Calibration method and camera device calibrated by adopting calibration method

Abstract

The invention discloses a calibration method and a camera device calibrated by adopting the calibration method. The method comprises: controlling a liquid crystal unit to display a first calibration image; acquiring an image coordinate of a first calibration image displayed by the liquid crystal unit as a first image coordinate; controlling the image acquisition unit to shoot a first calibration image displayed by the liquid crystal unit as a second calibration image; acquiring an image coordinate of a second calibration image as a second image coordinate; and determining a transformation matrix based on the first image coordinate and the second image coordinate, and calibrating the liquid crystal unit and the image acquisition unit. The calibration method is simple to operate, high in calibration precision and convenient to apply.

Description

Technical Field

[0001] The present invention relates to image sensor and display device calibration technology, and in particular to a calibration method and a camera device calibrated by using the calibration method. Background Art

[0002] High-reflective 3D imaging is an advanced technology for detecting, identifying and analyzing highly reflective surfaces or materials. Such surfaces include metals, glass, liquids, etc., and are often used in industrial inspection, medical imaging and scientific research.

[0003] Since highly reflective surfaces produce strong light reflections, traditional imaging technologies often face many challenges when dealing with these materials, such as light spots, ghosting, and contrast reduction. In modern imaging systems, CMOS sensors and LCD screens are key components for image acquisition and display. As the core of image acquisition, the performance of CMOS sensors directly affects the clarity and accuracy of images. The LCD screen can assist the imaging system in obtaining clear images. In the structured light 3D reconstruction system, an LCD screen is introduced in front of the CMOS image sensor and the camera lens. The intensity of the incident light is controlled by adjusting the brightness of the liquid crystal layer, thereby regulating the brightness of each area in the image acquired by the CMOS image sensor. Due to the interaction between the CMOS image sensor and the LCD screen, how to accurately calibrate the position of the CMOS sensor pixels with the LCD screen pixels to achieve pixel-level control of the brightness of the high-exposure area of ​​the image has become an important research topic.

[0004] CMOS sensors convert light signals into electrical signals through the photoelectric effect, and convert electrical signals into digital image data. Its core component is the photodiode array, which generates charges by sensing light intensity and ultimately generates images. The performance of CMOS sensors is mainly affected by factors such as pixel density, photosensitivity, noise level, and dynamic range. LCD screens adjust the transmittance of light through the optical properties of liquid crystal molecules to display images. The pixels of the LCD screen are composed of liquid crystal molecules and backlight sources, and the brightness and color of each pixel can be controlled by electrical signals. The display effect of the LCD screen is affected by factors such as resolution, brightness uniformity, and color accuracy. In practical applications, in order to achieve pixel-level control of incident light, the correspondence between CMOS pixels and LCD pixels must be obtained. A common method in the related art is to display a circle on an LCD screen and extract the center point. Since the points on the LCD screen are known, the corresponding homography matrix can be calculated through the coordinate points of the center point and the pixel points on the LCD screen. This method has certain requirements on the screen resolution. For screens with lower resolution, it is impossible to display enough complete circles, and the extracted center coordinates have large errors. Another method is to display a checkerboard on the screen and extract the corner points. The corresponding homography matrix is ​​calculated through the checkerboard corner points and the pixel points on the LCD screen. When the checkerboard is displayed on the screen, due to the errors caused by screen refraction and diffraction, the edges of the checkerboard in the image are blurred, and the extracted corner coordinates will have large errors.

[0005] These problems in traditional calibration methods limit their effectiveness and stability in practical applications. Therefore, developing a new calibration method that can overcome these problems is of great significance for improving the accuracy and reliability of image acquisition and display systems. To this end, this paper proposes a universal matching algorithm that can achieve accurate matching even when the screen quality is low, and subsequent changes in application scenarios will not affect the corresponding relationship of pixels. Summary of the invention

[0006] The present invention provides a calibration method and a camera device calibrated by the calibration method. The calibration method can improve the calibration accuracy.

[0007] In one aspect, a calibration method is provided, comprising: Controlling the liquid crystal unit to display a first calibration image; Acquire image coordinates of a first calibration image displayed by the liquid crystal unit as first image coordinates; Controlling the image acquisition unit to capture the first calibration image displayed by the liquid crystal unit as the second calibration image; Obtaining image coordinates of the second calibration image as second image coordinates; A transformation matrix is ​​determined based on the first image coordinates and the second image coordinates, and the liquid crystal unit and the image acquisition unit are calibrated.

