Calibration plate and calibration compensation method

Abstract

The present application provides a kind of calibration plate and calibration compensation method, the calibration plate includes at least two groups of calibration patterns, including first group calibration pattern and second group calibration pattern, the first group calibration pattern and the second group calibration pattern are mutually overlapped and different;Wherein, the first group calibration pattern includes multiple first calibration points, the second group calibration pattern includes multiple second calibration points, each first calibration point and each second calibration point one-to-one and mutually coincide.This application, when the camera lens of optical equipment is compensated, the shooting image is compensated after cross comparison using the two groups of patterns and the two groups of calibration points corresponding to the two groups of patterns, which can improve the accuracy of calibration and correction.

Description

Technical Field

[0001] This invention relates to the field of calibration technology, and in particular to a calibration plate and a calibration compensation method. Background Technology

[0002] Current intraoral scanners (IOS) typically use a probe inserted into the oral cavity to scan targets within the cavity. Specifically, multiple feature test patterns are projected onto the target object, and then a camera takes a picture to obtain an image. This image is then decoded to create a 3D model. However, due to the limitations of the optical components in the camera lens of the intraoral scanner, optical distortion often occurs during the process of projecting markings and capturing images containing those markings. Common optical distortions include barrel distortion (such as...). Figure 1A (as shown) and pincushion distortion (as shown) Figure 1B (As shown).

[0003] In daily life, cameras are often used to capture images. In order to compensate for the optical distortion of the camera lens, a calibration target with a known pattern / size is usually used to calculate distortion and perform software compensation. In applications such as machine vision, image measurement, photogrammetry, and 3D reconstruction, a geometric model of camera imaging needs to be established to correct lens distortion, determine the conversion relationship between physical dimensions and pixels, and determine the relationship between the 3D geometric position of a point on the surface of a spatial object and its corresponding point in the image. Among them, the known pattern includes: (1) a black and white checkerboard, which is used to take the corner points at the junction of black and white as feature points, such as Figure 2A As shown; (2) Circular point array, when used, the center of the circular points is used as the feature point, such as Figure 2B As shown; (3) Line checkerboard pattern, when using it, the intersection of the horizontal and vertical lines is used as the feature point, such as Figure 2C As shown, during distortion compensation calculation, images of the calibration board are captured by a camera at different distances, rotation angles, and tilt angles. The final correction compensation value is obtained through algorithm software.

[0004] However, traditional calibration plates vary in size from A4 to full-size newspapers and are suitable for optical distortion compensation of traditional camera lenses. They are not suitable for small-sized precision optical systems such as dental scanners. The main reason is that the calibration plate image captured by the camera lens of the dental scanner is no longer ideal under different distances, rotation angles, and tilt angles. This results in deviations in the feature points obtained from the calibration plate image, making accurate compensation impossible.

[0005] Therefore, a new calibration plate and calibration compensation method are needed to adapt to optical distortion compensation in small-sized precision optical systems such as dental scanners. Summary of the Invention

[0006] The purpose of this invention is to provide a calibration plate and a calibration compensation method to improve the accuracy of optical distortion compensation in optical equipment.

[0007] The technical solution of the present invention provides a calibration plate, the calibration plate including at least two sets of calibration patterns, the at least two sets of calibration patterns including a first set of calibration patterns and a second set of calibration patterns, the first set of calibration patterns and the second set of calibration patterns overlapping each other and being different; wherein, the first set of calibration patterns includes a plurality of first calibration points, the second set of calibration patterns includes a plurality of second calibration points, each first calibration point and each second calibration point correspond one-to-one and coincide with each other.

[0008] As an optional technical solution, the long side and short side of the calibration plate are both less than or equal to 5cm.

[0009] As an optional technical solution, the first set of calibration patterns includes multiple first patterns, and the second set of calibration patterns includes multiple second patterns, wherein each first pattern and each second pattern has a different shape and / or color.

[0010] As an optional technical solution, the color of each first pattern is black and the color of each second pattern is white; or, the color of each first pattern is black and the color of each second pattern is green.

[0011] As an optional technical solution, the plurality of first patterns correspond to the plurality of first calibration points, and the plurality of second patterns correspond to the plurality of second calibration points; wherein, the plurality of first patterns and the plurality of second patterns overlap, such that the plurality of first calibration points and the plurality of second calibration points coincide with each other.

