Backward stray light detection method based on heterodyne interference measurement principle

Abstract

The invention discloses a backward stray light detection method based on a heterodyne interference measurement principle, and the method comprises the steps: obtaining an actual received signal of a telescope, taking a small amount of emitted light beams as local reference laser, carrying out the interference with the received light beams, enabling a fixed frequency difference to exist, carrying out the balance detection of the actual received signal, obtaining a heterodyne signal, and carrying out the detection of the backward stray light according to the heterodyne signal. And phase information of back stray light is determined. Local reference laser is used for carrying out balance detection on an actual received signal, the local reference laser with large power and backward stray light with small power can be used for forming coherent laser superposition with a fixed frequency difference, and phase information of the backward stray light can be obtained from a light beat phenomenon generated by an obtained heterodyne signal. The phase information of the back stray light can be detected under the condition that the back stray light is weak, and data support is provided for elimination of the back stray light and use, maintenance and design of a telescope. The method is widely applied to the technical field of stray light detection.

Description

Technical Field

[0001] The present invention relates to the technical field of stray light detection, in particular to a method for detecting backward stray light based on the principle of heterodyne interference measurement. Background Art

[0002] When some telescopes are in operation, they emit and detect laser light towards the target to achieve related functions. For example, when a laser ranging telescope such as an interstellar laser interferometry telescope is in operation, it emits a very thin laser beam towards the target. The target reflects the laser beam back to the telescope, and the photoelectric element on the telescope side receives the reflected laser beam. The timer measures the time from the emission to the reception of the laser beam, and calculates the distance from the observer to the target.

[0003] Under ideal circumstances, the laser light related to the telescope is only the emitted laser light emitted by the equipment on the telescope side, and the received laser light reflected by the target and received by the equipment on the telescope side. However, due to environmental factors and the imperfections of the equipment itself, etc., some unwanted signals and noises are often introduced, forming backward stray light, which will affect the accuracy and stability of the measurement results. Backward stray light is usually very weak. For example, in a telescope with a micro field of view, the power of the backward stray light is at an ultra-weak level of only dozens of picowatts, which brings difficulties to the detection of backward stray light. Summary of the Invention

[0004] Aiming at the technical problems such as the interference of backward stray light faced by telescopes with laser measurement functions, the purpose of the present invention is to provide a method for detecting backward stray light based on the principle of heterodyne interference measurement.

[0005] The method for detecting backward stray light based on the principle of heterodyne interference measurement includes the following steps:

[0006] Obtain the actual received signal of the telescope; the actual received signal includes received laser light and backward stray light, and the received laser light is the signal light emitted by the opposite satellite received by the telescope;

[0007] Use a small amount of emitted light beams as local reference laser light, which interferes with the received light beam, and perform balanced detection on the actual received signal to obtain a heterodyne signal;

[0008] Determine the phase information of the backward stray light according to the heterodyne signal.

[0009] Further, the determining the phase information of the backward stray light according to the heterodyne signal includes:

[0010] Obtain the phase of the heterodyne signal;

[0011] Obtain the phase of the received laser light;

[0012] Determine the phase deviation generated by the backward stray light according to the phase of the heterodyne signal and the phase of the received laser.

[0013] Further, obtaining the phase of the heterodyne signal includes:

[0014] Input the heterodyne signal into a digital phase-locked loop for detection;

[0015] Obtain the phase of the heterodyne signal detected by the digital phase-locked loop.

[0016] Further, determining the phase information of the backward stray light according to the heterodyne signal further includes:

[0017] Obtain the heterodyne efficiency;

[0018] Obtain the total light intensity of the backward stray light;

[0019] Determine the phase magnitude of the backward stray light according to the heterodyne efficiency, the total light intensity of the backward stray light, and the phase deviation generated by the backward stray light.

[0020] Further, obtaining the total light intensity of the backward stray light includes:

[0021] Obtain the response signals of the telescope to the local reference laser and the backward stray light;

[0022] Determine the power information of the backward stray light according to the response signals;

[0023] Determine the total light intensity of the backward stray light according to the power information of the backward stray light.

