CN114019590B - Calculation method and control method of coating film strain of ultrathin lens and ultrathin lens - Google Patents
Calculation method and control method of coating film strain of ultrathin lens and ultrathin lens Download PDFInfo
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- G02B1/10—Optical coatings produced by application to, or surface treatment of, optical elements
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Abstract
The invention discloses a method for calculating coating strain of an ultrathin lens, a control method thereof and the ultrathin lens, wherein the coating strain calculation comprises the following steps: obtaining a relation model between the coating stress and the thickness of a film material required by the ultrathin lens, solving the corresponding coating stress according to the required thickness of each film, and calculating the coating stress of the ultrathin lens according to an improved Stoneley formula so as to obtain the strain of the coating to the substrate; coating strain control: based on the stress of the coating layer of the ultrathin lens, a metal oxide film layer is designed, the vector sum of the coating stress and the stress of the coating layer is smaller than a preset stress threshold, the designed metal oxide film layer is added into the coating layer of the ultrathin lens, and the control of the coating stress is realized. The method can predict and control the strain of the ultrathin lens in the film coating process to obtain the strain-free ultrathin lens after film coating.
Description
Technical Field
The invention belongs to the technical field of optical films, and particularly relates to a calculation method of coating film strain of an ultrathin lens, a control method of the calculation method and the ultrathin lens.
Background
Optical coating is a process of coating various optical films on optical glass by using a vacuum coating machine, and the optical films play an important role in an optical system. Fraunhofer produced, as early as 1827, the first antireflection films, which he formed by etching half of a finely polished flat glass in concentrated sulfuric or nitric acid. Single-layer antireflection films were prepared by vacuum evaporation successively from pall in germany and streun in the united states in the middle of the thirties in the twentieth century, and such simple antireflection films have been used in large quantities in general optical devices so far.
When light is emitted to the interface of two transparent media, if the light is emitted to the light-thinning medium from the optically dense medium, the light is likely to be totally reflected; when light is emitted from the optically thinner medium to the optically denser medium, the reflected light has half-wave loss. The refractive index of the anti-reflection film on the glass lens is between that of glass and air, and when light is emitted to the lens from air, the reflected light on two surfaces of the film has half-wave loss, so that the thickness of the film only meets the requirement that the optical path difference of the two reflected light is half wavelength. The reflected light on the back surface of the film travels more than the reflected light on the front surface, i.e., twice the thickness of the film. Therefore, the film thickness should be 1/4 the wavelength of light in the thin film medium so that the two reflected lights cancel each other and increase the light transmission. Nowadays, the infrared optical film is widely applied to the fields of daily life, industry, astronomy, military science, electronics and the like, has wide market prospect, can effectively improve the conversion efficiency of the battery, and can improve the mechanical property, the electrical property, the optical property and other physical and chemical properties of a matrix.
The coating method used by the existing infrared optical coating technology can cause the film above the substrate to have larger stress residual, and because the film is generally thinner and the substrate is generally a rigid body such as glass, the residual stress of the film can not cause obvious strain on the general lens.
However, for substrates having a thickness of 0.1mm (and below), the stresses generated by infrared optical coating techniques are sufficient to cause significant strain, resulting in a finished optical lens exhibiting a certain curvature. The curvature of the lens will cause focusing and diverging of the transmitted or reflected light through the lens and ultimately lead to a reduction in the overall performance of the optical element.
With the progress of technology, there is a trend of miniaturization of optical elements such as mobile phone lenses, and therefore, there is a need for a method for calculating and controlling the total strain of the lens during the coating process of the ultra-thin infrared lens with a thickness of 0.1mm (or less).
Disclosure of Invention
The invention provides a calculation method and a control method for coating strain of an ultrathin lens and the ultrathin lens, which can predict and control the strain of the ultrathin lens in a coating process to obtain the ultrathin lens without strain after coating.
In order to achieve the technical purpose, the invention adopts the following technical scheme:
a method for calculating the coating strain of an ultrathin lens is disclosed, wherein the ultrathin lens is a lens with the thickness not more than 0.1 mm; the method comprises the following steps:
step A1, the required second for ultra-thin lenses
A film layer material obtained byA relation model between coating stress and thickness;
，
the number of film layers required by the ultrathin lens;
step A2, obtaining the first step required by the ultra-thin lens
Thickness of each film layer
Solving the film coating stress of the film layer based on the film coating stress and thickness relation model of the film layer material
；
；
Step A3, according to the film coating stress of each film layer required by the ultrathin lens, calculating the film coating stress of the ultrathin lens according to the following relational expression
：
In the formula (I), the compound is shown in the specification,
the Young modulus, Poisson's ratio and thickness of the substrate of the ultrathin lens respectively,
the radius of the film coating area;
and A4, solving the strain of the coating layer of the ultrathin lens to the substrate according to the coating layer stress of the ultrathin lens.
