Method for compensating beam divergence angle of laser beam

Abstract

A method for compensating for a beam divergence angle of a laser beam is provided. The method comprises the steps that a compensation device is arranged at the laser beam emitting end of a device to be compensated, the compensation device at least comprises a liquid lens, and the liquid lens at least comprises a liquid lens cavity and liquid contained in the liquid lens cavity. The method further comprises the step of determining a second beam divergence angle of a second laser beam emitted by the laser beam emitted by the device to be compensated through the compensation device. The method further includes determining a voltage that needs to be applied to the liquid lens based on the second beam divergence angle. In addition, the method further comprises the step of driving the liquid lens to deform based on the voltage so as to compensate the beam divergence angle of the laser beam, so that the difference value between the compensated beam divergence angle and the expected beam divergence angle of the laser beam in the to-be-applied environment meets a preset condition. In this way, through the adjustable deformation of the liquid lens, the change of the laser beam divergence angle caused by the difference between the test environment and the to-be-applied environment is compensated, so that the accurate simulation test of the to-be-applied environment is realized.

Description

Technical Field

[0001] The invention relates to the field of laser application, and in particular to a method for compensating a beam divergence angle of a laser beam. Background Art

[0002] Lasers are widely used in the fields of laser radar, laser communication and gas composition analysis. In different environments, the temperature and laser propagation medium will be quite different. The difference in the medium will cause the refractive index to change, and the temperature will cause the refractive index of the propagation medium to change. These will cause the laser light source to defocus, and the defocus of the optical system will cause the laser beam divergence to change. In the field of space applications (for example, inter-satellite laser communication), the laser propagation medium is a vacuum, and the temperature of the optical equipment in the vacuum environment is variable. During ground testing, if the optical equipment is placed in a vacuum environment to measure and simulate the temperature in the vacuum environment, it will be time-consuming and laborious. Therefore, simulating the laser beam in a vacuum with multiple temperature fields in a normal temperature air medium has great practical value. In the field of environmental testing, laser spectroscopy is often used for gas composition analysis. Before performing gas composition analysis, its optical parameters need to be adapted. The laser beam divergence is one of the important parameters. Therefore, simulating the laser beam divergence in a gas chamber environment in a normal temperature air environment can provide convenience for actual gas analysis.

[0003] In order to overcome the problem of beam divergence difference caused by the difference between the normal temperature air test environment and the application environment, the traditional method is to add gaskets in the optical system. When the gaskets are added to the measurement room under the normal temperature air environment, when the test is completed and it is used in the real environment, the gaskets are removed. However, this method requires the installation and removal of gaskets, which is time-consuming and laborious. Another method is to add lens compensation to the optical system, but the compensation device is generally fixed and has no closed loop, and is not universally applicable to different application environments.

[0004] In summary, the method for compensating the beam divergence angle of the laser beam has the following disadvantages: it requires additional installation and removal of gaskets, which is time-consuming and labor-intensive; the added compensation device is fixed and cannot be adjusted in a closed loop, making it difficult to adapt to different application environments. Summary of the invention

[0005] The present invention provides a method for compensating for the divergence angle of a laser beam, which can not only conveniently compensate for the change in the divergence angle of the laser beam caused by the difference between a test environment and an application environment, but also realize accurate simulation tests for different application environments.

[0006] In order to overcome the problems existing in the prior art, the present invention provides a method for compensating the beam divergence angle of a laser beam. The method comprises: setting a compensation device at the laser beam emitting end of the device to be compensated, the compensation device comprising at least a liquid lens, the liquid lens comprising at least a liquid lens chamber and a liquid contained in the liquid lens chamber; determining the second beam divergence angle of a second laser beam emitted by the laser beam emitted by the device to be compensated through the compensation device; determining the voltage to be applied to the liquid lens based on the second beam divergence angle; and driving the liquid lens to deform based on the voltage to compensate for the beam divergence angle of the laser beam, so that the difference between the compensated beam divergence angle and the expected beam divergence angle of the laser beam in the environment to be applied satisfies a predetermined condition.

