Micro-LED array measurement method and system based on phase reconstruction

Abstract

The invention provides a Micro-LED array measurement method and system based on phase reconstruction, and relates to the technical field of micro-LED display, and the method comprises the steps: firstly obtaining a focal plane image and a plurality of out-of-focus plane images of a to-be-measured Micro-LED array, then carrying out the phase reconstruction of the images through a phase reconstruction model, obtaining the light field information of a light-emitting surface, and carrying out the measurement of the light field information of the light-emitting surface. The method comprises the following steps of: acquiring light field information, constructing amplitude-frequency distribution based on the light field information to obtain light intensity distribution evaluation diagrams of different light-emitting angles, and finally acquiring measurement information including the light-emitting angle, the luminous intensity ratio, the light intensity uniformity and the like based on a focal plane image and the light intensity distribution evaluation diagrams. According to the invention, the light emitting angle, the luminous intensity and the light intensity uniformity of the Micro-LED array can be rapidly, accurately and efficiently detected, the method is suitable for large-scale batch detection, the accuracy and the reliability of measurement are improved, and the method can be widely applied to measurement of other luminous semiconductor materials.

Description

Technical Field

[0001] The present invention relates to the technical field of micro light emitting diode (Micro-LED) displays, and particularly to a method and system for measuring a Micro-LED array based on phase reconstruction. Background Art

[0002] Micro-LED display technology uses light emitting diode (LED) devices with a size in the micrometer range as light emitting units, and integrates these tiny devices together through advanced semiconductor integration processes to achieve a super-high density display effect. However, traditional Micro-LED devices have a problem of spatial divergence during the light emitting process, resulting in relatively low light emitting efficiency, and the large divergence angle will cause light overlap and color crosstalk between adjacent Micro-LED devices, thus seriously affecting the display effect.

[0003] In order to improve the display effect of Micro-LEDs, collimation control of the emitted light has become a key link. However, after collimation control, it becomes particularly important to accurately measure the light emission angle of Micro-LEDs. At the same time, due to the difference in the uniformity of each light emitting point in the Micro-LED array, obtaining the light intensity information of each point and performing uniformity correction are also key steps to improve the display quality.

[0004] Currently, existing light emission angle measurement methods mainly rely on light intensity distribution testers or spectroradiometers. However, these devices are not only expensive and complex to operate, but also need to be used in rotation in cooperation with mechanical structures, so their application in the field of Micro-LED light emission angle measurement is severely limited. More importantly, due to the extremely small size of Micro-LEDs, the crosstalk problem between each sub-light emitting point during the measurement process is very prominent, which directly leads to a serious impact on the accuracy of the light emission angle and light emission uniformity measurement.

[0005] In summary, the current Micro-LED display technology faces many challenges in light emission angle and uniformity measurement. There is an urgent need for a new type of measurement method and system suitable for Micro-LED arrays to overcome the deficiencies of the existing technology and improve the overall performance and application range of Micro-LED display technology. Summary of the Invention

[0006] Therefore, the embodiments of the present invention provide a method and system for measuring a Micro-LED array based on phase reconstruction, which are used to solve the problems of inaccurate measurement of the light emission angle of Micro-LEDs, difficult evaluation of light emission uniformity, complex measurement process, and high cost in the existing technology.

[0007] To solve the above problems, an embodiment of the present invention provides a method for measuring a Micro-LED array based on phase reconstruction. The method is applied to a computer in a measurement system and includes: Obtain a focal plane image and multiple defocused plane images of the Micro-LED array to be measured; Use a phase reconstruction model to perform phase reconstruction on the focal plane image and the multiple defocused plane images to obtain the light field information of the light-emitting surface of the Micro-LED array to be measured; Based on the light field information of the light-emitting surface, construct the amplitude-frequency distribution of the light-emitting surface to obtain an evaluation map of the light intensity distribution at different light-emitting angles; Based on the focal plane image and the light intensity distribution evaluation map, obtain the measurement information of the Micro-LED array to be measured; wherein, the measurement information includes at least one of the light-emitting angle, the luminous intensity ratio, and the light intensity uniformity.

[0008] The beneficial effects of this technical solution are as follows: In the measurement method provided by the present invention, first, a focal plane image and multiple defocused plane images of the Micro-LED array to be measured are obtained; then, a phase reconstruction model is used for processing. The phase reconstruction model can deduce phase information from light intensity information, and then obtain the light field information of the light-emitting surface; based on the light field information, an amplitude-frequency distribution is constructed to obtain an evaluation map of the light intensity distribution at different light-emitting angles; using the focal plane image and the light intensity distribution evaluation map, the measurement information of the Micro-LED array to be measured (including at least one of the light-emitting angle, the luminous intensity ratio, and the light intensity uniformity) can be obtained; it can not only realize the detection of the Micro-LED array to be measured, but also quickly and accurately detect information such as the light-emitting angle, the luminous intensity ratio, and the light intensity uniformity of the Micro-LED array to be measured. Moreover, this measurement principle is not limited to Micro-LED arrays. For other light-emitting semiconductor materials, as long as the focal plane and defocused plane light intensity images can be obtained, this method can be applied for measurement, such as analyzing their light-emitting angles, luminous intensities, and uniformities, etc., providing a general solution for the detection of light-emitting semiconductor materials and can be widely applied to the measurement of other light-emitting semiconductor materials.

[0009] Preferably, the method for constructing the amplitude-frequency distribution of the light-emitting surface based on the light field information of the light-emitting surface is: Construct a coordinate system with the light-emitting surface of the Micro-LED array to be measured as the reference; wherein, it is set that the light-emitting surface is located in the xOy plane and the light propagates along the positive z-axis direction; Obtain the distribution information of the light emitted by the Micro-LED array to be measured in the spatial position under the coordinate system; Based on the first angle, the second angle, and the distribution information, obtain the amplitude-frequency distribution of the light-emitting surface; wherein, the first angle is the angle between the projection of the light propagation direction on the xOz plane and the positive direction of the z-axis, and the second angle is the angle between the projection of the light propagation direction on the yOz plane and the positive direction of the z-axis, and the light propagation direction is the propagation direction of the light emitted by the Micro-LED array to be measured.

