Space scattering light field distribution measurement method

Abstract

The invention discloses a space scattering light field distribution measurement method, which realizes measurement of space scattering light field distribution, and specifically comprises the following steps: S1, a tested sample or a reference sample close to ideal mirror reflection is not placed at a test position, a light source enters at a first angle, and a detector receives and measures light radiation from different angles to obtain light source light field distribution; s2, placing a tested sample at the test position, enabling the light source to enter at a second angle, receiving and measuring light radiation passing through the tested sample from different angles by the detector, and obtaining scattered light field distribution of the tested sample; and S3, decoupling the scattered light field distribution of the tested sample by using the light field distribution of the light source to obtain the corrected scattered light field distribution of the tested sample. According to the invention, the influence of the measurement system on the material scattering light field distribution test is eliminated, and the two-dimensional display detector is introduced for receiving, so that the measurement is more accurate. The method is especially obvious in effect on samples with higher specular reflection or higher transparency.

Description

Technical Field

[0001] The present invention relates to the field of optical radiation measurement, and particularly to a method for measuring the spatial scattering light field distribution. Background Art

[0002] The scattering light field distribution function of a material surface is used to define how the irradiance in a given incident direction affects the radiance in a given exit direction. It can comprehensively characterize the surface optical properties of the material and is very important for optical design and applications. To accurately measure the scattering light field distribution performance of a material, a multi-axis measurement system is generally used. By rotating the light source and the detector in space, the spatial scattering characteristics of the sample at different incident angles are measured: the light source irradiates the sample to be measured from one or more specified angles, and the detector receives the light distribution after the action of the sample (reflection or transmission); according to the anisotropy of the sample to be measured, the number of rotation axes of the multi-axis measurement system may be different. In modern instruments, there are also methods using array detectors to image to obtain the spatial light field, such as microlens imaging or conoscopic imaging. The basic principle is to map the scattering angle information into the pixels of the array detector through an optical imaging system.

[0003] However, it should be noted that the measurement system itself will affect the measurement of the bidirectional scattering characteristics. Taking the multi-axis scanning measurement system as an example, the influencing factors include the collimation degree of the light source, the size of the light spot, the size of the receiving solid angle, etc. Ideally, the incident light source for measurement is a parallel light, and the light spot of the light source and the spatial solid angle received by the detector are close to infinitesimal, and the light field distribution function of the incident light source is approximately a Dirac δ function. However, in actual measurement, affected by the size of the incident light spot and the size of the detector aperture, the light field of the incident light source and the scattering light field distribution of the sample to be measured will have a large broadening. When the sample to be measured is a diffuse surface, the broadening angle of the scattering light field distribution of the measurement system has little influence on the test result. If the sample to be measured is a highly specular or highly transparent material, the broadening angle of the scattering light field distribution of the measurement system will greatly affect the test result and cannot truly reflect the true scattering performance of these highly specular or highly transparent materials. Summary of the Invention

[0004] To solve the influence of the broadening effect of the measurement system on the test of the spatial scattering light field distribution of the material, the present invention provides a method for measuring the spatial scattering light field distribution. By performing deconvolution or ray tracing or a combination of both on the scattering light field distribution of the sample to be measured to achieve decoupling, the true surface scattering light field distribution of the material is restored, so as to be able to eliminate the influence of the measurement system itself on the test of the surface scattering light field distribution of the material, especially for specular or highly transparent samples, and the surface scattering properties of the material can be obtained more accurately.

[0005] The present invention is realized through the following technical solutions: A method for measuring the spatial scattering light field distribution, comprising the following steps:

[0006] S1: No test sample or a reference sample close to an ideal specular reflection is placed at the test position. The light source is incident at a first angle, and the detector receives and measures the light radiation from different angles to obtain the light field distribution of the light source.

[0007] S2: Place the test sample at the test position. The light source is incident at a second angle, and the detector receives and measures the scattered light radiation passing through the test sample from different angles to obtain the scattered light field distribution of the test sample.

[0008] S3: Use the light field distribution of the light source to perform decoupling operations on the scattered light field distribution of the test sample to obtain the corrected scattered light field distribution of the test sample.

[0009] In step S1, when no test sample is placed at the test position, it is equivalent to using air as the test sample, which is applicable to a measurement system with the function of measuring the transmitted light field distribution; while placing a reference sample close to an ideal specular reflection at the test position is applicable to a system with only the function of measuring the reflected light field distribution. The so-called ideal specular reflection means that its reflected light field distribution is a Dirac δ function, with only specular reflected light and no scattered light.

[0010] In actual tests, the spatial scattered light field distribution of the test sample directly measured by the measurement system is actually the convolution of the broadening effect of the measurement system and the true scattered light field distribution of the material, as shown in formula (1).

[0011]

[0012] Among them, represents the spatial scattered light field distribution function of the test sample measured by the measurement system, denoted as f test (·), represents the broadening function of the measurement system, denoted as g(·), represents the actual spatial scattered light field distribution function of the test sample, denoted as f actual (·), represents the zenith angle and azimuth angle of the incident light source, represents the zenith angle and azimuth angle of the scattering direction, λ represents the wavelength of the incident light source, and the test sample can produce different scattered light field distributions for incident light of different wavelengths; in actual mathematical calculations, f test (·), g(·), f actual (·) need to be in the same spherical coordinate system. Therefore, coordinate transformation processing needs to be done before this, as detailed below. After convolution, the specular angle or direct transmission angle of the actual scattered light field distribution of the specular sample or highly transparent sample will be broadened. At this time, it is necessary to correct the measured scattered light field distribution, otherwise it will have a relatively large impact on the subsequent optical simulation and evaluation of the material.