[0008] Optionally, controlling the liquid crystal unit to display the first calibration image includes: The transmittance at each pixel position in the liquid crystal unit is adjusted, and a checkerboard image is displayed on the liquid crystal unit as a first calibration image, wherein the first calibration image includes a plurality of white areas and a plurality of black areas.

[0009] Optionally, obtaining image coordinates of a first calibration image displayed by the liquid crystal unit as first image coordinates includes: The coordinate average of the pixel coordinates in the black area is obtained as the first image coordinate.

[0010] Optionally, obtaining image coordinates of the second calibration image as second image coordinates includes: The second calibration image is subjected to an inverse binary operation to form a third calibration image; Screening the white areas in the second calibration image according to the positions and quantities of the black areas in the first calibration image; The average coordinates of the pixel coordinates of the white area in the third calibration image are calculated as the second image coordinates.

[0011] Optionally, determining a transformation matrix based on the first image coordinates and the second image coordinates includes: Using a clustering algorithm to sort the acquired plurality of the second image coordinates, and to make the second image coordinates correspond to the first image coordinates one by one; Based on the formula Find the transformation matrix ,in represents the first image coordinates, Represents the second image coordinates.

[0012] In another aspect, a camera device is provided, comprising: Optical lens; An image acquisition unit, used to acquire an image incident to the optical lens; A liquid crystal unit, used to adjust the brightness of the image acquired by the image acquisition unit, wherein the optical lens, the liquid crystal unit and the image acquisition unit are arranged on the incident light path; A control unit is connected to the image acquisition unit and the liquid crystal unit. The control unit controls the brightness at each pixel position on the liquid crystal unit through a transformation matrix to achieve pixel-level regulation of the brightness of the image acquired by the image acquisition unit. The transformation matrix is ​​obtained by the calibration method according to any one of claims 1 to 5.

[0013] Optionally, the control unit controls the liquid crystal unit to obtain the image acquired by the image acquisition unit through the following formula: Compensate the brightness of the image:

[0014]

[0015] Among them, the pixel coordinates in the liquid crystal unit are ( , , 1), the coordinates of the image acquired by the image acquisition unit are ( , , 1), Represents the elements in the transformation matrix, where The value range is 1~3. The value range is 1~3.

[0016] Optionally, the liquid crystal unit is arranged between the optical lens and the image acquisition unit.

[0017] Optionally, the liquid crystal unit comprises: A first polarizer and a second polarizer, and a liquid crystal layer disposed between the first polarizer and the second polarizer, wherein the liquid crystal layer is connected to the control unit.

[0018] Optionally, the first polarizer and the second polarizer are polarizers.

[0019] The technical solution provided by the embodiments of the present disclosure has the following beneficial effects: In the embodiment of the present disclosure, a calibration method is provided. The steps of the calibration method are relatively simple and easy to apply. High-precision calibration of the image acquisition unit and the liquid crystal unit can be completed through a computer program. In addition, the calibration method has no requirements on the resolution of the liquid crystal unit, and high-precision calibration can also be achieved for liquid crystal units with lower resolutions. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0021] Figure 1 A method flow chart of a calibration method provided by an embodiment of the present disclosure; Figure 2 A schematic diagram of a first calibration image provided by an embodiment of the present disclosure; Figure 3A schematic diagram of a second calibration image provided by an embodiment of the present disclosure; Figure 4 A schematic diagram of a third calibration image provided by an embodiment of the present disclosure; Figure 5 A schematic diagram of the structure of a camera device provided in an embodiment of the present disclosure; Figure 6 A schematic diagram of the structure of a liquid crystal unit provided in an embodiment of the present disclosure; Figure 7 A schematic diagram of the structure of a three-dimensional reconstruction system provided in an embodiment of the present disclosure.

[0022] The reference numerals are as follows: 1: camera device; 11: optical lens; 12: image acquisition unit; 13: liquid crystal unit; 131: first polarizer; 132: second polarizer; 133: liquid crystal layer; 134: control line; 2: Image emission device; 3: Object being measured. DETAILED DESCRIPTION

[0023] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the drawings of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0024] Figure 1 A method flow chart of a calibration method provided by an embodiment of the present disclosure. Figure 1 The method steps include: S101 , controlling a liquid crystal unit to display a first calibration image.

