Illumination system and detection system

Abstract

The embodiment of the invention provides an illumination system and a detection system. The illumination system and the detection system are used for improving the illumination quality of a detection view field of a to-be-detected object. The illumination system in the embodiment of the invention comprises an illumination light source which presents a preset shape and is used for imaging to the surface of a to-be-detected object in a critical illumination mode; the turning prism is coaxially arranged with the illumination light source and is used for deflecting the illumination light rays emitted by the illumination light source, so that main light rays generated after deflection enter the double-Gaussian imaging system; the double-Gaussian imaging system and the main light are coaxially arranged, and the double-Gaussian imaging system is used for carrying out optical processing on the main light, generating emergent light and irradiating the emergent light to the surface of the to-be-detected object at a preset azimuth angle theta, the double-Gaussian imaging system comprises a first single lens, a first doublet lens, a second doublet lens and a second single lens which are sequentially arranged in the incidence direction of main light, and the preset azimuth angle theta ranges from 40 degrees to 50 degrees.

Description

Technical Field

[0001] The present application relates to the field of optical detection technology, and in particular to a lighting system and a detection system. Background Art

[0002] When detecting an object to be detected, in order to improve the resolution of the detection system, there are generally two methods: bright field detection and dark field detection.

[0003] Specifically, when bright field detection is used, the light source is generally incident vertically on the surface of the object to be detected, while when dark field detection is used, the light source is incident on the surface of the object to be detected at a preset azimuth angle. In the process of performing dark field detection, dark field lighting is generally required to meet the characteristics of high brightness and high uniformity. How to ensure the high brightness and high uniformity of dark field lighting is a problem that needs to be solved urgently. Summary of the Invention

[0004] The embodiments of the present application provide an illumination system and an inspection system for providing a high-brightness and high-uniformity illumination light source to an object to be inspected, so as to improve the illumination quality of the inspection field of view of the object to be inspected, thereby improving the signal-to-noise ratio of detecting small defects in the object to be inspected.

[0005] A first aspect of an embodiment of the present application provides a lighting system, including:

[0006] An illumination light source of a preset shape, used for imaging onto the surface of the object to be inspected by means of critical illumination;

[0007] a turning prism coaxially arranged with the illumination light source, for deflecting the illumination light emitted by the illumination light source, wherein the main light generated after the illumination light is deflected enters the double-Gauss imaging system;

[0008] The double Gaussian imaging system is coaxially arranged with the principal ray, and is used to perform optical processing on the principal ray to generate outgoing light and irradiate the outgoing light onto the surface of the object to be detected at a preset azimuth angle θ, wherein the double Gaussian imaging system includes a first single lens, a first double-cemented lens, a second double-cemented lens, and a second single lens arranged in sequence along the incident direction of the principal ray, and the preset azimuth angle θ includes 40° to 50°.

[0009] Preferably, the magnification of the lighting system is 1 to 3 times.

[0010] Preferably, the distance S between the object to be detected and the second single lens along the outgoing light is comprised between 35 mm and 200 mm.

[0011] Preferably, the S is 70 mm and the θ is 45°.

[0012] Preferably, the first single lens is a convex lens, and the focal length range of the first single lens includes 49 mm to 59 mm;

[0013] The first doublet lens includes a convex lens and a concave lens along the direction of the principal light, and the focal length range of the first doublet lens includes -67 mm to -57 mm;

[0014] The second doublet lens includes a concave lens and a convex lens along the direction of the principal light, and the focal length of the second doublet lens ranges from 43 mm to 53 mm;

[0015] The second single lens is a convex lens, and the focal length range of the second single lens includes 79 mm to 89 mm.

[0016] Preferably, the illumination light source is a rectangular light source, and the RMS radius of the light spot presented by the rectangular light source on the object to be detected is not greater than 30um, and the GEO radius of the light spot presented by the illumination light source on the object to be detected is not greater than 70um.

