TWI663421B - Wide angle lens distortion correction method, device and system - Google Patents

Abstract

The invention discloses a method, a device and a system for correcting a distortion of a wide-angle lens, wherein the method includes: obtaining n half-field angles θ ₁ to θ _{n of the} wide-angle lens, and obtaining an adjacent field-of-view ratio β according to the n half-field angles ₁ to β _(n-1) ; get image heights r ₁ to r _n corresponding to n half field angles according to n half field angles; according to adjacent field ratio β ₁ to β _(n-1) and n The image heights r ₁ to r _n corresponding to the half field angles are used to obtain the image height relationship of the adjacent half field angles. Based on the relationship between the image height corresponding to the maximum field angle and the image height relationship of the adjacent half field angles, it is calculated recursively. Obtain the image height of each half field of view angle; correct the distortion of the wide-angle lens in the central field of view according to the image height of each half field of view. This method can sequentially correct the distortion of the wide-angle lens in the central field of view according to the image height of each half of the field of view, so that the sampling rate of the central field of view is higher than the edge, which effectively improves the correction efficiency, reduces costs, and is simple and easy to implement.

Description

Distortion correction method, device and system for wide-angle lens

The invention relates to the technical field of image processing, and in particular, to a method, a device, and a system for correcting distortion of a wide-angle lens.

ADAS (Advanced Driver Assistance System) uses various sensors installed on the car to collect environmental data inside and outside the car at the first time for the identification, detection and detection of static and dynamic objects. Technical processing such as tracking can enable the driver to detect the possible danger in the fastest time, effectively increasing the comfort and safety of the car. Therefore, ADAS plays a very important role in the realization of autonomous driving.

In related technologies, a typical ADAS system generally has three cameras at the front of the vehicle, and the field of view angles are approximately 42 degrees, 60 degrees, and 120 degrees. If binocular vision is required, the number of cameras needs to be doubled; each camera is equipped with a 2MP (Mega -Pixels (megapixels), which is a 2-megapixel CMOS sensor.

However, there is a lot of redundancy in the related technology settings. For example, the field of view of the 42-degree camera is covered by the field of view of the 60-degree camera and the 120-degree camera. This makes the multiple cameras not only increase the complexity of the system connection and the various cameras. The complexity of communication and synchronization, and the cost of the entire system High, and the cameras need to ensure a good overlap of the field of view, resulting in a fixed angular relationship between each other, at the same time the overall and the car itself must also ensure the angle, so it is necessary to regularly do between the camera and camera and car Inter-body correction, the three-camera correction itself results in relatively complicated and heavy workload, which needs to be solved urgently.

The present invention aims to solve at least one of the technical problems in the related technology.

For this reason, an object of the present invention is to propose a method for correcting distortion of a wide-angle lens. This method can realize that the sampling rate of the central field of view of the wide-angle lens is higher than the edge, so that a one-camera system can be used instead of a three-camera system.

Another object of the present invention is to provide a distortion correction device for a wide-angle lens.

Another object of the present invention is to provide a distortion correction system for a wide-angle lens.

To achieve the above object, an embodiment of the present invention provides a method for correcting distortion of a wide-angle lens, including the following steps: obtaining n half-field angles θ ₁ to θ _{n of the} wide-angle lens, where θ _n is θ _(n-1) Adjacent half-field angles of angles, and obtain the adjacent field-view ratios β ₁ to β _(n-1) according to the n half-field angles θ ₁ to θ _n , where n is a positive integer; according to the n half-field angles Field angles θ ₁ to θ _n obtain the image heights r ₁ to r _n corresponding to the n half field angles; according to the adjacent field ratio β ₁ to β _(n-1) and the n half field angles Get the image height relationship of the adjacent half field angles from the image heights r ₁ to r _n , and recursively calculate each half according to the image height relationship corresponding to the maximum field angle and the image height relationship of the adjacent half field angles. The image height of the field of view angle; sequentially corrects the distortion of the wide-angle lens in the central field of view according to the image height of each half of the field of view angle.

The distortion correction method of the wide-angle lens according to the embodiment of the present invention can be based on the adjacent field of view ratio. Value and the image height corresponding to the complex half field of view angle to obtain the image height relationship of adjacent half field angles, and based on the relationship between the image height corresponding to the maximum field angle and the image height relationship of adjacent half field angles, each The image height at half field angle, so that the distortion of the wide field lens in the central field of view is corrected sequentially according to the image field height of each half field of view, so that the sampling rate of the central field of view of the wide angle lens is higher than the edge, which improves the accuracy and reliability of the correction. At the same time, improving correction efficiency and effectively reducing costs is simple and easy to implement.

In addition, the method for correcting the distortion of the wide-angle lens according to the above embodiment of the present invention may also have the following additional technical features: Further, in an embodiment of the present invention, the n half-field angles θ ₁ to θ _{n of the} wide-angle lens are obtained. Further comprising: collecting the maximum field angle of the wide-angle lens and a preset number of adjacent field angles; obtaining the half field angle θ ₁ according to the maximum field angle of the wide-angle lens, and according to the phase of the preset number The adjacent field angles give the half field angles θ ₂ to θ _n .