[0013] Compared with the traditional method for measuring the spatial scattered light field distribution, in the technical solution of the present invention, a step of measuring the light field distribution of the measuring light source is added. The purpose is to obtain the broadening function of the measuring system. By decoupling the light field distribution of the light source and the scattered light field distribution of the sample to be measured obtained under the same conditions, the corrected scattered light field distribution of the sample to be measured can be obtained. This decoupling process can be achieved through deconvolution or ray tracing. The corrected scattered light field distribution of the sample to be measured removes the broadening effect caused by the factors of the measuring system itself and restores the true scattering performance and surface topography characteristics of the sample to be measured.

[0014] As a technical solution, the light field distribution of the light source and the scattered light field distribution of the sample to be measured are both obtained by the method of spatial rotation scanning of the detector. Each scanning angle of the detector corresponds to a light field angle, and the center of the sample to be measured is placed at the rotation center of the spatial angle scanning. It should be noted that in the spatial scattered light field distribution measuring system, there may be two or more arranged detectors, and the optical axes of the two or more detectors form a certain angle and face the rotation center at the same time. This technical solution is mainly to improve the measurement efficiency by the simultaneous operation of two or more detectors in one scan.

[0015] As a technical solution, in step S1, a first receiving aperture is arranged in front of the detector, and the spatial scanning angle interval used is not greater than the angle subtended by the first receiving aperture with respect to the rotation center; in step S2, a second receiving aperture is arranged in front of the detector, and the size of the second receiving aperture is equal to or greater than the size of the first receiving aperture. Such an aperture setting can ensure that the angular resolution of the light field distribution of the light source is not lower than the angular resolution of the scattered light field distribution of the sample to be measured, so as to achieve the purpose of high-resolution measurement.

[0016] Furthermore, in step S1, according to the spatial response distribution of the detector under the first receiving aperture and the scanning angle interval, decoupling calculation is performed on the measured light field distribution of the light source to obtain the corrected light field distribution of the light source. In step S2, it also includes decoupling calculation of the scattered light field distribution of the sample to be measured according to the spatial response distribution of the detector under the second receiving aperture and the scanning angle interval. The purpose of the decoupling calculation is to convert the original radiation data into the spatial scattered light field distribution. As a specific implementation, when a reference sample close to an ideal specular reflection is used in step S1, the known scattered light field distribution function of the reference sample is used to perform decoupling calculation on the light field distribution of the light source.

[0017] As a technical solution for specific implementation, the spatial angle scanning system can be a two-axis, three-axis or four-axis measurement system. The two-axis spatial angle scanning system generally includes a light source axis and a detector axis, and the changes in the zenith angles of the light source and the detector are realized through a control system and a mechanical rotation device. The three-axis spatial angle scanning system has one more azimuth rotation axis for the detector compared to the two-axis spatial angle scanning system, realizing the full-space scanning of the reflected / transmitted light. For anisotropic samples to be measured, it is also necessary to change the incident azimuth angle of the light source, and a four-axis spatial angle scanning system needs to be used for measurement. The four-axis spatial angle scanning system can simultaneously realize the full-space changes in the zenith angles and azimuth angles of the light source and the detector.

[0018] The present invention also provides a method for measuring the spatial scattered light field distribution. This method uses an angular resolution imaging detection device with an imaging unit and a two-dimensional array detector to measure the scattered light field distribution. Each pixel or pixel region in the two-dimensional array detector corresponds to an angle, and specifically includes the following steps:

[0019] S1: No sample to be measured or a reference sample close to an ideal specular reflection is placed at the test position. The light source is incident at a first angle, and the light source light field distribution is obtained using the angular resolution imaging detection device.

[0020] S2: The sample to be measured is placed at the test position. The light source is incident at a second angle, and the angular resolution imaging detection device is used to receive and measure the scattered light radiation at different angles after passing through the sample to be measured, obtaining the scattered light field distribution of the sample to be measured.

[0021] S3: The scattered light field distribution of the sample to be measured is decoupled and calculated using the light source light field distribution to obtain the corrected scattered light field distribution of the sample to be measured.

[0022] In this technical solution, through the imaging element, the array detector can simultaneously measure the scattered light radiation at two or more angles, thereby improving the measurement speed.

[0023] Furthermore, the angular resolution imaging detection device faces the sample to be measured and rotates and scans in space with the sample to be measured as the rotation center to obtain the scattered light field distribution of the sample to be measured. At each scanning angle, the angular resolution imaging detection device obtains the light field information at two or more light field angles. It should be noted that the center of the sample to be measured is not necessarily placed at the rotation center, which mainly depends on the position of interest on the sample to be measured. This position is set at the rotation center. When the sample to be measured has a certain thickness, usually the surface of the sample to be measured is set at the rotation center.

[0024] As a preferred technical solution, the above imaging method is implemented by using an angular resolution imaging detection device with a two-dimensional microlens array. It images the scattered light of the sample to be measured onto a two-dimensional array detector, where each microlens corresponds to a scattering angle. The scattered light field distribution at each spatial angle is imaged onto a pixel or pixel region on the array detector. This technical solution scans multiple angles in space to obtain the scattered light field distribution of the entire space.

[0025] As a preferred technical solution, the above imaging method is implemented by using conoscopic imaging. After the light source irradiates the surface of the sample to be measured, its transmitted light enters the conoscopic system. The sample to be measured is placed on the working plane of the conoscope, so that the conoscope can receive the reflected / transmitted light within a large angular range. Through the lens group of the conoscope, the light incident at different angles can be imaged onto the plane of the array detector, where each pixel in the array detector corresponds to a spatial angle. This technical solution can obtain the scattered light field distribution of the sample to be measured in one imaging measurement, and the measurement speed is fast.

