A high-precision calibration method, device and equipment for mapping camera interior orientation elements and a storage medium

Abstract

The application provides a high-precision calibration method, device and equipment for mapping camera interior orientation elements and a storage medium. The method comprises the following steps: firstly, using a collimator and an electronic theodolite to independently calibrate the rotary table angle positioning error and the parallel light tube optical axis pointing deviation, respectively, to generate an error correction model and a space angle matrix, and converting the device system error into a known quantity that can be compensated; secondly, using a positive and negative mirror center-finding method to iteratively converge to determine the accurate intersection point of the sight axis and the target surface as the main point initial observation value and the sight axis reference angle, and eliminating the uncertainty of the main point; finally, starting from the reference angle to perform full field scanning and collection, and jointly substituting the corrected angle data, the angle matrix and the main point observation value into the collinearity condition equation for overall adjustment solution, so that the interior orientation elements and the distortion parameters purely reflecting the characteristics of the camera itself are solved under the premise that various system errors have been stripped one by one.

Description

Technical Field

[0001] This invention relates to the field of calibration of surveying cameras, and particularly to a high-precision calibration method, apparatus, device, and storage medium for orientation elements within a surveying camera. Background Technology

[0002] The calibration of the interior orientation elements of a high-resolution mapping camera is a crucial step in determining its mapping accuracy. The current mainstream method is laboratory calibration based on the precision angle measurement method: the camera is mounted on a high-precision two-axis turntable, and the camera is imaged at infinity points in different directions simulated by collimators by rotating the turntable. The correspondence between the image point coordinates and the angle of the incident light is established, and then the interior orientation elements are solved.

[0003] However, this method faces a core technical challenge in engineering implementation: multiple heterogeneous error sources in the calibration system are coupled together and cannot be effectively separated during the calculation process. This results in the final calibration result being a mixture of camera parameters and equipment system errors, leading to uncontrollable systematic deviations in calibration accuracy. Specifically, the orthogonality deviation and angular positioning error of the turntable axis, the deviation between the actual and nominal angles of the optical axes of each tube in the collimator array, and the uncertainty of the intersection point (i.e., principal point) between the camera's optical axis and the sensor target surface are not independently calibrated and quantified in traditional methods. Instead, they are directly mixed into the parameter calculation process based on the collinearity condition equation as unknown systematic deviations. Since the least squares adjustment algorithm itself cannot distinguish between the residuals from the camera's intrinsic parameters and the systematic deviations from the aforementioned equipment and reference, the calculated principal distance, principal point coordinates, and distortion coefficients essentially absorb the combined effects of all unseparated errors, causing the calibration result to deviate from the camera's true optical characteristics. This error coupling problem has become a fundamental bottleneck restricting further improvement in accuracy under the current sub-micron level calibration accuracy requirements.

[0004] In view of the above, this application is hereby submitted. Summary of the Invention

[0005] This invention discloses a high-precision calibration method, device, equipment, and storage medium for the orientation elements within a mapping camera. It aims to solve the problem that in the existing calibration process of orientation elements within a mapping camera, multiple system errors, such as turntable angle positioning error, collimator optical axis pointing deviation, and uncertainty of the intersection point between the line of sight and the target surface, are not independently calibrated but are coupled and mixed into the camera parameter calculation, resulting in inseparable systematic deviations in the calibration results.

[0006] The first embodiment of the present invention provides a high-precision calibration method for orientation elements within a mapping camera, comprising: Based on the actual rotation angle measurement data collected by the autocollimator at multiple angular positions on the turntable, a turntable angle system error correction model is fitted and generated. Based on the angle measurement data of each optical axis of the collimator array by the electronic theodolite, the spatial angle matrix of the collimator optical axis is calculated and generated. The control turntable drives the camera to face the target collimator, acquires star point images and extracts the coordinates of the star point images of the positive mirror, calls the correction model to correct the current angle reading, obtains the corrected angle value of the positive mirror, controls the turntable to drive the camera to rotate 180° around the azimuth axis, acquires star point images of the same target collimator and extracts the coordinates of the star point images of the reverse mirror, calls the correction model to obtain the corrected angle value of the reverse mirror. The turntable is finely adjusted based on the difference between the star point image coordinates of the upright and inverted mirrors so that the coordinate difference converges to within a preset threshold. The converged image point coordinates are then determined as the initial observation value of the master point, and the converged correction angle value is determined as the reference angle of the line of sight. Using the aforementioned line-of-sight reference angle as the starting reference, the turntable is controlled to step according to the preset angle scanning plan. At each point, star point images are acquired to extract image point coordinates, and the correction model is called to correct the angle readings to obtain the observation dataset. Using the spatial angle matrix of the collimator optical axis, the initial observation value of the principal point, and the observation dataset as input, an overdetermined observation equation set is constructed based on the collinearity condition equation. The least squares global adjustment is performed to solve for the camera's interior orientation elements and distortion parameters.

[0007] Preferably, it further includes: Based on the multi-position orthogonality measurement data between the turntable azimuth axis and pitch axis collected by the autocollimator, the perpendicularity deviation between the two axes is calculated, and the perpendicularity deviation is incorporated into the turntable angle system error correction model.