Further, in an embodiment of the present invention, the adjacent halves are obtained according to the adjacent field ratios β ₁ to β _(n-1) and the image heights r ₁ to r _n corresponding to the n half field angles. The image height relationship of the viewing angle further includes: performing sampling processing on the image heights r ₁ to r _n corresponding to the n half viewing angles according to the viewing angle relationship, wherein the sampling processing adopts an interpolation method; The field angle relation gives the image height relation of the adjacent half field angles.

Further, in an embodiment of the present invention, the field angle relationship is: And so on,

Further, in an embodiment of the present invention, the image height relationship of the adjacent half-field angles is: In addition, the image height of each half field angle is obtained by recursively calculating the relationship between the image height corresponding to the maximum field angle and the image height of the adjacent half field angle: Among them, r _(n-1) is the image height corresponding to the half field angle θ _(n-1) , r _n is the image height corresponding to the half field angle θ _n , β ₁ is the ratio of θ ₁ and θ ₂ , β ₂ is a ratio of θ ₂ and θ ₃ , and β _{( n -1)} is a ratio of θ _(n-1) and θ _n .

Further, in an embodiment of the present invention, the maximum field angle is greater than or equal to 70 °.

Further, in an embodiment of the present invention, the maximum field angle is 100 ° or more and 190 ° or less.

In order to achieve the above object, an embodiment of another aspect of the present invention proposes a distortion correction device for a wide-angle lens, including: a collection module for obtaining n half-field angles θ ₁ to θ _{n of the} wide-angle lens, where θ _n is θ _(n-1) adjacent half field angles, and obtain the adjacent field ratios β ₁ to β _(n-1) according to the n half field angles θ ₁ to θ _n , where n is a positive integer; A module for obtaining the image heights r ₁ to r _n corresponding to the n half field angles θ ₁ to θ _n according to the n half field angles θ; ₁ to β _(n-1) and the image heights r ₁ to r _n corresponding to the n half field angles are used to obtain the image height relationship of the adjacent half field angles, and according to the image height corresponding to the maximum field angle and the phase The image height relationship of the adjacent half field angles is obtained through the recursive calculation of the image height of each half field angle; a correction module is used to sequentially correct the distortion of the wide-angle lens in the central field of view according to the image height of each half field angle. .

The distortion correction device for the wide-angle lens according to the embodiment of the present invention can obtain the image height relationship of the adjacent half field angles according to the adjacent field ratio and the image height corresponding to the complex half field angle, and according to the image height corresponding to the maximum field angle The relationship between the image height of adjacent half-field angles and the image height of each half-field angle is calculated recursively, so that the distortion of the wide-angle lens in the central field of view is corrected in turn according to the image height of each half-field angle, and the wide-angle lens center view is realized. The sampling rate of the field is higher than the edge. While improving the accuracy and reliability of the correction, the correction efficiency is improved, the cost is effectively reduced, and it is simple and easy to implement.

In addition, the distortion correction device for the wide-angle lens according to the above embodiment of the present invention may also have the following additional technical features: Further, in an embodiment of the present invention, the collecting module further includes: a collecting unit for collecting the The maximum field angle of the wide-angle lens; a selection unit for obtaining the half field angle θ ₁ according to the maximum field angle of the wide angle lens, and obtaining the half field angle according to the adjacent previous half field angle θ _(n-1) Field angle θ _n .

Further, in an embodiment of the present invention, the calculation module further includes: a processing unit, configured to sample the image heights r ₁ to r _n corresponding to the n half field angles according to the field angle relation formula. Processing, in which the sampling process adopts an interpolation method; and an obtaining unit, configured to obtain an image height relationship of adjacent half-field angles according to the view angle relationship.

Further, in an embodiment of the present invention, the field angle relationship is: And so on,

Further, in an embodiment of the present invention, the image height relationship of the adjacent half-field angles is: In addition, the image height of each half field angle is obtained by recursively calculating the relationship between the image height corresponding to the maximum field angle and the image height of the adjacent half field angle: Among them, r _(n-1) is the image height corresponding to the half field angle θ _(n-1) , r _n is the image height corresponding to the half field angle θ _n , β ₁ is the ratio of θ ₁ and θ ₂ , β ₂ is a ratio of θ ₂ and θ ₃ , and β _{( n -1)} is a ratio of θ _(n-1) and θ _n .

Further, in an embodiment of the present invention, the maximum field angle is greater than or equal to 70 °.

Further, in an embodiment of the present invention, the maximum field angle is 100 ° or more and 190 ° or less.

In order to achieve the above object, another embodiment of the present invention provides a distortion of a wide-angle lens. A variable correction system includes the wide-angle lens and the pixel sensor corrected by the distortion correction device of the wide-angle lens.

The distortion correction system of the wide-angle lens according to the embodiment of the present invention can obtain the image height relationship of the adjacent half field angles according to the adjacent field ratio and the image height corresponding to the complex half field angle, and according to the image height corresponding to the maximum field angle The relationship between the image height of adjacent half-field angles and the image height of each half-field angle is calculated recursively, so that the distortion of the wide-angle lens in the central field of view is corrected in turn according to the image height of each half-field angle, and the wide-angle lens center view is realized. The sampling rate of the field is higher than the edge. While improving the accuracy and reliability of the correction, the correction efficiency is improved, the cost is effectively reduced, and it is simple and easy to implement.

Further, in an embodiment of the present invention, the wide-angle lens includes a first lens, a second lens, a third lens, an aperture, a fourth lens, a fifth lens, a sixth lens, and a seventh lens in order from the object side to the image side. Lenses, filters.