Further, the relation model of the coating stress and the thickness of each film material is as follows:
in the formula (I), the compound is shown in the specification,Fanddrespectively represents the coating stress and the thickness of any film layer material,
as in a relational modelm+1 coefficients; obtaining a relation model between the coating stress and the thickness of each film material, namely solving coefficients in the relation model
The solving method comprises the following steps:
for each film material, obtaining the stress of the film material with different thicknesses after film coating on the substrate, obtaining a group of coating stress and thickness data for each thickness, inputting all data groups into a relation model with unknown coefficients, and performing fitting calculation by adopting a partial least square method to obtain the coefficient of the relation model of the film material
。
Further, the calculation formula for solving the strain in step a4 is:
in the formula (I), the compound is shown in the specification,
coating film for ultrathin lensThe amount of strain of the layer to the substrate,Ethe Young's modulus of the coating layer is shown.
A control method of coating film strain of an ultrathin lens is disclosed, wherein the ultrathin lens is a lens with the thickness not more than 0.1 mm; the control method of the coating film strain comprises the following steps:
step B1, adopting the steps A1 to A3 of the technical scheme of the calculation method for the coating strain of any ultrathin lens, and solving the stress of the coating layer of the ultrathin lens
；
Step B2, designing a metal oxide film layer, wherein the vector sum of the film coating stress and the film coating stress of the ultrathin lens is less than a preset stress threshold;
and step B3, adding the designed metal oxide film layer into the coating layer of the ultrathin lens in the coating process of the ultrathin lens.
Further, when the metal oxide film layer is designed in the step B2:
firstly, preselecting a metal oxide material, and calculating a relation model between the coating stress and the thickness of the metal oxide film layer material according to the same method in the step A1 of the technical scheme of the method for calculating the coating strain of any ultrathin lens;
and then inputting a stress numerical value which is opposite to the stress of the coating layer into the relation model, and solving the thickness of the metal oxide film layer, wherein the metal oxide film layer with the thickness is the metal oxide film layer required by design.
An ultrathin lens is a lens with the thickness not greater than 0.1mm and comprises a substrate, a metal oxide film layer and a coating layer, wherein the coating layer comprises a plurality of functional film layers, and the functional film layers are film layers for realizing the functions of the lens; the sum of the stress vectors of the metal oxide film layer and the coating layer is less than a preset stress threshold; the metal oxide film layer is designed by adopting the control method of the coating film strain of the ultrathin lens.
In a more preferred ultra-thin lens solution, the ultra-thin lens is an infrared lens.
Advantageous effects
1. According to the method, the laser interference data of the strain of the coated materials with different thicknesses after coating is extracted, and then the relation model between the thickness and the stress of various coated materials is obtained through partial least squares regression and polynomial fitting, so that the stress data of the coated materials in the thickness of the film layer required by the ultrathin lens can be obtained, the strain of the ultrathin lens in the coating process is calculated and predicted, the technical obstacle caused by the strain in the existing infrared optical coating technology is solved, and the quantitative analysis of the total strain of the infrared optical film lens after coating is realized.
2. By utilizing the calculation model and the control method constructed by the invention, the strain prediction data of the ultrathin lens after the infrared optical coating process can be predicted, and on the basis of the strain prediction data, the metal oxide film is designed through reverse stress, so that the strain-free ultrathin infrared optical lens is realized.
3. In addition, by designing the balance between the reverse stress of the metal oxide film and the stress of the original film system of the infrared optical coating, the ultrathin infrared optical lens with a specific shape can be realized.
Drawings
Fig. 1 is a schematic view of an ultra-thin infrared lens according to an embodiment of the present disclosure.
Note: the figure is a schematic diagram, wherein the proportion of each part in the figure is not true proportion; wherein, 1 is a substrate of the ultrathin lens; 2 is a reverse stress metal oxide film layer; and 3 is the sum of all the existing film layers of the ultrathin lens.
Detailed Description
The following describes embodiments of the present invention in detail, which are developed based on the technical solutions of the present invention, and give detailed implementation manners and specific operation procedures to further explain the technical solutions of the present invention.
Example 1
step A1, fourth required for ultra-thin lenses
Obtaining a relation model between the coating stress and the thickness of each film layer material;
and n is the number of film layers required by the ultrathin lens.
