Spray printing height measuring and calculating method

Abstract

The invention is applicable to the field of jet printing, and discloses a jet printing height measuring and calculating method, which comprises the following steps of: emitting polychromatic light to a measured base material and a nozzle surface from one side, far away from a nozzle, of the measured base material by using a spectral confocal sensor, and receiving a first optical signal reflected from one side, close to the nozzle, of the measured base material and a second optical signal reflected by the nozzle; determining a first focusing wavelength focused on one side, close to the nozzle, of the measured base material, a second focusing wavelength focused on the nozzle and a nozzle incident angle according to the two optical signals, and substituting the first focusing wavelength, the second focusing wavelength and the nozzle incident angle into a pre-constructed refractive index calculation function to calculate the refractive index; substituting the dual wavelengths into a pre-constructed initial thickness calculation function and an error correction model to obtain a theoretical height value and an error compensation amount; if the inclination angle of the measured base material is not 0 degree, the actual height value from the measured base material to the nozzle is calculated according to a pre-constructed first real thickness calculation function, and the method is used for achieving online high-precision monitoring of the jet printing height.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of inkjet printing, and in particular to a method for calculating the height of inkjet printing. BACKGROUND

[0002] In the process of researching and developing OLED inkjet printing equipment, real-time accurate measurement of the height of inkjet printing is a key parameter for ensuring film uniformity and device performance. The height of inkjet printing refers to the vertical distance from the nozzle surface to the substrate surface. With the evolution of display technology towards large size and flexibility, non-contact inkjet printing gradually replaces the traditional evaporation process. Studies have shown that a ±5μm fluctuation in the height of inkjet printing will cause uneven ink drop spreading, and thus lead to a decrease in device efficiency. However, the existing measurement techniques generally have the problem of insufficient medium penetration, and cannot directly penetrate the transparent panel to obtain the height of the upper surface, or need to use multiple measurement conversion calculations, which causes system error accumulation and has become a technical bottleneck restricting the mass production of high-generation lines of OLEDs.

[0003] The current mainstream measurement methods have the following limitations: The laser triangulation method has fast response speed, but the light path is easily disturbed by the refraction effect in the transparent medium, the measurement value reflects the position of the lower surface of the glass, and the error can reach dozens of microns; the reflection signals of multiple layers of interfaces are superimposed, increasing the difficulty of separating the effective signals. If the height of printing is calculated by multiple measurements and conversion, not only will the system error be amplified, but also the overall measurement accuracy will be difficult to improve.

[0004] The white light interference method has high precision, but the sampling rate is less than 100Hz, and it is highly sensitive to external vibration and temperature fluctuation, so it needs to be equipped with vibration isolation and constant temperature devices, increasing the volume and complexity of the equipment, which is not conducive to online integrated applications.

[0005] The traditional spectral confocal technology relies on the perpendicularity of the optical axis of the sensor and the measured object, as well as the accurate calibration of the refractive index of the transparent medium, and lacks a multi-layer refraction compensation mechanism at the algorithm level, resulting in axial error accumulation and difficulty in meeting the high-precision measurement requirements.

[0006] The contact thickness gauge directly contacts the substrate through a mechanical probe, which has the risk of damaging the substrate surface and contamination, and cannot realize online detection of moving substrates, so it has been gradually eliminated by the industry.

[0007] Therefore, the existing technology needs to be improved and developed. SUMMARY

[0008] The present application aims to provide a method for calculating the height of inkjet printing, which aims to solve the technical problem that the height of inkjet printing in the existing OLED inkjet printing equipment is difficult to measure accurately in real time during the printing process.

[0009] To achieve the above-mentioned purpose, the present application provides the following scheme: A method for calculating a height of a print, comprising: emitting, by a spectral confocal sensor, a polychromatic light to a substrate and a nozzle from a side of the substrate away from the nozzle, and receiving a first light signal reflected from a side of the substrate close to the nozzle and a second light signal reflected from the nozzle; determining a first focus wavelength focused on the side of the substrate close to the nozzle and a second focus wavelength focused on the nozzle and a nozzle incident angle based on the first light signal and the second light signal respectively, and inputting the first focus wavelength, the second focus wavelength and the nozzle incident angle into a pre-constructed refractive index calculation function to calculate a refractive index; inputting the first focus wavelength and the second focus wavelength into a pre-constructed initial thickness calculation function to calculate a theoretical height value of the substrate to the nozzle, and inputting the first focus wavelength and the second focus wavelength into a pre-trained error correction model to obtain an error compensation amount; obtaining an inclination angle of the substrate, and if the inclination angle of the substrate is not 0 degree, inputting the first focus wavelength, the second focus wavelength, the nozzle incident angle, the refractive index, the inclination angle, the theoretical height value and the error compensation amount into a pre-constructed first real thickness calculation function to calculate an actual height value of the substrate to the nozzle.

