CN112288822B - Camera active alignment method combined with calibration - Google Patents
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- CN112288822B CN112288822B CN202011004423.2A CN202011004423A CN112288822B CN 112288822 B CN112288822 B CN 112288822B CN 202011004423 A CN202011004423 A CN 202011004423A CN 112288822 B CN112288822 B CN 112288822B
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- 238000000034 method Methods 0.000 title claims abstract description 22
- 238000012360 testing method Methods 0.000 claims abstract description 75
- 230000002093 peripheral effect Effects 0.000 claims abstract description 11
- 238000003384 imaging method Methods 0.000 claims description 14
- 238000012937 correction Methods 0.000 claims description 6
- 239000011521 glass Substances 0.000 claims description 4
- 239000003292 glue Substances 0.000 claims description 4
- 238000005530 etching Methods 0.000 claims description 3
- 230000003287 optical effect Effects 0.000 description 3
- 238000001723 curing Methods 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 230000000007 visual effect Effects 0.000 description 2
- 241001237160 Kallima inachus Species 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000004364 calculation method Methods 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 238000001029 thermal curing Methods 0.000 description 1
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
- G06T7/00—Image analysis
- G06T7/80—Analysis of captured images to determine intrinsic or extrinsic camera parameters, i.e. camera calibration
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
- G06T2207/00—Indexing scheme for image analysis or image enhancement
- G06T2207/10—Image acquisition modality
- G06T2207/10016—Video; Image sequence
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Abstract
The invention discloses a camera active alignment method combined with calibration, which comprises the following steps: providing a test chart card; acquiring image information of a test image card through a camera, determining the position of a central view field test pattern, and moving a lens or an image sensor until the corner point of the central view field test pattern is positioned at the center of the image; obtaining definition change curves of a central view field test pattern and a plurality of peripheral view field test patterns through scanning of a camera in the focal length direction, calculating the inclination angle of a lens and an image sensor according to the definition change curves, and adjusting the parallelism of the lens and the image sensor; and marking a distortion center of the camera through a checkerboard, and adjusting the relative horizontal position of the lens and the image sensor according to the difference between the distortion center and the image center so as to correct the deviation. The active alignment method of the camera combined with calibration can greatly improve the center deviation of the long-focus camera, so that the center of the internal reference of the camera is closer to the center of the image, and the alignment precision is greatly improved.
Description
Technical Field
The invention relates to the technical field of active alignment of cameras, in particular to a camera active alignment method combined with calibration.
Background
With the development of intelligent auxiliary driving, automatic driving and other technologies in the automobile industry, the camera is one of the main vehicle-mounted sensors, and the application field of the camera is also wider and wider. Especially, the front-view camera can be used for ranging, anti-collision and the like, has long focal length and higher requirements on parameters of the camera, and otherwise, the calculation accuracy is reduced.
The traditional active alignment algorithm of the camera uses the imaging position of the test pattern corner of the central area to determine the horizontal positions of the lens and the image sensor, and the method is considered to be optimal when the central test pattern is imaged on the image center, and is feasible for cameras with shorter focal length (such as a look-around camera), but is not applicable for cameras with long focus. In the case of the same inclination of the optical axis, the increase of the focal length of the lens causes the deviation of the center of the camera to increase proportionally. If the camera is aligned in a conventional manner, the center marked by the produced camera may deviate from the center of the image by tens of pixels. In practical experience, a camera with a focal length of around 16mm may deviate by more than fifty pixels.
Disclosure of Invention
The invention aims to provide a camera active alignment method combining calibration, which has high feasibility and high alignment precision.
In order to solve the above problems, the present invention provides a camera active alignment method combined with calibration, which includes:
Providing a test chart card, wherein the test chart card is integrated with a checkerboard, a central view field test pattern and a plurality of peripheral view field test patterns, the central view field test pattern is embedded in the checkerboard, and corner points are coincident with the corner points of the checkerboard;
acquiring image information of the test pattern card through a camera, determining the position of the central view field test pattern, and moving a lens or an image sensor until the corner point of the central view field test pattern is positioned at the center of the image;
Obtaining definition change curves of the central view field test pattern and the plurality of peripheral view field test patterns through scanning of the camera in the focal length direction, calculating the inclination angle of the lens and the image sensor according to the definition change curves, and adjusting the parallelism of the lens and the image sensor;
And marking a distortion center of the camera through the checkerboard, and adjusting the relative horizontal position of the lens and the image sensor according to the difference between the distortion center and the image center so as to correct the deviation.
