Real-time Focusing Method and Device for Testing the Flatness of a Thin Sheet under a High-resolution Lens

Abstract

The present invention relates to a real-time focusing method for testing the flatness of a thin sheet under a high-resolution lens, and the implementation method is as follows: record the positions of standard line-shaped projections formed by light emitted by multiple light-emitting devices on a standard plane and the positions of standard intersection points of multiple standard line-shaped projections; keep the detection lens at a certain height position from the test plane, record the positions of detection line-shaped projections formed by light emitted by two light-emitting devices on the detection plane and the positions of detection intersection points of the two detection line-shaped projections, and adjust the relative position of the detection lens and the test plane according to the difference between the positions of the detection line-shaped projections and the standard projection positions; use the difference in the positions of line-shaped projections formed by light emitted by multiple light-emitting devices within the field of view of the detection lens and the difference in the positions of line projection intersection points as a standard to adjust the relative position of the detection lens and the test plane, so as to achieve the purpose of rapid regional focusing and be able to quickly and efficiently detect the flatness.

Description

Technical Field

[0001] The present invention relates to the technical field of thin sheet flatness detection, and more specifically, to a real-time focusing method and device for testing the flatness of a thin sheet under a high-resolution lens. Background Art

[0002] Thin sheet-like objects have an optical characteristic under a high-resolution lens, that is, the depth of field is particularly small, for example, less than 0.2 mm, while the flatness or evenness of the object to be measured is much larger than the depth of field; generally in a static situation, to test such an object, after automatic adjustment or manual adjustment, normal testing can be carried out; however, for testing larger area objects, the conventional method is difficult to apply; the focus of the object to be measured can also be detected by measuring the sharpness of a standard image, but it can only focus on the position near the center point of the image, and cannot achieve focusing the entire FOV within the depth of field.

[0003] Taking the stencil widely used for printing on the SMT production line as an example, the main function of the stencil is to transfer an accurate amount of solder paste to the accurate position on the empty PCB. For products with high-precision printing requirements such as MINILED, the flatness of the stencil is particularly important. Therefore, it is necessary to accurately measure the flatness of the stencil.

[0004] However, there are the following problems in the current stencil detection on the production line: 1. It can only be manually measured by simple measuring tools; 2. It is inconvenient to use measuring tools to measure the finished stencil, with cumbersome operations and long time; 3. After the stencil on the production line is used for a period of time, the flatness of the stencil will change, and timely tracking is required; 4. It is impossible to predict how long the stencil will be used before the flatness changes; 5. Due to the rolling direction of the steel sheet, the reflection intensity of the light source in different directions varies greatly. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a real-time focusing method and device for testing the flatness of a thin sheet under a high-resolution lens in view of the above-mentioned defects of the prior art.

[0006] The technical solution adopted by the present invention to solve its technical problems is:

[0007] Construct a real-time focusing method for testing the flatness of a thin sheet under a high-resolution lens, wherein the implementation method is as follows:

[0008] Apply a detection lens and a plurality of light-emitting devices, the light-emitting devices emit light at an oblique angle to form a line-shaped projection within the field of view of the detection lens, and two adjacent line-shaped projections among the plurality of line-shaped projections intersect.

[0009] Calibration:

[0010] Keep the detection lens at a set height position from the standard plane, and record the positions of the standard line-shaped projections formed by the light emitted by multiple light-emitting devices on the standard plane and the positions of the standard intersection points of multiple standard line-shaped projections;

[0011] Test:

[0012] Keep the detection lens at a certain height position from the test plane, record the positions of the detection line-shaped projections formed by the light emitted by two light-emitting devices on the test plane and the positions of the detection intersection points of the two detection line-shaped projections, and adjust the relative position between the detection lens and the test plane according to the difference between the position of the detection line-shaped projection and the standard projection position;

[0013] When the differences between all the positions of the detection line-shaped projections and the standard projection positions and the differences between all the positions of the detection intersection points and the corresponding standard intersection points are within the set error range, the area focusing is completed.

[0014] The real-time focusing method for testing the flatness of a thin sheet under a high-resolution lens according to the present invention, wherein the method further includes:

[0015] Divide the area to be detected on the object to be measured into multiple sub-areas, move the detection lens and the light-emitting device to focus on each sub-area one by one and take pictures to obtain images.

