Quantitative measurement method for micro-pore diameter based on light intensity integration
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- SUZHOU UNIV
- Filing Date
- 2026-03-11
- Publication Date
- 2026-05-29
AI Technical Summary
Existing methods for measuring micropores, such as scanning electron microscopy and optical microscopy, suffer from problems such as expensive equipment, slow measurement speed, high destructiveness to samples, or limited accuracy. In particular, it is difficult to achieve rapid, non-destructive, and accurate detection when measuring micron-sized pores.
An indirect measurement method based on light intensity integration is adopted. The diameter of the micropore is inferred by measuring the integral of the transmitted light intensity. A mapping curve between the light intensity integral and the aperture size is established. The diameter of the micropore is obtained by fitting the curve using the least squares method and performing inversion calculation, thus avoiding direct identification of the aperture edge.
It enables rapid, non-destructive, and high-precision measurement of micron-sized pores, with an accuracy of up to 0.1 microns. It can simultaneously detect multiple pores and is not limited by the diffraction limit, making it suitable for optical microscope systems or independent measurement devices.
Smart Images
Figure CN121804342B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to a method for quantitative measurement of micropore diameter based on light intensity integration, belonging to the field of optical precision measurement. Background Technology
[0002] In many fields such as microelectronics, microfluidics, and electrospun precision filters, there is a significant need for rapid, non-destructive, and accurate measurement of micron-sized pores. Current mainstream measurement methods include scanning electron microscopy (SEM) and optical microscopy image processing. While SEM offers extremely high precision, it is expensive, requires a vacuum environment, is slow, and can be destructive to samples. Confocal microscopy, although offering high resolution (up to 150 nm), also suffers from high equipment costs, slow imaging speeds due to its scanning mode, and limitations when dealing with large-scale pore size detection. Ordinary optical microscopes, limited by the diffraction limit, produce blurred image edges when the aperture size is close to or smaller than the optical system's resolution. This makes it impossible to accurately extract the geometric dimensions using image processing algorithms such as edge detection and thresholding, leading to a sharp decrease in measurement accuracy.
[0003] To address the aforementioned issues, this invention proposes an indirect measurement method based on light intensity analysis. Instead of directly analyzing the edge contour of the aperture, it infers the size of each microaperture by detecting the total light flux irradiating it. Summary of the Invention
[0004] The purpose of this invention is to provide a method for quantitative measurement of micropore diameter based on light intensity integration, which aims to achieve rapid detection of the diameter of multiple micrometer-scale pores simultaneously, while achieving near-optical diffraction limit accuracy.
[0005] The technical solution of this invention is:
[0006] A method for quantitatively measuring the diameter of micropores based on light intensity integration includes the following steps:
[0007] Step 1: Illuminate the sample with a known diameter aperture vertically with a uniform collimated beam from the light source. After imaging by the imaging system, the micro-aperture image is captured by the image acquisition system. Further, read the light intensity integral of the known diameter aperture and establish the mapping curve of light intensity integral versus diameter.
[0008] In step 1, a mapping curve between the transmitted light intensity integral and the aperture size is established, specifically as follows:
[0009] Step 11: After passing through the imaging system, the integral of the light intensity I received by each micro-aperture on the image acquisition system is:
[0010] ,
[0011] Where d is the aperture diameter, a is a parameter representing the integral of the background light intensity, and b is a parameter including the wave vector, which is a constant under the same illumination and imaging system.
[0012] Step 12: By measuring a set of known diameters d i Light intensity integral of standard micropore array , with the diameter d of each aperture i The x-axis represents the integral of light intensity for each aperture. Using the ordinate as the vertical axis, a quadratic term fitting is performed using the least squares method to obtain a and b under the corresponding illumination and imaging conditions, and thus the mapping curve is obtained: ;
[0013] Step 2: Capture the sample image of the actual micropore to be tested using the same light source, imaging objective, and image acquisition system as in Step 1;
[0014] Step 3: During measurement, the transmitted light intensity integrals of multiple micropores to be measured are read and substituted into the mapping curve for inversion calculation. The diameter value is obtained by solving the inverse equation.
