Imaging device and use method of imaging device

Abstract

The invention discloses an imaging device and a use method of the imaging device, which are suitable for detecting defects on a flexible circuit board and comprise a camera, a high-angle light source, a beam splitter and a bowl-shaped light source. Through the combination of the multi-directional light sources and the use of the high-angle light source, the surface of a product can generate light reflection of different degrees, three-dimensional information of FPC product defects can be comprehensively obtained, background information can be inhibited, and excessive light reflection caused by flexible deformation and circuit edges can be effectively eliminated.

Description

Technical Field

[0001] This invention relates to the field of defect detection, and more specifically to an imaging device and a method of using the imaging device. Background Technology

[0002] For flexible circuit boards, due to the excessive reflection caused by deformation, excessive reflection caused by line edges, and the influence of complex backgrounds, mainstream 3D measurement methods essentially rely on good diffuse reflection characteristics. When applied to highly reflective surfaces like FPCs, data acquisition is prone to failure, and the robustness cannot meet the requirements of industrial production. Traditional fixed or simple zoned lighting cannot cope with the local high-intensity directional specular reflection caused by FPC deformation, and cannot actively and accurately control the incident angle of light to avoid the camera's field of view, resulting in high difficulty in defect detection of FPCs. Summary of the Invention

[0003] The purpose of this invention is to overcome the aforementioned defects or problems existing in the prior art or to provide a material basis for overcoming the aforementioned defects or problems existing in the prior art, and to provide an imaging device and a method of using the imaging device.

[0004] To achieve the above objectives, the present invention and its preferred embodiments employ the following technical solutions, but the embodiments are not limited to the following solutions: Option 1: An imaging device suitable for detecting defects on flexible circuit boards, including... A camera adapted to receive signals reflected from the surface of a flexible circuit board along a first direction; A high-angle light source includes several concentrically arranged ring-shaped top light sources, each top light source being adapted to emit light in a direction perpendicular to a first direction. A beam splitter, located in the first direction of the camera and closer to the flexible circuit board than the camera, is adapted to allow signals reflected from the surface of the flexible circuit board to pass through and to reflect light from the top light source to the surface of the flexible circuit board. The bowl-shaped light source is open at both the top and bottom, and its inner diameter gradually increases along the first direction away from the camera. Several groups of multi-directional light sources are arranged along the first direction on it. The multi-directional light sources are arranged in a ring and are suitable for emitting light onto the surface of the flexible circuit board.

[0005] Option 2, based on Option 1, includes several sets of fan-shaped light sources for both the multi-directional light source and the top light source. The fan-shaped light sources are adapted to independently emit light onto the surface of the flexible circuit board.

[0006] Option 3, based on Option 1, involves a camera with a telecentric lens and multiple apertures, each with a different aperture size.

[0007] Option 4, based on Option 1, also includes a ring light source, which is located in the first direction of the bowl-shaped light source, arranged in a ring shape, and is suitable for emitting light onto the surface of the flexible circuit board.

[0008] Option 5, a method of using an imaging device, based on any one of Options 1 to 4, includes the following steps: Based on a lighting strategy that gradually increases or decreases the reflectivity of the flexible circuit board surface, the multi-directional light source and the top light source are turned on and / or turned off, and the camera acquires an image of the flexible circuit board surface; the light intensity of feature points is calculated based on the image until the light intensity of feature points between two adjacent images satisfies the following formula: ; Where I1 and I2 are the light intensities of feature points in the two images, and M is a fixed threshold; the lighting method corresponding to I1 is used as the lighting method when detecting defects.

[0009] Option 6, based on Option 5, Under the Lambertian diffuse reflection model, the light intensity I at surface feature points satisfies: ; Where I: the light intensity of surface feature points in the imaging system; The diffuse reflectance of a surface at that point is used to characterize the material's ability to reflect incident light. L: The unit vector of the incident light direction, used to represent the direction of illumination; N: The unit normal vector at the surface feature point, used to represent the local geometric orientation of that point; ( ): The dot product of vectors L and N is equivalent to cosθ, where θ is the angle between the incident light direction and the surface normal direction.

