CN115018923A - Method and system for detecting panoramic annular lens parameters - Google Patents
Method and system for detecting panoramic annular lens parameters Download PDFInfo
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Abstract
The invention relates to a method and a system for detecting panoramic annular lens parameters, which comprises the following steps: collecting different calibration images in at least four different areas of a lens view field by using a checkerboard calibration plate and a panoramic annular lens; selecting all inner corner points of the checkerboard according to the calibration image to perform calibration calculation to obtain a polynomial fitting relation curve of the ray segment height and the pixel height; obtaining a corresponding relation curve of the field angle and the pixel height according to the polynomial fitting relation curve and the corresponding relation curve of the ray section height and the field angle; selecting an effective field of view from the calibration image to obtain the positions of a minimum field of view and a maximum field of view so as to respectively obtain corresponding pixel heights; and matching a corresponding relation curve of the field angle and the pixel height according to the corresponding pixel height to obtain the field angle of the panoramic annular lens. The invention can realize the detection of the parameters of the panoramic annular lens only by utilizing the panoramic annular lens to shoot images of the calibration plate at different positions.
Description
Technical Field
The invention belongs to the technical field of camera calibration, and particularly relates to a method and a system for detecting parameters of a panoramic annular lens.
Background
With the development of artificial intelligence, computer vision has become one of the indispensable key technologies. One of the prerequisites for computer vision applications is to obtain as much scene information as possible. Compared with the traditional pinhole imaging mode based on perspective projection, the panoramic imaging system can image a hemispherical field of view which is larger than 180 degrees in the horizontal or vertical direction, so that visual information far more than one perspective image is obtained.
The focal length, field of view, and distortion model are key parameters for the lens. The focal length can measure the light beam convergence and divergence capacity of the lens, provides the optimal shooting distance for the lens, and guides the installation position of an image sensor (sensor); the field of view can measure the imaging range of the lens and provide reference for lens installation in an actual scene; the distortion model can correct the distortion of the lens and acquire an image more in line with the vision of human eyes.
In the prior art, for lens parameters including focal length, field angle and distortion, the detection requires a central field to participate in imaging; however, for a panoramic annular lens, in the case that there is a blind zone in the central field, a corresponding detection method is lacking; especially for the focal length, due to the existence of the central dead zone of the panoramic annular lens, the focal length cannot be measured by utilizing the common angle measurement change or magnification because the focal length does not belong to the paraxial region outside the dead zone and has distortion.
Disclosure of Invention
Based on the above-mentioned shortcomings and drawbacks of the prior art, an object of the present invention is to at least solve one or more of the above-mentioned problems of the prior art, in other words, to provide a method and a system for detecting parameters of a panoramic annular lens, which satisfy one or more of the above-mentioned needs.
In order to achieve the purpose, the invention adopts the following technical scheme:
a method for detecting parameters of a panoramic annular lens comprises the following steps:
s1, collecting different calibration images in at least four different areas of a lens view field by using a checkerboard calibration board and a panoramic annular lens; the chessboard grid calibration plate is filled in the field of view between the minimum field of view and the maximum field of view of the panoramic annular lens;
s2, selecting all inner corner points of the checkerboard according to the calibration image to perform calibration calculation to obtain a polynomial fitting relation curve of the ray segment height and the pixel height; the pixel height is the distance between a point on an image surface of an image sensor of the panoramic annular lens and the center of the image surface, the ray segment height is a Z-direction coordinate value of the point on the image surface in the space where the image surface is located, and the image surface is an XOY plane;
s3, obtaining a corresponding relation curve of the field angle and the pixel height according to the polynomial fitting relation curve of the ray section height and the pixel height and the corresponding relation curve of the ray section height and the field angle;
s4, selecting an effective field of view from the calibration image to obtain the positions of the minimum field of view and the maximum field of view so as to obtain pixel heights corresponding to the positions of the minimum field of view and the maximum field of view respectively;
and S5, matching the corresponding relation curve of the field angle and the pixel height according to the pixel height respectively corresponding to the positions of the minimum field of view and the maximum field of view to obtain the field angle of the panoramic annular lens.
