A tin jet detection system

Abstract

The utility model discloses a kind of tin spraying detection systems, by being arranged in tin spraying detection system tin spraying device, control device, data processing device, image acquisition device and mechanical arm, tin spraying device is used to spray tin to each pad and form tin point, mechanical arm is used to control image acquisition device movement, control device is after each pad tin spraying is completed, control mechanical arm moves image acquisition device to substrate top, to obtain the detection image of each pad after tin spraying by image acquisition device, data processing device is used to judge whether detection image satisfies predetermined condition. Thus, quality detection can be carried out in real time during tin spraying process, and the product quality in production operation process is guaranteed.

Description

Technical Field

[0001] This utility model relates to the field of chip manufacturing, and in particular to a tin plating detection system. Background Technology

[0002] In the assembly process of camera modules, in order to meet the development needs of miniaturization and lightweight camera modules, the industry generally adopts the design of grooved ceramic substrates. However, this grooved structure places stringent requirements on the tinning process of the substrate. With its advantage of precise tinning, the spray tinning process has become the core tinning technology that is suitable for this grooved ceramic substrate.

[0003] The diameter of the solder dots in the tin-plating process directly determines the product yield. In actual production, the solder dot diameter needs to be strictly controlled within the range of 220 to 280 micrometers. Specifically, if the solder dot diameter is too large, it is easy to cause solder bridging between adjacent pads or components. If the solder dot diameter is too small, it will cause reliability problems such as cold solder joints. Therefore, both excessively large and excessively small solder dot diameters will directly affect the assembly quality and performance of the camera module.

[0004] Currently, the industry standard for detecting solder dot diameter is offline manual inspection. This means that after the substrate completes the soldering process, the product must be removed from the production line and transferred to a quality inspection room for individual measurement using measuring equipment. However, this method is inefficient and time-consuming, failing to meet the demands of large-scale mass production. Furthermore, it lacks real-time monitoring capabilities, leading to a large number of defective products. Therefore, developing a fast, efficient, and real-time measurement solution has become an urgent need to improve the yield rate of camera module production. Utility Model Content

[0005] In view of this, the present invention provides a solder spraying detection system that can perform real-time quality detection during the solder spraying process, thereby ensuring product quality during production operations.

[0006] This utility model embodiment provides a solder spraying detection system, the system comprising: A tin spraying device for spraying tin onto at least one pad to form tin dots on each pad, the at least one pad being disposed on a substrate; Image acquisition device, used to acquire inspection images of each solder pad after solder spraying; The control device is communicatively connected to the solder spraying device; The data processing device is communicatively connected to the control device; An image acquisition device is communicatively connected to the data processing device, and the image acquisition device is used to acquire detection images of each solder pad after solder spraying; A robotic arm, communicatively connected to the control device, is used to control the movement of the image acquisition device, or to control the movement of the image acquisition device and the solder spraying device. The data processing device is used to determine whether the detected image meets predetermined conditions, and the control device is used to control the robotic arm to move the image acquisition device or substrate after each solder pad is soldered so that the image acquisition device is positioned above the substrate.

[0007] The technical solution of this utility model embodiment includes a solder spraying device, a control device, a data processing device, an image acquisition device, and a robotic arm in the solder spraying inspection system. The solder spraying device sprays solder onto each pad to form solder dots. The robotic arm controls the movement of the image acquisition device. After solder spraying is completed on each pad, the control device moves the robotic arm to above the substrate so that the image acquisition device can acquire inspection images of each pad after solder spraying. The data processing device determines whether the inspection images meet predetermined conditions. Therefore, real-time quality inspection can be performed during the solder spraying process, ensuring product quality during production. Attached Figure Description

[0008] The above and other objects, features and advantages of the present invention will become clearer from the following description of embodiments of the present invention with reference to the accompanying drawings, in which: Figure 1 This is a graph showing the relationship between the solder spraying diameter and the amount of solder in a solder spraying device. Figure 2 This is a schematic diagram of the solder spraying detection system according to an embodiment of the present invention; Figure 3 This is a schematic diagram of the tin spraying device spraying tin onto the solder pads according to an embodiment of the present invention; Figure 4 This is a schematic diagram of the image acquisition device of this utility model acquiring detection images of each solder pad after solder spraying; Figure 5 This is a schematic diagram of binarizing the detected image according to an embodiment of the present invention; Figure 6 This is a schematic diagram illustrating the determination of the solder spot diameter based on a detection image according to an embodiment of this utility model; Figure 7 This is a schematic diagram of a solder pad according to an embodiment of the present invention. Detailed Implementation

[0009] The present application is described below based on embodiments, but it is not limited to these embodiments. In the detailed description of the present application below, certain specific details are described in detail. Those skilled in the art can fully understand the present application without these details. To avoid obscuring the substance of the present application, well-known methods, processes, flows, elements, and circuits are not described in detail.