[0012] As an optional technical solution, the first set of calibration patterns is a star array and the second set of calibration patterns is a circular array; or, the first set of calibration patterns is multiple straight lines and the second set of calibration patterns is a circular array; or, the first set of calibration patterns is a cross array and the second set of calibration patterns is a circular array; or, the first set of calibration patterns is a fan-shaped array and the second set of calibration patterns is a black and white checkerboard pattern.

[0013] The technical solution of the present invention also provides a calibration compensation method, the calibration compensation method comprising:

[0014] Step A: Provide the calibration board as described above and the optical equipment including a camera lens;

[0015] Step B: Use the camera lens to photograph the calibration board to obtain a photographed image;

[0016] Step C: Divide the captured image into N image regions, where N is an integer greater than 1. Each set of calibration patterns contains at least one calibration point in each image region. Obtain the compensation value of the calibration point of each set of calibration patterns in each image region.

[0017] Step D: Determine the compensation value for each image region by summing the product of the compensation value of the calibration points of each set of calibration patterns and the corresponding weighted ratio allocation coefficient, plus a preset compensation value; and

[0018] Step E: Compensate each image region according to the compensation value of each image region.

[0019] As an optional technical solution, the at least two sets of calibration patterns are a first set of calibration patterns and a second set of calibration patterns. In step C, each image region includes at least one first calibration point and at least one second calibration point, and a first compensation value A of the at least one first calibration point in each image region is obtained. n and the second compensation value B of the at least one second calibration point n In step D, according to the weighted formula: Z n =(u n ×A n )+(v n ×B n ) +w n 1≤n≤N, calculate the compensation value Z for each image region. n u n Assign a weighting factor, v, to the first calibration point within each image region. n Assign a weighting factor, w, to the second calibration point within each image region. n The preset compensation value for each image region.

[0020] As an optional technical solution, the N image regions include a first image region, which includes at least one first calibration point and at least one second calibration point; according to the weighting formula: Z1=(u1×A1)+(v1×B1)+w1, the first compensation value Z1 of the first image region is calculated, where u1 is the weighting ratio allocation coefficient of the first calibration point in the first image region, v1 is the weighting ratio allocation coefficient of the second calibration point in the first image region, and w1 is the preset compensation value in the first image region.

[0021] As an optional technical solution, the N image regions include a second image region, which includes at least one first calibration point and at least one second calibration point. A second compensation value Z2 for the second image region is calculated according to the weighting formula: Z2=(u2×A2)+(v2×B2)+w2, where u2 is the weighting ratio allocation coefficient of the first calibration point in the second image region, v2 is the weighting ratio allocation coefficient of the second calibration point in the second image region, and w2 is a preset compensation value in the second image region. The weighting ratio allocation coefficients of the first calibration point in the first image region and the second calibration point in the second image region are different, and the weighting ratio allocation coefficients of the second calibration point in the first image region and the second calibration point in the second image region are also different.

[0022] As an optional technical solution, the optical device is an oral scanner.

[0023] As an optional technical solution, N can be 9, 12, or 16.

[0024] Compared with existing technologies, this invention provides a calibration plate and its calibration compensation method. The calibration plate has overlapping and dissimilar first and second sets of calibration patterns. Multiple first calibration points corresponding to the first set of calibration patterns and multiple second calibration points corresponding to the second set of calibration patterns coincide. When compensating for images captured by a camera lens of an optical device, the two sets of overlapping and dissimilar patterns and their corresponding calibration points are cross-compared and then compensated. Furthermore, during the compensation process, the captured image is divided into partitions, and the compensation values ​​of the calibration points in different partitions are combined to calculate the compensation value for each partition before compensating each partition, thereby improving the accuracy of image compensation.

[0025] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments, but this is not intended to limit the present invention. Attached Figure Description

[0026] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0027] Figure 1A This is a schematic diagram of the barrel-shaped distortion pattern.

[0028] Figure 1B This is a schematic diagram of the pincushion distortion pattern.

[0029] Figure 2AThis is a schematic diagram of the black and white checkerboard pattern on the existing calibration board.

[0030] Figure 2B This is a schematic diagram of the circular pattern on the existing calibration plate.

[0031] Figure 2C This is a schematic diagram of the checkerboard pattern on the existing calibration board.

[0032] Figure 3 This is a schematic diagram of the calibration plate and its pattern provided in the first embodiment of the present invention.

[0033] Figure 4 This is a schematic diagram showing the calibration plate and its pattern exploded according to the second embodiment of the present invention.