[0015] In step 3, the inverse equation is:
[0016] ,
[0017] in, Let be the diameter of the i-th hole to be measured. Let be the integral of the light intensity of the i-th aperture to be measured.
[0018] Furthermore, in step 1, the imaging system includes an illumination module, an imaging objective lens, an image acquisition system, and a calibration and data processing module arranged sequentially.
[0019] The beneficial effects of this invention are as follows: This method for quantitatively measuring the diameter of micropores based on light intensity integration differs from traditional methods that first identify the edges of the micropores and then extract the contours for diameter calculation. Since the edge information of the micropores is mainly determined by high-frequency spatial components, traditional methods heavily rely on system resolution and are limited by the physical diffraction limit. In contrast, the light intensity integration information collected by this invention mainly relies on low-frequency components and is not limited by the diffraction limit. This enables rapid detection of multiple micrometer-scale micropore diameters, improving measurement accuracy and reliability. It achieves high-precision measurement of micropore diameters in the 1-10 micrometer range, with an accuracy of up to 0.1 micrometers. Furthermore, compared to traditional high-precision measurement methods, such as confocal microscopy, this method eliminates the need for time-consuming scanning processes and can achieve high-precision, rapid, and non-destructive detection of all subwavelength-sized micropores in an image using a single frame. It can be integrated into optical microscope systems or used as a standalone measurement device. Attached Figure Description
[0020] Figure 1 This is a schematic flowchart of the method for quantitative measurement of micropore diameter based on light intensity integration according to an embodiment of the present invention;
[0021] Figure 2 This is a schematic diagram of a sample with a known diameter small hole in the embodiment;
[0022] Figure 3 This is a schematic diagram illustrating the imaging system in the embodiment;
[0023] Figure 4 This is a schematic diagram illustrating the mapping relationship between the integral of transmitted light intensity and the aperture size in the embodiment.
[0024] Figure 5 This is a schematic diagram of the sample to be tested in the embodiment;
[0025] Figure 6 This is a schematic diagram of the sample to be tested in the embodiment;
[0026] Figure 7 This is a schematic diagram comparing the radius measured by the micropore diameter quantitative measurement method based on light intensity integration and the diameter measured by SEM in the embodiment. Among them, (a) is a schematic diagram of the diameter measured by the micropore diameter quantitative measurement method based on light intensity integration in the embodiment, and (b) is a schematic diagram of the diameter measured by SEM.
[0027] Figure 8 This is a schematic diagram comparing the radius measured by the micropore diameter quantitative measurement method based on light intensity integration with the probability density obtained by SEM measurement in the embodiment. (a) is a schematic diagram of the probability density obtained by the micropore diameter quantitative measurement method based on light intensity integration in the embodiment, and (b) is a schematic diagram of the probability density obtained by SEM measurement. Detailed Implementation
[0028] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings.
[0029] The embodiment provides a method for quantitative measurement of micropore diameter based on light intensity integration, such as Figure 1 This includes the following steps:
[0030] Step 1: Illuminate the sample with a known diameter aperture perpendicularly with a uniform, collimated beam from the light source. Figure 2 After passing through an imaging system such as Figure 3 After imaging, the micro-aperture image is captured by the image acquisition system; the light intensity integral of the aperture with a known diameter is then read to establish the light intensity-diameter mapping curve.
[0031] In step 1, the imaging system includes, in sequence, an illumination module, an imaging objective lens, an image acquisition system, and a calibration and data processing module. The illumination module generates a uniform, collimated beam. Taking the most common Kohler illumination in microscopes as an example, it consists of a light source, a condenser lens, an aperture stop, and a focusing lens. There are no specific requirements for the light source; it can be an LED lamp, laser lamp, halogen lamp, etc. Collimation can be achieved using the Kohler illumination system. Collimation requirements are based on the size of the sample area to be measured, ensuring uniform intensity of illumination across the sample area. The aperture stop is minimized while ensuring sufficient light intensity to achieve an approximately uniform irradiation field. The sample is mounted on a movable platform to allow for sequential measurement of multiple micro-apertures. The image acquisition system, such as a photodiode, scientific-grade CCD camera, or CMOS camera, collects the light signals passing through the micro-apertures and converts them into electrical signals. The calibration and data processing module is responsible for controlling the measurement process, storing calibration data, fitting mapping curves, and calculating diameter values.