[0010] Furthermore, those skilled in the art should understand that the accompanying drawings provided herein are for illustrative purposes only and are not necessarily drawn to scale.

[0011] Unless the context explicitly requires it, words such as "including" or "contains" throughout the application should be interpreted as including rather than exclusive or exhaustive; that is, meaning "including but not limited to".

[0012] In the description of this application, it should be understood that the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance. Furthermore, in the description of this application, unless otherwise stated, "a plurality of" means two or more.

[0013] Tin spraying, as a core tinning technology for adapting to recessed ceramic substrates, results in solder dots whose diameter is a key quality control indicator determining the yield of camera module production, directly impacting assembly reliability and long-term stability. In the precision manufacturing of camera modules, solder dots must simultaneously meet the electrical connection requirements of pads and capacitors, as well as adaptability to confined spaces. Therefore, the solder dot diameter must be strictly controlled within a predetermined range during actual production. Specifically, if the solder dot diameter exceeds the upper limit, excessive solder will spread within the recess, easily causing metal bridging between adjacent pads and between pads and surrounding capacitors, leading to solder bridging failures. This can cause short circuits and damage to precision electronic components, directly resulting in product scrap. Conversely, if the solder dot diameter is below the lower limit, the solder cannot adequately cover the pad surface and component leads, resulting in insufficient soldering contact area and inadequate intermetallic compound formation, leading to cold solder joints and significantly reducing the circuit connection stability of the camera module. In other words, if the diameter of the solder joint is too large or too small, it will directly damage the circuit connection integrity and structural assembly precision of the camera module, significantly reducing the product production yield and market competitiveness.

[0014] In the automated production process of tin plating, the stability of the solder dot diameter is easily affected by the dynamic changes in the amount of solder remaining in the syringe. Specifically, the solder supply system of the tin plating device delivers molten solder to the tin spray nozzle through the syringe. As production continues, the amount of solder in the syringe gradually decreases, causing changes in the solder supply pressure and flow rate, which in turn causes a synchronous deviation in the diameter of the solder dots sprayed onto the substrate pads. Figure 1 This is a graph showing the relationship between the solder spraying diameter and the amount of solder in a solder spraying device. The vertical axis represents the solder spraying diameter, which is the average diameter of the solder dots sprayed by the device under the conditions corresponding to the amount of solder on the horizontal axis. For example... Figure 1 As shown, the solder spraying diameter of the solder spraying device is positively correlated with the amount of solder; that is, the larger the amount of solder, the larger the spraying diameter. During assembly line operations, the amount of solder in the solder spraying device gradually decreases. Therefore, if offline methods are used to measure the solder dot diameter at the beginning of production, or if sampling inspection is used to detect the solder dots, it is impossible to detect diameter fluctuations caused by changes in the remaining solder amount in real time. In subsequent batch production, the solder dot diameter may still exceed the predetermined range due to the reduction in solder amount, leading to a large number of defective products and significant resource waste. Therefore, traditional offline inspection methods are insufficient to meet the real-time quality inspection requirements of the solder spraying process. Based on this, this utility model embodiment provides a solder spraying inspection system that can realize real-time detection of the solder dot diameter during production, ensuring product quality during the production process.

[0015] Figure 2 This is a schematic diagram of the solder spraying detection system according to an embodiment of the present invention, as shown below. Figure 2 As shown, the solder spraying inspection system includes a solder spraying device 1, an image acquisition device 2, a data processing device 3, a robotic arm 5, and a control device 6. In some embodiments, the solder spraying inspection system further includes an alarm device 4. Specifically, the solder spraying inspection system is used to perform solder spraying on each pad 71, 72, 73, and 74 on the substrate 7, and to perform quality inspection on the solder spraying results. Figure 1 The example given is a substrate 7 with four pads. It should be understood that the number of pads on the substrate 7 is not limited to this.

