Device and method for measuring deflection angle of light beam

Abstract

The invention provides a light beam deflection angle measuring device and method. The device comprises a lens assembly and a four-quadrant detector. The lens assembly at least comprises a first conical lens and a convex lens, and the first conical lens is used for converting the parallel light beams into annular light beams and focusing the annular light beams subjected to angle deflection through the convex lens so as to form annular light spots on the four-quadrant detector; and the four-quadrant detector is used for determining the position offset of the annular light spot relative to the center of the four-quadrant detector according to the photoelectric value of each quadrant in the four-quadrant detector so as to determine the deflection angle of the annular light beam according to the position offset. According to the invention, the defect that the detection condition of a four-quadrant detector cannot be met and indirect measurement is needed due to the fact that a round light spot at the focus position is focused as a round point is overcome, and the effective measurement effect of a single detector is effectively improved.

Description

Technical Field

[0001] The present application relates to the field of measurement technology, and in particular to a device and method for measuring a light beam deflection angle. Background Art

[0002] The four-quadrant detector (4-QD) is a position-sensitive detector. Due to its many significant advantages such as simple signal processing, low inherent noise level, high sensitivity, and fast response speed, it has been widely used in various measurement fields, such as laser position sensors, autocollimators, optical tweezers, lidar, precise optical alignment, wavefront sensing, angle measurement, etc.

[0003] Taking acoustic field measurement as an example, based on the principle of acousto-optic deflection, 4-QD can be used to detect the tiny displacement of the light spot after the laser passes through the acoustic field, calculate the deflection angle of the light, and then use the compressed sensing tomography method to accurately measure the refractive index distribution of the acoustic field cross section.

[0004] However, the four-quadrant detector is limited by its own principles, which means that the light spot it detects must have a certain size. In the conventional measurement process, if the four-quadrant detector is at the focus, the value of the light spot radius will be extremely small, which makes it difficult to meet the measurement conditions of the four-quadrant detector. Therefore, it is often necessary to place multiple four-quadrant detectors at a certain distance before and after the focus for indirect measurement, so that the size of the light spot received by the four-quadrant detector meets the detection conditions. However, this makes data processing more complicated and the cost increases accordingly. Summary of the invention

[0005] Based on this, it is necessary to provide a device and method for measuring the light beam deflection angle in response to the above technical problems, aiming to solve the technical problems of complex data processing and increased cost when measuring the light deflection angle by the four-quadrant detector in the related technology.

[0006] In a first aspect, the present application provides a device for measuring a light beam deflection angle, comprising: a lens assembly and a four-quadrant detector; The lens assembly at least includes a first aconic lens and a convex lens, wherein the first aconic lens is used to convert a parallel light beam into an annular light beam, and the annular light beam after angle deflection is focused by the convex lens to form an annular light spot on the four-quadrant detector; The four-quadrant detector is used to determine the position offset of the annular light spot relative to the center of the four-quadrant detector according to the photoelectric values ​​of each quadrant in the four-quadrant detector, so as to determine the deflection angle of the annular light beam according to the position offset.

[0007] In one embodiment, a second aconic lens is further provided between the convex lens and the four-quadrant detector; The second conical lens is used to adjust the size of the annular light spot formed on the four-quadrant detector to adjust the detection performance of the four-quadrant detector, and the detection performance at least includes detection sensitivity and detection range.

[0008] In one embodiment, the device is used to measure the sound field distribution; A sound field area to be measured is arranged between the first conical lens and the convex lens, wherein the annular light beam produces an angular deflection after passing through the sound field area to be measured; the deflection angle of the light beam is also used to determine the refractive index distribution of the sound field cross section in the sound field area to be measured, so as to determine the sound field distribution of the sound field area to be measured.

[0009] In one embodiment, the four-quadrant detector is arranged at the focal plane of the convex lens. In a second aspect, the present application provides a method for measuring a light beam deflection angle, characterized in that the method is applied to a light beam deflection angle measuring device, wherein the light beam deflection angle measuring device comprises a lens assembly and a four-quadrant detector; the lens assembly comprises at least a first conical lens and a convex lens; The method comprises: The parallel light beam is transformed into an annular light beam by a first axicon; Focusing the annular light beam after angle deflection through a convex lens to form an annular light spot on a four-quadrant detector; The position offset of the annular light spot relative to the center of the four-quadrant detector is determined according to the photoelectric values ​​of each quadrant in the four-quadrant detector, so as to determine the deflection angle of the annular light beam according to the position offset.

[0010] In one embodiment, determining the position offset of the annular light spot relative to the center of the four-quadrant detector according to the photoelectric values ​​of each quadrant in the four-quadrant detector includes: Determining a normalized offset of the annular light spot relative to the center of the four-quadrant detector according to the photoelectric value of each quadrant in the four-quadrant detector; The position offset of the annular light spot relative to the center of the four-quadrant detector is determined based on the normalized offset of the center of the four-quadrant detector and a preset annular light spot intensity distribution model.

[0011] In one embodiment, determining the position offset of the annular light spot relative to the center of the four-quadrant detector based on the normalized offset of the center of the four-quadrant detector and a preset annular light spot intensity distribution model includes: Determining an estimated offset of the annular light spot relative to the center of the four-quadrant detector based on a normalized offset of the center of the four-quadrant detector and a radius of the annular light spot; Determine the functional relationship between the normalized offset and the position offset of the center of the four-quadrant detector based on a preset annular spot light intensity distribution model; The estimated offset is input into the functional relationship to update the estimated offset and obtain the position offset of the annular light spot relative to the center of the four-quadrant detector.

