A method for designing a microscope objective medium and a detection device for its application

Abstract

The present application provides a method for designing an object medium of a microscope objective lens and a detection device using the same. For a microscope objective lens in the field of industrial detection that uses a refractive index medium as an object medium, the medium type is set to a virtual material. The virtual material has a characteristic that the change in refractive index with wavelength is exactly opposite to that of a conventional material. As long as the sample refractive index curve intersects with the virtual material refractive index slope, the wavelength at the intersection can be set to the working wavelength, the refractive index at the intersection can be set to the working refractive index, and then the corresponding refractive index matching liquid can be customized, so that the detection device can adapt to sample types with a wider refractive index range. The present invention can solve the problem of expanding the application scope of the measurement device when the refractive index matching method is used for high-precision scanning detection in samples, so that a set of hardware can be compatible with almost all samples.

Description

Technical Field

[0001] The present invention relates to the field of microscopic detection technology, and in particular to a design method for a microscope objective medium and detection equipment using the same. Background Art

[0002] Currently, most optical systems for industrial microscopic inspection use microscopic systems, which use the high resolution of microscope objective lenses to achieve high-precision inspection of microscopic defects or features of products.

[0003] However, the higher the resolution of the microscope, the larger the NA must be, so the depth of field is smaller, and there is a contradiction between the two indicators of resolution and depth of field. Therefore, industrial microscopic inspection equipment can only detect the surface of the component to be inspected, but cannot detect the internal defects of the component.

[0004] Since existing microscopic inspection equipment cannot detect internal defects of components, a long working distance immersion objective can be designed to match the refractive index with the sample to be tested, thereby achieving internal scanning of the sample. However, the types and range of samples that can be measured by this method system are limited by the refractive index, and there is a problem of limited measurable range of the objective. Summary of the invention

[0005] The purpose of the present invention is to propose a design method for an objective lens with strong adaptability and capable of testing a wider range of samples. For a microscope objective lens in the field of industrial detection that uses a refractive index medium as an object medium, the medium type is set to a virtual material. The virtual material has a characteristic that the change in refractive index with wavelength is exactly opposite to that of a conventional material, so that the detection equipment can adapt to sample types with a wider refractive index range.

[0006] This application adopts the following technical solutions: A method for designing a microscope objective medium comprises the following steps: The object medium of the microscope objective is set as a virtual material, and the refractive index of the virtual material increases linearly and monotonically with the wavelength; Determine the intersection point of the sample refractive index curve and the virtual material refractive index oblique line, set the wavelength at the intersection point as the working wavelength, and set the refractive index at the intersection point as the working refractive index; According to the working wavelength and working refractive index, the corresponding refractive index matching liquid is customized.

[0007] Another object of the present application is to provide a microscopic internal defect detection device for a microscope, which is applied to the above-mentioned method for designing an object medium of a microscope objective lens, including a microscope objective lens, wherein the object surface of the microscope objective lens is immersed in a refractive index matching liquid, the refractive index of the refractive index matching liquid matches that of the sample to be tested, and the object surface of the microscope objective lens can be moved relative to the sample to be tested so that the microscope objective lens can be focused to different heights inside the sample to be tested.

[0008] Compared with the prior art, the present invention has the following beneficial effects: The present application provides a method for designing an object medium of a microscope objective lens and a detection device using the same. For a microscope objective lens in the field of industrial detection that uses a refractive index medium as an object medium, the medium type is set to a virtual material. The virtual material has a characteristic that the change in refractive index with wavelength is exactly opposite to that of a conventional material. As long as the sample refractive index curve intersects with the virtual material refractive index slope, the wavelength at the intersection can be set to the working wavelength, the refractive index at the intersection can be set to the working refractive index, and then the corresponding refractive index matching liquid can be customized, so that the detection device can adapt to sample types with a wider refractive index range. The present invention can solve the problem of expanding the application scope of the measurement device when the refractive index matching method is used for high-precision scanning detection in samples, so that a set of hardware can be compatible with almost all samples. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 It is a structural schematic diagram of an existing microscopic detection device; Figure 2 This is a structural schematic diagram of a microscopic optical internal microscopic defect detection device embodiment 1 of the present application; Figure 3 This is a structural schematic diagram of a microscopic optical internal microscopic defect detection device embodiment 2 of the present application; Figure 4 (a) is a schematic diagram of the refractive index matching method of the objective lens in this application scheme; Figure 5 (b) is a schematic diagram of a method for matching the refractive index of an objective lens in the present application; Figure 6 To adopt Figure 4 Schematic diagram of the testable sample range of scheme (a); Figure 7 To adopt Figure 5 Schematic diagram of the testable sample range of scheme (b); Figure 8 The figure is a schematic diagram of the measurable sample range of a microscope objective lens object medium design method according to an embodiment. DETAILED DESCRIPTION