As a further improvement of the present invention, the marking the distortion center of the camera through the checkerboard, and adjusting the relative horizontal position of the lens and the image sensor according to the difference between the distortion center and the image center, further includes: and determining a correction result through recalibration, and if the deviation does not meet the requirement, continuing correction.
As a further improvement of the present invention, the marking the distortion center of the camera through the checkerboard, and adjusting the relative horizontal position of the lens and the image sensor according to the difference between the distortion center and the image center, further includes: the positions of the lens and the image sensor are determined by glue curing.
As a further improvement of the present invention, the distortion center of the camera is marked by the checkerboard, specifically including: and calibrating the distortion center of the camera by utilizing the relationship of epipolar geometry by utilizing the characteristic that an image obtained by imaging the checkerboard in an ideal small hole is parallel to the actual imaging of the checkerboard.
As a further improvement of the invention, the calibration of the distortion center of the camera by utilizing the relation of epipolar geometry specifically comprises the following steps: and determining the distortion center of the camera through the epipolar point determined by the image obtained by the checkerboard after the ideal pinhole imaging and the actual imaging of the checkerboard.
As a further improvement of the present invention, the test chart is film printing or glass etching.
As a further improvement of the invention, the film printed test chart card is attached or pressed on a flat bearing surface.
As a further improvement of the present invention, the test chart is transmissive or reflective.
As a further improvement of the present invention, the central field of view test pattern and the plurality of peripheral field of view test patterns are each a black naked sword side inclined by 5 degrees, including both horizontal and vertical directions, based on the ISO12233 standard.
As a further improvement of the present invention, each of the checkerboards is square, and the number of the checkers is 4x4 or more between the black and white in the transverse direction and the longitudinal direction.
The invention has the beneficial effects that:
the active alignment method of the camera combined with calibration can greatly improve the center deviation of the long-focus camera, so that the center of the internal reference of the camera is closer to the center of the image, and the alignment precision is greatly improved.
The foregoing description is only an overview of the present invention, and is intended to be implemented in accordance with the teachings of the present invention, as well as the preferred embodiments thereof, together with the following detailed description of the invention, given by way of illustration only, together with the accompanying drawings.
Drawings
FIG. 1 is a flow chart of a camera active alignment method in combination with calibration in a preferred embodiment of the invention;
FIG. 2 is a schematic diagram of a test card according to a preferred embodiment of the present invention;
fig. 3 is a schematic diagram of a test card according to a preferred embodiment of the invention.
Detailed Description
The present invention will be further described with reference to the accompanying drawings and specific examples, which are not intended to be limiting, so that those skilled in the art will better understand the invention and practice it.
As shown in fig. 1, the method for actively aligning a camera in combination with calibration in a preferred embodiment of the present invention includes the following steps:
S10, providing a test chart card, wherein the test chart card is integrated with a checkerboard, a central view field test pattern and a plurality of peripheral view field test patterns, the central view field test pattern is embedded in the checkerboard, and corner points are coincident with the corner points of the checkerboard.
As shown in fig. 2 and 3, in the preferred embodiment of the present invention, in fig. 2, the black grids in the checkerboard of the test chart are all full, two white circles are added in the diagonal black grids beside the central view field test pattern, and the software can locate the corner point of the central view field test pattern by identifying the two circles. In fig. 3, the black grids in the checkerboard of the test chart card are all hollow structures, only a circle of narrower black edges are left, the test chart card does not influence the search of corner points of the checkerboard in the calibration algorithm, but the active alignment algorithm does not recognize the corner points of the checkerboard, and the position recognition error of the central visual field test pattern can be avoided.
Preferably, the test chart card is film printing, glass etching or the like. The film printed test chart card is attached or pressed on a flat bearing surface. The bearing surface may be glass or the like.
In this embodiment, the test card is transmissive or reflective.
