Method for measuring relative intensity of high-order diffraction of metal mesh

Abstract

A method for measuring high-level diffraction relative intensity of a metal mesh belongs to the field of micro-nano structure photoelectric characteristic detection, and comprises the following steps: introducing a standard metal mesh diffraction reference quantity to construct a measurement transmission chain, and realizing step-by-step transmission of the diffraction reference quantity based on double-mesh diffraction light intensity measurement and comparison. The high-level diffraction light intensity corresponding to the diffraction reference quantity in the double-mesh diffraction image is selected, and the ratio of the high-level diffraction light intensity to the diffraction reference quantity is taken, so that the ratio of the diffraction reference quantities of adjacent levels can be obtained, and the magnitude comparison of the diffraction relative intensities between different meshes is realized. The measurement method breaks through the limitation of the measurement capability of a traditional light intensity sensor, effectively improves the measurement capability of the high-level diffraction extremely low relative intensity of the metal mesh, and provides a reliable means for testing the diffraction characteristics of the metal mesh.

Description

Technical Field

[0001] The invention belongs to the field of photoelectric property detection of micro-nano structures, and particularly relates to a method for measuring relative intensity of high-order diffraction of a metal grid. Background Art

[0002] With the development of information technology, the fields of satellite communication, mobile communication, medical examination and industrial flaw detection are inseparable from the application of electromagnetic waves. However, with the increasing intensity of electromagnetic wave applications and the widening of the application band, the electromagnetic pollution in the environment is becoming more and more serious, and the requirements for the research of electromagnetic shielding technology are also increasing. Nowadays, the development of electromagnetic shielding materials has gradually matured, and electromagnetic shielding materials based on different materials and structures have come out one after another. As a transparent conductive film, metal grid not only has good electromagnetic shielding ability, but also can meet the requirements of high transmittance at the same time, and is widely used in aircraft optical windows of aerospace equipment. With the continuous improvement of the requirements for the photoelectric detection capability of aircraft optical windows, in order to achieve a wider range and more accurate detection of targets, researchers have also put forward the requirements for the uniformity of the relative intensity distribution of higher-order diffraction for the optical transparency of optical windows. As one of the stray lights that affect the imaging quality, the high-order diffraction light will not only reduce the diffraction efficiency, but also may cause the problem of false imaging if the intensity is too high. The relative intensity of higher-order diffraction is an important indicator to measure the uniformity of higher-order diffraction. The measurement method of the relative intensity of higher-order diffraction of metal grid can further improve the evaluation system of metal grid imaging performance.

[0003] At present, in the research field of the relative intensity measurement method of the high-order diffraction of metal grids, no measurement method specifically for this value has been proposed. The relative intensity of the high-order diffraction of the metal grid is the ratio of the intensity of the high-order diffraction spot to the intensity of the zero-order diffraction spot. Therefore, when using an optical power meter for measurement, it is necessary to collect the intensity signals of the two diffraction spots in batches, which will introduce the influence of the fluctuation of the light source power over time in the measurement results. Each pixel of the CCD camera can independently record the light intensity information on its photosensitive surface, so multiple diffraction spot signals can be collected at the same time. However, as researchers deepen their research on the metal grid structure, the relative intensity of the high-order diffraction of the metal grid continues to decrease. The maximum relative intensity simulation prediction value of the high-order diffraction of some metal grids with excellent diffraction performance is already less than 0.01%, which is far beyond the light intensity measurement range of conventional CCD cameras.