[0025] In one example, step S101 includes: The transmittance at each pixel position in the liquid crystal unit is adjusted, and a checkerboard image is displayed on the liquid crystal unit as a first calibration image, wherein the first calibration image includes a plurality of white areas and a plurality of black areas.

[0026] In the disclosed embodiment, the first calibration image adopts a checkerboard image, in which black areas and white areas are alternately distributed, and when the subsequent image acquisition unit captures the first calibration image, it is more conducive to the clarity of the captured second calibration image. In addition, the use of the checkerboard image is conducive to determining the image coordinates of the first calibration image and the second calibration image.

[0027] It is worth noting that before calibration, a light source needs to be set on the incident light path of the camera device, such as a light source board, to provide incident light for the camera device. The voltage of the light source board can be 24V and the current can be 1A. After the light source board is turned on, it is necessary to ensure that the light provided by the light source board can cover the entire shooting field of view of the camera device.

[0028] S102 , obtaining image coordinates of a first calibration image displayed by the liquid crystal unit as first image coordinates.

[0029] In one example, step S102 includes: The coordinate average of the pixel coordinates in the black area is obtained as the first image coordinate.

[0030] The black area includes one or more pixel positions. When the black area is one pixel position, the coordinates of the pixel position are the image coordinates of the black area. When the black area includes multiple pixel positions, the coordinates of the black area are determined by obtaining the coordinate average of the pixel coordinates of the multiple pixel positions as the first image coordinates. The first calibration image usually includes multiple black areas, so the first image coordinates will also be multiple.

[0031] In the disclosed embodiment, by obtaining the image coordinates of the black area as the first image coordinates, it is more conducive to the subsequent matching with the coordinates of the second calibration image. When the image acquisition unit captures the checkerboard image, the black area in the captured checkerboard image will shrink, and after the black area shrinks, multiple spaced white areas will be connected into one piece, which is not conducive to determining the image coordinates of the white area. However, the above problem will not occur when the pixel coordinates of the black area are used as the first image coordinates. Even if the black area is shrunk, the position and number of the black area will not change.

[0032] Figure 2 A schematic diagram of a first calibration image provided by an embodiment of the present disclosure. Figure 2 , where the first encoded image is a checkerboard image.

[0033] S103 , controlling the image acquisition unit to capture the first calibration image displayed by the liquid crystal unit as the second calibration image.

[0034] Among them, when the image acquisition unit captures the first calibration image, the exposure of the camera device can be adjusted to a lower level, so that the area of ​​the black area in the first calibration image captured by the image acquisition unit can be reduced, which is more conducive to the subsequent determination of the image coordinates of the second calibration image.

[0035] In addition, when shooting a chessboard image, the chessboard image can be made to cover the entire field of view of the camera device as much as possible, which is helpful to reduce the influence of the lens distortion of the camera device on the calibration.

[0036] Figure 3 A schematic diagram of a second calibration image provided by an embodiment of the present disclosure. Figure 3 ,In the second calibration image, the area of ​​the black region is reduced accordingly.

[0037] S104 . Obtain image coordinates of the second calibration image as second image coordinates.

[0038] In one example, step S104 includes: In the first step, the second calibration image is subjected to an inverse binary operation to form a third calibration image.

[0039] Among them, the inverse binary operation converts the black area in the second calibration image into a white area, and the white area into a black area. The white area corresponds to "1" in the computer program, and the black area corresponds to "0" in the computer program. Performing the inverse binary operation is beneficial for the subsequent computer program to obtain the coordinates of the second image.

[0040] After the second calibration image is debinarized, the black areas are connected and visualized using the connected domain principle.

[0041] Figure 4 A schematic diagram of a third calibration image provided by an embodiment of the present disclosure. Figure 4 , the black areas are connected together, and multiple white areas are distributed at intervals. Figure 4 There are also some smaller white spots in the image, which are caused by environmental factors or stains during the shooting process of the image acquisition unit.

[0042] The second step is to screen the white areas in the second calibration image according to the positions and quantities of the black areas in the first calibration image.

[0043] The position and number of the black area in the first calibration image correspond to the position and number of the white area in the second calibration image. However, due to the influence of the external environment or lens stains, the white area in the second calibration image may not correspond to the black area in the first calibration image. In the second step, the areas in the second calibration image that do not correspond to the areas in the first calibration image are removed, which is beneficial to the subsequent determination of the transformation matrix.