[0016] The solder spraying device 1 is used to spray solder onto at least one pad on the substrate 7 to form solder dots on each pad, wherein the solder dots partially cover the pads. Specifically, after the substrate 7 moves under the solder spraying device 1, the positioning component first ensures that the pad to be soldered is aligned with the spray nozzle of the solder spraying device 1. Then, the solder spraying device 1 conveys molten solder to the spray nozzle after filtering and heat preservation. By adjusting the spraying pressure and spraying time, solder dots are formed on the pads. After soldering is completed on the pad to be soldered, the spray nozzle of the solder spraying device 1 is moved to the next pad to be soldered, and the above operation is repeated until all pads on the substrate 7 have been soldered. The solder spraying device 1 stores the coordinate positions of each pad in advance. During the solder spraying operation, the control device 6 controls the drive device (not shown in the figure) to control the solder spraying device 1 to move directly above each pad and perform solder spraying.

[0017] Figure 3This is a schematic diagram of the solder spraying device spraying solder onto the solder pads according to an embodiment of the present invention, wherein, Figure 3 The image on the left shows the diagram before soldering, and the image on the right shows the diagram after soldering. Figure 3 As shown in the left figure, during the solder spraying process, the solder spraying nozzle of the solder spraying device 1 is located directly above the solder pad 71. The solder spraying device 1 sprays solder onto the solder pad through the solder spraying nozzle to form solder dots on the solder pad. As shown in the right figure, the solder dots partially cover the solder pad.

[0018] Image acquisition device 2 is used to acquire detection images of each solder pad after soldering. Specifically, image acquisition device 2 can be implemented using a CCD (Charge-Coupled Device) camera. A CCD camera is a digital camera that uses a charge-coupled device as its image sensor. It converts light signals into electrical signals through a CCD chip, processes them to generate digital images, and works as follows: the lens collects the light reflected from the object being photographed and projects it onto the photosensitive unit of the CCD chip. The photosensitive unit converts photons into charges and stores them, then outputs the charges in an orderly manner through a charge transfer mechanism, and obtains a digital image through analog-to-digital conversion. In some embodiments, image acquisition device 2 is parallel to the substrate 7. By setting image acquisition device 2 parallel to substrate 7, perspective distortion and shape distortion are avoided, ensuring that the actual size and outline of the photographed object are accurately reproduced in the photograph. Specifically, in this embodiment, by setting image acquisition device 2 parallel to substrate 7, the circular outline of the solder pads will not become elliptical due to tilted shooting, and the diameter of the solder points can accurately map the actual specifications, thus providing a reliable visual basis for subsequent data processing.

[0019] Figure 4 This is a schematic diagram of the image acquisition device of this utility model acquiring detection images of each solder pad after solder spraying, as shown in the embodiment. Figure 4 As shown, the image acquisition device 2 is located above the substrate 7 to capture images of the substrate 7. In some embodiments, when acquiring the detection image, the image acquisition device 2 is located directly above the substrate, thereby placing the substrate 7 at the center of the detection image. This allows full utilization of the optimal imaging quality area at the center of the lens, reducing the impact of edge distortion on the substrate and solder dot contours, ensuring clear imaging and accurate dimensional reproduction. This provides a foundation for subsequent processing of the detection image and improves the stability and efficiency of the solder plating detection.

[0020] The data processing device 3 is communicatively connected to the image acquisition device 2 and is used to determine whether the detected image meets predetermined conditions. Specifically, the data processing device 3 receives the detected image sent by the image acquisition device 2 and determines whether the detected image meets the predetermined conditions. The specific method for determining whether the detected image meets the predetermined conditions will be described below and will not be repeated here.

[0021] Alarm device 4 is used to provide an anomaly alert when the detected image does not meet predetermined conditions. Specifically, alarm device 4 can be implemented through an audible and visual alarm device or a production line linkage shutdown device. Taking the audible and visual alarm device as an example, after receiving the relevant control signal that the detected image does not meet the predetermined conditions, the audible and visual alarm device triggers the speaker to emit a continuous, intermittent alarm sound on the one hand, and activates the LED warning light to light up or flash on the other hand. Through the dual alerts of sound and vision, the device quickly guides the staff to locate the abnormal workstation, ensuring that the relevant staff can handle the situation in a timely manner.