[0017] Preferably, the illumination light source is a rectangular light source. If the image of the rectangular light source on the object to be detected is a rectangular light spot, and the angle between the chief light of the illumination system and the first side of the rectangular light spot is θ, and the angle between the chief light of the illumination system and the second side of the rectangular light spot is 90°, then the magnification of the first side of the rectangular light spot relative to the first side corresponding to the rectangular light source is m′, and the magnification of the second side of the rectangular light spot relative to the second side corresponding to the rectangular light source is m, wherein:

[0018] in:

[0019] The θ′ is the complementary angle between the image of the object to be detected passing through the double Gaussian imaging system and the angle between the main light.

[0020] Preferably, the rectangular light spot of the rectangular light source on the object to be detected has a sharp boundary, and the illumination of the rectangular light spot is uniform.

[0021] A second aspect of an embodiment of the present application provides a detection system, characterized in that it includes at least an object to be detected and at least one set of lighting systems provided by the first aspect of the embodiment of the present application.

[0022] Preferably, the lighting system is a plurality of groups, and any two of the plurality of lighting systems are axially symmetrically distributed with respect to the normal of the object to be detected, and the plurality of groups is at least two groups.

[0023] It can be seen from the above technical solutions that the embodiments of the present invention have the following advantages:

[0024] The lighting system in the embodiment of the present application includes: an illumination light source presenting a preset shape, which is used to image the surface of the object to be detected by critical illumination; a turning prism arranged coaxially with the illumination light source, which is used to deflect the illumination light emitted by the illumination light source, and the main light generated after the illumination light is deflected is incident on the double Gaussian imaging system, the double Gaussian imaging system is arranged coaxially with the main light, and is used to optically process the main light, generate outgoing light and irradiate the surface of the object to be detected at a preset azimuth angle θ, wherein the double Gaussian imaging system includes a first single lens, a first double-cemented lens, a second double-cemented lens and a second single lens arranged in sequence along the incident direction of the main light, and the preset azimuth angle θ includes 40° to 50°.

[0025] Because the embodiment of the present application can improve the brightness of the lighting source through a turning prism and improve the uniformity of the lighting source through critical lighting, the lighting system in the embodiment of the present application can achieve a dark field detection field with high brightness and high uniformity, thereby improving the signal-to-noise ratio of detecting small defects in the object to be inspected.

[0026] Furthermore, in the embodiment of the present application, a dual-Gaussian imaging system is also used to optically process the principal light. The dual-Gaussian system has at least the following advantages during the optical processing:

[0027] 1. Symmetrical distribution: Because symmetrical distribution can correct various aberrations, it can ensure clear imaging of the illumination light source. 2. Simple structure: Only 4 pieces and 6 lenses are needed to achieve the purpose of critical illumination and clear imaging. That is, under the premise of saving costs, the signal-to-noise ratio of small defect detection of the object to be inspected is guaranteed. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a schematic diagram of an embodiment of a lighting system in an embodiment of the present application;

[0029] Figure 2 In the embodiment of the present application, a schematic diagram of the size of the light spot presented by the rectangular light source on the surface of the object to be detected is provided when the rectangular light source is 12.5mm*1mm, θ=45°, and m=2;

[0030] Figure 3 A schematic diagram of a rectangular light spot array diagram in an embodiment of the present application;

[0031] Figure 4 This is a simulation diagram of the rectangular spot lighting effect in the embodiment of the present application;

[0032] Figure 5 This is a schematic diagram of an embodiment of the detection system in the embodiment of the present application. DETAILED DESCRIPTION

[0033] Embodiments of the present invention provide an illumination system and an inspection system for providing a high-brightness and high-uniformity illumination light source to an object to be inspected, thereby improving the illumination quality of the inspection field of the object to be inspected, thereby improving the signal-to-noise ratio of detecting small defects in the object to be inspected.

[0034] In order to enable those skilled in the art to better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of the present invention.

