Measuring Device and Method for Beam Deflection Angle

Abstract

The present application provides a device and a method for measuring the deflection angle of a light beam. The device includes: a lens assembly and a quadrant detector; the lens assembly at least includes a first conical lens and a convex lens. The first conical lens is used to convert a parallel light beam into an annular light beam, and the deflected annular light beam is focused through the convex lens to form an annular light spot on the quadrant detector; the quadrant detector is used to determine the position offset of the annular light spot relative to the center of the quadrant detector according to the photoelectric values of each quadrant in the quadrant detector, so as to determine the deflection angle of the annular light beam according to the position offset. The present application 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 quadrant detector, so indirect measurement is required, and effectively improves the effect of effective measurement by a single detector.

Description

Technical Field

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

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

[0003] Taking acoustic field measurement as an example, based on the acousto-optic deflection principle, the small displacement of the light spot after the laser passes through the acoustic field can be detected by a 4-QD, and the deflection angle of the light can be calculated, so as to perform precise measurement of the refractive index distribution of the cross-section of the acoustic field by using the tomographic method of compressive sensing.

[0004] However, limited by its own principle, the light spot detected by the quadrant detector must have a certain size. In the conventional measurement process, if the quadrant detector is at the focal point, the value of the light spot radius will be extremely small, which is difficult to meet the measurement conditions of the quadrant detector. Therefore, multiple quadrant detectors often need to be placed at a certain distance before and after the focal point for indirect measurement, so that the size of the light spot received by the quadrant detector meets the detection conditions, but this makes the data processing more complex and the cost also increases accordingly. Summary of the Invention

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

[0006] In a first aspect, the present application provides a device for measuring the deflection angle of a light beam, including: a lens assembly and a quadrant detector;

[0007] The lens assembly at least includes a first conical lens and a convex lens. The first conical lens is used to convert a parallel light beam into an annular light beam, and the deflected annular light beam is focused by the convex lens to form an annular light spot on the quadrant detector;

[0008] The quadrant detector is used to determine the position offset of the annular light spot relative to the center of the quadrant detector according to the photoelectric values of each quadrant in the quadrant detector, so as to determine the deflection angle of the annular light beam according to the position offset.

[0009] In one embodiment, a second conical lens is further provided between the convex lens and the quadrant detector;

[0010] The second conical lens is used to adjust the size of the annular light spot formed on the quadrant detector, so as to adjust the detection performance of the quadrant detector, and the detection performance at least includes detection sensitivity and detection range.

[0011] In one embodiment, the device is applied to the measurement of sound field distribution;

[0012] A sound field area to be measured is arranged between the first conical lens and the convex lens. Wherein, the annular light beam generates 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.

[0013] In one embodiment, the quadrant detector is arranged on the focal plane of the convex lens.

[0014] In a second aspect, the present application provides a method for measuring the deflection angle of a light beam, which is characterized in that it is applied to a device for measuring the deflection angle of a light beam, and the device for measuring the deflection angle of a light beam includes a lens assembly and a quadrant detector; the lens assembly at least includes a first conical lens and a convex lens;

[0015] The method includes:

[0016] Converting a parallel light beam into an annular light beam through a first conical lens;

[0017] Focusing the annular light beam with an angular deflection through a convex lens to form an annular light spot on the quadrant detector;

[0018] According to the photoelectric values of each quadrant in the quadrant detector, determine the position offset of the annular light spot relative to the center of the quadrant detector, so as to determine the deflection angle of the annular light beam according to the position offset.

[0019] In one embodiment, the determining the position offset of the annular light spot relative to the center of the quadrant detector according to the photoelectric values of each quadrant in the quadrant detector includes:

[0020] Determine the normalized offset of the annular light spot relative to the center of the quadrant detector according to the photoelectric values of each quadrant in the quadrant detector;

[0021] Based on the normalized offset of the center of the quadrant detector and a preset light intensity distribution model of the annular light spot, determine the position offset of the annular light spot relative to the center of the quadrant detector.

[0022] In one embodiment, determining the position offset of the annular light spot relative to the center of the quadrant detector based on the normalized offset of the center of the quadrant detector and a preset annular light spot intensity distribution model includes:

[0023] Based on the normalized offset of the center of the quadrant detector and the radius of the annular light spot, determining the estimated offset of the annular light spot relative to the center of the quadrant detector;

[0024] Based on the preset annular light spot intensity distribution model, determining the functional relationship between the normalized offset of the center of the quadrant detector and the position offset;

[0025] Inputting the estimated offset into the functional relationship to update the estimated offset, and obtaining the position offset of the annular light spot relative to the center of the quadrant detector.

