Safety measurement method for distributed coupled cavity laser system

Abstract

The invention relates to a distributed coupled cavity laser system-oriented security measurement method, which comprises the following steps of: modeling a distributed coupled cavity laser system, and constructing an intrusion plane model and a CRR equivalent plane model based on key physical parameters and optical parameters; the intrusion plane model and the CRR equivalent plane model are used as boundary conditions, a diffraction-gain self-consistent equation set of light beam bidirectional propagation in the system is constructed based on key physical parameters and optical parameters, and after gain is introduced, iteration solution is carried out to obtain steady-state light field distribution; based on the steady-state light field distribution, calculating the total illumination of the corresponding intrusion plane and the light power upper limit of a laser beam output by the system under a safe condition; and selecting an appropriate value of the illumination safety threshold for each type of intrusion scene, comparing the appropriate value with the total illumination, and outputting a safety measurement result of the distributed coupled cavity laser system in combination with the upper limit of the optical power. Compared with the prior art, the invention provides a measurement method capable of quickly evaluating the security of the system under different working parameters and intrusion conditions.

Description

Technical Field

[0001] This invention relates to the field of long-distance wireless power transmission, and in particular to a safety measurement method for distributed coupled-cavity laser systems. Background Technology

[0002] Wireless power transfer (WPT) technology is particularly suitable for long-distance transmission and electromagnetically confined environments due to its high directionality, wide modulation bandwidth, and resistance to electromagnetic interference. Traditional external cavity laser wireless power transfer systems typically rely directly on free-space beams for energy transfer, where a laser beam generated at the receiving end illuminates a photoelectric conversion device at the receiving end. While offering high transmission efficiency, these systems suffer from issues such as strict alignment requirements, high radiation risks due to concentrated beams, and the potential for skin or eye damage when exposed to human contact. Furthermore, the system cannot promptly interrupt energy transfer when foreign objects intrude.

[0003] To address this, intracavity laser structures have been proposed. These structures form a closed resonant cavity between the transmitter and receiver, enhancing the oscillation of the laser beam within the cavity. For example, the recently proposed Distributed Coupled-Cavity Laser (DCCL) system not only enhances the field of view (FoV) of wireless power transfer systems but also possesses self-alignment and inherent security. It is considered a key architecture for next-generation high-security laser wireless power transfer systems. For instance, Chinese patent application CN113629897A provides a method for improving the security of composite cavity structures. This method improves the security of wireless charging systems by incorporating aperture groups and utilizing a combination of main resonant cavities and free resonant cavities. However, while these methods consider safety in their structural design, they lack systematic safety measurement and quantitative evaluation methods. Especially in practical applications, systems may face various complex scenarios such as accidental skin exposure, accidental eye irradiation, and foreign object intrusion, making their safety boundaries susceptible to fluctuations in operating parameters and external interference. If a system cannot make rapid and accurate safety status assessments under different operating conditions and intrusion scenarios, its inherent security will be difficult to reliably achieve in practice. Therefore, developing models and methods capable of real-time assessment of the safety risks of distributed coupled-cavity laser systems has become an indispensable key step in advancing its practical application.

[0004] Therefore, providing a measurement method that can quickly assess the safety of a system under different operating parameters and intrusion conditions, especially a safety measurement method for distributed coupled-cavity laser systems designed for complex scenarios such as skin exposure, eye irradiation, and foreign body intrusion, is a technical problem that needs to be solved. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the existing technology and provide a safety measurement method for distributed coupled cavity laser systems.

[0006] The objective of this invention can be achieved through the following technical solutions: According to a first aspect of the present invention, a method for measuring the safety of a distributed coupled-cavity laser system is provided, the method comprising: A distributed coupled-cavity laser system is modeled, and key physical and optical parameters of the system are obtained. Based on the key physical and optical parameters, an intrusion plane model and a CRR equivalent plane model are constructed; and the intrusion plane includes a large intrusion plane and a small intrusion plane. Using the aforementioned intrusion plane model and CRR equivalent plane model as boundary conditions, a diffraction-gain self-consistent equation set for the bidirectional propagation of the beam in the system is constructed based on the aforementioned key physical and optical parameters. After introducing the gain, the steady-state optical field distribution is obtained by iterative solution. Based on the aforementioned steady-state light field distribution, calculate the total illuminance of the corresponding intrusion plane and the upper limit of the optical power of the system's output laser beam under safe conditions; For each type of intrusion scenario, an appropriate value for the illumination safety threshold is selected. The appropriate value is compared with the total illumination, and combined with the upper limit of optical power, the safety measurement result of the distributed coupled cavity laser system is output.

[0007] As a preferred technical solution, the invasion plane model of the large invasion plane is a knife-edge model. In the knife-edge model, if the coordinate points of the coordinate system defined by the optical axis intercept plane in the distributed coupled cavity laser system satisfy the condition that the distance to the origin does not exceed the radius of the invasion plane... And the x-coordinate does not exceed the intrusion location. If the value is 1, then the effective plane value corresponding to that point is determined to be 1; otherwise, the effective plane value corresponding to that point is determined to be 0. The intrusion plane model of the small intrusion plane is a rectangular occlusion model. In the rectangular occlusion model, if the coordinate point satisfies the condition that the distance to the origin does not exceed the radius of the intrusion plane... If the coordinate point satisfies the condition that the distance to the origin exceeds the radius of the intrusion plane, then the effective plane value corresponding to that point is determined to be 1; Or, the x and y coordinates are respectively located in the interval [0, 1]. and If the value of the plane corresponding to the point is 0, then the effective plane value of that point is determined to be 0. Represents the coordinates of a small object that intrudes into the resonant cavity of a distributed coupled-cavity laser system; Indicates the width of small objects; Indicates the length of a small object.