[0035] The terms "first," "second," "third," "fourth," and the like in the specification and claims of the present invention and in the accompanying drawings are used to distinguish similar objects and are not necessarily used to describe a particular order or precedence. It should be understood that the terms used in this manner are interchangeable where appropriate so that the embodiments described herein can be implemented in an order other than that illustrated or described herein. In addition, the terms "including" and "having," and any variations thereof, are intended to cover non-exclusive inclusions. For example, a process, method, system, product, or apparatus comprising a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0036] For ease of understanding, the lighting system in the embodiment of the present application is described below. Figure 1 In the embodiment of the present application, the lighting system includes:

[0037] An illumination light source 10, a turning prism 20 and a double Gaussian imaging system 30, wherein the double Gaussian imaging system 30 includes a first single lens 301, a first doublet lens 302, a second doublet lens 303 and a second single lens 304 arranged in sequence along the direction of the main light emitted from the turning prism 20.

[0038] Specifically, the illumination source 10 in the embodiment of the present application can have a predetermined shape, such as a circle, rectangle, or square. The specific shape of the light source is related to the field of view required for the surface of the object to be inspected, and no specific limitation is imposed herein. To ensure uniform illumination of the surface of the object to be inspected, the illumination source 10 in the embodiment of the present application uses critical illumination to image the surface of the object to be inspected. Because critical illumination only generates light along a predetermined azimuth angle during dark-field inspection, it can reduce background light interference and improve the accuracy of surface defect detection of the object to be inspected.

[0039] Furthermore, because the luminous intensity of the illumination light source decreases as the luminous angle becomes larger, that is, the luminous intensity of the light source is strongest along the direction perpendicular to the surface of the light source, and in order to ensure the high brightness of dark field illumination, that is, to ensure the utilization of the energy of the illumination light source, a turning prism 20 is provided along the direction of the illumination light emitted by the illumination light source in the embodiment of the present application, wherein the turning prism 20 is used to deflect the illumination light emitted by the illumination light source 10, and the main light generated after the illumination light is deflected enters the double Gaussian imaging system. It can also be considered that the main light generated after the deflection is perpendicular to the first single lens 301 in the double Gaussian imaging system, thereby ensuring the efficient utilization of the light source energy in the illumination light source 10.

[0040] In order to image the illumination light source 10 onto the surface of the object to be detected, the embodiment of the present application is further provided with a double Gaussian imaging system 30 along the propagation direction of the main light, wherein the double Gaussian imaging system 30 is used to perform optical processing on the main light (such as astigmatism compensation, distortion correction, focal length adjustment, aberration correction, achromatism, direct imaging, etc.), generate outgoing light and irradiate the surface of the object to be detected at a preset azimuth angle θ, where the azimuth angle θ is the angle between the outgoing light and the surface normal of the object to be detected. In order to ensure the effect of dark field detection, the embodiment of the present application sets the azimuth angle θ to a range of 40° to 50°.

[0041] Specifically, the double Gaussian imaging system includes a system composed of at least four bilaterally symmetrical lenses (such as four lenses, six lenses, or eight lenses, etc.), wherein the mutually symmetrical structures can be used to compensate for each other's light. That is, when the double Gaussian system includes four bilaterally symmetrical lenses, if the two lenses on the left converge the light, then the two lenses on the right diverge the light.

[0042] Furthermore, the double Gaussian imaging system 30 in the embodiment of the present application includes a first single lens 301, a first doublet lens 302, a second doublet lens 303 and a second single lens 304 arranged in sequence along the direction of the main light, wherein the first single lens 301 and the first doublet lens 302 are used to converge the main light, while the second doublet lens 303 and the second single lens 304 are used for focal length adjustment and aberration correction.

[0043] The role of the double Gaussian imaging system in the present application is, on the one hand, to optically process the main light and generate an outgoing light, and the outgoing light is incident on the surface of the object to be detected at a preset azimuth angle θ to achieve the purpose of dark field detection, wherein the optical processing may include one or more processing capabilities of astigmatism compensation, distortion correction, focal length adjustment, aberration correction, achromatism, and direct imaging; on the other hand, it is to image the illumination light source onto the surface of the object to be detected to achieve the purpose of critical illumination, and the optical parameters of the first single lens 301, the first double-cemented lens 302, the second double-cemented lens 303 and the second single lens 304 change with the light spot of the illumination light source 10 on the object to be detected and the second single lens 304 along the outgoing light. Therefore, the optical parameters of the first single lens 301, the first double-cemented lens 302, the second double-cemented lens 303 and the second single lens 304 are not specifically limited. As long as the first single lens 301, the first double-cemented lens 302, the second double-cemented lens 303 and the second single lens 304 can perform some optical processing on the main light generated by the turning prism 20, and make the optically processed outgoing light irradiate the surface of the object to be detected at a preset azimuth angle θ, and image the illumination light source onto the surface of the object to be detected, the parameters of the first single lens 301, the first double-cemented lens 302, the second double-cemented lens 303 and the second single lens 304 are not specifically limited.