[0004] It is not difficult to find that if the relative intensity of high-order diffraction is directly measured using conventional light intensity sensors, it is difficult to meet the measurement requirements of the relative intensity of high-order diffraction of metal grids, especially when various random grid structures are constantly proposed, the relative intensity of high-order diffraction is expected to be further reduced. Therefore, in view of the current key technical problems, it is possible to consider using indirect measurement methods to effectively improve the measurement capability of the relative intensity of high-order diffraction of metal grids:

[0005] 1. Patent 202222771857.6 "Anti-electromagnetic interference, high-precision light intensity detection device" describes an anti-electromagnetic interference, high-precision light intensity detection device that can realize the recognition of weak light sources, adaptive adjustment of saturation suppression of strong light sources, and high-precision light intensity measurement of linear working values, but cannot realize simultaneous measurement of multiple light spots;

[0006] 2. Patent 202121528372.3 “A low optical noise photoelectric measurement device” describes a low optical noise photoelectric measurement device, which improves the accuracy of light intensity measurement by designing the detector housing. However, the device can only obtain the sum of the light intensity signals on the photosensitive surface in a single measurement;

[0007] 3. Patent 202020064538.X "A high-precision light intensity sensor based on photodiode" describes a high-precision light intensity sensor based on photodiode, which has the advantages of simple circuit and low cost;

[0008] 4. Patent 201820429618.3 "A light intensity measurement device" describes a light intensity measurement device that measures the light intensity of a light beam by fixing the optical power meter probe in an open loop, solving the problem of inaccurate measurement caused by the optical power meter probe being unable to be fixed during light intensity measurement;

[0009] 5. Patent 201620444647.8 "An experimental device for measuring the intensity distribution of Fraunhofer single-slit diffraction light" describes an experimental device for measuring the intensity distribution of Fraunhofer single-slit diffraction light. The experimental device describes a method for setting up the experimental device when measuring Fraunhofer diffraction.

[0010] 6. Patents 201520917323.7 and 201610007023.4 have both improved the diffraction light intensity experimental device and used the guide rail structure to measure the diffraction light intensity distribution at different positions.

[0011] In summary, the main defects of the prior art are:

[0012] 1. There is a lack of measurement methods for the relative intensity characteristics of high-order diffraction of metal grids: Since the relative intensity of high-order diffraction of metal grids is the ratio of the absolute intensity of high-order diffraction to the absolute intensity of zero-order diffraction, the light intensity measurement device needs to collect two independent light intensity signal values ​​at the same time during the measurement process. Summarizing the characteristics of existing light intensity measurement devices, it is found that most of the current light intensity measurement devices focus on the high-precision measurement of a single light intensity signal, and lack measurement methods for the relative intensity characteristics of high-order diffraction of metal grids.

[0013] 2. The light intensity measurement range is limited: At present, the maximum relative intensity of high-order diffraction of some metal grid structures with excellent diffraction performance has been reduced to 1×10 -4 This means that the ratio of the minimum measurable light intensity to the maximum measurable light intensity of the light intensity measurement device needs to be less than one ten-thousandth, and noise is inevitably present in the actual sensor, and this light intensity noise further reduces the relative light intensity measurement range. In the prior art, most light intensity measurement devices are difficult to simultaneously meet the requirements of a large light intensity measurement range and low measurement noise. Summary of the invention

[0014] The purpose of the present invention is to fill the gap in the current method for measuring the relative intensity of high-order diffraction of metal grids, especially for some metal grid high-order diffraction with extremely low relative intensity, and propose a principle of a method for measuring the relative intensity of high-order diffraction of metal grids. By introducing a standard metal grid to construct a measurement transfer chain, the step-by-step transfer of the diffraction reference quantity is realized based on the double-grid diffraction image light intensity measurement, which effectively improves the measurement capability of the relative intensity of high-order diffraction of metal grids and provides a reliable experimental means for testing the diffraction characteristics of metal grids.

[0015] The object of the present invention is achieved by: a method for measuring the relative intensity of high-order diffraction of a metal grid, the method comprising the following steps:

[0016] Ⅰ. Select a light intensity sensor for collecting the two-dimensional distribution of the diffraction intensity of the metal grid. Each pixel of the light intensity sensor is required to independently collect light intensity signals to form a diffraction image with intensity information. The noise parameters of the light intensity sensor are calibrated and the signal-to-noise ratio of the light intensity sensor is calculated.

