Micron-scale height measurement system and measurement method

Abstract

The invention discloses a micron-sized height measuring system and a micron-sized height measuring method, solves the problem of system complexity of a micron-sized height measuring system in the prior art, and has the beneficial effects of simple structure and capability of realizing object height measurement, and the specific scheme is as follows: the micron-sized height measuring system comprises a motion deflection platform, an object is arranged on the motion deflection platform and is driven by the motion deflection platform to rotate; the light source irradiates light towards an object. The control assembly is independently connected with the light source and the camera, the light source irradiates the surface of an object and is reflected into a lens of the camera, the camera shoots a first object image and transmits the first object image to the control assembly, and after the motion deflection platform drives the object to rotate by a set angle, the camera shoots an nth object image and transmits the nth object image to the control assembly. The control assembly performs gradient calculation of pixel points on the two object images to obtain the image pixel width of the object, and the control assembly converts the image pixel width of the object into height information of the object through a calculation model.

Description

Technical Field

[0001] The present invention relates to the field of height measurement, in particular to a micrometer-level height measurement system and a measurement method. Background Art

[0002] The statements in this section merely provide background information related to the present invention and do not necessarily constitute prior art.

[0003] With the continuous development of the chip field, the high integration and miniaturization of a large number of components and equipment require fast and accurate measurement. For the Z direction of micro-scale three-dimensional morphology, that is, the accurate measurement of height is an important calibration method for quality standards such as surface structure and surface features. Optical measurement is an ideal method. Its non-contact and fast characteristics give it great advantages in xy plane measurement. However, for the z-direction dimension, it is difficult to estimate the depth using a monocular method without prior knowledge. Binocular vision obtains the depth information of the target based on camera parallax. It has been proposed and developed for a long time and is a method that can be used to acquire three-dimensional data.

[0004] Traditional measurement uses multiple optical devices to obtain sequential images containing three-dimensional spatial information based on the principle of multi-viewpoints. However, the reconstruction accuracy and speed based on traditional methods have always been major computational challenges. The second-generation deep learning new methods also face the problems of insufficient learning data and model migration. In three-dimensional modeling and autonomous driving, the data required for target reconstruction can be supplemented by increasing the number of cameras to obtain multiple sequence images. However, in the field of microscopic vision measurement, the accuracy of binocular vision systems is still low, and huge original databases are difficult to obtain. Blindly increasing the number of devices and deep learning methods at this scale is not advisable. Summary of the invention

[0005] In view of the deficiencies in the prior art, the object of the present invention is to provide a micrometer-level height measurement system that can quickly and accurately achieve monocular height measurement of tiny height objects in image space.

[0006] In order to achieve the above object, the present invention is implemented through the following technical solutions:

[0007] A micrometer-level height measurement system, comprising:

[0008] A motion deflection platform, where an object is placed on the motion deflection platform and the object is driven to rotate by the motion deflection platform;

[0009] A light source, which is directed toward an object to shine light;

[0010] Camera, a camera has a lens;

[0011] A control component is separately and independently connected to a light source and a camera. The light source irradiates the surface of an object, and the light reflected from the object surface enters the camera lens, and the camera captures a first object image and transmits it to the control component. After the moving and deflecting platform rotates the object by a set angle, the camera captures an nth object image and transmits it to the control component. The control component calculates the gradient of pixel points of the two object images to obtain the image pixel width of the object. A calculation model is built in the control component. The calculation model obtains the height information of the object through the image pixel width of the object, the focal length of the lens, the shooting distance of the camera, the deflection angle of the object, the height of the object in the Z direction, and the angle between the line connecting the projection point of the object on the calibration plane to the optical center and the optical axis of the camera. The control component converts the image pixel width of the object into the height information of the object through the calculation model.

[0012] For a micron-level height measurement system as described above, before the control component obtains the image pixel width of the object, it is necessary to determine whether the size of the object is within the depth of field range or outside the depth of field range. If the size of the object is within the depth of field range, the control component directly obtains the image pixel width of the object.

[0013] For a micron-level height measurement system as described above, if the control component determines that the size of the object is outside the depth of field range, the control component respectively segments the obtained first object image and nth object image, calculates the focus evaluation parameters for each segmented part, calculates the step size according to the calculated focus evaluation parameter values, adjusts the focus position through the step size, and fuses multiple images with different focus positions through a fusion algorithm to obtain clear images in which each part of the first object image and the nth object image is within the depth of field range.