[0034] Figure 5 This is a schematic diagram showing the calibration plate and its pattern exploded according to the third embodiment of the present invention.

[0035] Figure 6 This is a schematic diagram showing the decomposed calibration plate and its pattern provided in the fourth embodiment of the present invention.

[0036] Figure 7 A flowchart of the calibration compensation method is provided for this invention.

[0037] Figure 8 A schematic diagram of image partitioning is provided for this invention. Detailed Implementation

[0038] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments and accompanying drawings. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0039] In the description of this invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0040] The purpose of this invention is to provide a calibration plate and a calibration compensation method. The calibration plate includes at least two sets of different and overlapping calibration patterns. Each set of calibration patterns contains multiple calibration points, and the multiple calibration points in each set of calibration patterns coincide with each other. By using the calibration plate of this invention, which includes at least two sets of calibration patterns, to calculate compensation values ​​for images captured by the camera lens of an optical device, the accuracy of calibration and correction can be improved.

[0041] Please refer to Figure 3 , Figure 3 This is a schematic diagram of the calibration plate and its pattern provided in the first embodiment of the present invention. Figure 3 As shown, in the first embodiment of the present invention, a calibration plate 100 is provided, which includes a first set of calibration patterns 10 and a second set of calibration patterns 20. The first set of calibration patterns 10 and the second set of calibration patterns 20 overlap and are different from each other. The first set of calibration patterns 10 includes a plurality of first calibration points 11, and the second set of calibration patterns 20 includes a plurality of second calibration points 21. Each first calibration point 11 and each second calibration point 21 coincide with each other. The plurality of first calibration points 11 can constitute a first calibration point system, and the plurality of second calibration points 21 can constitute a second calibration point system. In actual operation, the first set of calibration patterns can be formed on the calibration plate first, and then the second set of calibration patterns (or more calibration patterns) can be formed by adding elements such as lines, graphics, and colors, thereby expanding the original single calibration point system into multiple calibration point systems to facilitate subsequent distortion compensation calculations.

[0042] In some embodiments, the calibration plate 100 includes a sheet body 30, and a first set of calibration patterns 10 and a second set of calibration patterns 20 are disposed on the surface of the sheet body 30. The first set of calibration patterns 10 and the second set of calibration patterns 20 are not limited to being formed on the surface of the sheet body 30 by printing or printing.

[0043] Furthermore, in order to enable the calibration plate 100 to be used for deviation compensation in images captured by optical devices with high precision requirements, such as dental scanners, the long side and short side of the thin sheet body 30 are each less than or equal to 5 cm, that is, the long side and short side of the calibration plate 100 are each less than or equal to 5 cm. In this embodiment, the thin sheet body 30 can be square, but it is not limited to this in actual operation.

[0044] In this embodiment, the first set of calibration patterns 10 includes a plurality of first patterns 12, and the second set of calibration patterns 20 includes a plurality of second patterns 22, wherein each first pattern 12 and each second pattern 22 has a different shape and / or color, such that the first set of calibration patterns 10 and the second set of calibration patterns 20 are different.

[0045] In some embodiments, the shape of the first pattern 12 is different from the shape of the second pattern 22, making the first set of calibration patterns 10 and the second set of calibration patterns 20 different; in another embodiment, the shape and color of the first pattern 12 are different from the shape and color of the second pattern 22, making the first set of calibration patterns 10 and the second set of calibration patterns 20 different.

[0046] Furthermore, multiple first patterns 12 correspond to multiple first calibration points 11, and multiple second patterns 22 correspond to multiple second calibration points 21. The multiple first patterns 12 and multiple second patterns 22 overlap, so that the multiple first calibration points 11 and multiple second calibration points 21 coincide with each other.

[0047] In this embodiment, the first pattern 12 is, for example, a cross-shaped star structure, and the first calibration point 11 is the geometric center of the cross-shaped star structure. Multiple first patterns 12 are arranged in an array. The second pattern 22 is, for example, a circular shape, and the second calibration point 21 is the center of the circular shape. Multiple second patterns 22 are arranged in an array. Each first pattern 12 and each second pattern 22 overlaps, and each first calibration point 11 (the geometric center of the cross-shaped star structure) and each second calibration point 21 (the center of the circle) coincide.

