Knife-edge structure, schlieren imaging system and schlieren imaging method

Abstract

The present application provides an edge structure, a schlieren imaging system, and a schlieren imaging method. The edge structure includes a substrate and at least one transparent phase edge disposed on the substrate; wherein, the phase edge has a preset working thickness, and the preset working thickness is configured to enable a first light ray emitted from the phase edge to have a preset phase difference compared with a second light ray that passes through the substrate but does not pass through the phase edge, so that the first light ray and the second light ray form bright and dark regions on the imaging surface of the schlieren imaging system. The above-mentioned edge structure can make the formed image clearer and the vein features in the image more obvious.

Description

Technical Field

[0001] The present invention relates to the technical field of wafer imaging, and particularly to an edge structure, a schlieren imaging system and a schlieren imaging method. Background Art

[0002] Veining is commonly present in transparent crystals such as quartz, sapphire, and lithium niobate. Veining is similar to the texture in jade and emerald, and is a refractive index fault in the form of flocculent, filamentous or layered shapes. Since there is no obvious contrast between light and dark, it cannot be distinguished by the naked eye. Specifically, veining is caused by changes in temperature, growth rate, flow field movement, etc. during the crystal growth process, resulting in density mutation or crystal orientation mutation, and then refractive index change. The veining in the crystal can be imaged by a veining instrument, and the veining instrument generally uses the shadow method or the schlieren method. Among them, the shadow method uses parallel light for illumination, and the parallel light is deflected at the veining to generate a shadow; the schlieren method is based on the shadow method, converges the parallel light, and uses an edge to cut the focus at the convergence point, so as to convert the refractive index change into a change between light and dark.

[0003] However, with the maturity of technologies such as area imaging and artificial intelligence image recognition, methods for identifying and evaluating veining through digitization and artificial intelligence have been gradually developed. Therefore, it is urgent to synchronously improve the performance of the veining instrument to make the obtained images clearer and the features more obvious. Summary of the Invention

[0004] Based on this, the present invention aims to provide an improved edge structure, a schlieren imaging system and a schlieren imaging method to solve at least one of the above problems.

[0005] In a first aspect, the present application provides an edge structure suitable for schlieren imaging, and the edge structure includes: a substrate and at least one transparent phase edge provided on the substrate;

[0006] Wherein, the phase edge has a preset working thickness, and the preset working thickness is configured to make the first light emitted through the phase edge have a preset phase difference compared with the second light not emitted through the phase edge, so that the first light and the second light form a light and dark area on the imaging surface of the schlieren imaging system.

[0007] In the above edge structure, by using a transparent phase edge, the complete light energy and phase information can be retained, and the preset thickness of the phase edge enables the first light emitted through the phase edge and the second light not emitted through the phase edge to form a light and dark area on the imaging surface, thereby making the formed image clearer and the veining features in the image more obvious.

[0008] In one embodiment, the value range of the preset phase difference is 0.9π to 1.1π.

[0009] In one embodiment, the preset working thickness H satisfies: , where represents the wavelength of the light incident on the knife-edge structure, and n represents the refractive index of the phase knife-edge.

[0010] In one embodiment, the preset phase difference is π, and the preset working thickness H is .

[0011] In one embodiment, the light incident surface of at least one of the phase knife-edges is a wedge-shaped surface.

[0012] In one embodiment, a plurality of transparent phase knife-edges with different light incident surface areas are arranged at intervals on the substrate.

[0013] In one embodiment, the phase knife-edges are linearly arranged on the substrate, and along the arrangement direction, the area of the light incident surface of each phase knife-edge gradually increases or gradually decreases.

[0014] In a second aspect, the present application provides a schlieren imaging system, including: a light source, a concave mirror, a knife-edge structure as described in any of the previous embodiments, and a camera; wherein, the light emitted by the light source forms a focal spot at at least one of the transparent phase knife-edges after passing through the concave mirror, and the light emitted by the knife-edge structure is received and imaged by the camera.

[0015] For the above schlieren imaging system, by adopting the above knife-edge structure, the image clarity can be improved and the vein characteristics can be made more obvious.

[0016] In one embodiment, the focal spot covers the position where the phase knife-edge is located; and, the width of the phase knife-edge is less than the diameter of the focal spot, and / or the width of the phase knife-edge is half of the diameter of the focal spot.

[0017] Thirdly, the present application provides a schlieren imaging method, which uses a schlieren imaging system to perform pulse schlieren imaging on a sample. The schlieren imaging device includes a light source, a concave mirror, a knife-edge structure as described in any of the previous embodiments, and a camera. A first optical path is formed between the light source and the concave mirror, and a second optical path is formed between the concave mirror and the camera. The method includes: placing the sample to be measured in the first optical path or the second optical path; placing the knife-edge structure in the second optical path; wherein, the sample to be measured is located between the knife-edge structure and the concave mirror, and the position of at least one of the transparent phase knife-edges on the knife-edge structure coincides with the position of the focal spot of the light rays in the second optical path.