Preferably, when the center of the image plane of the image sensor of the panoramic annular lens is taken as the origin, the coordinates of a point on the image plane are (u, v), and the pixel height ρ is
The ray segment height f (rho) is a Z-direction coordinate value of the coordinate point (u, v) in the space of the image surface, namely (u, v, f (rho)) is a three-dimensional point of the space of the image surface, and the equal proportion corresponds to the real object space;
the coordinates at which the three-dimensional point (u, v, f (ρ)) is projected onto the image plane are (u, v).
Preferably, in step S2, the polynomial fitting relation curve of the ray segment height and the pixel height is:
f(ρ)＝a 0 +a 1 ρ+a 2 ρ 2 +…+a m ρ m
wherein, a 0 、a 1 、a 2 、…、a m Is a fitting coefficient; m is a polynomial degree.
Preferably, in step S3, the correspondence curve between the ray segment height and the field angle is:
f(ρ)＝ρ*tanθ
where θ is the angle of view.
Preferably, in step S3, the correspondence curve between the angle of view and the pixel height is:
as a preferred scheme, the method for detecting the panoramic annular lens parameters further comprises the following steps:
step S6, equating the corresponding relation curve of the angle of view and the ray segment height to a linear model, that is, θ ═ k ρ + b, where k and b are the slope and intercept of the linear model respectively;
and then the focal length f of the panoramic annular lens is fitted according to the ratio of the height difference delta y of any two points on the calibrated image on the image to the difference delta theta of the field angle to obtain a focal length fitting line:
wherein, y 1 、y 2 Respectively corresponding to the image heights of any two points on the calibration image on the image; rho 1 、ρ 2 The pixel heights of any two points on the calibration image on the image surface are respectively corresponding, and the corresponding pixel numbers are respectively n 1 、n 2 And ps is the size of a single pixel on the image surface, and 1000 is the conversion relation from the image size millimeter level to the image surface size micron level.
As a preferred scheme, the method for detecting the panoramic annular lens parameters further comprises the following steps:
s7, calculating the height of a theoretical pixel at each field angle position according to the angle, and obtaining the error e at each field angle position according to the ratio of the difference between the actual pixel height and the theoretical pixel height to the theoretical pixel height, namely the distortion model curve is as follows:
where ρ is the actual pixel height, ρ t Is the theoretical pixel height; rho t ＝f*θ。
As a preferred scheme, the method for detecting the panoramic annular lens parameters further comprises the following steps:
and outputting a polynomial fitting relation curve of the height of the display ray segment and the height of the pixel, a corresponding relation curve of the field angle and the height of the pixel, a focal length fitting line and a distortion model curve.
The invention also provides a system for detecting the parameters of the panoramic annular lens, which applies the detection method in the scheme and comprises the following steps:
the acquisition module is used for acquiring different calibration images in at least four different areas of a lens view field by utilizing the checkerboard calibration board and the panoramic annular lens; the chessboard grid calibration plate is filled in the field of view between the minimum field of view and the maximum field of view of the panoramic annular lens;
the calibration module is used for selecting all inner corner points of the checkerboard according to the calibration image to perform calibration calculation to obtain a polynomial fitting relation curve of the ray segment height and the pixel height; the pixel height is the distance between a point on an image surface of an image sensor of the panoramic annular lens and the center of the image surface, the ray segment height is a Z-direction coordinate value of the point on the image surface in the space where the image surface is located, and the image surface is an XOY plane;
the conversion module is used for obtaining a corresponding relation curve of the field angle and the pixel height according to the polynomial fitting relation curve of the ray section height and the pixel height and the corresponding relation curve of the ray section height and the field angle;
the calculation module is used for selecting the positions of the minimum view field and the maximum view field corresponding to the effective view field in the calibration image, and calculating pixel heights respectively corresponding to the positions of the minimum view field and the maximum view field;
and the matching module is used for matching the corresponding relation curve of the field angle and the pixel height according to the pixel height respectively corresponding to the positions of the minimum field of view and the maximum field of view to obtain the field angle of the panoramic annular lens.
