A method for image correction of linear array cameras

Abstract

The present invention discloses a linear array camera image correction method, wherein the arc target radius R and the arc center are known in the world physical coordinate system XOY w , the coordinates of the camera target center installed in the arc (X0, Y0), the camera axis and XOY w The X-axis deflection angle α, the horizontal pixel of the linear array camera represents the distance d u and the camera focal length f. S1: Calculate the intersection of the line array camera's optical axis and the arc. S2: Iterate through the pixel points, obtaining the intersection of each point on the arc and then its arc angle. S3: Based on the relative arc angle difference between the specific point and the center point, calculate the arc distance of each point from the center-arc intersection, which serves as the point's relative position in the unfolded image. S4: Reconstruct the image based on the distance between each point and the center point. Based on the relative pose relationship between the arc and the camera imaging model, the coordinates of the image pixels in objective physical space are recovered. Image reconstruction is performed based on these coordinates, thus obtaining true relative information reflecting the target along the arc path.

Description

Technical Field

[0001] The present invention relates to the technical field of line array camera image correction, and in particular to a line array camera image correction method. Background Art

[0002] In engineering applications, line scan cameras often encounter non-flat objects. This is especially true for circular surfaces like tunnels. The image lines formed by a line scan camera at a given moment actually represent the projection of the arc wall within the field of view. To achieve functions like overall stitching and object size measurement, the projected image of the arc surface must be corrected to flatten it along the arc.

[0003] Currently, all image correction methods rely on perspective transformations that abstract the captured object into a flat surface. There are no correction methods specifically designed for linear array cameras used for imaging on circular surfaces. After extensive research, the inventors have proposed a linear array camera image correction method that, given the known relative position of the camera and the circular surface, restores the flattened image of the circular surface. Summary of the Invention

[0004] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a method for correcting an image of a linear array camera.

[0005] The purpose of the present invention is achieved through the following technical solutions: A linear array camera image correction method, wherein the arc target radius R and the arc center are known in the world physical coordinate system. , the coordinates of the camera target center installed in the arc , camera axis and of Axis deflection angle , the horizontal pixels of the line array camera represent the distance and camera focal length , including the following steps:

[0006] S1: Find the intersection of the optical axis of the linear array camera and the circular arc, and calculate the arc distance between the circular arc intersection corresponding to each pixel and the intersection of the optical axis and the circular arc;

[0007] S2: Get the intersection point of each pixel on the arc, and then get its arc angle;

[0008] S3: Based on the relative arc distance between the specific point and the center point, the distance between each point and the intersection of the center and the arc is obtained as the relative position of the point in the expanded diagram;

[0009] S4: Reconstruct the image based on the distance between each point and the center point.

[0010] Preferably, step S1 further includes the following steps:

[0011] S11: According to the pinhole imaging principle, take the first Construct a one-dimensional vector from the image grayscale of the line ;

[0012] in, is the number of horizontal pixels of the line array camera;

[0013] S12: Optical axis straight line exist The equation in the coordinate system is:

[0014] ;

[0015] According to the system of equations,

[0016] ;

[0017] Conclusion Intersection point with arc .

[0018] Preferably, in step S2, the arc intersection point is obtained Angle in radians in a circular arc ,

[0019] .

[0020] Preferably, step S3 further includes the following steps:

[0021] S31: For one-dimensional vector points in the camera coordinate system The pixel coordinates are

[0022] ;

[0023] S32: The angle between the imaging line of the pixel point and the optical axis is ,

[0024] ;

[0025] S33: No. The imaging line corresponding to the point exist The equation in the coordinate system is

[0026] ;

[0027] According to the system of equations

[0028] ;

[0029] Solved Intersection with arc ;

[0030] S34: Find the arc intersection point again Angle in radians in a circular arc ,

[0031] ;

[0032] Then the arc segment The length is,

[0033] ;

[0034] That is, the pixels to the left of the center of the image Pixels to the right of the image center are negative Is a positive value.

[0035] Preferably, step S4 further includes the following steps:

[0036] S41: Traverse the image of the linear array camera All pixels in the horizontal direction of the line are obtained after each pixel is flattened relative to Construct a one-dimensional distance vector from the physical distance in the horizontal direction ;

[0037] S42: The first The horizontal coordinates of all pixels in the horizontal direction of the line in the new composition are

[0038] ;

[0039] in, The target pixel represents the distance of the corrected image, the unit is m / pixel, ceil is rounded up,

[0040] S43: The first All horizontal pixels of the line are normalized in the horizontal coordinates of the new composition.

