Micrometer-level height measurement system and measurement method

Abstract

The present invention discloses a micron-level height measurement system and a measurement method, which solve the problem of system complexity of the micron-level height measurement system in the prior art. The system has a simple structure and can achieve the beneficial effect of object height measurement. The specific scheme is as follows: A micron-level height measurement system includes a motion deflection platform, an object is placed on the motion deflection platform and the motion deflection platform drives the object to rotate; a light source is directed toward the object to irradiate light; a control component is separately connected to the light source and a camera, the light source irradiates the surface of the object and is reflected into the lens of the camera, and the camera captures the first object image and transmits it to the control component. After the motion deflection platform drives the object to rotate a set angle, the camera captures the nth object image and transmits it to the control component. The control component performs pixel gradient calculation on the two object images to obtain the image pixel width of the object. The control component converts the image pixel width of the object into the height information of the object through a calculation model.

Description

Technical Field

[0001] The present invention relates to the field of height measurement, and in particular to a micron-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 industry, the high integration and miniaturization of a large number of components and equipment require fast and accurate measurement. For the Z direction of small-scale three-dimensional topography, that is, highly accurate measurement, it 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 very 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 utilizes multiple optical devices based on the multi-viewpoint principle to acquire sequential images containing three-dimensional spatial information. However, the reconstruction accuracy and speed of these traditional methods have been significant computational challenges. Second-generation deep learning methods also face challenges with insufficient learning data and model migration. In 3D modeling and autonomous driving, the data required for target reconstruction can be supplemented by increasing the number of cameras to acquire multiple sequential images. However, in the field of microscopic visual measurement, the accuracy of binocular vision systems remains low, and large raw databases are difficult to obtain. At this scale, blindly increasing the number of devices and deep learning methods is not advisable. Summary of the Invention

[0005] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a micron-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 micron-level height measurement system, comprising:

[0008] A motion deflection platform, on which an object is placed and rotated by the motion deflection platform;

[0009] A light source, which shines light toward an object;

[0010] Camera, a camera has a lens;

[0011] The control component is separately connected to 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 image of the object and transmits it to the control component. After the motion deflection platform drives the object to rotate at a set angle, the camera takes the nth image of the object and transmits it to the control component. 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 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.

[0012] In a micron-level height measurement system as described above, the control component needs to determine whether the size of the object is within or outside the depth of field range before obtaining the image pixel width of the object. 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] In the 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, the control component segments the acquired first object image and nth object image respectively, calculates 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.

[0014] In the micron-level height measurement system as described above, the focus evaluation parameter is calculated based on the grayscale values ​​of pixels in the segmented partial image of the first object image or the nth object image.

[0015] In the micron-level height measurement system described above, 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.

[0016] In the micron-level height measurement system as described above, 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.

[0017] In the micron-level height measurement system described above, the height of the object in the Z direction is acquired based on 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.

[0018] In the micron-level height measurement system described above, the motion deflection platform includes a base, a first rotating component is provided on the base, a second rotating component is provided at the movable end of the first rotating component, and a flat plate is provided 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 assembly.

[0020] In a second aspect, the present invention further provides a micrometer-level height measurement method, comprising the following contents:

[0021] The moving yaw platform supports the object;

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

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

[0024] 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.

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

[0026] 1) The measurement system provided by the present invention only requires one camera to capture an image of an object. 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 object's image pixel width. The calibration method is simple, and the object's image pixel width is converted into the object's height information by constructing a calculation model. The overall structure is simple, and only one camera is used, which can give full play to the advantages of the monocular system and has a small system error.

[0027] 2) In the present invention, before obtaining the image pixel width of the object, it is necessary to determine 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, and after segmenting each part of the image, calculate the focus evaluation parameters and move the step size to obtain multiple images of each part within the depth of field, and fuse them to obtain a clearly focused 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 acquire the object image, and it is beneficial for the control component to extract the pixels of the object image. Then, the image grayscale gradient method is used to detect the edge pixel position of the image, and the entire image is calculated column by column along the direction perpendicular to its length to determine the image pixel width.

[0029] 4) The present invention selects the first point and the second point in the image of the nth object, obtains the projection points of these two points on the calibration plane, and obtains the yaw angle of the object, so as to obtain the height of the object in the Z direction. It can also obtain 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, and combine the image pixel width of the object to obtain a calculation model. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The accompanying drawings, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

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

[0032] Figure 2 1 is a two-dimensional schematic diagram of imaging of a micron-level height measurement system according to one or more embodiments of the present invention.

[0033] Figure 3 Schematic diagram of an 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 Schematic diagram of an image after grayscale transformation in a micron-level height measurement system according to one or more embodiments of the present invention.

[0035] Figure 5 It is a schematic diagram of establishing a computational 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 parts are exaggerated to show the positions of various parts, and the schematic diagram is for reference only. DETAILED DESCRIPTION

[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 skilled in the art 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 otherwise clearly indicated in the present invention, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "include" and / or "comprising" are used in this specification, they indicate the presence of features, steps, operations, devices, components and / or their combinations;

[0039] As introduced in the background art, the prior art micron-level height measurement system has the problem of system complexity. In order to solve the above technical problem, the present invention proposes a micron-level height measurement system.

[0040] Example 1

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

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

[0043] a light source, which is directed toward the object to illuminate the light and thereby magnify the microscopic scene;

[0044] Camera, a camera has a lens;

[0045] Control component, the control component is connected to the light source and camera separately, the light source is irradiated to the surface of the object, reference Figure 3 As shown, the reflection into the camera lens is captured by the camera and the first object image is transmitted to the control component. After the motion deflection platform drives the object to rotate by a set angle each time, an object image is captured. In this way, the camera captures the nth object image and transmits it to the control component. The nth object image refers to the image captured for the nth time, where n is a natural number and n is greater than or equal to 2. 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 constructed 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 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.