[0010] Preferably, after the obtaining the inclination angle of the substrate, the method further comprises: If the inclination angle of the substrate is 0 degree, inputting the first focus wavelength, the second focus wavelength, the nozzle incident angle, the refractive index, the theoretical height value and the error compensation amount into a pre-constructed second real thickness calculation function to calculate the actual height value of the substrate to the nozzle.

[0011] Preferably, the second real thickness calculation function is expressed as:

[0012] wherein, represents the actual height value of the substrate to the nozzle, represents the error compensation amount predicted and output by the error correction model based on the first focus wavelength and the second focus wavelength, represents the theoretical height value of the substrate to the nozzle, represents the nozzle incident angle, represents the first focus wavelength, represents the second focus wavelength, .

[0013] Preferably, the polychromatic light emitted by the spectral confocal sensor comprises a first monochromatic light and a second monochromatic light, the first monochromatic light is focused on the side of the substrate close to the nozzle, the second monochromatic light is focused on the nozzle, the first monochromatic light reflects the first light signal, and the second monochromatic light reflects the second light signal.

[0014] Preferably, the pre-constructed refractive index calculation function is expressed as:

[0015] In the formula, represents the refractive index, represents the first focusing wavelength, represents the second focusing wavelength, represents the nozzle incidence angle represents the focusing distance corresponding to the first focusing wavelength, represents the focusing distance corresponding to the second focusing wavelength, and h represents the thickness of the reference plate measured in the calibration experiment.

[0016] Preferably, the pre-constructed initial thickness calculation function is represented as: =

[0017] In the formula, represents the theoretical height value of the measured substrate to the nozzle, represents the focusing distance corresponding to the first focusing wavelength, represents the focusing distance corresponding to the second focusing wavelength.

[0018] Preferably, the pre-trained error correction model adopts a three-layer fully connected neural network. Preferably, the pre-trained error correction model includes an input layer, a hidden layer, and an output layer, the input layer includes two neurons for receiving the first focusing wavelength and the second focusing wavelength as input features; the hidden layer includes four neurons for fitting the nonlinear correlation between wavelength and error according to the input features; the output layer includes one neuron for mapping the nonlinear correlation between wavelength and error to a numerical value and outputting the error compensation amount.

[0019] Preferably, the first true thickness calculation function is represented as:

[0020]

[0021] In the formula, represents the actual height value of the measured substrate to the nozzle, represents the first focusing wavelength, represents the second focusing wavelength, represents the nozzle incidence angle represents the focusing distance corresponding to the first focusing wavelength, represents the focusing distance corresponding to the second focusing wavelength, represents the refraction angle of the monochromatic light corresponding to the second focusing wavelength in the complex light after being refracted by the side surface of the measured substrate close to the nozzle and then incident to the nozzle, represents the inclination angle of the measured substrate, represents an error compensation quantity predicted by the error correction model based on the first focusing wavelength and the second focusing wavelength, represents a refractive index.

[0022] The present application provides a multi-color light emitted from the nozzle side away from the substrate by using a spectral confocal sensor, which can penetrate the substrate to directly obtain the reflected light signal near the nozzle side and the nozzle surface, realizing non-contact cross-medium measurement, avoiding damage to the substrate and nozzle in contact measurement, and accurately positioning the target interface; moreover, the refractive index of the substrate is calculated by the focusing wavelength and the nozzle incident angle, the theoretical height value is obtained by combining the initial thickness function, the compensation quantity is obtained by introducing the pre-trained error correction model, and the corresponding real thickness calculation function is enabled according to the substrate inclination angle, forming a complete correction link of optical parameter calculation, theoretical value derivation, error compensation and inclination adaptation, which can effectively eliminate the measurement deviation caused by refraction, system implicit error and substrate inclination; in addition, the whole process is completed by optical signal and algorithm model to measure the height, without complex mechanical adjustment, with high measurement accuracy and strong adaptability, which can provide reliable height monitoring support for high-precision manufacturing scenes such as OLED printing. BRIEF DESCRIPTION OF DRAWINGS

[0023] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description are only some embodiments of the present application, and for those skilled in the art, other drawings can be obtained according to the structures shown in these drawings without creative labor.