[0008] Preferably, the extraction of the star point image coordinates adopts the gray-level weighted center of moment algorithm, wherein the gray-level weighted center of moment algorithm performs two-dimensional Gaussian fitting on the gray value of each pixel in the star point spot area, and uses the energy center position obtained by fitting as the sub-pixel level coordinates of the star point.

[0009] Preferably, the angle scanning plan is as follows: with the reference angle of the line of sight as the center, the entire field of view is covered at equal angular intervals of no more than 15 arcminutes along the azimuth and pitch directions, and includes observation points in the large field of view area at the edge of the field of view.

[0010] Preferably, when constructing the overdetermined observation equation set, an adaptive weight coefficient is assigned to each observation equation based on the field of view region where each observation point is located and the signal-to-noise ratio of its star image, wherein the weight of the observation point in the center region of the field of view is higher than the weight of the observation point in the edge region of the field of view.

[0011] Preferably, the interior orientation elements include principal distance and principal point coordinates, and the distortion parameters include radial distortion coefficient and tangential distortion coefficient.

[0012] The second embodiment of the present invention provides a high-precision calibration device for the orientation elements within a mapping camera, comprising: The data acquisition unit is used to fit and generate a turntable angle system error correction model based on the actual rotation angle measurement data collected by the autocollimator at multiple angular positions on the turntable, and to calculate and generate the spatial angle matrix of the collimator optical axis based on the angle measurement data of each optical axis of the collimator array by the electronic theodolite. The correction unit is used to control the turntable to drive the camera to face the target collimator, acquire star point images and extract the coordinates of the positive mirror star point images, call the correction model to correct the current angle reading, obtain the positive mirror correction angle value, control the turntable to drive the camera to rotate 180° around the azimuth axis, acquire star point images of the same target collimator and extract the coordinates of the reverse mirror star point images, and call the correction model to obtain the reverse mirror correction angle value. The line-of-sight reference angle determination unit is used to control the micro-adjustment of the turntable based on the difference between the coordinates of the star point images of the upright and reverse mirrors, so that the coordinate difference converges to within a preset threshold. The converged image point coordinates are determined as the initial observation value of the master point, and the converged correction angle value is determined as the line-of-sight reference angle. The observation dataset acquisition unit is used to control the turntable stepping according to the preset angle scanning plan, using the line-of-sight reference angle as the starting reference, to collect star point images at each point, extract image point coordinates, and call the correction model to correct the angle readings to obtain the observation dataset. The solution unit is used to construct an overdetermined set of observation equations based on the collinearity condition equations, construct the spatial angle matrix of the collimator optical axis, the initial observation value of the principal point and the observation dataset as input, perform least squares global adjustment calculation, and solve for the camera's interior orientation elements and distortion parameters.

[0013] The third embodiment of the present invention provides a high-precision calibration device for the orientation elements within a mapping camera, including a memory and a processor. The memory stores a computer program, which can be executed by the processor to implement the high-precision calibration method for the orientation elements within a mapping camera as described in any of the above embodiments.

[0014] The fourth embodiment of the present invention provides a computer-readable storage medium storing a computer program, which can be executed by the processor of the device where the computer-readable storage medium is located, to implement a high-precision calibration method for the orientation elements of a mapping camera as described in any of the above claims.

[0015] Based on the high-precision calibration method, device, equipment, and storage medium for the interior orientation elements of a mapping camera provided by this invention, the following steps are taken: First, the turntable angle positioning error and the collimator optical axis pointing deviation are independently calibrated using an autocollimator and an electronic theodolite, respectively, to generate an error correction model and a spatial angle matrix, transforming the systematic errors of the equipment into compensable known quantities. Then, the precise intersection point of the line of sight and the target surface is determined by iterative convergence using the upright and reverse mirror centering method, which serves as the initial observation value of the principal point and the reference angle of the line of sight, eliminating the uncertainty of the principal point. Finally, the entire field of view is scanned and acquired starting from this reference angle, and the corrected angle data, the angle matrix, and the principal point observation value are substituted into the collinearity condition equation for overall adjustment and solution. Thus, under the premise that all kinds of systematic errors have been eliminated one by one, the interior orientation elements and distortion parameters that purely reflect the characteristics of the camera itself are solved. Attached Figure Description

[0016] Figure 1 This is a flowchart illustrating a high-precision calibration method for orientation elements within a mapping camera, provided in the first embodiment of the present invention. Figure 2 This is a schematic diagram of a high-precision calibration device for the orientation elements within a mapping camera, provided in the second embodiment of the present invention. Detailed Implementation

[0017] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0018] To better understand the technical solution of the present invention, the embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0019] This invention discloses a high-precision calibration method, device, equipment, and storage medium for the orientation elements within a mapping camera. It aims to solve the problem that in the existing calibration process of orientation elements within a mapping camera, multiple system errors, such as turntable angle positioning error, collimator optical axis pointing deviation, and uncertainty of the intersection point between the line of sight and the target surface, are not independently calibrated but are coupled and mixed into the camera parameter calculation, resulting in inseparable systematic deviations in the calibration results.