[0026] As a technical solution, the detector is an array detector with multi-channel response. Specifically, a high-resolution array detector (such as a CMOS or CCD two-dimensional area array detector) can be used to capture the light field distribution of the light source and the scattered light field distribution of the sample to be measured respectively. The size of a single pixel of the array detector can reach the micron level, and it can record the light intensity information of multiple pixel points at the same time. Moreover, the measurement values of multiple pixel points can be cumulatively calculated with each other (also known as the macro mode). Therefore, the diagonal angle of the array detection surface relative to the sample to be measured can be controlled at a small angle through the tiny pixel units of the array detector, and at the same time, the measurement of the scattered light field distribution is also very precise, which can greatly improve the efficiency and resolution of the acquisition of the scattered light field distribution information.

[0027] As a technical solution, the decoupling operation of the scattered light field distribution of the sample to be measured by using the light field distribution of the light source includes one or a combination of two or more of ray tracing and deconvolution.

[0028] As a technical solution, the light source is a monochromatic light source, or the light source is a broadband light source and is incident on the surface of the sample to be measured through a collimation system to ensure that the light irradiated on the sample to be measured has good directivity and uniformity.

[0029] As a preferred technical solution, the monochromatic light source can be a monochromatic laser light source or a monochromatic LED light source, or a broadband light source can be split into monochromatic light by a monochromator or filtered by a narrow-band color filter. The broadband light source can be an incandescent lamp or an LED white light source. In practical applications, different measured samples have different requirements for the incident light source. The corresponding incident light source can be set according to specific lighting requirements, and the luminous power of the incident light source can be controlled to meet the lighting needs of different types of measured samples.

[0030] As a preferred technical solution, the scattered light field distribution is a function with two-dimensional angles as variables. The two-dimensional angles are described as the angle between planes and the angle within the plane, corresponding to the azimuth angle and the zenith angle. In the step of decoupling the scattered light field distribution of the measured sample by using the light source light field distribution, the scattered light field distribution in each plane is decoupled. During the operation, the material space scattered light field distribution function and the light source light field distribution function need to correspond one by one in terms of spatial angles.

[0031] As a preferred technical solution, the first incident angle is incident perpendicular to the test position plane. If no measured sample is placed, the system measures the scattered light field distribution (or the light source light field distribution) in the state of direct transmission of air. No matter what angle the light source is incident at, its light source light field distribution remains unchanged. However, when the light source is incident perpendicularly, the calculation is simpler and the complexity is lower. Only the light source light field distribution within a smaller receiving angle range needs to be scanned. At this time, the light source light field distribution obtained in the step S1 is denoted as where the two 0° respectively represent that both the zenith angle and the azimuth angle of the input light are 0°.

[0032] As a technical solution, before decoupling the scattered light field distribution of the measured sample by using the light source light field distribution, the obtained light source light field distribution is subjected to coordinate transformation according to the incident light angle, that is, angle rotation, to ensure that the decoupling operation is carried out in the same coordinate system. The transformation angle is the incident angle of the light source when testing the measured sample. To obtain the light source light field distribution incident at an angle of without the measured sample, which is That is, the broadening function g(·) of the measurement system.

[0033] Specifically, the light source light field distribution is subjected to coordinate rotation. As Figure 1 shown, the test light source rotates from the incident angle of (0°, 0°) perpendicular to the sample surface in the step S1 to the incident angle in the step S2. Its scattered light field distribution remains relatively unchanged, only the overall angle is converted. The converted expression is

[0034]

[0035] As a technical solution, the scattered light field distribution is a function with two-dimensional angles as variables, and the two-dimensional angles can be described as the angle between planes and the angle within a plane; in the decoupling operation of the scattered light field distribution of the sample to be measured using the light source light field distribution, the scattered light field distribution in each plane is decoupled. During the operation, the material space scattered light field distribution function and the light source light field distribution function need to correspond one by one in terms of spatial angles. Taking the deconvolution decoupling operation as an example, the convolution kernel is the light source light field distribution in the corresponding plane.

[0036] Specifically, when the light source is incident on the surface of the sample to be measured at an angle of , the measured scattered light field distribution is It is a function with two-dimensional angles as variables, describing the scattered light field distribution in the angle space between planes. When the azimuth angle of the receiving surface of the detector remains unchanged, the scattered light field distribution describes the light scattering light field distribution in the angle space within a plane.

[0037] As a technical solution, during the process of decoupling the scattered light field distribution of the sample to be measured using the light source light field distribution, it includes: fitting a modified scattered light field distribution function of the sample to be measured using a fitting function and performing deconvolution calculation in an iterative manner. The fitting function is a Gaussian function or a Lorentz function or a cosine function or an ABg function or a Henyey-Greenstein function or a Gegenbauer function or a combination of them, so as to be applicable to the simulation of the reflection and transmission characteristics of different materials respectively. Specifically, determining the convergence threshold is required for deconvolution calculation in an iterative manner, and this convergence threshold can be set by experience or calibrated by testing with a standard device. The fitting and iterative processes are briefly described below respectively.

[0038] Specifically, at a certain angle within a plane of the determined light source incident angle , the scattered light field distribution function can be simplified to f test (θ s ). Traverse all to obtain the two-dimensional scattered light field distribution function in the spherical coordinate system at the S2 incident angle. Its expressions under different fitting functions are different.

[0039] If the fitting function is a Gaussian function, the scattered light field distribution function is as follows:

[0040]

[0041] Among them, A, σ, and μ are all characteristic constants of the Gaussian fitting function, which are related to the shape of the distribution and can be obtained by the method of fitting approximation.

[0042] If the fitting function is a Lorentz function, the scattered light field distribution function is as follows:

[0043]

[0044] Among them, A and γ are all characteristic constants of the Lorentz fitting function, which are related to the shape of the distribution and can be obtained by the method of fitting approximation.

[0045] If the fitting function is a cosine function, the scattered light field distribution function is as follows:

[0046] f test (θ s ) = Acos(Bθ s )…………………………………(5)

[0047] Among them, A and B are characteristic constants of the cosine fitting function, which are related to the shape of the distribution and can be obtained by the method of fitting approximation.