[0008] As a preferred technical solution, in the aforementioned CRR equivalent plane model, for the i-th CRR, if the coordinate point satisfies the condition that the distance to the origin does not exceed the radius of the lens and mirror in the CRR... And the x-coordinate does not exceed the intrusion location. If the value of the point is 1, then the effective plane value corresponding to that point is determined to be 1; otherwise, the effective plane value corresponding to that point is determined to be 0.

[0009] As a preferred technical solution, the diffraction-gain self-consistent equation set is as follows: , in, This indicates that the diffraction-gain self-consistent equations are calculated in the nth iteration. This represents the optical field distribution in a free-space cavity within a distributed coupled-cavity laser system. This represents the optical field distribution in the main cavity of a distributed coupled-cavity laser system. This represents the operator used to describe one round trip of a light beam inside the main cavity, and has... , and This represents the reflection process of a light field. This represents the propagation process of a light field; Let represent the operator used to describe one round trip of a light beam in a free-space cavity, and have . , and These represent the processes of the light field reaching the intrusion plane and the light field reaching the reflecting mirror, respectively. and This represents the process of a light field being reflected by a mirror. This represents the process of a light field passing through an intruding plane or a reflecting mirror; This represents an operator used to describe the unidirectional propagation of beam energy from the main cavity to the free space cavity, and has... , This represents the propagation process of the energy field of the light beam. This represents the transmission process of an energy field; This represents an operator used to describe the unidirectional propagation of energy from the free-space cavity back to the main cavity, and has... ; And for each reflection and transmission process: , , , , , field The reflection operator of the i-th CRR mirror; Represents the imaginary unit. Let represent the amplitude reflection coefficient of the mirror in the i-th CRR; This represents the boundary conditions in the i-th CRR, corresponding to the equivalent planar model of the i-th CRR; field The transmission operator of the i-th CRR mirror; This represents the amplitude transmission coefficient of the transmission mirror in the i-th CRR; field The calculation factor in the invasion plane; Represents the intrusion plane model, and , Represents the knife edge model. Represents a rectangular occlusion model; Indicates the propagation operator, and ; and These represent the inverse Fourier transform and the Fourier transform, respectively. Represents the transfer function; Indicates spatial frequency; Indicates the wavelength of the light beam; This indicates the distance the light beam travels.

[0010] As a preferred technical solution, the iterative solution process is as follows: An initial guess value is assigned to the light field distribution of the free space cavity and the inner cavity. Based on the initial guess value, the light field distribution of the free space cavity and the inner cavity in the next iteration is solved using the diffraction-gain self-consistent equation system. For the nth iteration, the light field distribution is calculated based on the light field distribution of the (n-1)th iteration. For the optical field distribution of the internal cavity and the optical field distribution of the free space cavity, the optical field distribution is updated to a new optical field distribution considering saturation gain using the gain-coupling formula; The cavity laser residual is calculated based on the new optical field distribution. If the cavity laser residual is less than a set threshold, convergence is determined, the iteration ends, and the corresponding new optical field distribution is taken as the steady-state optical field distribution. Otherwise, the optical field distribution for the next iteration is calculated based on the new optical field distribution.

[0011] As a preferred technical solution, the gain-coupling formula is: , in, Indicates the saturation intensity of the gain medium; This represents the speed of light in a vacuum. Represents the vacuum permittivity; This indicates the optical field distribution within the cavity or the optical field distribution in a free space cavity before entering the gain medium. Represents the logarithmic function of the product; Let represent the small-signal gain coefficient, and: , This indicates the efficiency of converting pump power into gain. Indicates the power input to the pump. Indicates the volume of the gain medium; Indicates the length of the gain medium; Represents an intermediate variable, and: .

[0012] As a preferred technical solution, the method for calculating the total illuminance is as follows: Steady-state optical field distribution based on free-space cavity Obtain the steady-state light field distribution at the last reflecting mirror in the free-space cavity. ; based on and the steady-state optical field distribution of the free space cavity. The optical field distribution of the light beam before and after propagation to the intrusion plane is calculated, where the optical field distribution before the intrusion plane is based on the intrusion plane model. propagation operators and The calculated light field distribution after intrusion into the plane is based on the intrusion plane model. propagation operators and Calculated; The forward and reverse light field illuminances are calculated based on the light field distributions before and after the intrusion plane, and the total illuminance is the sum of the two.

[0013] As a preferred technical solution, the method for calculating the upper limit of optical power is as follows: Based on the steady-state light field distribution at the last reflecting mirror in the free space cavity Calculate the illuminance of the laser on the corresponding mirror, and then calculate the output laser power of the corresponding mirror based on this illuminance. The expression is as follows: , in, This indicates the output laser power of the reflector; This indicates the transmittance of the last reflecting mirror; Indicates coordinates Illuminance value at that location; This represents the speed of light in a vacuum. Represents the vacuum permittivity; Using the maximum power point tracking method and dynamically adjusting the equivalent load resistance, the wireless charging current is calculated based on the output laser power as follows: , in, This indicates the response speed of the PV cell; Indicates reverse saturation current; Represents the elementary charge; Indicates the number of batteries; The ideal factor representing the equivalent diode inside the battery; Represents the Boltzmann constant; Kelvin represents absolute temperature; , and These represent the equivalent load resistance, internal equivalent series resistance, and internal equivalent parallel resistance, respectively. A charging current-voltage characteristic curve is plotted based on the wireless charging current. The maximum power point is selected based on this curve, and the power value corresponding to this point is the upper limit of the optical power. Its calculation method is as follows: .