[0024] Figure 1 is a flow chart of the printing height measurement calculation method provided by the embodiment of the present application; Figure 2 is a schematic diagram of the inclination of a transparent flat plate provided by the embodiment of the present application; Figure 3 is a schematic diagram of the thickness compensation principle provided by the embodiment of the present application. DETAILED DESCRIPTION

[0025] The terms "first", "second", "third", "fourth" and the like in the description and in the claims of the present application, if any, are used for distinguishing between similar objects and not necessarily for describing a particular sequential or chronological order. It is to be understood that the use of these terms herein is to be construed as interchangeable in order to comfort the embodiments described herein to be practiced in either order unless it is clear from the context that one technique precedes another technique. Furthermore, the terms "comprising", "having", "including", and the like, as well as any variations thereof, are intended to cover a non-exclusive inclusion such that a process, method, system, product, or apparatus that comprises, has, includes or includes elements or steps not expressly listed after such terms should not be excluded or denied.

[0026] For the purpose of facilitating understanding, the specific flow of the embodiments of the present application is described below, please refer to Figure 1 In the embodiments of the present application, a spray printing height measurement calculation method, S101, using a spectral confocal sensor to emit polychromatic light from the side of the measured substrate away from the nozzle to the measured substrate and the nozzle surface, and receive the first light signal reflected from the side of the measured substrate close to the nozzle and the second light signal reflected by the nozzle; S102, determining the first focusing wavelength focused on the side of the measured substrate close to the nozzle and the second focusing wavelength focused on the nozzle and the nozzle incident angle according to the first light signal and the second light signal respectively, and substituting the first focusing wavelength, the second focusing wavelength and the nozzle incident angle into the pre-constructed refractive index calculation function to calculate the refractive index; S103, substituting the first focusing wavelength and the second focusing wavelength into the pre-constructed initial thickness calculation function to calculate the theoretical height value of the measured substrate to the nozzle, and inputting the first focusing wavelength and the second focusing wavelength into the pre-trained error correction model to obtain the error compensation amount; S104, if the inclination angle of the measured substrate is not 0 degree, substituting the first focusing wavelength, the second focusing wavelength, the nozzle incident angle, the refractive index, the inclination angle, the theoretical height value and the error compensation amount into the pre-constructed first real thickness calculation function to calculate the actual height value of the measured substrate to the nozzle.

[0027] The height measurement calculation method of the printing height measurement of the embodiment adopts a spectral confocal sensor to emit polychromatic light from the side of the substrate away from the nozzle, can penetrate the substrate to directly obtain reflected light signals close to the nozzle side and the nozzle surface, realizes non-contact cross-medium measurement, avoids damage to the substrate and the nozzle in contact measurement, and can accurately position the target interface; moreover, the refractive index of the substrate is calculated by the focusing wavelength and the nozzle incident angle, the theoretical height value is obtained by combining the initial thickness function, the compensation amount is obtained by introducing the pre-trained error correction model, and the corresponding real thickness calculation function is enabled according to the substrate inclination angle, forming a complete correction link of optical parameter calculation, theoretical value derivation, error compensation and inclination adaptation, which can effectively eliminate the measurement deviation caused by refraction, system implicit error and substrate inclination; in addition, the whole process is completed by optical signals and algorithm models, without complex mechanical adjustment, and has high measurement accuracy and strong adaptability, which can provide reliable height monitoring support for high-precision manufacturing scenes such as OLED printing.

[0028] In the embodiment, in step S101, the polychromatic light emitted by the spectral confocal sensor includes first monochromatic light and second monochromatic light, the first monochromatic light is focused on the side of the measured substrate close to the nozzle, the second monochromatic light is focused on the nozzle, the first monochromatic light reflects the first light signal, and the second monochromatic light reflects the second light signal.

[0029] In the embodiment, the measurement light of the confocal sensor propagates along a predefined path, which is in turn vertical incidence and penetration of the measured substrate (first segment thickness), traversal of the environmental gas gap (second segment thickness, i.e. printing height), and finally arrival at the nozzle. It can be seen that the second segment thickness is defined by two planes, the first plane being the upper surface of the measured substrate and the second plane being the lower surface of the nozzle. That is, in the embodiment, the printing height can be determined by solving the second segment thickness.