[0026] In one embodiment, inputting the estimated offset into the functional relationship to update the estimated offset and obtaining the position offset of the annular light spot relative to the center of the quadrant detector includes:

[0027] Inputting the lateral offset in the estimated offset into the functional relationship to update the longitudinal offset in the estimated offset;

[0028] Inputting the longitudinal offset in the estimated offset into the functional relationship to update the lateral offset in the estimated offset;

[0029] Until the predicted normalized offset obtained by inputting the updated estimated offset into the functional relationship satisfies the preset requirements, taking the currently obtained updated estimated offset as the position offset of the annular light spot relative to the center of the quadrant detector.

[0030] In one embodiment, the calculation formula for determining the normalized offset of the annular light spot relative to the center of the quadrant detector according to the optoelectronic values of each quadrant in the quadrant detector is as follows:

[0031] ;

[0032] Wherein, is the normalized lateral offset of the annular light spot relative to the center of the quadrant detector in the lateral direction, is the normalized longitudinal offset of the annular light spot relative to the center of the quadrant detector in the longitudinal direction; are respectively the optoelectronic values of the four quadrants in the quadrant detector;

[0033] The formula of the preset annular light spot intensity distribution model in polar coordinates is as follows:

[0034] ;

[0035] where, is the light intensity at the polar radius r , r0 is the radius of the ring, P is the total light intensity of the annular light spot, where is the Dirac function;

[0036] The functional relationship between the normalized offset at the center of the quadrant detector and the position offset is:

[0037] ;

[0038] ;

[0039] where, d is the width of the annular light spot, is the centroid coordinate of the annular light spot, is the lateral position offset of the annular light spot, is the lateral position offset of the annular light spot;

[0040] The calculation formula for the estimated offset of the annular light spot relative to the center of the quadrant detector is:

[0041] ;

[0042] where, is the estimated offset of the annular light spot relative to the center of the quadrant detector.

[0043] In one embodiment, the method is applied to the measurement of the sound field distribution;

[0044] The method further includes:

[0045] Passing the annular beam through the sound field area to be measured to cause deflection of the annular beam; and

[0046] Determining the refractive index distribution of the sound field cross-section in the sound field area to be measured based on the deflection angle of the beam;

[0047] Determining the sound field distribution of the sound field area to be measured according to the refractive index distribution of the sound field cross-section.

[0048] The beam deflection angle measuring device provided by the embodiment of the present application converts light into a ring through a cone lens, and uses a convex lens to focus the ring beam to form a ring-shaped light spot. By combining the analysis of the light intensity distribution of the ideal circular ring light spot and the imaging principle of the quadrant detector, the calculation of the position offset of the ring-shaped light spot relative to the center of the quadrant detector is realized to determine the deflection angle of the ring beam. Compared with the conventional circular light spot, it 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 quadrant detector, so indirect measurement is required. That is, the present application provides an implementation scheme for effective measurement using a single detector at the focal plane. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the following drawings are only some embodiments of the present application. For those skilled in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0050] Figure 1a Schematic diagram for indirectly measuring the beam deflection angle based on a quadrant detector;

[0051] Figure 1b Schematic diagram of a circular light spot formed on a quadrant detector;

[0052] Figure 2 Schematic structural diagram of a beam deflection angle measuring device provided by the embodiment of the present application;

[0053] Figure 3 Schematic structural diagram of another beam deflection angle measuring device provided in the embodiment of the present application;

[0054] Figure 4 Schematic structural diagram of a system for measuring the sound field based on the beam deflection angle provided by the embodiment of the present application;

[0055] Figure 5 Schematic diagram of the step flow of a beam deflection angle measuring method provided by the embodiment of the present application;

[0056] Figure 6 Schematic structural diagram of an electronic device provided by the embodiment of the present application. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0057] The following will clearly and completely describe the technical solutions in the embodiments of the present application in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative efforts fall within the scope of protection of the present application.

[0058] In the description of the present application, the terms "first" and "second" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of the described features. In the description of the present application, the meaning of "a plurality" is two or more, unless otherwise specifically defined.