[0010] Option 7, based on Option 5, the camera has a telecentric lens, and the telecentric lens has a variable aperture; initially, the above steps are performed with the smallest aperture, and after obtaining the lighting method used when detecting defects, the camera is gradually adjusted so that the telecentric lens receives the brightness changes of the defects that are just in line with the illumination imaging.

[0011] As can be seen from the above description of the present invention and its preferred embodiments, compared with the prior art, the technical solution of the present invention and its preferred embodiments have the following beneficial effects due to the adoption of the following technical means: An imaging device suitable for detecting defects on a flexible circuit board includes a camera, a high-angle light source, a beam splitter, and a bowl-shaped light source.

[0012] The camera is adapted to receive signals reflected from the surface of the flexible circuit board along a first direction in order to obtain corresponding images and determine whether there are defects. The high-angle light source includes several concentrically arranged top light sources, which are adapted to emit light in a direction perpendicular to the first direction. The beam splitter is located in the first direction of the camera and is closer to the flexible circuit board than the camera. It is adapted to allow the signal reflected from the surface of the flexible circuit board to pass through, thereby preventing it from affecting the camera's detection of defects. It is also adapted to reflect the light from the top light sources onto the surface of the flexible circuit board, so that the light emitted by the top light sources can act on the surface of the flexible circuit board without directly pointing at it, thus compensating for the problem that the high-angle light source cannot be set up due to the camera.

[0013] The bowl-shaped light source is open at both the top and bottom, and its inner diameter gradually increases along the first direction away from the camera. Several groups of multi-directional light sources are arranged along the first direction on it. The multi-directional light sources are arranged in a ring and are suitable for emitting light onto the surface of the flexible circuit board. By combining the multi-directional light sources and using high-angle light sources, the product surface can produce different degrees of reflection. This can comprehensively obtain three-dimensional information of FPC product defects while suppressing background information and effectively eliminating excessive reflection caused by flexible deformation and line edges. Attached Figure Description

[0014] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0015] Figure 1 This is a schematic diagram of the imaging device in Embodiment 1; Figure 2 This is a top view of the imaging device in Embodiment 1; Figure 3 A schematic diagram illustrating excessive reflection in a flexible circuit board.

[0016] Explanation of key figure labels: FPC product 1; Defect 2; Ring light source 3; Multi-directional light source 4; Beam splitter 5; Telecentric lens 6; Camera 7; Power supply 8; PC 9; Trigger 10; Light source controller 11; Top light source 12; Detailed Implementation The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are preferred embodiments of the present invention and should not be considered as excluding other embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0017] Unless otherwise expressly defined, the use of terms such as "first," "second," or "third" in the claims, description, and accompanying drawings of this invention is for distinguishing different objects and not for describing a specific order.

[0018] Unless otherwise expressly defined, in the claims, description, and accompanying drawings of this invention, the use of directional terms such as "center," "lateral," "longitudinal," "horizontal," "vertical," "top," "bottom," "inner," "outer," "upper," "lower," "front," "rear," "left," "right," "clockwise," and "counterclockwise" to indicate orientation or positional relationships is based on the orientation and positional relationships shown in the accompanying drawings and is only for the convenience of describing the invention and simplifying the description, and is not intended to indicate or imply that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation, and therefore should not be construed as limiting the specific scope of protection of this invention.

[0019] Unless otherwise expressly defined, the terms "fixed connection" or "fixed connection" used in the claims, description and drawings of this invention should be interpreted broadly to refer to any connection in which there is no displacement or relative rotation relationship between the two parties, including non-removable fixed connection, detachable fixed connection, integral connection and fixed connection by other means or components.

[0020] In the claims, description and accompanying drawings of this invention, the terms "comprising," "having," and variations thereof are used to mean "including but not limited to."

[0021] refer to Figures 1-3 An imaging device suitable for detecting defects 2 on a flexible circuit board (FPC product 1), comprising a camera 7, a high-angle light source, a beam splitter 5, a bowl-shaped light source and a ring light source 3.

