Knife edge structure, schlieren imaging system and schlieren imaging method

Abstract

The invention provides a knife edge structure, a schlieren imaging system and a schlieren imaging method. The knife edge structure comprises a substrate and at least one transparent phase knife edge arranged on the substrate; wherein the phase knife edge has a preset working thickness, and the preset working thickness is configured to enable a first light ray emitted from the phase knife edge to have a preset phase difference compared with a second light ray which 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 a bright and dark area on an imaging surface of the schlieren imaging system. According to the knife edge structure, the formed image is clearer, and the texture features in the image are more obvious.

Description

Technical Field

[0001] The present invention relates to the field of wafer imaging technology, and in particular to a knife edge structure, a schlieren imaging system and a schlieren imaging method. Background Art

[0002] Veins are common in transparent crystals such as quartz, sapphire, and lithium niobate. Veins are similar to the textures in jadeite and jade. They are a kind of refractive index fault that is shaped like flocs, filaments, or layers. Because they do not have obvious light and dark contrast, they cannot be distinguished by the naked eye. Specifically, veins are caused by changes in temperature, growth rate, flow field movement, etc. during the growth of the crystal, resulting in a sudden change in density or crystal orientation, and then a change in refractive index. Veins in crystals can be imaged by a vein meter, which generally uses the shadow method or the schlieren method. The shadow method uses parallel light for illumination, and the parallel light is deflected at the vein to produce a shadow; the schlieren method is based on the shadow method, and the parallel light is converged, and the knife edge is used to cut the focus at the convergence point, thereby converting the refractive index change into light and dark changes.

[0003] However, with the maturity of technologies such as area array imaging and artificial intelligence image recognition, methods for identifying and evaluating pulses through digitization and artificial intelligence have gradually developed. Therefore, it is urgent to simultaneously improve the performance of pulse analyzers so that the images they acquire are clearer and the features are more obvious. Summary of the invention

[0004] Based on this, the present invention aims to provide an improved blade 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 a knife edge structure suitable for schlieren imaging, the knife edge structure comprising: a substrate and at least one transparent phase knife edge provided on the substrate; Wherein, the phase blade has a preset working thickness, and the preset working thickness is configured to make a first light ray emitted through the phase blade have a preset phase difference compared to a second light ray emitted without passing through the phase blade, so that the first light ray and the second light ray form bright and dark areas on the imaging surface of the schlieren imaging system.

[0006] The above-mentioned blade structure can retain complete light energy and phase information by adopting a transparent phase blade, and through the preset thickness of the phase blade, the first light emitted through the phase blade and the second light not emitted through the phase blade form light and dark areas on the imaging surface, thereby making the resulting image clearer and the vein features in the image more obvious.

[0007] In one embodiment, the preset phase difference has a value range of 0.9π to 1.1π.

[0008] In one embodiment, the preset working thickness H satisfies: .in, represents the wavelength of the light incident to the knife-edge structure, and n represents the refractive index of the phase knife-edge.

[0009] In one embodiment, the preset phase difference is π, and the preset working thickness H is .

[0010] In one embodiment, the light incident surface of at least one of the phase knife edges is a wedge-shaped surface.

[0011] In one embodiment, a plurality of transparent phase edges with different light incident surface areas are arranged at intervals on the substrate.

[0012] In one embodiment, each phase edge is linearly arranged on the substrate, and along the arrangement direction, the area of ​​the light incident surface of each phase edge gradually increases or decreases.

[0013] In a second aspect, the present application provides a schlieren imaging system, comprising: a light source, a concave mirror, a knife-edge structure as described in any of the preceding 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 through the knife-edge structure is received by the camera and imaged.

[0014] The above-mentioned Schlieren imaging system, by adopting the above-mentioned knife-edge structure, can improve image clarity and make vein features more obvious.

[0015] 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 smaller 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.

[0016] In a third aspect, the present application provides a schlieren imaging method, which uses a schlieren imaging system to perform vein schlieren imaging on a sample, the schlieren imaging device comprises a light source, a concave mirror, a knife-edge structure as described in any of the foregoing embodiments, and a camera, a first light path is formed between the light source and the concave mirror, and a second light path is formed between the concave mirror and the camera, the method comprising: placing a sample to be tested in the first light path or the second light path; placing the knife-edge structure in the second light path; wherein the sample to be tested 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 in the second light path.

[0017] The above method, by setting a transparent phase edge at the focal spot position of the second light path, can retain the complete light energy and phase information during imaging, and through the preset thickness of the phase edge, the first light emitted through the phase edge and the second light passing through the substrate but not emitted through the phase edge form light and dark areas on the imaging surface, thereby making the resulting image clearer and the vein features in the image more obvious. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the implementation methods of this specification or the technical solutions in the prior art, the drawings required for use in the implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some implementation methods recorded in this specification. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0019] Figure 1 A schematic diagram of the composition of a schlieren imaging system according to an embodiment of the present application; Figure 2 This is a schematic diagram of the structure of a knife edge structure according to an embodiment of the present application; Figure 3 A schematic diagram of the position of a phase knife edge according to an embodiment of the present application; Figure 4 A side view schematic diagram of a phase knife edge according to an embodiment of the present application; Figure 5 The comparison of wafer inspection schlieren images of a conventional knife edge and a phase knife edge of an embodiment of the present application is shown; Figure 6 Shows Figure 5 A partial enlarged view of the Schlieren image shown; Figure 7 A schematic top view of a knife edge structure according to another embodiment of the present application; Figure 8 This is a top view schematic diagram of a knife edge structure according to another embodiment of the present application; Fig. 9 Shows this application Figure 4 Phase knife edge and Figure 8 Wafer inspection schlieren image comparison of the phase knife edge shown. DETAILED DESCRIPTION