[0059] In the description of the present application, the term "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 construed as being more preferred or having more advantages than other embodiments. In order for any person skilled in the art to implement and use the present invention, the following description is given. In the following description, details are set forth for the purpose of explanation. It should be understood that those of ordinary skill in the art can recognize that the present invention can be implemented without using these specific details. In other instances, well-known structures and processes are not elaborated in detail to avoid unnecessary details from obscuring the description of the present invention. Therefore, the present invention is not intended to be limited to the embodiments shown, but is consistent with the broadest scope that conforms to the principles and features disclosed in the present application.

[0060] To facilitate the understanding of the beam deflection angle measurement device and method provided in the embodiments of the present application, the application background of the related beam deflection angle measurement device and method will be described accordingly. Specifically, the present application mainly proposes a beam deflection angle measurement method for a quadrant detector. For example, as a common implementation scheme, a Gaussian beam laser (such as a helium-neon laser with a wavelength of 632 nm) can be used to form a parallel beam through a collimating lens, and the laser direction changes when passing through the measured area, and then it is imaged onto the surface of the quadrant detector through a focusing lens to form a circular spot. By processing the electrical signals generated by the quadrant detector, the displacement information of the circular spot can be obtained, and further the angle change value of the laser direction, that is, the deflection angle, can be obtained. The specific calculation formula is roughly as follows:

[0061] ;

[0062] wherein, f is the focal length of the convex lens, and are the lateral displacement and longitudinal displacement of the light spot at the focus, and correspond to the deflection angles of the laser direction in the lateral and longitudinal directions, respectively.

[0063] The quadrant detector is composed of four equivalent photodiodes, which are separated by a small gap. When light irradiates the detector surface, the four quadrant units respectively output photocurrents, and the magnitude of the photocurrent of each unit is proportional to the spot energy it receives. When the centroid of the light spot is exactly at the center of the detector, the output photocurrent magnitudes of the four quadrants are equal; when the centroid of the light spot deviates from the center, the photocurrent outputs of each quadrant are unbalanced. Based on this characteristic, the position of the light spot centroid can be determined by the degree of imbalance of the photocurrents. However, due to the principle of the quadrant detector, the light spot formed on the detector surface usually needs to have a certain size. However, in the conventional measurement process, if the quadrant detector is at the focus, the value of the spot radius will be extremely small, only forming a dot, making it difficult to meet the measurement conditions of the quadrant detector. Therefore, to solve the above problems, the related technology proposes to place multiple quadrant detectors at a certain distance before and after the focus for indirect measurement. Specifically, please refer to Figure 1a , Figure 1a which is a schematic diagram of indirect measurement of the beam deflection angle based on a quadrant detector, and is described in detail as follows.

[0064] Among them, the laser source is divided into two beams successively through the first mirror and the beamsplitter prism. The two parallel beams are imaged onto the surfaces of two 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 spots on the quadrant detectors. The specific formula is as follows:

[0065] ;

[0066] where f is the focal length of the convex lens, and are the distances from the convex lens to the corresponding quadrant detectors in the two optical paths, and are the lateral displacement and longitudinal displacement of the light spot on 4-QDa, and correspond to the lateral displacement and longitudinal displacement of the light spot on 4-QDb. Further combining the above formula with the deflection angle calculation formula provided above, the deflection angle calculation formula in the above indirect measurement process can be further obtained:

[0067] ;

[0068] Among them, the meanings of the parameters in the above formula have been provided previously, and the embodiments of the present application will not repeat them here.

[0069] However, the above process requires the detection of multiple quadrant detectors. On the one hand, it increases the measurement cost. On the other hand, since it is necessary to calculate the displacements of the light spots on multiple quadrant detectors, it also increases the complexity of data processing, resulting in a relatively increased measurement error.

[0070] In addition, it should also be noted that in the process of calculating the displacement of the light spot based on the photocurrent of the 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 based on the photocurrent calculation is often the normalized offset degree, rather than representing the offset of the actual centroid position of the light spot. It is often necessary to consider the mathematical model of the energy distribution of the laser light spot for further solution. For example, please refer to Figure 1b , Figure 1b shows a schematic diagram of the circular light spot formed on the quadrant detector in the above scheme. Specifically, for the convenience of understanding the above content, the following will specifically describe it in combination with the principle of the quadrant detector.