[0018] In the above method, by setting the transparent phase knife-edge at the focal spot position of the second optical path, the complete light energy and phase information can be retained during imaging, and through the preset thickness of the phase knife-edge, the first light rays exiting from the phase knife-edge and the second light rays passing through the substrate but not exiting from the phase knife-edge form bright and dark regions on the imaging surface, thereby making the formed image clearer and the vein features in the image more obvious. Description of the Drawings

[0019] In order to more clearly illustrate the embodiments of the present specification or the technical solutions in the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings described below are only some embodiments recorded in the present specification. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0020] Figure 1 It is a schematic diagram of the composition of a schlieren imaging system according to an embodiment of the present application;

[0021] Figure 2 It is a schematic diagram of the structure of a knife-edge structure according to an embodiment of the present application;

[0022] Figure 3 It is a schematic diagram of the position of a phase knife-edge according to an embodiment of the present application;

[0023] Figure 4 It is a side view schematic diagram of a phase knife-edge according to an embodiment of the present application;

[0024] Figure 5 It shows a comparison of the wafer inspection schlieren images of a traditional knife-edge and a phase knife-edge according to an embodiment of the present application;

[0025] Figure 6 It shows Figure 5 A partial enlarged view of the shown schlieren image;

[0026] Figure 7Top view schematic diagram of the cutting edge structure according to another embodiment of the present application;

[0027] Figure 8 Top view schematic diagram of the cutting edge structure according to yet another embodiment of the present application;

[0028] Figure 9 Shows the present application Figure 4 The phase cutting edge shown and Figure 8 Comparison of the wafer inspection schlieren images of the phase cutting edges shown. Detailed implementation manners

[0029] To make the above objects, features, and advantages of the present invention more obvious and understandable, the following will describe the detailed implementation manners of the present invention in conjunction with the accompanying drawings. Many specific details are set forth in the following description in order to fully understand the present invention. However, the present invention can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without departing from the connotation of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed below.

[0030] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus cannot be construed as a limitation of the present invention.

[0031] In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one of such features. In the description of the present invention, "a plurality" means at least two, such as two, three, etc., unless otherwise specifically defined.

[0032] It should be noted that when an element is referred to as being "fixed to" or "disposed on" another element, it can be directly on the other element or there may also be a middle element. When an element is considered to be "connected" to another element, it can be directly connected to the other element or there may be a middle element at the same time. The terms "vertical", "horizontal", "upper", "lower", "left", "right" and similar expressions used herein are only for the purpose of illustration and do not represent the only implementation manner.

[0033] In the traditional schlieren method, a knife edge is placed at the focus. The knife edge is a sharp semi-occluder with a physical edge. By cutting the focus spot in half with the knife edge, half of the energy is blocked and half of the phase information is lost, thus affecting the contrast of schlieren imaging.

[0034] Based on the above problems, the present application provides a knife-edge structure. By using a transparent phase knife edge, the complete light energy and phase information can be retained, and the first light ray exiting through the phase knife edge and the second light ray not exiting through the phase knife edge form light and dark regions on the imaging surface through the preset thickness of the phase knife edge, so that the formed image is clearer and the vein features in the image are more obvious.

[0035] Figure 1 The composition schematic diagram of the schlieren imaging system 10 according to an embodiment of the present application is shown. It can be seen that the schlieren imaging system 10 includes a light source 110, a concave mirror 120, a knife-edge structure 130, and a camera 140; among them, as Figure 2 shown, the knife-edge structure 130 includes a substrate 131 and at least one transparent phase knife edge 132 provided on the substrate 131. The light ray emitted by the light source 110 forms a focus spot at at least one transparent phase knife edge 132 after passing through the concave mirror 120, and the light ray exiting through the knife-edge structure 130 is received by the camera 140 and imaged; among them, the phase knife edge 132 has a preset working thickness, and the preset working thickness is configured to make the first light ray exiting through the phase knife edge 132 have a preset phase difference compared with the second light ray that passes through the substrate 131 but does not pass through the phase knife edge 132, so that the first light ray and the second light ray form light and dark regions on the imaging surface of the schlieren imaging system 10.