[0017] Ⅱ. The light intensity value of the collected signal when the signal-to-noise ratio of the light intensity sensor is x is recorded as the lower limit value of the measurement range I min , the full scale value of the light intensity sensor is recorded as the upper limit value of the measurement range I max , the ratio of the lower limit value to the upper limit value of the measuring range I min / I max Denoted as r o ;

[0018] III. Introduce n standard metal grids and select standard metal grid M i(where i = 1, 2, ..., n, the same below) the relative intensity of the higher order diffraction r i(mi,ni) As a standard metal grid diffraction reference X ref(i) , where r i(mi,ni) Standard metal grid M i The higher-order diffraction intensity I used as the diffraction reference i(mi,ni) and the zero-order diffraction light intensity I i(0,0) The ratio I i(mi,ni) / I i(0,0) , the standard metal grid diffraction reference quantity must satisfy the following relationship: X ref(1) >r o , X ref(i+1) / X ref(i) >r o ;

[0019] IV. Use the light intensity sensor to build a diffraction image acquisition device. First, collect the diffraction image of the standard metal grid M1. In the diffraction image, read the zero-order diffraction light intensity I 1(0,0) and the higher-order diffraction intensity I as a diffraction reference 1(m1,n1) , calculate the diffraction reference quantity X ref(1) =r 1(m1,n1) =I 1(m1,n1) / I 1(0,0) ;

[0020] V. Place the standard metal grid M1 and the standard metal grid M2 in parallel in the optical path, fix the standard metal grid M1, and rotate the standard metal grid M2 with the optical axis as the rotation axis, so that the (m1, n1)-order high-order diffraction spots of M1 and the (m2, n2)-order high-order diffraction spots of M2 are fully separated from other diffraction spots, and collect the diffraction image. Read the standard metal grid diffraction reference quantity X calculated in IV from the image ref(1) The diffraction light intensity I of the (m1, n1)-order diffraction spot used 固定(m1,n1) , and read the (m2,n2)-order diffraction light intensity I of the standard metal grid M2 旋转(m2,n2) , calculate the diffraction reference ratio X ref(2) / X ref(1) =I 旋转(m2,n2) / I 固定(m1,n1) , and so on, the standard metal grid M i and standard metal grid M i+1 Place it parallel to the optical path and rotate it appropriately. Collect the diffraction image and read the corresponding high-order diffraction light intensity. After calculation, the diffraction reference ratio X is obtained. ref(i+1) / X ref(i) =I 旋转(mi+1,ni+1) / I 固定(mi,ni) ;

[0021] Ⅵ、Standard Metal Grid Mn and the metal grid M to be tested p Placed parallel to the optical path, fixed with standard metal grid M n , rotate the metal grid M to be tested with the optical axis as the rotation axis p , so that M n The (mn,nn)-order diffraction spots and M p The (mp, np)-order diffraction spots are fully separated from other diffraction spots, and the diffraction image is collected. The standard metal grid M is calculated from the image. n Diffraction reference X ref(n) The diffraction intensity I of the (mn,nn)-order diffraction spots used 固定(mn,nn) , and read the metal grid M to be tested p The diffraction intensity of the (mp,np)-order higher-order diffraction is I 旋转(mp,np) , calculate the ratio r p / X ref(n) =I 旋转(mp,np) / I 原位(mn,nn) , where r p is the metal grid M to be tested p The relative intensity of the (mp,np)-level higher-order diffraction;

[0022] VII. Diffraction reference quantity X ref(1) , diffraction reference ratio X ref(i+1) / X ref(i) 、Metal grid to be tested M p Relative intensity of higher-order diffraction and standard metal grid M n The ratio of diffraction to reference p / X ref(n) Multiply them to get the metal grid M to be tested. p The relative intensity of (mp,np)-order diffraction p .