[0030] In the embodiment, in step S102, it can be understood that the working principle of the spectral confocal sensor is that light of different wavelengths is focused at different distances. When the light is vertically incident on the measured surface, only the light of a specific wavelength that is focused on the surface will be reflected back to the sensor with high intensity. By analyzing the peak value of the reflected spectrum, the corresponding focusing wavelength of the surface can be determined.

[0031] In the embodiment, instead of directly determining the nozzle incident angle, the exit angle of the second monochromatic light in the air is determined. In the spectral confocal system, a specific wavelength λ corresponds to a specific exit angle, so after the second focusing wavelength is determined, the exit angle of the second monochromatic light, i.e. the nozzle incident angle, can be determined.

[0032] Let the first focusing wavelength be , the second focusing wavelength be , and the nozzle incident angle be , then the nozzle incident angle is expressed as:

[0033] are constant coefficients.

[0034] In the embodiment, a focusing distance-wavelength function formula between the focusing distance and the normalized wavelength is established by a polynomial fitting method, and the focusing distance-wavelength function formula is expressed as:

[0035] are constant coefficients.

[0036] In the embodiment, the function expression of the nozzle incident angle and the focusing distance-wavelength function formula are selected for the following reason: in precise measurement, in order to offset the lens edge distortion and the nonlinearity of the spectrometer itself, six is considered as the upper limit of balancing the fitting accuracy and the calculation stability. More than seven is easy to cause the Runge phenomenon, resulting in severe oscillation at the edge.

[0037] In the embodiment, The specific values of are obtained by experiment calibration combined with the least square method.

[0038] In the embodiment, the nozzle incident angle calibration method is to place the calibration object on a high-precision electric rotary table, at a series of preset angles, a series of standard distances (the distance from the sensor to the calibration object) are given by using a high-precision displacement table, the spectral peak wavelength in each state is recorded, and finally the size of is solved by the least square method.

[0039] ​​​​​​​​​​​​​​​​​​​​In the present embodiment, in the focusing distance-wavelength calibration process, a high-precision displacement table (such as a nanometer piezoelectric ceramic table) is used to give a series of standard distances (the distance from the sensor to the calibration object) along the axial direction, and the corresponding spectral peak wavelength is recorded, and finally the size of the focusing distance-wavelength calibration process is solved by the least square method.

[0040] In the present embodiment, the focusing distance corresponding to the first focusing wavelength is defined as , and the focusing distance corresponding to the second focusing wavelength is , and the pre-constructed refractive index calculation function is expressed as:

[0041] In the formula, h represents the thickness of the measured reference plate in the calibration experiment.

[0042] It should be noted that in the calibration experiment, the thickness of the measured reference plate is measured by using the remaining measurement method, and the specific values of the focusing wavelength, the incident angle and other variables are obtained, so that the real refractive index corresponding to different second focusing wavelengths is calculated, the real refractive index is fitted into a function, and the refractive index pre-calculation function is formed, and then stored in the software, which is convenient for subsequent calling.

[0043] In the present embodiment, in step S103, the pre-constructed initial thickness calculation function is expressed as: =

[0044] In the formula, is expressed as the theoretical height value of the measured substrate to the nozzle.

[0045] In the present embodiment, the first focusing wavelength and the second focusing wavelength are substituted into the pre-constructed initial thickness calculation function to calculate the theoretical height value of the measured substrate to the nozzle.

[0046] It can be understood that monochromatic light with a wavelength of is focused on the side of the measured substrate close to the nozzle; monochromatic light with a wavelength of is focused on the nozzle after being refracted by the side of the measured substrate close to the nozzle. If the refractive effect of the measured substrate is ignored (i.e. the refractive index is assumed to be 1), the wavelength should be focused on the unrefracted point on the optical axis. The unrefracted point is located between the measured substrate and the nozzle, and the thickness calculated under this condition is , that is, the axial distance between the two wavelength focusing points, representing the initial thickness without refractive compensation.