As a preferred scheme, the system for detecting the parameters of the panoramic annular lens further comprises:
and the output display module is used for outputting and displaying a polynomial fitting relation curve of the field angle, the ray section height and the pixel height of the panoramic annular lens and a corresponding relation curve of the field angle and the pixel height.
Compared with the prior art, the invention has the beneficial effects that:
the invention only needs to utilize the panoramic annular lens to shoot images of the calibration plate at different positions, realizes the calculation of the parameters (focal length, field angle and distortion model) of the panoramic annular lens, does not need to use a parallel light incidence mode to calculate in the calculation process of the optical platform, has no strict limitation on the arrangement of the chessboard grid calibration plate, and is simple, convenient and fast.
The invention provides necessary lens parameter measurement indexes for the panoramic annular lens and provides parameter guidance for subsequent application of the panoramic annular lens in each scene, expansion calculation, measurement and the like of the panoramic annular image.
Drawings
FIG. 1 is a schematic view of a checkerboard calibration plate in embodiment 1 of the present invention;
FIG. 2 is a calibration image collected in embodiment 1 of the present invention;
FIG. 3 is a graph of a polynomial fit relationship of ray segment height and pixel height for a panoramic annular lens according to an embodiment of the present invention;
fig. 4 is a graph showing the correspondence between the field angle and the pixel height of the panoramic annular lens in embodiment 1 of the present invention;
FIG. 5 is a labeled diagram of the minimum field of view and the maximum field of view of the panoramic annular lens in embodiment 1 of the present invention;
FIG. 6 is a focal length fit line diagram of a panoramic annular lens according to embodiment 1 of the present invention;
FIG. 7 is a distortion curve chart of embodiment 1 of the present invention;
fig. 8 is a block configuration diagram of a system for detecting parameters of a panoramic annular lens according to embodiment 1 of the present invention.
Detailed Description
In order to more clearly illustrate the embodiments of the present invention, the following description will explain the embodiments of the present invention with reference to the accompanying drawings. It is obvious that the drawings in the following description are only some examples of the invention, and that for a person skilled in the art, other drawings and embodiments can be derived from them without inventive effort.
Example 1:
the method for detecting the panoramic annular lens parameters comprises the following steps:
s1, collecting different calibration images in at least four different areas of a lens view field by using a checkerboard calibration board and a panoramic annular lens; the chessboard grid calibration plate is filled in the field of view between the minimum field of view and the maximum field of view of the panoramic annular lens; the checkerboard calibration plate is as shown in fig. 1, and the checkerboard calibration plate is filled in the field of view between the minimum field of view and the maximum field of view of the panoramic annular lens, so that the subsequent calculation can utilize the field of view as large as possible to obtain the result as accurate as possible.
Specifically, by rotating the panoramic annular lens, different calibration images are acquired in at least four different areas of the lens field of view, wherein one calibration image is as shown in fig. 2.
S2, selecting all inner corner points of the checkerboard according to the calibration image to perform calibration calculation to obtain a polynomial fitting relation curve of the ray segment height and the pixel height; the pixel height is the distance between a point on an image surface of an image sensor of the panoramic annular lens and the center of the image surface, the ray segment height is a Z-direction coordinate value of the point on the image surface in the space where the image surface is located, and the image surface is an XOY plane.
The calibration calculation mode is to define a ray segment height f (rho), model the ray segment height f (rho) into a polynomial, and fit the polynomial by using a mode of minimizing reprojection errors to obtain a calibration result, namely a polynomial fitting relation curve of the ray segment height and the pixel height.
Specifically, the center of an image plane of an image sensor of the panoramic annular lens is taken as an origin, and coordinates are (0, 0); the coordinates of a point on the image plane are (u, v), the pixel height ρ is
Since a real object is imaged on the image sensor via the imaging system, the distance from the center of the image plane is taken as the pixel height.
The ray segment height f (rho) is a Z-direction coordinate value of the coordinate point (u, v) in the space of the image surface, namely (u, v, f (rho)) is a three-dimensional point of the space of the image surface, and the equal proportion corresponds to the real object space; the coordinates at which the three-dimensional point (u, v, f (ρ)) is projected onto the image plane (i.e., the XOY plane) are (u, v).