[0014] As a preferred technical solution, the large invasion plane includes the skin, and the small invasion plane includes the hair; for the skin, a fixed maximum permissible exposure value is selected. As an appropriate value, when the total illuminance of the skin is less than If so, it is considered safe; For the hair, a fixed rapid decay time threshold is selected as an appropriate value, where the rapid decay time is the time required for the intracavity optical field of the distributed coupled cavity laser system to decay to a preset percentage when the obstruction causes the obstruction to cause the obstruction to occur.

[0015] As a preferred technical solution, the intrusion plane also includes the human eye, and the method for selecting an appropriate value for the human eye is as follows: Construct a three-dimensional head model of the human head in an intrusive distributed coupled cavity laser system, and calculate the minimum convex polyhedron that surrounds all points of the head model, i.e., the convex hull. For each external tangent of the convex hull, calculate the distance from the eye to the external tangent and take the minimum value of the distance; and calculate the angle between the eye normal vector and the external tangent and the necklace. Based on the minimum distance and the corresponding angle, it is determined whether the laser will be focused onto the retina. If so, the maximum permissible exposure value of the first retina is selected as the appropriate value. If the focus is not on the retina, then the maximum permissible exposure value of the second retina is selected as the appropriate value; Furthermore, the maximum permissible exposure value of the first retina is much smaller than the maximum permissible exposure value of the second retina.

[0016] Compared with the prior art, the present invention has the following beneficial effects: 1) To address the problem that existing technologies cannot rapidly assess distributed coupled-cavity laser systems under different operating parameters and intrusion conditions, this invention proposes a safety measurement method for distributed coupled-cavity laser systems. In this method, the coupled-cavity structure is equivalent to a parallel planar cavity, and the propagation of the laser beam within the cavity is described. Then, the intrusion plane of the intruding object is modeled, and different indicator functions are constructed to describe intrusion physics of different sizes. Since the surface irradiance of the intruding object includes forward irradiance and backward irradiance, after mathematically modeling and measuring the steady-state light field of the distributed coupled high-intensity laser, this invention calculates the light field and irradiance before and after the intruding object using the self-consistent equation of the light field. Finally, the system safety is quantitatively determined based on the irradiance and the international maximum permissible exposure standard.

[0017] 2) Considering that when the intruding object is the eye, the focusing state of the laser on the retina can cause varying degrees of damage to the eye, specifically, when the direction of the incident laser is close to the optical axis of the eye and the laser incident point is close to the surface of the eye, it means that the laser enters the eye almost along the direction of the pupil and is focused on the retina by the cornea and lens. This is a high-risk focusing situation that may cause retinal burns. To ensure eye safety, a more stringent maximum permissible exposure value for the retina should be selected. However, when the incident angle is large or the distance between the outer tangent and the eye is small, the laser cannot enter the eyeball along the optical axis. The part of the light that enters the eyeball will be reflected or scattered at the cornea and will not converge on the retina. This is an unfocused situation, and the energy mainly stays on the surface of the cornea or around the eyelids. The risk is significantly reduced, and the corresponding safety threshold limit can be appropriately relaxed. To address the aforementioned issues, this invention constructs a three-dimensional human head model, calculates the distance between the eyes and the head bulge, as well as the angle between the normal vectors, based on this model, and ultimately determines the laser's focusing state based on the distance and the corresponding angle, thereby setting different safety thresholds; ensuring more detailed and accurate safety measurements while meeting the system's optimal operating power. Attached Figure Description

[0018] Figure 1 This is a flowchart of the method of the present invention; Figure 2 The coordinate system of the wireless power transfer system based on distributed coupled cavity laser of the present invention is shown below. Figure 3 This is a schematic diagram of beam propagation in the presence of an intruding object, and the planar boundaries of two types of intruding objects, according to the present invention. Figure 4This is a schematic diagram of a three-dimensional human head model according to the present invention; (a) represents the three-dimensional human head model; (b) represents the convex hull cutting plane; Figure 5 The diagram shows the focusing of the laser beam onto the retina according to the present invention; (a) shows the laser beam focused onto the retina; (b) shows the laser beam not focused onto the retina. Detailed Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0020] This invention proposes a safety measurement framework for wireless power transfer systems based on distributed coupled cavity lasers, which addresses the shortcomings of existing intracavity laser wireless power transfer systems in terms of safety assessment. Specifically, it lacks a unified multi-scenario safety measurement model and cannot quantitatively assess the risks of skin, eye, and foreign body intrusion. The aim is to provide a safety measurement framework that can quantitatively assess the risks of skin exposure, eye irradiation, and foreign body intrusion under different operating parameters and intrusion scenarios.

[0021] Specifically, the method and process are as follows: Figure 1 As shown, it includes: S1. Model the distributed coupled cavity laser system and obtain the key physical and optical parameters of the system. Based on the key physical and optical parameters, construct the intrusion plane model and the CRR equivalent plane model.