[0047] ​In the actual measurement process, there are also various error sources in the embodiment, including but not limited to focusing error of the confocal optical system, installation and manufacturing tolerance of the workpiece (such as installation error of the measuring device), and random error caused by environmental factors (such as environmental noise, air flow disturbance, light source instability and operator intervention, etc.). The above errors belong to non-systematic errors. In order to further improve the measurement accuracy and compensate for non-systematic errors, the error correction model based on neural network is introduced in the scheme. The non-systematic error not covered in the initial theoretical height value is corrected through the error correction model, so that the measurement error of the final actual height value is ≤±0.1 μm. The error correction model takes the focusing wavelength 、 as input, learns and predicts complex error characteristics, and outputs error compensation .

[0048] In the embodiment, the error correction model adopts a three-layer fully connected neural network. The error correction model includes an input layer, a hidden layer and an output layer. The input layer includes two neurons for receiving the first focusing wavelength and the second focusing wavelength as input features. The hidden layer includes four neurons for fitting the nonlinear relationship between the wavelength and the error according to the input features. The output layer includes one neuron for mapping the nonlinear relationship between the wavelength and the error to a numerical value and outputting the error compensation . The hidden layer uses the ReLU activation function, and the output layer uses the linear activation function.

[0049] In the embodiment, the experimental data is obtained as training samples to train and optimize the fully connected neural network, and the pre-trained error correction model is obtained.

[0050] Each group of training samples includes input features and label values. The input features are the measured values of the first focusing wavelength (unit: nm) and the second focusing wavelength (unit: nm), and the label values are the differences between the actual printing height true value and the initial theoretical height value (i.e. the true value of the error compensation); wherein the actual printing height true value is obtained by the high-precision laser interferometer (measurement accuracy ±0.05 μm), and the initial theoretical height value is obtained by the initial thickness calculation function. A total of 1000 samples (covering the commonly used measurement range of λ1 ∈ [500~550nm], λ2 ∈ [600~650nm]) are collected.

[0051] In the embodiment, in step S104, it can be understood that in actual application, if the measured substrate produces inclination, the incident light will no longer be ideal specular reflection, especially under a larger inclination angle, which will cause the spectral signal to shift and affect the thickness calculation accuracy. Even a small angle inclination will also affect the measurement result, therefore, if the inclination angle of the measured substrate is not 0 degrees, the first real thickness calculation function is used to calculate the actual height value of the measured substrate to the nozzle. The first real thickness calculation function introduces inclination compensation on the basis of error compensation.

[0052] The first real thickness calculation function is represented as:

[0053]

[0054] In the formula, h represents the actual height value of the measured substrate to the nozzle, represents the actual height value of the measured substrate to the nozzle, represents the refraction angle, represents the inclination angle of the measured substrate, represents the error compensation amount predicted by the error correction model based on the first focusing wavelength and the second focusing wavelength.

[0055] In the embodiment, the inclination angle of the measured substrate is measured by an inclinometer.

[0056] Specifically, when constructing the first real thickness calculation function formula, taking a transparent flat plate as an example, as shown in FIG. 1, which is a schematic diagram of the inclination of the transparent flat plate. Figure 2

[0057] The focusing wavelengths of the upper and lower surfaces of the transparent flat plate remain unchanged, which are and respectively, and the peak wavelength drift caused by the inclination is ignored. The direction of the optical axis is denoted as , represents the upper surface when not inclined, which is parallel to the normal line of the optical axis; represents the inclined surface of the upper surface with a deflection angle of around point A relative to the normal direction, and it is assumed that the lower surface is parallel to the upper surface, and the inclination angle is also .

[0058] The spectral confocal sensor (i.e., the confocal probe) emits monochromatic light with a wavelength of at an incident angle of to focus on point A, and light with a wavelength of at an angle of focuses on point C of the un-inclined surface, which corresponds to point B of the upper surface after inclination. If refraction is not considered, the light should focus on point E on the optical axis; and actually, due to the refractive index of the material , the light is refracted to point F on the upper surface.​ refracted angle incident to the lower surface , and finally focus on point D, the angle between the light and the optical axis is . represents the real thickness of the transparent plate when the focusing wavelength is constant on the upper and lower surfaces of the transparent plate, represents and the difference between the monochromatic light focusing distance and the plate measurement thickness, represents the path of the refracted light in the transparent plate, and respectively represent the distance of straight line AC and the length of AB projection on the normal of the optical axis, and respectively represent the distance of straight line AB perpendicular to point A and point B.