[0010] In order to make the technical problems, technical solutions and beneficial effects solved by the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0011] See also Figure 1-3 , Figure 1 It is the structure of conventional microscopic detection equipment; Figure 2 is the detection structure of the detection device of embodiment 1 of the present invention; Figure 3This is the detection structure of the detection device of Example 2 of the present invention; in the figure, 1-microscope objective lens, 2-sample to be detected, 3-air, 4-refractive index matching liquid, 5-window plate; the black and white lines in the sample are schematic diagrams of internal defects.

[0012] An embodiment of the present application provides a microscopic internal microscopic defect detection device, including a microscope objective lens 1, wherein the object surface of the microscope objective lens 1 is immersed in a refractive index matching liquid 4, the refractive index of the refractive index matching liquid 4 matches that of a sample to be tested 2, and the object surface of the microscope objective lens 1 can be moved relative to the sample to be tested 2 so that the microscope objective lens 1 can be focused to different heights inside the sample to be tested 2.

[0013] By the attached Figure 1 It can be seen that conventional optical microscopic inspection equipment can only detect the upper surface of the sample, but cannot deeply detect the defects inside the sample. The present invention can achieve complete optical microscopic inspection of the inside of the sample by designing a specially designed immersion objective lens; the present application designs a microscope objective lens with a refractive index medium as the object medium. The refractive index medium is liquid, and its refractive index accurately matches the sample to be tested. During the inspection, the objective lens moves up and down in the medium, so that the object plane can be focused to different heights inside the sample, thereby achieving full inspection of defects inside the component. The present invention can solve the problem that the existing inspection method cannot perform high-precision inspection of the inside of the component, and meet the needs of high-precision body defect detection in the industrial field.

[0014] The above embodiment designs a long working distance immersion objective lens to match the refractive index with the sample to be tested, thereby realizing internal scanning of the sample, and specifically referring to a microscopic optical automatic detection device in the embodiment. However, this method has the problem of limited measurable range of the objective lens. The refractive index matching method of the objective lens can adopt the following two methods: like Figure 4 and Figure 5 The refractive index matching method of the objective lens is shown.

[0015] Figure 4 In the middle scheme (a), the objective lens sets the refractive index matching medium to a constant refractive index value (a horizontal line parallel to the wavelength axis) on the object side. During the test, the intersection of the design value and the refractive index curve of the sample is the working wavelength. Then the refractive index matching liquid is customized to meet the design refractive index value at the working wavelength; Figure 5 In the middle scheme (b), the refractive index matching medium is set as a known stable commercial refractive index matching liquid material on the object side. During detection, the intersection of the refractive index curve of the refractive index matching liquid and the sample is the working wavelength.

[0016] When using solution (a), the sample must satisfy the refractive index close to the refractive index value and have an intersection with the designed horizontal line in the range of 400~700nm.

[0017] When using solution (b), the sample must have a refractive index that intersects with the refractive index matching liquid in the range of 400 to 700 nm.

[0018] Both of the above solutions limit the types and range of samples that can be measured by the system to the refractive index; like Figure 6 and Figure 7 The testable sample range is shown. Figure 6 The range of samples that can be measured when using solution (a); Figure 7 The range of samples that can be measured when using solution (b).