[0012] In one embodiment, the inputting the estimated offset into the functional relationship to update the estimated offset to obtain the position offset of the annular light spot relative to the center of the four-quadrant detector includes: Inputting the lateral offset in the estimated offset into the functional relationship to update the longitudinal offset in the estimated offset; Inputting the longitudinal offset in the estimated offset into the functional relationship to update the lateral offset in the estimated offset; Until the predicted normalized offset obtained by inputting the updated estimated offset into the functional relationship and the normalized offset detected by the four-quadrant detector meet the preset requirements, the currently obtained updated estimated offset is used as the position offset of the annular spot relative to the center of the four-quadrant detector.

[0013] In one embodiment, the calculation formula for determining the normalized offset of the annular light spot relative to the center of the four-quadrant detector according to the photoelectric value of each quadrant in the four-quadrant detector is as follows: ; in, is the normalized lateral offset of the annular spot relative to the center of the four-quadrant detector in the lateral direction, is the normalized longitudinal offset of the annular spot relative to the center of the four-quadrant detector in the longitudinal direction; are respectively the photoelectric values ​​of the four quadrants in the four-quadrant detector; The formula of the preset annular spot light intensity distribution model in polar coordinates is as follows: ; in, The polar diameter is r The light intensity at r0 is the radius of the ring, P is the total light intensity of the annular spot, where is the Dirac function; The functional relationship between the normalized offset and the position offset of the center of the four-quadrant detector is: ; ; Where d is the width of the annular spot, is the centroid coordinate of the annular spot, is the lateral position offset of the annular spot, is the lateral position offset of the annular spot; The calculation formula for the estimated offset of the annular spot relative to the center of the four-quadrant detector is: ; in, is the estimated offset of the annular spot relative to the center of the four-quadrant detector.

[0014] In one embodiment, the method is applied to the measurement of sound field distribution; The method further comprises: Allowing the annular light beam to pass through a sound field region to be measured so that the annular light beam is deflected; and Determining the refractive index distribution of the sound field cross section in the sound field region to be measured based on the deflection angle of the light beam; The sound field distribution of the sound field area to be measured is determined according to the refractive index distribution of the sound field cross section.

[0015] The device for measuring the deflection angle of a light beam provided in the embodiment of the present application converts light into a ring shape through a conical lens, and uses a convex lens to focus the ring beam to form a ring light spot. Combined with the analysis of the light intensity distribution of the ideal ring light spot and the imaging principle of the four-quadrant detector, the position offset of the ring light spot relative to the center of the four-quadrant detector is calculated to determine the deflection angle of the ring light beam. Compared with the conventional circular light spot, the device overcomes the defect that the circular light spot will be focused into a dot at the focal position, resulting in the inability to meet the detection conditions of the four-quadrant detector, thus requiring indirect measurement. That is, the present application provides a solution for implementing effective measurement using a single detector at the focal plane. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For those skilled in the art, other drawings can be obtained based on these drawings without creative work.

[0017] Figure 1a A schematic diagram of indirectly measuring the beam deflection angle based on a four-quadrant detector; Figure 1b is a schematic diagram of a circular light spot formed on a four-quadrant detector; Figure 2 A schematic diagram of the structure of a device for measuring a light beam deflection angle provided in an embodiment of the present application; Figure 3A schematic diagram of the structure of another device for measuring the light beam deflection angle provided in an embodiment of the present application; Figure 4 A schematic diagram of the structure of a system for realizing sound field measurement based on light beam deflection angle provided in an embodiment of the present application; Figure 5 A schematic flow chart of the steps of a method for measuring a light beam deflection angle provided in an embodiment of the present application; Figure 6 A schematic diagram of the structure of an electronic device provided in an embodiment of the present application. DETAILED DESCRIPTION

[0018] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of this application.

[0019] In the description of this application, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of this application, "plurality" means two or more, unless otherwise clearly and specifically defined.

[0020] In the description of the present application, the word "for example" is used to mean "used as an example, illustration or explanation". Any embodiment described as "for example" in the present application is not necessarily to be construed as being more preferred or advantageous than other embodiments. The following description is given to enable any technician in the field to implement and use the present invention. In the following description, details are listed for the purpose of explanation. It should be understood that a person of ordinary skill in the art can recognize that the present invention can be implemented without using these specific details. In other examples, well-known structures and processes will not be elaborated in detail to avoid obscuring the description of the present invention with unnecessary details. Therefore, the present invention is not intended to be limited to the embodiments shown, but is consistent with the widest scope consistent with the principles and features disclosed in the present application.

[0021] In order to facilitate understanding of the device and method for measuring the light beam deflection angle provided in the embodiments of the present application, the application background of the device and method for measuring the light beam deflection angle is first described accordingly. Specifically, the present application is mainly directed to a method for measuring the light beam deflection angle proposed for a four-quadrant detector. For example, as a common implementation scheme, a Gaussian beam laser (such as a helium-neon laser with a wavelength of 632nm) can be used to form a parallel light beam through a collimating lens, and the laser direction changes when passing through the measured area, and then the focusing lens is used to image the surface of the four-quadrant detector to form a circular light spot. By processing the electrical signal generated by the four-quadrant detector, the displacement information of the circular light spot can be obtained, thereby further obtaining the angle change value of the laser direction, that is, the deflection angle. The specific calculation formula is roughly as follows: ; in, f is the focal length of the convex lens, and is the lateral and longitudinal displacement of the light spot at the focus, and This corresponds to the deflection angle of the laser direction in the horizontal and vertical directions.