[0059] According to the geometric relationship, the following relationship is obtained:

[0060]

[0061] The refracted angle can be obtained as follows:

[0062] In addition, according to the geometric relationship, the following relationship is obtained:

[0063]

[0064]

[0065]

[0066]

[0067] From the analysis, the real thickness of the transparent plate Figure 2 , the measurement thickness of the transparent plate , the real thickness of the transparent plate can be solved , wherein is expressed as:

[0068] The real thickness expression of the tilt compensation can be finally derived as:

[0069] Finally, the error compensation amount ​The first real thickness calculation function is obtained by incorporating the tilt compensation into the real thickness expression.

[0070] In the embodiment, if the tilt angle of the measured substrate is 0 degree, the first focus wavelength, the second focus wavelength, the nozzle incident angle, the refractive index, the theoretical height value and the error compensation amount are substituted into the pre-constructed second real thickness calculation function to calculate the actual height value of the measured substrate to the nozzle.

[0071] In the embodiment, since the material has a certain refractive index in the actual situation , the theoretical height value needs to be corrected to obtain the actual height value of the measured substrate to the nozzle.

[0072] Specifically, in order to eliminate the measurement error caused by the refraction effect, the second real thickness calculation function is constructed.

[0073] The second real thickness calculation function is expressed as:

[0074] In the formula, represents the actual height value of the measured substrate to the nozzle, represents the error compensation amount predicted and output by the error correction model based on the first focus wavelength and the second focus wavelength.

[0075] In the embodiment, Figure 3 the principle of thickness compensation is illustrated by taking a transparent plate as an example. According to the refraction law, the incident angle of the lower surface is . is the theoretical incident angle. Since the upper surface of the transparent plate refracts the light once, the light finally reaching the lower surface will be emitted at an actual incident angle of .

[0076]

[0077] Considering that the refractive index of air is approximately 1, i.e. , the incident angle of the lower surface is expressed as:

[0078] According to the geometric relationship, the incident angle and the exit angle satisfy the following formulas respectively:

[0079]

[0080] In the formula, is the radial displacement of the focus spot.

[0081] The actual thickness calculation function is derived by combining the above relationships, and is expressed as:

[0082] Finally, the error compensation amount is incorporated into the actual thickness calculation function to obtain a second true thickness calculation function.

[0083] The following will combine a specific OLED glass substrate spray printing height measurement scene to fully demonstrate the actual application process of the method, so that you can intuitively understand the operation and calculation logic of each step: I. The completed pre-calibration parameters are as follows:

[0084]

[0085] Object to be measured: OLED glass substrate for spray printing (inclination angle =1°), which needs to measure the spray printing height of the surface close to the nozzle side to the nozzle surface.

[0086] II. Specific measurement steps 1. Light signal acquisition Start the spectral confocal sensor, emit polychromatic light from the side of the glass substrate away from the nozzle, and receive the first light signal of the surface close to the nozzle side of the glass substrate and the second light signal of the nozzle surface after the light penetrates the glass substrate.

[0087] 2. Determine the key optical parameters By analyzing the light intensity peak value of the light signal, the first focusing wavelength (substrate close to nozzle side) (λ1=520nm) and the second focusing wavelength (nozzle surface) (λ2=610nm) are obtained Substitute the incident angle function to calculate the nozzle incident angle Get 3.2°.

[0088] 3. Calculate the refractive index Substitute λ1=520nm, λ2=610nm and =3.2° into the pre-constructed refractive index calculation function to calculate the refractive index =1.51.

[0089] 4. Calculate the theoretical height value Substitute λ1=520nm, λ2=610nm into the pre-constructed initial thickness calculation function to obtain =304μm.

[0090] 5. Obtain the error compensation amount Substitute λ1=520nm, λ2=610nm into the pre-trained error correction model to obtain the compensation amount = -0.52 μm.

[0091] 6. Calculate the actual printing height under the tilt condition Known substrate tilt angle = 1°, according to the calculation .

[0092] Again, substitute the first true thickness calculation function to calculate the actual height value as 547.98 μm.

[0093] The above only describes the preferred embodiments of the present application, and does not limit the patent scope of the present application. Any equivalent structural transformation, direct / indirect application in other related technical fields, or use of the content of the present application specification and drawings under the inventive concept of the present application is included in the patent protection scope of the present application.