[0044] In an embodiment of the present application, the lighting system involved includes an illumination light source presenting a preset shape, which is used to image the surface of the object to be detected by critical illumination; a turning prism arranged coaxially with the illumination light source, which is used to deflect the illumination light emitted by the illumination light source, so that the main light generated after the illumination light is deflected enters the double Gaussian imaging system; the double Gaussian imaging system is arranged coaxially with the main light generated by the deflection, which is used to irradiate the outgoing light generated after optical processing of the main light to the surface of the object to be detected at a preset azimuth angle θ, wherein the double Gaussian imaging system includes a first single lens, a first double-cemented lens, a second double-cemented lens and a second single lens arranged in sequence along the direction of the main light, and the preset azimuth angle θ includes 40° to 50°.

[0045] Because the embodiment of the present application can improve the brightness of the lighting source through a turning prism and improve the uniformity of the lighting source through critical lighting, the lighting system in the embodiment of the present application can achieve a dark field detection field with high brightness and high uniformity, thereby improving the signal-to-noise ratio of detecting small defects in the object to be inspected.

[0046] Furthermore, the dual Gaussian imaging system in the embodiment of the present application has at least the following advantages during the imaging process: 1. Symmetrical distribution, because the symmetrical distribution can correct various aberrations, thereby ensuring clear imaging of the illumination light source; 2. Simple structure, only 4 pieces and 6 lenses are needed to achieve the purpose of critical illumination and clear imaging, that is, while saving costs, the signal-to-noise ratio of the detection of small defects in the object to be inspected is guaranteed.

[0047] against Figure 1 In the embodiment, in order to form a field of view area of a specific size on the surface of the object to be detected, the embodiment of the present application further sets the illumination light source 10 to a rectangular light source. In order to adapt to the actual detection scene, the embodiment of the present application also controls the distance between the object to be detected and the double Gaussian imaging system 30 along the direction of the outgoing light. Generally, the distance S between the object to be detected and the second single lens 304 along the outgoing light of the double Gaussian imaging system is set to between 35 mm and 200 mm.

[0048] As a preferred embodiment, the azimuth angle θ can be set to 45° and S can be set to 70 mm, thereby ensuring a specific size of the light spot presented by the illumination light source on the surface of the object to be detected.

[0049] Specifically, when θ=45° and S=70 mm, in order to ensure that the illumination light source can be imaged onto the surface of the object to be detected, the parameters of each lens in the double Gaussian imaging system 20 are set as follows in this embodiment of the application:

[0050] The first single lens 301 is set to be a convex lens, and the focal length range of the first single lens includes 49mm to 59mm; the first doublet lens 302 includes a convex lens and a concave lens arranged along the propagation direction of the main light, and the focal length range of the first doublet lens 302 includes -67mm to -57mm; the second doublet lens 303 includes a concave lens and a convex lens arranged along the propagation direction of the main light, and the focal length range of the second doublet lens 303 includes 43mm to 53mm; the second single lens is a convex lens 304, and the focal length range of the second single lens 304 includes 79mm to 89mm.

[0051] For ease of understanding, the following Table 1 provides a specific embodiment of optical parameters of the first single lens 301, the first doublet lens 302, the second doublet lens 303, the second single lens 304, and the turning prism 20 when the azimuth angle θ = 45° and S = 70 mm:

[0052] Table 1

[0053]

[0054] Among them: the radius of different surfaces is used to indicate the radius of different surfaces of the surface lens, the thickness is used to indicate the thickness of the lens, the refractive index and Abbe number are used to indicate the material of the lens, and the semi-aperture is used to indicate the diameter of the surface lens.