[0022] The robotic arm 5 is used to control the movement of the substrate 7, or to control the movement of the solder spraying device 1 and the image acquisition device 2. In one optional implementation, the robotic arm 5 moves the substrate 7 below the solder spraying device 1. After solder spraying is completed on each pad, the robotic arm 5 controls the substrate 7 to move below the image acquisition device 2, so that the image acquisition device 2 can take a picture of the substrate 7 to obtain a detection image. In another optional implementation, the substrate 7 is fixed in a certain position, and the robotic arm 5 is respectively set to control the solder spraying device 1 and the image acquisition device 2 to move above the substrate 7 before and after solder spraying. Figure 2 The diagram shows the control board 7 of the robotic arm 5.

[0023] The control device 6 is communicatively connected to the solder spraying device 1, the data processing device 3, the alarm device 4, and the robotic arm 5, and serves as the control center of the entire solder spraying inspection system. Specifically, after the solder spraying device 1 has finished spraying solder onto each pad, the control device 6 controls the robotic arm 5 to move the substrate 7 below the image acquisition device 2, or controls the robotic arm 5 to move the image acquisition device 2 above the substrate. Figure 1The diagram shows the robotic arm 5 controlling the substrate 7 to move below the image acquisition device 2. The control device 6 is also used to control the alarm device 4 to operate when the detected image does not meet predetermined conditions. On one hand, after the solder spraying device 1 completes solder spraying on each pad, the control device 6 controls the robotic arm 5 to move the substrate 7 below the image acquisition device 2 and controls the image acquisition device 2 to acquire the detected image. On the other hand, when the data processing device 3 determines that the detected image does not meet predetermined conditions, the control device 6 receives the relevant non-compliance instruction sent by the data processing device 3 and controls the alarm device 4 to operate by sending an alarm instruction, thereby prompting relevant personnel to handle the situation.

[0024] In some embodiments, the system further includes a carrier plate 8, which corresponds to the solder spraying device 1 and is used to support the substrate 7.

[0025] The following describes the specific method by which the data processing device 3 determines whether the detected image meets predetermined conditions. In some embodiments, the data processing device 3 is further used to perform binarization processing on the detected image so that within the area of ​​the solder pad, the portion covered by the solder dot is in a first color, and the portion not covered by the solder dot is in a second color. Taking black as the first color and white as the second color as an example, specifically, after obtaining the detected image, since the solder pad itself has a color, it is easy to confuse it with the color of the solder dot. Therefore, it is first necessary to perform a binarization operation on the detected image to more clearly distinguish the portion covered by the solder dot and the portion not covered by the solder dot in the solder pad. Specifically, binarization is to convert a brightness image with a brightness value range of 0 to 255 into a binary image containing only two pixel values: pure black (brightness value of 0) and pure white (brightness value of 255) to highlight the target area, thereby achieving rapid separation of the target area from the background area. Specifically, by setting a brightness threshold T, the pixel brightness value of each pixel is compared with T. When the brightness value is less than T, the brightness value corresponding to that pixel is assigned a value of 0 to form a pure black pixel. When the brightness value is greater than or equal to T, the brightness value corresponding to that pixel is assigned a value of 255 to form a pure white pixel. For example, if the brightness threshold T is set to 55, and the brightness value of a certain pixel is 80, since the brightness value is greater than the brightness threshold T, the brightness value of that pixel is assigned a value of 255 to form a pure white pixel. Through the binarization processing of the detection image by the data processing device 3, the parts covered by solder joints and the parts not covered by solder joints in each pad are distinguished, which facilitates subsequent processing of the detection image.

[0026] Figure 5 This is a schematic diagram illustrating the binarization processing of the detection image according to an embodiment of the present invention, as shown below. Figure 5As shown, before binarization, the parts of each pad not covered by solder joints appear yellow, while the parts covered by solder joints appear dark gray. By setting a brightness threshold between the brightness values ​​of these two colors, binarization is performed on the detection image, making the parts of each pad not covered by solder joints pure white and the parts covered by solder joints pure black. This makes it easier to distinguish between the parts covered and not covered by solder joints in the detection image, facilitating subsequent image processing.