[0048] If the fitting function is an ABg function, the scattered light field distribution function is as follows:

[0049]

[0050] Among them, A, B, and g are all characteristic constants of the ABg fitting function, which are related to the shape of the distribution and can be obtained by the method of fitting approximation.

[0051]

[0052] If the fitting function is a Henyey-Greenstein function, the scattered light field distribution function is as follows:

[0053]

[0054] Among them, g HG is the characteristic constant of the Henyey-Greenstein fitting function, which is related to the shape of the distribution and can be obtained by the method of fitting approximation.

[0055] If the fitting function is a Gegenbauer function, the scattered light field distribution function is as follows:

[0056]

[0057] Among them, α G , g Gis a characteristic constant of the Gegenbauer fitting function, which is related to the shape of the distribution and can be obtained by means of fitting approximation.

[0058] In addition, the scattered light field distribution can also be a combination of multiple functions mentioned above, such as the Gaussian-Lorentz function:

[0059]

[0060] where G a (θ′ s ) and L(θ′ s ) are the Gaussian function and the Lorentz function respectively.

[0061] As a technical solution, in the decoupling operation of the scattered light field distribution of the measured sample by using the light source light field distribution, the iterative process can adopt the following process: g(·) is the broadened function after coordinate rotation and serves as the deconvolution kernel; use f test (·) as the initial value of f actual (·), calculate the convolution value R(·) = g(·) * f actual (·), and compare it with the actually measured f test (·), for example, calculate the ratio of the two sets of values corresponding to each angle, determine whether it converges to a certain threshold, or calculate whether the total transmission or total reflection value converges to a certain standard value. If it does not converge, adjust the corresponding characteristic constant according to the selected fitting function, iterate multiple times, or directly adopt the Richardson-Lucy (RL) algorithm, use a specific iterative formula, and perform the next iterative calculation until convergence; at this time, the adjusted f actual (·) is the actual spatial scattered light field distribution function of the measured sample. Taking the RL algorithm as the fitting adjustment strategy, this process can be illustrated by the following formula:

[0062]

[0063] where k is the number of iterations, T is the ratio of the fitting convolution value to the true value at each angle after k iterations, and g flipped (·) represents the flipping (rotation by 180°) of the convolution kernel. When T converges to the preset threshold, the iteration ends.

[0064] As a technical solution, the light source light field distribution described above can be simulated by a Gaussian distribution or a uniform distribution. The scattered test light source generally has certain distribution characteristics after passing through the optical system, such as the Gaussian distribution of the laser light source or the uniform distribution of the white light source. The former can be simulated by a Gaussian distribution: where A, σ, μ are Gaussian function parameters and can be obtained by measurement and fitting; the latter can be simulated by a constant Where K is a measurable constant, and C1 and C2 respectively represent the sets of all zenith angles and azimuth angles corresponding to the uniform light spot.

[0065] As a technical solution, if the material has linear response characteristics, the decoupling operation in step S3 can be obtained by performing deconvolution calculation in the frequency domain. The specific operation steps are as follows: perform discrete Fourier transform on both sides of the convolution function It can also be written as Where are respectively The discrete Fourier transform of; then the frequency domain function of the measured true scattered light field distribution can be obtained Where * represents conjugate, and the small constant ∈ is to prevent noise amplification; then perform inverse discrete Fourier transform on both sides to obtain the scattered light field distribution of the sample

[0070]

[0071] As a technical solution, the polarization state and / or spot size and / or relative spectral power distribution of the light source can be adjusted. Under different polarization states, spot sizes and relative spectral power distributions of the light source, measure the light field distribution of the light source, and perform decoupling calculation and correction on the scattered light field distribution of the measured sample under the same conditions.

[0072] As a preferred solution, the polarization state of the above light source can be adjusted by a polarizer, and can also be cut in and out or manually switched by a mechanical device. The influence of the change in its polarization state on the expression of the scattered light field distribution function can be solved by introducing the polarization angle α. Specifically, the scattered light field distribution function can be decomposed in two polarization directions, such as And Is the change in the amplitude ratio of the two polarization directions, where g(·), f actual (·), f test (·) can all be expressed in the form of , and calculate through the decomposition in two polarization directions. As a preferred solution, the spot size of the above light source is adjusted by a diaphragm, and the size of the spot can also be switched or manually switched by a mechanical device. The adjustment of the spot size can be adjusted through the parameters of the fitting function.

[0073] As a preferred solution, when measuring the sample to be measured, the light source is incident at two or more angles, and the scattered light field distributions of the sample to be measured at each incident angle are measured respectively, and a decoupling operation is performed to obtain the corrected scattered light field distribution of the sample to be measured. Specifically, the light source can be incident on the surface of the sample to be measured at multiple angles to measure the scattered light field distributions of the sample to be measured at multiple incident angles. Each time the incident angle of the light source is switched, steps S2 and S3 are repeated to obtain the corrected scattered light field distribution of the sample under the incident light source.

[0074] It should be noted that the scattered light field distribution function described in the present invention is a bidirectional scattered light field distribution function BSDF or a differential scattered light field distribution function DSF.

[0075] Specifically, the bidirectional scattered light field distribution function BSDF is calculated by the following formula:

[0076]

[0077] where represents the zenith angle and azimuth angle of the incident light source, represents the zenith angle and azimuth angle of the scattering direction, represents at the differential luminance at the scattering angle coordinate, represents at the differential illuminance on the surface of the sample to be measured at the scattering angle coordinate, represents at the incident angle the bidirectional scattered light field distribution value at the receiving angle.

[0078] The differential scattered light field distribution function DSF is calculated by the following formula:

[0079]

[0080] where represents at the incident angle the differential scattered light field distribution value at the receiving angle.