[0024] Further, determining the power information of the backward stray light according to the response signals includes:

[0025] Obtain the DC component and the AC component of the response signals;

[0026] Obtain the heterodyne efficiency;

[0027] Determine the power information of the backward stray light according to the DC component, the AC component, the power of the local reference laser, and the heterodyne efficiency.

[0028] Further, determining the power information of the backward stray light according to the DC component, the AC component, the power of the local reference laser, and the heterodyne efficiency includes:

[0029] According to the formula

[0030] I DC = η·(P S + PLO )

[0031]

[0032] Calculate the power information of the backward stray light; wherein, I DC is the DC component, I AC is the AC component, ε is the heterodyne efficiency, P LO is the power of the local reference laser, P S is the power information of the backward stray light.

[0033] Further, determining the phase magnitude of the backward stray light according to the heterodyne efficiency, the total light intensity of the backward stray light, and the phase deviation generated by the backward stray light includes:

[0034] According to the formula

[0035]

[0036] Calculate the phase magnitude of the backward stray light; wherein, γ is the phase deviation generated by the backward stray light, ε is the heterodyne efficiency, u is the total light intensity of the backward stray light, and ψ is the phase magnitude of the backward stray light.

[0037] Further, determining the phase information of the backward stray light according to the heterodyne signal further includes:

[0038] Obtain the heterodyne efficiency;

[0039] Obtain the coherence intensity of the backward stray light;

[0040] Obtain the power of the local reference laser;

[0041] Determine the variance of the phase deviation generated by the backward stray light according to the heterodyne efficiency, the coherence intensity of the backward stray light, and the power of the local reference laser.

[0042] Further, determining the variance of the phase deviation generated by the backward stray light according to the heterodyne efficiency, the power information of the backward stray light, and the power of the local reference laser includes:

[0043] According to the formula

[0044]

[0045] Calculate the variance of the phase deviation generated by the backward stray light; wherein, ε is the heterodyne efficiency, I stray is the coherence intensity of the backward stray light, I ref is the power of the local reference laser.

[0046] The beneficial effects of the present invention are as follows: The method for detecting backward stray light based on the heterodyne interference measurement principle in the embodiment can perform balanced detection on the actual received signal by using a local reference laser, and can form a coherent laser superposition with a fixed frequency difference between the local reference laser with a relatively high power and the backward stray light with a relatively low power. The phase information of the backward stray light can be obtained from the optical beat phenomenon generated by the obtained heterodyne signal. Therefore, even when the backward stray light is weak, the phase information of the backward stray light can be detected, providing data support for the elimination of backward stray light, the use, maintenance, and design of the telescope. Description of the Drawings

[0047] Figure 1 It is a schematic diagram of the steps of the method for detecting backward stray light based on the heterodyne interference measurement principle in the embodiment;

[0048] Figure 2 It is a schematic diagram of the telescope system that can apply the method for detecting backward stray light based on the heterodyne interference measurement principle in the embodiment;

[0049] Figure 3 It is a schematic diagram of the principle of using a local reference laser to perform balanced detection on the actual received signal in the embodiment. Detailed Embodiment

[0050] In this embodiment, a method for detecting backward stray light based on the heterodyne interference measurement principle is provided. Referring to Figure 1 , the method for detecting backward stray light based on the heterodyne interference measurement principle includes the following steps:

[0051] S1. Obtain the actual received signal of the telescope;

[0052] S2. Use the emitted light beam as the local reference laser to interfere with the received light beam, with a fixed frequency difference. Perform balanced detection on the actual received signal to obtain a heterodyne signal;

[0053] S3. Determine the phase information of the backward stray light according to the heterodyne signal.

[0054] In this embodiment, the method for detecting backward stray light based on the heterodyne interference measurement principle can be applied to the Figure 2 shown telescope system. Referring to Figure 2 , taking the interstellar laser interferometric telescope as an example, the device on one side of the interstellar laser interferometric telescope emits a laser beam towards a target such as a star. The angular frequency of the emitted laser is ω1, and the power of the emitted laser is I Tx = 1W. After the emitted laser reaches the target and is reflected back to the position where the interstellar laser interferometric telescope is located, a received laser that can be detected by the device on one side of the interstellar laser interferometric telescope is formed. The angular frequency of the received laser is ω s, the power of the received laser is I Rx .