[0010] Preferably, the obtaining of the amplitude-frequency distribution of the light-emitting surface based on the first angle, the second angle, and the distribution information includes: Obtain the distribution information at each of the spatial positions; Based on the first angle, the second angle, and each of the spatial positions, calculate the adjustment information at each of the spatial positions; Based on the product of the distribution information at each of the spatial positions and the corresponding adjustment information, obtain the amplitude-frequency distribution of the light-emitting surface.

[0011] Preferably, the calculating of the adjustment information at each of the spatial positions based on the first angle, the second angle, and each of the spatial positions includes: Process the first angle and the second angle respectively to obtain a first coefficient and a second coefficient; wherein, the first coefficient is related to the first angle and the wavelength of the light emitted by the Micro-LED array to be measured, and the second coefficient is related to the second angle and the wavelength of the light emitted by the Micro-LED array to be measured; Process the first coefficient and the second coefficient to obtain the adjustment information; wherein, the adjustment information is related to the first coefficient, the second coefficient, and the spatial position.

[0012] Preferably, the amplitude-frequency distribution of the light-emitting surface has the following calculation formula: ; In the formula, is the coordinate of the spatial position, is the distribution information at the spatial position (x, y), is the spatial frequency, is the wavelength, is the imaginary unit.

[0013] Preferably, the obtaining of the measurement information of the Micro-LED array to be measured based on the focal plane image and the light intensity distribution evaluation diagram includes: Obtain the gray value of each pixel in the focal plane image, and calculate the root mean square error of all the gray values; based on the root mean square error, determine the light intensity uniformity of the Micro-LED array to be measured; wherein, the smaller the value of the root mean square error, the better the light intensity uniformity of the Micro-LED array to be measured; And / or, process the light intensity distribution evaluation map to obtain the peak value of the light intensity and the angular range corresponding to the light of different intensities; based on the peak value of the light intensity and the angular range corresponding to the light of different intensities, obtain the light emitting angle of the Micro-LED array to be measured; And / or, process the light intensity distribution evaluation map to obtain the light intensity at different angles; calculate the sum of the light intensities at all angles within a preset angular range to obtain the local light intensity sum; calculate the ratio of the local light intensity sum to the total light intensity of the light emitted by the Micro-LED array to be measured to obtain the light emitting intensity ratio.

[0014] Preferably, the measurement system further includes a focusing lens device, a microscope objective lens, and an image sensor. Before performing phase reconstruction on the focal plane image and the multiple defocused plane images, the method further includes: Calibrate the focusing lens device, the microscope objective lens, and the image sensor; Based on the calibrated focusing lens device, microscope objective lens, and image sensor, establish an error correction model; wherein, the error correction model is used to correct the aberration introduced by the focusing lens device, microscope objective lens, and image sensor; Obtain the to-be-corrected focal plane image of the Micro-LED array to be measured and multiple to-be-corrected defocused plane images sent by the image sensor; Use the error correction model to correct the to-be-corrected focal plane image and each to-be-corrected defocused plane image respectively to obtain the corresponding focal plane image and the multiple defocused plane images.

[0015] Preferably, the measurement system further includes a focusing lens device, and the method further includes: Obtain the initial surface polynomial parameters of the focusing lens device and the initial model parameters of the phase reconstruction model; wherein, the initial surface polynomial parameters are the initial values of the surface polynomial parameters of the focusing lens device, and the initial model parameters are the initial values of the model parameters of the phase reconstruction model; Simulate and generate multiple defocused plane light intensity signal images under the initial surface polynomial parameters, and use the phase reconstruction model to perform phase reconstruction on the multiple defocused plane light intensity signal images based on the initial model parameters to obtain the reconstructed phase distribution data; Construct a loss function based on the reconstructed phase distribution data and the ideal phase distribution data at the corresponding positions, and jointly optimize the surface polynomial parameters of the focusing lens device and the model parameters of the phase reconstruction model through the backpropagation algorithm. Iteratively optimize until the loss function converges to obtain the optimized surface polynomial parameters and the optimized model parameters; Use the optimized surface polynomial parameters as the actual working parameters of the focusing lens device, and use the optimized model parameters as the final model parameters of the phase reconstruction model; Preferably, the calculation formula of the loss function is as follows: ; where, represents the root mean square error, represents the total number of pixels in the vertical direction of the defocused plane light intensity signal image; represents the total number of pixels in the horizontal direction of the defocused plane light intensity signal image; is the reconstructed phase value at the pixel position ; is the ideal phase value at the pixel position ;

[0016] The beneficial effects of this technical solution are as follows: On the one hand, calibrate the focusing lens device, the microscope objective lens and the image sensor before measurement, and establish an error correction model to correct the aberration. On the other hand, by obtaining the initial surface polynomial parameters of the focusing lens device and the initial model parameters of the phase reconstruction model, simulate the defocused plane light intensity signal image, perform phase reconstruction to obtain the reconstructed phase distribution data, construct a loss function, and use the backpropagation algorithm to jointly optimize the surface polynomial parameters of the focusing lens device and the model parameters of the phase reconstruction model, and iterate until the loss function converges to obtain the optimized parameters. These measures effectively reduce the measurement error and improve the accuracy and reliability of the measurement.

[0017] The embodiment of the present invention also provides a measurement system, which includes a computer, and the computer is used to implement the above-mentioned Micro-LED array measurement method based on phase reconstruction.

[0018] Preferably, the measurement system further includes: A first displacement platform for moving the Micro-LED array to be measured in the x-axis direction and the y-axis direction; A stage is arranged on the first displacement platform for carrying and adjusting the pitch angle of the light-emitting surface of the Micro-LED array to be measured, so that the light-emitting surface of the Micro-LED array is perpendicular to the optical axis of the measurement system; A focusing lens device is arranged on the outgoing light path of the to-be-tested Micro-LED array for separating and converging the beam crosstalk generated by adjacent light-emitting units in the to-be-tested Micro-LED array; A microscope objective lens is arranged on the outgoing light path of the focusing lens device for magnifying the beam converged by the focusing lens device; An image sensor is arranged on the outgoing light path of the microscope objective lens and is mechanically connected to the microscope objective lens for receiving and recording the light intensity information magnified by the microscope objective lens to obtain the focal plane image and the multiple defocused plane images; A second displacement platform is used for adjusting the height of the microscope objective lens and the image sensor in the z-axis direction. The second displacement platform is connected to both sides of the image sensor through an adapter plate.