[0007] In some embodiments, the method also includes: the liquid lens is located between the beam reducer and the beam expander and is controlled by a drive control device, and the compensation device also includes: the beam reducer, located at one end of the liquid lens close to the emission end, and configured to reduce the laser beam by a given multiple; and the beam expander, located at the other end of the liquid lens away from the emission end, and configured to enlarge the laser beam by a given multiple.

[0008] In some embodiments, the method also includes: the application environment is one of a space environment and a predetermined gas environment, and determining the voltage that needs to be applied to the liquid lens based on the second beam divergence angle includes: determining the initial voltage applied to the liquid lens based on the second beam divergence angle; determining the voltage fine-tuning parameter based on the comparison between the second beam divergence angle and the expected beam divergence angle; and determining the voltage that needs to be applied to the liquid lens based on the initial voltage and the voltage fine-tuning parameter.

[0009] In some embodiments, determining the initial voltage applied to the liquid lens based on the second beam divergence angle includes: determining the initial voltage applied to the liquid lens based on the second beam divergence angle, the beam waist radius and wavelength of the laser beam, and relevant parameters of the liquid lens.

[0010] In some embodiments, the relevant parameters of the liquid lens include the radius of the liquid lens cavity, the interfacial tension, the dielectric constant, the refractive index of the liquid, the thickness of the dielectric layer, and the initial equilibrium angle between the conductive droplet and the insulating dielectric layer.

[0011] In some embodiments, the method further includes: determining the waist radius of the laser beam based on the wavelength of the laser beam and the waist radius in the application environment, the equivalent lens focal length and the equivalent lens refractive index of the device to be compensated in the application environment, and the refractive index of the air in the test environment where the laser beam is located.

[0012] In some embodiments, the method further includes determining a voltage trim parameter that is not zero in response to a difference between the second beam spread angle and the desired beam spread angle being greater than a threshold deviation.

[0013] In some embodiments, the method further includes determining the expected beam divergence angle based on the beam waist radius of the laser beam in the environment to be applied and the refractive index of the optical propagation medium in the environment to be applied, and the equivalent lens focal length and equivalent lens refractive index of the device to be compensated in the environment to be applied.

[0014] In some embodiments, the method further includes determining the refractive index of the optical propagation medium in the environment to be used based on the refractive index and the refractive index variation of the environment to be used at a standard given temperature.

[0015] In some embodiments, the method further includes determining the amount of change in the refractive index based on the wavelength of the laser beam, compensation coefficients under different media, a standard given temperature, and a temperature of the environment to be applied.

[0016] The beneficial effect of the above method is that it provides a compensation device with a liquid lens, which is universal for different application environments and can be adjusted in a closed loop so that the beam divergence angle of the laser emitted from the compensation device in a normal temperature test environment is consistent with that in the application environment, thereby achieving a test effect consistent with the actual system performance in a normal temperature test environment.

[0017] It should be understood that the contents described in the summary of the invention are not intended to limit the key or important features of the embodiments of the present disclosure, nor are they intended to limit the scope of the present disclosure. Other features of the present disclosure will become easily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The above and other features, advantages and aspects of the embodiments of the present disclosure will become more apparent with reference to the following detailed description in conjunction with the accompanying drawings. In the accompanying drawings, the same or similar reference numerals represent the same or similar elements.

[0019] Figure 1 A schematic diagram of a method for compensating for laser beam divergence according to some embodiments of the present invention is shown.

[0020] Figure 2 A flow chart of a method for compensating for laser beam divergence according to some embodiments of the present invention is shown.

[0021] Figure 3 A schematic diagram of a system for compensating for laser beam divergence according to some embodiments of the present invention is shown.

[0022] Figure 4 A flow chart of a method for implementing laser beam divergence compensation according to some embodiments of the present invention is shown.