[0019] However, the refractive index curve of real glass material has the characteristics of high short-wavelength, low long-wavelength, and nonlinear monotonically decreasing with wavelength. Therefore, under the condition of a given refractive index matching medium, the measurable sample range is an oblique quadrilateral area.

[0020] from Figure 6 As can be seen from Figure 7, under normal circumstances, the system using solution (a) can measure samples within a refractive index range of approximately 0.017; the system using solution (b) (whose objective lens design medium curve is the real data of a standard commercial refractive index matching liquid) can measure samples within a refractive index range of approximately 0.035.

[0021] In order to solve the problem of limited measurable range of the above objective lens, the embodiment of the present application provides a method for designing an object medium of a microscope objective lens, comprising the following steps: S1. The object medium of the microscope objective is set to be a virtual material, and the refractive index of the virtual material increases linearly and monotonically with the wavelength; S2, determining the intersection point of the sample refractive index curve and the virtual material refractive index oblique line, setting the wavelength at the intersection point as the working wavelength, and setting the refractive index at the intersection point as the working refractive index; S3. Customize the corresponding refractive index matching liquid according to the working wavelength and working refractive index.

[0022] use Figure 8 The medium setting method is to set the object medium of the microscope objective lens as a virtual material. The refractive index curve characteristics of this virtual material are exactly opposite to those of real glass: the refractive index curve of real glass material has the characteristics of high short wavelength, low long wavelength, and nonlinear monotonically decreasing with wavelength; while the refractive index curve of this virtual material has the characteristics of low short wavelength, high long wavelength, and linear monotonically increasing with wavelength. In this way, the measurable range of the sample can be maximized.

[0023] The virtual material uses a linear refractive index, which makes it easier to calculate the required refractive index value when customizing the refractive index matching liquid. As long as the refractive index curve of the sample has an intersection with the virtual material in the range of 400~700nm, it meets the measurability. The refractive index curve used in the figure has a refractive index span of 0.3 in the range of 400~700nm and a slope of 1 / um, ensuring feasibility while increasing the measurable range of the sample. For example, as a comparable object with similar parameters, the refractive index of real glass H-F2 is nd=1.613, and the refractive index span in the range of 400~700nm is 0.0387, which is greater than the designed virtual material 0.3.

[0024] In this way, the measurable sample range can reach about 0.32 refractive index, which is nearly 10 times higher than the 0.035 refractive index range supported by the standard commercial refractive index matching liquid. For sample materials with stronger dispersion, especially materials in the high refractive index region, the advantage of the measurement range of the present invention will be greater because the refractive index curve is steeper.

[0025] from Figure 8 It can be seen that the sample measurable range covers most common glass materials, so that one set of designs can meet most measurement requirements.

[0026] Although the virtual material set in the objective lens design stage has no counterpart in reality, it does not affect the use of this design for measurement. As long as the sample refractive index curve intersects with the virtual material refractive index slope, the wavelength at the intersection can be set as the working wavelength, the refractive index at the intersection can be set as the working refractive index, and then the corresponding refractive index matching liquid can be customized.

[0027] A microscopic optical automatic detection method, using the above-mentioned microscopic optical automatic detection device, comprises the following steps: S101, obtaining a refractive index matching liquid 4 that matches the refractive index of the sample 2 to be tested; S102, immersing the object surface of the microscope objective lens 1 in the refractive index matching liquid 4; S103 , moving the relative distance between the object plane of the microscope objective lens 1 and the sample to be detected 2 , and scanning the entire interior of the sample to be detected 1 .

[0028] As a preferred embodiment of this application, Figure 2In the embodiment 1 shown, the sample to be tested and the object surface of the microscope objective lens are both immersed in the refractive index matching liquid, and the sample to be tested or the microscope objective lens can move in the refractive index matching liquid. During the test, the sample and the end surface of the objective lens are both immersed in the refractive index matching liquid. There is only one medium, the refractive index matching liquid, between the sample and the objective lens. The starting working distance between the objective lens and the sample allows the objective lens to focus on the upper surface of the sample, and then the objective lens moves downward to scan the entire sample interior; the starting working distance between the objective lens and the sample allows the objective lens to focus on the lower surface of the sample, and then the objective lens moves upward to scan the entire sample interior; the objective lens can also be kept stationary, and the sample moves up and down to scan the entire sample interior. When the objective lens is designed, the refractive index of the entire object side is corrected to be equal to the refractive index of the sample, so that the entire sample testing process will not be limited by the depth of field of the microscope objective lens, but only by the working distance of the objective lens. During the test process, any slight defects on the surface and inside of the sample will form strong scattered light to be detected, while the defect-free area will transmit light and appear as a dark background.