[0055] Factors such as surface scattering generated by the optical elements of the telescope, reflection of the emitted laser by objects other than the target such as spacecraft, and external stray light may all generate backscattered stray light. Assuming that these backscattered stray lights are all coaxial with the telescope, each beam of backscattered stray light can be expressed as

[0056]

[0057] where 2I0 is Figure 2 the power of the local reference laser used for parallel detection by the balanced detection module in n , u is the amplitude of the nth beam of backscattered stray light, then n is the intensity of the nth beam of backscattered stray light, ψ

[0058]

[0059] where u is the amplitude of the total backscattered stray light, u 2 =|∑u n exp(iψ n )| 2 is the total light intensity of the total backscattered stray light, ψ = arg[u n exp(iψ n )] is the phase of the total backscattered stray light (the coherent sum of the phases of all N beams of backscattered stray light).

[0060] In this embodiment, without special instructions, when referring to "backscattered stray light", it may refer to the total backscattered stray light.

[0061] In step S1, the actual received signal of the telescope can be obtained through Figure 2 the balanced detection module in Figure 2 . Referring to

[0062] In step S2, referring to Figure 2 , the balanced detection module also receives a beam of local reference laser. In this embodiment, the angular frequency of the local reference laser is the same as that of the emitted laser, which is ω1, and the power of the local reference laser is I ref = 2I0, specifically I ref= 2 mW. Generally, the power I of the received laser Rx and the power I of the local reference laser ref satisfy I Rx = a 2 I ref , where a 2 is a coefficient. Generally, a 2 = 3.5×10 -7 . Therefore, when I ref = 2 mW, the power I of the received laser Rx = a 2 I ref ≈ 700 pW. Moreover, the coherent intensity I stray of the total backward stray light and the power I ref of the local reference laser satisfy I stray = u 2 I ref . The magnitude of I stray is at the level of dozens of picowatts, that is, I stray is much smaller than I ref .

[0063] In step S2, the balanced detection module uses the local reference laser to perform balanced detection on the actual received signal to obtain the heterodyne signal. The balanced detection module executes step S3 and determines the phase information of the backward stray light according to the heterodyne signal detected in step S2. Specifically, the phase information of the backward stray light includes information such as the magnitude of the phase of the backward stray light, the phase deviation generated by the backward stray light on the phase of the received laser, and the variance of the phase deviation generated by the backward stray light on the phase of the received laser.

[0064] In this embodiment, the principle of executing steps S1 - S3 is as follows: Using the local reference laser to perform balanced detection on the actual received signal can form a coherent laser superposition with a fixed frequency difference between the local reference laser with a larger power and the backward stray light with a smaller power. The phase information of the backward stray light can be obtained from the optical beat phenomenon generated by the obtained heterodyne signal. Thus, even in the case where the backward stray light is weak, the phase information of the backward stray light can be detected, providing data support for the suppression of the backward stray light, the use, maintenance, and design of the telescope.

[0065] For example, the phase information of the backscattered stray light may include the optical path change when the laser beam propagates in the telescope, thus including the structural deformation information of the telescope. Therefore, the performance of the telescope can be detected by analyzing the phase information of the backscattered stray light, which provides value for improving the optical path stability and optical system stability of the telescope. Specifically, the optical path optimization, integrated structural function design, equal arm length adjustment, equal stiffness design, etc. of the telescope can be guided according to the information of the backscattered stray light, so as to effectively improve the signal-to-noise ratio, reduce the errors and drifts of the system, and then achieve a more accurate measurement effect and improve the performance and reliability of the measurement system.

[0066] In this embodiment, when performing step S2, that is, using the local reference laser to perform balanced detection on the actual received signal to obtain the heterodyne signal, the process is as Figure 3 shown. Figure 3 In the figure, the balanced detection module includes components such as a coupler, a first photodiode, and a second photodiode.