[0023] Throughout the drawings, the same or similar reference numbers denote the same or similar elements. DETAILED DESCRIPTION

[0024] Embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although certain embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be construed as being limited to the embodiments described herein, which are instead provided for a more thorough and complete understanding of the present disclosure. It should be understood that the drawings and embodiments of the present disclosure are only for exemplary purposes and are not intended to limit the scope of protection of the present disclosure.

[0025] In the description of the embodiments of the present disclosure, the term "including" and similar terms should be understood as open inclusion, that is, "including but not limited to". The term "based on" should be understood as "based at least in part on". The term "one embodiment" or "the embodiment" should be understood as "at least one embodiment". The terms "first", "second", etc. may refer to different or the same objects. Other explicit and implicit definitions may also be included below.

[0026] Figure 1 Schematic diagram of a method for compensating for laser beam divergence according to some embodiments of the present invention is shown. Figure 1 As shown, the device 100 to be compensated emits a laser beam 102, and the laser beam 102 reaches the second beam divergence calculation device 110 via the compensation device 104. The device 100 to be compensated may be, for example, an optical device, equipment or system including a laser. The compensation device 104 includes at least a liquid lens 106, and the liquid lens 106 includes at least a liquid lens cavity and a liquid contained in the liquid lens cavity (not shown in the figure). The shape of the liquid lens cavity changes with the voltage 116 applied to the liquid lens 106, so that the shape of the liquid contained therein also changes. Correspondingly, the refractive index and focal length of the liquid lens also change with the change of the voltage 116. After passing through the compensation device 104, the laser beam 102 becomes a second laser beam 108, and its beam divergence angle (in order to distinguish it from the beam divergence angle of the laser beam 102, it is also called "second beam divergence angle 112") is different from the beam divergence angle of the laser beam 102.

[0027] In some embodiments, the second beam divergence angle calculation device 110 may include a camera, an image acquisition device, and a computing device. The image acquisition device may be, for example, a scanner, an image acquisition card, etc. The computing device may be a personal computer, a workstation, a server, a tablet computer, an industrial control computer, a graphics processing unit computing device, a digital signal processing device, a programmable logic controller, a field programmable gate array device, etc. The second beam divergence angle calculation device 110 may, for example, calculate the second beam divergence angle 112 of the second laser beam 108 based on the spot image of the second laser beam 108 captured by the camera and the information obtained by the image processing of the image acquisition device and other parameters.

[0028] In some embodiments, the voltage calculation device 114 may be the same calculation device as the second beam divergence calculation device 110, or may be a different calculation device. The voltage calculation device 114 can calculate the voltage 116 that needs to be applied to the liquid lens 106 according to the second beam divergence 112, and apply the voltage 116 to the liquid lens 106 through a voltage applying device (not shown in the figure), thereby changing the refractive index and focal length of the liquid lens 106. Through such a closed-loop adjustment, the second beam divergence 112 can gradually approach the desired beam divergence of the laser beam 102 in the environment to be applied, and finally achieve the effect that the difference between the second beam divergence 112 and the desired beam divergence meets the predetermined condition.

[0029] In this way, through the adjustable deformation of the liquid lens 106, the change of the laser beam divergence angle caused by the difference between the test environment and the environment to be applied is compensated, thereby achieving an accurate simulation test of the environment to be applied.

[0030] Figure 2 A flow chart of a method for compensating for laser beam divergence according to some embodiments of the present invention is shown. In some embodiments, the actions in the flow may further include additional actions not shown and / or the actions shown may be omitted, and the scope of the present disclosure is not limited in this respect.

[0031] exist Figure 2 In S1, a compensation device 104 is provided at the laser beam emitting end of the device to be compensated 100, and the compensation device 104 at least includes a liquid lens 106, and the liquid lens 106 at least includes a liquid lens cavity and a liquid contained in the liquid lens cavity.

[0032] exist Figure 2 In S2, a second beam divergence angle 112 of a second laser beam 108 emitted by the device to be compensated 104 and passing through the compensation device 104 is determined.

[0033] exist Figure 2 In S3 , based on the second beam divergence angle 112 , a voltage 116 that needs to be applied to the liquid lens 106 is determined.