[0022] Distributed coupled cavity laser systems such as Figure 2 As shown, it consists of a series of retroreflectors (cat glasses), each composed of a thin lens and a reflector. L1 and M1 form the first set of retroreflectors, L2 and M2 / 3 form the second set, M2 / 3 and L3 form the third set, and M4 and L4 form the fourth set. Its overall structure is divided into three parts: the first part, consisting of L1, M1, L2, M2 / 3, and L3, forms the transmitter, used to transmit energy; the second part is the free-space cavity, also known as the over-the-air transmission channel, corresponding to the distance L; and L4 and M4 form the receiver.

[0023] By defining an intrusion plane in the free-space cavity portion along the system's optical axis, its relative position, attitude angle, and incident depth with respect to the transmitter and receiver are determined. Specifically, the intrusion plane includes a large intrusion plane and a small intrusion plane, and its model structure can be equivalent to... Figure 3 As shown in the image, the specific details are as follows: i) For large intrusion planes such as skin or head, the intrusion plane model is a knife-edge model. In the knife-edge model, if the coordinates of the coordinate system defined by the optical axis section plane in the distributed coupled cavity laser system satisfy the condition that the distance to the origin does not exceed the radius of the intrusion plane. And the x-coordinate does not exceed the intrusion location. If the condition is met, the valid plane value corresponding to that point is determined to be 1; otherwise, the valid plane value corresponding to that point is determined to be 0. The expression is as follows: , in, This represents the coordinate point of the coordinate system defined by the optical axis section plane in a distributed coupled cavity laser system; Indicates the radius of the intrusion plane; Indicates the location of the invasion on the invasion plane.

[0024] ii) A small intrusive plane includes hair, which can be simplified into a rectangle, where length represents the length and width represents the diameter. Then... and Let these be the length and width of the hair, respectively, and ( , Let be the coordinates of the hair that invaded the resonant cavity, and its invasion plane model can be set as a rectangular occlusion model. In the rectangular occlusion model, if the coordinates satisfy the condition that the distance from the origin does not exceed the radius of the invasion plane... If the coordinate point satisfies the condition that the distance to the origin exceeds the radius of the intrusion plane, then the effective plane value corresponding to that point is determined to be 1; Or, the x and y coordinates are respectively located in the interval [0, 1]. and If the value of the plane corresponding to the point is 0, then the effective plane value of that point is determined to be 0. Represents the coordinates of a small object that intrudes into the resonant cavity of a distributed coupled-cavity laser system; Indicates the width of small objects; The length of a small object is expressed as: .

[0025] A resonant cavity composed of CRRs can be equivalently modeled as a cavity with plane mirrors, where the size of each mirror corresponds to the effective reflection area of ​​the associated CRR under moving conditions. Therefore, for... For the i-th CRR, in its equivalent planar model, if the coordinate point satisfies the condition that the distance to the origin does not exceed the radius of the lens and mirror in the CRR... And the x-coordinate does not exceed the intrusion location. If the condition is met, the valid plane value corresponding to that point is determined to be 1; otherwise, the valid plane value corresponding to that point is determined to be 0. The expression is as follows: , in, This represents the coordinate point of the coordinate system defined by the optical axis section plane in a distributed coupled cavity laser system; Let represent the radius of the lens and mirror in the i-th CRR, and let be the center of the offset lens aperture in the CRR. , Incident beam angle at the CRR surface caused by the transceiver angle Decision, and have ; Indicates the location of the intrusion plane.

[0026] S2. Using the intrusion plane model and the CRR equivalent plane model as boundary conditions, construct a set of diffraction-gain self-consistent equations for the bidirectional propagation of the beam in the system based on key physical and optical parameters, and then iteratively solve the steady-state light field distribution after introducing the gain.

[0027] Specifically, based on the distributed coupled-cavity laser structure, a self-consistent set of diffraction-gain equations for bidirectional propagation is established, and the process is as follows: Figure 3 As shown, firstly, the effective reflecting surface of each retroreflector is calculated, specifically using an indicator function. Then, a Fast Fourier Transform (FFT) is used to model the diffraction propagation of the light field within the cavity, specifically calculating the light field distribution reaching the plane after propagating a certain distance. Secondly, a relevant gain equation is introduced each time the light beam passes through the gain medium to simulate the optical power amplification process. Finally, the Fox-Li algorithm is used to iteratively calculate the laser beam within the cavity, solving for the steady-state light field distribution. Based on the solution results, the light intensity distribution and peak irradiance at the invasive plane in the free-space cavity can be obtained. Since the laser beam undergoes continuous bidirectional propagation within the free-space resonant cavity, using... The irradiance intruded onto the surface of an object due to forward (transmitter-to-receiver) transmission is represented by... This represents the irradiance caused by receiver-to-transmitter transmission. The total irradiance penetrating the surface of an object is determined by... The detailed steps are as follows: S21. The self-consistent equations for diffraction-gain are constructed, and their expressions are as follows: , in, This indicates that the diffraction-gain self-consistent equations are calculated in the nth iteration. This represents the optical field distribution in a free-space cavity within a distributed coupled-cavity laser system. This represents the optical field distribution in the main cavity of a distributed coupled-cavity laser system. This represents the operator used to describe one round trip of a light beam inside the main cavity, and has... , and This represents the reflection process of a light field. This represents the propagation process of a light field; Let represent the operator used to describe one round trip of a light beam in a free-space cavity, and have . , and These represent the processes of the light field reaching the intrusion plane and the light field reaching the reflecting mirror, respectively. and This represents the process of a light field being reflected by a mirror. This represents the process of a light field passing through an intruding plane or a reflecting mirror; This represents an operator used to describe the unidirectional propagation of beam energy from the main cavity to the free space cavity, and has... , This represents the propagation process of the energy field of the light beam. This represents the transmission process of an energy field; This represents an operator used to describe the unidirectional propagation of energy from the free-space cavity back to the main cavity, and has... ; And for each reflection and transmission process: , , , , , field The reflection operator of the i-th CRR mirror; Represents the imaginary unit. Let represent the amplitude reflection coefficient of the mirror in the i-th CRR; This represents the boundary conditions in the i-th CRR, corresponding to the equivalent planar model of the i-th CRR; field The transmission operator of the i-th CRR mirror; This represents the amplitude transmission coefficient of the transmission mirror in the i-th CRR; field The calculation factor in the invasion plane; Represents the intrusion plane model, and , Represents the knife edge model. Represents a rectangular occlusion model; Indicates the propagation operator, and ; and These represent the inverse Fourier transform and the Fourier transform, respectively. Represents the transfer function; Indicates spatial frequency; Indicates the wavelength of the light beam; This indicates the distance the light beam travels.