[0071] Specifically, usually, the energy density distribution of the laser light spot can be approximated by a Gaussian distribution, that is

[0072] ;

[0073] Among them 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 energy density distribution of each [[[]] on the quadrant detector [[[]] can be described by the above formula.

[0074] On this basis, when light irradiates the surface of the detector, the four quadrant units respectively output photocurrents, and the photocurrent amplitude [[[]] of each unit is proportional to the light spot energy it receives, that is:

[0075] ;

[0076] Among them, S[[[]] i is the photosensitive area of each quadrant unit.

[0077] Furthermore, the calculation formula for the normalized offset of the light spot relative to the center of the detector is specifically as follows:

[0078] ;

[0079] Among them, (E X , E Y ) represents the normalized offset degree of the light spot relative to the center of the detector. And from the foregoing relevant descriptions, it can be known that. The actual position of the centroid ( x 0 , y 0 ) is not exactly the same as the calculated normalized offset degree (E X , E Y ), and there is a non-linear relationship between the two due to the Gaussian edge response, which usually shows an S-shaped non-linear deviation. Therefore, in order to obtain the approximate position of the light spot centroid (x' 0 , y' 0 ) , it is necessary to use a specific light spot position correction algorithm for compensation. Among them, the energy density distribution of the light spot and the shape of the detector are usually symmetric, 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 for discussion. Specifically as follows.

[0080] In a quadrant detector, the normalized relationship between the light 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 calculation expression of the normalized lateral offset E X can be expressed as:

[0081] ;

[0082] This is a complex problem with a transcendental equation and cannot be directly solved. Therefore, it is necessary to use approximation methods or numerical calculations to further optimize the analysis. In the case of assuming that the detector size tends to infinity (R→∞) and the quadrant gap width tends to zero (d→0), the relationship between the light spot centroid position and the normalized solution value can be approximately expressed as:

[0083] ;

[0084] Among them, erf(x) is the error function, and the definition is as follows:

[0085] ;

[0086] By taking the inverse error function of the above equation, the approximate position of the light spot centroid can be obtained:

[0087] ;

[0088] Similarly, the longitudinal position of the centroid can also be calculated through similar steps, and the present application will not repeat the description.

[0089] It can be seen that in the related technical solutions, on the one hand, the spot directly measured at the focus is difficult to meet the requirements of the quadrant detector. Indirect measurement requires at least two detectors, the data processing is more complex, and the cost also increases accordingly. On the other hand, using the Gaussian distribution as the spot energy density distribution will cause non-linearity due to the Gaussian edge response, and complex compensation is required, resulting in a smaller linear range.

[0090] To solve the above problems, the present application provides a device and method for measuring the beam deflection angle. The circular spot detected by the detector is converted into an annular spot through a conical lens. On the one hand, it avoids the problem that the spot at the focus is difficult to meet the requirements of the quadrant detector, so that the displacement of the spot can be accurately and effectively detected by using a single detector. On the other hand, it also provides another way to calculate the spot displacement in combination with the spot energy density distribution of the annular spot, effectively avoiding the problem of edge response caused by using the Gaussian distribution as the spot energy density distribution of the circular spot and the need for complex compensation. The following will be specifically described.

[0091] Please refer to Figure 2 , Figure 2 , which is a schematic structural diagram of a device for measuring the beam deflection angle provided by an embodiment of the present application. The device for measuring the beam deflection angle mainly includes a lens assembly 210 and a quadrant detector 220. The lens assembly 210 generally includes a first conical lens 2101 for converting a parallel beam into an annular beam, and a convex lens 2102 for focusing the annular beam on the quadrant detector.

[0092] Among them, the first conical lens 2101 is used to convert a parallel beam into an annular beam, and the deflected annular beam is focused by the convex lens 2102 to form an annular spot on the quadrant detector 220;

[0093] The quadrant detector 220 is used to determine the position offset of the annular spot relative to the center of the quadrant detector according to the photoelectric values of each quadrant in the quadrant detector, so as to determine the deflection angle of the annular beam according to the position offset.