[0034] exist Figure 2 In S4 , based on the voltage 116 , the liquid lens 106 is driven to deform to compensate for the beam divergence angle of the laser beam 102 , so that the difference between the compensated beam divergence angle and the expected beam divergence angle of the laser beam 102 in the application environment satisfies a predetermined condition.

[0035] The predetermined condition may be that a difference between the compensated beam spread angle and the desired beam spread angle is within a threshold deviation range.

[0036] Figure 3FIG. 3 is a schematic diagram showing a system 300 for compensating for laser beam divergence according to some embodiments of the present invention. Figure 3 As shown, the system 300 includes an optical vibration isolation platform 332, a device to be compensated 302, a compensation device 314, a bracket 1 334-1, a bracket 2 334-2, a bracket 3 334-3, a bracket 4 334-4, a drive control device 330, a computing device 328, an image acquisition device 326, and a camera 324. The device to be compensated 302 includes, for example, a laser 304, an optical fiber 306, a ferrule connector / bevel physical connector (FC / APC), and an optical collimating lens barrel 310. The bracket 1 334-1, the bracket 2 334-2, the bracket 3 334-3, and the bracket 4 334-4 are used to respectively realize the position fixation of the device to be compensated 302, the compensation device 314, the focusing lens 322, and the camera 324. The device to be compensated 302 has an equivalent lens 312 with the same effect as the device to be compensated 302, such as focal length, optical focal length, and aberration.

[0037] The compensation device 314 includes an optical beam reducer 316, a liquid lens 318 and an optical beam expander 320. The optical beam reducer 316 is located at one end of the liquid lens close to the emitting end of the device to be compensated 302, and can reduce the laser beam emitted from the device to be compensated 302 to adapt to the lens aperture size of the liquid lens 318. The reduced laser beam passes through the liquid lens 318 and is expanded by the optical beam expander 320. The optical beam expander 320 is located at the other end of the liquid lens 318 away from the emitting end of the device to be compensated 302, and can restore the laser beam to a laser beam of the same size as the beam emitted from the device to be compensated 302. In other words, the reduction factor of the optical beam reducer 316 is equal to the magnification factor of the optical beam expander 320. The liquid lens 318 includes a liquid lens cavity and two liquids. The radius of the liquid lens cavity is R, and the two liquids have refractive indices respectively. n l1 and n l2 One side of the liquid lens 318 is a flat surface, and its focal length f L The relationship between the applied voltage in the working area is (1) in, is the interfacial tension, is the dielectric constant, d is the thickness of the dielectric layer, θ0 is the initial equilibrium angle between the conductive droplet and the insulating dielectric layer, and U is the voltage applied to the liquid lens 318 by the drive control device 330.

[0038] After the laser beam passes through the compensation device 314, the spot image is captured by the camera 324. The image plane of the camera 324 is placed on the focal plane of the focusing lens 322. The far-field spot of the laser beam is measured online by the camera 324, and the current beam divergence angle is calculated. , the beam divergence angle Focal length with liquid lens 318 f L The geometric relationship is as follows: (2) Wherein, l is the distance between the laser emission end of the device to be compensated 302 and the compensation device 314, is the beam waist radius of the laser beam emitted from the device to be compensated 302 in the actual test environment (for example, room temperature air environment), and λ is the laser wavelength. Based on the following formula: (3) in, is the beam waist radius of the laser in the application environment, f is the focal length of the optical lens in the environment to be applied (e.g., space environment, given gas environment), n p is the refractive index of the equivalent lens of the device to be compensated 302 at the ambient temperature to be applied, n air is the refractive index of air in the test environment. The beam waist radius of the laser in the application environment can be obtained by the following formula: (4) in, is the expected beam divergence angle of the laser emitted by the device to be compensated 302 in the environment to be applied, and n' is the refractive index of the optical propagation medium at the temperature T0 of the environment to be applied, which is obtained by the following formula: (5) Where n is the application environment at the standard given temperature T s The refractive index under is the refractive index of the optical propagation medium at the ambient temperature T0 to be applied and the refractive index of the ambient temperature T0 to be applied s The difference in refractive index under , that is, the change in refractive index. n is known, It needs to be obtained through the following formula: (6) in, is the ambient temperature T0 to be applied and the standard given temperature T sThe difference between the two media, C0, C1, C2, and C3 represent the compensation coefficients under different media.