[0027] The following describes the specific method by which the data processing device 3 determines whether the detected image meets predetermined conditions. In some embodiments, the data processing device 3 is used to fit the outer contour of the tin spot in the detected image to obtain a target circle, and to determine whether the diameter of each target circle is within a first predetermined range. Figure 6 This is a schematic diagram illustrating the determination of the solder spot diameter based on a detection image according to an embodiment of this utility model. Figure 6 As shown, firstly, the positions of each pad are detected using a pre-set search box 21 and recognition box 22, thereby locating the solder points within the pads. Specifically, the search box 21 is used to determine the position of the substrate. Since the substrate 7 occupies a relatively large area in the image, the area of ​​the search box 21 is set relatively large to ensure that the range of the search box 21 can cover the substrate 7. After determining the position of the substrate 7 using the search box 21, the specific position of each solder point is determined by setting the recognition box 22. The area of ​​the recognition box 22 is set to be slightly smaller than the area of ​​the pad, so that it can completely cover the solder points on the pad. Figure 6 Only the identification box 22 corresponding to pad 71 is shown in the image; it should be understood that other pads also have similar identification boxes. Figure 6 As can be seen, since the area of ​​the recognition box 22 is slightly smaller than the area of ​​the pad 71, and the area of ​​the solder point is significantly smaller than the area of ​​the pad 71, the recognition box 22 can completely cover the solder point. After detecting the position of each solder point through the recognition box 22, the outer contour of each solder point is fitted to obtain the target circle. Specifically, the edge pixel set needs to be preprocessed first to remove abnormal pixels such as noise and breakpoints, and retain continuous and complete effective edge points. Then, the least squares circle fitting method is used based on the principle of minimizing the sum of the squares of the deviations between the distance from each effective edge point to the center of the ideal circle and the radius, and the center coordinates and radius are solved by matrix operations. It should be understood that other methods in the existing technology can also be used to fit the target circle, such as the RANSAC (RANSAC Robust Circle Fitting Algorithm), the Hough transform circle detection algorithm, and the geometric circle fitting algorithm.

[0028] After determining the target circle corresponding to each solder point through fitting, it is necessary to determine whether the diameter of each target circle is within a predetermined range. In some embodiments, the control device is further configured to: control the alarm device to operate when there is a target circle in the detection image whose diameter is not within the first predetermined range. Specifically, if there is a target circle in the detection image whose diameter is not within the first predetermined range, it indicates that the diameter of a solder point is not within the predetermined range, indicating that the solder spraying device 1 is malfunctioning, and the alarm device is controlled to operate to prompt relevant personnel to handle the situation. In some embodiments, the control device is further configured to: control the robotic arm to transfer the substrate to a predetermined position when the diameters of the target circles in the detection image are all within the first predetermined range. The predetermined position can be the next station on the production line. Specifically, when the diameters of each target circle are all within the first predetermined range, it indicates that the diameters of each solder point are within the predetermined range, indicating that the soldering device is operating normally. At this time, the soldering process is terminated by controlling the robotic arm 5 to transfer the substrate 7 to the next station on the production line.

[0029] However, if the diameter of the target circle obtained by fitting the solder dot profile is within the first predetermined range, it does not necessarily indicate that the solder spraying device 1 is working properly. Figure 7 This is a schematic diagram of a solder pad according to an embodiment of the present invention, as shown below. Figure 7 As shown, the solder spot is elliptical with a large eccentricity. In this case, the solder spot does not meet the process requirements, and the solder spraying device 1 is malfunctioning. Therefore, if the judgment is made solely by fitting a target circle and determining its diameter, the diameter of the target circle fitted to the solder spot profile may still be within a predetermined range. Therefore, while fitting the circle, it is necessary to determine whether the solder spot profile is quasi-circular, thereby improving the accuracy of solder spot quality detection. Specifically, the longest distance between the two points of each solder spot profile can be measured as the major axis, and the shortest distance between the two points as the minor axis, and the ratio of the major axis to the minor axis can be calculated. If the ratio of the major axis to the minor axis of the solder spot is greater than a predetermined threshold, it is determined that the detected image does not meet the predetermined conditions. For example, if the predetermined threshold is set to 1.2, then when the ratio of the major axis to the minor axis of a solder point in the detection image is 1.5, it indicates that the solder point is not within the preset error range and is not circular, but rather elliptical, irregular polygonal, or other non-circular shapes, indicating that the shape of the solder point is abnormal. In this case, it is determined that the detection image does not meet the predetermined conditions, and the alarm device 4 needs to be controlled by the control device 6 to alert the relevant personnel.