[0055] Specifically in the above table, the first single lens 301 is a convex lens with a positive focal length and a focal length of 54.41 mm.

[0056] The first doublet lens 302 is a cemented lens group consisting of a convex lens with a positive focal length and a concave lens with a negative focal length, with focal lengths of 28.56 mm and -12.86 mm respectively; the focal length of the cemented lens group is -61.93 mm.

[0057] The second doublet lens 303 is a cemented lens group consisting of a concave lens with a negative focal length and a convex lens with a positive focal length, with focal lengths of -12.28 mm and 19.05 mm respectively; the focal length of the cemented lens group is 48.304 mm.

[0058] The second single lens 304 is a convex lens with a positive focal length and a focal length of 84.06 mm.

[0059] Furthermore, in order to control the size of the light spot presented by the rectangular light source on the object to be detected, a turning prism 20 is added to the illumination system, so that the magnification of the illumination light source in the illumination system satisfies Schaum's law:

[0060] If the image of the rectangular light source on the object to be detected is a rectangular spot, and the angle between the outgoing light of the double Gaussian system and the first side of the rectangular spot is θ, and the angle between the outgoing light and the second side of the rectangular spot is 90°, then the magnification of the first side of the rectangular spot relative to the first side of the rectangular light source is m′, and the magnification of the second side of the rectangular spot relative to the second side of the rectangular light source is m, where:

[0061] in:

[0062] θ′ is the complementary angle between the image of the object to be detected passing through the double Gaussian imaging system and the angle between the main light.

[0063] For ease of understanding, Figure 2 A schematic diagram is given of the size of the light spot presented by the rectangular light source on the surface of the object to be detected when the rectangular light source is 12.5mm*1mm, θ=45°, and m=2.

[0064] Specifically, assuming that the angle between the outgoing light of the double Gaussian system and the length of the rectangular spot is θ, and the angle between the outgoing light of the double Gaussian system and the width of the rectangular spot is 90°, then according to the above formula, it can be obtained that:

[0065] The width of the rectangular light spot is relative to the width of the rectangular light source. If the magnification is 2, the width of the rectangular light spot is 2mm. Since the angle between the main light of the lighting system and the length of the rectangular light spot is θ, assuming that the length of the rectangular light spot is x, then:

[0066] tanθ=mtanθ′, so tan45°=2×tanθ′, so

[0067] Then θ′=26.565°;

[0068] but So x = 2.24*12.5 = 28 mm.

[0069] The embodiment of the present application provides a calculation process for causing a rectangular light source to present a light spot area of a specific size on the surface of the object to be detected. In actual application scenarios, as long as the magnification of the lighting system and the azimuth angle of the outgoing light and the surface normal of the object to be detected are set, the size of the rectangular light spot can be controlled according to Scham's law, thereby improving the convenience of obtaining a light spot area of a specific size.

[0070] Furthermore, in order to verify the quality of the light spot presented by the lighting system in the embodiment of the present application on the surface of the object to be detected, the embodiment of the present application also uses the optical system point array diagram to evaluate the imaging quality of the rectangular light source in the embodiment of the present application. For specific point array diagrams, please refer to Figure 3 In the embodiment of the present application, the RMS radius of the rectangular light spot is less than 30um, and the GEO radius is less than 70um. Moreover, since the imaging of the lighting system is performed in the embodiment of the present application, the diffusion requirement for the edge of the image is not high. Therefore, this imaging quality can achieve the function of sharp edges of the rectangular light spot image.

[0071] Furthermore, in order to more directly view the brightness and boundaries of the rectangular light spot, the embodiment of the present application Figure 4 A simulation diagram of the rectangular spot lighting effect is also given. In this simulation diagram, the horizontal and vertical coordinates represent the size of the spot, and the filling color in the simulation diagram is used to represent the incoherent irradiance of the rectangular spot, where white is 0, black is 3.98, and Figure 4 The rectangular area in the figure is all black, and the shape of the rectangular light spot is clear, so it can be determined that the rectangular light spot has a sharp boundary and the brightness within this rectangular area is very uniform.