[0016] The real-time focusing method for testing the flatness of a thin sheet under a high-resolution lens according to the present invention, wherein the method for adjusting the relative position between the detection lens and the test plane is:

[0017] Adjust the height of the detection lens or adjust the height of the test plane.

[0018] The real-time focusing method for testing the flatness of a thin sheet under a high-resolution lens according to the present invention, wherein the formula for adjusting the height of the detection lens or adjusting the height h of the test plane is:

[0019] h = d * tan(a) * pixel;

[0020] Wherein, d is the difference between the position of the detection line-shaped projection and the standard projection position, a is the angle between the light emitted by the light-emitting device and the vertical direction, and pixel is the resolution ratio of the detection lens.

[0021] The real-time focusing method for testing the flatness of a thin sheet under a high-resolution lens according to the present invention, wherein the method for adjusting the height of the test plane is:

[0022] Precision drive motors are arranged at the four corner positions of the test plane, and the up and down micro-movements of each position are precisely controlled by adjusting the four precision drive motors.

[0023] The real-time focusing method for testing the flatness of a thin sheet under a high-resolution lens according to the present invention, wherein two adjacent linear projections among a plurality of linear projections are perpendicular to each other.

[0024] The real-time focusing method for testing the flatness of a thin sheet under a high-resolution lens according to the present invention, wherein the light emitting device is a laser emitter.

[0025] A real-time focusing device for testing the flatness of a thin sheet under a high-resolution lens, which includes a detection lens and a plurality of light emitting devices. The light emitting devices emit light at an oblique angle to form linear projections within the field of view of the detection lens, and two adjacent linear projections among the plurality of linear projections intersect; the device further includes a distance adjustment mechanism for adjusting the relative position between the detection lens and the test plane.

[0026] The real-time focusing device for testing the flatness of a thin sheet under a high-resolution lens according to the present invention, wherein the distance adjustment mechanism includes a Z-axis module for adjusting the height of the detection lens and / or four Z-axis units respectively corresponding to adjusting the heights of the four corners of the test plane.

[0027] The real-time focusing device for testing the flatness of a thin sheet under a high-resolution lens according to the present invention, wherein the device further includes an XY-axis module for driving the detection lens and the plurality of light emitting devices to move along the X-axis and the Y-axis.

[0028] The beneficial effect of the present invention is that the relative position between the detection lens and the test plane is adjusted based on the position difference of the linear projections formed by the light emitted from a plurality of light emitting devices within the field of view of the detection lens and the position difference of the intersection points of the linear projections, so as to achieve the purpose of rapid regional focusing and be able to quickly and efficiently detect the flatness. Description of the Drawings

[0029] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will further illustrate the present invention in conjunction with the drawings and embodiments. The drawings in the following description are only partial embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts:

[0030] Figure 1 is the flowchart of the real-time focusing method for testing the flatness of a thin sheet under a high-resolution lens in a preferred embodiment of the present invention;

[0031] Figure 2 is the schematic diagram of the perpendicular projection of two laser beams in the real-time focusing method for testing the flatness of a thin sheet under a high-resolution lens in a preferred embodiment of the present invention;

[0032] Figure 3Schematic diagram of the vertical projection of three laser beams in the real-time focusing method for testing the flatness of a thin sheet under a high-resolution lens according to a preferred embodiment of the present invention;

[0033] Figure 4 Schematic diagram of the vertical projection of four laser beams in the real-time focusing method for testing the flatness of a thin sheet under a high-resolution lens according to a preferred embodiment of the present invention;

[0034] Figure 5 Schematic diagram of the internal angle laser in the real-time focusing method for testing the flatness of a thin sheet under a high-resolution lens according to a preferred embodiment of the present invention;

[0035] Figure 6 Schematic diagram of the external angle laser in the real-time focusing method for testing the flatness of a thin sheet under a high-resolution lens according to a preferred embodiment of the present invention;

[0036] Figure 7 Schematic diagram of making fine adjustments in the Z-axis direction according to different depth-of-field requirements in the real-time focusing method for testing the flatness of a thin sheet under a high-resolution lens according to a preferred embodiment of the present invention;

[0037] Figure 8 Schematic diagram of the structure of the real-time focusing device for testing the flatness of a thin sheet under a high-resolution lens according to a preferred embodiment of the present invention;

[0038] Figure 9 Schematic diagram of the parallelism between the actual test line and the standard line of the invention;