[0094] Of course, it should be noted that the above-provided measuring device is merely an essential component for implementing the method for measuring the deflection angle of the light beam provided in this application. In fact, in the application scenario of the measuring device provided in the embodiments of this application, there may also be included many other optional components. For example, a laser source for providing a laser beam may be included. Among them, based on the requirements of the actual application scenario, the laser source may select a laser that emits a specific type of laser according to actual needs. In addition, other lenses may also be included, such as mirrors, beam splitters, etc., for implementing the selection of more optical paths. Of course, specific application components such as gratings, acoustic field generating devices, etc. may also be included. The embodiments of this application do not limit other components that may be involved in the measuring device for the deflection angle of the light beam in different application scenarios. Any device that converts a parallel light beam into an annular light beam through a cone lens and focuses the annular light beam on a quadrant detector through a convex lens to form an annular light spot, and determines the position offset of the annular light spot relative to the center of the quadrant detector according to the photoelectric values in each quadrant of the quadrant detector to calculate the deflection angle of the annular light beam is within the scope protected by this application.

[0095] On the basis of the above, in order to further improve the flexibility of the measuring device for the deflection angle of the light beam provided in this application in the actual application scenario. Specifically, please refer to Figure 3 , Figure 3 which is a schematic structural diagram of another measuring device for the deflection angle of the light beam provided in the embodiments of this application, and is described in detail as follows.

[0096] In the embodiments of this application, different from the Figure 2 schematic structural diagram of the measuring device for the deflection angle of the light beam shown, a second cone lens 2103 is further provided between the convex lens 2102 and the quadrant detector 220, so that the size of the annular light spot formed on the quadrant detector can be conveniently changed by adjusting the distance between the second cone lens 2103 and the quadrant detector 220. Since the photoelectric value detected by the quadrant detector is related to the annular light spot formed on the quadrant detector, generally, the second cone lens provided between the convex lens 2102 and the quadrant detector 220 can effectively adjust the angle detection range and sensitivity of the quadrant detector, so as to have more effective practical application value in specific application scenarios.

[0097] Of course, in order to clearly understand the specific application scenario of the measuring device for the deflection angle of the light beam provided in this application, in a feasible embodiment, a specific measuring system for the deflection angle of the light beam will be provided to measure the deflection angle of the light beam after passing through the acoustic field, so as to further analyze and determine the implementation scheme of the acoustic field distribution. Specifically, please refer to Figure 4 , Figure 4A 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.

[0098] 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.

[0099] 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.

[0100] 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.

[0101] 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.

[0102] 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:

[0103] S510, convert the parallel light beam into an annular light beam through a first conical lens.

[0104] S520, focus the annular light beam after angular deflection through a convex lens to form an annular light spot on the quadrant detector.

[0105] S530, determine the position offset of the annular light spot relative to the center of the quadrant detector according to the photoelectric values of each quadrant in the quadrant detector, so as to determine the deflection angle of the annular light beam according to the position offset.

[0106] In the embodiments of the present application, the specific implementation processes of converting the parallel light beam into an annular light beam through the first conical lens and focusing the annular light beam after angular deflection through the convex lens to form an annular light spot on the quadrant detector will not be elaborated. Specifically, reference can be made to the description of the aforementioned measuring device for the deflection angle of the light beam.

[0107] In the embodiments of the present application, in the process of determining the position offset of the annular light spot relative to the center of the quadrant detector based on the photoelectric values of each quadrant in the 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 specifically refer to the aforementioned description, that is, the deflection angle of the annular light beam can be calculated according to the ratio of the position offset to the focal length of the convex lens. The specific implementation solution is not repeated in the embodiments of the present application. The embodiments of the present application mainly illustrate how to determine the position offset of the annular light spot relative to the center of the quadrant detector based on the photoelectric values of each quadrant in the quadrant detector. In particular, in the above process, calculations will be performed based on the principle of the quadrant detector and the light intensity distribution of the annular light spot. Specifically, it is elaborated as follows.

[0108] In a feasible implementation solution in the embodiments of the present application, the step of determining the position offset of the annular light spot relative to the center of the quadrant detector according to the photoelectric values of each quadrant in the quadrant detector generally can also first determine the normalized offset of the annular light spot relative to the center of the quadrant detector based on the photoelectric values of each quadrant in the quadrant detector, and then further determine the position offset of the annular light spot relative to the center of the 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 step of determining the position offset of the annular light spot relative to the center of the quadrant detector according to the photoelectric values of each quadrant in the quadrant detector includes:

[0109] Determine the normalized offset of the annular light spot relative to the center of the quadrant detector according to the photoelectric values of each quadrant in the quadrant detector;

[0110] Determine the position offset of the annular light spot relative to the center of the quadrant detector based on the normalized offset of the center of the quadrant detector and the preset annular light spot intensity distribution model.