[0072] Furthermore, the embodiment of the present application also provides a detection system, comprising an object to be detected and at least one group of Figure 1 The description of the lighting system is similar to that described in the above embodiment and will not be repeated here.

[0073] In order to further improve the brightness of the light source on the surface of the object to be detected, the embodiment of the present application can also set up multiple lighting systems for the object to be detected, and any two of the multiple lighting systems are axially symmetrically distributed relative to the normal of the object to be detected, wherein the multiple groups are at least 2 groups.

[0074] For ease of understanding, Figure 5 A structural diagram including the object to be detected and two lighting systems is given.

[0075] It should be noted that the object to be detected in the embodiment of the present application can be glass, film, wafer, etc., and there is no specific limitation on the type of the object to be detected.

[0076] As described above, the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that the technical solutions described in the above embodiments can still be modified, or some of the technical features thereof can be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A lighting system, characterized in that: include: An illumination light source of a preset shape, used for imaging onto the surface of the object to be inspected by means of critical illumination; a turning prism coaxially arranged with the illumination light source, for deflecting the illumination light emitted by the illumination light source, wherein the main light generated after the illumination light is deflected enters the double-Gauss imaging system; The double Gaussian imaging system is coaxially arranged with the principal ray, and is used to perform optical processing on the principal ray to generate outgoing light and irradiate the outgoing light onto the surface of the object to be detected at a preset azimuth angle θ, wherein the double Gaussian imaging system includes a first single lens, a first double-cemented lens, a second double-cemented lens, and a second single lens arranged in sequence along the incident direction of the principal ray, and the preset azimuth angle θ includes 40° to 50°.

2. The lighting system according to claim 1, wherein The magnification of the illumination system ranges from 1 to 3 times.

3. The lighting system according to claim 1, wherein The distance S between the object to be detected and the second single lens along the outgoing light is comprised between 35 mm and 200 mm.

4. The lighting system according to claim 3, characterized in that The S is 70 mm, and the θ is 45°.

5. The lighting system according to claim 4, characterized in that The first single lens is a convex lens, and the focal length range of the first single lens includes 49 mm to 59 mm; The first doublet lens includes a convex lens and a concave lens along the direction of the principal light, and the focal length range of the first doublet lens includes -67 mm to -57 mm; The second doublet lens includes a concave lens and a convex lens along the direction of the principal light, and the focal length of the second doublet lens ranges from 43 mm to 53 mm; The second single lens is a convex lens, and the focal length of the second single lens ranges from 79 mm to 89 mm.

6. The lighting system according to claim 1, wherein The illumination light source is a rectangular light source, and the RMS radius of the light spot presented by the rectangular light source on the object to be detected is not greater than 30um, and the GEO radius of the light spot presented by the illumination light source on the object to be detected is not greater than 70um.

7. The lighting system according to claim 1, wherein The illumination light source is a rectangular light source. If the image of the rectangular light source on the object to be detected is a rectangular light spot, and the angle between the main light of the illumination system and the first side of the rectangular light spot is θ, and the angle between the main light of the illumination system and the second side of the rectangular light spot is 90°, then the magnification of the first side of the rectangular light spot relative to the first side corresponding to the rectangular light source is m′, and the magnification of the second side of the rectangular light spot relative to the second side corresponding to the rectangular light source is m, wherein: The θ′ is the complementary angle between the image of the object to be detected passing through the double Gaussian imaging system and the angle between the main light.

8. The lighting system according to claim 6, characterized in that The rectangular light spot of the rectangular light source on the object to be detected has a sharp boundary, and the illumination of the rectangular light spot is uniform.

9. A detection system, characterized in that: The device comprises at least an object to be detected and at least one lighting system according to any one of claims 1 to 8.

10. The detection system according to claim 9, characterized in that: The lighting system is divided into multiple groups, and any two groups among the multiple lighting systems are axially symmetrically distributed with respect to the normal line of the object to be detected, wherein the multiple groups are at least two groups.

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