[0081] Advantages of the present invention: Compared with the traditional method for measuring the spatial scattered light field distribution, the present invention adds the step of measuring the light field distribution of the light source, and obtains the corrected scattered light field distribution of the sample to be measured by deconvolving the light field distribution of the light source and the scattered light field distribution of the sample to be measured obtained by measuring through the same system. The corrected scattered light field distribution of the sample to be measured removes the broadening effect caused by the non-ideal measurement system itself, and restores the true scattering performance and surface topography characteristics of the sample. At the same time, the present invention can obtain the spatial scattered light field distribution through the angular resolution imaging detection device, which can improve the measurement speed and spatial resolution. Without significantly changing the hardware of the measurement system, the present invention innovatively utilizes the existing configuration, and can obtain the corrected sample scattering function by measuring an additional set of data and algorithms, and thus obtain the surface scattering properties of the sample with higher accuracy, without the need to spend a large cost to improve the system performance, such as improving the parallelism of the incident light source, improving the spatial resolution of the receiving system, etc. The present invention has the characteristics of high measurement accuracy, simple operation, powerful function, low cost, etc. The present invention also proposes an angular resolution imaging detection device to obtain the spatial scattered light field distribution, and innovatively uses the imaging unit and the two-dimensional array detector to increase the dimension of the spatial scattering measurement, and thus obtains higher measurement resolution and measurement speed, which greatly improves the measurement accuracy of the scattered light field distribution of specular reflection or direct transmission materials.

[0082] The present invention is applicable to the spatial scanning measurement system, especially applicable to the two-dimensional imaging type spatial scattered light field distribution measurement system, with a wide application range, and can be applicable to almost all types of spatial scattered light field distribution characteristic measurement systems. The present invention can not only be used to measure the bidirectional scattering distribution function (BSDF), but also be used to realize the analysis of the differential scattering distribution (DSF), with strong practicability. BRIEF DESCRIPTION OF THE DRAWINGS

[0083] Appendix Figure 1 is a schematic diagram of the coordinate system of the present invention;

[0084] Appendix Figure 2 is a schematic diagram of the measurement system of Embodiment 1 of the present invention;

[0085] Appendix Figure 3 is a schematic diagram of the measurement method flow of Embodiment 1 of the present invention;

[0086] Appendix Figure 4 (a) is a schematic diagram of the measured scattered light field distribution without placing the sample in Embodiment 1 of the present invention;

[0087] Appendix Figure 4 (b) is a schematic diagram of the measured scattered light field distribution when placing the sample in Embodiment 1 of the present invention;

[0088] Appendix Figure 4(c) Schematic diagram of the scattered light field distribution of the measured sample after correction in the first embodiment of the present invention;

[0089] Appendix Figure 5 (a) Schematic diagram of the scattered light field distribution measured without a sample in the second embodiment of the present invention;

[0090] Appendix Figure 5 (b) Schematic diagram of the scattered light field distribution measured with a sample placed in the second embodiment of the present invention;

[0091] Appendix Figure 5 (c) Schematic diagram of the scattered light field distribution of the measured sample after correction in the second embodiment of the present invention;

[0092] Appendix Figure 6 Schematic diagram of the measurement structure and test principle in the third embodiment of the present invention;

[0093] Appendix Figure 7 Schematic diagram of the measurement structure and test principle without a sample in the fourth embodiment of the present invention;

[0094] Appendix Figure 8 Schematic diagram of the measurement structure and test principle with a sample placed in the fourth embodiment of the present invention. Detailed implementation manner

[0095] Embodiment 1

[0096] This embodiment provides a method for measuring the spatial scattered light field distribution, and the measured sample is a plane mirror. Figure 2 Schematic diagram of the measurement system for this embodiment, Figure 3 Schematic diagram of the flow of the measurement method for this embodiment, Figure 4 (a), Figure 5 (a) Schematic diagram of the scattered light field distribution measured by the measurement system without a sample, Figure 4 (b), Figure 5 (b) Schematic diagram of the scattered light field distribution measured by the measurement system with a sample placed, Figure 4 (c), Figure 5 (c) Schematic diagram of the scattered light field distribution of the measured sample after correction.

[0097] In this embodiment, a four-axis spatial angle scanning system is used to measure the spatial scattered light field distribution of the material. The schematic diagram of the device structure is as shown in Figure 2As shown in the figure, it includes a first base 1 and a second base 2; a laser positioning unit 9 and a first rotating arm 3 that rotates around a horizontal axis are provided on the first base 1, and the laser emitted by the laser positioning unit 9 passes through the first rotating arm 3, and the laser optical axis is coaxial with the horizontal axis; a second rotating arm 6 that rotates around a vertical axis is provided on the second base 2, and the second rotating arm 6 is further provided with a sample rotating table 7 that rotates around a vertical axis and a third rotating arm 8 that rotates around a horizontal axis; the sample rotating table 7 includes a sample stage 7-1, a sample rotating mechanism 7-2 and a vertical adjustment unit 7-3; the sample stage 7-1 is arranged on the sample rotating mechanism 7-2, and the sample rotating mechanism 7-2 is connected to the second rotating arm 6 through the vertical adjustment unit 7-3, and the vertical adjustment unit 7-3 includes an adjustment knob and a vertical moving base; the sample stage 7-1 further includes a fixture 11 for fixing the sample to be measured, and the sample to be measured can be fixed on the sample stage 7-1 through the fixture 11; a measurement and control center 10 electrically connected to the first rotating arm 3, the second rotating arm 6, the third rotating arm 8, the sample rotating table 7, the incident light source 4 and the angular resolution imaging detection device 5 is further provided on the first base 1; the angular resolution imaging detection device 5 has an imaging unit and a two-dimensional array detector; the measurement and control center 10 includes a human-computer interaction unit 19, and the human-computer interaction unit 19 is located inside the first base 1; one end of the first rotating arm 3 is provided with the incident light source 4 and one end of the third rotating arm 8 is provided with the angular resolution imaging detection device 5; a monitoring unit 16 is arranged beside the incident light source 4. The rotation ranges of the first rotating arm 3 and the third rotating arm 8 are both -180° to +180°, and the rotation ranges of the second rotating arm 6 and the sample stage 7-1 are both 0° to 360°; the angular resolution of the first rotating arm 3, the second rotating arm 6, and the third rotating arm 8 is all ±0.01°. The incident light source 4 includes laser light sources with different wavelengths and different spot sizes, and the spot diameters are 2 mm and 10 mm respectively, and the incident light beam of the incident light source 4 irradiates the surface of the sample to be measured in the form of parallel light.