[0044] The third step is to obtain the average coordinates of the pixel coordinates of the white area in the third calibration image as the second image coordinates.

[0045] In step S104, the above steps are used to determine the second image coordinates, which is beneficial to improving the accuracy of the second image coordinates.

[0046] The white area may include one or more pixel coordinates.

[0047] S105 . Determine a transformation matrix based on the first image coordinates and the second image coordinates, and calibrate the liquid crystal unit and the image acquisition unit.

[0048] In one example, step S105 includes: In the first step, a clustering algorithm is used to sort the acquired plurality of the second image coordinates, and the second image coordinates are matched one by one with the first image coordinates.

[0049] The clustering algorithm is a K-Means clustering algorithm, and of course, it can also be other types of clustering algorithms.

[0050] The image coordinates of multiple white areas are clustered by row coordinates using the K-Means clustering algorithm, where the number of clusters is equal to the number of rows. Then, the points in each cluster are sorted from small to large by their ordinates. The average value of the point coordinates of each cluster is calculated, and the clusters are merged in order from small to large in average value, and finally a set of coordinates corresponding to the black pixel grids of the checkerboard in the liquid crystal unit screen (i.e., multiple second image coordinates) is obtained.

[0051] The second step is based on the formula Find the transformation matrix ,in represents the first image coordinates, Represents the second image coordinates.

[0052] in, and is a 3×1 matrix, is a 3×3 matrix.

[0053] in, , , .

[0054] and denote the abscissa and ordinate of the first image coordinates, respectively, and Respectively represent the horizontal and vertical coordinates of the second image coordinates.

[0055] and It can be expressed as:

[0056] In determining and After that, the transformation matrix H can be solved by linear transformation algorithm.

[0057] It is worth noting that in the embodiment of the present disclosure, when solving the transformation matrix H, multiple image coordinates on the liquid crystal unit and multiple second image coordinates on the image acquisition unit are used, and a first image coordinate and its corresponding second image coordinate constitute a pair of image coordinates. When solving the transformation matrix, the more image coordinates are used, the more conducive to the accuracy of the solved transformation matrix. In the embodiment of the present disclosure, a checkerboard image is displayed in the liquid crystal unit, which can ensure that the number of first image coordinates is large, thereby ensuring that the number of logarithms of the image coordinates used to solve the transformation matrix is ​​large, so as to ensure that the accuracy of the solved transformation matrix is ​​high.

[0058] In the embodiment of the present disclosure, a calibration method is provided. The steps of the calibration method are relatively simple and easy to apply. High-precision calibration of the image acquisition unit and the liquid crystal unit can be completed through a computer program. In addition, the calibration method has no requirements on the resolution of the liquid crystal unit, and high-precision calibration can also be achieved for liquid crystal units with lower resolutions.

[0059] Figure 5 This is a schematic diagram of the structure of a camera device provided by an embodiment of the present disclosure. Figure 5 , the camera device 1 comprises: Optical lens 11; An image acquisition unit 12, used to acquire an image incident to the optical lens 11; The liquid crystal unit 13 is used to adjust the brightness of the image acquired by the image acquisition unit 12, and the optical lens 11, the liquid crystal unit 13 and the image acquisition unit 12 are arranged on the incident light path; The control unit 14 is connected to the image acquisition unit 12 and the liquid crystal unit 13. The control unit 14 controls the brightness at each pixel position on the liquid crystal unit 13 through a transformation matrix to achieve pixel-level regulation of the brightness of the image acquired by the image acquisition unit 12. The transformation matrix is ​​obtained by the calibration method described in any of the above items.

[0060] In the disclosed embodiment, the camera device includes a liquid crystal unit and an image acquisition unit, and the control unit can control the brightness of each pixel position in the liquid crystal unit to control the light transmittance at each pixel position of the liquid crystal unit. When the brightness at a certain position in the image captured by the image acquisition unit is too high, the control unit can adjust the light transmittance at the pixel position corresponding to the position in the liquid crystal unit through a transformation matrix, thereby adjusting the brightness of each position in the image captured by the image acquisition unit. The use of a transformation matrix can improve the control accuracy and ensure that the pixel positions of the image acquisition unit and the liquid crystal unit can correspond one to one, thereby achieving pixel-level control of the brightness of the image captured by the image acquisition unit.