[0041] ;

[0042] Assign the first The corresponding grayscale values ​​of all pixels horizontally along the line in the new composition for The positions where there are no calculated pixels are filled with pixels by linear interpolation of adjacent calculated pixels to obtain the first pixel in the line array camera image. The rectified image of the line.

[0043] The present invention has the following advantages: the present invention restores the coordinates of image pixel points in the objective physical space based on the relative posture relationship between the arc and the camera imaging model, and reconstructs the image based on the coordinates, thereby obtaining real relative information reflecting the target on the arc path. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 This is a schematic diagram of the structure of the line array camera image correction;

[0045] Figure 2 This is a schematic diagram of the structure of the linear array camera after image correction and amplification;

[0046] Figure 3 It is a structural diagram for comparing the corrected image with the original image;

[0047] Figure 4 This is a structural diagram of the positional relationship between the linear array camera and the arc wall; DETAILED DESCRIPTION

[0048] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings herein can be arranged and designed in various different configurations.

[0049] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention as claimed, but rather merely represents selected embodiments of the present invention. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort are also within the scope of protection of the present invention.

[0050] It should be noted that, in the absence of conflict, the embodiments and features of the embodiments of the present invention can be combined with each other.

[0051] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, it does not need to be further defined or explained in subsequent drawings.

[0052] In the description of the present invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," "outer," etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, or are the orientations or positional relationships in which the inventive product is typically placed when in use, or are the orientations or positional relationships commonly understood by those skilled in the art. These terms are intended only to facilitate the description of the present invention and to simplify the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation. Therefore, they should not be construed as limiting the present invention. Furthermore, the terms "first," "second," etc., etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0053] In the description of the present invention, it should also be noted that, unless otherwise expressly specified or limited, the terms "disposed," "installed," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed connections, detachable connections, or integral connections; they may refer to mechanical connections or electrical connections; they may refer to direct connections or indirect connections through an intermediate medium; and they may refer to internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances.

[0054] In this embodiment, if Figure 1 and Figure 4 As shown in the figure, a linear array camera image correction method is shown. The arc target radius R and the arc center in the world physical coordinate system are known. , the coordinates of the camera target center installed in the arc , camera axis and of Axis deflection angle , the horizontal pixels of the line array camera represent the distance and camera focal length , including the following steps:

[0055] S1: Find the intersection of the optical axis of the linear array camera and the circular arc, and calculate the arc distance between the circular arc intersection corresponding to each pixel and the intersection of the optical axis and the circular arc;

[0056] S2: Get the intersection point of each pixel on the arc, and then get its arc angle;

[0057] S3: Based on the relative arc distance between the specific point and the center point, the distance between each point and the intersection of the center and the arc is obtained as the relative position of the point in the expanded diagram;

[0058] S4: Reconstruct the image based on the distance between each point and the center point. Based on the relative pose of the arc and the camera imaging model, the coordinates of the image pixels in objective physical space are restored. Image reconstruction is performed based on these coordinates, thereby obtaining true relative information reflecting the target along the arc path. In this embodiment, because the camera's pose relative to the arc remains constant, the true distances calculated for each point in steps S2 and S3 are consistent across all image lines of the linear array camera. This calculation only needs to be performed once, and S4 only requires the same repositioning and reconstruction of the remaining lines.

[0059] Further, such as Figure 2 As shown, step S1 further includes the following steps:

[0060] S11: According to the pinhole imaging principle, take the first Construct a one-dimensional vector from the image grayscale of the line ;

[0061] in, is the number of horizontal pixels of the line array camera;

[0062] S12: Optical axis straight line exist The equation in the coordinate system is:

[0063] ;

[0064] According to the system of equations,

[0065] ;

[0066] Conclusion Intersection point with arc .

[0067] Furthermore, in step S2, the arc intersection point is obtained Angle in radians in a circular arc ,

[0068] .