[0028] S22. The gain-coupling formula is constructed, and its corresponding expression is: , in, Indicates the saturation intensity of the gain medium; This represents the speed of light in a vacuum. Represents the vacuum permittivity; This indicates the optical field distribution within the cavity or the optical field distribution in a free space cavity before entering the gain medium. Represents the logarithmic function of the product; Let represent the small-signal gain coefficient, and: , This indicates the efficiency of converting pump power into gain. Indicates the power input to the pump. Indicates the volume of the gain medium; Indicates the length of the gain medium; Represents an intermediate variable, and: .

[0029] Furthermore, the process of laser light passing through a gain medium can also be replaced by the data integral form of the rate equation, and the corresponding standard rate equation can be written as: , in, Indicates the number of particles; Represents the reduced Planck constant ( , (This is Planck's constant). Indicates angular frequency; Indicates the spontaneous emission lifetime of the gain medium; This represents the stimulated emission cross section, characterizing the intensity of the interaction between the particle and the light field; Group velocity represents the speed at which light propagates through a medium. This represents the total loss factor, which includes mirror loss, scattering absorption, etc., and determines the cavity attenuation.

[0030] S23. Solving for steady-state light field distribution.

[0031] S231. Assign initial guesses to the light field distribution of the free space cavity and the inner cavity. Based on the initial guesses, use the diffraction-gain self-consistent equations to solve for the light field distribution of the free space cavity and the inner cavity in the next iteration. For the nth iteration, the light field distribution is calculated based on the light field distribution of the (n-1)th iteration.

[0032] Specifically, for different types of intrusion planes, different models are substituted into the diffraction-gain self-consistent equation system to obtain the light field distribution of the free space cavity and the inner cavity under the corresponding intrusion plane type. For example, when the intrusion plane is a large object such as human skin, the knife edge model is substituted into the equation system, and when it is a small object such as hair, the rectangular occlusion model is used.

[0033] S232. For the optical field distribution of the internal cavity and the optical field distribution of the free space cavity, the optical field distribution is updated to a new optical field distribution considering saturation gain using the gain-coupling formula.

[0034] S233. Calculate the intracavity laser residual based on the new optical field distribution. If the intracavity laser residual is less than... If the value is adjustable, then convergence is determined, the iteration ends, and the corresponding new light field distribution is taken as the steady-state light field distribution; otherwise, the light field distribution for the next iteration is calculated based on the new light field distribution.

[0035] The detailed formula for calculating residuals is as follows: , in, This indicates that in the nth iteration, at the discrete grid point The light field distribution at the location; n represents the number of iterations.

[0036] S3. Calculate the total illuminance of the corresponding intrusion plane and the upper limit of the optical power of the output laser beam of the system under safe conditions based on the steady-state optical field distribution.

[0037] S31. Calculate the total illuminance.

[0038] S311. Steady-state optical field distribution based on free-space cavity Obtain the steady-state light field distribution at the last reflecting mirror in the free-space cavity. .

[0039] S312, based on Steady-state optical field distribution of free space cavity The optical field distribution of the light beam before and after propagation to the intrusion plane is calculated, where the optical field distribution before the intrusion plane is based on the intrusion plane model. propagation operators and The calculated light field distribution after intrusion into the plane is based on the intrusion plane model. propagation operators and The calculation yields the following expression: , .

[0040] S313. Calculate the forward and reverse light field illuminance based on the light field distribution before and after the intrusion plane. The total illuminance is the sum of the two, and its expression is: , in, Indicates the illuminance of the forward light field; Indicates the illuminance of the reverse light field; Indicates the illuminance of the forward light field; This represents the illuminance of the reverse light field.

[0041] S314, Select The maximum value in the range is taken as the peak illuminance value.

[0042] After step S31, the peak illuminance value of each intrusion plane can be calculated, which serves as an important indicator for subsequent safety measurement.

[0043] S32. Calculate the upper limit of optical power.