Further, in an embodiment of the present invention, the first lens, the second lens, and the seventh lens are all aspherical lenses.

Additional aspects and advantages of the present invention will be given in part in the following description, part of which will become apparent from the following description, or be learned through the practice of the present invention.

10‧‧‧Distortion correction device for wide-angle lens

100‧‧‧ Collection Module

200‧‧‧Get Module

300‧‧‧ Computing Module

400‧‧‧correction module

CMOS‧‧‧Complementary Metal Oxide Semiconductor

L1, L2, L3, L4, L5, L6, L7‧‧‧ lenses

S1‧‧‧ aperture

S2‧‧‧ Filter

S101, S102, S103, S104‧‧‧ steps

The above and / or additional aspects and advantages of the present invention will become apparent and easy to understand from the following description of the embodiments with reference to the accompanying drawings, wherein: FIG. 1 is a flow chart of a method for correcting a distortion of a wide-angle lens according to an embodiment of the present invention Figure; FIG. 2 is a schematic diagram of the relationship between the image height of a wide-angle lens according to an embodiment of the present invention at adjacent field angles; FIG. 3 is a schematic structural diagram of a distortion correction device of the wide-angle lens according to an embodiment of the present invention; FIG. 5 is a schematic structural view of a wide-angle lens using recursive distortion correction; FIG. 5 is a schematic diagram of a grid point of a wide-angle lens distortion correction system before down-sampling according to a specific embodiment of the present invention; Schematic diagram of the grid pattern of the wide-angle lens distortion correction system in a specific embodiment after downsampling.

An embodiment of the present invention is described in detail below. An example of the embodiment is shown in the drawings, wherein the same or similar reference numerals indicate the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the drawings are exemplary and are intended to explain the present invention, but should not be construed as limiting the present invention.

Before introducing the method, device, and system for correcting the distortion of the wide-angle lens according to the embodiments of the present invention, the method for correcting the distortion of the wide-angle lens in the related art will be briefly introduced.

The sensor equipped with 2MP pixels on the market and ADAS system camera is about 1/3 "in size, and the next-generation sensor will be launched with 8MP pixels. Based on this, can you design a camera, Using a high-pixel sensor camera to achieve the effect of the existing three-sensor camera? If simply based on the superposition of pixels, then the number of pixels of the latest 8MP sensor has exceeded three 2MP The sum of the sensors. However, an 8MP sensor can meet the pixel requirements of a maximum field angle of 120 °, but may not meet the 2MP pixel requirements of a central field angle of 60 ° and 42 °.

In the related art, a typical imaging optical system has the problems of a low sampling rate near the center of the field of view and a high sampling rate at the edge, and at the same time, the illuminance at the edge also decreases due to the increase of the field angle. If the imaging system is corrected according to the ideal distortion curve ( r = f * tanθ , θ is the half field angle), assuming that the relative image height of the 120-degree horizontal field of view is 1, then the relative image height corresponding to the 60-degree center of view field is tan (30 °) / tan (60 °) 0.333, 42 degree center of view full field of view corresponds to image height tan (21 °) / tan (60 °) 0.222. In this way, the image of 8MP at 120 degrees is only 0.9MP after intercepting the area corresponding to 60 degrees in the center, and the full field of view corresponding to 42 degrees has dropped to 0.4MP. This method of correcting the ideal distortion obviously cannot meet the original requirements.

Similarly, if the system is based on the perfect f-theta distortion correction ( r = f * θ , θ is the half field angle) method, the relative image height corresponding to the full field of view at the center of 60 degrees is (30 °) / (60 ° ) = 0.5, the full field of view at the center of 42 degrees corresponds to the image height (21 °) / (60 °) = 0.35, so the 8MP picture at 120 degrees is 2MP after the center corresponds to the 60 degree area, and the corresponding at the intercept center 1MP after 42-degree field of view, the f-theta distortion correction method obviously did not meet the original expectations.

In summary, the main problem of the ideal distortion correction method and f-theta distortion correction method in the related art is the high sampling rate of the edges. For ideal distortion correction, the edge sampling rate is higher than the central field of view, that is, the edge makes the force too large; for f-theta distortion correction, the edge and center sampling rate are the same, that is, the force is uniform.

The present invention is based on the above-mentioned problems, and proposes a distortion correction method and device for a wide-angle lens.

The distortion correction method, device, and system of the wide-angle lens according to the embodiments of the present invention are described below with reference to the drawings. First, the distortion correction method of the wide-angle lens according to the embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a flowchart of a distortion correction method of a wide-angle lens according to an embodiment of the present invention.

As shown in Figure 1, the distortion correction method of the wide-angle lens includes the following steps:

In step S101, n half-field angles θ ₁ to θ _{n of the} wide-angle lens are obtained, where θ _n is an adjacent half-field angle θ _(n-1) , and according to the n half-field angles θ ₁ to θ _n obtains adjacent field ratios β ₁ to β _(n-1) , where n is a positive integer.

Further, in an embodiment of the present invention, acquiring n half field angles θ ₁ to θ _{n of the} wide-angle lens further includes: collecting the maximum field angle of the wide-angle lens and the preset number of adjacent field angles; The half field angle θ1 is obtained according to the maximum field angle of the wide-angle lens, and the half field angles θ ₂ to θ _{n are} obtained according to the preset number of adjacent field angles.