The film material required by the ultrathin lens is determined according to the optical property requirement required by the product and is responsible for forming specific spectral properties in the product.
The relationship between the thickness of the coating material and the strain in different film systems has a certain degree of non-linear dependence. Therefore, in this embodiment, for each film material, a relationship model between the coating stress and the thickness is established as follows:
in the formula (I), the compound is shown in the specification,Fanddrespectively represents the coating stress and the thickness of any film layer material,
as in a relational modelm+1 coefficients; obtaining a relation model between the coating stress and the thickness of each film material, namely solving coefficients in the relation model
The solving method comprises the following steps:
for each film material, obtaining the stress of the film material with different thicknesses after film coating on the substrate, obtaining a group of coating stress and thickness data for each thickness, inputting all data groups into a relation model with unknown coefficients, and performing fitting calculation by adopting a partial least square method to obtain the coefficient of the relation model of the film material
。
In this embodiment, the film coating stress of the film layer materials with various thicknesses on the substrate is obtained by acquiring strained laser interference data by using a laser interferometer, and abnormal data such as data jitter, error data, equipment errors and the like are inevitably obtained.
Step A2, obtaining the first step required by the ultra-thin lens
Thickness of each film layer
Solving the film coating stress of the film layer based on the film coating stress and thickness relation model of the film layer material
；
。
Step A3, calculating the stress of the coating layer of the ultrathin lens according to the following improved Stoneley formula according to the coating stress of each layer required by the ultrathin lens
：
In the formula (I), the compound is shown in the specification,
the Young modulus, Poisson's ratio and thickness of the substrate of the ultrathin lens respectively,
is the radius of the coating area.
Different film layers of the ultrathin lens interfere with each other, and the film layers of all components may have different stress combination degrees to a certain extent, so that the accuracy of stress analysis of a film coating layer of the ultrathin lens is influenced. Therefore, the quantitative analysis method is adopted in the embodiment, on one hand, a partial least squares regression + polynomial fitting mode is added to reduce errors of input data, on the other hand, the improved Stoneley formula correlation model is used for calculating and predicting the post-coating strain of the infrared optical lens, and the accuracy of calculation of the coating layer stress of the ultrathin lens is improved.
Step A4, according to the stress of the coating layer of the ultrathin lens, solving the strain of the coating layer of the ultrathin lens to the substrate by Hooke's law, wherein the calculation formula is as follows:
in the formula (I), the compound is shown in the specification,
the strain of the coating layer of the ultrathin lens to the substrate is large, and E represents the Young modulus of the coating layer.
Example 2
step B1, using steps A1 through A3 of the method of example 1, to determine the coating stress of the ultra-thin lens
；
Step B2, designing a metal oxide film layer, wherein the vector sum of the film coating stress and the film coating stress of the ultrathin lens is less than a preset stress threshold;
and step B3, adding the designed metal oxide film layer into the coating layer of the ultrathin lens in the coating process of the ultrathin lens.
In a more preferred embodiment, when the metal oxide film layer is designed in step B2: firstly, preselecting a metal oxide material, and calculating a relation model between the coating stress and the thickness of the metal oxide film layer material according to the same method as the step A1 in the embodiment 1; and then inputting a stress numerical value which is opposite to the stress of the film coating layer into the relation model, and solving the thickness of the metal oxide film layer, wherein the metal oxide film layer with the thickness is the metal oxide film layer required by design.
The coating layer in the invention refers to the sum of all film layers of the ultrathin lens in the prior art and is also called as the prior film layer. Because the existing film layer can cause certain stress residue in the film coating process, the stress can cause certain strain according to the Hooke law mentioned above. Therefore, in the implementation, a metal oxide film layer is designed and added to the existing film layer, and the metal oxide film layer is designed according to two principles, on one hand, the metal oxide film layer needs to show stress opposite to that of the existing film layer as much as possible so as to reduce or even eliminate stress residue which may appear originally, and on the other hand, the metal oxide film layer shows spectral properties in a designed waveband as small as possible, so that the optical properties of the total film layer after the metal oxide film layer is added are consistent with those before the metal oxide film layer is added. Therefore, the final total film layer is greatly reduced in strain because the residual stress of the original film is mostly offset, and the control of the coating strain of the ultrathin lens is finally realized.
Example 3
The above embodiments are preferred embodiments of the present application, and those skilled in the art can make various changes or modifications without departing from the general concept of the present application, and such changes or modifications should fall within the scope of the claims of the present application.