[0044] S321. Steady-state optical field distribution based on the last reflecting mirror in a free-space cavity. Calculate the illuminance of the laser on the corresponding mirror, and then calculate the output laser power of the corresponding mirror based on this illuminance. The expression is as follows: , in, This indicates the output laser power of the reflector; This indicates the transmittance of the last reflecting mirror; Indicates coordinates Illuminance value at that location; This represents the speed of light in a vacuum. This represents the vacuum permittivity. S322. Using the maximum power point tracking method and dynamically adjusting the equivalent load resistance, the wireless charging current is calculated based on the output laser power as follows: , in, This indicates the response speed of the PV cell; Indicates reverse saturation current; Represents the elementary charge; Indicates the number of batteries; The ideal factor representing the equivalent diode inside the battery; Represents the Boltzmann constant; Kelvin represents absolute temperature; , and These represent the equivalent load resistance, internal equivalent series resistance, and internal equivalent parallel resistance, respectively.

[0045] S323. Plot the charging current-voltage characteristic curve based on the wireless charging current. Select the maximum power point based on the charging current-voltage characteristic curve. The power value corresponding to this point is the upper limit of optical power, and its calculation method is as follows: .

[0046] S4. Select an appropriate value for the illumination safety threshold for each type of intrusion scenario, compare the appropriate value with the total illumination, and combine it with the upper limit of optical power to output the safety measurement result of the distributed coupled cavity laser system.

[0047] For skin, a fixed maximum permissible exposure value is selected. As an appropriate value, when the peak illuminance value of the skin is less than If so, it is considered safe; The values ​​are determined based on standard ICNIRP(2020) / IEC60825-1:2014.

[0048] For hair, a fixed rapid decay time threshold is selected as an appropriate value, where the rapid decay time is the time when the optical field inside the distributed coupled cavity laser system decays to 90% of the level it would be without intrusive plane obstruction (i.e., ...). The time required when ), if that time is less than If the measurement result is safe, the attenuation level is set to 90% because the system can automatically shut down when the occlusion causes the intracavity light field to attenuate by more than 90%.

[0049] For the human eye, when the incident laser direction is close to the optical axis of the eye and the laser incident point is close to the eye surface, it means that the laser enters the eye almost along the pupil direction and is focused onto the retina by the cornea and lens. This is a high-risk focusing situation that may cause retinal burns. To ensure eye safety, a more stringent maximum permissible retinal exposure value should be selected. However, when the incident angle is large or the outer tangent is close to the eye, the laser cannot enter the eyeball along the optical axis. The portion of the light entering the eyeball will be reflected or scattered at the cornea and will not converge onto the retina. This is an unfocused situation, where the energy mainly remains on the corneal surface or around the eyelids, significantly reducing the risk. The corresponding safety threshold can be appropriately relaxed. Therefore, different safety thresholds need to be selected for different situations. The method is as follows: i) Construct a three-dimensional head model of the intrusive distributed coupled-cavity laser system, such as... Figure 4 As shown in (a), calculate the minimum convex polyhedron that encloses all points of the human head model, i.e., the convex hull.

[0050] ii) For each circumferential surface of the convex hull (the circumferential surface is as follows: ...) Figure 4 As shown in (b), calculate the distance from the eye to the outer tangent plane and take the minimum value of the distance; and calculate the angle between the eye normal vector and the outer tangent plane and the necklace.

[0051] iii) Based on the minimum distance and the corresponding angle, determine whether the laser will be focused onto the retina. If so (corresponding to...) Figure 5 In the case shown in (a), the maximum permissible exposure value of the first retina is selected as the appropriate value; if the focus is not on the retina (corresponding to...) Figure 5 In the case shown in (b), the maximum permissible exposure value of the second retina is selected as the appropriate value; and the maximum permissible exposure value of the first retina is much smaller than the maximum permissible exposure value of the second retina, such as the maximum permissible exposure value of the first retina being set to a value of The maximum permissible exposure value for the second retina is [value missing]. .

[0052] More specifically, an eye model was built in Ansys Zemax OpticStudio, including the cornea, lens, vitreous body, and retina. Each component was given a specific refractive index and optical function, and the minimum distance d and the corresponding incident angle were also defined. The incident position coordinates and direction vector are input into the ray tracing simulation module to verify whether the laser is focused on the retina under the incident conditions.

[0053] In summary, this invention proposes the first security measurement framework for wireless power transfer systems based on distributed coupled cavity lasers (DCCL). Previous studies have mostly focused on the optical structure and power transfer efficiency of such systems. This invention, for the first time, proposes a system modeling and evaluation method for security, establishing a unified framework for quantitative measurement in multiple scenarios. It specifically models the intrusion plane of intrusive objects in intracavity laser-based wireless power transfer systems, classifying them into two categories: knife-edge intrusion and hair intrusion. This classification modeling method can be used to quantitatively measure the impact of different types of intrusive objects on the field distribution of the intracavity laser and the security of the wireless power transfer system, providing a reference for the security design and evaluation of subsequent intracavity laser-based wireless power transfer and related systems. Specifically, for eye security measurement, this invention combines three-dimensional anatomical modeling and ray trajectory tracking simulation to measure whether the intracavity laser can be focused on the retina, extending the retinal MPE to the corneal level.

[0054] Furthermore, the present invention also includes an electronic device comprising a central processing unit (CPU), which can perform various appropriate actions and processes according to computer program instructions stored in read-only memory (ROM) or loaded from storage units into random access memory (RAM). The RAM may also store various programs and data required for device operation. The CPU, ROM, and RAM are interconnected via a bus. Input / output (I / O) interfaces are also connected to the bus.

[0055] Multiple components in the device are connected to the I / O interface, including: input units such as keyboards and mice; output units such as various types of displays and speakers; storage units such as disks and optical discs; and communication units such as network interface cards (NICs), modems, and wireless transceivers. The communication unit allows the device to exchange information / data with other devices through computer networks such as the Internet and / or various telecommunications networks.