[0022] The four-quadrant detector is composed of four equivalent photodiodes separated by tiny gaps. When light hits the detector surface, the four quadrant units output photocurrents respectively, and the photocurrent amplitude of each unit is proportional to the light spot energy it receives. When the center of mass of the light spot is exactly at the center of the detector, the output photocurrent amplitudes of the four quadrants are equal; when the center of mass of the light spot deviates from the center, the photocurrent outputs of each quadrant lose balance. Based on this characteristic, the position of the center of mass of the light spot can be determined by the degree of imbalance of the photocurrent. However, due to the limitation of the principle of the four-quadrant detector, the light spot formed by irradiating the detector surface often needs to have a certain size. However, in the conventional measurement process, if the four-quadrant detector is at the focus, the value of the light spot radius will be extremely small, and only a dot will be formed, which makes it difficult to meet the measurement conditions of the four-quadrant detector. Therefore, in order to solve the above problem, the relevant technology proposes to place multiple four-quadrant detectors at a certain distance before and after the focus for indirect measurement. For details, please refer to Figure 1a , Figure 1a The figure is a schematic diagram of indirectly measuring the beam deflection angle based on a four-quadrant detector, which is described in detail as follows.

[0023] The laser source is divided into two beams by the first reflector (mirror 1) and the beamsplitter prism. The two parallel beams are imaged onto the surfaces of two four-quadrant detectors (4-QD a and 4-QD b) through convex lenses to form light spots. At this time, the angle measurement can be converted into the displacement of the light spot on the four-quadrant detector. The specific formula is as follows: ; in f is the focal length of the convex lens, and is the distance from the convex lens to the corresponding four-quadrant detector in the two optical paths, and are the lateral and longitudinal displacements of the light spot on the 4-QDa, and Corresponding to the lateral displacement and longitudinal displacement of the light spot on 4-QDb, and further combining the above formula with the above-mentioned deflection angle calculation formula, the calculation formula of the deflection angle in the above-mentioned indirect measurement process can be further obtained: ; The meaning of each parameter in the above formula has been provided above and will not be repeated here in the embodiments of the present application.

[0024] However, the above process needs to rely on the detection of multiple four-quadrant detectors, which on the one hand increases the cost of measurement. On the other hand, since it is necessary to calculate the displacement of the light spots on multiple four-quadrant detectors, it also increases the complexity of data processing, resulting in a relatively increased measurement error.

[0025] In addition, it is also necessary to point out that in the process of calculating the displacement of the light spot based on the photocurrent of the four-quadrant detector, since there is no direct mathematical relationship between the displacement of the light spot and the photocurrent, the displacement of the light spot determined by the photocurrent calculation is often a normalized displacement degree, and does not represent the displacement of the actual center of mass position of the light spot. It is often necessary to consider the mathematical model of the laser light spot energy distribution for further solution. For example, see Figure 1b , Figure 1b The schematic diagram of the circular light spot formed on the four-quadrant detector in the above solution is shown. Specifically, in order to facilitate the understanding of the above content, the following will be specifically explained in combination with the principle of the four-quadrant detector.

[0026] Specifically, under normal circumstances, the energy density distribution of the laser spot can be approximated by a Gaussian distribution, that is, ; in is the total energy of the Gaussian beam, is the radius of the light spot, ( x 0 , y 0 ) is the position of the centroid of the light spot, that is, the position of each spot on the four-quadrant detector The energy density distribution of the spot It can be described by the above formula.

[0027] On this basis, when light hits the detector surface, the four quadrant units output photocurrents respectively, and the photocurrent amplitude of each unit is It is proportional to the light spot energy it receives, that is: ; Among them, S i is the photosensitive area of ​​each quadrant unit.

[0028] Furthermore, the calculation formula of the normalized offset of the light spot relative to the center of the detector is as follows: ; Among them, (E X , E Y ) represents the normalized offset of the light spot relative to the center of the detector. Combined with the above description, it can be seen that the actual position of the center of mass ( x 0 , y 0 ) is not exactly the same as the calculated normalized offset (E X , E Y ), there is a nonlinear relationship between the two due to the Gaussian edge response, which usually manifests as an S-shaped nonlinear deviation. Therefore, in order to obtain the approximate position of the center of mass of the spot (x' 0 , y' 0 ) , a specific spot position correction algorithm is required for compensation. The energy density distribution of the spot and the shape of the detector are usually symmetrical, so the position calculations in the x-axis and y-axis directions are independent of each other. The subsequent analysis will mainly take the x-axis direction as an example. The details are as follows.

[0029] In a four-quadrant detector, the normalized relationship between the spot centroid position and the detector output current can be expressed by integration. Assuming the detector size is R and the gap width is d, according to the photocurrent distribution, the normalized lateral offset E X The calculation expression can be expressed as: ; This is a complex problem with transcendental equations that cannot be solved directly, so approximate methods or numerical calculations are needed to further optimize the analysis. Assuming that the detector size tends to infinity (R→∞) and the quadrant gap width tends to zero (d→0), the relationship between the spot centroid position and the normalized solution can be approximately expressed as: ; in, erf(x) is the error function, which is defined as follows: ; By inverting the error function of the above equation, the approximate position of the center of mass of the light spot can be obtained: ; Similarly, the longitudinal position of the center of mass can also be calculated through similar steps, which will not be repeated in this application.