[0067] Referring to Figure 3 , balanced detection is to input the local reference laser and the actual received signal (including the received laser and the backscattered stray light) into the coupler in the balanced detection module. The coupler reflects and transmits the local reference laser and the actual received signal respectively. Among them, the reflected light of the actual received signal and the transmitted light of the local reference laser (local oscillator light) form signal E1 and project it onto the first photodiode in the balanced detection module, causing the first photodiode to generate a signal in the form of a photocurrent; the transmitted light of the actual received signal and the reflected light of the local reference laser (local oscillator light) form signal E2 and project it onto the second photodiode in the balanced detection module, causing the second photodiode to generate a signal in the form of a photocurrent. The signal generated by the first photodiode and the signal generated by the second photodiode form a heterodyne signal, which is used as the heterodyne signal output by the balanced detection module.

[0068] In this embodiment, taking the total backscattered stray light including two beams of backscattered stray light with amplitudes u1 and u2 as an example, E1 and E2 can be respectively expressed as

[0069]

[0070]

[0071] Among them, Ω a is the heterodyne frequency, that is, Ω a is the angular frequency ω s of the received laser minus the angular frequency (which is also the angular frequency of the local reference laser) ω1 of the transmitted laser, that is, Ω a = ω s-ω1, a1 is the response efficiency of the first photodiode, a2 is the response efficiency of the second photodiode, φ is the phase of the received laser, ψ is the phase of the total backscattered stray light, t is the time, i is the unit imaginary number, and e is the base of the natural logarithm.

[0072] The same factors are ignored in the expressions (3) and (4) of E1 and E2 Based on formulas (3) and (4), it is possible to Figure 3 express the heterodyne signal output by the balanced detection module in

[0073]

[0074] In this embodiment, when performing step S3, that is, the step of determining the phase information of the backscattered stray light according to the heterodyne signal, the following steps can be specifically performed:

[0075] S301. Obtain the phase of the heterodyne signal;

[0076] S302. Obtain the phase of the received laser;

[0077] S303. Determine the phase deviation generated by the backscattered stray light according to the phase of the heterodyne signal and the phase of the received laser;

[0078] S304. Obtain the heterodyne efficiency;

[0079] S305. Obtain the total light intensity of the backscattered stray light;

[0080] S306. Determine the phase magnitude of the backscattered stray light according to the heterodyne efficiency, the total light intensity of the backscattered stray light, and the phase deviation generated by the backscattered stray light;

[0081] S307. Obtain the coherence intensity of the backscattered stray light;

[0082] S308. Obtain the power of the local reference laser;

[0083] S309. Determine the variance of the phase deviation generated by the backscattered stray light according to the heterodyne efficiency, the coherence intensity of the backscattered stray light, and the power of the local reference laser.

[0084] Step S3 is applied to the IQ demodulation technique. By utilizing the characteristics of the quadrature modulation signal, the complex signal is decomposed into two orthogonal signal components through mixing and filtering processes, and then the signal phase information is obtained. Among them, steps S301 - S303 are the steps for detecting the phase deviation generated by the backscattered stray light on the phase of the received laser, steps S304 - S306 are the steps for detecting the phase magnitude of the backscattered stray light, and steps S307 - S309 are the steps for detecting the variance of the phase deviation generated by the backscattered stray light. The phase deviation and its variance generated by the backscattered stray light, together with the phase magnitude of the backscattered stray light, constitute the phase information of the backscattered stray light.

[0085] In steps S301 - S303, when performing step S301, for the heterodyne signals shown in formulas (5) and (6), the heterodyne signals can be input into a digital phase - locked loop for detection. The digital phase - locked loop is based on the formula

[0086]

[0087] for calculation, and then outputs the phase φ of the heterodyne signal. m . In formula (7), n represents the integration period. The phase φ of the heterodyne signal m can be specifically expressed as

[0088] (8)

[0090] In formula (8), δ(u1, u2, ψ) is a higher - order small quantity with respect to u1, u2, and ψ. In actual calculation, δ(u1, u2, ψ) can be taken as 0. Moreover, the efficiencies of the first photodiode and the second photodiode in the balanced detection module are usually relatively close, that is, a1≈a2. Therefore, in formula (8), there is:

[0091]

[0092] When performing step S302, since the received laser in the actual received signal is relatively strong (at the level of several hundred picowatts in power), the phase of the actual received signal can be detected, thereby obtaining the phase φ of the received laser.