In this embodiment, the central field of view test pattern and the plurality of peripheral field of view test patterns are each a black naked sword side inclined by 5 degrees, including both horizontal and vertical directions, based on the ISO12233 standard. The distribution of the test patterns can be adjusted according to the field angle of the camera and the test field requirements of clients, a central field test pattern is arranged in the central area of the image, and the number of peripheral field test patterns is four, eight and the like.
In other embodiments, the test pattern has slits, star patterns, dead leaf patterns, and the like.
In this embodiment, each of the checkerboards is square, and the number of the checkers is 4x4 or more between the black and white in the transverse direction and the longitudinal direction.
S20, acquiring image information of the test pattern card through a camera, determining the position of the central view field test pattern, and moving a lens or an image sensor until the corner point of the central view field test pattern is positioned at the center of the image. Specifically, for the test chart card in fig. 2, two circles are first identified, the position of the center field test pattern can be determined by the positions of the two circles, and the corner point of the center field test pattern is moved to the center of the image. For the test chart card in fig. 3, the black grid of the checkerboard is hollowed out, so that the sharpness algorithm can not grasp the corner points of the checkerboard, but only grasp the corner points of the central field of view test pattern, and the corner points of the central field of view test pattern can be directly moved to the center of the image. This step is to substantially ensure that the test pattern is in the desired field of view or close proximity during focusing and does not define the final camera internal parameter center position.
S30, obtaining definition change curves of the central view field test pattern and the plurality of peripheral view field test patterns through scanning of the camera in the focal length direction, calculating the inclination angle of the lens and the image sensor according to the definition change curves, and adjusting the parallelism of the lens and the image sensor.
The non-parallel visual representation of the lens and the image sensor is that the peak value of the definition curve of each test pattern is scattered on different scanning steps before adjustment, and the peak value of the definition curve is basically fallen at one place at the same time after adjustment. Because the lens is equivalent to a black box, the main point position and the like of the lens cannot be accurately known, and the actual lens cannot generally reach the ideal state in design because of assembly errors and the like, the traditional active alignment algorithm considers that the lens and the image sensor are leveled in this way, and the optical axis of the lens is likely to be inclined actually because of the characteristics of the lens.
In one embodiment, the method further comprises the steps of: after leveling, scanning once in the focal length direction, returning to the definition peak point, and determining the horizontal relative position of the lens and the image sensor by taking the corner point of the central view field test pattern as the principle of imaging at the center of the image. However, since the optical axis may have an inclination angle in this state, for a lens with a relatively large focal length, for example, a 16mm long focal length, if the lens is inclined by 0.5 degrees, the pixel size is 3um, the center is offset by about 46 pixels, and for a vehicle-mounted camera or the like requiring accurate measurement, the deviation is beyond the allowable range, not to mention that the introduction of a variable during glue thermal curing may cause more deviation.
S40, marking a distortion center of the camera through the checkerboard, and adjusting the relative horizontal position of the lens and the image sensor according to the difference between the distortion center and the image center so as to correct the deviation. The purpose is to make the distortion center coincide with the image center as much as possible, reduce the deviation and improve the precision.
Specifically, the characteristic that an image obtained by imaging the checkerboard in an ideal small hole is parallel to the actual imaging of the checkerboard is utilized, and the distortion center of the camera is calibrated by utilizing the epipolar geometry relation. More specifically, the distortion center of the camera is determined by the epipolar point determined by both the image obtained by imaging the ideal aperture of the checkerboard and the actual imaging of the checkerboard.
In the embodiment, the calibration is based on a single image, so that the calibration efficiency is greatly improved, and the alignment precision is ensured.
In one embodiment, the following steps are further included after step S40:
And determining a correction result through recalibration, and if the deviation does not meet the requirement, continuing correction. This process can be repeated, depending on the different requirements for accuracy and production efficiency.
In one embodiment, the following steps are further included after step S40: the positions of the lens and the image sensor are determined by glue curing.
The above embodiments are merely preferred embodiments for fully explaining the present invention, and the scope of the present invention is not limited thereto. Equivalent substitutions and modifications will occur to those skilled in the art based on the present invention, and are intended to be within the scope of the present invention. The protection scope of the invention is subject to the claims.