[0020] Please see Figure 1 The first embodiment of the present invention provides a high-precision calibration method for the orientation elements within a mapping camera. The hardware includes a high-precision two-axis turntable, whose orientation axis and pitch axis are independently controllable, used to support the camera to be calibrated and perform angle positioning on two rotational degrees of freedom. A collimator array consists of multiple collimators with star-shaped reticles arranged in a preset spatial distribution, used to provide infinity targets in different spatial directions; The autocollimator is used to collect actual rotation angle measurement data and two-axis orthogonality measurement data when the turntable rotates at multiple angular positions. An electronic theodolite is used to collect angle measurement data of the optical axes of each collimator in the collimator array. The data processing unit, which is communicatively connected to both the turntable and the camera to be calibrated, is configured to perform the following steps: S101. Based on the actual rotation angle measurement data collected by the autocollimator at multiple angular positions on the turntable, a turntable angle system error correction model is fitted and generated. Based on the angle measurement data of each optical axis of the collimator array by the electronic theodolite, the spatial angle matrix of the collimator optical axis is calculated and generated. During the system error calibration phase, the data processing unit first performs a full-angle range system error calibration on the high-precision two-axis turntable. Specifically, a standard reflector is mounted on the turntable surface, and an autocollimator is aligned with the reflector. The data processing unit controls the turntable to rotate sequentially to multiple preset angular positions, starting from the zero position of the azimuth axis, with a fixed angular step size. At each position, the autocollimator measures the actual deflection angle of the turntable reflector, and the data processing unit simultaneously reads the angle reading output by the turntable encoder. The two are compared point by point to obtain the positioning deviation value of the azimuth axis at each angular position. Subsequently, the pitch axis is measured in the same way across multiple positions within the full-angle range to obtain the positioning deviation value of the pitch axis at each angular position. The data processing unit uses all the deviation data of the above two axes as sample points and establishes angle system error correction models for the azimuth and pitch axes respectively using polynomial fitting. This allows the encoder readings to be interpolated and corrected in real time using the model when the turntable moves to any angular position during subsequent calibration, obtaining angular data closer to the true value.

[0021] After calibrating the independent angular positioning errors of each axis, the data processing unit further calibrates the orthogonality deviation between the two axes of the turntable. The autocollimator maintains its aiming state towards the turntable's reflector, and the data processing unit controls the turntable to rotate to multiple different positions on the azimuth axis. At each azimuth position, the pitch axis is driven to rotate slightly in both directions. The autocollimator records the horizontal and vertical offsets of the reflected beam during the pitch axis rotation. If the azimuth and pitch axes are strictly orthogonal, the pitch axis rotation only causes a vertical beam offset, while the horizontal offset should remain unchanged. By analyzing the horizontal coupling offset caused by the pitch axis rotation at multiple azimuth positions, the data processing unit calculates the verticality deviation angle between the two axes and incorporates this deviation angle as a coupling compensation term into the aforementioned turntable angle system error correction model. This ensures that when the two axes of the turntable move in tandem, the angular coupling error caused by the orthogonality deviation can be synchronously compensated, thus completing the establishment of the turntable system error correction model.

[0022] After the turntable error calibration is completed, the data processing unit receives the angle measurement data obtained by the electronic theodolite through precise angle measurement of the optical axes of each collimator in the array, and calculates and generates a spatial angle matrix of the collimator optical axes. Specifically, the electronic theodolite is set up at an appropriate position in front of the array, and the operator aims at the output optical axis direction of each collimator in the array one by one in a multi-round manner. Each aiming uses the average of the readings from both the upright and inverted positions to eliminate the theodolite's own line-of-sight error and horizontal axis tilt error, obtaining the azimuth and elevation angle observation values ​​of the optical axis of each collimator in the theodolite coordinate system. After receiving all the above angle measurement data, the data processing unit uses the optical axis direction of a certain collimator in the array as the reference direction, and calculates the spatial angle between the optical axes of the remaining optical tubes and the reference optical axis one by one, constructing a complete spatial angle matrix of the collimator optical axes. Each element in this matrix represents the angular deviation of the corresponding optical axis of the light tube relative to the reference optical axis in both the azimuth and elevation directions. Its accuracy depends on the angle measurement accuracy of the electronic theodolite and the redundancy of multiple observations. After averaging multiple observations, an accuracy level better than 1 arcsecond can be achieved. This angle matrix is ​​stored as a known true value in the data processing unit. In the subsequent full-field adjustment calculation stage, it participates in the construction of the observation equations together with the angle values ​​corrected by the turntable, providing accurate spatial angle input conditions for high-precision solution of the azimuth elements within the camera.