[0022] Camera 7 is adapted to receive signals reflected from the surface of the flexible circuit board along a first direction to obtain an image of the surface of the flexible circuit board, thereby facilitating the acquisition of information about defect 2 through the image.

[0023] The high-angle light source includes several concentrically arranged annular top light sources 12. The top light sources 12 are adapted to emit light in a direction perpendicular to the first direction. In this embodiment, there are two top light sources 12 to serve as the top light source.

[0024] The beam splitter 5 is located in the first direction of the camera 7 and is closer to the flexible circuit board than the camera 7. It is adapted to allow signals reflected from the surface of the flexible circuit board to pass through, thereby preventing the loss of information received by the camera 7. In addition, the beam splitter 5 is also adapted to reflect the light from the top light source 12 onto the surface of the flexible circuit board, so that the light emitted by the top light source 12 can also act on the surface of the flexible circuit board without directly pointing at it.

[0025] The bowl-shaped light source has openings at both the top and bottom. The upper opening ensures unobstructed information from the camera 7, while the lower opening allows light emitted from the light source to reach the surface of the flexible circuit board. The inner diameter of the bowl-shaped light source gradually increases along the first direction away from the camera 7. Several groups of multi-directional light sources 4 are arranged in a ring along the first direction on the bowl-shaped light source, suitable for emitting light onto the surface of the flexible circuit board. Both the multi-directional light source 4 and the top light source 12 are formed by several point light sources and emit light through diffuse reflection. Both the multi-directional light source 4 and the top light source 12 include several groups of fan-shaped light sources. These fan-shaped light sources are suitable for independently emitting light onto the surface of the flexible circuit board. The fan-shaped light sources are fan-shaped and emit light independently to provide directional illumination, facilitating the detection of minute defects 2 on the FPC surface. When all the fan-shaped light sources of the same multi-directional light source 4 are lit, full illumination is provided to meet the detection requirements of most defects 2.

[0026] The combination of these two light sources can satisfy the acquisition of the three-dimensional information of defect 2. When the top light source 12 and the multi-directional light source 4 are adjusted to obtain the best lighting method, the three-dimensional information of defect 2 can be obtained while suppressing background information, thereby eliminating excessive reflection.

[0027] The ring light source 3 is located in the first direction of the bowl-shaped light source and is closer to the flexible circuit board than the camera 7. The ring light source 3 is arranged in a ring shape and is suitable for emitting light onto the surface of the flexible circuit board. It is responsible for providing a uniform, low-reflection imaging environment and is suitable for detecting edge or three-dimensional defects 2.

[0028] The camera 7 has a telecentric lens 6, which has a continuously variable aperture. By adjusting the aperture of the lens, the information reflected from the defect 2 received by the camera 7 is precisely adjusted, thereby further ignoring background information.

[0029] Specifically, in this embodiment, for the high-angle light source, there are two top light sources 12, namely 1-1 and 1-2. For the bowl-shaped light source, there are six multi-directional light sources 4, defined from top to bottom as LED beads 1-3 to 1-8. Each multi-directional light source 4 and the top light source 12 has four fan-shaped light sources, corresponding to 0°, 90°, 180° and 270° respectively, for a total of 24 zoned light sources. Since each top light source 12 and each multi-directional light source 4 represents a different exposure height, it can accurately image defects 2 with different curvatures, while ensuring a good signal-to-noise ratio of the image.

[0030] A method of using an imaging device, based on the aforementioned imaging device, includes the following steps: Initially, the telecentric lens 6 is set to use the smallest aperture. Based on the lighting strategy that gradually increases or decreases the reflectivity of the flexible circuit board surface, the multi-directional light source 4 and the top light source 12 are turned on and / or turned off, and the camera 7 acquires the surface image of the flexible circuit board; for example, all the multi-directional light sources 4 and the top light source 12 are turned on first, and then 1-1 to 1-8 are gradually turned off, or 1-8 to 1-1 are gradually turned on.

[0031] For example, when the product background has no or only minor deformation, the light emitted by the top light source 12 passes through the beam splitter 5 placed at a 45° angle and then strikes the flexible circuit board vertically, thus enabling the detection of the corresponding defect 2.