[0048] It should be noted that, for ease of explanation, Figure 3 The grayscale values ​​of multiple first calibration points 11 differ from those of other areas in the first pattern 12. In practice, however, multiple first calibration points 11 can be represented using the same grayscale values, shapes, and sizes as other areas in the first pattern 12. Similarly, Figure 3 The grayscale values ​​of multiple second calibration points 21 differ from those of other areas in the second pattern 22. In practice, multiple second calibration points 21 can be represented using the same grayscale values / shapes / sizes as other areas in the second pattern 22. The following embodiments are similar and will not be described again.

[0049] like Figure 3 As shown, in the calibration plate 100, the second pattern 22 overlaps above the first pattern 12, but this is not a limitation. In other embodiments of the present invention, the second pattern 22 may also overlap below the first pattern 12. That is, the present invention does not particularly limit the overlapping order of the first and second patterns, as long as their calibration points overlap.

[0050] like Figure 3 As shown, the first pattern 12 and the second pattern 22 are both black, but this is not a limitation. In other embodiments of the present invention, the colors of the first pattern 12 and the second pattern 22 can also be different. For example, the combination of the colors of the first pattern 12 and the second pattern 22 can be selected from a combination of green and white, or a combination of green and black. By changing the colors of the patterns and using patterns with obvious color differences, the patterns with obvious color differences and their corresponding calibration points are more easily identified in the captured image after being captured by the camera lens of the optical device.

[0051] Please refer to Figure 4 , Figure 4 This is a schematic diagram showing the exploded view of the calibration plate and its pattern provided in the second embodiment of the present invention. Figure 4As shown, the difference between calibration plate 200 and calibration plate 100 provided in the second embodiment of the present invention is only that the first set of calibration patterns 210 in calibration plate 200 and the first set of calibration patterns 10 in calibration plate 100 (e.g., ...) Figure 3 The (shown) are not the same. Furthermore, Figure 4 and Figure 3 The same labels in the code represent the same component structure and have similar functions.

[0052] The calibration plate 200 includes a first set of calibration patterns 210 comprising multiple first patterns 212, which are evenly arranged. Each first pattern 212 is a straight line, and multiple first calibration points 211 are evenly distributed on each first pattern 212. Multiple second patterns 22 are arranged in an array, and the multiple first patterns 212 overlap with the multiple second patterns 22, such that the multiple first calibration points 211 coincide with the multiple second calibration points 21. It should be noted that, for ease of explanation, Figure 4 The dimensions of multiple first calibration points 211 are different from those of other areas in the first drawing 212. In actual operation, multiple first calibration points 211 can be presented with the same size / shape / grayscale value as other areas in the first drawing 212.

[0053] In this embodiment, each first pattern 212 corresponds to a plurality of first calibration points 211, and each second pattern 22 corresponds to a second calibration point 22. Each first pattern 212 and a plurality of second patterns 22 overlap, such that the plurality of first calibration points 211 on each first pattern 212 coincide with the plurality of second calibration points 21 in the plurality of second patterns 22.

[0054] In addition, each first pattern 212 may overlap below a plurality of second patterns 22, but is not limited thereto. Each first pattern 212 may also overlap above a plurality of second patterns 22.

[0055] Please refer to Figure 5 , Figure 5 This is a schematic diagram showing the exploded view of the calibration plate and its pattern provided in the third embodiment of the present invention. Figure 5 As shown, the difference between calibration plate 300 and calibration plate 100 provided in the third embodiment of the present invention is only that the first set of calibration patterns 310 in calibration plate 300 and the first set of calibration patterns 10 in calibration plate 100 (e.g., ...) Figure 3 The (shown) are not the same. Furthermore, Figure 5 and Figure 3 The same labels in the code represent the same component structure and have similar functions.

[0056] The first set of calibration patterns 310 in the calibration plate 300 includes multiple first patterns 312, each first pattern 312 corresponding to each first calibration point 311. Each first pattern 312 is cross-shaped, and each first calibration point 311 is the geometric center of the cross-shaped pattern. The geometric center of the cross-shaped pattern coincides with the second calibration point 21 (center of the circle) of the second pattern 22 (circle).

[0057] like Figure 5 As shown, in this embodiment, each first pattern 312 and each second pattern 22 correspond one-to-one and overlap. In this embodiment, the cross-shaped first pattern 312 can be white, and the circular second pattern 22 can be black. In actual operation, this is not a limitation.