[0023] S102, control the turntable to drive the camera to face the target collimator, acquire star point images and extract the star point image coordinates of the positive mirror, call the correction model to correct the current angle reading, obtain the positive mirror correction angle value, control the turntable to drive the camera to rotate 180° around the azimuth axis, acquire star point images of the same target collimator and extract the star point image coordinates of the reverse mirror, call the correction model to obtain the reverse mirror correction angle value. After completing the system error calibration and obtaining the turntable angle system error correction model and the collimator optical axis spatial angle matrix, the precise measurement stage of the intersection point between the line of sight and the target surface begins. The mapping camera to be calibrated, having undergone optomechanical adjustment, is rigidly mounted on the turntable's support platform using a special fixture, ensuring no relative displacement between the camera and the turntable. The data processing unit controls the turntable's coordinated movement along the azimuth and pitch axes, driving the camera to approximately face a pre-selected target collimator in the collimator array. This target collimator is typically chosen as the one with the largest aperture and located at the center of the array to ensure the signal-to-noise ratio and image quality of the star point imaging. Once the camera's line of sight is approximately aligned with the target collimator, the parallel beam of light simulating an infinity target emitted by that collimator is converged by the camera's optical system, forming a star point spot on the sensor target surface. The data processing unit synchronously triggers camera exposure, captures the star image in real time through the image acquisition card, and synchronously reads the angle readings output by the azimuth and pitch axis encoders of the turntable at this time. It calls the established turntable angle system error correction model to correct and compensate the angle reading, and obtains the corrected high-precision angle value under the positive mirror state, that is, the positive mirror corrected angle value.

[0024] Subsequently, the data processing unit performs precise extraction of image point coordinates from the acquired star point images. The extraction process employs a gray-level weighted centroid algorithm to achieve sub-pixel-level localization. Specifically, the data processing unit first detects and defines the pixel region containing the star point spot in the star point image, reads the gray-level value of each pixel within this region, and then uses a two-dimensional Gaussian function as a fitting model to perform least-squares fitting on the pixel gray-level distribution within the spot region. This yields the two-dimensional plane coordinates corresponding to the peak value of the Gaussian function, which represent the sub-pixel-level position of the star point spot's energy center. This localization accuracy is significantly superior to simple pixel-level centroid calculation methods. The data processing unit records these coordinates as the image coordinates of the positive mirror star point.

[0025] After completing the upright mirror measurement, the data processing unit controls the turntable to rotate the camera 180 degrees around the azimuth axis. After the rotation, the camera's line of sight deflects in the opposite direction in the horizontal plane. However, since the turntable's pitch axis has not been adjusted, the camera can still receive the parallel beam emitted by the same target collimator and form a star image on the target surface. The data processing unit triggers the camera to expose again, capturing the star image at this time. Simultaneously, it reads the azimuth and pitch axis angle readings of the turntable at the current position and calls the turntable angle system error correction model to correct these readings, obtaining the corrected angle value in the inverted mirror state, i.e., the inverted mirror correction angle value. The data processing unit also performs the above-mentioned gray-scale weighted moment center algorithm on this star image to extract the sub-pixel level coordinates of the star spot energy center and records them as the coordinates of the inverted mirror star image. If the optical line of sight of the camera does not strictly coincide with the rotation center of the turntable after the camera rotates 180 degrees around the azimuth axis, or if there is a geometric deviation between the line of sight and the sensor target surface, then the position of the star point image formed by the two measurements of the upright and inverted mirrors on the target surface will produce an observable deviation. This deviation directly reflects the uncertainty of the intersection point of the line of sight and the target surface, providing a key observation basis for the subsequent accurate determination of the principal point through iterative convergence.

[0026] S103, control the turntable to make fine adjustments based on the difference between the star point image coordinates of the upright and inverted mirrors so that the coordinate difference converges to within the preset threshold, determine the converged image point coordinates as the initial observation value of the main point, and determine the converged correction angle value as the line-of-sight reference angle. After obtaining the coordinates of the star image from the upright and inverted mirrors, the data processing unit calculates the coordinate differences between them in the row and column directions on the target surface. The physical meaning of this coordinate difference is that if the camera's optical axis of view is strictly aligned with the rotation center of the turntable's azimuth axis, then before and after the camera rotates 180 degrees around the azimuth axis, the star image from the same collimator should fall at the same position on the target surface; that is, the coordinates of the upright and inverted mirror star images are completely consistent. Conversely, if there is a deviation, it indicates a geometric misalignment between the optical axis of view and the rotation center. Half of this offset is the deviation component of the optical axis of view relative to the turntable's rotation center in the corresponding direction. Based on the aforementioned geometric relationship, the data processing unit converts half of the difference between the star point image coordinates of the upright and inverted mirrors into the required angular fine-tuning amount for the azimuth and pitch axes of the turntable (for example, "converting the image plane coordinate deviation into the corresponding angular deviation amount based on the nominal values ​​of the camera's pixel size and principal distance"), and sends a micro-motion command to the turntable motion controller to drive the turntable to perform corresponding small-angle correction rotations on the azimuth and pitch axes to compensate for the alignment deviation between the line of sight and the rotation center.

[0027] After the fine-tuning is completed, the data processing unit controls the turntable again to execute the complete process of orthogonal and inverted mirror measurement. Specifically, it acquires a star image at the current position, extracts the star image coordinates of the orthogonal mirror, and obtains the orthogonal mirror correction angle value. Then, it controls the turntable to rotate 180 degrees around the azimuth axis, acquires a star image, extracts the star image coordinates of the inverted mirror, and obtains the inverted mirror correction angle value. The difference between the two image coordinates is recalculated. If the coordinate difference is still greater than a preset threshold, the data processing unit continues to calculate a new fine-tuning amount using the above method and drives the turntable to perform further fine-tuning corrections. This process is repeated iteratively, with the difference between the orthogonal and inverted mirror star image coordinates gradually decreasing in each iteration until the coordinate difference converges to within a preset threshold in both the row and column directions of the target surface. In this embodiment, this preset threshold is set to be no greater than 0.1 pixels.