Preferably, in an embodiment of the present invention, the maximum field angle is greater than or equal to 70 °.

Preferably, in an embodiment of the present invention, the maximum field angle is 100 ° or more and 190 ° or less.

It can be understood that a wide-angle lens, also known as a short focal length lens, is a lens with a field of view greater than 60 °; for a zoom lens on a camera, the focal length is less than 25mm. The use of a wide-angle lens is conducive to the performance of large-scale scenes at close range, The wide-angle lens is suitable for displaying the main body of the picture and its environment. Using the characteristics of the depth of field of the wide-angle lens, you can perform multi-level representation of objects, increasing the capacity and information of the picture; using the wide-angle lens to approach the object at close range, you can complete snap shots and candid shots. ; At the same time, it is conducive to maintaining a smooth picture of mobile photography.

It can be understood that, in the embodiment of the present invention, the maximum HFOV (Horizontal Field Of View) of the wide-angle lens can be obtained first, and the half field angles adjacent to the n wide-angle lenses can be sequentially selected. Field angle θ ₁ , θ ₂ θ _n , where θ ₁ = HFOV / 2, n > = 3, θ ₁ > θ ₂ > θ ₃ >...> θ _n , it should be noted that the maximum field angle of the wide-angle lens can be greater than or equal to 70 ° The maximum field angle of the preferred wide-angle lens is 100 ° or more and 190 ° or less.

In step S102, the n according to the half field angle θ ₁ to obtain [theta] _n n half angle of view corresponding to the image height r ₁ to r _n.

In step S103, the image height relationship between the adjacent half field angles is obtained according to the adjacent field ratios β ₁ to β _(n-1) and the image heights r ₁ to r _n corresponding to the _n half field angles, and according to The relationship between the image height corresponding to the maximum field angle and the image height of the adjacent half-field angles is obtained by recursively calculating the image height of each half-field angle.

Further, in an embodiment of the present invention, the adjacent half field angles are obtained according to the adjacent field ratios β ₁ to β _(n-1) and the image heights r ₁ to r _n corresponding to the _n half field angles. The image height relationship further includes: performing sampling processing on the image heights r ₁ to r _n corresponding to n half field angles through the field angle relationship formula, wherein the sampling processing adopts an interpolation method; and the phase is obtained according to the field angle relationship formula. Image height relationship of adjacent half field angle.

Further, in an embodiment of the present invention, the field angle relationship is: And so on,

Wherein, in an embodiment of the present invention, the relationship between the image heights of adjacent half-field angles is: In addition, according to the relationship between the image height corresponding to the maximum field angle and the image height relationship of adjacent half field angles, the image height of each half field angle is calculated recursively: Among them, r _(n-1) is the image height corresponding to the half field angle θ _(n-1) , r _n is the image height corresponding to the half field angle θ _n , β ₁ is the ratio of θ ₁ and θ ₂ , β ₂ is a ratio of θ ₂ and θ ₃ , and β _{( n -1)} is a ratio of θ _(n-1) and θ _n .

It can be understood that according to the embodiment of the present invention, the half-field angles θ ₁ and θ ₂ adjacent to the n wide-angle lenses can be selected in sequence. θ _n , and define n half field angles θ ₁ , θ ₂ Image heights r ₁ , r ₂ corresponding to each half field angle of θ _n r _n , where θ ₁ = HFOV / 2, n > = 3, θ ₁ > θ ₂ > θ ₃ >...> θ _n , the schematic diagram of the image height relationship between adjacent half field angles is shown in Fig. 2 .

In addition, in the embodiment of the present invention, the ratios of the adjacent fields of view may be defined as follows: β ₁ = θ ₁ / θ ₂ , β ₂ = θ ₂ / θ ₃ , Β _{( n -1)} = θ _{( n -1)} / θ _n , so that the image heights of n half-field angles are sampled by interpolation according to the ratio of adjacent half-field angles to obtain the relationship, where The sampling processing of the image heights of the n half-field angles of the wide-angle lens by interpolation can be achieved by the following relationship:

...

Among them, r ₁ is the image height corresponding to the half field angle θ ₁ , r ₂ is the image height corresponding to the half field angle θ ₂ , r ₃ is the image height corresponding to the half field angle θ ₃ , and r _(n-1) Is the image height corresponding to the half field angle θ _(n-1) , r _n is the image height corresponding to the half field angle θ _n , β ₁ is the ratio of θ ₁ and θ ₂ and β ₂ is the ratio of θ ₂ and θ ₃ The ratio β _{( n -1)} is a ratio of θ _(n-1) and θ _n , and n is an integer of 3 or more.

Incidentally, the meaning of the relation (3) is the center of a small field of high resolution corresponding to image height θ _n r _n, can be down-sampled at adjacent large field of view _{(n -1) θ,} linear The downsampling magnification is the field ratio β _{( n -1)} , and the newly added large field image height ( r _{( n -1)} -r _n ) part, ideally does not need to be resampled, that is, it will not waste the existing As a result, the large field of view θ _{( n -1)} itself achieves a pixel resolution that is completely consistent with the adjacent small field of view θ _n , that is, the image height of the large field of view after downsampling is equal to r _n .

In addition, in the embodiment of the present invention, the above-mentioned relational expressions (1) to (3) can be further optimized to obtain the image height relationship of adjacent half-field angles:

...