[0093] When performing step S303, according to the phase φ m of the heterodyne signal detected in step S301

[0094] and the phase φ of the received laser detected in step S302, the phase deviation γ generated by the backscattered stray light can be calculated according to the formula m γ = φ

[0095] - φ (10)

[0096] In steps S304 - S306, when performing step S304, the reflectivity and transmittance of the coupler in the balance detection module as shown in Figure 2 can be obtained, and the reflectivity is expressed as 1 + ε, or the transmittance is expressed as 1 - ε, thereby obtaining the heterodyne efficiency. Moreover, by introducing the composite asymmetry parameter ε to represent the deviation of the two paths of stray light, there is:

[0097]

[0098] When performing step S305, first, the response signals of the telescope to the local reference laser and the backward stray light are obtained. Actually, it is equivalent to the response signals of the balance detection module to the local reference laser and the backward stray light. Since the backward stray light has a fixed difference frequency with the emitted laser and the local reference laser, when the backward stray light and the local reference laser are superimposed in the coupler of the balance detection module, the response on the balance detection module can be expressed using the wave equation as:

[0099]

[0100] where η represents the response efficiency of the photodiode, and specifically, η = a1 = a2 can be taken, P S represents the power of the backward stray light, P LO represents the power of the local reference light, ε represents the heterodyne efficiency, ω het represents the frequency difference between the backward stray light and the local reference laser, represents the phase difference between the backward stray light and the local reference laser.

[0101] According to formula (12), the response on the balance detection module includes a DC component

[0102] I DC = η·(P S + P LO ) (13)

[0103] and an AC component

[0104]

[0105] two parts. Since the power of the backward stray light is only dozens of picowatts, the DC component mainly depends on the power of the local reference beam; and due to the reason of coherent enhancement, the amplitude of the AC component is greatly increased under the influence of the local reference light, thereby greatly improving the detection ability of the backward stray light. Later, by distinguishing the magnitudes of the DC component and the AC component, the power of the backward scattered light of the ultra-precise and ultra-stable telescope can be obtained, and the measurement of the backward stray light flux is realized.

[0106] Specifically, the DC component I DC and the AC component I in formulas (13) and (14)AC , the specific values of the power P of the local reference light LO and the heterodyne efficiency ε, etc. are known. Therefore, the power information P of the backscattered stray light can be calculated by simultaneously solving formulas (13) and (14). S .

[0107] When performing step S305, according to the physical relationship between the power and intensity of the laser, the total light intensity u of the backscattered stray light can be determined based on the power information P of the backscattered stray light. S

[0108] When performing step S306, according to formulas (8)-(10), the phase deviation γ caused by the backscattered stray light can be expressed as

[0109]

[0110] By solving formula (15) according to the phase deviation γ detected in step S303, the heterodyne efficiency ε obtained in step S304, and the total light intensity u detected in step S305, the phase magnitude ψ of the total backscattered stray light can be obtained.

[0111] In steps S307-S309, when performing step S307, after detecting the power I of the local reference laser ref and the total light intensity u of the backscattered stray light, according to I stray = u 2 I ref the coherence intensity I of the backscattered stray light can be calculated. stray .

[0112] When performing step S308, it can be detected that the power of the local reference laser is I ref .

[0113] It can be assumed that the phase deviation caused by the backscattered stray light is equally probable within a certain range. This equally probable range is usually [-π, π]. According to Euler's formula, we have:

[0114]

[0115] According to formula (16), we have:

[0116]

[0117] where < > represents taking the average value.

[0118] Also, because:

[0119]

[0120] Therefore:

[0121]

[0122] According to formula (19), the variance of the phase deviation caused by the backward stray light satisfies:

[0123]

[0124] Therefore, when performing step S309, the variance of the phase deviation caused by the backward stray light can be calculated according to formula (20).

[0125] A computer program for implementing the backward stray light detection method based on the heterodyne interferometry principle in this embodiment can be written, and this computer program can be written into a computer device or a storage medium. When the computer program is read and run, the backward stray light detection method based on the heterodyne interferometry principle in this embodiment is executed, so as to achieve the same technical effect as the backward stray light detection method based on the heterodyne interferometry principle in the embodiment.