[0014] For a micron-level height measurement system as described above, the calculation of the focus evaluation parameters is obtained according to the gray values of pixel points in the segmented partial images of the first object image or the nth object image.

[0015] For a micron-level height measurement system as described above, the control component respectively extracts pixels from the first object image and the nth object image, calculates the gray gradient, locates the pixel position with the maximum gray gradient as the boundary line, calculates the entire image column by column along the direction perpendicular to its length, and takes the average value of the results as the edge pixel position of the first object image and the nth object image. This average value of the results is used as the image pixel width.

[0016] For a micron-level height measurement system as described above, the projection point of the object on the calibration plane is the projection points of the first point and the second point in the nth object image on the calibration plane, and the position of the second point in the nth object image is lower than the position of the first point.

[0017] A micron-level height measurement system as described above, the height of the object in the Z direction is obtained according to the distance between the second point and the rotation center of the moving deflection platform in the nth object image and the deflection angle of the object.

[0018] A micron-level height measurement system as described above, the moving yaw platform includes a base, a first rotating component is arranged on the base, a second rotating component is arranged at the movable end of the first rotating component, a flat plate is arranged on the second rotating component, and the flat plate supports the object;

[0019] The first rotating component and the second rotating component are respectively connected to the control component.

[0020] In a second aspect, the present invention also provides a micron-level height measurement method, including the following contents:

[0021] The moving yaw platform supports the object;

[0022] The light source irradiates the surface of the object, is reflected into the lens of the camera, and the camera captures the first object image and transmits it to the control component;

[0023] After the moving deflection platform drives the object to rotate by a set angle, the camera captures the nth object image and transmits it to the control component;

[0024] The control component performs gradient calculation on the pixel points of the two object images to obtain the image pixel width of the object. A calculation model is built in the control component, and the control component converts the image pixel width of the object into the height information of the object through the calculation model.

[0025] The beneficial effects of the present invention are as follows:

[0026] 1) For the measurement system provided by the present invention, only one camera is needed to capture the object image. The moving yaw platform drives the object to rotate, and multi-angle image acquisition data is obtained through the moving yaw platform. In this way, the two work together, and the control component performs gradient calculation on the pixel points of the object image to obtain the image pixel width of the object. The calibration method is simple. By building a calculation model, the image pixel width of the object is converted into the height information of the object. The overall structure is simple, with only one camera, which can give full play to the advantages of the monocular system and has small system errors.

[0027] 2) Before obtaining the image pixel width of the object in the present invention, it is necessary to judge whether the size of the object is within the depth of field or outside the depth of field. If it is within the depth of field, the image pixel width of the object can be directly obtained; if it is outside the depth of field, it is necessary to segment the object image, calculate the focus evaluation parameters and the movement of the step length for each part of the image segmentation, obtain multiple images in which each part is within the depth of field, and perform fusion to obtain a focused and clear image.

[0028] 3) The measurement system of the present invention is provided with a light source. By using the light source to highlight the height information of the object, it is beneficial for the camera to obtain the object image, and it is beneficial for the control component to extract the pixels of the object image. Then, the image gray gradient method is used to detect the position of the edge pixels of the image, and the entire image is calculated column by column along the direction perpendicular to its length to determine the pixel width of the image.

[0029] 4) The present invention selects the first point and the second point in the nth object image, obtains the projection points of these two points on the calibration plane, and obtains the deflection angle of the object, so that the height of the object in the Z direction can be obtained, and the angle between the line connecting the projection point of the object on the calibration plane to the optical center and the camera optical axis can also be obtained. Combining with the pixel width of the object image, a calculation model can be obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The attached drawings forming a part of the present invention are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation to the present invention.

[0031] Figure 1 is a schematic structural diagram of a micron-level height measurement system according to one or more embodiments of the present invention.

[0032] Figure 2 is a two-dimensional imaging schematic diagram of a micron-level height measurement system according to one or more embodiments of the present invention.

[0033] Figure 3 is a schematic diagram of the original image of an object in a micron-level height measurement system according to one or more embodiments of the present invention.