That is, since the image height corresponding to the maximum half-field angle of the wide-angle lens is known to be r ₁ , the embodiment of the present invention can calculate the image height relationship by recursion:

In step S104, the distortion of the wide-angle lens in the central field of view is sequentially corrected according to the image height of each half of the field of view.

It can be understood that the embodiment of the present invention can sequentially correct the distortion of the wide-angle lens in the central field of view according to the image height of each half of the field of view.

For example, the embodiment of the present invention uses a wide-angle lens system with recursive distortion correction, and is preferably composed of a 8MP CMOS (Complementary Metal Oxide Semiconductor) sensor and a wide-angle lens with a maximum field angle of 120 degrees. The optical system can effectively replace the three-lens (field of view angles of 120 degrees, 60 degrees, and 42 degrees) and three 2MP sensor systems, that is, to achieve the entire wide-angle lens field of view of 120 degrees, the corresponding analysis degrees 8MP, center 60 degrees and 42 degrees Small field, can achieve the same resolution center 2MP; the following steps: first, the maximum angle of view embodiment selected the wide angle lens of the embodiment of the present invention is 120 degrees half θ ₁ is 60 degrees, The image height corresponding to its half field angle is r ₁ ; half of the adjacent middle field angle of 60 degrees θ ₂ is 30 degrees, and the image height corresponding to its half field angle is r ₂ ; the center small field angle is 42 degrees The half θ ₃ is 21 degrees, and the image height corresponding to the half field angle is r ₃ ; thus, the ratio of adjacent fields of view is obtained: β ₁ = θ ₁ / θ ₂ = 60/30 = 2, β ₂ = θ ₂ / θ ₃ = 30/21 = 10/7; Secondly, in the embodiment of the present invention, the half field angles θ ₂ and θ ₃ are The corresponding image height is sampled separately and processed by the following relationship:

The above relationship is further optimized to obtain the image height relationship of adjacent half-field angles:

Since it is known that the image height corresponding to the maximum half field angle of the wide-angle lens is r ₁ , the relationship of the image height is calculated recursively:

Therefore, the above-mentioned wide-angle lens is subjected to a distortion correction design according to the obtained image height of each half of the field angle.

According to the relational expressions (12) and (13), assuming that the image height r ₁ corresponding to the 120-degree field of view angle is 1, the normalized image height r ₂ corresponding to the adjacent 60-degree field of view angle r ₂ = 2/3 * r ₁ 0.6667; when calculating the image height of the center of view angle of 42 degrees, the embodiment of the present invention can adopt a recursive algorithm, and the corresponding normalized image height r ₁ = 10/13 * 2/3 * r ₁ = 20/39 0.5128.

In addition, the recursive distortion correction method provided by the embodiment of the present invention and the See Table 1 for the beneficial effects of distortion correction methods. Because this distortion requirement is based on the system's non-linear sampling, it is not based on the human eye's own preference, but is completely aimed at machine vision. Moreover, the specific implementation of this sampling used in the embodiment of the present invention is interpolation, and The interpolation point itself is a non-linear distribution, so the interpolation position can be calculated in advance to increase the speed. Table 1 is a comparison table of the image heights of the recursive distortion control in the embodiment of the present invention and the distortion control in the related art.

This embodiment of the present invention uses a CMOS sensor with 8MP pixels and a wide-angle lens with a maximum field of view of 120 degrees. If the image height relationship is converted into a pixel relationship, such as the ARO820 from ON Semiconductor's 8MP, the pixels are 3840 * 2160. Then the pixels of the half-field of view are 1920 * 1080, and the correspondence between the recursive distortion control and the distortion control pixels in the related technology according to the embodiment of the present invention can be obtained, as shown in Table 2. Table 2 is a horizontal pixel comparison table between the recursive distortion control and the distortion control in the related art according to the embodiment of the present invention.

As can be seen from Tables 1 and 2, the result of the recursive distortion correction control used in the embodiment of the present invention is to ensure that the central part of the wide-angle lens achieves a resolution of 2MP after being intercepted. Specifically, according to Table 2, it can be seen that if only the information within the central half-field angle of 21 degrees is intercepted, the corresponding number of pixels is 985, which is basically the same as the 964 (1928/2) pixels of AR0231 of ON Semiconductor 2MP. In other words, the amount of pixel information contained in this section is the same as if you designed a lens and equipped it with AR0231.

Further, for a half field of view angle of 30 degrees, after down-sampling the 21 degree part of the center, the included pixels are also 985 (985 * 7/10 + 1280-985 = 985). Similarly, in a 60-degree field of view, the effective pixel resolution after down-sampling a 30-degree field of view is also 985.

In summary, the wide-angle lens with non-linear recursive distortion correction provided by the embodiment of the present invention has a resolution of 8MP at a 120-degree field of view angle and a small field of view of 42 degrees at the center, which can achieve a resolution of 2MP at the center; for the center 42 Down-sampling the field of view and combining the adjacent 60-degree field of view information can also achieve 2MP resolution; further down-sampling this 60-degree field of view image, combining information between 60 and 120 degrees, can achieve 2MP resolution for full field of view. Therefore, in the embodiments of the present invention, a higher-pixel sensor and a recursive distortion-correcting wide-angle lens can replace the plurality of low-pixel sensors and the plurality of lens systems.