[0056] The processing unit executes the various methods and processes described above, such as methods S1 to S4. For example, in some embodiments, methods S1 to S4 may be implemented as computer software programs tangibly contained in a machine-readable medium, such as a storage unit. In some embodiments, part or all of the computer program may be loaded and / or installed on the device via ROM and / or a communication unit. When the computer program is loaded into RAM and executed by the CPU, one or more steps of methods S1 to S4 described above may be performed. Alternatively, in other embodiments, the CPU may be configured to execute methods S1 to S4 by any other suitable means (e.g., by means of firmware).

[0057] The functions described above in this document can be performed, at least in part, by one or more hardware logic components. For example, exemplary types of hardware logic components that can be used, without limitation, include: Field Programmable Gate Arrays (FPGAs), Application-Specific Integrated Circuits (ASICs), Application Standard Products (ASSPs), System-on-Chip (SoCs), Complex Programmable Logic Devices (CPLDs), and so on.

[0058] The program code used to implement the methods of the present invention can be written in any combination of one or more programming languages. This program code can be provided to a processor or controller of a general-purpose computer, special-purpose computer, or other programmable data processing device, such that when executed by the processor or controller, the program code causes the functions / operations specified in the flowcharts and / or block diagrams to be implemented. The program code can be executed entirely on the machine, partially on the machine, as a standalone software package partially on the machine and partially on a remote machine, or entirely on a remote machine or server.

[0059] In the context of this invention, a machine-readable medium can be a tangible medium that may contain or store a program for use by or in conjunction with an instruction execution system, apparatus, or device. A machine-readable medium can be a machine-readable signal medium or a machine-readable storage medium. Machine-readable media can include, but are not limited to, electronic, magnetic, optical, electromagnetic, infrared, or semiconductor systems, apparatus, or devices, or any suitable combination of the foregoing. More specific examples of machine-readable storage media include electrical connections based on one or more wires, portable computer disks, hard disks, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), optical fibers, portable compact disk read-only memory (CD-ROM), optical storage devices, magnetic storage devices, or any suitable combination of the foregoing.

[0060] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and these modifications or substitutions should all be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for security metric for distributed coupled cavity laser system, characterized in that, The method comprises: modeling a distributed coupled cavity laser system, obtaining key physical parameters and optical parameters of the system, constructing an intrusion plane model and a CRR equivalent plane model based on the key physical parameters and optical parameters, and the intrusion plane comprising a large intrusion plane and a small intrusion plane; taking the intrusion plane model and the CRR equivalent plane model as boundary conditions, constructing a diffraction-gain self-consistent equation set of bidirectional propagation of light beams in the system based on the key physical parameters and optical parameters, and introducing gain to perform iterative solving to obtain a steady-state light field distribution; calculating total illumination of a corresponding intrusion plane and an upper limit of output laser power of the system under a safe condition based on the steady-state light field distribution; selecting a proper value of an illumination safety threshold for each type of intrusion scene, comparing the proper value with the total illumination, and combining the upper limit of the output laser power to output a safety measurement result of the distributed coupled cavity laser system.

2. The method of claim 1, wherein, The invasion plane model of the large invasion plane is a knife-edge model, in which if a coordinate point of a coordinate system defined by an optical axis section plane of the distributed coupling cavity laser system satisfies a distance to an origin not more than an invasion plane radius and an x coordinate not more than an invasion position , then it is determined that an effective plane value corresponding to the point is 1, otherwise, it is determined that the effective plane value corresponding to the point is 0; The small invasion plane model is a rectangular barrier model, in which if the coordinate point satisfies the condition that the distance to the origin is not more than the invasion plane radius , then the effective plane value corresponding to the point is determined as 1; if the coordinate point satisfies the condition that the distance to the origin is more than the invasion plane radius , or the x coordinate and the y coordinate are respectively located in the interval and , then the effective plane value corresponding to the point is determined as 0; represents the coordinate of the small object in the invasion distributed coupling cavity laser system; represents the width of the small object; represents the length of the small object.

3. The method of claim 1, wherein, In the CRR equivalent plane model, for the i-th CRR, if the coordinate point satisfies the distance to the origin is not more than the radius of the lens and the mirror in the CRR , and the x coordinate is not more than the intrusion position , then it is determined that the effective plane value corresponding to the point is 1, otherwise, it is determined that the effective plane value corresponding to the point is 0.