[0034] Figure 4 is a schematic diagram of the image after gray-scale transformation in a micron-level height measurement system according to one or more embodiments of the present invention.

[0035] Figure 5 is a schematic diagram of the construction of a calculation model in a micron-level height measurement system according to one or more embodiments of the present invention.

[0036] In the figure: The distances or sizes between each part are exaggerated for showing the positions of each part, and the schematic diagram is only for illustration. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0037] It should be noted that the following detailed description is illustrative and is intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention belongs.

[0038] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present invention. As used herein, unless the present invention clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should also be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof;

[0039] As introduced in the background art, there are problems with system complexity in micron-level height measurement systems in the prior art. To solve the above technical problems, the present invention proposes a micron-level height measurement system.

[0040] Embodiment 1

[0041] In a typical embodiment of the present invention, refer to Figure 1 、 Figure 2 As shown, a micron-level height measurement system includes:

[0042] A motion yaw platform, on which an object is placed and the object is rotated by the motion yaw platform;

[0043] A light source, which irradiates light towards the object to magnify the microscopic scene;

[0044] A camera, which has a lens;

[0045] A control component, which is separately connected to the light source and the camera. The light source irradiates the surface of the object. As shown in Figure 3 , it is reflected into the lens of the camera and the camera takes a first object image and transmits it to the control component. After the motion yaw platform drives the object to rotate by a set angle each time, an object image is taken. In this way, the camera takes the nth object image and transmits it to the control component. The nth object image refers to the image taken for the nth time, where n is a natural number and n is greater than or equal to 2. The control component performs gradient calculation on the pixel points of two object images to obtain the image pixel width of the object. A calculation model is built in the control component. The control component converts the image pixel width of the object into the height information of the object through the calculation model. The calculation model obtains the height information of the object through the image pixel width of the object, the lens focal length, the camera shooting distance, the yaw angle of the object, the height of the object in the Z direction, and the angle between the line connecting the projection point of the object on the calibration plane to the optical center and the camera optical axis.

[0046] In this embodiment, the motion yaw platform includes a base, a first rotating component is arranged on the base, a second rotating component is arranged at the movable end of the first rotating component, a flat plate is arranged on the second rotating component, and the flat plate supports an object; the first rotating component and the second rotating component are respectively connected to a servo driver, and the servo driver is connected to a control component. The control component controls the servo driver, and further controls the actions of the first rotating component and the second rotating component. The first rotating component is specifically a first rotating motor, and the second rotating component is specifically a second rotating motor.

[0047] It is easy to understand that the flat plate can be a circular plate.

[0048] The control component is specifically an existing computing terminal. The control component is separately connected to the light source and the camera. In this way, the control component realizes the adjustment of the brightness of the light source. The light source is specifically an existing light source, and a composite light source is built using the existing light source. The camera is an industrial camera.

[0049] It should be noted that before the control component obtains the image pixel width of the object, it is necessary to determine whether the size of the object is within the depth of field range or outside the depth of field range. The depth of field of the camera is calculated according to the following formula:

[0050]

[0051] Where Z is the camera shooting distance, f is the lens focal length, F is the lens aperture value, and δ is the allowable circle of confusion diameter (when an object is imaged, due to aberration, the imaging light beam cannot converge at a point, and a diffused circular projection is formed on the image plane, which is called the circle of confusion. The maximum diameter that the image can be recognized and accepted is called the allowable circle of confusion diameter).

[0052] Specifically, each shooting has a shooting distance, which is determined according to the lens magnification. After the lens focal length, the lens aperture value, and the allowable circle of confusion diameter are input into the above formula, the shooting distance at each shooting is input into the formula to obtain the corresponding depth of field value. If the depth of field value exceeds the set value, it means that the size of the object is outside the depth of field range. If the depth of field value is less than the set value, it means that the size of the object is within the depth of field range.