[0023] Preferably, in the above-mentioned method for measuring relative intensity of high-order diffraction of a metal grid, in step I, noise parameter calibration is performed based on the actual output image of the light intensity sensor.

[0024] Preferably, in the above-mentioned method for measuring the relative intensity of high-order diffraction of a metal grid, in step II, the lower limit value I of the light intensity measurement range of the sensor is min The signal-to-noise ratio value x is greater than or equal to 30dB.

[0025] Preferably, in the above-mentioned method for measuring the relative intensity of high-order diffraction of a metal grid, in step III, the value of the diffraction reference quantity of the standard metal grid should be such that the diffraction reference quantity X ref(1) and the diffraction reference ratio X ref(i+1) / X ref(i) In the range greater than or equal to ro Try to approach r o .

[0026] Preferably, in the above-mentioned method for measuring relative intensity of high-order diffraction of a metal grid, in step III, the grid unit period and line width of the standard metal grid are stable, and the dimensional fluctuation is less than 3% of its own average value.

[0027] Preferably, in the above-mentioned method for measuring the relative intensity of high-order diffraction of a metal grid, in step IV, the incident light of the diffraction image acquisition device is vertically incident on the surface of the metal grid, and the light intensity sensor receives a clear far-field diffraction image of the metal grid.

[0028] Preferably, in the above-mentioned method for measuring the relative intensity of high-order diffraction of a metal grid, in steps V-VI, when one of the standard metal grids is fixed and the other standard metal grid is rotated to a specific angle, the rotation angle of the rotating grid is slightly changed at the specific angle and the intensity of the high-order diffraction spot does not change, it indicates that the high-order diffraction spot is fully separated from other diffraction spots.

[0029] The innovation and good effects of the present invention are:

[0030] 1. A method for measuring the relative intensity of high-order diffraction of a metal grid of the present invention introduces a standard grid diffraction reference to construct a diffraction measurement transmission chain, thereby realizing the transmission from a diffraction relative intensity with a higher value to a diffraction relative intensity with an extremely low value, breaking through the limitation of the measurement capability of traditional light intensity sensors, and being able to effectively measure the relative intensity of high-order diffraction of a metal grid with extremely low relative intensity.

[0031] 2. Taking full advantage of the characteristics of the double-grid diffraction image, a method is proposed to compare the relative diffraction intensity values ​​between different grids when two standard metal grids are parallel to each other and one of the grids is properly rotated to fully separate the high-order diffraction energies;

[0032] 3. A design method for diffraction reference in the measurement transmission chain is proposed, that is, the ratio of diffraction references at adjacent levels should not be lower than the minimum relative intensity measurable by the light intensity sensor, and according to the principle of the shortest measurement chain, it must approach the minimum relative intensity measurable by the camera, ensuring that the final metal grid high-order diffraction relative intensity measurement results have good measurement accuracy;

[0033] In view of the above-mentioned innovation and good results achieved by the present invention, it has great application value in the detection of photoelectric characteristics of micro-nano structures in imaging windows of advanced optical instruments. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0035] Figure 1 It is a logic block diagram of the measurement transfer chain based on the standard grid diffraction reference quantity described in the present invention.

[0036] Figure 2 It is the schematic diagram of the image acquisition device for light intensity sensor output test.

[0037] Figure 3 It is a schematic diagram of the value transfer of the diffraction reference quantity in the measurement transfer chain.

[0038] Figure 4 It is a schematic diagram of the relationship between the values ​​of diffraction reference quantities in the measurement transfer chain.

[0039] Figure 5 It is the schematic diagram of the metal grid diffraction image acquisition device.

[0040] Figure 6 It is a three-dimensional schematic diagram of the double-grid diffraction structure when the higher-order diffraction spots are fully separated.

[0041] Figure 7 This is a schematic diagram of the relative position of the double grid when the higher-order diffraction spots are fully separated.

[0042] Figure 8 It is the diffraction image of the standard grid M1 collected by the sensor in the example of the present invention.