[0111] Among them, the calculation process of the normalized offset of the center of the quadrant detector can usually be similar to the foregoing, that is, obtained through the following calculation formula:

[0112] ;

[0113] Among them, the explanations of each parameter have been specifically described above, and the embodiments of the present application will not repeat them here.

[0114] On this basis, considering the light intensity distribution of the annular light spot, the embodiments of the present application further provide the position offset of the centroid of the annular light spot relative to the center of the quadrant detector ( x 0 , y 0 ) and the function relationship between the normalized offset provided above , which will be specifically described below.

[0115] Specifically, due to the focusing effect of the convex lens, the light intensity distribution of the annular light spot on the focal plane can be considered to be all distributed on the circular ring, and the width of the circular ring Δr→0, that is:

[0116] ;

[0117] Among them, r0 is the radius of the circular ring, that is, the radius of the annular light spot, P is the total light intensity of the annular light spot, where is the Dirac function, that is, it is not zero within the brackets, that is takes the value of 0 in the case of, but the integral over the entire domain is 1.

[0118] In order to simplify the above formula for subsequent calculations, in the embodiments of the present application, it is considered to transform the light intensity distribution of the annular light spot into the polar coordinate system, that is, to consider constructing an annular light spot intensity distribution model based on the polar coordinate system, and thus the following can be obtained:

[0119] ;

[0120] That is to say, within the annular light spot, the light intensity distribution at each point in the light spot is mainly related to the polar coordinate value r at that point, that is, the polar radius. Of course, the photocurrent amplitude output by the four quadrant units is proportional to the light spot energy received by them, that is:

[0121] ;

[0122] Among them, S i is the photosensitive area of each quadrant unit.

[0123] By combining the above formulas, we can get the following formula:

[0124] ;

[0125] 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:

[0126] ;

[0127] By analyzing the symbolic function, we can further obtain the following formula:

[0128] ;

[0129] 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.

[0130] 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.

[0131] 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 The light intensity at [a certain position]. However, in fact, the ring of the circular ring spot also has a certain ring width. That is to say, based on the photocurrent distribution provided above, the normalized lateral offset E X The actual calculation formula is as follows:

[0132] ;

[0133] where the detector size is R and the ring width is d. At this time, combining the annular spot light intensity distribution model in the polar coordinate system provided above, the functional relationship between the normalized offset of the center of the four-quadrant detector and the position offset can be further determined, including the normalized lateral offset and the lateral coordinate of the centroid coordinate , that is, the functional relationship between the value of the position offset in the lateral dimension:

[0134] ;

[0135] Based on a similar process, the normalized longitudinal offset and the longitudinal coordinate of the centroid coordinate , that is, the specific functional relationship between the value of the position offset in the lateral dimension:

[0136] ;

[0137] That is, after determining the normalized offset of the annular 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 centroid of the annular spot relative to the center of the four-quadrant detector can be obtained by solving the above equation ( x 0 , y 0 ).

[0138] Of course, considering that the above equation is difficult to directly solve, therefore, in order to simplify the above calculation process, as a feasible embodiment of the present application, an implementation scheme based on rough solution iterative update calculation to obtain an accurate position offset is provided. That is to say, in an embodiment of the present application, determining the position offset of the annular 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 preset annular spot light intensity distribution model includes:

[0139] Based on the normalized offset of the center of the four-quadrant detector and the radius of the annular spot, determine the estimated offset of the annular spot relative to the center of the four-quadrant detector;

[0140] Determine the functional relationship between the normalized offset and the position offset of the center of the quadrant detector based on a preset annular light spot intensity distribution model;

[0141] Input the estimated offset 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 quadrant detector.

[0142] Among them, for the calculation process of determining the estimated offset of the annular light spot relative to the center of the quadrant detector based on the normalized offset of the center of the quadrant detector and the radius of the annular light spot, reference can be made to the foregoing formula:

[0143] ;

[0144] That is, substituting the obtained normalized offset of the center of the quadrant detector and the radius of the annular light spot (as ), the estimated offset of the annular light spot relative to the center of the quadrant detector can be obtained, which is the rough solution .