[0053] If the size of the object is within the depth of field range, the control component directly obtains the image pixel width of the object;

[0054] If the control component determines that the size of the object is outside the depth of field range, the control component respectively divides the obtained first object image and the nth object image, calculates the focus evaluation parameters for each divided part, calculates the step size according to the calculated focus evaluation parameter values, adjusts the focus position through the step size, and fuses multiple images with different focus positions through a fusion algorithm to obtain clear images in which each part of the first object image and the nth object image is within the depth of field range;

[0055] Among them, the focus evaluation parameter is calculated for each segmented part to obtain the relationship between the focus evaluation parameter D(f) and x or y. The clearer the focus, the larger the value of the focus evaluation parameter. The pixel width L1 (such as L1 = x 1 -x 2 ) within the depth of field range, where the value of L1 is the clear imaging pixel area within the depth of field range. Calculate the step size according to the deflection angle θ of the object at this time. The step size is h = L1·tanθ. Moving the moving deflection platform perpendicular to the Z-axis according to the step size can obtain a clear image.

[0056] Among them, the calculation of the focus evaluation parameter is obtained according to the gray values of the pixel points in the segmented partial images of the first object image and the nth object image. Specifically, the focus evaluation parameter is as follows:

[0057]

[0058] Among them, f(x, y) is the gray value of the pixel point (x, y) in the image;

[0059] Since the image matrix is discrete, the change rate of the image gray level is represented by the difference. For the backward difference of the image in the x direction, the formula is:

[0060] G x (x, y) = G(x, y) - G(x - 1, y)

[0061] G x (x, y) represents the gray value at the image (x, y);

[0062] The control component extracts pixels from the first object image and the nth object image respectively, calculates the gray gradient, locates the pixel position with the largest gray gradient as the boundary line, calculates the entire image column by column along the direction perpendicular to its length, and takes the result average value as the edge pixel position of the first object image and the nth object image. This result average value is used as the image pixel width, and the image obtained after gray conversion is as Figure 4 shown.

[0063] In this embodiment, the calculation model is the relational expression between the height information of the object and the image pixel width of the object. The calculation model obtains the height information of the object through the image pixel width of the object, the lens focal length, the camera shooting distance, the deflection angle of the object, the height of the object in the Z direction, and the included angle between the connection line from the projection point of the object on the calibration plane to the optical center and the camera optical axis. Among them, in the paraxial light of the convex lens, the incident ray and the corresponding and parallel outgoing ray form conjugate rays. The intersection point of the connection line between the incident point and the outgoing point and the principal optical axis is called the focus of the convex lens, and the point located at the center of the lens is called the optical center.

[0064] Among them, the calibration plane is obtained through coordinate transformation based on the internal and external parameters of the camera, and is a position plane obtained in the world coordinate system corresponding one-to-one with the camera pixel coordinates.

[0065] Since the object is now in a yaw state, the entire side cannot be fully on the calibration plane. Therefore, the image value on the nth object image is not the horizontal distance of the actual target value, but the projection of the object on the calibration plane.

[0066] Reference Figure 5 As shown, the projection point of the image value edge on the calibration plane is denoted as point H 1 , and the lower edge projection is denoted as point H 2 . The measured edge is vertically projected onto the calibration plane, denoted as point H' 1 and point H' 2 . The intersection points of the optical axis with the lines connecting point H 1 , point H 2 with the calibration plane are denoted as W 1 and W 2 . The distances from the two intersection points W 1 , W 2 to the rotation center of the motion deflection platform are denoted as L1 and L2, the difference between L1 and L2 is L, and the angles between the connecting lines and the camera optical axis are respectively α 1 , α 2 , H 2 The distance from the yaw table rotation center is denoted as R; the projection of the height information H of the object on the calibration plane is the image pixel width l of the object. It can be seen that the relationship between the height information of the object and the image pixel width of the object can be expressed as:

[0067] H·sinθ = L + (z' + H·cosθ)tanα 1 -z'tanα 2

[0068] In the formula:

[0069]

[0070] In this way, the height information of the object is obtained according to the following formula:

[0071]

[0072] Among them, z' is the height of the object in the Z direction;

[0073] The measurement system provided in this embodiment only requires one camera to capture the object image. The motion yaw platform drives the object to rotate, and multi-angle image acquisition data is obtained through the motion yaw platform. In this way, the two work together, and the control component calculates the gradient of the pixel points of the object image to obtain the image pixel width of the object. The calibration method is simple, and the image pixel width of the object is converted into the height information of the object by constructing a calculation model, which can give full play to the advantages of the monocular system.