[0019] Preferably, the accuracy of the first displacement platform reaches ±10 μm, the stroke of the first displacement platform is greater than the size of the to-be-tested Micro-LED array, and the aperture of the focusing lens device is more than 3 times the size of the to-be-tested Micro-LED array; the accuracy of the second displacement platform reaches ±1 μm, and the stroke of the second displacement platform is greater than 3 times the focal depth of the microscope objective lens; And / or, the numerical aperture of the microscope objective lens is greater than the numerical aperture of the focusing lens device.

[0020] The beneficial effects of this technical solution are as follows: The measurement system provided by the present invention includes a first displacement platform, a stage, a focusing lens device, a microscope objective lens, an image sensor, and a second displacement platform. The first displacement platform has an accuracy of ±10 μm and a stroke greater than the size of the to-be-tested Micro-LED array, and can accurately move the to-be-tested Micro-LED array; the stage can adjust the pitch angle of the light-emitting surface of the to-be-tested Micro-LED array to be perpendicular to the optical axis; the aperture of the focusing lens device is more than 3 times the size of the to-be-tested Micro-LED array, and can separate and converge the beam crosstalk of adjacent light-emitting units; the microscope objective lens magnifies the converged beam; the image sensor receives and records the light intensity information; the second displacement platform has an accuracy of ±1 μm and a stroke greater than 3 times the focal depth of the microscope objective lens, and accurately adjusts the height of the microscope objective lens and the image sensor to obtain the focal plane and defocused plane images. The entire system is designed compactly and reasonably, can realize an automated measurement process, is suitable for batch detection of large-scale Micro-LED arrays, and greatly improves the detection efficiency. Description of the Drawings

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly describe the drawings required in the embodiments. By referring to the drawings, the features and advantages of the present invention will be more clearly understood. The drawings are schematic and should not be construed as imposing any limitations on the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts. Among them: Figure 1 It is a flowchart of a measurement method for a Micro-LED array based on phase reconstruction provided by the present invention; Figure 2 It is a schematic structural diagram of a measurement system provided by the present invention.

[0022] Reference numerals in the specification drawings: 1. First displacement platform; 2. Carriage; 3. Focusing lens device; 4. Microscope objective; 5. Image sensor; 6. Second displacement platform; 7. Computer. Specific embodiments

[0023] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are some but not all of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0024] Embodiment 1:

[0025] To solve the problems of inaccurate measurement of the light-emitting angle of Micro-LEDs, difficult evaluation of light-emitting uniformity, and complex and costly measurement process in the prior art. As Figure 1 shown, the present invention proposes a measurement method for a Micro-LED array based on phase reconstruction, including: S1: Obtain the focal plane image and multiple defocused plane images of the Micro-LED array to be measured.

[0026] The Micro-LED array to be measured is the Micro-LED array that needs to be tested. In optical measurement, it is relatively difficult to directly obtain the phase information of the light field, while the light intensity information is relatively easy to measure. For the Micro-LED array to be measured, the light intensity information of its focal plane image and multiple defocused plane images can be obtained. The focal plane image and the defocused plane image contain rich information (light intensity information) about the light emitted by the Micro-LED array to be measured, and these images are the key data basis for phase reconstruction using the phase reconstruction model.

[0027] S2: Use the phase reconstruction model to perform phase reconstruction on the focal plane image and multiple defocused plane images to obtain the light field information of the light-emitting surface of the Micro-LED array to be measured.

[0028] To deeply understand the light-emitting characteristics of the Micro-LED array to be measured, the phase information of the light field is crucial because phase plays a key role in phenomena such as light interference and diffraction, determining the propagation and interaction characteristics of light. Therefore, it is necessary to use the phase reconstruction model to deduce the phase information from the known light intensity information, and then obtain the complete light field information. Based on the focal plane image and all defocused plane images, the phase reconstruction model can obtain the light field information of the light-emitting surface, providing support for subsequent analysis.

[0029] Specifically, the algorithms adopted by common phase reconstruction models include the Gerchberg-Saxton iterative algorithm, the transport of intensity equation, or deep learning algorithms, etc. The Gerchberg-Saxton iterative algorithm performs iterative calculations based on Fourier transform and constraint conditions. By repeatedly transforming between the spatial domain and the frequency domain, it gradually approaches the true phase distribution. The transport of intensity equation is based on the relationship between the light intensity change and phase during light propagation, and restores the phase by solving partial differential equations. Deep learning algorithms use a large amount of data to train the model, enabling the model to learn the complex mapping relationship between light intensity information and phase information, thereby realizing phase reconstruction. In practical applications, an appropriate algorithm model can be selected according to factors such as measurement requirements, data characteristics, and computing resources.

[0030] Furthermore, input the light intensity information of the obtained focal plane image and all defocused plane images into the selected phase reconstruction algorithm model. Based on its own principles and calculation logic, the algorithm model analyzes and processes this light intensity information. Taking the Gerchberg-Saxton iterative algorithm as an example, first perform a preliminary Fourier transform on the light intensity information to obtain an initial phase estimate, and then, according to the constraint conditions of the focal plane and defocused plane, continuously iterate and update the phase estimate between the spatial domain and the frequency domain until a certain convergence condition is met to obtain relatively accurate phase information. Combining the phase information and the known light intensity information, the light field information of the light-emitting surface of the Micro-LED array to be measured can be constructed.

[0031] The light field information of the light-emitting surface includes the amplitude and phase distributions of light, which is crucial for comprehensively understanding the light-emitting characteristics of the Micro-LED array. Based on the light field information, the amplitude-frequency distribution data of the light-emitting surface can be further constructed to obtain the light intensity distribution evaluation diagram at different light-emitting angles.

[0032] S3: Based on the light field information of the light-emitting surface, construct the amplitude-frequency distribution data of the light-emitting surface to obtain the light intensity distribution evaluation diagram at different light-emitting angles.