[0043] Fig. 9 It is a diffraction image produced by superposition of the standard grid M1 and the standard grid M2 when the high-order diffraction spots are fully separated in the example of the present invention.

[0044] Fig.10 In the example of the present invention, when the high-order diffraction spots are fully separated, the standard grid M2 and the grid to be tested M p The diffraction image produced by the superposition of .

[0045] Fig.11 is the minimum relative intensity r that can be measured by the CCD in the present invention. o , Standard grid diffraction reference quantity X ref(1) , Standard grid diffraction reference quantity X ref(2) and the relative intensity of the higher-order diffraction of the grid to be measured r p Specific numerical measurement results diagram. DETAILED DESCRIPTION

[0046] The present invention is further described below with reference to the accompanying drawings and preferred embodiments: The object of the present invention is achieved by adopting a method for measuring the relative intensity of high-order diffraction of a metal grid, the method comprising the following steps:

[0047] Ⅰ. Select a light intensity sensor for collecting the two-dimensional distribution of the diffraction intensity of the metal grid. Each pixel of the light intensity sensor is required to independently collect light intensity signals to form a diffraction image with intensity information. The noise parameters of the light intensity sensor are calibrated and the signal-to-noise ratio of the light intensity sensor is calculated.

[0048] Ⅱ. The light intensity value of the collected signal when the signal-to-noise ratio of the light intensity sensor is x is recorded as the lower limit value of the measurement range I min , the full scale value of the light intensity sensor is recorded as the upper limit value of the measurement range I max , the ratio of the lower limit value to the upper limit value of the measuring range I min / I max Denoted as r o ;

[0049] III. Introduce n standard metal grids and select standard metal grid M i (where i = 1, 2, ..., n, the same below) the relative intensity of the higher order diffraction r i(mi,ni) As a standard metal grid diffraction reference X ref(i) , where r i(mi,ni) Standard metal grid M i The higher-order diffraction intensity I used as the diffraction reference i(mi,ni) and the zero-order diffraction light intensity I i(0,0) The ratio I i(mi,ni) / I i(0,0) , the standard metal grid diffraction reference quantity must satisfy the following relationship: X ref(1) >r o , X ref(i+1) / X ref(i) >r o ;

[0050] IV. Use the light intensity sensor to build a diffraction image acquisition device. First, collect the diffraction image of the standard metal grid M1. In the diffraction image, read the zero-order diffraction light intensity I 1(0,0) and the higher-order diffraction intensity I as a diffraction reference 1(m1,n1) , calculate the diffraction reference quantity X ref(1) =r 1(m1,n1) =I 1(m1,n1) / I 1(0,0) ;

[0051] V. Place the standard metal grid M1 and the standard metal grid M2 in parallel in the optical path, fix the standard metal grid M1, and rotate the standard metal grid M2 with the optical axis as the rotation axis, so that the (m1, n1)-order high-order diffraction spots of M1 and the (m2, n2)-order high-order diffraction spots of M2 are fully separated from other diffraction spots, and collect the diffraction image. Read the standard metal grid diffraction reference quantity X calculated in IV from the image ref(1) The diffraction light intensity I of the (m1, n1)-order diffraction spot used 固定(m1,n1) , and read the (m2,n2)-order diffraction light intensity I of the standard metal grid M2 旋转(m2,n2) , calculate the diffraction reference ratio X ref(2) / X ref(1) =I 旋转(m2,n2) / I 固定(m1,n1) , and so on, the standard metal grid M i and standard metal grid M i+1 Place it parallel to the optical path and rotate it appropriately. Collect the diffraction image and read the corresponding high-order diffraction light intensity. After calculation, the diffraction reference ratio X is obtained. ref(i+1) / X ref(i) =I 旋转(mi+1,ni+1) / I 固定(mi,ni) ;