The polynomial fitting relation curve of the ray segment height and the pixel height in this embodiment is:
f(ρ)＝a 0 +a 1 ρ+a 2 ρ 2 +…+a m ρ m
wherein, a 0 、a 1 、a 2 、…、a m Is a fitting coefficient; m is a polynomial degree.
More specifically, the panoramic annular lens of the present embodiment can be modeled as a fourth-order polynomial, that is, m is 4; inputting the actual size of the checkerboard, which is 22mm in this embodiment, and inputting the number of the used checkerboard, this embodiment uses the position with clear boundary inside the checkerboard, i.e. removing the 7 × 5 checkerboard at the center of the outermost circle, i.e. 7 and 5 in two directions, respectively, and each parameter of the fourth-order polynomial can be calculated by minimizing the reprojection error.
In addition, a polynomial fitting relation curve showing the ray segment height f (ρ) and the pixel height ρ is also output, as shown in fig. 3, so as to intuitively acquire the relation between the ray segment height f (ρ) and the pixel height ρ. Wherein the pixel height can be measured using a calibration image.
And S3, obtaining a corresponding relation curve of the field angle and the pixel height according to the polynomial fitting relation curve of the ray section height and the pixel height and the corresponding relation curve of the ray section height and the field angle.
The corresponding relation curve of the ray section height f (rho) and the field angle theta is as follows:
f(ρ)＝ρ*tanθ
where θ is the angle of view.
Correspondingly, the ray segment height f (ρ) of a certain point in the calibration image on the image surface can be converted into the angle of view θ on the image, and the corresponding relation curve of the angle of view θ and the pixel height ρ is obtained as follows:
wherein the value range of theta is-90 degrees to 90 degrees.
The present embodiment outputs a displayed correspondence curve of the angle of view θ and the pixel height ρ, as shown in fig. 4.
S4, selecting an effective field of view from the calibration image to obtain the positions of the minimum field of view and the maximum field of view so as to obtain pixel heights corresponding to the positions of the minimum field of view and the maximum field of view respectively;
specifically, an inner ring and an outer ring are marked on the acquired calibration image, and an effective field of view is formed between the inner ring and the outer ring, so that the positions of the minimum field of view and the maximum field of view are obtained, as shown in fig. 5.
And S5, matching the corresponding relation curve of the field angle and the pixel height according to the pixel height respectively corresponding to the positions of the minimum field of view and the maximum field of view to obtain the field angle of the panoramic annular lens.
Specifically, according to a pixel height calculation formula, obtaining pixel height matching field angles corresponding to the positions of the minimum field of view and the maximum field of view respectively, and then matching a corresponding relation curve of the field angles and the pixel heights; that is, according to the field of view of the panoramic annular lens, the conversion angle is the field angle of the panoramic annular lens, and the field angle of the present embodiment is 38.41 ° to 99.78 °.
Step S6, equating the corresponding relation curve of the angle of view and the ray segment height to a linear model, that is, θ ═ k ρ + b, where k and b are the slope and intercept of the linear model respectively;
then, the focal length f of the panoramic annular lens is fitted according to the ratio of the height difference delta y of any two points on the calibrated image on the image to the difference delta theta of the field angle to obtain a focal length fitting line, which is as follows:
wherein, y 1 、y 2 Respectively calibrating the image heights of any two points on the image corresponding to the image; rho 1 、ρ 2 The pixel heights of any two points on the calibration image on the image surface are respectively corresponding, and the corresponding pixel numbers are respectively n 1 、n 2 And ps is the size of a single pixel on the image surface, and 1000 is the conversion relation from the image size millimeter level to the image surface size micron level.