[0033] S4: Based on the focal plane image and the light intensity distribution evaluation diagram, obtain the measurement information of the Micro-LED array to be measured. The measurement information of the Micro-LED array to be measured includes at least one of the light-emitting angle, the luminous intensity ratio, and the light intensity uniformity.

[0034] As can be seen from the above technical solution, the present invention proposes a measurement method for a Micro-LED array based on phase reconstruction. First, obtain the focal plane image and multiple defocused plane images of the Micro-LED array to be measured. This step can quickly obtain basic data. Then, use the phase reconstruction model to process these images to obtain the light field information of the light-emitting surface. This process uses advanced algorithms and can effectively improve the accuracy and reliability of the measurement. Next, based on the light field information, construct amplitude-frequency distribution data to obtain the light intensity distribution evaluation diagram at different light-emitting angles, thereby accurately presenting the light-emitting characteristics. Finally, combine the focal plane image and the light intensity distribution evaluation diagram to obtain measurement information such as the light-emitting angle, the luminous intensity ratio, and the light intensity uniformity, realizing a comprehensive evaluation of the Micro-LED array to be measured. This method is not only applicable to the batch detection of large-scale Micro-LED arrays, greatly improving the detection efficiency, but also can be widely applied to the measurement of other light-emitting semiconductor materials, providing an efficient and stable batch product detection solution for the field of automatic detection of light-emitting semiconductor materials, and effectively solving the problems of inaccurate measurement, difficult evaluation, complex process, and high cost in the prior art.

[0035] Further, the method for constructing the amplitude-frequency distribution data of the light-emitting surface based on the light field information of the light-emitting surface includes: S31: Construct a coordinate system with the light-emitting surface of the Micro-LED array as the reference.

[0036] It is assumed that the light-emitting surface is located in the xOy plane, the light propagates along the positive direction of the z-axis, and the light emitted by the Micro-LED array can be parallel or non-parallel to the z-axis.

[0037] S32: Obtain the distribution information of the light emitted by the Micro-LED array to be measured in the spatial position under the coordinate system.

[0038] S34: Based on the first included angle, the second included angle, and the distribution information, obtain the amplitude-frequency distribution data of the light-emitting surface.

[0039] The first included angle is the included angle between the projection of the light propagation direction on the xOz plane and the positive direction of the z-axis, which is ; the second included angle is the included angle between the projection of the light propagation direction on the yOz plane and the positive direction of the z-axis, which is .

[0040] Further, obtaining the amplitude-frequency distribution data of the light-emitting surface based on the first included angle, the second included angle, and the distribution information includes: S341: Obtain the distribution information at each spatial position.

[0041] S342: Calculate the adjustment information at each spatial position based on the first angle, the second angle, and each spatial position.

[0042] The following method can be adopted: (A1) Process the first angle and the second angle respectively to obtain the first coefficient and the second coefficient.

[0043] The first coefficient is related to the first angle and the wavelength of the light emitted by the Micro-LED array to be measured, and the second coefficient is related to the second angle and the wavelength of the light emitted by the Micro-LED array to be measured.

[0044] (A2) Process the first coefficient and the second coefficient to obtain the adjustment information.

[0045] The adjustment information is related to the first coefficient, the second coefficient, and the spatial position; specifically, the calculation formula of the adjustment information F(x, y) is as follows: ; Wherein, is the coordinate of the spatial position, is the wavelength, is the imaginary unit, is the first coefficient, is the second coefficient, is the spatial frequency.

[0046] S343: Obtain the amplitude-frequency distribution of the light-emitting surface based on the product of the distribution information at each spatial position and the corresponding adjustment information.

[0047] Based on the product of the distribution information at each spatial position and the corresponding adjustment information, obtain the amplitude-frequency distribution of the light-emitting surface, so as to convert the spatial distribution characteristics of the light field to the frequency domain for analysis. Specifically, the amplitude-frequency distribution of the light-emitting surface has the following calculation formula: ; In the formula, is the coordinate of the spatial position, is the spatial position at which the distribution information is located, is the adjustment information, is the wavelength, is the imaginary unit.

[0048] Furthermore, the amplitude-frequency distribution reflects the distribution of different spatial frequency components in the light field. Since there is a corresponding relationship between the spatial frequency and the light-emitting angle, an evaluation diagram of the light intensity distribution at different light-emitting angles can be constructed.

[0049] In one embodiment, the measurement information of the Micro-LED array to be measured includes light intensity uniformity, and the evaluation method of light intensity uniformity includes: S41a: Obtain the gray value of each pixel in the focal plane image, and calculate the root mean square error of the gray values.

[0050] S42a: Based on the root mean square error, determine the light intensity uniformity of the Micro-LED array to be measured.

[0051] The smaller the value of the root mean square error, the better the light intensity uniformity of the Micro-LED array to be measured. For example, multiple levels can be set for the light intensity uniformity of the Micro-LED array to be measured, and each level corresponds to a numerical range of the root mean square error, as shown in Table 1 below: Table 1 Relationship between the numerical range of the root mean square error and the level of light intensity uniformity Numerical range of root mean square error Level of light intensity uniformity [R1, R2) Very uniform [R2, R3) Generally uniform [R3, R4) Non-uniform It should be noted that if there are points with too large a difference in gray values, the position of the corresponding light-emitting point can be located by finding the coordinates of the point, and the uniformity can be corrected by adjusting the voltage of the light-emitting point.

[0052] In one embodiment, the measurement information of the Micro-LED array to be measured includes the light-emitting angle. Since the light intensity distribution evaluation map reflects the light intensity distribution at different light-emitting angles, in order to obtain the light-emitting angle, the methods that can be adopted include: S41b: Process the light intensity distribution evaluation map to obtain the peak value of the light intensity and the angle range corresponding to the light of different intensities.

[0053] S42b: Based on the peak value of the light intensity and the angle range corresponding to the light of different intensities, obtain the light-emitting angle of the Micro-LED array to be measured.