[0028] Once the iteration convergence condition is met, the data processing unit determines that the camera's optical line of sight has passed through the rotation center of the turntable's azimuth axis, and the imaging positions of the star images on the target surface in both upright and inverted mirror states are completely coincident within the measurement accuracy range. At this point, the data processing unit determines the star image coordinates extracted in the last iteration as the initial observation value of the principal point, which is the precise intersection point of the camera's optical line of sight and the sensor target surface in the image plane coordinate system. Simultaneously, the data processing unit determines the turntable angle value corrected by the turntable angle system error correction model in the last iteration as the reference angle of the line of sight, which characterizes the precise pointing of the camera's line of sight in the calibration system's spatial coordinate system. The data processing unit stores the initial observation value of the principal point and the reference angle of the line of sight for subsequent full-field data acquisition and overall adjustment calculation stages. This method, through the principle of geometric symmetry, transforms the determination of the principal point from an absolute measurement relying on an external reference to a relative alignment process based on the internal consistency of the upright and inverted mirrors, giving the determination of the principal point a clear physical basis and a self-verifiable convergence criterion, significantly improving the objectivity and accuracy of the principal point determination.

[0029] S104, using the line-of-sight reference angle as the starting reference, control the turntable to step according to the preset angle scanning plan, collect star point images at each point to extract image point coordinates, and call the correction model to correct the angle readings to obtain the observation dataset; After accurately determining the initial observation value of the principal point and the reference angle of the line of sight, the camera is restored to the positive mirror state, and the automatic data acquisition stage of the entire field of view begins. The data processing unit uses the reference angle of the line of sight determined and stored in the previous stage as the starting reference and coordinate origin for angle scanning, and generates a point sequence covering the entire effective field of view of the camera to be calibrated according to the preset angle scanning plan. This angle scanning plan starts from the center of the field of view corresponding to the reference angle of the line of sight, and expands symmetrically to both sides along the azimuth and elevation directions, gradually extending to the edge of the field of view at equal angular intervals of no more than 15 arcminutes, ensuring that the scanning grid uniformly covers the entire area from the center of the field of view to the edge of the field of view. Taking a linear pushbroom mapping camera using TDICCD as an example, if the full field of view angle of the camera in the vertical direction is a certain number of degrees, the scanning plan extends along this direction from the position of the maximum negative field of view angle corresponding to one end of the target surface to the position of the maximum positive field of view angle corresponding to the other end. Multiple rows of scanning points are also set at equal angular intervals along the flight direction, thus forming a two-dimensional angle grid that is regularly distributed in the azimuth and elevation dimensions. The plan mandates that large field-of-view areas at the edge of the field of view be included in the scanning range, ensuring that the entire observation scheme contains a sufficient number of large-angle observation points. These large field-of-view observation data play a crucial role in the effective constraint of principal distance and the reliable calculation of higher-order distortion parameters, avoiding the problem of insufficient principal distance constraint caused by the simplification or omission of large-angle area measurements in traditional methods.

[0030] After generating a complete list of angle points according to the above plan, the data processing unit automatically initiates a point-by-point data acquisition process. At each preset angle point, the data processing unit sends a target angle command to the turntable motion controller. The turntable moves in tandem along the azimuth and pitch axes, precisely positioning the camera at that angle, aligning the camera's line of sight with the collimator in the collimator array corresponding to the current angle position. Once the turntable is in position and stable, the data processing unit synchronously triggers camera exposure, capturing the star image of the current point in real time via the image acquisition card. It then performs a grayscale weighted center-of-magnitude algorithm on the image to extract the sub-pixel coordinates of the star spot energy center as the image point coordinates for that point. Simultaneously, the data processing unit reads the angle readings output by the turntable's azimuth and pitch axis encoders at the current point, calls the established and stored turntable angle system error correction model to correct and compensate for these readings in real time, obtaining the corrected high-precision true angle value for that point. The data processing unit binds and stores the extracted image point coordinates and corresponding corrected angle values ​​for each point, forming a complete observation record.

[0031] The above acquisition process is automatically executed one by one along the preset list of angle points without manual intervention. The turntable steps to the next angle position in sequence, repeating the synchronous operations of image acquisition, image point coordinate extraction, and angle reading correction until all preset points covering the entire field of view have been acquired. The observation records of all points are summarized to form a complete observation dataset. Each record in this dataset contains the sub-pixel-level image point coordinates of the corresponding point and the true angle value of the turntable after systematic error correction. This provides high-quality input data with uniform spatial distribution, sufficient angle coverage, and pre-compensated errors for subsequent overall adjustment calculations based on the collinearity condition equation.

[0032] S105, using the spatial angle matrix of the collimator optical axis, the initial observation value of the principal point, and the observation dataset as input, construct an overdetermined observation equation set based on the collinearity condition equation, perform least squares global adjustment, and solve for the camera's interior orientation elements and distortion parameters.