[0030] It can be seen that in the relevant technical solutions, on the one hand, the light spot generated by direct measurement at the focus is difficult to meet the needs of the four-quadrant detector, and indirect measurement requires at least two detectors, which makes data processing more complicated and the cost increases accordingly. On the other hand, using Gaussian distribution as the light spot energy density distribution will cause nonlinearity due to the Gaussian edge response, which requires complex compensation and results in a smaller linear range.

[0031] In order to solve the above problems, the present application provides a device and method for measuring the deflection angle of a light beam, which converts the circular light spot detected by the detector into a circular light spot through a conical lens. On the one hand, it avoids the difficulty of the light spot at the focus to meet the requirements of the four-quadrant detector, so that the detection of the light spot displacement can be accurately and effectively realized using a single detector. On the other hand, it also provides another way to calculate the light spot displacement in combination with the light spot energy density distribution of the circular light spot, which effectively avoids the problem of edge response caused by the use of Gaussian distribution as the light spot energy density distribution of the circular light spot, and the need for complex compensation. The following will be explained in detail.

[0032] See also Figure 2 , Figure 2 A structural schematic diagram of a device for measuring a light beam deflection angle provided in an embodiment of the present application, wherein the device for measuring a light beam deflection angle mainly includes a lens assembly 210 and a four-quadrant detector 220, wherein the lens assembly 210 generally includes a first conical lens 2101 for converting a parallel light beam into an annular light beam, and a convex lens 2102 for focusing the annular light beam onto the four-quadrant detector.

[0033] The first conical lens 2101 is used to convert the parallel light beam into an annular light beam, and focus the annular light beam after angle deflection through the convex lens 2102 to form an annular light spot on the four-quadrant detector 220; The four-quadrant detector 220 is used to determine the position offset of the annular light spot relative to the center of the four-quadrant detector according to the photoelectric values ​​of each quadrant in the four-quadrant detector, so as to determine the deflection angle of the annular light beam according to the position offset.

[0034] Of course, it should be noted that the measuring device provided above is only a necessary component for realizing the method for measuring the beam deflection angle provided by the present application. In fact, in the application scenario of the measuring device provided by the embodiment of the present application, other more optional components may also be included. For example, a laser source for providing a laser beam may be included, wherein, based on the needs of the actual application scenario, the laser source may select a laser that emits a specific type of laser based on actual needs. In addition, other lenses may also be included, such as a reflector, a spectroscope, etc., for realizing the selection of more light paths. Of course, specific application components such as gratings, sound field generating devices, etc. may also be included. The embodiment of the present application does not limit other components that may be involved in the measuring device for the beam deflection angle in different application scenarios. All parallel beams are converted into annular beams through a conical lens, and the annular beam is focused on a four-quadrant detector through a convex lens to form an annular spot, so as to determine the position offset of the annular spot relative to the center of the four-quadrant detector according to the photoelectric values ​​of each quadrant in the four-quadrant detector, so as to calculate the deflection angle of the annular beam. All are within the scope of protection claimed in the present application.

[0035] On the basis of the above, in order to further improve the flexibility of the beam deflection angle measurement device provided by the present application in practical application scenarios. Figure 3 , Figure 3 This is a schematic diagram of the structure of another device for measuring the light beam deflection angle provided in an embodiment of the present application, which is described in detail as follows.

[0036] In the present application embodiment, Figure 2The difference from the schematic diagram of the structure of the device for measuring the deflection angle of the light beam shown in the figure is that a second cone lens 2103 is further provided between the convex lens 2102 and the four-quadrant detector 220, so that the size of the circular ring light spot formed on the four-quadrant detector can be easily changed by adjusting the distance between the second cone lens 2103 and the four-quadrant detector 220. Since the photoelectric value detected by the four-quadrant detector is related to the circular ring light spot formed on the four-quadrant detector, the second cone lens provided between the convex lens 2102 and the four-quadrant detector 220 can effectively adjust the angle detection range and sensitivity of the four-quadrant detector, so that it has more effective practical application value in specific application scenarios.

[0037] Of course, in order to clearly understand the specific application scenarios of the light beam deflection angle measurement device provided in this application, in a feasible embodiment, a specific light beam deflection angle measurement system will be provided to measure the deflection angle of the light beam after passing through the sound field, so as to further analyze and determine the implementation scheme of the sound field distribution. For details, please participate in Figure 4 , Figure 4 A schematic diagram of the system structure for realizing sound field measurement based on the light beam deflection angle provided in an embodiment of the present application is described in detail as follows.

[0038] In the embodiment of the present application, the parallel light beam emitted by the laser source becomes an annular light beam after passing through the first aconic lens, and is deflected after passing through the sound field, and is further processed by the convex lens and the second aconic lens before being focused on the four-quadrant detector to form an annular light spot. The formed annular light spot is also shown in the figure. It can be seen that the annular light spot is similar to the annular light spot of FIG. Figure 1a Compared with the indirect measurement of the beam deflection angle based on a four-quadrant detector shown in FIG, the method provided by the present application does not need to rely on the measurement of multiple beams and multiple four-quadrant detectors, which effectively reduces the measurement cost. Figure 1b Compared with the four-quadrant detector shown, the shape of the light spot focused thereon is also different, so there are certain differences in the light spot energy density distribution. The specific calculation process of the light spot displacement caused by the above differences will be specifically described in subsequent embodiments.