[0069] In this embodiment, step S3 further includes the following steps:

[0070] S31: For one-dimensional vector points in the camera coordinate system The pixel coordinates are

[0071] ;

[0072] S32: The angle between the imaging line of the pixel point and the optical axis is ,

[0073] ;

[0074] S33: No. The imaging line corresponding to the point exist The equation in the coordinate system is

[0075] ;

[0076] According to the system of equations

[0077] ;

[0078] Solved Intersection with arc ;

[0079] S34: Find the arc intersection point again Angle in radians in a circular arc ,

[0080] ;

[0081] Then the arc segment The length is,

[0082] ;

[0083] That is, the pixels to the left of the center of the image Pixels to the right of the image center are negative Is a positive value.

[0084] Furthermore, step S4 further includes the following steps:

[0085] S41: Traverse the image of the linear array camera All pixels in the horizontal direction of the line are obtained after each pixel is flattened relative to Construct a one-dimensional distance vector from the physical distance in the horizontal direction ;

[0086] S42: The first The horizontal coordinates of all pixels in the horizontal direction of the line in the new composition are

[0087] ;

[0088] in, The target pixel of the corrected image represents the distance, and the unit is m / pixel. Ceil is rounded up. In this embodiment, it can be set to 0.01 m / pixel.

[0089] S43: The first All horizontal pixels of the line are normalized in the horizontal coordinates of the new composition.

[0090] ;

[0091] Specifically, the first The purpose of normalizing the horizontal coordinates of all pixels in the horizontal direction of the line in the new composition is to ensure that all coordinates are positive numbers.

[0092] like Figure 3 As shown, the first The corresponding grayscale values ​​of all pixels horizontally along the line in the new composition for The positions where there are no calculated pixels are filled with pixels by linear interpolation of adjacent calculated pixels to obtain the first pixel in the line array camera image. The corrected image of the lines is obtained, thereby achieving the flattening of the arc surface image according to the physical size.

[0093] This method can be used for visual inspection and measurement of tunnels, pipelines, etc.

[0094] Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments, or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A linear array camera image correction method, where the arc target radius R and the arc center are known in the world physical coordinate system. , the coordinates of the camera target center installed in the arc , camera axis and of Axis deflection angle , the horizontal pixels of the line array camera represent the distance and camera focal length , characterized in that: The following steps are involved: S1: Find the intersection of the optical axis of the linear array camera and the circular arc, and calculate the arc distance between the circular arc intersection corresponding to each pixel and the intersection of the optical axis and the circular arc; S2: Get the intersection point of each pixel on the arc, and then get its arc angle; S3: Based on the relative arc distance between the specific point and the center point, the distance between each point and the intersection of the center and the arc is obtained as the relative position of the point in the expanded diagram; S4: reconstruct the image based on the distance between each point and the center point; The step S4 further includes the following steps: S41: Traverse the image of the linear array camera All pixels in the horizontal direction of the line are obtained after each pixel is flattened relative to Construct a one-dimensional distance vector from the physical distance in the horizontal direction ; S42: The first The horizontal coordinates of all pixels in the horizontal direction of the line in the new composition are ； in, The target pixel represents the distance of the corrected image, the unit is m / pixel, ceil is rounded up, S43: The first All horizontal pixels of the line are normalized in the horizontal coordinates of the new composition. ； Assign the first The corresponding grayscale values ​​of all pixels horizontally along the line in the new composition for The positions where there are no calculated pixels are filled with pixels by linear interpolation of adjacent calculated pixels to obtain the first pixel in the line array camera image. The corrected image of the line.

2. The method for correcting an image of a line array camera according to claim 1, wherein: The step S1 further includes the following steps: S11: According to the pinhole imaging principle, take the first Construct a one-dimensional vector from the image grayscale of the line ; in, is the number of horizontal pixels of the line array camera; S12: Optical axis straight line exist The equation in the coordinate system is: ； According to the system of equations, ； Conclusion Intersection point with arc .

3. The method for correcting an image of a line array camera according to claim 2, wherein: In step S2, the arc intersection point is obtained. Angle in radians in a circular arc , 。 4. The method for correcting a line array camera image according to claim 3, wherein: The step S3 further includes the following steps: S31: For one-dimensional vector points in the camera coordinate system The pixel coordinates are ； S32: The angle between the imaging line of the pixel point and the optical axis is , ； S33: No. The imaging line corresponding to the point exist The equation in the coordinate system is ； According to the system of equations ； Solved Intersection with arc ; S34: Find the arc intersection point again Angle in radians in a circular arc , ； Then the arc segment The length is, ； That is, the pixels to the left of the center of the image Pixels to the right of the image center are negative Is a positive value.

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