[0036] In some embodiments, referring to Figure 2 continuously, the knife-edge structure 130 uses a transparent material (such as quartz crystal) as the substrate 131, and a transparent material layer with a preset thickness H is prepared on the substrate 131 through a coating or microfabrication process to form the phase knife edge 132, and the junction of the phase knife edge 132 and the substrate 131 is called the phase knife-edge edge. Since the entire knife-edge structure 130 uses a transparent material, it is beneficial to retain all the spot energy, thereby enhancing the subsequent contrast effect between the light and dark regions. Among them, the thickness direction is the Y direction.

[0037] In some embodiments, the value range of the preset phase difference is 0.9π to 1.1π. For example, it can be any one of 0.9π, 0.95π, 1.05π, 1.1π. Thus, there is an optical path difference of approximately half a wavelength between the first light ray and the second light ray on the camera imaging surface, thereby enhancing the contrast between the light and dark regions. Correspondingly, from the perspective of the optical path, it can be inferred that the preset working thickness H satisfies: , where, represents the wavelength of the light incident on the knife-edge structure 130, and n represents the refractive index of the phase knife-edge 132. Among them, when the preset phase difference is π, the first light ray and the second light ray can be made to be out of phase, thereby further enhancing the contrast of the formed bright and dark regions. Correspondingly, the preset working thickness H at this time is . Optionally, the light source 110 is a monochromatic light source.

[0038] In some embodiments, when detecting a sample, the position of the phase knife-edge can be moved to coincide with the position of the focal spot. For example, Figure 3 as shown, the light ray is incident along the -Y direction, where the rectangular pattern region represents the position region of the focal spot, and the region between the upper and lower two curved dotted lines represents the region irradiated by the light ray. It can be seen that the focal spot covers the position where the phase knife-edge 132 is located. Figure 4 shows a side view of the phase knife-edge according to an embodiment of the present application. Among them, w represents the width of the phase knife-edge 132, and the width of the phase knife-edge 132 is smaller than the diameter of the focal spot; optionally, the width of the phase knife-edge 132 can be half of the focal spot, so that half of the light quantity passes through the phase knife-edge 132, and the other half of the light quantity passes through the substrate 131 but does not pass through the phase knife-edge, thereby forming a clear bright and dark region.

[0039] Figure 5 shows a comparison diagram of schlieren images of a wafer detected by a traditional knife-edge and a phase knife-edge according to an embodiment of the present application. Among them, the left figure shows the schlieren image of the wafer formed by using an ordinary knife-edge, and the right figure shows the schlieren image of the wafer formed by using the phase knife-edge 132. It can be seen that the contrast of the vein light and dark in the right figure is more obvious. Figure 6 shows Figure 5 a partial enlarged view of the schlieren image shown. It can be seen that the detail comparison of the local features in figure c is more obvious than that of the local features in figure a, and the detail comparison of the local features in figure d is more obvious than that of the local features in figure b.

[0040] In some embodiments, the light incident surface of at least one phase knife-edge is a wedge surface. Figure 7 shows a front view schematic diagram of the phase knife-edge according to an embodiment of the present application. It can be seen that Figure 7 the shown phase knife-edge 132 is in a situation where the upper and lower sides gradually converge towards the midline. Of course, only the upper side or the lower side of the phase knife-edge 132 can be inclined towards the midline. The present application does not limit the specific form of the wedge surface. In this way, it is beneficial to adjust the width of the phase knife-edge 132 in the light spot by moving the phase knife-edge 132, so as to conveniently adapt to light spots of different sizes and ensure the contrast of the features of the formed schlieren image.

[0041] In some embodiments, for example, Figure 8As shown, a plurality of transparent phase knife edges 132 with different light incident surface areas are arranged at intervals on the substrate 131. In this way, by aligning with the focal spot in two directions, the position accuracy of the phase knife edge 132 in the focal spot can be improved, thereby further enhancing the characteristic contrast of the schlieren image.

[0042] Figure 9 It shows the use of Figure 2 the phase knife edge (phase knife edge 1) shown and Figure 8 the phase knife edge (phase knife edge 3) shown, and the comparison diagram of the schlieren images for detecting the wafer. It can be seen that compared with the local schematic diagrams c and d corresponding to the phase knife edge 1, the contrast of the local schematic diagrams e and f corresponding to the phase knife edge 3 is further improved, and the lines become clearer.

[0043] Optionally, the phase knife edges 132 are linearly arranged on the substrate 131, and along the arrangement direction, the area of the light incident surface of each phase knife edge 132 gradually increases or gradually decreases. For example, if the length and width of the third phase knife edge 132 from left to right are both w, then the length and width of the second phase knife edge 132 can be both less than w, and the length and width of the fourth phase knife edge 132 can be both greater than w. In this way, it is beneficial to gradually adjust the size of the phase knife edge 132 in the focal spot by linear movement, thereby improving the imaging efficiency. Optionally, the light incident surface of the phase knife edge 132 is a circular surface or a square surface.