[0052] Ⅵ、Standard metal grid M n and the metal grid M to be tested p Placed parallel to the optical path, fixed with standard metal grid M n , rotate the metal grid M to be tested with the optical axis as the rotation axis p , so that M n The (mn,nn)-order diffraction spots and M p The (mp, np)-order diffraction spots are fully separated from other diffraction spots, and the diffraction image is collected. The standard metal grid M is calculated from the image. n Diffraction reference X ref(n) Diffraction intensity of the (mn,nn)-order diffraction spots used And read the metal grid M to be tested p The diffraction intensity of the (mp, np)-order higher-order diffraction Calculate the ratio Among them, r p is the metal grid M to be tested p The relative intensity of the (mp,np)-level higher-order diffraction;

[0053] VII. Diffraction reference quantity X ref(1) , diffraction reference ratio X ref(i+1) / X ref(i) 、Metal grid to be tested M pRelative intensity of higher-order diffraction and standard metal grid M n The ratio of diffraction to reference p / X ref(n) Multiply them to get the metal grid M to be tested. p The relative intensity of (mp,np)-order diffraction p .

[0054] The present invention provides a method for measuring the relative intensity of high-order diffraction of a metal grid. The measurement transmission chain logic block diagram is as follows: Figure 1 As shown, Figure 1 The transfer direction of the standard grid diffraction reference amount and the transfer method between adjacent levels of diffraction reference amounts are demonstrated.

[0055] The present invention provides a method for measuring the relative intensity of high-order diffraction of a metal grid. The principle diagram of the light intensity sensor output test image acquisition device is as follows: Figure 2 As shown, in this device, the light emitted by the surface light source is uniformly treated by the diffusion film and finally reaches the photosensitive surface of the sensor, so that each pixel point on the photosensitive surface of the sensor can receive the same light intensity. The test image output at this time is collected for the calibration of the sensor noise parameters.

[0056] Figure 3 It is a schematic diagram of the value transfer of the diffraction reference quantity in the measurement transfer chain. The diffraction reference quantity is transferred from high level to low level step by step. The diffraction reference quantity X ref(1) The value is greater than the minimum relative intensity r that the light intensity sensor can measure o , with the increase of the reference level, the value of the diffraction reference quantity continues to decrease.

[0057] Figure 4 It is a schematic diagram of the relationship between the diffraction reference quantities in the measurement transfer chain. The value of the diffraction reference quantity needs to make the ratio of the diffraction reference quantities of adjacent levels satisfy X ref(i+1) / X ref(i) >r o , and the ratio needs to be as close as possible to the minimum relative intensity r that the light intensity sensor can measure o .

[0058] Figure 5 This is the schematic diagram of a diffraction image acquisition device. An attenuator is added to the light source of the device to ensure that the incident light power is adjustable. Focusing imaging is performed through a lens to ensure that the sensor receives the far-field diffraction image of the grid. During the diffraction image acquisition process, the device needs to take light shielding measures throughout the process.

[0059] Figure 6 This is a three-dimensional schematic diagram of the double-grid diffraction structure when the higher-order diffraction spots are fully separated. Figure 7It is a planar schematic diagram of the double-grid diffraction structure when the high-order diffraction spots are fully separated. The planes where the two metal grids are located are parallel to each other, and the angle formed by the metal grid lines is θ.