[0032] In step 1, a mapping curve between the transmitted light intensity integral and the aperture size is established, specifically as follows:
[0033] Step 11: After passing through the imaging system, the integral of the light intensity I received by each micro-aperture on the image acquisition system is:
[0034] ,
[0035] Where d is the aperture diameter, a is a parameter representing the background light intensity, and b is a parameter including the wave vector, which is a constant under the same illumination and imaging system.
[0036] Step 12: By measuring a set of known diameters d i Integral light intensity of a standard micropore array norm (i) Using the diameter d of each aperture i The x-axis represents the integral of light intensity I corresponding to each aperture. norm (i) is the ordinate. By using the least squares method to fit the quadratic term, we can obtain a and b under the corresponding illumination and imaging conditions, and obtain the mapping curve: .
[0037] Step 2: Capture the sample image of the actual micropore to be tested using the same light source, imaging objective, and image acquisition system as in Step 1.
[0038] Step 3: During measurement, the transmitted light intensity integrals of multiple micropores to be measured are read and substituted into the mapping curve for inversion calculation. The diameter value is obtained by solving the inverse equation.
[0039] In step 3, the inverse equation is:
[0040]
[0041] Where, d target (i) is the diameter of the i-th hole to be measured, I target (i) is the integral of the light intensity of the i-th aperture to be measured.
[0042] This method for quantitative measurement of micropore diameter based on the light intensity integration method addresses the limitations of traditional methods, which require edge identification to extract the contour for resolving micropore diameters. Since edge information is primarily determined by high-frequency spatial components, traditional methods heavily rely on system resolution and are constrained by the physical diffraction limit. In contrast, this invention collects light intensity primarily based on low-frequency components, is not limited by the diffraction limit, and enables rapid detection of multiple micrometer-scale micropore diameters. This improves measurement accuracy and reliability, achieving high-precision measurement of micropore diameters in the 1-10 micrometer range, with an accuracy of up to 0.1 micrometers. Furthermore, compared to traditional high-precision measurement methods, such as confocal microscopy, this method eliminates the need for time-consuming scanning processes. It can achieve high-precision, rapid, and non-destructive detection of all subwavelength-sized micropores in an image using a single frame, and can be integrated into optical microscopy systems or used as a standalone measurement device.
[0043] This method for quantitatively measuring the diameter of micropores based on light intensity integration presents two scenarios when uniformly collimated light is irradiated onto the sample surface: (1) When the light spot irradiates a non-pore area, the light is completely blocked, and the transmitted light intensity is almost zero. (2) When the light spot irradiates a micropore, the light can pass through, and its transmitted light intensity integral is closely related to the effective light-transmitting area of the aperture. This subwavelength aperture measurement system is not limited to using a camera array for detection; it can also use a photodiode for point detection. The standard sample can be on the same substrate as the sample to be measured or it can be an independent calibration component. The illumination light can be monochromatic or broadband light combined with a filter.
[0044] The principle of this method for quantitatively measuring the diameter of a microaperture based on light intensity integration is explained as follows: According to the theory of light energy flux density, under uniform collimated light perpendicular illumination, the integral of the transmitted light intensity of a microaperture is proportional to its area, i.e., proportional to the square of its diameter. Considering factors such as background light intensity and detector dark current in the imaging system, a constant 'a' is introduced to represent the parameter of background light intensity, and a constant 'b' is a parameter including the wave vector, i.e., the system response coefficient, which incorporates factors such as light source intensity, imaging system transmittance, and detector response. Therefore, the integral of light intensity and the aperture diameter satisfy a quadratic relationship: .