[0054] The specific implementation involves processing the evaluation map data, such as finding the extreme points of the light intensity distribution curve, determining the corresponding angle as the main light-emitting angle, or determining the angle range of the light-emitting angle according to the set light intensity threshold, etc., which is similar to the related art and will not be elaborated here.

[0055] In one embodiment, the measurement information of the Micro-LED array to be measured includes the luminous intensity ratio, and the obtaining method of the luminous intensity ratio includes: S41c: Process the light intensity distribution evaluation map to obtain the light intensity at different angles; calculate the sum of the light intensities at all angles within the preset angle range to obtain the local light intensity sum.

[0056] S42c: Calculate the ratio of the local light intensity sum to the total light intensity of the light emitted by the Micro-LED array to be measured to obtain the luminous intensity ratio.

[0057] When calculating the total light intensity, it is necessary to integrate or sum the light intensities corresponding to all angles in the light intensity distribution evaluation diagram. For example, assume that the outgoing light angle range is divided into k (k≥2) sub-intervals , first calculate the light intensity within each sub-interval , the total light intensity , then for a certain sub-interval , the proportion of the luminous intensity is .

[0058] In summary, the measurement method provided by the present invention can quickly and at low cost detect the outgoing light angle, the proportion of luminous intensity, the light intensity uniformity of the light-emitting points, etc. of the Micro-LED array to be measured after collimation regulation. Through the test method provided by the present invention, it is possible to provide efficient and stable batch product detection in the field of automatic detection of light-emitting semiconductor materials.

[0059] Embodiment 2:

[0060] As Figure 2 shown, the present invention provides a measurement system, which includes a computer 7 for implementing the above-mentioned Micro-LED array measurement method based on phase reconstruction. In addition, the measurement system further includes a first displacement platform 1, a stage 2, a focusing lens device 3, a microscope objective 4, an image sensor 5, and a second displacement platform 6.

[0061] The first displacement platform 1 is used to move the Micro-LED array to be measured in the x-axis direction and the y-axis direction. Specifically, in this embodiment, the accuracy requirement of the first displacement platform 1 reaches ±10μm, and the stroke needs to be greater than the size of the Micro-LED array to be measured; this is to ensure that during the measurement process, the position of the Micro-LED array to be measured can be accurately controlled, and all parts of the Micro-LED array to be measured can be moved to the appropriate positions in the measurement optical path to obtain accurate and comprehensive measurement data.

[0062] The stage 2 is arranged on the first displacement platform 1 and is used to carry and adjust the pitch angle of the outgoing light surface of the Micro-LED array to be measured, so that the outgoing light surface of the Micro-LED array is perpendicular to the optical axis of the measurement system. Specifically, the three-point adjustment method can be used to adjust the pitch angle of the outgoing light surface of the Micro-LED array to be measured, but it is not limited to this.

[0063] The focusing lens device 3 is disposed on the outgoing light path of the Micro-LED array to be measured, and is used to separate and converge the beam crosstalk generated by adjacent light-emitting units in the Micro-LED array to be measured. Specifically, in this embodiment, the aperture of the focusing lens device 3 is more than three times the size of the Micro-LED array to be measured, so as to better collect and process the light emitted by the Micro-LED array to be measured, reduce light loss and edge effects, and improve imaging quality and measurement accuracy.

[0064] The microscope objective 4 is disposed on the outgoing light path of the focusing lens device 3 and is used to magnify the beam converged by the focusing lens device 3.

[0065] The image sensor 5 is disposed on the outgoing light path of the microscope objective 4 and is mechanically connected to the microscope objective 4, and is used to receive and record the light intensity information magnified by the microscope objective 4 to obtain a focal plane image and a plurality of defocused plane images.

[0066] Furthermore, in this embodiment, the numerical aperture of the microscope objective 4 is greater than the numerical aperture of the focusing lens device 3. The numerical aperture is an important parameter for measuring the light collection ability of an optical system. The larger the numerical aperture, the more light the optical system can collect, the higher the resolution, and the better the imaging quality. In this measurement system, the microscope objective 4 needs to further magnify and image the light processed by the focusing lens device 3 so that the image sensor 5 can accurately record the light intensity information for subsequent operations such as phase reconstruction and light field information analysis. If the numerical aperture of the microscope objective 4 is smaller than that of the focusing lens device 3, the light converged by the focusing lens device 3 may not be fully received and processed by the microscope objective 4, resulting in a decrease in imaging quality, loss or distortion of light field information, and further affecting the accurate measurement of parameters such as the light output angle and uniformity of the Micro-LED array.

[0067] The second displacement platform 6 is used to adjust the height of the microscope objective 4 and the image sensor 5 in the z-axis direction, and the second displacement platform 6 is connected to both sides of the image sensor 5 through an adapter plate. Specifically, in this embodiment, the accuracy requirement of the second displacement platform 6 reaches ±1 μm, and the stroke is greater than three times the focal depth of the microscope objective 4. The high-precision second displacement platform 6 helps to more accurately adjust the relative position of the microscope objective 4 and the image sensor 5 when obtaining the focal plane image and the defocused plane images, so as to obtain more accurate light intensity information and provide a reliable data basis for subsequent phase reconstruction and performance analysis.

[0068] Furthermore, obtaining the focal plane image and a plurality of defocused plane images of the Micro-LED array to be measured by using the measurement system of the present invention is an important basic link in the measurement process, and its operation process includes the following steps: (1) First, install the Micro-LED array to be measured on the stage 2, and precisely adjust the pitch angle of its light-emitting surface so that the light-emitting surface of the Micro-LED array to be measured is strictly perpendicular to the optical axis of the measurement system. This can ensure that the light emitted by the Micro-LED array to be measured can enter the subsequent optical components in the correct direction. Subsequently, light up the Micro-LED array to be measured, and precisely move it to the measurement position with the help of the first displacement platform 1.

[0069] (2) The focusing lens device 3 focuses the light beam emitted by the Micro-LED array to be measured, separates and converges the beam crosstalk generated by adjacent light-emitting units, facilitating subsequent processing. The light beam emitted by the Micro-LED array to be measured then enters the microscope objective 4, and the microscope objective 4 magnifies the converged light beam.