More specifically, the positions of an inner ring and an outer ring corresponding to the field of view where a checkerboard effective for lens calibration is located are marked on the panoramic annular lens, in this embodiment, a position with a clear boundary inside the checkerboard is used, that is, 7 × 5 checkerboards at the center and at the outermost circle are removed, and a corresponding relationship curve of the field angle θ and the pixel height ρ is calculated again between the inner ring and the outer ring, and the curve can be approximately fitted into a straight line by using a least square method; according to the f-theta model, the distortion of the f-theta model of the visual field where the actual use part of the checkerboard calibration plate is located is very small, and the focal length f of the panoramic annular lens can be obtained according to the slope of a straight line; accordingly, θ 1 、θ 2 The angles of view corresponding to the outer and inner rings on the calibration image, y 1 、y 2 The outer ring and the inner ring on the calibration image correspond to the image height on the image and can be directly measured in the image; rho 1 、ρ 2 The outer ring and the inner ring on the calibration image correspond to the pixel heights on the image plane (namely the radiuses of the outer ring and the inner ring), and the corresponding pixel numbers are n 1 、n 2 And ps is the size of a single pixel on the image surface, and 1000 is the conversion relation from the image size millimeter level to the image surface size micron level. The focal length fitting line output and displayed by the embodiment is shown in fig. 6.
S7, calculating theoretical pixel height according to the angle at each field angle position according to the f-theta model, and obtaining an error e at each field angle position according to the ratio of the difference between the actual pixel height and the theoretical pixel height to the theoretical pixel height, namely a distortion model curve is as follows:
where ρ is the actual pixel height, ρ t Is the theoretical pixel height; rho t ＝f*θ。
Calculating theoretical pixel height rho according to the angle and focal length at each view field angular position t Calibrating according to the size of the checkerboard to obtain the actual pixel height rho; the distortion model curve output and displayed by the embodiment is shown in fig. 7.
Based on the above detection method for the panoramic annular lens parameters, as shown in fig. 8, the embodiment further provides a detection system for the panoramic annular lens parameters, which includes an acquisition module, a calibration module, a conversion module, a calculation module, a matching module, and an output display module.
Specifically, the acquisition module of the embodiment is configured to acquire different calibration images in at least four different areas of a lens field of view by using a checkerboard calibration board and a panoramic annular lens; the chessboard grid calibration plate is filled in the field of view between the minimum field of view and the maximum field of view of the panoramic annular lens; the checkerboard calibration plate is as shown in fig. 1, and the checkerboard calibration plate is filled in the field of view between the minimum field of view and the maximum field of view of the panoramic annular lens, so that the subsequent calculation can utilize the field of view as large as possible to obtain the result as accurate as possible. Different calibration images can be collected in at least four different areas of the lens field of view by rotating the panoramic annular lens, wherein one calibration image is shown in fig. 2.
The calibration module of the embodiment is used for selecting all inner corner points of the checkerboard according to the calibration image to perform calibration calculation to obtain a polynomial fitting relation curve of ray segment height and pixel height; the pixel height is the distance between a point on an image surface of an image sensor of the panoramic annular lens and the center of the image surface, the ray segment height is a Z-direction coordinate value of the point on the image surface in the space where the image surface is located, and the image surface is an XOY plane;
the calibration calculation mode is to define a ray segment height f (rho), model the ray segment height f (rho) into a polynomial, and fit the polynomial by using a mode of minimizing reprojection errors to obtain a calibration result, namely a polynomial fitting relation curve of the ray segment height and the pixel height.
Specifically, the center of an image plane of an image sensor of the panoramic annular lens is taken as an origin, and coordinates are (0, 0); the coordinates of a point on the image plane are (u, v), the pixel height ρ is
Since a real object is imaged on the image sensor via the imaging system, the distance from the center of the image plane is taken as the pixel height.
The ray segment height f (rho) is a Z-direction coordinate value of the coordinate point (u, v) in the space of the image surface, namely (u, v, f (rho)) is a three-dimensional point of the space of the image surface, and the equal proportion corresponds to the real object space; the coordinates at which the three-dimensional point (u, v, f (ρ)) is projected onto the image plane (i.e., the XOY plane) are (u, v).
The polynomial fitting relation curve of the ray segment height and the pixel height in this embodiment is:
f(ρ)＝a 0 +a 1 ρ+a 2 ρ 2 +…+a m ρ m
wherein, a 0 、a 1 、a 2 、…、a m Is a fitting coefficient; m is a polynomial degree.