[0045] The following example illustrates this method for quantitative measurement of micropore diameter based on light intensity integration:
[0046] First, the light emitted from the laser is expanded and collimated to form a uniform and stable illumination field. The standard samples are a series of micro-holes with diameters precisely calibrated by SEM, fabricated on a silicon wafer: 1.4 μm, 1.5 μm, 1.6 μm, 1.7 μm, 1.8 μm, 1.9 μm, 2.0 μm, 2.1 μm, and 2.2 μm. The standard samples are placed in the illumination field, and the transmitted light is collected using a 20x microscope objective. The light intensity is detected by a high dynamic range scientific-grade CMOS camera. For each standard hole, an image is acquired, and the total grayscale value of the pixels within the hole region is calculated as the light intensity signal I.
[0047] like Figure 4 As shown, with the square of the diameter as the horizontal axis and the integral of the light intensity of each aperture as the vertical axis, the data points exhibit a good quadratic relationship. Linear fitting using the least squares method yields the mapping curve equation I = -1667759.39 + 2680234.19 * d 2 .
[0048] Subsequently, the sample to be tested was measured, such as... Figure 5 The light intensity integrals measured from a total of 101 micropores in the sample were substituted into the above mapping curve for inverse calculation. Through repeated measurements and statistical analysis of multiple micropores, the average diameter, variance, and distribution of the 101 micropores were obtained. Figure 6 for Figure 5 SEM image of the small hole within the red box.
[0049] Figure 7 This is a schematic diagram comparing the radius measured by the micropore diameter quantitative measurement method based on light intensity integration with the diameter measured by SEM in an embodiment. Figure 7 (a) is a schematic diagram of the diameter measured by the micropore diameter quantitative measurement method based on light intensity integration in the embodiment. Figure 7 (b) is a schematic diagram of the diameter measured by SEM. For example... Figure 7 As shown, the average diameter obtained from the embodiment can be within 0.1 micrometers of the average diameter obtained by SEM electron microscopy.
[0050] Figure 8 This is a schematic diagram comparing the radius measured by the micropore diameter quantitative measurement method based on light intensity integration with the probability density obtained by SEM measurement. Figure 8 (a) is a schematic diagram of the probability density obtained by the quantitative measurement method of micropore diameter based on light intensity integration in the embodiment. Figure 8 (b) is a schematic diagram of the probability density obtained from SEM measurements. For example... Figure 8 As shown, their distribution is quite consistent, which can meet the requirements for rapid detection of large batches and large quantities of round hole samples.
[0051] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any transformations or substitutions that can be conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of the present invention. Therefore, the scope of protection of the present invention should be defined by the scope of the claims.
Claims
1. A method for quantitatively measuring the diameter of a micropore based on light intensity integration, characterized in that: Includes the following steps, Step 1: Illuminate the sample with a known diameter aperture vertically with a uniform collimated beam from the light source. After imaging by the imaging system, the micro-aperture image is captured by the image acquisition system. Further, read the light intensity integral of the known diameter aperture and establish the mapping curve of light intensity integral versus diameter. In step 1, a mapping curve between the transmitted light intensity integral and the aperture size is established, specifically as follows: Step 11: After passing through the imaging system, the integral of the light intensity I received by each micro-aperture on the image acquisition system is: ， Where d is the aperture diameter, a is a parameter representing the integral of the background light intensity, and b is a parameter including the wave vector, which is a constant under the same illumination and imaging system. Step 12: By measuring a set of known diameters d i Light intensity integral of standard micropore array , with the diameter d of each aperture i The x-axis represents the integral of light intensity for each aperture. Using the ordinate as the vertical axis, a quadratic term fitting is performed using the least squares method to obtain a and b under the corresponding illumination and imaging conditions, and thus the mapping curve is obtained: ; Step 2: Capture the sample image of the actual micropore to be tested using the same light source, imaging objective, and image acquisition system as in Step 1; Step 3: During measurement, the transmitted light intensity integrals of multiple micropores to be measured are read and substituted into the mapping curve for inversion calculation. The diameter value is obtained by solving the inverse equation. In step 3, the inverse equation is: ， in, Let be the diameter of the i-th hole to be measured. Let be the integral of the light intensity of the i-th aperture to be measured.
2. The method for quantitative measurement of micropore diameter based on light intensity integration as described in claim 1, characterized in that: In step 1, the imaging system includes an illumination module, an imaging objective lens, an image acquisition system, and a calibration and data processing module arranged sequentially.