[0039] It can be seen that after determining the deflection angle of the light beam, the deflection angle can be further combined with the principle of acousto-optic deflection to determine the refractive index distribution of the sound field cross section in the sound field area to be measured using a compressed sensing tomography method, thereby further determining the sound field distribution of the sound field area to be measured. Of course, considering that this application is mainly for confirming the deflection angle of the light beam, the specific process of calculating the sound field distribution after obtaining the deflection angle of the light beam is not described in detail in the embodiments of this application.

[0040] In addition, in a feasible embodiment, the four-quadrant detector is arranged at the focal plane of the convex lens, so that the circular ring light spot formed in the four-quadrant detector has as small a width as possible, that is, the width Δr of the circular ring light spot is regarded as approaching 0, so as to facilitate subsequent calculations.

[0041] On the basis of the aforementioned device for measuring the light beam deflection angle, the embodiments of the present application will further illustrate the method for measuring the light beam deflection angle. In particular, after a circular spot is formed on the four-quadrant detector through a conical lens, a new and effective implementation scheme for accurately measuring the light beam deflection angle is provided in combination with the light spot energy density distribution of the circular spot, which will be specifically described below.

[0042] For details, please refer to Figure 5 , Figure 5 A schematic diagram of the step flow of a method for measuring a light beam deflection angle provided in an embodiment of the present application. In particular, the method for measuring a light beam deflection angle is mainly applied to the light beam deflection angle measuring device provided in any of the aforementioned embodiments. Specifically, the step flow of the measuring method is described in detail as follows, specifically including steps S510 to S530: S510, converting the parallel light beam into an annular light beam through a first axicon.

[0043] S520, focusing the annular light beam after angle deflection through a convex lens to form an annular light spot on a four-quadrant detector.

[0044] S530, determining a position offset of the annular light spot relative to the center of the four-quadrant detector according to the photoelectric values ​​of each quadrant in the four-quadrant detector, so as to determine a deflection angle of the annular light beam according to the position offset.

[0045] In the embodiments of the present application, the specific implementation process of converting a parallel light beam into an annular light beam by a first conical lens, and focusing the angle-deflected annular light beam by a convex lens to form an annular light spot on a four-quadrant detector is not described in detail. For details, please refer to the description of the aforementioned device for measuring the deflection angle of the aforementioned light beam.

[0046] In an embodiment of the present application, in the process of determining the position offset of the annular light spot relative to the center of the four-quadrant detector based on the photoelectric values ​​of each quadrant in the four-quadrant detector, and determining the deflection angle of the annular light beam according to the position offset, the process of determining the deflection angle of the annular light beam according to the position offset can be specifically referred to the above description, that is, the deflection angle of the annular light beam can be calculated according to the ratio of the position offset and the focal length of the convex lens, and the specific implementation scheme of the embodiment of the present application will not be repeated here. The embodiment of the present application mainly describes how to determine the position offset of the annular light spot relative to the center of the four-quadrant detector based on the photoelectric values ​​of each quadrant in the four-quadrant detector. In particular, in the above process, calculations will be performed based on the principle of the four-quadrant detector and the light intensity distribution of the annular light spot. Specifically, the details are as follows.

[0047] In an embodiment of the present application, in a feasible implementation scheme, the position offset of the annular light spot relative to the center of the four-quadrant detector is determined according to the photoelectric values ​​of each quadrant in the four-quadrant detector. Generally, the normalized offset of the annular light spot relative to the center of the four-quadrant detector can also be determined based on the photoelectric values ​​of each quadrant in the four-quadrant detector, so as to further determine the position offset of the annular light spot relative to the center of the four-quadrant detector based on the normalized offset and the distribution model of the light intensity of the annular light spot. That is to say, the position offset of the annular light spot relative to the center of the four-quadrant detector is determined according to the photoelectric values ​​of each quadrant in the four-quadrant detector, including: Determining a normalized offset of the annular light spot relative to the center of the four-quadrant detector according to the photoelectric value of each quadrant in the four-quadrant detector; The position offset of the annular light spot relative to the center of the four-quadrant detector is determined based on the normalized offset of the center of the four-quadrant detector and a preset annular light spot intensity distribution model.

[0048] The calculation process of the normalized offset of the center of the four-quadrant detector is usually similar to the above, that is, it is obtained by the following calculation formula: ; Among them, the explanation of each parameter has been explained in detail above, and the embodiments of the present application will not be repeated here.

[0049] On this basis, considering the light intensity distribution of the annular light spot, the embodiment of the present application further provides a position offset of the center of mass of the annular light spot relative to the center of the four-quadrant detector ( x 0 , y 0 ) and the normalized offset provided above The functional relationship between them will be explained in detail below.

[0050] Specifically, due to the focusing effect of the convex lens, the intensity distribution of the annular spot on the focal plane can be considered to be distributed entirely on the ring, and the width of the ring Δr→0, that is: ; Among them, r0 is the radius of the ring, that is, the radius of the annular spot, P is the total light intensity of the annular spot, where is the Dirac function, that is, it is not zero in the brackets, that is, , but the integral over the entire domain is 1.