[0032] If the product background experiences warping or flexible deformation, it will cause excessive reflection, making it extremely difficult to detect unevenness / protrusion defects. Different degrees of flexible deformation require light sources at different heights. Therefore, the multi-directional light source 4 is adjusted by first lighting up all the LEDs (1-3 to 1-8), then sequentially turning off the topmost LED, i.e., turning off the topmost light source sequentially. Each time a light source is turned off, an image of the product is captured. By subtracting the previous image from the subsequent one and setting an appropriate threshold, if the threshold is exceeded, the previous light source is considered optimal; otherwise, the light sources are turned off sequentially.

[0033] The specific calculations are as follows: the lighting scheme further integrates the photometric stereo method. Under the Lambertian diffuse reflection model, the light intensity I at the surface feature points satisfies: ; I: The light intensity of surface feature points in the imaging system, i.e., gray intensity (which can be understood as the pixel intensity sampled by camera 7, and the unit can be relative gray value or irradiance correlation quantity).

[0034] The diffuse reflectance of a surface at a given point, also known as albedo, characterizes a material's ability to reflect incident light; it is typically set to 0. The dimensionless coefficient of 1.

[0035] L: The unit vector of the incident light direction, used to represent the direction of illumination.

[0036] N: The unit vector of the surface normal at the feature point, used to represent the local geometric orientation of that point.

[0037] ( The dot product of vectors L and N is equivalent to cosθ, where θ is the angle between the incident light direction and the surface normal direction. Physically, max(0, This is to avoid negative values ​​when backlit.

[0038] Calculate the light intensity of feature points based on the image until the light intensity of feature points between two adjacent images satisfies the following formula: ; Wherein, I1 (corresponding to the previous image mentioned above) and I2 (corresponding to the next image mentioned above) are the light intensities of the feature points of the two images, respectively, and M is a fixed threshold; The lighting method corresponding to I1 is used as the lighting method when detecting defect 2.

[0039] After obtaining the lighting method used when detecting defect 2, the method is gradually adjusted so that the telecentric lens 6 receives the light and shadow changes of defect 2 in a way that matches the illumination.

[0040] After determining the optimal layered illumination positions for defect detection (e.g., 1-3), based on the area ratio of newly added bright interference areas in the normal product image after adding the last layer of light source (e.g., to 1-4), combined with the pre-calibrated empirical coefficient k (the relationship between the areas of bright interference areas between the previous and subsequent positions after adjusting the telecentric lens aperture), the aperture mechanism of the telecentric lens is continuously adjusted by adjusting the telecentric lens aperture, so that the surface of the normal product is in a critical state where no obvious bright reflection occurs (e.g., the position is finely adjusted to 1-3.8 at this time) (more accurate than adjusting only the multi-directional light source 4). This is the optimal illumination condition for defect detection, so that when the last layer of light source is not added, the normal product is in a critical state where no bright reflection occurs. Once the degree of unevenness of the concave-convex defect is greater than the warp curvature range of the product itself, the defect will immediately become bright, thus being detected by the imaging algorithm, thereby achieving defect detection.

[0041] Therefore, the above-mentioned lighting method can be used to detect defect 2 in this product, and defect 2 can be displayed more clearly.

[0042] When warping and flexible deformation occur in the product, the multi-directional light source 4 (1-3 to 1-8) is first lit to take an image to detect minor defects 2 on the FPC surface; then the ring light source 3 is lit to take another image to detect edge or three-dimensional defects 2; finally, the algorithm combines the information from the two images to complete the overall defect 2 judgment.

[0043] In use, power is supplied to the camera 7, PC 9, trigger 10, light source controller 11, top light source 12, and multi-directional light source 4 via power supply 8. The light source controller 11 controls the activation and deactivation of the top light source 12 and multi-directional light source 4. After the camera 7 acquires a photo, it transmits it to the PC 9 for image analysis to determine the lighting method. Further adjustments are made by controlling the aperture of the camera 7 until the final working condition is determined.