Because the sampling rate of the central part is higher, in the process of downsampling, a noise reduction algorithm can be added to solve the problem of increasing dark noise due to the reduction in pixel size. For example, the binning of the pixels in the center. For example, if it is double downsampling, you can simply do a 2 × 2 matrix kernel (Kernel) convolution on the center part, and then sample.

A typical application scenario is when the daylight is sufficient, the central part such as a 42 degree field of view The resolution in the angle is sufficient, the signal strength is sufficient, and the ADAS system can see far away; at night, there is insufficient light. Due to the limitation of the illuminance of the headlights and street lights, the 42-degree camera can look far, but the obtained photos are very noisy and the illumination is not enough. At this time, down-sampling can be performed on the 60-degree field of view to remove some noise. At this time, although the resolution of the central part within 42 degrees was sacrificed, the low light sensitivity of the system was improved. Since the driving speed at night can be lower, the resolution of the objects to be discriminated is lower. Furthermore, if the illuminance is lower and the visibility is worse, based on the 120-degree field of view, the center 60-degree and 42-degree can be de-noised and down-sampled simultaneously.

In other words, an embodiment of the present invention can use an 8MP CMOS chip, and now produces three 2MP images, which respectively correspond to a 42-degree field of view, a 60-degree field of view, and a 120-degree field of view. When the light is sufficient, the 42-degree field of view and the 120-degree field of view can serve the ADAS system at the same time. At this time, the 42-degree field of view ensures that the ADAS system can see far. When the light is weak, it depends on the field of view of 60 degrees and 120 degrees. When the light is very weak, you can rely on a 2MP image generated by a 120-degree field of view. At this time, the 8MP sensor chip has a pixel size of 2.1um, and the effect achieved is equivalent to a 2 × 2 binning of the sensor, and the effective pixel size is 4.2um. This size and low-light performance are very good. Good AR0220 wafers are consistent.

Compared with the distortion correction control method in the related art, the wide-angle lens distortion correction method of the embodiment of the present invention also has the following beneficial effects: (1) The embodiment of the present invention effectively corrects the distortion of the wide-angle lens and achieves a high sampling rate of the central field of view At the edges, the resolution of the central field of view of the wide-angle lens can be quantitatively adjusted as the system needs; (2) The large degree of information is compressed to a relatively small center field of view, making the contrast of the lens system even greater than 1, This makes it possible to increase the CRA (Chief Ray Angle) during optical design, thereby reducing the overall length of the system and making the entire system more compact.

Taking Table 2 as an example, in the actual optical lens design, several key points can be added to the distortion control. The specific needs to control the image height at 1920 pixels and 985 pixels. If necessary, the distortion point at 1280 pixels can be added. Ensure that the distortion curve transitions smoothly in these three points.

It is emphasized here that there is no need to strictly control the distortion at 1280 pixels, the main reason is that it is close to the central field of view, that is, the 21-degree half field of view and the 30-degree half field of view are very close, and effective control of the main light may have certain challenges. In other words, even if the 30-degree field of view cannot be effectively controlled, the direct result is that when the 30-degree field of view is sampled, the size of the obtained picture exceeds 2MP (such as 3MP). This situation can be easily handled by subsequent mathematical processing. Further correction; Another compromise that can be considered is the strict control of the 30-degree half-field of view, while the 21-degree half-field of view itself is more difficult to do distortion correction, and the consequence is that the picture cut out of the 21-degree half-view field itself does not have 2MP. The choice of a specific scheme needs to be determined by those skilled in the art according to the actual situation, but distortion at 60 degrees is a key to achieving this algorithm, and distortion needs to be effectively controlled here.

According to the method for correcting a distortion of a wide-angle lens according to an embodiment of the present invention, an image height relationship of adjacent half-field angles can be obtained according to an adjacent field-of-view ratio and an image height corresponding to a complex half-field angle, and according to a maximum field-of-view angle corresponding The relationship between the image height and the image height of adjacent half-field angles is calculated recursively to obtain the image height of each half-field angle, so that according to the image height of each half-field angle, the distortion of the wide-angle lens in the central field of view is corrected in order, and a wide-angle lens is realized. The sampling rate of the central field of view is higher than the edge, so that the resolution of the central field of view of the wide-angle lens can be quantitatively adjusted according to the needs of the system, and the total angle of the system can be reduced by increasing the incident angle of the light, making the entire system more compact; through a high pixel The camera effectively replaces the complex low-pixel camera, saves the cost of ADAS system, simplifies the requirements of system correction and system calculation, improves the accuracy and reliability of correction, improves the correction efficiency, effectively reduces the cost, and is easy to implement.

Next, a distortion correction device for a wide-angle lens according to an embodiment of the present invention will be described with reference to the drawings.

FIG. 3 is a schematic structural diagram of a distortion correction device for a wide-angle lens according to an embodiment of the present invention.

As shown in FIG. 3, the distortion correction device 10 for the wide-angle lens includes a collection module 100, an acquisition module 200, a calculation module 300, and a correction module 400.