[0029] As another preferred embodiment of the present application, Figure 3 In the embodiment 2 shown, the sample to be detected is arranged outside the refractive index matching liquid, and a window piece is arranged on the refractive index matching liquid between the object plane of the microscope objective lens and the sample to be detected. The position between the window piece and the sample to be detected is fixed, and the microscope objective lens can move in the refractive index matching liquid. During detection, the sample is placed in the air, and the objective lens is placed in the refractive index matching liquid. There are three media between the objective lens and the sample, namely, the refractive index matching liquid, the window piece, and the air. During measurement, the thickness of the window piece and the thickness of the air are fixed, and the objective lens moves up and down in the refractive index matching liquid to scan the entire interior of the sample.

[0030] For the test piece with curvature on the surface, such as 2.5D glass, the solution of Example 1 can be used to avoid the influence of surface optical focal length on high-precision imaging; for the test piece with a precisely flat surface, the solution of Example 2 can be used to make the system deployment and detection process more flexible.

[0031] The objective lens structure shown in the figure is for illustration only. In fact, the object media of the three objective lenses are different, so the internal structures are also different. Figure 1 The object medium of the objective lens is air. Figure 2 The object side medium of the objective lens is a refractive index matching liquid. Figure 3 The objective medium of the objective lens is refractive index matching liquid, window plate, and air. Different corrections need to be designed for the three objective lenses.

[0032] The detection system works in single wavelength mode, so the illumination and detection also need to work in single wavelength mode. There are two specific implementation methods: Use single wavelength illumination, such as laser illumination; Use white light for illumination and set narrow-band filters on the detection light path to avoid noise caused by other wavelengths of light.

[0033] In this way, a closed loop is formed in terms of detection method, objective lens design, lighting, detection, etc., so that the detection equipment can achieve the function of completely scanning the sample.

[0034] The objective lens is somewhat similar to an oil immersion objective lens (liquid immersion objective lens) in terms of design, but it has at least the following differences from the oil immersion objective lens: 1. The traditional oil immersion objective lens uses the high refractive index of the medium to obtain a larger NA, with the purpose of further increasing the resolution of the objective lens. The objective lens involved in the present invention uses the characteristics that the medium can match the refractive index of the element to be measured and the objective lens can move freely in the medium, so there are differences in the characteristics and functions used.

[0035] 2. Traditional oil immersion objective lenses are mostly used for high-power or even ultra-high-power objective lenses (for example, above 60x). However, the detection conditions targeted by the present invention require a certain working distance, so they are more often used for objective lenses with lower magnifications (for example, below 40x); 3. There is only one medium between the conventional oil-immersion objective lens and the object surface, usually deionized water or various refractive index matching liquids. However, in addition to the refractive index matching liquid, glass, air, etc. may also exist between the objective lens and the object surface involved in the present invention.

[0036] The present application provides a microscopic internal defect detection device, a microscope objective lens with a refractive index medium as the object medium, the refractive index medium is in liquid form, and its refractive index is precisely matched with that of the sample to be detected. The object surface of the microscope objective lens is immersed in the refractive index matching liquid. During detection, the object surface of the microscope objective lens can be moved relative to the sample to be detected so that the microscope objective lens can be focused to different heights inside the sample to be detected, thereby realizing full detection of defects inside the component. The present invention can solve the problem that the existing detection method cannot perform high-precision detection of the inside of the component, and meet the needs of high-precision body defect detection in the industrial field.