[0044] This imaging device features a high-angle light source and a multi-directional light source 4 with multiple fan-shaped light sources to provide directional illumination. When all fan-shaped light sources are lit, full illumination is provided to meet the detection requirements of most defects 2. When the fan-shaped light sources are adjusted to obtain the optimal light source position, the three-dimensional information of defect 2 can be obtained while suppressing background information, thereby eliminating excessive reflection. It can comprehensively acquire the three-dimensional information of defect 2 in FPC product 1 while suppressing background information, effectively eliminating excessive reflection caused by flexible deformation and circuit edges.

[0045] Compared with the prior art, this embodiment has the following beneficial effects: In one exemplary embodiment, an imaging device adapted to detect defects 2 on a flexible circuit board includes a camera 7, a high-angle light source, a beam splitter 5, and a bowl-shaped light source.

[0046] Camera 7 is adapted to receive signals reflected from the surface of the flexible circuit board along a first direction in order to obtain a corresponding image and determine whether there is a defect 2. The high-angle light source includes several concentrically arranged top light sources 12, which are adapted to emit light in a direction perpendicular to the first direction. The beam splitter 5 is located in the first direction of the camera 7 and is closer to the flexible circuit board than the camera 7. It is adapted to allow the signal reflected from the surface of the flexible circuit board to pass through, thereby preventing the camera 7 from affecting the detection of defect 2, and is adapted to reflect the light from the top light sources 12 onto the surface of the flexible circuit board. This allows the light emitted by the top light sources 12 to act on the surface of the flexible circuit board without directly pointing at it, thus compensating for the problem that the high-angle light source cannot be set up due to the setting of the camera 7.

[0047] The bowl-shaped light source is open at both the top and bottom, and its inner diameter gradually increases along the first direction away from the camera 7. Several sets of multi-directional light sources 4 are arranged along the first direction on it. The multi-directional light sources 4 are arranged in a ring and are suitable for emitting light onto the surface of the flexible circuit board. By combining the multi-directional light sources 4 and using high-angle light sources, the product surface can produce different degrees of reflection. This can comprehensively obtain the three-dimensional information of the defects 2 of the FPC product 1 while suppressing background information and effectively eliminating excessive reflection caused by flexible deformation and line edges.

[0048] In one exemplary embodiment, both the multi-directional light source 4 and the top light source 12 include several sets of fan-shaped light sources. These fan-shaped light sources are adapted to independently emit light onto the surface of the flexible circuit board for independent illumination, preventing individual defects 2 from being missed due to the symmetrical arrangement of the light sources causing corresponding information to cancel each other out. Each fan-shaped light source can be individually lit and its brightness adjusted, essentially acting as a "detail enhancement layer" responsible for "revealing" minute defects 2, facilitating the detection of subtle defects 2 on the FPC surface.

[0049] In one exemplary embodiment, the camera 7 has a telecentric lens 6, and the telecentric lens 6 has a continuously variable aperture. By adjusting the aperture, the telecentric lens 6 receives the brightness changes of the illumination imaging defect 2 in a way that is just right, making it easier to detect the defect 2.

[0050] In one exemplary embodiment, the ring light source 3 can precisely control the light, eliminate blind spots and reflections, and illuminate the entire ring at once, providing uniform illumination. It serves as the "basic lighting layer" of the entire system, responsible for providing a uniform, low-reflection imaging environment, suitable for detecting edge or three-dimensional defects 2. Together with the multi-directional light source 4, it can stably and accurately detect various defects 2 on the FPC.

[0051] In one exemplary embodiment, a method of using an imaging device, based on the aforementioned imaging device, includes the following steps: Turn on top light source 12 and take a global preview image of the FPC; Select the effective region of the FPC as the region of interest; Calculate the variance of all pixel grayscale values ​​and the image edge gradient within the region of interest; Deformation evaluation index values ​​are calculated based on variance and image edge gradient to determine the magnitude of product deformation. When the product background has no or minimal deformation, top light source 12 is selected as the lighting method. When the product background undergoes warping or flexible deformation, based on a lighting strategy that gradually increases or decreases the surface reflection of the flexible circuit board, the multi-directional light source 4 is turned on and / or turned off, and the camera 7 acquires an image of the surface of the flexible circuit board; the light intensity of feature points is calculated based on the image until the light intensity of feature points between two images satisfies the following formula: ; Wherein, I1 and I2 are the light intensities of feature points in the two images, and M is a fixed threshold; the lighting method corresponding to I1 is used as the lighting method when detecting defect 2. Under this lighting method, background information can be suppressed, and excessive reflection caused by flexible deformation and line edge can be effectively eliminated, thereby ensuring that the detected abnormal value is more likely to be defect 2 and improving the detection rate.