[0051] In order to simplify the above formula and facilitate subsequent calculations, in the embodiment of the present application, the annular spot light intensity distribution is converted into a polar coordinate system, that is, a annular spot light intensity distribution model is constructed based on the polar coordinate system, thereby obtaining: ; That is to say, within the circular light spot, the light intensity distribution at each point in the light spot is mainly related to the polar coordinate value r of that point, that is, the polar diameter. Of course, the photocurrent amplitude output by the four quadrant units is proportional to the light spot energy they receive, that is: ; Among them, S i is the photosensitive area of ​​each quadrant unit.

[0052] By combining the above formulas, we can get the following formula: ; This formula actually describes, in the lateral direction, the normalized lateral offset Transverse coordinates to the centroid coordinates The functional relationship between them is is a sign function, when +1 when When is -1, is the polar angle in the polar coordinate system. And due to the Dirac function The existence of is non-zero, so the above formula can be simplified to: ; By analyzing the symbolic function, we can further obtain the following formula: ; It can be seen that the above scheme describes the ideal situation, that is, the intensity distribution of the annular spot on the focal plane is concentrated in the width of the ring. When on the ring, the normalized lateral offset Transverse coordinates to the centroid coordinates Therefore, this value can be used as a rough solution of the position offset of the annular spot relative to the center of the four-quadrant detector for subsequent calculations.

[0053] Of course, the above process is described with reference to the horizontal direction as an example. In fact, the position offset in the vertical direction can also be calculated based on a similar process as above. y 0 Normalized longitudinal offset The ideal functional relationship between them is obtained, so as to obtain a rough solution of the position offset in the longitudinal direction for subsequent calculations.

[0054] Of course, the above process only considers that the intensity distribution of the annular spot is concentrated in the width of the ring. When it is on the ring, the width of the ring , that is, only considering But in fact, the ring of the annular spot also has a certain ring width, that is, based on the photocurrent distribution provided above, the normalized lateral offset E X The actual calculation formula is as follows: ; Wherein, the detector size is R, and the ring width is d. At this time, combined with the annular spot light intensity distribution model in the polar coordinate system provided above, the functional relationship between the normalized offset and the position offset of the center of the four-quadrant detector can be further determined, including the normalized lateral offset Transverse coordinates to the centroid coordinates , that is, the functional relationship between the values ​​of the position offset in the horizontal dimension: ; Based on a similar process, the normalized longitudinal offset can be further obtained: Longitudinal coordinates with centroid coordinates , that is, the specific functional relationship between the values ​​of the position offset in the horizontal dimension: ; That is, after determining the normalized offset of the annular light spot relative to the center of the four-quadrant detector based on the photoelectric values ​​of each quadrant in the four-quadrant detector, the position offset of the center of mass of the annular light spot relative to the center of the four-quadrant detector can be obtained by solving the above equation ( x 0 , y 0 ).

[0055] Of course, considering that the above equation is difficult to solve directly, in order to simplify the above calculation process, as a feasible embodiment of the present application, an implementation scheme based on iterative update calculation of a rough solution to obtain an accurate position offset is provided. That is to say, in an embodiment of the present application, the position offset of the annular light spot relative to the center of the four-quadrant detector is determined based on the normalized offset of the center of the four-quadrant detector and the preset annular light spot intensity distribution model, including: Determining an estimated offset of the annular light spot relative to the center of the four-quadrant detector based on a normalized offset of the center of the four-quadrant detector and a radius of the annular light spot; Determine the functional relationship between the normalized offset and the position offset of the center of the four-quadrant detector based on a preset annular spot light intensity distribution model; The estimated offset is input into the functional relationship to update the estimated offset and obtain the position offset of the annular light spot relative to the center of the four-quadrant detector.

[0056] The calculation process of determining the estimated offset of the annular light spot relative to the center of the four-quadrant detector based on the normalized offset of the center of the four-quadrant detector and the radius of the annular light spot can refer to the above formula: ; The normalized offset of the center of the four-quadrant detector and the radius of the annular spot are also obtained. (As ) is substituted into the equation, we can get the estimated offset of the annular spot relative to the center of the four-quadrant detector, which is the rough solution .

[0057] On the basis of the above, by Substituting into the specific formula of the functional relationship provided above, the update of the centroid coordinates can be completed, wherein the specific update of the centroid coordinates can be to update the longitudinal coordinates through the rough solution of the transverse coordinates, and to update the transverse coordinates based on the rough solution of the longitudinal coordinates, that is, the estimated offset is input into the functional relationship to update the estimated offset, and the position offset of the annular light spot relative to the center of the four-quadrant detector is obtained, including: Inputting the lateral offset in the estimated offset into the functional relationship to update the longitudinal offset in the estimated offset; Inputting the longitudinal offset in the estimated offset into the functional relationship to update the lateral offset in the estimated offset; Until the predicted normalized offset obtained by inputting the updated estimated offset into the functional relationship and the normalized offset detected by the four-quadrant detector meet the preset requirements, the currently obtained updated estimated offset is used as the position offset of the annular spot relative to the center of the four-quadrant detector.

[0058] Specifically, the rough solution Substituting the normalized offset and centroid coordinates into the specific formula provided above, the updated estimated offset is calculated as follows: ; ; That is, the rough solution, that is, the lateral offset in the estimated offset Substituting the above normalized longitudinal offset The calculation formula can be used to obtain the updated longitudinal offset. Similarly, the longitudinal offset in the estimated offset is Substituting the above normalized lateral offset The updated lateral offset can be obtained by using the calculation formula.