[0020] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific embodiments of the present invention are described in detail below in conjunction with the accompanying drawings. In the following description, many specific details are set forth to facilitate a full understanding of 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 violating the connotation of the present invention, so the present invention is not limited by the specific embodiments disclosed below.

[0021] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0022] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0023] It should be noted that when an element is referred to as being "fixed to" or "disposed on" another element, it may be directly on the other element or there may be a central element. When an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be a central element at the same time. The terms "vertical", "horizontal", "upper", "lower", "left", "right" and similar expressions used herein are for illustrative purposes only and are not intended to be the only implementation method.

[0024] The traditional Schlieren method places a knife edge at the focus. The knife edge is a sharp, opaque semi-obstruction with a physical edge. The knife edge cuts the focal spot in half, blocking half of the energy and losing half of the phase information, thus affecting the contrast of the Schlieren imaging.

[0025] Based on the above problems, the present application provides a knife-edge structure, which can retain the complete light energy and phase information by adopting a transparent phase knife edge, and through the preset thickness of the phase knife edge, the first light emitted through the phase knife edge and the second light not emitted through the phase knife edge form light and dark areas on the imaging surface, thereby making the resulting image clearer and the vein features in the image more obvious.

[0026] Figure 1 FIG. 1 is a schematic diagram showing the composition of a Schlieren imaging system 10 according to an embodiment of the present application. 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; Figure 2As shown, the blade structure 130 includes a substrate 131 and at least one transparent phase blade 132 arranged on the substrate 131. The light emitted by the light source 110 forms a focal spot at at least one transparent phase blade 132 after passing through the concave mirror 120, and the light emitted through the blade structure 130 is received by the camera 140 and imaged; wherein, the phase blade 132 has a preset working thickness, and the preset working thickness is configured to make the first light emitted through the phase blade 132 have a preset phase difference compared to the second light emitted through the substrate 131 but not through the phase blade 132, so that the first light and the second light form a bright and dark area on the imaging surface of the schlieren imaging system 10.

[0027] In some embodiments, see Figure 2 The blade structure 130 uses a transparent material (such as quartz crystal) as a substrate 131, and a transparent material layer with a preset thickness H is prepared on the substrate 131 by coating or micromachining technology to form a phase blade 132, and the junction between the phase blade 132 and the substrate 131 is called the phase blade edge. Since the blade structure 130 is made of transparent material as a whole, it is beneficial to retain all the spot energy, thereby improving the subsequent light and dark area contrast effect. Among them, the thickness direction is the Y direction.

[0028] In some embodiments, the preset phase difference has a value range of 0.9π to 1.1π, for example, it can be any one of 0.9π, 0.95π, 1.05π, and 1.1π, so that the first light and the second light have an optical path difference of approximately half a wavelength on the camera imaging surface, thereby improving the contrast of the bright and dark areas. Correspondingly, from the perspective of the optical path, it can be inferred that the preset working thickness H satisfies: ,in, 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. When the preset phase difference is π, the first light and the second light can be in anti-phase to further enhance the contrast of the formed light and dark areas. Correspondingly, the preset working thickness H is Optionally, the light source 110 is a monochromatic light source.

[0029] In some embodiments, when testing a sample, the position of the phase knife edge can be moved so that it coincides with the position of the focal spot, such as Figure 3 As shown, the light is incident along the -Y direction, wherein the rectangular pattern area represents the location area of ​​the focal spot, and the area between the upper and lower curved dotted lines represents the area irradiated by the light. It can be seen that the focal spot covers the location of the phase knife edge 132. Figure 4A side view of a phase knife edge of an embodiment of the present application is shown, wherein 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 passes through the phase knife edge 132, and the other half of the light passes through the substrate 131 but not through the phase knife edge, thereby forming clear light and dark areas.

[0030] Figure 5 A comparison of the schlieren images of wafers inspected using a conventional blade and a phase blade of an embodiment of the present application is shown, wherein the left figure shows the schlieren image of the wafer formed using an ordinary blade, and the right figure shows the schlieren image of the wafer formed using a phase blade 132. It can be seen that the light and dark contrast of the veins shown in the right figure is more obvious. Figure 6 Shows Figure 5 From the local enlarged image of the schlieren image shown, it can be seen that the detail contrast of the local features in Figure c is more obvious than that in Figure a, and the detail contrast of the local features in Figure d is more obvious than that in Figure b.