[0039] Figure 10 Schematic diagram of the angle between the actual test line and the standard line of the invention. Detailed implementation

[0040] In order to make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0041] The real-time focusing method for testing the flatness of a thin sheet under a high-resolution lens according to a preferred embodiment of the present invention, as Figure 1 shown, is implemented as follows:

[0042] Apply a detection lens and multiple light-emitting devices. The light-emitting devices emit light at an oblique angle to form line-shaped projections within the field of view of the detection lens, and two adjacent line-shaped projections among the multiple line-shaped projections intersect;

[0043] S01: Calibration:

[0044] Keep the detection lens at a set height position from the standard plane (such as using a 00-level plane, etc., without flatness problems), record the positions of the standard line-shaped projections formed by the light rays emitted by multiple light-emitting devices on the standard plane, and the positions of the standard intersection points of the multiple standard line-shaped projections;

[0045] S02: Testing:

[0046] Keep the detection lens at a certain height position from the test plane, record the positions of the detected line-shaped projections formed by the light rays emitted by two light-emitting devices on the test plane, and the positions of the detected intersection points of the two detected line-shaped projections. Adjust the relative position of the detection lens and the test plane according to the difference between the position of the detected line-shaped projection and the standard projection position;

[0047] When the differences between all the positions of the detected line-shaped projections and the standard projection positions, and the differences between all the positions of the detected intersection points and the corresponding standard intersection points are within the set error range, the area focusing is completed;

[0048] Take the differences in the positions of the line-shaped projections formed by the light rays emitted by multiple light-emitting devices within the field of view of the detection lens and the differences in the positions of the intersections of the line projections as the standard to adjust the relative position of the detection lens and the test plane, so as to achieve the purpose of rapid area focusing and be able to detect the flatness quickly and efficiently.

[0049] It should be noted that a certain height position in this application means that the detection lens can form a line-shaped projection within the field of view of the detection lens at any distance from the test plane;

[0050] Preferably, the method further includes:

[0051] S03: Repeat the second step until the entire plane is detected;

[0052] Divide the area to be detected on the object to be measured into multiple sub-areas, move the detection lens and the light-emitting device to focus on and take pictures of the multiple sub-areas one by one to obtain images;

[0053] After the standard setting in the first step is completed, the area focusing detection in the second step can be carried out immediately. After each area is detected, it is horizontally moved to the adjacent next area to repeat the area focusing detection action in the second step. When repeating the detection, the "certain height position" in the second step preferably adopts the height position of the detection lens when it is horizontally moved. Of course, according to needs, the vertical height can also be adjusted after the detection lens is horizontally moved to form a "certain height position". The two methods are determined according to actual needs and both belong to the protection scope of this application;

[0054] Preferably, the light-emitting device is a laser emitter. In the case of using laser, firstly, for products such as steel meshes where there are significant differences in the light reflection intensity due to the rolling direction of the steel sheets, it can ensure sufficient light intensity and the clarity of the light projection. Secondly, the light is more concentrated and straighter, ensuring the adjustment accuracy.

[0055] Within the field of view of the lens, multiple laser lines are projected at oblique angles. Experiments show that for the detection of the flatness of the entire plane which requires multiple position corrections, using a single laser dot structure does not work well during detection and cannot achieve the correction of the flatness of the entire plane. Using two laser lines in a cross shape is the most economical laser method, as Figure 2 shown. Of course, it is also possible to use the three-perpendicular method as shown in Figure 3 and the four-perpendicular method as shown in Figure 4 . If four lasers are used, it is very easy to solve the unevenness within the entire FOV.

[0056] For the layout of the laser generation, the angular laser can be an external angle or an internal angle. As Figure 5 shown, the advantage of the internal angle is that the head space is very small, but it is easy to interfere with other structures in the head (such as the angular light source). As Figure 6 shown, the advantage of the external angle is that it does not interfere with existing other structures, and the disadvantage is that the structure will be relatively large.

[0057] Preferably, the method for adjusting the relative position of the detection lens and the test plane is as follows:

[0058] Adjust the height of the detection lens or the height of the test plane. When adjusting the height of the detection lens or the height h of the test plane, the formula is used:

[0059] h = d * tan(a) * pixel;

[0060] where d is the difference between the position of the detected line-shaped projection and the standard projection position, a is the angle between the light emitted by the light-emitting device and the vertical direction, and pixel is the resolution ratio of the detection lens.