[0070] (3) Use the second displacement platform 6 to move the image sensor 5 so that the image sensor 5 is located at the best focal plane position converged by the microscope objective 4; use the image sensor 5 to receive and record the light intensity information magnified by the microscope objective 4. At this time, the obtained image is the focal plane image.

[0071] (4) Adjust the height of the microscope objective 4 and the image sensor 5 in the z-axis direction through the second displacement platform 6, change their relative positions, and make the image sensor 5 in different defocus positions. At each defocus position, the image sensor 5 receives and records the corresponding light intensity information, so that multiple defocus plane images can be obtained.

[0072] In addition, in order to further improve the measurement accuracy, the method of the present invention can pre-calibrate the focusing lens device 3, the microscope objective 4, and the camera image sensor 5 before performing phase reconstruction on the focal plane image and multiple defocus plane images, so as to better analyze and correct the errors that they may introduce. The specific steps are as follows: (B1) Calibrate the focusing lens device 3, the microscope objective 4, and the image sensor 5.

[0073] (B2) Based on the calibrated focusing lens device 3, microscope objective 4, and image sensor 5, establish an error correction model.

[0074] The error correction model is used to correct the aberrations introduced by the focusing lens device 3, the microscope objective 4, and the image sensor 5.

[0075] (B3) Obtain the to-be-corrected focal plane image of the Micro-LED array to be measured and multiple to-be-corrected defocus plane images sent by the image sensor 5.

[0076] (B4) Use the error correction model to correct the to-be-corrected focal plane image and each to-be-corrected defocus plane image respectively, and obtain the corresponding focal plane image and multiple defocus plane images.

[0077] In addition to the above method of pre-calibration and post-correction, the present invention can also take into account the aberration during the design process of the focusing lens device 3. By continuously optimizing the parameters of the focusing lens device 3 and the parameters of the phase reconstruction model, the difference between the finally obtained reconstructed phase and the theoretical phase can be minimized. Specifically, by constructing a root mean square error loss function to jointly optimize the parameters of the focusing lens device 3 and the parameters of the phase reconstruction model, the best combination of device parameters and model parameters is found, which specifically includes the following steps: (C1)Obtain the initial surface polynomial parameters of the focusing lens device 3 and the initial model parameters of the phase reconstruction model.

[0078] The initial surface polynomial parameters are the initial values of the surface polynomial parameters of the focusing lens device 3, and the initial model parameters are the initial values of the model parameters of the phase reconstruction model.

[0079] The surface of the focusing lens device 3 is not a simple spherical or planar surface. In order to accurately describe its complex shape, polynomials are often used for fitting. The surface polynomial is a mathematical expression that approximates the actual lens surface through the combination of different terms. The coefficients of each term are the so-called surface polynomial parameters. Taking the commonly used Zernike polynomials as an example, they are widely used in the optical field to describe the surface of optical elements. The Zernike polynomials consist of a series of functions with specific mathematical forms. By adjusting the coefficients of each term in the polynomial, the surface of the focusing lens device 3 can be accurately described. These coefficients are the device parameters. Different parameter values correspond to different surfaces, and the surface will affect the refraction, focusing, etc. of light by the lens, and thus affect the performance of the entire measurement system, such as the convergence effect of the light beam and the clarity of imaging.

[0080] (C2)Simulate and generate multiple defocused surface light intensity signal images under the initial surface polynomial parameters, and use the phase reconstruction model to perform phase reconstruction on the multiple defocused surface light intensity signal images based on the initial model parameters to obtain the reconstructed phase distribution data.

[0081] (C3)Construct a loss function based on the reconstructed phase distribution data and the ideal phase distribution data at the corresponding positions. Through the backpropagation algorithm, jointly optimize the surface polynomial parameters of the focusing lens device 3 and the model parameters of the phase reconstruction model, and iteratively optimize until the loss function converges to obtain the optimized surface polynomial parameters and the optimized model parameters.

[0082] The ideal phase distribution is generated by simulating the physical optics model, and the calculation of the loss function is based on the phase distribution data in the form of a two-dimensional matrix.

[0083] Further, the loss function is used to quantify the deviation between the reconstructed phase and the ideal phase, and guide the joint optimization of the parameters of the focusing lens device 3 and the model parameters of the phase reconstruction model. The calculation formula of the loss function is as follows: ; wherein, represents the root mean square error, represents the total number of pixels in the vertical direction of the defocused plane light intensity signal image; represents the total number of pixels in the horizontal direction of the defocused plane light intensity signal image; is the pixel position of the reconstructed phase value; is the pixel position of the ideal phase value.

[0084] (C4) Use the optimized surface polynomial parameters as the actual working parameters of the focusing lens device 3, and use the optimized model parameters as the final model parameters of the phase reconstruction model.

[0085] By minimizing the loss function, the present invention can find the best combination of device parameters (i.e., the actual working parameters of the focusing lens device 3) and model parameters (i.e., the final model parameters of the phase reconstruction model), so as to optimize the entire measurement system and improve the accuracy of measuring the light output angle and uniformity of the Micro-LED array to be measured.

[0086] The technical solution provided by the present invention has the following advantages: (1) Accurately measure multiple parameters: The measurement method provided by the present invention first obtains the focal plane image and multiple defocused plane images of the Micro-LED array to be measured, and then uses the phase reconstruction model for processing. It can deduce the phase information from the light intensity information, and then obtain the light field information of the light output surface. Based on the light field information, an amplitude-frequency distribution is constructed to obtain an evaluation diagram of the light intensity distribution at different light output angles. Calculate the root mean square error of the pixel gray value through the focal plane image to evaluate the light intensity uniformity; obtain the light intensity peak value from the evaluation diagram of the light intensity distribution, determine the light output angle from the angle range corresponding to different intensities of light; calculate the ratio of the light intensity sum in the preset angle range to the total light intensity to obtain the light intensity ratio. These steps are closely linked, and can not only realize the detection of the Micro-LED array to be measured, but also quickly and accurately detect information such as the light output angle, light intensity ratio and light intensity uniformity of the Micro-LED array to be measured.