[0098] A method for measuring the spatial scattered light field distribution, as Figure 3 shown, specifically includes the following steps:

[0099] B1: Before measurement, first perform height positioning on the sample rotating table 7, turn on the incident light source 4 and the laser positioning unit 9. At this time, an intersection point will be formed between the incident light emitted by the incident light source 4 and the laser emitted by the laser positioning unit 9. Adjust the vertical adjustment unit 7-3 so that the center of the surface of the sample to be measured coincides with the intersection point, then the positioning is considered completed.

[0100] B2: No test sample is placed on the sample stage 7-1. The measurement and control center 10 controls the first rotating arm 3 to make the incident light source 4 incident at an angle perpendicular to the sample stage 7-1; controls the second rotating arm 6 and the third rotating arm 8 to enable the angular resolution imaging detection device 5 to obtain the scattered light field distribution (or the light source light field distribution) in the air direct transmission state through imaging reception measurement. In this embodiment, with the light source incident vertically, only the scattered light field distribution of the air within a single receiving angle needs to be scanned, as shown in Figure 4 (a).

[0101] B3: Place the test sample on the sample stage 7-1. The measurement and control center 10 controls the first rotating arm 3 to drive the incident light source 4 to irradiate the test sample at different angles; at the same time, the measurement and control center 10 controls the second rotating arm 6 and the third rotating arm 8 to drive the angular resolution imaging detection device 5 to receive and measure the light rays after the action of the test sample through imaging in the full space; when the second rotating arm 6 rotates, the third rotating arm 8 and the sample rotating stage 7 both rotate at an angle along with the second rotating arm 6. At this time, the sample rotating mechanism 7-2 can be controlled to rotate the sample stage back to the original position to avoid the influence of the change in the position of the test sample on the measurement result; the measurement result is displayed by the human-computer interaction unit 19, and the scattered light field distribution passing through the test sample is measured, as shown in Figure 4 (b).

[0102] B4: Use the light source light field distribution to perform deconvolution on the scattered light field distribution of the test sample. Specifically, a Gaussian function is used to fit the corrected scattered light field distribution function of the test sample and an iterative method is used for deconvolution calculation to obtain the corrected scattered light field distribution of the test sample, as shown in Figure 4 (c).

[0103] In this embodiment, the scattered light field distribution measured by the measurement system is a bidirectional scattered light field distribution, which is calculated according to the formula ; where represents the zenith angle and azimuth angle of the incident light source, represents the zenith angle and azimuth angle of the scattering direction, represents at the differential luminance at the scattering angle coordinate, represents at the differential illuminance on the surface of the test sample at the scattering angle coordinate, represents at the incident angle the bidirectional scattered light field distribution value at the receiving angle.

[0104] In this embodiment, a Gaussian function is used for fitting. At a certain plane angle under the determined light source incident angle , the scattered light field distribution function is simplified to ftest (θ s ) is obtained by iteration according to the formula ; where both σ and μ are characteristic constants of the Gaussian fitting function, related to the shape of the distribution, and can be obtained by the method of fitting approximation. Determining the convergence threshold is required for deconvolution calculation by the iterative method, and this threshold can be set empirically or calibrated through testing with a standardizer.

[0105] For the convenience of calculation, before performing the step B4, the coordinate transformation of the light source light field distribution is carried out as follows:

[0106] C1: Obtain the light source light field distribution through the step B2

[0107] C2: Under spherical coordinates, rotate the light source light field distribution in C1 by the zenith angle of θ i and the azimuth angle of , where θ i and are respectively the incident zenith angle and azimuth angle of the test light source in the step B3, that is, the divergence angle coordinates in the formula are respectively adjusted by an incident light angle, and expressed by the formula as

[0108] The above process pseudocode can be expressed as:

[0109]

[0110] Embodiment 2

[0111] This embodiment provides another method for measuring the spatial scattered light field distribution. The sample to be measured is a diffuse reflection glass, and a three-axis spatial angle scanning system is used to measure the spatial scattered light field distribution of the material. The schematic diagram of the device structure is the same as that in Embodiment 1, and specifically includes the following steps:

[0112] D1: Before measurement, first perform height positioning on the sample turntable 7, turn on the incident light source 4 and the laser positioning unit 9. At this time, an intersection point will be formed by the incident light emitted by the incident light source 4 and the laser emitted by the laser positioning unit 9. Adjust the vertical adjustment unit 7-3 so that the center of the sample to be measured coincides with the intersection point, and it is considered that the positioning is completed.

[0113] D2: Do not place the sample to be measured on the sample stage 7-1. The measurement and control center 10 controls the first rotating arm 3 so that the incident light source 4 is incident at an angle perpendicular to the sample stage 7-1; controls the second rotating arm 6 and the third rotating arm 8 so that the angular resolution imaging detection device 5 receives and measures the scattered light field distribution in the air direct transmission state through imaging, as shown in Figure 5 (a).