[0058] Please refer to Figure 6 , Figure 6 This is a schematic diagram showing the exploded view of the calibration plate and its pattern provided in the fourth embodiment of the present invention. Figure 6 As shown, the difference between calibration plate 400 and calibration plate 100 provided in the fourth embodiment of the present invention is that the first set of calibration patterns 410 and the second set of calibration patterns 420 in calibration plate 400 and the first set of calibration patterns 10 and the second set of calibration patterns 20 in calibration plate 100 are all different (e.g., Figure 3 (As shown). Furthermore, Figure 6 and Figure 3 The same labels in the code represent the same component structure and have similar functions.

[0059] like Figure 6 As shown, the first set of calibration patterns 410 includes multiple first patterns 412, each first pattern 412 corresponding to a first calibration point 411; the second set of calibration patterns 420 is a black and white checkerboard pattern, with multiple second calibration points 421 located at the intersection of any black square (or any white square) in the black and white checkerboard; wherein, each first calibration point 411 and each second calibration point 421 coincide.

[0060] In this embodiment, after the first set of calibration patterns 410, composed of multiple first patterns 412, and the second set of calibration patterns 420 are overlapped, the white squares in each first pattern 412 and the second set of calibration patterns 420 overlap. Each first pattern 412 is black in color and has the shape of two connected sectors, with the vertices of the two sectors connected to each other. In actual operation, the difference in shape and color can be used to make the first pattern 412 and the black and white checkerboard pattern easier to distinguish.

[0061] The aforementioned calibration plates 100 / 200 / 300 / 400 each contain two sets of distinct and overlapping calibration patterns, with multiple calibration points in each set of patterns coinciding with multiple calibration points in the other set of patterns. In practice, calibration plates may also contain more than two sets of distinct and overlapping calibration patterns, and are not limited to this.

[0062] like Figure 7 As shown, the present invention also provides a calibration compensation method, which includes:

[0063] Step A: Provide any of the above calibration plates and optical devices including a camera lens;

[0064] Step B: Use the camera lens to photograph the calibration board to obtain a photographed image;

[0065] Step C: Divide the above-captured pattern into N image regions, where N is an integer greater than 1; each set of calibration patterns contains at least one calibration point in each image region, and obtain the compensation value of the calibration point of each set of calibration patterns in each image region.

[0066] Step D: Determine the compensation value for each image region by summing the product of the compensation value of the calibration points of each set of calibration patterns and the corresponding weighted ratio allocation coefficient, plus a preset compensation value; and

[0067] Step E: Compensate each image region according to the compensation value of each image region.

[0068] In this invention, the captured image is divided into partitions, and each partition is assigned a weighted ratio coefficient of a different calibration point system. This is combined with correction and compensation to obtain the final calibration point position, thereby improving the accuracy of the optical equipment.

[0069] The following explanation uses an example where the calibration board contains two sets of calibration patterns, namely, a first set of calibration patterns and a second set of calibration patterns. Therefore, in step C, each image region includes at least one first calibration point and at least one second calibration point, and a first compensation value A for at least one first calibration point within each image region is obtained. n and at least one second compensation value B for a second calibration point n , 1≤n≤N.

[0070] In step D, according to the weighted formula: Z n =(u n ×A n )+(v n ×B n )+w n ; Calculate the compensation value Z for each image region n , where u nAssign a weighting factor, v, to the first calibration point within each image region. n Assign a weighting factor, w, to the second calibration point within each image region. n This refers to a preset compensation value for each image region. In practice, for example... Figure 1A The barrel distortion shown and Figure 1B As shown in the pincushion distortion diagram, the degree of distortion varies in different regions of the captured image, resulting in different weighting ratios for each region.

[0071] It should be noted that the weighting formula in this embodiment is calculated based on the calibration plate containing two sets of calibration patterns. In actual operation, the algorithm when the calibration plate contains more than two sets of calibration patterns can be deduced by analogy.

[0072] Please refer to Figure 8 , Figure 8 This diagram illustrates the division of an image captured by a camera lens of an optical device onto a calibration board into N image regions. In this embodiment, the captured image is divided into 9 regions, i.e., N=9. However, in actual operation, this is not a limitation. Users can divide the captured image into different regions according to their actual needs, such as 12, 16, 20, 25, etc.

[0073] like Figure 8 As shown, the captured image is divided into N (N=9 in this embodiment) image regions, and the compensation value for each image region is calculated and compensated separately, which helps to improve the accuracy of the image after compensation.