Claims (8)
1. The camera active alignment method combined with calibration is characterized by comprising the following steps of:
Providing a test chart card, wherein the test chart card is integrated with a checkerboard, a central view field test pattern and a plurality of peripheral view field test patterns, the central view field test pattern is embedded in the checkerboard, and corner points are coincident with the corner points of the checkerboard;
acquiring image information of the test pattern card through a camera, determining the position of the central view field test pattern, and moving a lens or an image sensor until the corner point of the central view field test pattern is positioned at the center of the image;
Obtaining definition change curves of the central view field test pattern and the plurality of peripheral view field test patterns through scanning of the camera in the focal length direction, calculating the inclination angle of the lens and the image sensor according to the definition change curves, and adjusting the parallelism of the lens and the image sensor;
Marking a distortion center of the camera through the checkerboard, and adjusting the relative horizontal position of the lens and the image sensor according to the difference between the distortion center and the image center so as to correct the deviation;
The distortion center of the camera is marked through the checkerboard, and the method specifically comprises the following steps: the characteristic that an image obtained by imaging the checkerboard in an ideal small hole is parallel to the actual imaging of the checkerboard is utilized, and the distortion center of the camera is calibrated by utilizing the relation of epipolar geometry;
The calibration of the distortion center of the camera by utilizing the relation of epipolar geometry specifically comprises the following steps: and determining the distortion center of the camera through the epipolar point determined by the image obtained by the checkerboard after the ideal pinhole imaging and the actual imaging of the checkerboard.
2. The method for actively aligning a camera with calibration according to claim 1, wherein the calibrating the distortion center of the camera by the checkerboard, and adjusting the relative horizontal position of the lens and the image sensor according to the difference between the distortion center and the image center, further comprises: and determining a correction result through recalibration, and if the deviation does not meet the requirement, continuing correction.
3. The method for actively aligning a camera with calibration according to claim 1, wherein the calibrating the distortion center of the camera by the checkerboard, and adjusting the relative horizontal position of the lens and the image sensor according to the difference between the distortion center and the image center, further comprises: the positions of the lens and the image sensor are determined by glue curing.
4. The camera active alignment method according to claim 1, wherein the test chart is film printing or glass etching.
5. The camera head active alignment method according to claim 4, wherein the film printed test chart is attached or pressed on a flat bearing surface.
6. The method for actively aligning a camera with calibration according to claim 1, wherein the test card is transmissive or reflective.
7. The camera active alignment method according to claim 1, wherein the center field test pattern and the plurality of peripheral field test patterns are each a black naked sword side inclined by 5 degrees based on the ISO12233 standard, and include both horizontal and vertical directions.
8. The camera active alignment method for combining calibration according to claim 1, wherein each grid in the checkerboard is square, and the number of the grids is greater than or equal to 4x4 between the horizontal black and white.
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| CN113766210B (en) * | 2021-07-21 | 2024-05-10 | 歌尔光学科技有限公司 | Test method and device |
| CN115361497B (en) * | 2022-08-01 | 2024-06-07 | 歌尔股份有限公司 | Method, device, equipment and storage medium for measuring inclination angle of camera module |
| CN116320747A (en) * | 2023-05-19 | 2023-06-23 | 四川华鲲振宇智能科技有限责任公司 | Method for horizontally checking image sensor and lens |
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| KR101482645B1 (en) * | 2013-06-28 | 2015-01-16 | (주) 세인 | Distortion Center Correction Method Applying 2D Pattern to FOV Distortion Correction Model |
| CN107833255A (en) * | 2017-11-17 | 2018-03-23 | 广州市安晓科技有限责任公司 | A kind of fish-eye quick calibrating method |
| CN109961482A (en) * | 2017-12-22 | 2019-07-02 | 比亚迪股份有限公司 | Camera calibration method, device and vehicle |
| CN108581869B (en) * | 2018-03-16 | 2020-05-15 | 深圳市策维软件技术有限公司 | Camera module alignment method |
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| CN104038755A (en) * | 2014-04-30 | 2014-09-10 | 惠州华阳通用电子有限公司 | Camera distortion center point testing device and identification method |
| CN104881874A (en) * | 2015-06-04 | 2015-09-02 | 西北工业大学 | Double-telecentric lens calibration method based on binary quartic polynomial distortion error compensation |
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