[0087] (2) Suitable for batch detection: The measurement system provided by the present invention includes a first displacement platform, a stage, a focusing lens device, a microscope objective, an image sensor, and a second displacement platform. The first displacement platform has an accuracy of ±10 μm and a travel greater than the size of the Micro-LED array to be measured, and can accurately move the array; the stage can adjust the pitch angle of the light-emitting surface of the array to be perpendicular to the optical axis; the aperture of the focusing lens device is more than 3 times the size of the array, and can separate and converge the beam crosstalk of adjacent light-emitting units; the microscope objective magnifies the converged beam; the image sensor receives and records the light intensity information; the second displacement platform has an accuracy of ±1 μm and a travel greater than 3 times the focal depth of the microscope objective, and accurately adjusts the height between the microscope objective and the image sensor to obtain the focal plane and defocused plane images. The entire system is designed compactly and reasonably, can realize an automated measurement process, is suitable for batch detection of large-scale Micro-LED arrays, and greatly improves the detection efficiency.

[0088] (3) Improve measurement accuracy and reliability: On the one hand, calibrate the focusing lens device, microscope objective, and image sensor before measurement, and establish an error correction model to correct aberration. On the other hand, by obtaining the initial surface polynomial parameters of the focusing lens device and the initial model parameters of the phase reconstruction model, simulate and generate the defocused plane light intensity signal image, perform phase reconstruction to obtain the reconstructed phase distribution data, construct a loss function, and use the backpropagation algorithm to jointly optimize the surface polynomial parameters of the focusing lens device and the model parameters of the phase reconstruction model, and iterate until the loss function converges to obtain the optimized parameters. These measures effectively reduce measurement errors and improve the accuracy and reliability of measurement.

[0089] (4) Wide range of applications: The core of the measurement method based on phase reconstruction in the present invention is to obtain the optical field phase information from the light intensity information, and then analyze the light-emitting characteristics. This measurement principle is not limited to Micro-LED arrays. For other light-emitting semiconductor materials, as long as the focal plane and defocused plane light intensity images can be obtained, this method can be applied for measurement, such as analyzing the light-emitting angle, light-emitting intensity, and uniformity, etc., providing a general solution for the detection of light-emitting semiconductor materials, and can be widely applied to the measurement of other light-emitting semiconductor materials.

[0090] Those skilled in the art should understand that the embodiments of the present application can be provided as a method, a system, or a computer program product. Therefore, the present application can take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present application can take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0091] This application is described with reference to the flowcharts and / or block diagrams of methods, apparatuses (systems), and computer program products according to embodiments of the present application. It should be understood that each flow and / or block in the flowchart and / or block diagram, as well as the combination of flows and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to the processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing devices to generate a machine, such that the instructions executed by the processor of the computer or other programmable data processing devices generate a means for implementing the functions specified in the Figure 1 one or more flows and / or blocks Figure 1 one or more blocks.

[0092] These computer program instructions can also be stored in a computer-readable memory that can direct a computer or other programmable data processing device to work in a specific manner, such that the instructions stored in the computer-readable memory generate a manufactured article including an instruction means that implements the functions specified in the Figure 1 one or more flows and / or blocks Figure 1 one or more blocks. These computer program instructions can also be loaded onto a computer or other programmable data processing device, such that a series of operation steps are executed on the computer or other programmable device to generate a computer-implemented process, and thus the instructions executed on the computer or other programmable device provide steps for implementing the functions specified in the Figure 1 one or more flows and / or blocks Figure 1 one or more blocks.

[0093] Obviously, the above embodiments are merely examples for clear illustration and are not limitations on the implementation manners. For those of ordinary skill in the art, other different forms of changes or variations can be made based on the above description. It is not necessary and impossible to enumerate all the implementation manners here. And the obvious changes or variations derived therefrom are still within the protection scope of the present invention.

Claims

1. A measurement method for Micro-LED arrays based on phase reconstruction, characterized in that, A computer applied to a measurement system, the method comprising: Obtaining a focal plane image and a plurality of defocused plane images of the Micro-LED array to be measured; Performing phase reconstruction on the focal plane image and the plurality of defocused plane images by using a phase reconstruction model to obtain the light field information of the light-emitting surface of the Micro-LED array to be measured; Based on the light field information of the light-emitting surface, constructing the amplitude-frequency distribution of the light-emitting surface to obtain an intensity distribution evaluation map at different light-emitting angles; Based on the focal plane image and the intensity distribution evaluation map, obtaining the measurement information of the Micro-LED array to be measured; wherein, the measurement information includes at least one of a light-emitting angle, a luminous intensity ratio, and a light intensity uniformity.

2. The method for measuring a Micro-LED array based on phase reconstruction according to claim 1, wherein The method for constructing the amplitude-frequency distribution of the light-emitting surface based on the light field information of the light-emitting surface is: Constructing a coordinate system with the light-emitting surface of the Micro-LED array to be measured as a reference; wherein, it is set that the light-emitting surface is located in the xOy plane and the light propagates along the positive z-axis direction; Obtaining the distribution information of the light emitted by the Micro-LED array to be measured in the spatial position in the coordinate system; Based on the first included angle, the second included angle, and the distribution information, obtain the amplitude-frequency distribution of the light-emitting surface; wherein, the first included angle is the included angle between the projection of the light propagation direction on the xOz plane and the positive direction of the z-axis, and the second included angle is the included angle between the projection of the light propagation direction on the yOz plane and the positive direction of the z-axis, and the light propagation direction is the propagation direction of the light emitted by the Micro-LED array to be measured.

3. The method for measuring a Micro-LED array based on phase reconstruction according to claim 2, wherein The obtaining the amplitude-frequency distribution of the light-emitting surface based on the first included angle, the second included angle, and the distribution information includes: Obtaining the distribution information at each of the spatial positions; Calculating the adjustment information at each of the spatial positions based on the first included angle, the second included angle, and each of the spatial positions; Based on the product of the distribution information at each of the spatial positions and the corresponding adjustment information, obtaining the amplitude-frequency distribution of the light-emitting surface.