[0074] Specifically, the N image regions include a first image region N1, which includes at least one first calibration point and at least one second calibration point. The first compensation value Z1 of the first image region is calculated according to the weighting formula: Z1=(u1×A1)+(v1×B1)+w1, where u1 is the weighting ratio allocation coefficient of the first calibration point in the first image region, v1 is the weighting ratio allocation coefficient of the second calibration point in the first image region, and w1 is the preset compensation value in the first image region.

[0075] The N image regions also include a second image region N2, which includes at least one first calibration point and at least one second calibration point. A second compensation value Z2 for the second image region is calculated according to the weighting formula: Z2 = (u2 × A2) + (v2 × B2) + w2, where u2 is the weighting ratio allocation coefficient of the first calibration point in the second image region, v2 is the weighting ratio allocation coefficient of the second calibration point in the second image region, and w2 is a preset compensation value in the second image region. The weighting ratio allocation coefficients of the first calibration point in the first image region and the second calibration point in the second image region are different (i.e., u1 and u2 are different), and the weighting ratio allocation coefficients of the second calibration point in the first image region and the second calibration point in the second image region are also different (i.e., v1 and v2 are different). In one embodiment, for example, u1 is 60%, v1 is 40%, u2 is 55%, and v2 is 45%. These values ​​are merely examples and are not limited to in actual operation.

[0076] Similarly, the N image regions also include the third image region N3, the fourth image region N4, the fifth image region N5, the sixth image region N6, the seventh image region N7, the eighth image region N8, and the ninth image region N9. The compensation values ​​for the third to ninth image regions can be calculated separately according to the weighted formula mentioned above.

[0077] In addition, the weighting ratio allocation coefficients of the first calibration points corresponding to the third to ninth image regions are different; and the weighting ratio allocation coefficients of the second calibration points corresponding to the third to ninth image regions are also different.

[0078] Taking the aforementioned calibration board 100 as an example, a black starburst pattern is superimposed on the circles without affecting the determination of the center of each black circle in the black circular array. Theoretically, the calculated values ​​of the first calibration point system and the second calibration point system are the same when performing distortion compensation calculations. However, in reality, the calculated values ​​of the first calibration point system and the second calibration point system are often different due to the deviations described in the background art. This invention uses the aforementioned weighted formula to calculate the deviation compensation, which can ensure the accuracy of distortion compensation.

[0079] The calibration board of the present invention expands a calibration board with a single calibration point system into a calibration board with multiple calibration point systems by adding simple lines, geometric shapes, colors and other elements, and can use data from multiple calibration point systems for cross-comparison and compensation.

[0080] The above calibration compensation method is particularly suitable for the calibration compensation of images captured by optical devices such as dental scanners when the size of the calibration plate is less than or equal to 5cm×5cm.

[0081] This invention employs a single calibration plate, expanding it with at least two calibration point systems through pattern design. For example, it includes a first calibration point system and a second calibration point system. The first calibration point system contains multiple first calibration points, and the second calibration point system contains multiple second calibration points. The multiple first calibration points and multiple second calibration points correspond one-to-one and overlap with each other. Simultaneously, this invention utilizes the captured image to partition it into multiple image regions. Each image region uses a different weighting ratio allocation coefficient for the calibration points to correct the deviation values ​​of the calibration points within each image region, thereby achieving distortion compensation and improving the accuracy of distortion compensation.

[0082] In summary, this invention provides a calibration plate and a calibration compensation method. The calibration plate has at least one overlapping and distinct first set of calibration patterns and a second set of calibration patterns. Multiple first calibration points corresponding to the first set of calibration patterns and multiple second calibration points corresponding to the second set of calibration patterns coincide. When compensating for images captured by a camera lens of an optical device, compensation is performed by cross-comparing these two overlapping and distinct sets of patterns and their corresponding two sets of calibration points. Furthermore, during the compensation process, the captured image is divided into partitions, and the compensation values ​​of the calibration points in different partitions are combined to calculate the compensation value for each partition before compensation is applied to each partition, thereby improving the accuracy of image compensation.

[0083] The present invention has been described by the above-described embodiments; however, these embodiments are merely examples for implementing the present invention. Furthermore, the technical features involved in the different embodiments of the present invention described above can be combined with each other as long as they do not conflict with each other. It must be noted that the present invention may have other various embodiments, and those skilled in the art can make various corresponding changes and modifications based on the present invention without departing from its spirit and essence; however, all such corresponding changes and modifications should fall within the protection scope of the appended claims.