[0126] It should be noted that, unless otherwise specified, when a certain feature is referred to as "fixed" or "connected" to another feature, it can be directly fixed or connected to another feature, or indirectly fixed or connected to another feature. In addition, the up, down, left, right, etc. descriptions used in the present disclosure are only relative to the mutual positional relationship of the various components of the present disclosure in the drawings. The singular forms "a", "an" and "the" used in the present disclosure are also intended to include the plural forms, unless the context clearly indicates otherwise. In addition, unless otherwise defined, all technical and scientific terms used in this embodiment have the same meaning as commonly understood by those skilled in the technical field of the present invention. The terms used in the description of this embodiment of the specification are only for describing specific embodiments, and are not intended to limit the present invention. The term "and / or" used in this embodiment includes any and all combinations of one or more of the related listed items.

[0127] It should be understood that although the terms first, second, third, etc. may be used in the present disclosure to describe various elements, these elements should not be limited to these terms. These terms are only used to distinguish elements of the same type from each other. For example, without departing from the scope of the present disclosure, the first element may also be referred to as the second element, and similarly, the second element may also be referred to as the first element. The use of any and all examples or exemplary languages ("for example", "such as", etc.) provided in this embodiment is only intended to better illustrate the embodiments of the present invention, and will not impose a limitation on the scope of the present invention unless otherwise required.

[0128] It should be recognized that embodiments of the present invention can be implemented or carried out by computer hardware, a combination of hardware and software, or by computer instructions stored in a non-transitory computer-readable memory. The methods can be implemented in a computer program using standard programming techniques - including a non-transitory computer-readable storage medium configured with the computer program, where the storage medium so configured causes the computer to operate in a specific and predefined manner - in accordance with the methods and drawings described in the specific embodiments. Each program can be implemented in a high-level procedural or object-oriented programming language to communicate with the computer system. However, if desired, the program can be implemented in assembly or machine language. In any case, the language can be a compiled or interpreted language. Additionally, for this purpose the program is capable of running on a programmed application-specific integrated circuit.

[0129] In addition, the operations of the processes described in this embodiment can be performed in any suitable order, unless this embodiment otherwise indicates or is otherwise clearly contradicted by the context. The processes described in this embodiment (or variations and / or combinations thereof) can be executed under the control of one or more computer systems configured with executable instructions, and can be implemented as code (e.g., executable instructions, one or more computer programs, or one or more applications) executed jointly on one or more processors, by hardware, or a combination thereof. A computer program includes a plurality of instructions executable by one or more processors.

[0130] Furthermore, the method can be implemented in any type of computing platform operatively connected as appropriate, including but not limited to personal computers, minicomputers, mainframes, workstations, network or distributed computing environments, standalone or integrated computer platforms, or communicating with charged particle tools or other imaging devices, etc. Aspects of the present invention can be implemented in machine-readable code stored on a non-transitory storage medium or device, whether removable or integrated into the computing platform, such as a hard disk, optical read and / or write storage medium, RAM, ROM, etc., such that it can be read by a programmable computer and, when the storage medium or device is read by the computer, can be used to configure and operate the computer to perform the processes described herein. Additionally, the machine-readable code, or portions thereof, can be transmitted via a wired or wireless network. When such media includes instructions or programs that implement the above steps in conjunction with a microprocessor or other data processor, the invention of this embodiment includes these and other different types of non-transitory computer-readable storage media. When programmed in accordance with the methods and techniques of the present invention, the present invention also includes the computer itself.

[0131] A computer program can be applied to input data to perform the functions of this embodiment, thereby converting the input data to generate output data stored in a non-volatile memory. The output information can also be applied to one or more output devices such as a display. In a preferred embodiment of the present invention, the converted data represents physical and tangible objects, including specific visual depictions of physical and tangible objects generated on a display.

[0132] The above are only the preferred embodiments of the present invention. The present invention is not limited to the above-described embodiments. As long as it achieves the technical effects of the present invention by the same means, any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention. Within the scope of protection of the present invention, its technical solutions and / or implementation manners can have various different modifications and changes.