[0030] Besides determining whether a solder point is qualified by measuring its diameter, it can also be determined by determining its area. In some embodiments, the data processing device is used to determine whether the areas of the solder points in the detection image are all within a second predetermined range. Specifically, if the area of ​​the solder points in the detection image is within the second predetermined range, the detection image is determined to meet a predetermined condition; if the area of ​​the solder points in the detection image is not within the second predetermined range, the detection image is determined to not meet the predetermined condition. Since the area and diameter of a solder point can be correlated using the formula for the area of ​​a circle, the qualified area range can be derived from the target diameter range. Specifically, if the area of ​​each solder point is within the second predetermined range, it indicates that the diameter of each solder point meets the requirements, and the detection image is determined to meet the predetermined condition; if the area of ​​at least one solder point is not within the second predetermined range, the detection image is determined to not meet the predetermined condition. It should be understood that when determining whether a solder point is qualified by its area, it is also necessary to combine the ratio between the major and minor axes of the solder point's profile to determine whether the solder point is circular. If the area of ​​each solder point is within the second predetermined range and the shape of each solder point is circular, the detection image is determined to meet the predetermined condition.

[0031] This invention, in its embodiment, incorporates a solder spraying device, an image acquisition device, a data processing device, a robotic arm, and a control device within a solder spraying inspection system. The solder spraying device sprays solder onto each pad to form solder dots. The robotic arm controls the movement of the image acquisition device. After solder spraying is completed on each pad, the control device moves the robotic arm above the substrate to acquire inspection images of each pad after solder spraying. The data processing device determines whether the inspection images meet predetermined conditions. In some embodiments, if the predetermined conditions are not met, the control device activates an alarm device. This allows for real-time quality inspection during the solder spraying process, ensuring product quality throughout the production process.

[0032] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A solder spraying detection system, characterized in that, The system includes: A tin spraying device for spraying tin onto at least one pad to form tin dots on each pad, the at least one pad being disposed on a substrate; The control device is communicatively connected to the solder spraying device; The data processing device is communicatively connected to the control device; An image acquisition device is communicatively connected to the data processing device, and the image acquisition device is used to acquire detection images of each solder pad after solder spraying; A robotic arm, communicatively connected to the control device, is used to control the movement of the image acquisition device, or to control the movement of the image acquisition device and the solder spraying device. The data processing device is used to determine whether the detected image meets predetermined conditions, and the control device is used to control the robotic arm to move the image acquisition device or substrate after each pad is soldered so that the image acquisition device is positioned above the substrate.

2. The system according to claim 1, characterized in that, The system also includes: The carrier plate, corresponding to the solder spraying device, is used to support the substrate.

3. The system according to claim 2, characterized in that, The image acquisition device is parallel to the carrier plate.

4. The system according to claim 1, characterized in that, It also includes an alarm device and is communicatively connected to the control device; The control device is also used to control the alarm device to operate when the detected image does not meet predetermined conditions.

5. The system according to any one of claims 1-4, characterized in that, The data processing device is also used to perform binarization processing on each pad.

6. The system according to claim 4, characterized in that, The data processing device is used to fit the outer contour of the tin spot in the detection image to obtain the target circle, and to determine whether the diameter of each target circle is within a first predetermined range.

7. The system according to claim 6, characterized in that, The control device is also used for: When a target circle with a diameter outside the first predetermined range is present in the detected image, the alarm device is activated.

8. The system according to claim 6, characterized in that, The control device is also used for: When the diameters of the target circles in the detected image are all within a first predetermined range, the robotic arm is controlled to transfer the substrate to a predetermined position.

9. The system according to any one of claims 1-4, characterized in that, The data processing device is used to determine whether the areas of the tin spots in the detected image are all within a second predetermined range.

10. The system according to any one of claims 1-4, characterized in that, The image acquisition device is positioned directly above the substrate when acquiring the detection image.

Images