The collection module 100 is configured to obtain n half-field angles θ ₁ to θ _{n of the} wide-angle lens, where θ _n is an adjacent half-field angle of θ _(n-1) , and according to the n half-field angles θ ₁ to θ _n obtain adjacent field ratios β ₁ to β _(n-1) , where n is a positive integer. N acquisition module 200 for obtaining a half angle of view corresponding to the image height r ₁ to r _n n The half field angle θ ₁ to θ _n. The calculation module 300 is configured to obtain the image height relationship of the adjacent half field angles according to the adjacent field ratios β ₁ to β _(n-1) and the image heights r ₁ to r _n corresponding to the _n half field angles, and According to the relationship between the image height corresponding to the maximum field angle and the image height relationship of adjacent half-field angles, the image height of each half-field angle is obtained through recursive calculation. The correction module 400 is used to sequentially correct the distortion of the wide-angle lens in the central field of view according to the image height of each half of the field of view. The device 10 according to the embodiment of the present invention can correct the distortion of the wide-angle lens in the central field of view according to the image height relationship of the adjacent half-field angles, so that the sampling rate of the central field of view is higher than the edge, which reduces costs and is simple and easy to implement.

Further, in an embodiment of the present invention, the collection module 100 further includes: a collection unit and a selection unit. The collection unit is configured to collect a maximum field angle of the wide-angle lens and a preset number of adjacent field angles. The selecting unit is configured to obtain a half field angle θ ₁ according to a maximum field angle of the wide-angle lens, and obtain half field angles θ ₂ to θ _n according to a preset number of adjacent field angles.

Further, in an embodiment of the present invention, the calculation module 300 further includes: a processing unit and a calculation unit. The processing unit is configured to perform sampling processing on the image heights r ₁ to r _n corresponding to the n half-view angles by using the field angle relation formula, wherein the sampling process adopts an interpolation method. The obtaining unit is used to obtain the image height relationship of adjacent half-field angles according to the view angle relationship.

Further, in an embodiment of the present invention, the field angle relationship is: And so on,

Further, in an embodiment of the present invention, the relationship between the image heights of adjacent half field angles is: In addition, according to the relationship between the image height corresponding to the maximum field angle and the image height relationship of adjacent half field angles, the image height of each half field angle is calculated recursively: Among them, r _(n-1) is the image height corresponding to the half field angle θ _(n-1) , r _n is the image height corresponding to the half field angle θ _n , β ₁ is the ratio of θ ₁ and θ ₂ , β ₂ is a ratio of θ ₂ and θ ₃ , and β _{( n -1)} is a ratio of θ _(n-1) and θ _n .

Further, in an embodiment of the present invention, the maximum field angle is greater than or equal to 70 °.

Further, in an embodiment of the present invention, the maximum field angle is 100 ° or more and 190 ° or less.

It should be noted that, the foregoing explanation of the embodiment of the method for correcting distortion of a wide-angle lens is also applicable to the device for correcting distortion of a wide-angle lens of this embodiment, and details are not described herein again.

According to the distortion correction device of the wide-angle lens provided by the embodiment of the present invention, the relationship between the image heights of adjacent half-field angles can be obtained according to the adjacent field-of-view ratio and the image height corresponding to the complex half-field angle, and according to the maximum field-of-view angle corresponding The relationship between the image height and the image height of adjacent half-field angles is calculated recursively to obtain the image height of each half-field angle, so that according to the image height of each half-field angle, the distortion of the wide-angle lens in the central field of view is corrected in order, and a wide-angle lens is realized. The sampling rate of the central field of view is higher than the edge, so that the resolution of the central field of view of the wide-angle lens can be quantitatively adjusted as the system needs, and the total length of the system can be reduced by increasing the incident angle of the light, making the entire system more compact.

In addition, an embodiment of the present invention also proposes a distortion correction system for a wide-angle lens. The system includes a wide-angle lens and a pixel sensor corrected by the distortion correction device of the wide-angle lens.

Further, in an embodiment of the present invention, the wide-angle lens corrected by using the distortion correction device includes a first lens, a second lens, a third lens, an aperture, a fourth lens, and a fifth lens in order from the object side to the image side. , Sixth lens, seventh lens, and filter.

Further, in an embodiment of the present invention, the first lens, the second lens, and the seventh lens are all aspheric lenses.

Further, in an embodiment of the present invention, the aspheric surface shapes of the first lens, the second lens, and the seventh lens all satisfy the following equations: Among them, z is the curvature corresponding to the radius, h is the radial coordinate, c is the curvature of the vertex of the surface, K is the conic quadric curve coefficient, and B, C, D, and E respectively represent fourth, sixth, eighth, and ten The coefficient corresponding to the radial coordinate of the first order.

It can be understood that, as shown in FIG. 4, the wide-angle lens for recursive distortion correction (the maximum field angle is 120 degrees) used in the embodiment of the present invention includes the first lens L1 and the second lens in order from the object side to the imaging surface. L2, third lens L3, aperture S1, fourth lens L4, fifth lens L5, sixth lens L6, seventh lens L7, filter S2, and first lens L1, second lens L2, seventh lens L7 Aspheric lens. The design parameters of each lens in the wide-angle lens of the embodiment of the present invention are shown in Table 3, and the aspheric parameters of each lens are shown in Table 4.

Further, as shown in FIG. 5, small x is a uniform sampling of the field of view by the main ray. After being projected onto the CMOS sensor, due to the existence of distortion, the entire deformation occurs, and as a result, there is not much distortion in the central part. A small x can correspond to a sample of about 9 pixels, so the resolution is high, while a small x on the side only corresponds to a sample of one pixel, and the resolution is low. The small black square in the figure represents a pixel. After downsampling, these small x will be evenly distributed, and the reconstructed image is shown in Figure 6. This resampling frequency can be calculated as ((30/21) * (60/30)) ^ 2 = 8.2. Therefore, the wide-angle lens provided by the embodiment of the present invention simultaneously achieves correction of distortion after resampling.