[0061] Preferably, the method for adjusting the height of the test plane is as follows:

[0062] Precision drive motors are set at the four corner positions of the test plane. By adjusting the four precision drive motors, the up-and-down micro-movement of each position can be accurately controlled. The up-and-down micro-movement of the four corners of the test plane by the precision drive motors can be achieved through the existing cam drive form or the existing linkage drive form; of course, it can also be replaced with other existing forms, such as pneumatic adjustment methods such as cylinders, etc.;

[0063] The laser generator can move in the XY plane along with the detection lens; in the Z direction, the laser generator can be fixed (by adjusting the test plane) or can move up and down in the Z direction following the detection lens (by adjusting the test lens).

[0064] As Figure 7 shown, the arc-shaped line represents the flatness curve, and the square represents the focal height position where a photo needs to be taken;

[0065] A real-time focusing device for testing the flatness of a thin sheet under a high-resolution lens, as Figure 8 shown, includes a detection lens 1 and a plurality of light-emitting devices 2. The light-emitting devices 2 emit light at an oblique angle to form a linear projection within the field of view of the detection lens 1, and two adjacent linear projections among the multiple linear projections intersect; the device also includes a distance adjustment mechanism for adjusting the relative position between the detection lens and the test plane 4; obtaining the standard data of the intersecting light projections of two or more light-emitting devices 2 projected onto a standard plane. During detection, the position is adjusted through the distance adjustment mechanism so that each light projection and the projection intersection point are as close as possible to the standard data. When the adjustment reaches a position error within an acceptable range, it can be determined that the plane to be measured is within the focal depth range of the test lens;

[0066] It should be noted that during adjustment, it can be done in the way of precise calculation as described above, or it can be manually adjusted (manually observing the position of the linear projection and the projection intersection point with the naked eye and adjusting the lens height and / or the test plane accordingly). Of course, the efficiency of manual adjustment relying on this device is also much higher than the existing test methods.

[0067] Preferably, the distance adjustment mechanism includes a Z-axis module 3 for adjusting the height of the detection lens and / or four Z-axis units respectively corresponding to adjusting the heights of the four corners of the test plane;

[0068] That is, the detection lens can be driven to move in the Z direction by the Z-axis module 3 to adjust the distance, or the four Z-axis units can be used to adjust the up and down micro-movement of the corners of the detection plane to adjust the distance, or a combination of both can be used; the Z-axis unit can be realized by using existing methods such as a motor with a cam mechanism, a connecting rod mechanism, a lead screw mechanism, etc., or a cylinder can also be used. Such conventional transformations all fall within the scope of protection of this application.

[0069] The device also includes an XY-axis module for driving the detection lens 1 and a plurality of light-emitting devices 2 to move along the X-axis and the Y-axis; it is convenient to perform detection on multiple partitions one by one; the XY-axis module can use existing equipment.

[0070] The calibration relationship between the four corner positions and the Z-axis:

[0071] First, determine the position of the lens focus. After the focus position is determined, use multiple laser generators to emit laser lines respectively. Through central fitting, a theoretical straight line in the horizontal or vertical direction (related to the orientation of the laser generator) is obtained, and the coordinate relationship of the straight line is recorded. Here, if there are two laser generators, there are two theoretical straight lines and one intersection point. If there are four laser generators, there are four theoretical straight lines and four intersection points. The intersection points of adjacent two theoretical straight lines need to verify the right-angle relationship to ensure that the measured plane is perpendicular to the optical center of the lens.

[0072] If the actual test line and its corresponding calibration line are parallel, only the Z-axis needs to be adjusted for focusing.

[0073] As Figure 9 shown, if one or more of the following situations occur for the actual test line, such as defocus, thickening of the line, and the intersection point of adjacent actual test lines not being at the theoretical position, then it is necessary to analyze the coordinate difference (dx, dy) between the intersection point of the actual test line and the center of the theoretical test position to determine the adjustment parameters:

[0074] a. If dx = dy, only the height of the Z-axis needs to be adjusted to make the test intersection point overlap with the theoretical intersection point.