[0052] The foregoing description of the specifications and embodiments is intended to explain the scope of protection of this invention, but does not constitute a limitation on the scope of protection of this invention. Modifications, equivalent substitutions, or other improvements to the embodiments of this invention or a portion thereof that can be obtained by those skilled in the art through logical analysis, reasoning, or limited experimentation, based on the teachings of this invention or the foregoing embodiments, in conjunction with common knowledge, general technical knowledge, and / or existing technology, should all be included within the scope of protection of this invention.

Claims

1. An imaging device suitable for detecting defects (2) on a flexible circuit board, characterized in that: include Camera (7), adapted to receive signals reflected from the surface of a flexible circuit board along a first direction; A high-angle light source includes several concentrically arranged ring light sources (3) and a ring-shaped top light source (12), the top light source (12) being adapted to emit light in a direction perpendicular to a first direction. A beam splitter (5) is located in the first direction of the camera (7) and closer to the flexible circuit board than the camera (7), and is adapted to allow signals reflected from the surface of the flexible circuit board to pass through, and to reflect the light from the top light source (12) to the surface of the flexible circuit board. The bowl-shaped light source has openings at the top and bottom, and its inner diameter gradually increases along the first direction away from the camera (7). Several groups of multi-directional light sources (4) are arranged along the first direction. The multi-directional light sources (4) are arranged in a ring and are suitable for emitting light onto the surface of the flexible circuit board.

2. The imaging device as described in claim 1, characterized in that: Both the multi-directional light source (4) and the top light source (12) include several sets of fan-shaped light sources, which are adapted to independently emit light onto the surface of the flexible circuit board.

3. The imaging device as described in claim 1, characterized in that: The camera (7) has a telecentric lens (6) and the telecentric lens (6) has a continuously variable aperture.

4. The imaging device as described in claim 1, characterized in that: It also includes a ring light source (3), which is located in the first direction of the bowl-shaped light source, is arranged in a ring shape, and is adapted to emit light onto the surface of the flexible circuit board.

5. A method of using an imaging device, characterized in that: An imaging device according to any one of claims 1-4 includes the following steps: Based on the lighting strategy that gradually increases or decreases the reflectivity of the flexible circuit board surface, the multi-directional light source (4) and the top light source (12) are turned on and / or off, and the camera (7) acquires an image of the flexible circuit board surface; the light intensity of the feature points is calculated based on the image until the light intensity of the feature points between two adjacent images satisfies the following formula: Where I1 and I2 are the light intensities of feature points in the two images, and M is a fixed threshold; the lighting method corresponding to I1 is used as the lighting method when detecting defects (2).

6. The method of using the imaging device as described in claim 5, characterized in that: Under the Lambertian diffuse reflection model, the light intensity I at surface feature points satisfies: ； Where I: the light intensity of surface feature points in the imaging system; The diffuse reflectance of a surface at that point is used to characterize the material's ability to reflect incident light. L: The unit vector of the incident light direction, used to represent the direction of illumination; N: The unit normal vector at the surface feature point, used to represent the local geometric orientation of that point; ( ): The dot product of vectors L and N is equivalent to cosθ, where θ is the angle between the incident light direction and the surface normal direction.

7. The method of using an imaging device as described in claim 5, characterized in that: The camera (7) has a telecentric lens (6) and the telecentric lens (6) has a continuously variable aperture. Initially, the above steps are performed with the aperture of the smallest aperture. After obtaining the lighting method used when detecting the defect (2), the camera is gradually adjusted so that the telecentric lens (6) receives the brightness changes of the imaging defect (2) in a way that matches the lighting.

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