More specifically, the panoramic annular lens of the embodiment can be modeled as a fourth-order polynomial, that is, m is 4; inputting the actual size of the checkerboard, which is 22mm in this embodiment, and inputting the number of the used checkerboard, this embodiment uses the position with clear boundary inside the checkerboard, i.e. removing the 7 × 5 checkerboard at the center of the outermost circle, i.e. 7 and 5 in two directions, respectively, and each parameter of the fourth-order polynomial can be calculated by minimizing the reprojection error.
In addition, a polynomial fitting relation curve showing the ray segment height f (ρ) and the pixel height ρ is also output, as shown in fig. 3, so as to intuitively acquire the relation between the ray segment height f (ρ) and the pixel height ρ. Wherein the pixel height can be measured using a calibration image.
The conversion module of this embodiment is configured to obtain a corresponding relationship curve between the field angle and the pixel height according to the polynomial fitting relationship curve between the ray segment height and the pixel height and the corresponding relationship curve between the ray segment height and the field angle.
Specifically, the correspondence curve between the ray segment height f (ρ) and the field angle θ is:
f(ρ)＝ρ*tanθ
where θ is the angle of view.
Correspondingly, the ray segment height f (ρ) of a certain point in the calibration image on the image surface can be converted into the field angle θ on the image, and the corresponding relation curve of the field angle θ and the pixel height ρ is obtained as follows:
wherein the value range of theta is-90 degrees to 90 degrees.
The calculation module of this embodiment is configured to select the positions of the minimum field of view and the maximum field of view corresponding to the effective field of view in the calibration image, and calculate pixel heights corresponding to the positions of the minimum field of view and the maximum field of view, respectively.
Specifically, an inner ring and an outer ring are marked on the acquired calibration image, and an effective field of view is formed between the inner ring and the outer ring, so that the positions of the minimum field of view and the maximum field of view are obtained, as shown in fig. 5.
The matching module of the embodiment is used for matching a corresponding relation curve of the field angle and the pixel height according to the pixel height respectively corresponding to the positions of the minimum field of view and the maximum field of view to obtain the field angle of the panoramic annular lens.
Specifically, according to a pixel height calculation formula, obtaining pixel height matching field angles corresponding to the positions of the minimum field of view and the maximum field of view respectively, and then matching a corresponding relation curve of the field angles and the pixel heights; that is, according to the field of view of the panoramic annular lens, the conversion angle is the field angle of the panoramic annular lens, and the field angle of the present embodiment is 38.41 ° to 99.78 °.
The conversion module of this embodiment is further configured to make a corresponding relationship curve between the field angle and the ray segment height equivalent to a linear model, that is, θ ═ k ρ + b, and k and b are a slope and an intercept of the linear model, respectively;
then, the focal length f of the panoramic annular lens is fitted according to the ratio of the height difference delta y of any two points on the calibrated image on the image to the difference delta theta of the field angle to obtain a focal length fitting line, which is as follows:
wherein, y 1 、y 2 Respectively calibrating the image heights of any two points on the image corresponding to the image; rho 1 、ρ 2 The pixel heights of any two points on the calibration image on the image surface are respectively corresponding, and the corresponding pixel numbers are respectively n 1 、n 2 And ps is the size of a single pixel on the image surface, and 1000 is the conversion relation from the image size millimeter level to the image surface size micron level.