[0039] The image plane of the camera 324 is placed on the focal plane of the focusing lens 322, and the image acquisition device 326 obtains the spot image and beam divergence angle from the camera 324. The computing device 328 calculates the voltage required to be applied to the liquid lens 318 through the computing program stored therein, and transmits the voltage value to the driving control device 330, which applies voltage to the liquid lens 318, thereby changing the shape of the liquid lens cavity and then changing the focal length of the liquid lens, thereby compensating for the focal length change caused by the environmental change, thereby obtaining a compensated beam divergence angle whose difference from the expected beam divergence angle in the environment to be applied is within the threshold deviation range.

[0040] Combine the following Figure 4 A process for calculating the voltage that needs to be applied to the liquid lens 318 is described. Figure 4 1 is a flow chart of a method for implementing laser beam divergence compensation according to some embodiments of the present invention. The actions in the flow may also include additional actions not shown and / or the actions shown may be omitted. The scope of the present disclosure is not limited in this respect.

[0041] exist Figure 4 In S1, enter the parameters of the application environment and the desired beam divergence angle .

[0042] In some embodiments, the parameters to be input into the calculation program stored in the computing device 328 may include the laser wavelength, the temperature of the environment to be applied, the refractive index and focal length of the equivalent lens of the device to be compensated 302 at the temperature of the environment to be applied, the refractive index of the air in the test environment, the distance between the laser output end of the device to be compensated 302 and the compensation device 314, etc.

[0043] exist Figure 4 S2 in the calculation is used to calculate the laser beam waist radius before compensation in the test environment.

[0044] In some embodiments, the process can calculate the laser beam waist radius before compensation by using formula (3).

[0045] exist Figure 4 S3 in , calculate the voltage that needs to be applied to the liquid lens.

[0046] In this process, the voltage to be applied can be calculated by formula (1) and formula (2). The voltage obtained by the first calculation is the initial voltage, but the initial voltage cannot make the beam divergence angle of the laser beam emitted from the compensation device 314 consistent with the desired beam divergence angle (the deviation is within the threshold deviation), so it is necessary to repeat the process until the result of the judgment in S5 is yes.

[0047] exist Figure 4 S4 in the calculation calculates the compensated beam divergence angle.

[0048] This process is performed by, for example, the camera 324, and the calculated beam divergence angle is transmitted to the image acquisition device 326. Provided to a computing program in a computing device so that the computing program can determine the compensated beam divergence angle Is it consistent with the expected beam divergence angle? Consistent.

[0049] If the result is no, execute Figure 4 The process in S6, that is, setting the fine-tuning parameters.

[0050] In some embodiments, the fine-tuning parameter is set based on Figure 4 The comparison results of S5 in the With the desired beam divergence angle When the difference is greater than the threshold deviation, the value of the fine-tuning parameter is not 0, for example, it can be 0.9, 0.99, 0.999, etc., which can be adjusted according to the dispersion angle With the desired beam divergence angle The difference and threshold deviation are used to set the fine-tuning parameters. Figure 4 In the process of S3 in FIG. 1 , the calculation is no longer performed using formulas (1) and (2). Instead, the voltage to be applied to the liquid lens 318 is obtained by multiplying the product of the fine-tuning parameter and the initial voltage.