[0145] On the basis of the foregoing, by substituting the rough solution into the specific formula of the functional relationship provided above, the update of the centroid coordinates can be completed. Among them, the specific update of the centroid coordinates can be to update the longitudinal coordinates through the rough solution of the transverse coordinates, and update the transverse coordinates based on the rough solution of the longitudinal coordinates. That is, 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 quadrant detector includes:

[0146] Input the transverse offset in the estimated offset into the functional relationship to update the longitudinal offset in the estimated offset;

[0147] Input the longitudinal offset in the estimated offset into the functional relationship to update the transverse offset in the estimated offset;

[0148] Until the predicted normalized offset obtained by inputting the updated estimated offset into the functional relationship meets the preset requirements, the currently obtained updated estimated offset is used as the position offset of the annular light spot relative to the center of the quadrant detector.

[0149] Specifically, substituting the rough solution into the specific formula of the normalized offset and the centroid coordinates provided above, the calculation process of the updated estimated offset is as follows:

[0150] ;

[0151] ;

[0152] 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.

[0153] 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.

[0154] It can be seen that the measuring device and method for the beam deflection angle provided by the embodiments of the present application convert light into a ring through a conical lens, and use a convex lens to focus the ring beam to form a ring-shaped light spot, solving the defect in the related art 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 quadrant detector, so indirect measurement is required, effectively reducing the measurement cost and realizing the effective detection of a single detector. At the same time, by combining the analysis of the light intensity distribution of the formed ring-shaped light spot and the imaging principle of the quadrant detector, a specific implementation scheme is provided to calculate the displacement of the ring-shaped light spot based on the photocurrents on the four quadrants detected by the quadrant detector, so as to accurately calculate the beam deflection angle. At the same time, compared with the Gaussian distribution of the light spot energy on the circular light spot, it overcomes the defect that the non-linear relationship between the actual position of the centroid and the normalized offset due to the Gaussian edge response, so that complex compensation of the normalized offset is required to obtain the actual position of the centroid. The measurement method provided by the present application iteratively updates the estimated offset by substituting the rough solution obtained by simplified calculation into the ring-shaped light spot light intensity distribution model, so that the updated estimated offset gradually approaches the true offset result, so as to accurately and effectively obtain the position offset of the ring-shaped light spot relative to the center of the quadrant detector, and accurately calculate the deflection angle of the ring beam for further subsequent calculations, such as calculating the sound field distribution passed by the ring beam.

[0155] Of course, in order to implement the above measurement process of the beam deflection angle, in addition to the lens assembly and the quadrant detector mentioned in the measuring device for the beam deflection angle, in a feasible implementation scheme, an electronic device is also provided. The electronic device is electrically connected to the quadrant detector to collect the photoelectric values of each quadrant in the quadrant detector, so as to complete the calculation of the position offset of the ring-shaped light spot relative to the center of the quadrant detector and the deflection angle of the ring beam based on the calculation process of the beam deflection angle measurement method provided by the present application. For example, in one embodiment, a program module for executing each step in the above embodiments may be stored in the memory of the electronic device, and the computer program composed of each program module enables the electronic device to execute the steps in the beam deflection angle measurement method of each embodiment described in this specification.

[0156] For example, please refer to Figure 6 , Figure 6A schematic structural diagram of an electronic device provided by an embodiment of the present application. The electronic device includes a processor, a memory, and a network interface connected through a system bus. Among them, 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 through a network connection. When the computer program is executed by the processor, it implements a method for measuring the deflection angle of a light beam.

[0157] Those skilled in the art can understand that Figure 6 the structure shown in [the figure] is only a block diagram of some structures related to the solution of the present application, and does not constitute a limitation on the electronic device to which the solution of the present application is applied. The specific electronic device may include more or fewer components than those shown in the figure, or combine certain components, or have different component arrangements.

[0158] 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 the deflection angle of a light beam provided by the embodiments of the present application.

[0159] Those of ordinary skill in the art can understand that all or part of the processes of implementing the methods in the above embodiments can be completed by instructing relevant hardware through a computer program. 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 methods. Any reference to a memory, storage, information base, or other medium used in the embodiments provided by the present application can include at least one of non-volatile and volatile memories. 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. By way of illustration and not limitation, RAM can be in various forms, such as static random access memory (SRAM) or dynamic random access memory (DRAM), etc.

[0160] The technical features of the above embodiments can be combined arbitrarily. For the sake of brevity of description, 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, it should be considered as the scope described in this specification.