[0031] In some embodiments, the light incident surface of at least one phase knife edge is a wedge-shaped surface. Figure 7 FIG. 1 shows a front view schematic diagram of a phase knife edge of an embodiment of the present application. It can be seen that: Figure 7 The phase blade 132 shown is in the situation that the upper and lower sides gradually converge toward the center line. Of course, only the upper side or the lower side of the phase blade 132 can be inclined toward the center line. 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 blade 132 in the light spot by moving the phase blade 132, so as to facilitate the adaptation of light spots of different sizes and ensure the contrast of the characteristics of the resulting Schlieren image.

[0032] In some embodiments, Figure 8 As shown, a plurality of transparent phase blades 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 blade 132 in the focal spot can be improved, thereby further improving the characteristic contrast of the schlieren image.

[0033] Fig. 9 Shows the use of Figure 2 The phase knife edge (phase knife edge 1) and Figure 8 The phase knife edge (phase knife edge 3) shown in the figure is a comparison of the schlieren images of 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 are further clear.

[0034] Optionally, the phase blade 132 is linearly arranged on the substrate 131, and along the arrangement direction, the area of ​​the light incident surface of each phase blade 132 gradually increases or decreases. For example, the length and width of the third phase blade 132 from left to right are both w, then the length and width of the second phase blade 132 can be both less than w, and the length and width of the fourth phase blade 132 can be both greater than w. In this way, it is beneficial to gradually adjust the size of the phase blade 132 in the focal spot through linear movement, thereby improving the imaging efficiency. Optionally, the light incident surface of the phase blade 132 is a circular surface or a square surface.

[0035] The embodiment of the present application also provides a schlieren imaging method, including: using a schlieren imaging system 10 to perform vein schlieren imaging on a sample, 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 light path is formed between the light source 110 and the concave mirror 120, and a second light path is formed between the concave mirror 120 and the camera 140, the method includes: S100, placing the sample to be tested on the first light path or the second light path; S200, placing the knife-edge structure in the second optical path; wherein the sample to be tested is located between the knife-edge structure 130 and the concave mirror 120, and the position of 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.

[0036] The above method, by setting the transparent phase edge 132 at the focal spot position of the second light path, can retain the entire light energy and phase information during imaging, and through the preset thickness of the phase edge 132, the first light emitted through the phase edge 132 and the second light passing through the substrate 131 but not emitted through the phase edge 132 form light and dark areas on the imaging surface, thereby making the resulting image clearer and the vein features in the image more obvious.

[0037] It should be noted that the 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 "roughly", "about", "approximately" or "substantially" in some cases. For example, unless otherwise specified, "roughly", "about", "approximately" or "substantially" can indicate a ±20% variation of the value described. Accordingly, in some embodiments, the numerical parameters used in the specification and claims are approximate values, which may change according to the required features of individual embodiments. In some embodiments, the numerical parameters should take into account the specified significant digits and adopt the general method of retaining digits. Although the numerical domains and parameters used to confirm the breadth of their range in some embodiments of the present application are approximate values, in specific embodiments, the setting of such numerical values ​​is as accurate as possible within the feasible range.

[0038] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0039] The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A knife edge structure suitable for Schlieren imaging, characterized in that: The blade structure comprises: A substrate and at least one transparent phase knife edge disposed on the substrate; in, The phase knife edge has a preset working thickness, and the preset working thickness is configured to make a first light ray emitted through the phase knife edge have a preset phase difference compared to a second light ray emitted through the substrate but not through the phase knife edge, so that the first light ray and the second light ray form bright and dark areas on the imaging surface of the schlieren imaging system.

2. The blade structure according to claim 1, characterized in that: The preset phase difference has a value range of 0.9π to 1.1π.

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

4. The knife 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 knife edge structure according to claim 1, characterized in that: The light incident surface of at least one of the phase knife edges is a wedge-shaped surface.

6. The blade structure according to claim 1, characterized in that: A plurality of transparent phase knife edges with different light incident surface areas are arranged at intervals on the substrate.

7. The knife edge structure according to claim 6, characterized in that: Each phase edge is linearly arranged on the substrate, and along the arrangement direction, the area of ​​the light incident surface of each phase edge gradually increases or decreases.

8. A Schlieren imaging system, characterized in that: include: A light source, a concave mirror, a knife-edge structure as claimed in any one of claims 1 to 7, and a camera; The light 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 emitted through the knife edge structure is received by the camera and imaged.

9. The Schlieren imaging system according to claim 8, characterized in that: The focal spot covers the position where the phase knife edge is located; and the width of the phase knife edge is smaller 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.

10. A Schlieren imaging method, using a Schlieren imaging system to perform veining Schlieren imaging on a sample, the Schlieren imaging system comprising a light source, a concave mirror, a knife-edge structure according to any one of claims 1 to 7, and a camera, a first light path is formed between the light source and the concave mirror, a second light path is formed between the concave mirror and the camera, the method comprising: Placing the sample to be tested on the first light path or the second light path; The knife-edge structure is placed in the second optical path; wherein the sample to be tested is located between the knife-edge structure and the concave mirror, and the position of at least one of the transparent phase edges on the knife-edge structure coincides with the position of the focal spot of the light in the second optical path.

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