[0060] The core of the present invention is to provide a method for measuring the relative intensity of high-order diffraction of a metal grid. The method is characterized in that it introduces a standard grid diffraction reference to build a measurement transmission chain to achieve the step-by-step transmission of the relative intensity of diffraction. The method creatively uses the characteristics of the double grid diffraction image to achieve the comparison of the relative intensity of diffraction between different grids, which not only achieves the measurement of high-order diffraction of metal grids with extremely low relative intensity, but also ensures that the measurement results have high accuracy. Figure 8 , Fig. 9 , Fig.10 , Fig.11 The present invention is implemented in an embodiment to illustrate the effectiveness of the measurement method when applied to the relative intensity measurement of high-order diffraction of a metal grid. The present invention takes the introduction of two standard grid diffraction reference quantities as an example to illustrate the effect of the measurement method. Figure 8 The diffraction image of the standard grid M1 collected by the sensor is given. The diffraction reference quantity X can be obtained by reading the diffraction light intensity in the image. ref(1) =0.0328. Fig. 9 The diffraction image produced by the superposition of standard grid M1 and standard grid M2 when the high-order diffraction energy is fully separated is given. By reading the diffraction light intensity in the image and calculating, the ratio X of the diffraction reference quantity can be obtained. ref(2) / X ref(1) =0.0375. Fig.10 The standard grid M2 and the grid to be tested M2 are given when the high-order diffraction energy is fully separated. p The diffraction image produced by the superposition of the diffraction light intensity in the image can be calculated to obtain the relative intensity r of the high-order diffraction of the grid to be measured. p With the diffraction reference X ref(2) The ratio r p / X ref(2) = 0.0440. The diffraction reference quantity X ref(1) , the ratio of the diffraction reference quantity X ref(2) / X ref(1) , relative intensity of high-order diffraction of the grid to be measured r p With the diffraction reference X ref(2) The ratio r p / X ref(2) Multiply them to get the relative intensity measurement result r of the high-order diffraction of the grid to be measured. p =5.41×10 -5 . Fig.11 The minimum relative intensity r that can be measured by CCD is given o , Standard grid diffraction reference quantity Xref(1) , Standard grid diffraction reference quantity X ref(2) and the relative intensity of the higher-order diffraction of the grid to be measured r p The specific values ​​of indicate that the embodiment of the present invention introduces two standard grid diffraction reference quantities to construct a measurement transfer chain, thereby achieving the measurement of the relative intensity of the metal grid high-order diffraction. The measurement result is 5.41×10 -5 , achieving a value of less than 1×10 -4 Measurement of the relative intensity of high-order diffraction of metal grids.