[0074] Embodiment 2

[0075] This embodiment provides a micron-level height measurement method, including the following:

[0076] The motion yaw platform supports the object;

[0077] The light source irradiates the object surface, is reflected into the camera lens, and the camera captures the first object image and transmits it to the control component;

[0078] After the motion deflection platform drives the object to rotate by a set angle, the camera captures the nth object image and transmits it to the control component;

[0079] The control component calculates the gradient of the pixel points of the two object images to obtain the image pixel width of the object. A calculation model is built in the control component, and the control component converts the image pixel width of the object into the height information of the object through the calculation model.

[0080] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A micrometer-level height measurement system, characterized in that: include: A motion deflection platform, where an object is placed on the motion deflection platform and the object is driven to rotate by the motion deflection platform; A light source, which is directed toward an object to shine light; Camera, a camera has a lens; The control component is separately connected with the light source and the camera. The light source irradiates the surface of the object and is reflected into the lens of the camera. The camera takes the first object image and transmits it to the control component. The motion deflection platform drives the object to rotate by a set angle each time. The camera takes the nth object image and transmits it to the control component, where n is greater than or equal to 2. The control component calculates the gradient of the pixel points of the first object image and the nth object image to obtain the image pixel width of the object. A calculation model is constructed in the control component. The calculation model obtains the height information of the object through the image pixel width of the object, the focal length of the lens, the shooting distance of the camera, the yaw angle of the object, the height of the object in the Z direction, and the angle between the line connecting the projection point of the object on the calibration plane to the optical center and the optical axis of the camera. The control component converts the image pixel width of the object into the height information of the object through the calculation model.

2. A micrometer-level height measurement system according to claim 1, characterized in that: Before obtaining the image pixel width of the object, the control component needs to determine whether the size of the object is within the depth of field range or outside the depth of field range. If the size of the object is within the depth of field range, the control component directly obtains the image pixel width of the object.

3. A micron-level height measurement system according to claim 2, characterized in that: If the control component determines that the size of the object is outside the depth of field, the control component segments the first object image and the nth object image respectively, calculates the focus evaluation parameters for each segmented part, calculates the step length according to the calculated focus evaluation parameter value, adjusts the focus position according to the step length, and fuses multiple images with different focus positions through a fusion algorithm to obtain clear images in which each part of the first object image and the nth object image is within the depth of field.

4. A micron-level height measurement system according to claim 3, characterized in that: The focus evaluation parameter is calculated by obtaining the grayscale value of the pixel in the segmented partial image of the first object image or the nth object image.

5. The micrometer-level height measurement system according to claim 1, characterized in that: The control component extracts pixels from the first object image and the nth object image respectively, calculates the grayscale gradient, locates the pixel position with the largest grayscale gradient as the boundary line, calculates the entire image column by column along a direction perpendicular to its length, and takes the average value of the results as the edge pixel position of the first object image and the nth object image, and the average value of the results is used as the image pixel width.

6. The micrometer-level height measurement system according to claim 1, characterized in that: The projection point of the object on the calibration plane is the projection point of the first point and the second point in the nth object image on the calibration plane, and the position of the second point in the nth object image is lower than the position of the first point.

7. A micron-level height measurement system according to claim 6, characterized in that: The height of the object in the Z direction is acquired according to the distance between the second point in the nth object image and the rotation center of the motion deflection platform and the deflection angle of the object.

8. The micrometer-level height measurement system according to claim 1, characterized in that: The motion deflection platform comprises a base, a first rotating component is arranged on the base, a second rotating component is arranged on the movable end of the first rotating component, and a flat plate is arranged on the second rotating component, and the flat plate supports the object; The first rotating component and the second rotating component are respectively connected to the control assembly.

9. A micrometer-level height measurement method, characterized in that: A micrometer-level height measurement system according to any one of claims 1 to 8, comprising the following contents: The moving yaw platform supports the object; The light source irradiates the surface of the object and is reflected into the lens of the camera, and the camera captures the image of the first object and transmits it to the control component; After the motion deflection platform drives the object to rotate by a set angle, the camera takes an image of the nth object and transmits it to the control component; The control component calculates the gradient of the pixels of the two object images to obtain the pixel width of the object image. A calculation model is constructed in the control component, and the control component converts the pixel width of the object image into the height information of the object through the calculation model.

Images