[0161] The above has introduced in detail a device and method for measuring the beam deflection angle provided by the embodiments of the present application. Specific examples are used herein to elaborate on the principle and implementation manner of the present invention. The description of the above embodiments is only used to help understand the method and its core idea of the present invention; at the same time, for those skilled in the art, according to the idea of the present invention, there will be changes in the specific implementation manner and application scope. In summary, the content of this specification should not be construed as a limitation to the present invention.

Claims

1. A measuring device for the deflection angle of a light beam, characterized in that Comprising: a lens assembly and a quadrant detector; The lens assembly at least includes a first conical lens and a convex lens. The first conical lens is used to convert a parallel light beam into an annular light beam, and the convex lens is used to focus the annular light beam after angular deflection to form an annular light spot on the quadrant detector; The quadrant detector is used to determine the normalized offset of the annular light spot relative to the center of the quadrant detector according to the photoelectric values of each quadrant in the quadrant detector; based on the normalized offset of the center of the quadrant detector and the radius of the annular light spot, determine the estimated offset of the annular light spot relative to the center of the quadrant detector; based on a preset annular light spot intensity distribution model, determine the functional relationship between the normalized offset of the center of the quadrant detector and the position offset; input 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 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 conical lens is further arranged between the convex lens and the quadrant detector; The second conical lens is used to adjust the size of the annular light spot formed on the quadrant detector to adjust the detection performance of the 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 the measurement of sound field distribution; A to-be-measured sound field area is arranged between the first conical lens and the convex lens. Wherein, the annular light beam generates angular deflection after passing through the to-be-measured sound field area; the deflection angle of the light beam is also used to determine the refractive index distribution of the sound field cross section in the to-be-measured sound field area to determine the sound field distribution of the to-be-measured sound field area.

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

5. A method for measuring the deflection angle of a light beam, characterized in that, Applied to a device for measuring the deflection angle of a light beam, the device for measuring the deflection angle of a light beam includes a lens assembly and a quadrant detector; the lens assembly at least includes a first conical lens and a convex lens; The method includes: Converting a parallel light beam into an annular light beam through a first conical lens; Focusing the annular light beam after angular deflection through a convex lens to form an annular light spot on a quadrant detector; Determining the normalized offset of the annular light spot relative to the center of the quadrant detector according to the photoelectric values of each quadrant in the quadrant detector; based on the normalized offset of the center of the quadrant detector and the radius of the annular light spot, determining the estimated offset of the annular light spot relative to the center of the quadrant detector; based on a preset annular light spot intensity distribution model, determining the functional relationship between the normalized offset of the center of the quadrant detector and the position offset; 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 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, Inputting the estimated offset into the functional relationship to update the estimated offset, so as to obtain the position offset of the annular light spot relative to the center of the 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 meets the preset requirements, and taking the currently obtained updated estimated offset as the position offset of the annular light spot relative to the center of the quadrant detector.

7. The method according to claim 5, characterized in that The calculation formula for determining the normalized offset of the annular light spot relative to the center of the quadrant detector according to the optoelectronic values of each quadrant in the quadrant detector is as follows: Among them, E X is the normalized lateral offset of the annular light spot relative to the center of the quadrant detector in the lateral direction, and E Y is the normalized longitudinal offset of the annular light spot relative to the center of the quadrant detector in the longitudinal direction; I A 、I B 、I C 、I D are the photoelectric values of the four quadrants in the quadrant detector respectively; The formula of the preset light intensity distribution model of the annular light spot in polar coordinates is as follows: Among them, O(r) is the light intensity at the polar radius r, r0 is the radius of the ring, P is the total light intensity of the annular light spot, and δ() is the Dirac function; The functional relationship between the normalized offset at the center of the quadrant detector and the position offset is: Among them, d is the width of the annular light spot, (x0, y0) is the centroid coordinate of the annular light spot, x0 is the lateral position offset of the annular light spot, and y0 is the lateral position offset of the annular light spot; The calculation formula for the estimated offset of the annular light spot relative to the center of the quadrant detector is: Among them, (x0′, y0′) is the estimated offset of the annular light spot relative to the center of the quadrant detector.

8. The method according to any one of claims 5 to 7, characterized in that, The method is applied to the measurement of the sound field distribution; The method further includes: Making the annular beam pass through the sound field area to be measured to cause the annular beam to deflect; and Determining the refractive index distribution of the sound field cross-section in the sound field area to be measured based on the deflection angle of the beam; Determining the sound field distribution of the sound field area to be measured according to the refractive index distribution of the sound field cross-section.

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