Claims

1. A calibration plate, characterized in that The calibration plate includes at least two sets of calibration patterns, which include a first set of calibration patterns and a second set of calibration patterns. The first set of calibration patterns and the second set of calibration patterns overlap each other and are different. The first set of calibration patterns includes multiple first calibration points, and the second set of calibration patterns includes multiple second calibration points. Each first calibration point and each second calibration point correspond to each other and overlap with each other. In use, the calibration board is photographed to obtain a captured image; the captured image is divided into N image regions, where N is an integer greater than 1, and each set of calibration patterns contains at least one calibration point in each image region; the compensation value of the calibration point of each set of calibration patterns in each image region is obtained; the compensation value of each image region is determined by multiplying the compensation value of the calibration point of each set of calibration patterns with the corresponding weighted ratio allocation coefficient and adding the sum of preset compensation values; each image region is compensated according to the compensation value of each image region.

2. The calibration board of claim 1, wherein, The long side and short side of the calibration plate are both less than or equal to 5 cm.

3. The calibration board of claim 1, wherein, The first set of calibration patterns includes multiple first patterns, and the second set of calibration patterns includes multiple second patterns, wherein each first pattern and each second pattern has a different shape and / or color.

4. The calibration plate according to claim 3, characterized in that, The first set of calibration patterns is a starburst array, and the second set of calibration patterns is a circular array; or... The first set of calibration patterns consists of multiple straight lines, and the second set of calibration patterns consists of a circular array; or... The first set of calibration patterns is a cross array, and the second set of calibration patterns is a circular array; or... The first set of calibration patterns is a fan-shaped array, and the second set of calibration patterns is a black and white checkerboard pattern.

5. A calibration compensation method, characterized in that, The calibration compensation method includes: Step A: Provide a calibration plate according to any one of claims 1-4 and an optical device including a camera lens; Step B: Use the camera lens to photograph the calibration board to obtain a photographed image; Step C: Divide the captured image into N image regions, where N is an integer greater than 1. Each set of calibration patterns contains at least one calibration point in each image region. Obtain the compensation value of the calibration point of each set of calibration patterns in each image region. Step D: Determine the compensation value for each image region by summing the product of the compensation value of the calibration points of each set of calibration patterns and the corresponding weighted ratio allocation coefficient, plus a preset compensation value; and Step E: Compensate each image region according to the compensation value of each image region.

6. The calibration compensation method according to claim 5, characterized in that, The at least two sets of calibration patterns are the first set of calibration patterns and the second set of calibration patterns. In step C, each image region comprises at least one first calibration point and at least one second calibration point, a first compensation value A of the at least one first calibration point in each image region is obtained n and a second compensation value B of the at least one second calibration point n ​ In step D, the compensation value Z n of each image region is calculated according to the weighted formula: Z n = (u n × A n ) + (v n × B n ) + w n , 1≤n≤N, wherein u n is the weighted proportional distribution coefficient of the first calibration point in each image region, v n is the weighted proportional distribution coefficient of the second calibration point in each image region, and w n is the preset compensation value in each image region.

7. The calibration compensation method according to claim 6, characterized in that, The N image regions include a first image region, which includes at least one first calibration point and at least one second calibration point; In step D, the first compensation value Z1 of the first image region is calculated according to the weighting formula: Z1=(u1×A1)+(v1×B1)+w1, where u1 is the weighting ratio allocation coefficient of the first calibration point in the first image region, v1 is the weighting ratio allocation coefficient of the second calibration point in the first image region, and w1 is the preset compensation value in the first image region.

8. The calibration compensation method according to claim 7, characterized in that, The N image regions include a second image region, and the second image region includes at least one first calibration point and at least one second calibration point; According to the weighting formula: Z2=(u2×A2)+(v2×B2)+w2, the second compensation value Z2 of the second image region is calculated, u2 is the weighting ratio allocation coefficient of the first calibration point in the second image region, v2 is the weighting ratio allocation coefficient of the second calibration point in the second image region, and w2 is the preset compensation value in the second image region; where u1 and u2 are different, and v1 and v2 are different.

9. The calibration compensation method according to claim 5, characterized in that, N is 9, 12, or 16.

10. The calibration compensation method according to claim 5, characterized in that, The optical device is an oral scanner.

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