[0061] In the embodiment of the present disclosure, the control unit controls the liquid crystal unit to compensate the brightness of the image acquired by the image acquisition unit through the following formula:

[0062]

[0063] Among them, the pixel coordinates in the liquid crystal unit are ( , , 1), the coordinates of the image acquired by the image acquisition unit are ( , , 1), Represents the elements in the transformation matrix, where The value range is 1~3. The value range is 1~3.

[0064] In the embodiment of the present disclosure, the above formula is used to obtain the corresponding pixel coordinates in the liquid crystal unit according to the coordinates of the pixel position whose brightness needs to be adjusted in the image captured by the image acquisition unit, thereby adjusting the brightness of the corresponding pixel position in the liquid crystal unit, thereby realizing pixel-level control of the brightness of the image captured by the image acquisition unit.

[0065] In the embodiment of the present disclosure, the liquid crystal unit 13 is disposed between the optical lens 11 and the image acquisition unit 12 .

[0066] In the disclosed embodiment, the closer the distance between the liquid crystal unit and the image acquisition unit is, the more conducive it is to improving the image quality. In the traditional method, the liquid crystal unit is placed in front of the optical lens, which is convenient to operate but will cause large errors. This is due to the structure of the transmissive liquid crystal unit itself. When external light passes through the liquid crystal unit, scattering occurs. The transmissive liquid crystal unit controls the transmittance of light by controlling the polarization state of the liquid crystal. Because the liquid crystal unit transmits light, a driving circuit must exist between the liquid crystal elements. When the liquid crystal unit is far away from the image acquisition unit, the effect of light scattering is aggravated, resulting in blurred imaging. In the present invention, the liquid crystal unit is arranged between the image acquisition unit and the optical lens, the distance between the image acquisition unit and the liquid crystal unit is minimized, the effect of light scattering is reduced, and the image quality is significantly improved compared with the traditional method.

[0067] In the embodiment of the present disclosure, the image acquisition unit 12 is a complementary metal oxide semiconductor (CMOS) image sensor, and the liquid crystal unit 13 is a liquid crystal screen.

[0068] Figure 6 This is a schematic diagram of the structure of a liquid crystal unit provided by an embodiment of the present disclosure. Figure 6, the liquid crystal unit 13 comprises: A first polarizer 131 and a second polarizer 132 , and a liquid crystal layer 133 disposed between the first polarizer and the second polarizer, wherein the liquid crystal layer 133 is connected to the control unit 14 .

[0069] The liquid crystal unit 133 is electrically connected to the control unit 14 via a control line 134 .

[0070] In the disclosed embodiment, the liquid crystal unit can be controlled at the pixel level. When no voltage is applied, light can pass through the liquid crystal unit, thereby presenting a transparent state. When an appropriate voltage is applied to one or several pixel positions, the liquid crystal molecules are rearranged, and light is blocked at these pixel positions, thereby switching from a transparent state to a semi-transparent state. The degree of transparency is determined by the intensity of the applied voltage.

[0071] In the embodiment of the present disclosure, the first polarizer and the second polarizer are polarizers, which can realize a polarization function.

[0072] Figure 7 A schematic diagram of the structure of a three-dimensional reconstruction system provided by an embodiment of the present disclosure. Figure 7 The three-dimensional reconstruction system includes: a camera device 1, an image emitting device 2 and a measured object 3.

[0073] The structured light working principle of the three-dimensional reconstruction system is based on projecting a light pattern of known structure (such as stripes, grids, etc.) onto the surface of the target object, and then using a camera to capture the deformation of the light pattern caused by the surface morphology of the object. By analyzing these deformed light patterns, the computer algorithm can reconstruct the three-dimensional shape of the object. Specifically, the projector projects a structured light pattern. When the light pattern encounters the surface of the object, it will deform accordingly according to the concavity and shape of the object. The camera captures the deformed pattern and transmits the image to the computer. The computer will calculate based on these deformation information through algorithms such as triangulation, so as to accurately reconstruct the three-dimensional structure of the object. By using the camera provided by the present disclosure, during the three-dimensional reconstruction process, the brightness of the image captured by the camera can be adjusted to ensure that the image captured by the camera is clear, which can solve the problem of excessive brightness of the image of the measured object captured during the three-dimensional reconstruction process.