[0075] b. If dx!= dy, as Figure 10 shown in the right projection, it can be seen that there is an angle between the black measured position and the green theoretical position. At this time, only adjusting the Z-axis cannot meet the requirement that the measured plane is parallel to the theoretical plane. Then, it is necessary to adjust the support feet according to the difference between dx and dy to make the actual plane parallel to the theoretical plane, and then adjust the Z-axis.

[0076] Similarly, if there is profiling distortion between the measured line and the theoretical line, calculate the change values of each support point according to the angle between the straight lines and the values of dx and dy until the test straight line is parallel to the theoretical straight line.

[0077] It should be understood that those of ordinary skill in the art can make improvements or transformations according to the above description, and all such improvements and transformations should fall within the protection scope of the appended claims of the present invention.

Claims

1. A real-time focusing method for testing the flatness of a thin sheet under a high-resolution lens, characterized in that, The implementation method is as follows: Apply a detection lens and multiple light-emitting devices. The light-emitting devices emit light at an oblique angle to form linear projections within the field of view of the detection lens, and two adjacent linear projections among multiple linear projections intersect; Calibration: Keep the detection lens at a set height position from the standard plane, and record the positions of the standard linear projections formed by the light emitted by multiple light-emitting devices on the standard plane and the positions of the standard intersection points of multiple standard linear projections; Testing: The detection lens is at a certain height position from the test plane. Record the positions of the detection linear projections formed by the light emitted by two light-emitting devices on the test plane and the positions of the detection intersection points of the two detection linear projections. Adjust the relative position of the detection lens and the test plane according to the difference between the positions of the detection linear projections and the standard projection positions; When the differences between all the positions of the detection linear projections and the standard projection positions and the differences between all the positions of the detection intersection points and the corresponding standard intersection points are within the set error range, the area focusing is completed.

2. The real-time focusing method for testing the flatness of a thin sheet under a high-resolution lens according to claim 1, characterized in that, The method further includes: Divide the area to be detected on the object to be measured into multiple sub-areas, move the detection lens and the light-emitting devices to focus on each of the multiple sub-areas one by one and take pictures to obtain images.

3. The real-time focusing method for testing the flatness of a thin sheet under a high-resolution lens according to claim 1, wherein, The method for adjusting the relative position of the detection lens and the test plane is: Adjust the height of the detection lens or adjust the height of the test plane.

4. The real-time focusing method for testing the flatness of a thin sheet under a high-resolution lens according to claim 3, characterized in that, Adjusting the height of the detection lens or adjusting the height h of the test plane uses the formula: h = d * tan(a) * pixel; Where d is the difference between the positions of the detection linear projection and the standard projection, a is the angle between the light emitted by the light-emitting device and the vertical direction, and pixel is the resolution ratio of the detection lens.

5. The real-time focusing method for testing the flatness of a thin sheet under a high-resolution lens according to claim 3 or 4, characterized in that, The method for adjusting the height of the test plane is: Set precision drive motors at the four corner positions of the test plane, and precisely control the up and down micro-movements of each position by adjusting the four precision drive motors.

6. The real-time focusing method for testing the flatness of a thin sheet under a high-resolution lens according to any one of claims 1-3, characterized in that, Two adjacent linear projections among multiple linear projections are perpendicular to each other.

7. The real-time focusing method for testing the flatness of a thin sheet under a high-resolution lens according to any one of claims 1-3, characterized in that The light-emitting device is a laser emitter.

8. A real-time focusing device for testing the flatness of a thin sheet under a high-resolution lens, which is used to implement the real-time focusing method for testing the flatness of a thin sheet under a high-resolution lens according to any one of claims 1-7, characterized in that, It includes a detection lens and multiple light-emitting devices. The light-emitting devices emit light at an oblique angle to form linear projections within the field of view of the detection lens, and two adjacent linear projections among multiple linear projections intersect; the device further includes a distance adjustment mechanism for adjusting the relative position of the detection lens and the test plane.

9. The real-time focusing device for testing the flatness of a thin sheet under a high-resolution lens according to claim 8, wherein, The distance adjustment mechanism includes a Z-axis module for adjusting the height of the detection lens and / or four Z-axis units respectively corresponding to adjusting the heights of the four corner positions of the test plane.

10. The real-time focusing device for testing the flatness of a thin sheet under a high-resolution lens according to claim 8, wherein, The device further includes an XY-axis module for driving the detection lens and multiple light-emitting devices to move along the X-axis and the Y-axis.

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