characterized in that, The cross-correlation function is: in, This represents the cross-correlation operation, where k is the normalization coefficient, δ represents the cross-correlation curve function between the reference signal and the signal under test, and R... xy (τ) represents the cross-correlation function, τ represents the time delay, X(t) represents the reference signal, and Y(t) represents the signal to be measured.

7. The method for positioning and anomaly detection of a split-cavity laser system according to claim 6, characterized in that, The distance between the transmitter and receiver is: L2=cτ / 2n air Where c is the speed of light, n air τ is the refractive index in the optical path of the free-space resonant cavity, and τ represents the time delay.

8. The method for positioning and anomaly detection of a split-cavity laser system according to claim 1, characterized in that, After the handshake, the laser beam outside the free-space resonant cavity of the receiving end is directed to the information receiver of the transmitting end. The microprocessor obtains information from the transmitting end based on the information receiver of the transmitting end. The energy receiver connects the microprocessor and the information receiver of the transmitting end. The energy receiver receives the energy of the laser beam outside the cavity and supplies power to the microprocessor and the information receiver of the transmitting end.

9. The method for positioning and anomaly detection in a split-cavity laser system according to claim 1, characterized in that, After comparing the actual and measured parameters, if an anomaly occurs in the transmission channel when the transmitter and receiver are relatively stationary, a control signal is sent to the gain medium or polarization modulator at the transmitter to control the pump power supplied to the gain medium, or to control the polarization modulator to send an anomaly warning message to the receiver.

10. The method for positioning and anomaly detection in a split-cavity laser system according to claim 1, characterized in that, An LCD shutter modulator contains two linear polarizers and a liquid crystal. The linear polarizers selectively block the light beam incident on them, and the liquid crystal layer acts as a modulator to rotate the polarization direction of the polarized light beam. When no voltage is applied, the LCD shutter modulator closes, the display turns black and is completely opaque, corresponding to the modulation signal "0". When voltage is applied, the shutter opens and becomes transparent, corresponding to the modulation signal "1".

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