Claims

1. A method for measuring and calculating printing height, characterized in that, The method comprises: emitting a complex light from a side of a measured substrate away from a nozzle to the measured substrate and the nozzle surface by a spectral confocal sensor, and receiving a first light signal reflected from a side of the measured substrate close to the nozzle and a second light signal reflected from the nozzle; determining a first focusing wavelength focused on the side of the measured substrate close to the nozzle and a second focusing wavelength and a nozzle incident angle focused on the nozzle according to the first light signal and the second light signal respectively, and substituting the first focusing wavelength, the second focusing wavelength and the nozzle incident angle into a pre-constructed refractive index calculation function to calculate the refractive index; substituting the first focusing wavelength and the second focusing wavelength into a pre-constructed initial thickness calculation function to calculate a theoretical height value of the measured substrate to the nozzle, and inputting the first focusing wavelength and the second focusing wavelength into a pre-trained error correction model to obtain an error compensation amount; obtaining an inclination angle of the measured substrate, and if the inclination angle of the measured substrate is not 0 degrees, substituting the first focusing wavelength, the second focusing wavelength, the nozzle incident angle, the refractive index, the inclination angle, the theoretical height value and the error compensation amount into a pre-constructed first real thickness calculation function to calculate an actual height value of the measured substrate to the nozzle.

2. The spray height measurement calculation method of claim 1, wherein, After the inclination angle of the measured substrate is obtained, the method further comprises: if the inclination angle of the measured substrate is 0 degrees, substituting the first focusing wavelength, the second focusing wavelength, the nozzle incident angle, the refractive index, the theoretical height value and the error compensation amount into a pre-constructed second real thickness calculation function to calculate an actual height value of the measured substrate to the nozzle.

3. The spray height measurement calculation method of claim 2, wherein, The second real thickness calculation function is expressed as: In the formula, represents an actual height value of the measured substrate to the nozzle, represents an error compensation amount predicted by the error correction model based on the first focus wavelength and the second focus wavelength, represents a theoretical height value of the measured substrate to the nozzle, represents a nozzle incidence angle, represents a first focus wavelength, represents a second focus wavelength, .

4. The spray height measurement calculation method of claim 1, wherein, The complex light emitted by the spectral confocal sensor comprises a first monochromatic light and a second monochromatic light, the first monochromatic light is focused on the side of the measured substrate close to the nozzle, the second monochromatic light is focused on the nozzle, the first monochromatic light reflects the first light signal, and the second monochromatic light reflects the second light signal.

5. The spray height measurement calculation method of claim 1, wherein, The pre-constructed refractive index calculation function is expressed as: wherein n represents the refractive index, λ1 represents the first focusing wavelength, λ2 represents the second focusing wavelength, θ represents the nozzle incident angle f1 represents the focusing distance corresponding to the first focusing wavelength, f2 represents the focusing distance corresponding to the second focusing wavelength, and h represents the thickness of the reference plate measured in the calibration experiment.

6. The drop height measurement calculation method of claim 1, wherein, The pre-constructed initial thickness calculation function is expressed as: = In the formula, represents the theoretical height value of the measured substrate to the nozzle, represents the focusing distance corresponding to the first focusing wavelength, represents the focusing distance corresponding to the second focusing wavelength.

7. The spray height measurement calculation method of claim 1, wherein, The pre-trained error correction model adopts a three-layer fully connected neural network.

8. The spray height measurement calculation method of claim 7, wherein, The pre-trained error correction model comprises an input layer, a hidden layer and an output layer, the input layer comprises two neurons for receiving the first focusing wavelength and the second focusing wavelength as input features, the hidden layer comprises four neurons for fitting a nonlinear correlation between the wavelength and the error according to the input features, and the output layer comprises one neuron for mapping the nonlinear correlation between the wavelength and the error to a numerical value and outputting the error compensation amount.

9. The spray height measurement calculation method of claim 1, wherein, The first real thickness calculation function is expressed as: In the formula, represents the actual height value of the measured substrate to the nozzle, represents the first focusing wavelength, represents the second focusing wavelength, represents the nozzle incidence angle represents the focusing distance corresponding to the first focusing wavelength, represents the focusing distance corresponding to the second focusing wavelength, represents the refraction angle of the monochromatic light corresponding to the second focusing wavelength in the complex color light after being refracted by the side surface of the measured substrate close to the nozzle and then being incident to the nozzle, represents the inclination angle of the measured substrate, represents the error compensation amount predicted and output by the pre-trained error correction model based on the first focusing wavelength and the second focusing wavelength, represents the refractive index.

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