[0037] The present application provides a method for designing an object medium of a microscope objective lens. For a microscope objective lens in the field of industrial detection that uses a refractive index medium as an object medium, the medium type is set to a virtual material. The virtual material has a characteristic that the change in refractive index with wavelength is exactly opposite to that of a conventional material. As long as the sample refractive index curve intersects with the virtual material refractive index slope, the wavelength at the intersection can be set as the working wavelength, the refractive index at the intersection can be set as the working refractive index, and then the corresponding refractive index matching liquid can be customized, so that the detection equipment can adapt to sample types with a wider refractive index range. The present invention can solve the problem of expanding the application scope of the measurement equipment when the refractive index matching method is used for high-precision scanning detection in samples, so that a set of hardware can be compatible with almost all samples.

[0038] The above is a preferred embodiment of the present invention. It should be pointed out that a person skilled in the art can make several improvements and modifications without departing from the principle of the present invention. These improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A method for designing a microscope objective medium, characterized in that: The following steps are involved: The object medium of the microscope objective is set as a virtual material, and the refractive index of the virtual material increases linearly and monotonically with the wavelength; Determine the intersection point of the sample refractive index curve and the virtual material refractive index oblique line, set the wavelength at the intersection point as the working wavelength, and set the refractive index at the intersection point as the working refractive index; According to the working wavelength and working refractive index, the corresponding refractive index matching liquid is customized.

2. A method for designing a microscope objective medium according to claim 1, characterized in that: This virtual material has the opposite refractive index curve characteristics to real glass, with low short wavelengths and high long wavelengths.

3. A method for designing a microscope objective medium according to claim 1, characterized in that: The refractive index curve of the virtual material has a refractive index span of 0.3 in the range of 400~700nm and a slope of 1 / um.

4. A microscopic internal defect detection device for microscopic optics, applied to a method for designing a microscopic objective medium according to any one of claims 1 to 3, characterized in that: The object surface of the microscope objective lens is immersed in a refractive index matching liquid, the refractive index of the refractive index matching liquid matches that of the sample to be tested, and the object surface of the microscope objective lens can move relative to the sample to be tested so that the microscope objective lens can be focused to different heights inside the sample to be tested.

5. The microscopic optical internal microscopic defect detection device according to claim 4, characterized in that: The sample to be detected and the object surface of the microscope objective are both immersed in the refractive index matching liquid, and the sample to be detected or the microscope objective can move in the refractive index matching liquid.

6. The microscopic optical internal microscopic defect detection device according to claim 4, characterized in that: The sample to be detected is arranged outside the refractive index matching liquid, and a window piece is arranged on the refractive index matching liquid between the object plane of the microscope objective lens and the sample to be detected. The position between the window piece and the sample to be detected is fixed, and the microscope objective lens can move in the refractive index matching liquid.

7. The microscopic optical internal microscopic defect detection device according to claim 4, characterized in that: The detection method includes the following steps: Obtaining a refractive index matching liquid that matches the refractive index of the sample to be measured; The object plane of the microscope objective is immersed in the refractive index matching liquid; Move the relative distance between the object plane of the microscope objective and the sample to be tested to scan the entire interior of the sample to be tested.

8. The microscopic optical internal microscopic defect detection device according to claim 7, characterized in that: Move the relative distance between the object plane of the microscope objective and the sample to be detected, including: The initial working distance between the microscope objective lens and the sample to be detected enables the microscope objective lens to focus on the upper surface of the sample to be detected, and then the microscope objective lens moves downward to scan the entire interior of the sample to be detected.

9. The microscopic optical internal microscopic defect detection device according to claim 7, characterized in that: Move the relative distance between the object plane of the microscope objective and the sample to be detected, including: The initial working distance between the microscope objective lens and the sample to be detected enables the microscope objective lens to focus on the lower surface of the sample to be detected, and then the microscope objective lens moves upward to scan the entire interior of the sample to be detected.

10. The microscopic optical internal microscopic defect detection device according to claim 7, characterized in that: The relative distance between the object plane of the microscope objective and the sample to be detected is moved, specifically including: the microscope objective is stationary, the sample to be detected is moved up and down, and the entire interior of the sample is scanned.

Images