Claims

1. A standard metal grid metal grid high-order diffraction relative intensity measurement method, It is characterized in that The method comprises the following steps: Ⅰ. Select a light intensity sensor for collecting the two-dimensional distribution of the diffraction intensity of the metal grid. Each pixel of the light intensity sensor is required to independently collect light intensity signals to form a diffraction image with intensity information. The noise parameters of the light intensity sensor are calibrated and the signal-to-noise ratio of the light intensity sensor is calculated. Ⅱ. The light intensity value of the collected signal when the signal-to-noise ratio of the light intensity sensor is x is recorded as the lower limit value of the measurement range I min , the full scale value of the light intensity sensor is recorded as the upper limit value of the measurement range I max , the ratio of the lower limit value to the upper limit value of the measuring range I min / I max Denoted as r o ; III. Introduce n standard metal grids and select standard metal grid M i (where i = 1, 2, ..., n, the same below) the relative intensity of the higher order diffraction r i(mi,ni) As a standard metal grid diffraction reference X ref(i) , where r i(mi,ni) Standard metal grid M i The higher-order diffraction intensity I used as the diffraction reference i(mi,ni) and the zero-order diffraction light intensity I i(0,0) The ratio I i(mi,ni) / I i(0,0) , the standard metal grid diffraction reference quantity must satisfy the following relationship: X ref(1) >r o , X ref(i+1) / X ref(i) >r o ; IV. Use the light intensity sensor to build a diffraction image acquisition device. First, collect the standard metal grid M 1 The diffraction image of the zero-order diffraction light intensity I is read in the diffraction image. 1(0,0) and the higher-order diffraction intensity I as a diffraction reference 1(m1,n1) , calculate the diffraction reference quantity X ref(1) =r 1(m1,n1) =I 1(m1,n1) / I 1(0,0) ; Ⅴ、Standard metal grid M 1 and standard metal grid M 2 Placed parallel to the optical path, fixed with standard metal grid M 1 , rotate the standard metal grid M with the optical axis as the rotation axis 2 , so that M 1 (m 1 ,n 1 ) level higher order diffraction spots and M 2 (m 2 ,n 2 )-level high-order diffraction spots are fully separated from other diffraction spots, and a diffraction image is collected. The standard metal grid diffraction reference quantity X is calculated from the image. ref(1) Used (m 1 ,n 1 ) The diffraction intensity of the higher-order diffraction spot I 固定(m1,n1) , and read the standard metal grid M 2 (m 2 ,n 2 ) level higher order diffraction light intensity I 旋转(m2,n2) , calculate the diffraction reference ratio X ref(2) / X ref(1) =I 旋转(m2,n2) / I 固定(m1,n1) , and so on, the standard metal grid M i and standard metal grid M i+1 Place it parallel to the optical path and rotate it appropriately. Collect the diffraction image and read the corresponding high-order diffraction light intensity. After calculation, the diffraction reference ratio X is obtained. ref(i+1) / X ref(i) =I 旋转(mi+1,ni+1) / I 固定(mi,ni) ; Ⅵ、Standard metal grid M n and the metal grid M to be tested p Placed parallel to the optical path, fixed with standard metal grid M n , rotate the metal grid M to be tested with the optical axis as the rotation axis p , so that M n (m n ,n n ) and M p (m p ,n p )-level high-order diffraction spots are fully separated from other diffraction spots, and the diffraction image is collected. The standard metal grid M is calculated from the image. n Diffraction reference X ref(n) Used (m n ,n n )-order diffraction light intensity of the higher-order diffraction spot And read the metal grid M to be tested p The diffraction intensity of the (mp,np)-order higher-order diffraction is I 旋转(mp,np) , calculate the ratio r p / X ref(n) =I 旋转(mp,np) / I 原位(mn,nn) , where r p is the metal grid M to be tested p The relative intensity of the (mp,np)-level higher-order diffraction; VII. Diffraction reference quantity X ref(1) , diffraction reference ratio X ref(i+1) / X ref(i) 、Metal grid to be tested M p Relative intensity of higher-order diffraction and standard metal grid M n The ratio of diffraction to reference p / X ref(n) Multiply them to get the metal grid M to be tested. p The relative intensity of (mp,np)-order diffraction p .

2. A method for measuring relative intensity of high-order diffraction of a metal grid according to claim 1, Features: In the step I, noise parameter calibration is performed based on the actual output image of the light intensity sensor.

3. A method for measuring relative intensity of high-order diffraction of a metal grid according to claim 1, Features: In step II, the lower limit value of the sensor light intensity measurement range I min The signal-to-noise ratio value x is greater than or equal to 30dB.

4. A method for measuring relative intensity of high-order diffraction of a metal grid according to claim 1, Features: In step III, the value of the diffraction reference quantity of the standard metal grid should be such that the diffraction reference quantity X ref(1) and the diffraction reference ratio X ref(i+1) / X ref(i) In the range greater than or equal to r o Try to approach r o .

5. A method for measuring relative intensity of high-order diffraction of a metal grid according to claim 1, Features: In the step III, the grid unit period and line width of the standard metal grid are stable, and the size fluctuation is less than 3% of its own average value.

6. A method for measuring relative intensity of high-order diffraction of a metal grid according to claim 1, Features: In step IV, the incident light of the diffraction image acquisition device is vertically incident on the surface of the metal grid, and the light intensity sensor receives a clear far-field diffraction image of the metal grid.

7. A method for measuring relative intensity of high-order diffraction of a metal grid according to claim 1, Features: In the steps V-VI, when one of the standard metal grids is fixed and the other standard metal grid is rotated to a specific angle, and the rotation angle of the rotating grid is slightly changed at the specific angle while the intensity of the higher-order diffraction spot does not change, it indicates that the higher-order diffraction spot is fully separated from the other diffraction spots.

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