4. The method of claim 1, wherein, The diffraction-gain self-consistent equation set is: ， in, This indicates that the diffraction-gain self-consistent equations are calculated in the nth iteration. This represents the optical field distribution in a free-space cavity within a distributed coupled-cavity laser system. This represents the optical field distribution in the main cavity of a distributed coupled-cavity laser system. This represents the operator used to describe one round trip of a light beam inside the main cavity, and has... , and This represents the reflection process of a light field. This represents the propagation process of a light field; Let represent the operator used to describe one round trip of a light beam in a free-space cavity, and have . , and These represent the processes of the light field reaching the intrusion plane and the light field reaching the reflecting mirror, respectively. and This represents the process of a light field being reflected by a mirror. This represents the process of a light field passing through an intruding plane or a reflecting mirror; This represents an operator used to describe the unidirectional propagation of beam energy from the main cavity to the free space cavity, and has... , This represents the propagation process of the energy field of the light beam. This represents the transmission process of an energy field; This represents an operator used to describe the unidirectional propagation of energy from the free-space cavity back to the main cavity, and has... ; and for each reflection and transmission process: ， ， ， ， ， representing the reflection operator of a mirror in the i-th CRR; representing the imaginary unit, representing the amplitude reflection coefficient of a mirror in the i-th CRR; representing the boundary condition in the i-th CRR, corresponding to the equivalent plane model of the i-th CRR; representing the reflection operator of a mirror in the i-th CRR; representing the amplitude reflection coefficient of a mirror in the i-th CRR; representing the amplitude transmission coefficient of a mirror in the i-th CRR; representing the transmission operator of a mirror in the i-th CRR; representing the transmission operator of a mirror in the i-th CRR; representing the intrusion plane model, and , representing the knife-edge model, representing the rectangular occlusion model; representing the propagation operator, and ; and representing the inverse Fourier transform and the Fourier transform, respectively; representing the transfer function; representing the spatial frequency; representing the wavelength of the light beam; representing the distance of the light beam propagation.​ 5. The method of claim 1, wherein, The iterative solving process is: assigning an initial guess value to the light field distribution of the free-space cavity and the inner cavity, solving the light field distribution of the free-space cavity and the inner cavity at the next iteration based on the initial guess value using the diffraction-gain self-consistent equation set, and for the nth iteration, the light field distribution is calculated based on the light field distribution of the (n-1)th iteration; for the inner cavity light field distribution and the free-space cavity light field distribution, updating the light field distribution to a new light field distribution considering saturated gain using a gain-coupling formula; calculating a cavity laser residual based on the new light field distribution, and if the cavity laser residual is less than a set threshold, determining convergence and ending the iteration, taking the corresponding new light field distribution as the steady-state light field distribution, otherwise, calculating the light field distribution of the next iteration based on the new light field distribution.

6. The method of claim 5, wherein, The gain-coupling formula is: ， wherein, represents the saturation intensity of the gain medium; represents the speed of light in vacuum; represents the vacuum permittivity; represents the intracavity light field distribution before entering the gain medium or the free space cavity light field distribution; represents the product log function; represents the small signal gain coefficient, and: ， represents the efficiency of converting pump power into gain, represents the power of the input pump, represents the volume of the gain medium; represents the length of the gain medium; represents an intermediate variable, and: 。 7. The method of claim 1, wherein, The method for calculating the total illumination is: Steady state light field distribution based on a free space cavity , obtaining a steady state light field distribution at a last mirror in the free space cavity ; based on and the steady state light field distribution of the free space cavity , the light field distribution before and after the intrusion plane is calculated, wherein the light field distribution before the intrusion plane is calculated based on the intrusion plane model , the propagation operator and ; the light field distribution after the intrusion plane is calculated based on the intrusion plane model , the propagation operator and ; calculating forward light field illumination and reverse light field illumination based on the light field distribution before the intrusion plane and the light field distribution after the intrusion plane, and the total illumination being the sum of the two.

8. The method of claim 1, wherein, The calculation method of the upper limit of the output laser power is: Based on the steady-state light field distribution at the last mirror in a free-space cavity The laser power output of the corresponding mirror is calculated based on the calculated illuminance of the laser on the corresponding mirror, and the expression is: ， wherein, represents the output laser power of the mirror; represents the transmissivity of the last mirror; represents the illumination value at the coordinates ; represents the speed of light in vacuum; represents the vacuum permittivity; using a maximum power point tracking method and dynamically adjusting the equivalent load resistance, and calculating a wireless charging current based on the output laser power, and the calculation method being: ， wherein, represents a response speed of the PV cell; represents a reverse saturation current; represents a elementary charge; represents a number of cells; represents an ideality factor of an internal equivalent diode of the cell; represents a Boltzmann constant; represents a Kelvin absolute temperature; , and respectively represent an equivalent load resistance, an internal equivalent series resistance, and an internal equivalent parallel resistance. drawing a charging current-voltage characteristic curve based on the wireless charging current, selecting a maximum power point based on the charging current-voltage characteristic curve, and the power value of the maximum power point being the upper limit of the output laser power. 。 9. The method of claim 1, wherein, The large intrusion plane comprises skin and the small intrusion plane comprises hair, for the skin a fixed maximum permissible exposure value is chosen As a proper value, when the total illuminance of the skin is less than then it is determined to be safe; For the hair, a fixed fast decay time threshold is selected as the proper value, wherein the fast decay time is the time required for the cavity light field of the distributed coupled cavity laser system to decay to a preset percentage when there is no intrusion plane obstruction.

10. The method of claim 1, wherein, The intrusion plane further comprises an eye, and the proper value selection method for the eye is: constructing a three-dimensional head model of the intrusion distributed coupled cavity laser system, calculating a minimum convex polyhedron, i.e., a convex hull, enclosing all points of the head model. For each circumscribed surface of the convex hull, the distance from the eye to the circumscribed surface is calculated, and the minimum value of the distance is taken; and the included angle between the eye normal vector and the circumscribed surface is calculated; Based on the minimum distance and the corresponding included angle, it is determined whether the laser will be focused on the retina, and if so, the first maximum permissible exposure value of the retina is selected as the appropriate value; If not focused on the retina, the second maximum permissible exposure value of the retina is selected as the appropriate value; And the first maximum permissible exposure value of the retina is much smaller than the second maximum permissible exposure value of the retina.

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