More specifically, the positions of an inner ring and an outer ring corresponding to the field of view where a checkerboard effective for lens calibration is located are marked on the panoramic annular lens, in this embodiment, a position with a clear boundary inside the checkerboard is used, that is, 7 × 5 checkerboards at the center and at the outermost circle are removed, and a corresponding relationship curve of the field angle θ and the pixel height ρ is calculated again between the inner ring and the outer ring, and the curve can be approximately fitted into a straight line by using a least square method; according to the f-theta model, the distortion of the f-theta model of the visual field where the actual use part of the checkerboard calibration plate is located is very small, and the focal length f of the panoramic annular lens can be obtained according to the slope of a straight line; accordingly, θ 1 、θ 2 The angles of view corresponding to the outer and inner rings on the calibration image, respectively, y 1 、y 2 The outer ring and the inner ring on the calibration image correspond to the image height on the image and can be directly measured in the image; rho 1 、ρ 2 The outer ring and the inner ring on the calibration image correspond to the pixel heights on the image plane (namely the radiuses of the outer ring and the inner ring), and the corresponding pixel numbers are n 1 、n 2 Ps is the size of a single pixel on the image surface, and 1000 is the image size from millimeter level to the image surfaceConversion relation of micron size. The focal length fitting line output and displayed by the embodiment is shown in fig. 6.
The conversion module of this embodiment is further configured to calculate a theoretical pixel height at each field angle position according to the angle based on the f- θ model, and obtain an error e at each field angle position according to a ratio of a difference between the actual pixel height and the theoretical pixel height to the theoretical pixel height, that is, a distortion model curve is:
where ρ is the actual pixel height, ρ t Is the theoretical pixel height; rho t ＝f*θ。
Calculating theoretical pixel height rho according to the angle and focal length at each view field angular position t Calibrating according to the size of the checkerboard to obtain the actual pixel height rho; the distortion model curve output and displayed by the present embodiment is shown in fig. 7.
The output display module of this embodiment is configured to output a polynomial fitting relationship curve showing a ray segment height and a pixel height, a corresponding relationship curve showing a field angle and a pixel height, a field angle, a focal length, and a distortion model curve.
Example 2:
the method for detecting the panoramic annular lens parameters in the embodiment is different from the method in the embodiment 1 in that:
only any 1 or any 2 of the field angle, the focal length and the distortion are detected, and the detection method can be determined according to the actual application requirements, so that the corresponding steps of the detection method can be correspondingly deleted, and the requirements of different applications are met;
correspondingly, the detection system of the panoramic annular lens parameters is adjusted adaptively.
The steps of the specific detection method and the construction of the detection system can be referred to in example 1.
The foregoing has outlined rather broadly the preferred embodiments and principles of the present invention and it will be appreciated that those skilled in the art may devise variations of the present invention that are within the spirit and scope of the appended claims.
Claims (10)
1. A method for detecting parameters of a panoramic annular lens is characterized by comprising the following steps:
s1, collecting different calibration images in at least four different areas of a lens view field by using a checkerboard calibration board and a panoramic annular lens; the chessboard grid calibration plate is filled in the field of view between the minimum field of view and the maximum field of view of the panoramic annular lens;
s2, selecting all inner corner points of the checkerboard according to the calibration image to perform calibration calculation to obtain a polynomial fitting relation curve of ray segment height and pixel height; the pixel height is the distance between a point on an image surface of an image sensor of the panoramic annular lens and the center of the image surface, the ray segment height is a Z-direction coordinate value of the point on the image surface in the space where the image surface is located, and the image surface is an XOY plane;
s3, obtaining a corresponding relation curve of the field angle and the pixel height according to the polynomial fitting relation curve of the ray section height and the pixel height and the corresponding relation curve of the ray section height and the field angle;
s4, selecting an effective field of view from the calibration image to obtain the positions of the minimum field of view and the maximum field of view so as to obtain pixel heights corresponding to the positions of the minimum field of view and the maximum field of view respectively;
and S5, matching the corresponding relation curve of the field angle and the pixel height according to the pixel height respectively corresponding to the positions of the minimum field of view and the maximum field of view to obtain the field angle of the panoramic annular lens.
2. The method of claim 1, wherein the center of the image plane of the image sensor of the panoramic annular lens is taken as an origin, the coordinates of the point on the image plane are (u, v), and the height p of the pixel is (p;)
The ray segment height f (rho) is a Z-direction coordinate value of the coordinate point (u, v) in the space of the image surface, namely (u, v, f (rho)) is a three-dimensional point of the space of the image surface, and the equal proportion corresponds to the real object space;
the coordinates at which the three-dimensional point (u, v, f (ρ)) is projected onto the image plane are (u, v).