[0114] D3: Place the sample to be measured on the sample stage 7-1. The measurement and control center 10 controls the first rotating arm 3 to drive the incident light source 4 to irradiate the sample to be measured at different angles. At the same time, the measurement and control center 10 controls the second rotating arm 6 and the third rotating arm 8 to drive the angular resolution imaging detection device 5 to scan and receive the light after being affected by the sample to be measured in the entire space through imaging and perform measurements. When the second rotating arm 6 rotates, the third rotating arm 8 and the sample rotating stage 7 both rotate at an angle along with the second rotating arm 6. At this time, the sample rotating mechanism 7-2 can be controlled to rotate the sample stage back to the original position to avoid the influence of the change in the position of the sample to be measured on the measurement result. The measurement result is displayed by the human-computer interaction unit 19, and the scattered light field distribution passing through the sample to be measured is measured, such as Figure 5 (b) as shown.

[0115] D4: Use the light field distribution of the light source to correct the scattered light field distribution of the sample to be measured. Use the cosine function to fit the scattered light field distribution function of the corrected sample to be measured and perform deconvolution calculation in an iterative manner to obtain the scattered light field distribution of the corrected sample to be measured, such as Figure 5 (c) as shown.

[0116] Example 3

[0117] This example provides another method for measuring the spatial scattered light field distribution. The sample to be measured is a specular reflection glass. The spatial scattered light field distribution of the material is measured using a three-axis spatial angle scanning system. The schematic diagram of the device structure is the same as that in Example 1, and specifically includes the following steps:

[0118] E1: Before measurement, first perform height positioning on the sample rotating stage 7. Turn on the incident light source 4 and the laser positioning unit 9. At this time, an intersection point will be formed between the incident light emitted by the incident light source 4 and the laser emitted by the laser positioning unit 9. Adjust the vertical adjustment unit 7-3 so that the center of the sample to be measured coincides with the intersection point, which is regarded as the positioning completed.

[0119] E2: Do not place the sample to be measured on the sample stage 7-1. The measurement and control center 10 controls the first rotating arm 3 so that the incident light source 4 is incident at an angle perpendicular to the sample stage 7-1. Control the second rotating arm 6 and the third rotating arm 8 so that the angular resolution imaging detection device 5 receives and measures the scattered light field distribution in the air direct transmission state through imaging, such as Figure 5 (a) as shown.

[0120] E3: Place the sample to be measured on the sample stage 7-1. The measurement and control center 10 controls the first rotating arm 3 to drive the incident light source 4 to irradiate the sample to be measured at different angles. At the same time, the measurement and control center 10 controls the second rotating arm 6 and the third rotating arm 8 to drive the angular resolution imaging detection device 5 to scan and receive the light after being affected by the sample to be measured through imaging in the whole space and conduct measurements. When the second rotating arm 6 rotates, the third rotating arm 8 and the sample rotating stage 7 both rotate at an angle along with the second rotating arm 6. At this time, the sample rotating mechanism 7-2 can be controlled to rotate the sample stage back to the original position to avoid the influence of the change in the position of the sample to be measured on the measurement result. The measurement result is displayed by the human-computer interaction unit 19, and the scattered light field distribution passing through the sample to be measured is obtained, such as Figure 5 (b) as shown.

[0121] E4: Use the light field distribution of the light source to correct the scattered light field distribution of the sample to be measured. Fit the corrected scattered light field distribution function of the sample to be measured with a cosine function and perform deconvolution calculation in an iterative manner to obtain the corrected scattered light field distribution of the sample to be measured, such as Figure 5 (c) as shown.

[0122] The device structure schematic and test principle of the two-dimensional array detector are shown in Appendix Figure 6 . The device structure of the two-dimensional array detector specifically includes: a microlens array 21, a two-dimensional array pixel 22, a detector housing 23, a data processing module 33, a communication port 31, and a power port 32. When the scattered light 25 of a certain angle of the sample to be measured 30 passes through a microlens 24 on the microlens array 21 and is received and imaged as an image 27 on the two-dimensional array pixel 22, the scattered light field distribution of this angle is obtained. Each microlens on the microlens array corresponds to a certain scattering angle of the sample to be measured, and its image is located on some pixels of the two-dimensional array pixel 22, so the scattered light field distributions at these angles are obtained.

[0123] Example 4

[0124] This example provides another method for measuring the spatial scattered light field distribution. The sample to be measured is a transmissive glass, and a conoscopic angle scanning system is used to measure the spatial scattered light field distribution of the material. The device structure schematic is shown in Appendix Figure 7 , and specifically includes the following steps:

[0125] F1: First, do not place a sample on the sample platform 40. The incident light 48 is perpendicularly incident on the platform surface, and its air scattered light 47 is imaged onto the two-dimensional array detector 42 by the lens 41 of the conoscopic lens, and the light field distribution of the light source is decoupled.

[0126] F2: Next, place the sample 50 on the sample stage 40. The incident light 51 is incident on the sample 50 at a certain angle, and its scattered light 52 is imaged onto the two-dimensional array detector 42 by the lens 41 of the conoscopic lens, and the scattered light field distribution of the sample is decoupled and obtained.

[0127] F3: Use the light field distribution of the light source to correct the scattered light field distribution of the sample to be measured. Fit the corrected scattered light field distribution function of the sample to be measured with a Gaussian function and perform deconvolution calculation in an iterative manner to obtain the corrected scattered light field distribution of the sample to be measured.

[0128] The schematic diagram of the structure and principle of the conoscopic lens measurement is shown in the appendix Figure 7 , and the conoscopic lens specifically includes: a conoscopic lens lens 41, a two-dimensional array sensor 42, a housing 43, a data processing module 46, a communication port 44, and a power port 45.

[0129] The above four embodiments are all applicable to the measurement of the spatial scattered light field distribution of other solid or liquid samples. Among them, the liquid sample can be loaded in other containers and fixed on the sample stage 7-1 by a fixture, and has the advantages of wide application range, high test efficiency, and high measurement accuracy.

[0130] The above embodiments have specifically described the technical solutions of the present invention, but the technical solutions of the embodiments are not limited to these descriptions. The protection scope of the present invention is defined by the claims, and any simple modification based on the claims of the present invention is included in the protection scope of the present invention.