[0046] In this embodiment, the motion yaw platform includes a base, a first rotating component is provided on the base, a second rotating component is provided at the movable end of the first rotating component, and a flat plate is provided on the second rotating component, which supports the 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, and the control component controls the servo driver, thereby controlling the movement 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, and the control component is separately connected to the light source and the camera, so that the control component can adjust 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 obtaining the pixel width of the object's image, the control component needs to determine whether the object's size is within 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 focal length of the lens, F is the lens aperture value, and δ is the diameter of the permissible circle of confusion (when an object is imaged, due to aberrations, its imaging light beam cannot converge at one point, forming a diffuse circular projection on the image plane, which is called the circle of confusion. The maximum diameter at which the image can be recognized and accepted is called the permissible circle of confusion).

[0052] Specifically, each shooting has a shooting distance, which is determined according to the lens magnification. After the lens focal length, lens aperture value and allowable confusion circle diameter are input into the above formula, the shooting distance for 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, 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 segments the acquired first object image and the nth object image respectively, calculates focus evaluation parameters for each segmented portion, calculates a 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 using a fusion algorithm to obtain a clear image in which each portion of the first object image and the nth object image is within the depth of field range;

[0055] 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 focus evaluation parameter value. The pixel width L1 (such as L1 = x1-x2) where the focus evaluation parameter value is higher than the preset value within the depth of field is intercepted. The L1 value is the clear imaging pixel area within the depth of field. The step length is calculated according to the yaw angle θ of the object at this time. The step length is h = L1·tanθ. The moving yaw platform is moved perpendicular to the Z axis according to the step length to obtain a clear image.

[0056] The focus evaluation parameters are calculated based on the grayscale values ​​of the pixels in the segmented partial images of the first object image and the nth object image. Specifically, the focus evaluation parameters are as follows:

[0057]

[0058] Where f(x,y) is the grayscale value of the pixel (x,y) in the image;

[0059] Since the image matrix is ​​discrete, the rate of change of the image grayscale is expressed by the difference. The formula for the backward difference of the image in the x direction is:

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

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

[0062] 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 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. The average value of the results is used as the image pixel width, and the image obtained after grayscale conversion is as follows Figure 4 shown.

[0063] In this embodiment, the calculation model is a relationship 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 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. Among them, in the paraxial light of the convex lens, the incident ray and the corresponding and parallel outgoing ray constitute conjugate light, and the intersection of the line connecting the incident point and the outgoing point with the main optical axis is called the focus of the convex lens, and the point at the center of the lens is called the optical center.

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

[0065] Since the object is now in a yaw state, not all sides are 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] refer to Figure 5 As shown, the projection point of the image value edge on the calibration plane is recorded as point H1, and the projection of the lower edge is recorded as point H2. The measured edge is vertically projected on the calibration plane and recorded as points H′1 and H′2 respectively. The intersection points of the optical axis, points H1, and H2 with the calibration plane are recorded as W1 and W2. The distances between the two intersection points W1 and W2 and the rotation center of the motion deflection platform are recorded as L1 and L2, the difference between L1 and L2 is L, the angles between the connecting line and the optical axis of the camera are α1 and α2 respectively, and the distance between H2 and the rotation center of the deflection platform is recorded 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)tanα1-z′tanα2

[0068] Where:

[0069]

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

[0071]

[0072] Where 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 an image of an object. 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 in the object image to obtain the object's image pixel width. The calibration method is simple. By constructing a calculation model to convert the object's image pixel width into the object's height information, the advantages of the monocular system can be fully utilized.

[0074] Example 2

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

[0076] The moving yaw platform supports the object;

[0077] The light source is irradiated onto the surface of the object and reflected into the lens of the camera, and the camera captures the image of the first object 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 image of the nth object 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 foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A micron-level height measurement system, characterized in that: include: A motion deflection platform, on which an object is placed and rotated by the motion deflection platform; A light source, which shines light toward an object; Camera, a camera has a lens; A control component is separately connected to a light source and a camera. The light source irradiates the surface of an object and is reflected into the lens of the camera. The camera captures an image of the first object and transmits it to the control component. The motion deflection platform drives the object to rotate by a set angle each time, and the camera captures an image of the nth object and transmits it to the control component, where n is greater than or equal to 2. The control component calculates the gradient of the pixels 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. 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; If the control component determines that the size of the object is outside the depth of field, the control component segments the acquired first object image and 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.

2. A micron-level height measurement system according to claim 1, characterized in that: The focus evaluation parameter is calculated based on the grayscale values ​​of pixels in the segmented partial image of the first object image or the nth object image.

3. The micron-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.

4. The micron-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.

5. The micron-level height measurement system according to claim 4, characterized in that: The height of the object in the Z direction is acquired based on 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.

6. The micron-level height measurement system according to claim 1, characterized in that: The motion deflection platform includes a base, a first rotating component is provided on the base, a second rotating component is provided at the movable end of the first rotating component, and a flat plate is provided 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.

7. A micron-level height measurement method, characterized in that: A micron-level height measurement system according to any one of claims 1 to 6, comprising the following contents: The moving yaw platform supports the object; The light source is irradiated onto the surface of the object and 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 captures the image of the nth object and transmits it to the control component; 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.

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