[0074] It is worth noting that the present invention has shown obvious advantages. First, the present invention proposes to introduce a transmissive liquid crystal unit between the CMOS sensor (image acquisition unit) and the optical lens. Compared with the traditional method of placing a liquid crystal unit outside the camera lens, the light scattering error is smaller and the imaging quality is higher. Secondly, the calibration algorithm proposed in the present invention has low quality requirements for the LCD screen, because the calibration process does not require complex corner point extraction, and even a screen with low resolution or poor display effect can achieve accurate calibration. On the other hand, it has a certain tolerance for the placement of the liquid crystal unit. Even if the liquid crystal unit has a certain rotation angle, it will not significantly affect the calibration result. This fault tolerance greatly improves the practicality and flexibility of the system. In addition, the calibration method of the present invention performs well in adaptability and stability. It can adapt to different light sources and environmental conditions and maintain high-precision calibration in various complex application scenarios. At the same time, due to the simple calibration process, the required equipment and operation costs are low, which is easy to promote and apply. The image acquisition unit and liquid crystal unit calibration method proposed in the present invention achieves high-precision calibration of the image acquisition unit and the liquid crystal unit by cleverly utilizing the transmissive liquid crystal unit, the light source board and the computer control technology. This not only improves the accuracy and efficiency of calibration, but also reduces the requirements for equipment and has broad application prospects.

[0075] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A calibration method, characterized in that: include: Controlling the liquid crystal unit to display a first calibration image; Acquire image coordinates of a first calibration image displayed by the liquid crystal unit as first image coordinates; Controlling the image acquisition unit to capture the first calibration image displayed by the liquid crystal unit as the second calibration image; Obtaining image coordinates of the second calibration image as second image coordinates; A transformation matrix is ​​determined based on the first image coordinates and the second image coordinates, and the liquid crystal unit and the image acquisition unit are calibrated.

2. The calibration method according to claim 1, characterized in that: Controlling the liquid crystal unit to display a first calibration image includes: The transmittance at each pixel position in the liquid crystal unit is regulated, and a checkerboard image is displayed on the liquid crystal unit as a first calibration image, wherein the first calibration image includes a plurality of white areas and a plurality of black areas.

3. The calibration method according to claim 2, characterized in that: Obtaining image coordinates of a first calibration image displayed by the liquid crystal unit as first image coordinates, including: The coordinate average of the pixel coordinates in the black area is obtained as the first image coordinate.

4. The calibration method according to claim 2, characterized in that: Obtaining image coordinates of a second calibration image as second image coordinates includes: The second calibration image is subjected to an inverse binary operation to form a third calibration image; Screening the white areas in the second calibration image according to the positions and quantities of the black areas in the first calibration image; The average coordinates of the pixel coordinates of the white area in the third calibration image are calculated as the second image coordinates.

5. The calibration method according to claim 4, characterized in that: Determining a transformation matrix based on the first image coordinates and the second image coordinates includes: Using a clustering algorithm to sort the acquired plurality of the second image coordinates, and to make the second image coordinates correspond to the first image coordinates one by one; Based on the formula Find the transformation matrix ,in represents the first image coordinates, Represents the second image coordinates.

6. A camera device, characterized in that: include: Optical lens; An image acquisition unit, used to acquire an image incident to the optical lens; A liquid crystal unit, used to adjust the brightness of the image acquired by the image acquisition unit, wherein the optical lens, the liquid crystal unit and the image acquisition unit are arranged on the incident light path; A control unit is connected to the image acquisition unit and the liquid crystal unit. The control unit controls the brightness at each pixel position on the liquid crystal unit through a transformation matrix to achieve pixel-level regulation of the brightness of the image acquired by the image acquisition unit. The transformation matrix is ​​obtained by the calibration method according to any one of claims 1 to 5.

7. The imaging device according to claim 6, wherein: The control unit controls the liquid crystal unit to compensate the brightness of the image acquired by the image acquisition unit through the following formula: Among them, the pixel coordinates in the liquid crystal unit are ( , , 1), the coordinates of the image acquired by the image acquisition unit are ( , , 1), Represents the elements in the transformation matrix, where The value range is 1~3. The value range is 1~3.

8. The imaging device according to claim 6, wherein: The liquid crystal unit is arranged between the optical lens and the image acquisition unit.

9. The imaging device according to claim 6, wherein: The liquid crystal unit comprises: A first polarizer and a second polarizer, and a liquid crystal layer disposed between the first polarizer and the second polarizer, wherein the liquid crystal layer is connected to the control unit.

10. The imaging device according to claim 9, characterized in that: The first polarizer and the second polarizer are polarizers.

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