[0051] The step diagrams illustrate the possible implementation architectures, functions, and operations of the systems, methods, and computer hardware or software products according to various example embodiments of the present disclosure. In this regard, each step in the flow chart or step diagram may represent a portion of a module, segment, or code, which includes one or more executable instructions for implementing a specified logical function. It should be understood that in some alternative implementations, the functions indicated in the steps may not occur in the order shown in the figure. For example, two steps shown in succession may be performed or implemented substantially simultaneously, or sometimes two steps may be performed in reverse order, depending on the functions involved. Some steps may also be omitted. It should also be understood that each step in the step diagram and the combination of steps may be implemented by a dedicated hardware system that performs a specified function or action, or by a combination of dedicated hardware and computer instructions.

[0052] Other variations to the disclosed embodiments may be understood and effected by those skilled in the art in practicing the claimed invention by studying the drawings, the disclosure and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. Any reference signs in the claims should not be construed as limiting the scope.

Claims

1. A method for compensating a beam divergence angle of a laser beam, characterized in that: include: A compensation device is provided at the laser beam emitting end of the device to be compensated, wherein the compensation device at least comprises a liquid lens, and the liquid lens at least comprises a liquid lens cavity and a liquid contained in the liquid lens cavity; determining a second beam divergence angle of a second laser beam emitted by the device to be compensated through the compensation device; Based on the second beam divergence angle, determining a voltage to be applied to the liquid lens; as well as Based on the voltage, the liquid lens is driven to deform to compensate for the beam divergence angle of the laser beam, so that the difference between the compensated beam divergence angle and the expected beam divergence angle of the laser beam in the application environment meets a predetermined condition.

2. The method according to claim 1, characterized in that The liquid lens is located between the beam reducer and the beam expander and is controlled by a driving control device, and the compensation device also includes: A beam reducer, located at one end of the liquid lens close to the emission end, configured to reduce the laser beam by a given factor; and A beam expander is located at the other end of the liquid lens away from the emitting end, and is configured to amplify the laser beam to the given multiple.

3. The method according to claim 1, characterized in that The application environment is one of a space environment and a predetermined gas environment, and determining the voltage to be applied to the liquid lens based on the second beam divergence angle includes: determining an initial voltage applied to the liquid lens based on the second beam divergence angle; determining a voltage fine tuning parameter based on a comparison of the second beam spread angle with a desired beam spread angle; and The voltage to be applied to the liquid lens is determined based on the initial voltage and the voltage fine-tuning parameter.

4. The method according to claim 3, characterized in that Based on the second beam divergence angle, determining an initial voltage applied to the liquid lens comprises: The initial voltage applied to the liquid lens is determined based on the second beam divergence angle, the beam waist radius and the wavelength of the laser beam and relevant parameters of the liquid lens.

5. The method according to claim 4, characterized in that The relevant parameters of the liquid lens include: the radius of the liquid lens cavity, the interfacial tension, the dielectric constant, the refractive index of the liquid, the thickness of the dielectric layer, and the initial equilibrium angle between the conductive droplet and the insulating dielectric layer.

6. The method according to claim 4, characterized in that Also includes: The beam waist radius of the laser beam is determined based on the wavelength of the laser beam and the beam waist radius in the environment to be applied, the equivalent lens focal length and the equivalent lens refractive index of the device to be compensated in the environment to be applied, and the refractive index of the air in the test environment where the laser beam is located.

7. The method according to claim 6, characterized in that Based on the comparison between the second beam divergence angle and the expected beam divergence angle, determining the voltage fine-tuning parameter comprises: In response to a difference between the second beam spread angle and the desired beam spread angle being greater than a threshold deviation, a voltage trimming parameter that is not zero is determined.

8. The method according to claim 7, characterized in that The desired beam divergence angle is determined based on the beam waist radius of the laser beam in the application environment and the refractive index of the optical propagation medium in the application environment, and the equivalent lens focal length and the equivalent lens refractive index of the device to be compensated in the application environment.

9. The method according to claim 8, characterized in that The refractive index of the optical propagation medium in the environment to be used is determined based on the refractive index and the amount of refractive index variation of the environment to be used at a standard given temperature.

10. The method according to claim 9, characterized in that The refractive index variation is determined based on the wavelength of the laser beam, compensation coefficients under different media, a standard given temperature, and the temperature of the environment to be applied.

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