[0059] By cyclically substituting the lateral offset and the longitudinal offset in the updated estimated offset into the calculation formula of the above-mentioned normalized offset, the updated offset can be gradually approached to the actual result. That is to say, when the predicted normalized offset obtained by inputting the updated estimated offset into the preset annular spot light intensity distribution model at a certain time and the difference between the normalized offset detected by the four-quadrant detector does not exceed the preset threshold, it can be considered that the currently obtained estimated offset is closer to the actual offset. Therefore, the currently obtained updated estimated offset can be used as the position offset of the annular spot relative to the center of the four-quadrant detector for subsequent calculations, such as for the calculation of the sound field distribution, that is, after determining the deflection angle of the light beam based on the position offset of the annular spot relative to the center of the four-quadrant detector, the refractive index distribution of the sound field cross section in the sound field area to be measured is determined based on the deflection angle, so as to further determine the sound field distribution of the sound field area to be measured according to the refractive index distribution of the sound field cross section. The calculation process of the subsequent sound field distribution is not elaborated in the embodiment of the present application.

[0060] It can be seen that the device and method for measuring the beam deflection angle provided in the embodiment of the present application converts the light into a ring shape through a conical lens, and uses a convex lens to focus the ring beam to form a ring light spot, which solves the defect in the related art that the circular light spot at the focal position will be focused into a dot, resulting in the inability to meet the detection conditions of the four-quadrant detector, thereby requiring indirect measurement, effectively reducing the measurement cost and achieving effective detection by a single detector. At the same time, combined with the analysis of the intensity distribution of the circular light spot formed and the imaging principle of the four-quadrant detector, a specific solution is provided for calculating the displacement of the circular light spot based on the photocurrent on the four quadrants detected by the four-quadrant detector to accurately calculate the beam deflection angle. At the same time, compared with the spot energy distribution of the Gaussian distribution used on the circular light spot, the defect of the nonlinear relationship between the actual position of the center of mass and the normalized offset caused by the Gaussian edge response is overcome, thereby requiring complex compensation of the normalized offset to obtain the actual position of the center of mass. The measurement method provided in the present application iteratively updates the estimated offset by cyclically substituting the rough solution obtained by simplified calculation into the annular spot light intensity distribution model, so that the updated estimated offset gradually approaches the actual offset result, thereby being able to accurately and effectively obtain the position offset of the annular spot relative to the center of the four-quadrant detector, and accurately calculate the deflection angle of the annular light beam, which can be further used in subsequent calculations, such as the calculation of the sound field distribution through which the annular light beam passes.

[0061] Of course, in order to realize the above-mentioned measurement process of the beam deflection angle, in addition to the lens assembly and the four-quadrant detector mentioned in the beam deflection angle measurement device, in a feasible implementation scheme, an electronic device is also provided, and the electronic device is electrically connected to the four-quadrant detector to collect the photoelectric values ​​of each quadrant in the four-quadrant detector, so as to complete the calculation of the position offset of the annular light spot relative to the center of the four-quadrant detector and the deflection angle of the annular light beam based on the calculation process of the beam deflection angle measurement method provided in the present application. For example, in one embodiment, the memory of the electronic device may store program modules for executing the various steps in the above-mentioned embodiments, and the computer program composed of the various program modules enables the electronic device to execute the steps in the beam deflection angle measurement method of each embodiment of the present application described in this specification.

[0062] For example, see Figure 6 , Figure 6A schematic diagram of the structure of an electronic device provided in an embodiment of the present application. The electronic device includes a processor, a memory and a network interface connected via a system bus. The processor of the electronic device is used to provide computing and control capabilities. The memory of the electronic device includes a non-volatile storage medium and an internal memory. The non-volatile storage medium stores an operating system and a computer program. The internal memory provides an environment for the operation of the operating system and the computer program in the non-volatile storage medium. The network interface of the electronic device is used to communicate with an external electronic device via a network connection. When the computer program is executed by the processor, a method for measuring a beam deflection angle is implemented.

[0063] Those skilled in the art will understand that Figure 6 The structure shown in the figure is merely a block diagram of a partial structure related to the scheme of the present application, and does not constitute a limitation on the electronic device to which the scheme of the present application is applied. The specific electronic device may include more or fewer components than shown in the figure, or combine certain components, or have a different arrangement of components.

[0064] In some embodiments of the present application, a computer-readable storage medium is provided, storing a computer program, and the computer program is loaded by a processor, so that the processor executes any method for measuring a light beam deflection angle provided in the embodiments of the present application.

[0065] Those of ordinary skill in the art can understand that all or part of the processes in the above-mentioned embodiment methods can be completed by instructing the relevant hardware through a computer program, and the computer program can be stored in a non-volatile computer-readable storage medium. When the computer program is executed, it can include the processes of the embodiments of the above-mentioned methods. Any reference to memory, storage, information library or other media used in the embodiments provided in this application may include at least one of non-volatile and volatile memory. Non-volatile memory may include read-only memory (ROM), magnetic tape, floppy disk, flash memory or optical memory, etc. Volatile memory may include random access memory (RAM) or external cache memory. As an illustration and not limitation, RAM can be in various forms, such as static random access memory (SRAM) or dynamic random access memory (DRAM).

[0066] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0067] The above is a detailed introduction to a device and method for measuring the deflection angle of a light beam provided in an embodiment of the present application. Specific examples are used herein to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea; at the same time, for technical personnel in this field, according to the idea of ​​the present invention, there will be changes in the specific implementation method and application scope. In summary, the content of this specification should not be understood as a limitation on the present invention.