Claims

1. A method for measuring the spatial scattering light field distribution, characterized in that It includes the following steps: S1: Without placing the sample to be measured or a reference sample close to ideal specular reflection at the test position, the light source is incident at a first angle, and the detector receives and measures the light radiation from different angles to obtain the light field distribution of the light source. S2: Place the sample to be measured at the test position, the light source is incident at a second angle, and the detector receives and measures the scattered light radiation passing through the sample to be measured from different angles to obtain the scattered light field distribution of the sample to be measured. S3: Use the light field distribution of the light source to perform decoupling operation on the scattered light field distribution of the sample to be measured to obtain the corrected scattered light field distribution of the sample to be measured.

2. The method for measuring the spatial scattering light field distribution according to claim 1, wherein Both the light field distribution of the light source and the scattered light field distribution of the sample to be measured are obtained by the method of spatial rotation scanning of the detector. Each scanning angle of the detector corresponds to a light field angle, and the sample to be measured is placed at the rotation center of the spatial angle scanning.

3. The method for measuring the spatial scattering light field distribution according to claim 1 or 2, characterized in that, In step S1, a first receiving aperture is set in front of the detector, and the spatial rotation scanning angle interval used is not greater than the angle subtended by the first receiving aperture with respect to the rotation center; in step S2, a second receiving aperture is set in front of the detector, and the size of the second receiving aperture is equal to or greater than the size of the first receiving aperture.

4. The spatial scattered light field distribution measurement method according to claim 3, characterized in that In step S1, decoupling calculation is performed on the measured light field distribution of the light source according to the spatial response distribution of the detector under the first receiving aperture and the scanning angle interval to obtain the corrected light field distribution of the light source; in step S2, it also includes decoupling calculation of the scattered light field distribution of the sample to be measured according to the spatial response distribution of the detector under the second receiving aperture and the scanning angle interval.

5. A method for measuring the spatial scattering light field distribution, characterized in that, Use an angular resolution imaging detection device with an imaging unit and a two-dimensional array detector to measure the spatial light field distribution. Each pixel or pixel region in the two-dimensional array detector corresponds to a spatial angle, and it specifically includes the following steps: S1: Without placing the sample to be measured or a reference sample close to ideal specular reflection at the test position, the light source is incident at a first angle, and use the angular resolution imaging detection device to obtain the light field distribution of the light source. S2: Place the sample to be measured at the test position, the light source is incident at a second angle, and use the angular resolution imaging detection device to receive and measure the scattered light radiation at different angles passing through the sample to be measured to obtain the scattered light field distribution of the sample to be measured. S3: Use the light field distribution of the light source to perform decoupling operation on the scattered light field distribution of the sample to be measured to obtain the corrected scattered light field distribution of the sample to be measured.

6. The method for measuring the spatial scattered light field distribution according to claim 5, wherein The imaging unit in the angular resolution imaging detection device is a microlens array, and the two-dimensional array detector is located on the imaging surface behind the microlens array; or the imaging unit in the angular resolution imaging detection device is a conoscopic lens, and the two-dimensional array detector is located on the imaging surface behind the conoscopic lens.

7. The method for measuring the spatial scattering light field distribution according to claim 5 or 6, characterized in that, The angular resolution imaging detection device faces the sample to be measured and rotates and scans in space with the sample to be measured as the rotation center. At each scanning angle, the angular resolution imaging detection device obtains the light field information at two or more light field angles.

8. The method for measuring the spatial scattering light field distribution according to claim 1 or 5, characterized in that The decoupling operation of using the light field distribution of the light source on the scattered light field distribution of the sample to be measured includes one or a combination of two or more of ray tracing and deconvolution.

9. The method for measuring the spatial scattering light field distribution according to claim 1 or 5, characterized in that, Before performing the decoupling operation on the scattered light field distribution of the sample to be measured using the light field distribution of the light source, the light field distribution of the light source is subjected to coordinate transformation according to the incident light angle to ensure that the decoupling operation is carried out in the same coordinate system.

10. The method for measuring the spatial scattering light field distribution according to claim 1 or 5, characterized in that The scattered light field distribution mentioned above is a function with two-dimensional angles as variables, and the two-dimensional angles are described as the angle between planes and the angle within a plane; in the process of performing the decoupling operation on the scattered light field distribution of the sample to be measured using the light field distribution of the light source, the decoupling operation is performed on the scattered light field distribution in each plane, and during the operation, the spatial scattered light field distribution function and the light field distribution function of the light source need to correspond one by one in terms of spatial angles.

11. The method for measuring the spatial scattering light field distribution according to claim 1 or 5, characterized in that The polarization state and / or the spot size and / or the relative spectral power distribution of the light source can be adjusted. Under different polarization states, spot sizes and relative spectral power distributions of the light source, the light field distribution of the light source is measured, and the decoupling calculation and correction are performed on the scattered light field distribution of the sample to be measured measured under the same conditions.

12. The method for measuring the spatial scattering light field distribution according to claim 1 or 5, characterized in that When measuring the sample to be measured, the light source is incident at two or more angles, the scattered light field distribution of the sample to be measured at each incident angle is measured respectively, and the decoupling operation is performed to obtain the corrected scattered light field distribution of the sample to be measured.

13. The method for measuring the spatial scattering light field distribution according to claim 1 or 5, characterized in that, In the process of performing the decoupling operation on the scattered light field distribution of the sample to be measured using the light field distribution of the light source, it includes using a fitting function to fit out the corrected scattered light field distribution function of the sample to be measured and performing deconvolution operation in an iterative manner; the fitting function is a Gaussian function or a Lorentz function or a cosine function or an ABg function or a Henyey-Greenstein function or a Gegenbauer function, or a combination of two or more of them.

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