Claims

1. A method for detecting backscattered stray light based on the principle of heterodyne interferometry, applied to a telescope, characterized in that, The backscattered stray light detection method based on the heterodyne interference measurement principle includes: Obtain the actual received signal of the telescope; the actual received signal includes received laser light and backscattered stray light, and the received laser light is the signal light emitted by the opposite satellite received by the telescope; Use the transmitted light beam as the local reference laser, interfere with the received light beam, there is a fixed frequency difference, and perform balanced detection on the actual received signal to obtain the heterodyne signal; Determine the phase information of the backscattered stray light according to the heterodyne signal.

2. The method for detecting backscattered stray light based on the heterodyne interference measurement principle according to claim 1, wherein The determining the phase information of the backscattered stray light according to the heterodyne signal includes: Obtain the phase of the heterodyne signal; Obtain the phase of the received laser light; Determine the phase deviation generated by the backscattered stray light according to the phase of the heterodyne signal and the phase of the received laser light.

3. The method for detecting backscattered stray light based on the heterodyne interference measurement principle according to claim 2, wherein The obtaining the phase of the heterodyne signal includes: Input the heterodyne signal into a digital phase-locked loop for detection; Obtain the phase of the heterodyne signal detected by the digital phase-locked loop.

4. The backscattered stray light detection method based on the heterodyne interference measurement principle according to claim 2, wherein The determining the phase information of the backscattered stray light according to the heterodyne signal further includes: Obtain the heterodyne efficiency; Obtain the total light intensity of the backscattered stray light; Determine the phase magnitude of the backscattered stray light according to the heterodyne efficiency, the total light intensity of the backscattered stray light, and the phase deviation generated by the backscattered stray light.

5. The backscattered stray light detection method based on the heterodyne interference measurement principle according to claim 4, characterized in that The obtaining the total light intensity of the backscattered stray light includes: Obtain the response signals of the telescope to the local reference laser and the backscattered stray light; Determine the power information of the backscattered stray light according to the response signals; Determine the total light intensity of the backscattered stray light according to the power information of the backscattered stray light.

6. The method for detecting backscattered stray light based on the heterodyne interference measurement principle according to claim 5, wherein The determining the power information of the backscattered stray light according to the response signals includes: Obtain the DC component and AC component of the response signals; Obtain the heterodyne efficiency; Determine the power information of the backscattered stray light according to the DC component, the AC component, the power of the local reference laser, and the heterodyne efficiency.

7. The backscattered stray light detection method based on the heterodyne interference measurement principle according to claim 6, characterized in that, The determining the power information of the backscattered stray light according to the DC component, the AC component, the power of the local reference laser, and the heterodyne efficiency includes: According to the formula I DC = η·(P S + P LO ) Calculate the power information of the backward stray light; where, I DC is the DC component, I AC is the AC component, ε is the heterodyne efficiency, P LO is the power of the local reference laser, P S is the power information of the backward stray light.

8. The backscattered stray light detection method based on the heterodyne interference measurement principle according to claim 4, wherein The determining the phase magnitude of the backscattered stray light according to the heterodyne efficiency, the total light intensity of the backscattered stray light, and the phase deviation generated by the backscattered stray light includes: According to the formula Calculate the phase magnitude of the backscattered stray light; where γ is the phase deviation generated by the backscattered stray light, ε is the heterodyne efficiency, u is the total light intensity of the backscattered stray light, and ψ is the phase magnitude of the backscattered stray light.

9. The method for detecting backscattered stray light based on the heterodyne interference measurement principle according to any one of claims 2-8, characterized in that, The determining the phase information of the backscattered stray light according to the heterodyne signal further includes: Obtain the heterodyne efficiency; Obtain the coherence intensity of the backscattered stray light; Obtain the power of the local reference laser; Determine the variance of the phase deviation generated by the backscattered stray light according to the heterodyne efficiency, the coherence intensity of the backscattered stray light, and the power of the local reference laser.

10. The method for detecting backscattered stray light based on the heterodyne interference measurement principle according to claim 9, wherein The determining the variance of the phase deviation generated by the backscattered stray light according to the heterodyne efficiency, the power information of the backscattered stray light, and the power of the local reference laser includes: According to the formula Calculate the variance of the phase deviation generated by the backward stray light; where ε is the heterodyne efficiency, I stray is the coherent intensity of the backward stray light, I ref is the power of the local reference laser.

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