4. The method for measuring a Micro-LED array based on phase reconstruction according to claim 3, wherein The calculating the adjustment information at each of the spatial positions based on the first included angle, the second included angle, and each of the spatial positions includes: Processing the first included angle and the second included angle respectively to obtain a first coefficient and a second coefficient; wherein, the first coefficient is related to the first included angle and the wavelength of the light emitted by the Micro-LED array to be measured, and the second coefficient is related to the second included angle and the wavelength of the light emitted by the Micro-LED array to be measured; Processing the first coefficient and the second coefficient to obtain the adjustment information; wherein, the adjustment information is related to the first coefficient, the second coefficient, and the spatial position.

5. The method for measuring a Micro-LED array based on phase reconstruction according to claim 4, wherein The amplitude-frequency distribution of the light-emitting surface The calculation formula is as follows: ； In the formula, is the coordinate of the spatial position, is the distribution information at the spatial position (x, y), is the spatial frequency, is the wavelength, is the imaginary unit.

6. The method for measuring a Micro-LED array based on phase reconstruction according to claim 1, wherein The obtaining the measurement information of the Micro-LED array to be measured based on the focal plane image and the intensity distribution evaluation map includes: Obtaining the gray value of each pixel in the focal plane image, and calculating the root mean square error of all the gray values; based on the root mean square error, determining the light intensity uniformity of the Micro-LED array to be measured; wherein, the smaller the value of the root mean square error, the better the light intensity uniformity of the Micro-LED array to be measured; And / or, processing the intensity distribution evaluation map to obtain the peak value of the light intensity and the angular range corresponding to the light of different intensities; based on the peak value of the light intensity and the angular range corresponding to the light of different intensities, obtaining the light-emitting angle of the Micro-LED array to be measured; And / or, process the light intensity distribution evaluation diagram to obtain the light intensity at different angles; calculate the sum of the light intensities at all angles within a preset angle range to obtain the sum of local light intensities; calculate the ratio of the sum of local light intensities to the total light intensity of the light emitted by the Micro-LED array to be measured to obtain the proportion of the luminous intensity.

7. The method for measuring a Micro-LED array based on phase reconstruction according to claim 1, wherein, The measurement system further includes a focusing lens device, a microscope objective lens, and an image sensor. Before performing phase reconstruction on the focal plane image and the multiple defocused plane images, the method further includes: Calibrate the focusing lens device, the microscope objective lens, and the image sensor; Based on the calibrated focusing lens device, microscope objective lens, and image sensor, establish an error correction model; wherein, the error correction model is used to correct the aberration introduced by the focusing lens device, microscope objective lens, and image sensor; Obtain the to-be-corrected focal plane image and multiple to-be-corrected defocused plane images of the Micro-LED array to be measured sent by the image sensor; Use the error correction model to correct the to-be-corrected focal plane image and each to-be-corrected defocused plane image respectively to obtain the corresponding focal plane image and the multiple defocused plane images.

8. The method for measuring a Micro-LED array based on phase reconstruction according to claim 1, wherein The measurement system further includes a focusing lens device, and the method further includes: Obtain the initial surface shape polynomial parameters of the focusing lens device and the initial model parameters of the phase reconstruction model; wherein, the initial surface shape polynomial parameters are the initial values of the surface shape polynomial parameters of the focusing lens device, and the initial model parameters are the initial values of the model parameters of the phase reconstruction model; Simulate and generate multiple defocused plane light intensity signal images under the initial surface shape polynomial parameters, and use the phase reconstruction model to perform phase reconstruction on the multiple defocused plane light intensity signal images based on the initial model parameters to obtain reconstructed phase distribution data; Construct a loss function based on the reconstructed phase distribution data and the ideal phase distribution data at corresponding positions, and jointly optimize the surface shape polynomial parameters of the focusing lens device and the model parameters of the phase reconstruction model through the backpropagation algorithm, and iterate and optimize until the loss function converges to obtain the optimized surface shape polynomial parameters and the optimized model parameters; Use the optimized surface shape polynomial parameters as the actual working parameters of the focusing lens device, and use the optimized model parameters as the final model parameters of the phase reconstruction model.

9. The method for measuring a Micro-LED array based on phase reconstruction according to claim 8, wherein, The calculation formula of the loss function is as follows: ； Among them, represents the root mean square error, represents the total number of pixels of the defocused plane light intensity signal image in the vertical direction; represents the total number of pixels of the defocused plane light intensity signal image in the horizontal direction; is the reconstructed phase value at pixel position ; is the ideal phase value at pixel position .

10. A measurement system, characterized in that, The measurement system includes a computer, and the computer is used to implement the phase reconstruction-based Micro-LED array measurement method according to any one of claims 1 to 9.

11. The measurement system according to claim 10, characterized in that, The measurement system further includes: A first displacement platform for moving the Micro-LED array to be measured in the x-axis direction and the y-axis direction; A stage provided on the first displacement platform for carrying and adjusting the pitch angle of the light-emitting surface of the Micro-LED array to be measured so that the light-emitting surface of the Micro-LED array is perpendicular to the optical axis of the measurement system; A focusing lens device is arranged on the outgoing light path of the to-be-tested Micro-LED array and is used to separate and converge the beam crosstalk generated by adjacent light-emitting units in the to-be-tested Micro-LED array; A microscope objective lens is arranged on the outgoing light path of the focusing lens device and is used to magnify the beam converged by the focusing lens device; An image sensor is arranged on the outgoing light path of the microscope objective lens and is mechanically connected to the microscope objective lens. It is used to receive and record the light intensity information magnified by the microscope objective lens to obtain the focal plane image and the multiple defocused plane images; A second displacement platform is used to adjust the height of the microscope objective lens and the image sensor in the z-axis direction. The second displacement platform is connected to both sides of the image sensor through an adapter plate.

12. The measurement system according to claim 11, wherein The accuracy of the first displacement platform reaches ±10 μm, the stroke of the first displacement platform is greater than the size of the to-be-tested Micro-LED array, and the aperture of the focusing lens device is more than 3 times the size of the to-be-tested Micro-LED array; the accuracy of the second displacement platform reaches ±1 μm, and the stroke of the second displacement platform is greater than 3 times the focal depth of the microscope objective lens; And / or, the numerical aperture of the microscope objective lens is greater than the numerical aperture of the focusing lens device.

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