Claims (6)
1. A method for calculating the coating strain of an ultrathin lens is disclosed, wherein the ultrathin lens is a lens with the thickness not more than 0.1 mm; it is characterized by comprising:
step A1, the required second for ultra-thin lenses
Obtaining a relation model between the coating stress and the thickness of each film layer material;
，
the number of film layers required by the ultrathin lens;
the relation model of the coating stress and the thickness of each film material is as follows:
in the formula (I), the compound is shown in the specification,Fanddrespectively represents the coating stress and the thickness of any film layer material
As in a relational modelm+1 coefficients; obtaining a relation model between the coating stress and the thickness of each film material, namely solving coefficients in the relation model
The solving method comprises the following steps:
for each film material, acquiring the stress of the film materials with different thicknesses after film coating on the substrate, wherein each thicknessObtaining a group of coating stress and thickness data, inputting all the data groups into a relation model with unknown coefficients, and performing fitting calculation by adopting a partial least square method to obtain the relation model coefficients of the film material
；
Step A2, obtaining the first step required by the ultra-thin lens
Thickness of each film layer
Solving the film coating stress of the film layer based on the film coating stress and thickness relation model of the film layer material
；
；
Step A3, according to the film coating stress of each film layer required by the ultrathin lens, calculating the film coating stress of the ultrathin lens according to the following relational expression
：
In the formula (I), the compound is shown in the specification,
the Young modulus, Poisson's ratio and thickness of the substrate of the ultrathin lens respectively,
the radius of the film coating area;
and A4, solving the strain of the coating layer of the ultrathin lens to the substrate according to the coating layer stress of the ultrathin lens.
2. The method of claim 1, wherein the calculation of step a4 to solve for strain is:
in the formula (I), the compound is shown in the specification,
the strain of the coating layer of the ultrathin lens to the substrate is large,
the Young's modulus of the coating layer is shown.
3. A control method of coating film strain of an ultrathin lens is disclosed, wherein the ultrathin lens is a lens with the thickness not more than 0.1 mm; the method is characterized by comprising the following steps:
step B1 of using steps A1 through A3 of the method of claim 1 to solve for coating stress of ultra-thin lenses
；
Step B2, designing a metal oxide film layer, wherein the vector sum of the film coating stress and the film coating stress of the ultrathin lens is less than a preset stress threshold;
and step B3, adding the designed metal oxide film layer into the coating layer of the ultrathin lens in the coating process of the ultrathin lens.
4. The method of claim 3, wherein when designing the metal oxide film layer in step B2:
first preselecting a metal oxide film material, and calculating a relation model between the coating stress and the thickness of the metal oxide film material according to the same method as that of step a1 in the method of any one of claims 1 to 2;
and then inputting a stress numerical value which is opposite to the stress of the coating layer into the relation model, and solving the thickness of the metal oxide film layer, wherein the metal oxide film layer with the thickness is the metal oxide film layer required by design.
5. An ultrathin lens is characterized in that the ultrathin lens is a lens with the thickness not greater than 0.1mm and comprises a substrate, a metal oxide film layer and a coating layer, wherein the coating layer comprises a plurality of functional film layers, and the functional film layers are film layers for realizing the functions of the lens; the sum of the stress vectors of the metal oxide film layer and the coating layer is less than a preset stress threshold; the metal oxide film layer is designed by the method for controlling the coating strain of the ultrathin lens according to any one of claims 3 or 4.
6. The ultra-thin lens of claim 5, wherein the ultra-thin lens is an infrared lens.
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| CN1749782A (en) * | 2004-09-17 | 2006-03-22 | 鸿富锦精密工业（深圳）有限公司 | The coated glass eyeglass |
| CN100494929C (en) * | 2007-04-03 | 2009-06-03 | 中国科学院上海光学精密机械研究所 | Method and apparatus for measuring thin-film stress |
| CN101629859B (en) * | 2009-05-04 | 2011-04-20 | 付康 | System and method for determining thin-film stress based on deformation measurement and numerical reverse |
| CN104729897B (en) * | 2015-02-11 | 2020-04-17 | 中国人民解放军装甲兵工程学院 | Non-residual stress film, preparation method thereof and application thereof in nano-indentation method |
| US9864105B2 (en) * | 2015-05-28 | 2018-01-09 | Northwestern University | Stress manipulated coating for figure reshape of optical substrates |
| JP7188754B2 (en) * | 2019-01-17 | 2022-12-13 | 東海光学株式会社 | Warp prediction method and program for optical products |
| CN111399103B (en) * | 2020-04-22 | 2023-07-18 | 杭州科汀光学技术有限公司 | Low-stress multilayer thin film optical filter and preparation method thereof |
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