[0033] After the full-field observation dataset is acquired, the data processing unit enters the intrinsic parameter weighted optimization solution stage. It gathers all the calibration data generated and stored in the previous stages and uniformly substitutes them into the camera's rigorous geometric imaging model for overall solution. Specifically, the data processing unit reads the collimator optical axis spatial angle matrix generated in the system error calibration stage, the initial observation values ​​of the principal points obtained in the stage of determining the intersection of the line of sight and the target surface, and the observation dataset formed in the full-field acquisition stage, which includes sub-pixel level image point coordinates and corrected turntable true angle values ​​for each point. All three are used as input conditions for the solution.

[0034] For each observation point in the observation dataset, the data processing unit establishes an observation equation for that point based on the photogrammetric collinearity condition equation. The collinearity condition equation describes the geometric constraint relationship of collinearity between the target point, the camera projection center, and the corresponding image point on the image plane in object space. The equation includes the camera interior orientation elements and distortion parameters to be solved. Specifically, the spatial direction of the incident light ray at each observation point is determined by the direction of the collimator's optical axis corresponding to that point. This direction is calculated by combining the angle deviation of the collimator relative to the reference collimator recorded in the collimator's optical axis spatial angle matrix with the corrected true angle value of the turntable at that point. This ensures that the installation deviation of the collimator and the positioning error of the turntable are introduced into the equation as known quantities, rather than being mixed into the parameters to be solved. Regarding image point coordinates, each observation equation directly uses the sub-pixel level coordinate values ​​extracted by the gray-scale weighted moment center algorithm for the corresponding point. The principal point coordinates are used as the initial approximate values ​​of the principal point obtained during the determination of the intersection of the line of sight and the target plane, participating in the iterative calculation. Since the number of observation points in the observation dataset is far greater than the number of unknown parameters to be solved, all the observation equations form an overdetermined system of equations.

[0035] When constructing this overdetermined observation equation set, the data processing unit does not apply equal constraints to all observation equations. Instead, it assigns an adaptive weight coefficient to each equation based on the location of each observation point within the field of view and the signal-to-noise ratio (SNR) characteristics of its star image. Since the imaging quality of the camera's optical system in the central region of the field of view is typically better than in the edge regions, the energy concentration of star spots is higher, and the accuracy of the image point coordinates extracted by the gray-scale weighted moment center algorithm is correspondingly higher. Therefore, the data processing unit assigns larger weight coefficients to observation points located in the central region of the field of view with high SNR star images, enabling these high-precision observation data to play a stronger role in parameter constraints in the overall solution. While observation points in the edge regions of the field of view have relatively lower weights, they still have irreplaceable geometric contributions to the solution of principal distance constraints and higher-order distortion parameters. Therefore, they are also retained in the equation set to ensure the consistency and integrity of the solution results across the entire field of view.

[0036] The data processing unit iteratively solves the aforementioned weighted overdetermined observation equations using a least-squares global adjustment algorithm. In each iteration, the algorithm calculates the residuals of each observation equation based on the current parameter estimates, constructs normal equations according to the weight coefficients of each equation, solves for parameter corrections, and updates the parameter estimates. This process is repeated iteratively until the parameter corrections converge to within the set accuracy. Finally, the data processing unit obtains all interior orientation elements and distortion parameters of the camera to be calibrated in one solution. The interior orientation elements include principal distance and principal point coordinates. The principal distance represents the vertical distance from the projection center of the camera's optical system to the image plane, and the principal point coordinates represent the precise position of the intersection of the optical axis and the sensor target surface in the image plane coordinate system. The distortion parameters include radial distortion coefficients and tangential distortion coefficients. The radial distortion coefficients describe the displacement of the image point along the radial direction caused by the rotational symmetry defects of the optical system, while the tangential distortion coefficients describe the displacement of the image point in the tangential direction caused by the eccentricity and tilt of optical elements. Since all input data involved in the calculation have undergone independent calibration and compensation of systematic errors in the preceding stage, the calculated interior orientation elements and distortion parameters purely reflect the optical imaging characteristics of the camera itself, no longer mixed with the influence of equipment systematic errors, and the calibration accuracy and result reliability are fully guaranteed.

[0037] Please see Figure 2 The second embodiment of the present invention provides a high-precision calibration device for the orientation elements within a mapping camera, comprising: The data acquisition unit 201 is used to fit and generate a turntable angle system error correction model based on the actual rotation angle measurement data collected by the autocollimator at multiple angular positions on the turntable, and to calculate and generate the spatial angle matrix of the collimator optical axis based on the angle measurement data of each optical axis of the collimator array by the electronic theodolite. Correction unit 202 is used to control the turntable to drive the camera to face the target collimator, acquire star point images and extract the coordinates of the star point image of the positive mirror, call the correction model to correct the current angle reading, obtain the corrected angle value of the positive mirror, control the turntable to drive the camera to rotate 180° around the azimuth axis, acquire star point images of the same target collimator and extract the coordinates of the star point image of the reverse mirror, and call the correction model to obtain the corrected angle value of the reverse mirror. The line-of-sight reference angle determination unit 203 is used to control the micro-motion adjustment of the turntable based on the difference between the coordinates of the star point images of the upright and reverse mirrors, so that the coordinate difference converges to within a preset threshold, the converged image point coordinates are determined as the initial observation value of the master point, and the converged correction angle value is determined as the line-of-sight reference angle. The observation dataset acquisition unit 204 is used to control the turntable to step according to the preset angle scanning plan, take the line of sight reference angle as the starting reference, collect star point images at each point to extract image point coordinates, and call the correction model to correct the angle readings to obtain the observation dataset. The solver unit 205 is used to construct an overdetermined set of observation equations based on the collinearity condition equations, take the collimator optical axis spatial angle matrix, the initial observation value of the principal point and the observation dataset as input, perform least squares global adjustment calculation, and solve for the camera's interior orientation elements and distortion parameters.