[0044] The embodiment of the present application further provides a schlieren imaging method, including: performing pulsed schlieren imaging on a sample by using a schlieren imaging system 10, where the schlieren imaging system 10 includes a light source 110, a concave mirror 120, a knife edge structure 130, and a camera 140. A first optical path is formed between the light source 110 and the concave mirror 120, and a second optical path is formed between the concave mirror 120 and the camera 140. The method includes:

[0045] S100. Place the sample to be measured in the first optical path or the second optical path;

[0046] S200. Place the knife edge structure in the second optical path; wherein, the sample to be measured is located between the knife edge structure 130 and the concave mirror 120, and the position where at least one transparent phase knife edge 132 on the knife edge structure 130 coincides with the position of the focal spot of the light in the second optical path.

[0047] In the above method, by setting the transparent phase knife edge 132 at the focal spot position of the second optical path, the entire light energy and phase information can be retained during imaging, and through the preset thickness of the phase knife edge 132, the first light emitted from the phase knife edge 132 and the second light that passes through the substrate 131 but is not emitted from the phase knife edge 132 form bright and dark regions on the imaging surface, thereby making the formed image clearer and the vein features in the image more obvious.

[0048] It should be noted that numbers representing quantities or properties used to describe and claim certain embodiments of the present application should be understood to be modified by the terms "substantially", "about", "approximate" or "essentially" in certain cases. For example, unless otherwise specified, "substantially", "about", "approximate" or "essentially" may indicate a variation of ±20% of the value they describe. Accordingly, in some embodiments, the numerical parameters used in the specification and claims are approximate values, which may vary according to the characteristics required by individual embodiments. In some embodiments, the numerical parameters should consider the specified significant digits and adopt the method of retaining the general number of digits. Although the numerical ranges and parameters used to confirm the breadth of the scope in some embodiments of the present application are approximate values, in specific embodiments, such numerical settings are as precise as possible within the feasible range.

[0049] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the various technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered to be within the scope described in this specification.

[0050] The above-described embodiments merely represent several implementation manners of the present invention, and their descriptions are relatively specific and detailed, but should not be construed as limiting the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the invention patent should be subject to the appended claims.

Claims

1. A blade structure suitable for schlieren imaging, characterized in that, The described knife-edge structure includes: a substrate and at least one transparent phase knife-edge provided on the substrate; wherein, the phase knife-edge has a preset working thickness, and the preset working thickness is configured to make the first light ray emerging from the phase knife-edge have a preset phase difference compared with the second light ray that passes through the substrate but does not pass through the phase knife-edge, so that the first light ray and the second light ray form bright and dark regions on the imaging surface of the schlieren imaging system; the phase knife-edges are linearly arranged on the substrate, and along the arrangement direction, the area of the light incident surface of each phase knife-edge gradually increases or gradually decreases; the light incident surface of at least one phase knife-edge is a wedge surface.

2. The cutting edge structure according to claim 1, characterized in that, The value range of the preset phase difference is 0.9π to 1.1π.

3. The edge structure according to claim 2, characterized in that, The preset working thickness H satisfies: , where represents the wavelength of the light incident on the blade structure, and n represents the refractive index of the phase blade.

4. The edge structure according to claim 2 or 3, characterized in that, The preset phase difference is π, and the preset working thickness H is .

5. The cutting edge structure according to claim 1, characterized in that, A plurality of transparent phase knife-edges with different light incident surface areas are spaced on the substrate.

6. A schlieren imaging system, characterized in that, It includes: a light source, a concave mirror, the knife-edge structure as described in any one of claims 1 to 5, and a camera; wherein, the light ray emitted by the light source is reflected by the concave mirror to form a focal spot at at least one of the transparent phase knife-edges, and the light ray emerging from the knife-edge structure is received and imaged by the camera.

7. The schlieren imaging system according to claim 6, wherein The focal spot covers the position where the phase knife-edge is located; and the width of the phase knife-edge is less than the diameter of the focal spot, and / or the width of the phase knife-edge is half of the diameter of the focal spot.

8. A schlieren imaging method, which uses a schlieren imaging system to perform pulse schlieren imaging on a sample. The schlieren imaging system includes a light source, a concave mirror, the knife-edge structure as described in any one of claims 1 to 5, and a camera. A first optical path is formed between the light source and the concave mirror, and a second optical path is formed between the concave mirror and the camera. The method includes: placing the sample to be measured in the first optical path or the second optical path; placing the knife-edge structure in the second optical path; wherein, the sample to be measured is located between the knife-edge structure and the concave mirror, and the position where at least one of the transparent phase knife-edges on the knife-edge structure is located coincides with the position of the focal spot of the light ray in the second optical path.

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