3. The method for detecting the parameters of the panoramic annular lens according to claim 2, wherein in the step S2, the polynomial fitting relation curve of the ray segment height and the pixel height is:
f(ρ)＝a 0 +a 1 ρ+a 2 ρ 2 +…+a m ρ m
wherein, a 0 、a 1 、a 2 、…、a m Is a fitting coefficient; m is a polynomial degree.
4. The method for detecting the parameters of the panoramic annular lens according to claim 3, wherein in the step S3, the corresponding relationship curve between the ray segment height and the field angle is:
f(ρ)＝ρ*tanθ
where θ is the angle of view.
5. The method for detecting the parameters of the panoramic annular lens according to claim 4, wherein in the step S3, the curve of the correspondence between the field angle and the pixel height is:
6. the method for detecting the parameters of the panoramic annular lens according to claim 5, further comprising the following steps:
step S6, equating the corresponding relation curve of the angle of view and the ray segment height to a linear model, that is, θ ═ k ρ + b, where k and b are the slope and intercept of the linear model respectively;
and then the focal length f of the panoramic annular lens is fitted according to the ratio of the height difference delta y of any two points on the calibrated image on the image to the difference delta theta of the field angle to obtain a focal length fitting line:
wherein, y 1 、y 2 Respectively calibrating the image heights of any two points on the image corresponding to the image; ρ is a unit of a gradient 1 、ρ 2 The pixel heights of any two points on the calibration image on the image surface are respectively corresponding, and the corresponding pixel numbers are respectively n 1 、n 2 Ps is the size of a single pixel on the image plane, and 1000 is the conversion relation from the millimeter level of the image size to the micron level of the image plane size.
7. The method for detecting the parameters of the panoramic annular lens according to claim 6, further comprising the following steps:
s7, calculating the height of a theoretical pixel at each field angle position according to the angle, and obtaining the error e at each field angle position according to the ratio of the difference between the actual pixel height and the theoretical pixel height to the theoretical pixel height, namely the distortion model curve is as follows:
where ρ is the actual pixel height, ρ t Is the theoretical pixel height; rho t ＝f*θ。
8. The method for detecting the parameters of the panoramic annular lens according to claim 7, further comprising:
and outputting a polynomial fitting relation curve of the height of the display ray segment and the height of the pixel, a corresponding relation curve of the field angle and the height of the pixel, a focal length fitting line and a distortion model curve.
9. A system for detecting parameters of a panoramic annular lens, which applies the detection method of claim 1, wherein the system comprises:
the acquisition module is used for acquiring different calibration images in at least four different areas of a lens view field by using the checkerboard calibration plate and the panoramic annular lens; the chessboard grid calibration plate is filled in the field of view between the minimum field of view and the maximum field of view of the panoramic annular lens;
the calibration module is used for selecting all inner corner points of the checkerboard according to the calibration image to perform calibration calculation to obtain a polynomial fitting relation curve of the ray segment height and the pixel height; the pixel height is the distance between a point on an image surface of an image sensor of the panoramic annular lens and the center of the image surface, the ray segment height is a Z-direction coordinate value of the point on the image surface in the space where the image surface is located, and the image surface is an XOY plane;
the conversion module is used for obtaining a corresponding relation curve of the field angle and the pixel height according to the polynomial fitting relation curve of the ray section height and the pixel height and the corresponding relation curve of the ray section height and the field angle;
the calculation module is used for selecting the positions of the minimum view field and the maximum view field corresponding to the effective view field in the calibration image and calculating pixel heights corresponding to the positions of the minimum view field and the maximum view field respectively;
and the matching module is used for matching the corresponding relation curve of the field angle and the pixel height according to the pixel height respectively corresponding to the positions of the minimum field of view and the maximum field of view to obtain the field angle of the panoramic annular lens.
10. The system for detecting the parameters of the panoramic annular lens according to claim 9, further comprising:
and the output display module is used for outputting and displaying a polynomial fitting relation curve of the field angle, the ray section height and the pixel height of the panoramic annular lens and a corresponding relation curve of the field angle and the pixel height.
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