[0038] The third embodiment of the present invention provides a high-precision calibration device for the orientation elements within a mapping camera, including a memory and a processor. The memory stores a computer program, which can be executed by the processor to implement the high-precision calibration method for the orientation elements within a mapping camera as described in any of the above embodiments.

[0039] The fourth embodiment of the present invention provides a computer-readable storage medium storing a computer program, which can be executed by the processor of the device where the computer-readable storage medium is located, to implement a high-precision calibration method for the orientation elements of a mapping camera as described in any of the above claims.

[0040] Based on the high-precision calibration method, device, equipment, and storage medium for the interior orientation elements of a mapping camera provided by this invention, the following steps are taken: First, the turntable angle positioning error and the collimator optical axis pointing deviation are independently calibrated using an autocollimator and an electronic theodolite, respectively, to generate an error correction model and a spatial angle matrix, transforming the systematic errors of the equipment into compensable known quantities. Then, the precise intersection point of the line of sight and the target surface is determined by iterative convergence using the upright and reverse mirror centering method, which serves as the initial observation value of the principal point and the reference angle of the line of sight, eliminating the uncertainty of the principal point. Finally, the entire field of view is scanned and acquired starting from this reference angle, and the corrected angle data, the angle matrix, and the principal point observation value are substituted into the collinearity condition equation for overall adjustment and solution. Thus, under the premise that all kinds of systematic errors have been eliminated one by one, the interior orientation elements and distortion parameters that purely reflect the characteristics of the camera itself are solved.

[0041] Exemplary examples show that the computer program described in the third and fourth embodiments of the present invention can be divided into one or more modules, which are stored in the memory and executed by the processor to complete the present invention. The one or more modules can be a series of computer program instruction segments capable of performing specific functions, which describe the execution process of the computer program in a high-precision calibration device for mapping camera orientation elements. For example, the apparatus described in the second embodiment of the present invention.

[0042] The processor can be a Central Processing Unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The general-purpose processor can be a microprocessor or any conventional processor. This processor is the control center of the high-precision calibration method for the orientation elements within a mapping camera, connecting various parts of the method for assisting a pure electric vehicle downhill using various interfaces and lines.

[0043] The memory can be used to store the computer program and / or modules. The processor, by running or executing the computer program and / or modules stored in the memory, and by calling the data stored in the memory, implements various functions of a high-precision calibration method for orientation elements within a mapping camera. The memory may mainly include a program storage area and a data storage area. The program storage area may store the operating system, at least one application program required for a function (such as sound playback function, text conversion function, etc.), etc.; the data storage area may store data created based on the use of the mobile phone (such as audio data, text message data, etc.). In addition, the memory may include high-speed random access memory, and may also include non-volatile memory, such as hard disk, memory, plug-in hard disk, smart media card (SMC), secure digital (SD) card, flash card, at least one disk storage device, flash memory device, or other volatile solid-state storage device.

[0044] If the implemented module is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, all or part of the processes in the above embodiments of the present invention can also be implemented by a computer program instructing related hardware. The computer program can be stored in a computer-readable storage medium, and when executed by a processor, it can implement the steps of the various method embodiments described above. The computer program includes computer program code, which can be in the form of source code, object code, executable files, or certain intermediate forms. The computer-readable medium can include: any entity or device capable of carrying the computer program code, recording media, USB flash drives, portable hard drives, magnetic disks, optical disks, computer memory, read-only memory (ROM), random access memory (RAM), electrical carrier signals, telecommunication signals, and software distribution media, etc. It should be noted that the content included in the computer-readable medium can be appropriately added or removed according to the requirements of legislation and patent practice in the jurisdiction. For example, in some jurisdictions, according to legislation and patent practice, computer-readable media do not include electrical carrier signals and telecommunication signals.

[0045] It should be noted that the device embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate, and the components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs. Furthermore, in the accompanying drawings of the device embodiments provided by this invention, the connection relationships between modules indicate that they have communication connections, which can be specifically implemented as one or more communication buses or signal lines. Those skilled in the art can understand and implement this without any creative effort.