Claims

1. A device for measuring a light beam deflection angle, characterized in that: include: lens assembly and four-quadrant detector; The lens assembly at least includes a first aconic lens and a convex lens, wherein the first aconic lens is used to convert a parallel light beam into an annular light beam, and the annular light beam after angle deflection is focused by the convex lens to form an annular light spot on the four-quadrant detector; The four-quadrant detector is used to determine the position offset of the annular light spot relative to the center of the four-quadrant detector according to the photoelectric values ​​of each quadrant in the four-quadrant detector, so as to determine the deflection angle of the annular light beam according to the position offset.

2. The device according to claim 1, characterized in that A second aconic lens is also provided between the convex lens and the four-quadrant detector; The second conical lens is used to adjust the size of the annular light spot formed on the four-quadrant detector to adjust the detection performance of the four-quadrant detector, and the detection performance at least includes detection sensitivity and detection range.

3. The device according to claim 1, characterized in that The device is applied to measure the sound field distribution; A sound field area to be measured is arranged between the first conical lens and the convex lens, wherein the annular light beam produces an angular deflection after passing through the sound field area to be measured; the deflection angle of the light beam is also used to determine the refractive index distribution of the sound field cross section in the sound field area to be measured, so as to determine the sound field distribution of the sound field area to be measured.

4. The device according to any one of claims 1 to 3, characterized in that: The four-quadrant detector is arranged on the focal plane of the convex lens.

5. A method for measuring a light beam deflection angle, characterized in that: Applicable to a device for measuring a light beam deflection angle, the device comprising a lens assembly and a four-quadrant detector; the lens assembly at least comprises a first cone lens and a convex lens; The method comprises: The parallel light beam is transformed into an annular light beam by a first axicon; Focusing the annular light beam after angle deflection through a convex lens to form an annular light spot on a four-quadrant detector; The position offset of the annular light spot relative to the center of the four-quadrant detector is determined according to the photoelectric values ​​of each quadrant in the four-quadrant detector, so as to determine the deflection angle of the annular light beam according to the position offset.

6. The method according to claim 5, characterized in that Determining the position offset of the annular light spot relative to the center of the four-quadrant detector according to the photoelectric values ​​of each quadrant in the four-quadrant detector includes: Determining a normalized offset of the annular light spot relative to the center of the four-quadrant detector according to the photoelectric value of each quadrant in the four-quadrant detector; The position offset of the annular light spot relative to the center of the four-quadrant detector is determined based on the normalized offset of the center of the four-quadrant detector and a preset annular light spot light intensity distribution model.

7. The method according to claim 6, characterized in that The determining the position offset of the annular light spot relative to the center of the four-quadrant detector based on the normalized offset of the center of the four-quadrant detector and a preset annular light spot intensity distribution model includes: Determining an estimated offset of the annular light spot relative to the center of the four-quadrant detector based on a normalized offset of the center of the four-quadrant detector and a radius of the annular light spot; Determine the functional relationship between the normalized offset and the position offset of the center of the four-quadrant detector based on a preset annular spot light intensity distribution model; The estimated offset is input into the functional relationship to update the estimated offset and obtain the position offset of the annular light spot relative to the center of the four-quadrant detector.

8. The method according to claim 7, characterized in that Inputting the estimated offset into the functional relationship to update the estimated offset to obtain the position offset of the annular light spot relative to the center of the four-quadrant detector includes: Inputting the lateral offset in the estimated offset into the functional relationship to update the longitudinal offset in the estimated offset; Inputting the longitudinal offset in the estimated offset into the functional relationship to update the lateral offset in the estimated offset; Until the predicted normalized offset obtained by inputting the updated estimated offset into the functional relationship and the normalized offset detected by the four-quadrant detector meet the preset requirements, the currently obtained updated estimated offset is used as the position offset of the annular spot relative to the center of the four-quadrant detector.

9. The method according to claim 7, characterized in that: The calculation formula for determining the normalized offset of the annular light spot relative to the center of the four-quadrant detector according to the photoelectric values ​​of each quadrant in the four-quadrant detector is as follows: ； in, is the normalized lateral offset of the annular spot relative to the center of the four-quadrant detector in the lateral direction, is the normalized longitudinal offset of the annular spot relative to the center of the four-quadrant detector in the longitudinal direction; are respectively the photoelectric values ​​of the four quadrants in the four-quadrant detector; The formula of the preset annular spot light intensity distribution model in polar coordinates is as follows: ； in, The polar diameter is r The light intensity at is the radius of the ring, P is the total light intensity of the annular spot, where is the Dirac function; The functional relationship between the normalized offset and the position offset of the center of the four-quadrant detector is: ； ； Where, d is the width of the annular spot, ( x 0 ，y 0 ) is the centroid coordinate of the annular spot, x 0 is the lateral position offset of the annular spot, y 0 is the lateral position offset of the annular spot; The calculation formula for the estimated offset of the annular spot relative to the center of the four-quadrant detector is: ； in, is the estimated offset of the annular spot relative to the center of the four-quadrant detector.

10. The method according to any one of claims 5 to 9, characterized in that: The method is applied to the measurement of sound field distribution; The method further comprises: Allowing the annular light beam to pass through a sound field region to be measured so that the annular light beam is deflected; and Determining the refractive index distribution of the sound field cross section in the sound field region to be measured based on the deflection angle of the light beam; The sound field distribution of the sound field area to be measured is determined according to the refractive index distribution of the sound field cross section.

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