[0046] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A high-precision calibration method for orientation elements within a mapping camera, characterized in that, include: Based on the actual rotation angle measurement data collected by the autocollimator at multiple angular positions on the turntable, a turntable angle system error correction model is fitted and generated. Based on the angle measurement data of each optical axis of the collimator array by the electronic theodolite, the spatial angle matrix of the collimator optical axis is calculated and generated. The control turntable drives the camera to face the target collimator, acquires star point images and extracts the coordinates of the star point images of the positive mirror, calls the correction model to correct the current angle reading, obtains the corrected angle value of the positive mirror, controls the turntable to drive the camera to rotate 180° around the azimuth axis, acquires star point images of the same target collimator and extracts the coordinates of the star point images of the reverse mirror, calls the correction model to obtain the corrected angle value of the reverse mirror. The turntable is finely adjusted based on the difference between the star point image coordinates of the upright and inverted mirrors so that the coordinate difference converges to within a preset threshold. The converged image point coordinates are then determined as the initial observation value of the master point, and the converged correction angle value is determined as the reference angle of the line of sight. Using the aforementioned line-of-sight reference angle as the starting reference, the turntable is controlled to step according to the preset angle scanning plan. At each point, star point images are acquired to extract image point coordinates, and the correction model is called to correct the angle readings to obtain the observation dataset. Using the spatial angle matrix of the collimator optical axis, the initial observation value of the principal point, and the observation dataset as input, an overdetermined observation equation set is constructed based on the collinearity condition equation. The least squares global adjustment is performed to solve for the camera's interior orientation elements and distortion parameters.

2. The high-precision calibration method for the orientation elements within a mapping camera according to claim 1, characterized in that, Also includes: Based on the multi-position orthogonality measurement data between the turntable azimuth axis and pitch axis collected by the autocollimator, the perpendicularity deviation between the two axes is calculated, and the perpendicularity deviation is incorporated into the turntable angle system error correction model.

3. The high-precision calibration method for the orientation elements within a mapping camera according to claim 1, characterized in that, The extraction of star point image coordinates adopts the gray-level weighted center of moment algorithm, wherein the gray-level weighted center of moment algorithm performs two-dimensional Gaussian fitting on the gray value of each pixel in the star point spot area, and uses the energy center position obtained by fitting as the sub-pixel level coordinates of the star point.

4. The high-precision calibration method for the orientation elements within a mapping camera according to claim 1, characterized in that, The angle scanning plan is as follows: with the reference angle of the line of sight as the center, the entire field of view is covered at equal angular intervals of no more than 15 arcminutes along the azimuth and pitch directions, and includes observation points in the large field of view area at the edge of the field of view.

5. The high-precision calibration method for the orientation elements within a mapping camera according to claim 1, characterized in that, When constructing the overdetermined observation equation set, an adaptive weight coefficient is assigned to each observation equation based on the field of view region where each observation point is located and the signal-to-noise ratio of its star image. The weight of observation points in the center region of the field of view is higher than that of observation points in the edge region of the field of view.

6. The high-precision calibration method for the orientation elements within a mapping camera according to claim 1, characterized in that, The interior orientation elements include principal distance and principal point coordinates, and the distortion parameters include radial distortion coefficient and tangential distortion coefficient.

7. A high-precision calibration device for orientation elements within a mapping camera, characterized in that, include: The data acquisition unit is used to fit and generate a turntable angle system error correction model based on the actual rotation angle measurement data collected by the autocollimator at multiple angular positions on the turntable, and to calculate and generate the spatial angle matrix of the collimator optical axis based on the angle measurement data of each optical axis of the collimator array by the electronic theodolite. The correction unit is used to control the turntable to drive the camera to face the target collimator, acquire star point images and extract the coordinates of the positive mirror star point images, call the correction model to correct the current angle reading, obtain the positive mirror correction angle value, control the turntable to drive the camera to rotate 180° around the azimuth axis, acquire star point images of the same target collimator and extract the coordinates of the reverse mirror star point images, and call the correction model to obtain the reverse mirror correction angle value. The line-of-sight reference angle determination unit is used to control the micro-adjustment of the turntable based on the difference between the coordinates of the star point images of the upright and reverse mirrors, so that the coordinate difference converges to within a preset threshold. The converged image point coordinates are determined as the initial observation value of the master point, and the converged correction angle value is determined as the line-of-sight reference angle. The observation dataset acquisition unit is used to control the turntable stepping according to the preset angle scanning plan, using the line-of-sight reference angle as the starting reference, to collect star point images at each point, extract image point coordinates, and call the correction model to correct the angle readings to obtain the observation dataset. The solution unit is used to construct an overdetermined set of observation equations based on the collinearity condition equations, construct the spatial angle matrix of the collimator optical axis, the initial observation value of the principal point and the observation dataset as input, perform least squares global adjustment calculation, and solve for the camera's interior orientation elements and distortion parameters.

8. A high-precision calibration device for the orientation elements within a mapping camera, characterized in that, The system includes a memory and a processor. The memory stores a computer program that can be executed by the processor to implement a high-precision calibration method for orientation elements within a mapping camera as described in any one of claims 1 to 6.

9. A computer-readable storage medium, characterized in that, The device contains a computer program that can be executed by a processor of the device on which the computer-readable storage medium is located, to implement a high-precision calibration method for orientation elements within a mapping camera as described in any one of claims 1 to 6.

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