Table 5 is the corresponding image height and pixel parameters of the wide-angle lens provided in this embodiment at different half-field angles. As can be seen from Table 5, the theoretical values of the wide-angle lens of the embodiment of the invention and the recursive distortion correction method of the invention are basic. Consistent, it shows that the recursive distortion correction method of the embodiment of the present invention can effectively correct the distortion of the wide-angle lens in the central field of view, and the sampling rate of the central field of view can be higher than that of the edge. rate.

For example, in another embodiment of the present invention, by using a wide-angle lens with recursive distortion correction, and assuming a system of a 160-degree wide-angle lens and a 12.4MP CMOS sensor, if the central 42-degree field of view is still maintained The resolution is 2MP. According to Table 6, if the horizontal field of view is increased to 160 degrees, the pixels required by the sensor are 4802 * 2702, which is 12.4MP. In addition, if the horizontal field of view is maintained at 120 degrees, after the sensor is increased to 12 MP, the number of pixels in the central field of view of 42 degrees is also increased to 3 MP. Therefore, the development of next-generation wide-angle lens products can have two directions. One is to increase the field of view coverage and maintain the center resolution; the second is to maintain the field of view coverage and improve the center resolution. It should be noted that, in the embodiment of the present invention, a more suitable solution may be determined according to the development of the ADAS and the algorithm.

According to Table 6, when the HFOV reaches 160 degrees, if it is necessary to ensure 2MP coverage at the center of 42 degrees, the entire sensor pixel is 4802 * 2702 (that is, 12.4MP).

It should be noted that the foregoing explanation of the embodiment of the method for correcting the distortion of the wide-angle lens is also applicable to the distortion correction system of the wide-angle lens of this embodiment, and details are not described herein again.

According to the distortion correction system of the wide-angle lens according to the embodiment of the present invention, the image height relationship of the adjacent half-field angles can be obtained according to the adjacent field-of-view ratio and the image height corresponding to the complex half-field angle. The relationship between the image height and the image height of adjacent half-field angles is calculated recursively to obtain the image height of each half-field angle, so that according to the image height of each half-field angle, the distortion of the wide-angle lens in the central field of view is corrected in order, and a wide-angle lens is realized. The sampling rate of the central field of view is higher than the edge, so that the resolution of the central field of view of the wide-angle lens can be quantitatively adjusted according to the needs of the system, and the total angle of the system can be reduced by increasing the incident angle of the light, making the entire system more compact; through a high pixel The camera effectively replaces the complex low-pixel camera, saves the cost of ADAS system, simplifies the requirements of system correction and system calculation, improves the accuracy and reliability of correction, improves the correction efficiency, effectively reduces the cost, and is easy to implement.

In the description of the present invention, it should be understood that the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", " Rear "," left "," right "," vertical "," level "," top "," bottom "," inside "," outside "," clockwise "," counterclockwise "," axial ", The azimuth or position relationship indicated by "radial", "circumferential", etc. is based on the azimuth or position relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply the device or element referred to. Must have a specific approach Position, structure and operation in a specific orientation, so it cannot be understood as a limitation of the present invention.

In addition, the terms "first" and "second" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as “first” and “second” may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless it is specifically and specifically defined otherwise.

In the present invention, the terms "installation", "connected", "connected", "fixed" and other terms shall be understood in a broad sense unless otherwise specified and defined, for example, they may be fixed connections or removable connections , Or integrated; it can be mechanical or electrical; it can be directly connected or indirectly connected through an intermediate medium, it can be the internal connection of the two elements or the interaction between the two elements, unless otherwise specified The limit. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

In the present invention, unless explicitly stated and defined otherwise, the first feature "on" or "down" of the second feature may be the first and second features in direct contact, or the first and second features indirectly through an intermediate medium. contact. Moreover, the first feature is "above", "above", and "above" the second feature. The first feature is directly above or obliquely above the second feature, or simply indicates that the level of the first feature is higher than the second feature. The “below”, “below”, and “below” of the first feature may be directly below or obliquely below the second feature, or simply indicate that the level of the first feature is smaller than the second feature.

In the description of this specification, the description with reference to the terms “an embodiment”, “some embodiments”, “examples”, “specific examples”, or “some examples” and the like means specific features described in conjunction with the embodiments or examples , Structures, materials, or features are included in at least one embodiment or example of the present invention. In this specification, the schematic expressions of the above terms are not necessarily directed to the same embodiment or example. and, The specific features, structures, materials, or characteristics described may be combined in any suitable manner in any or multiple embodiments or examples. In addition, without any contradiction, those skilled in the art may combine and combine different embodiments or examples and features of the different embodiments or examples described in this specification.

Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limitations on the present invention. Those skilled in the art can interpret the above within the scope of the present invention. Embodiments are subject to change, modification, substitution, and modification.

Claims (13)

A method for correcting distortion of a wide-angle lens, comprising the following steps: obtaining n half-field angles θ ₁ to θ _{n of} a wide-angle lens, where θ _n is an adjacent half-field angle of θ _(n-1) , n and the half field angle θ ₁ to obtain [theta] _n of the adjacent fields of view according to a ratio β ₁ to β _{(n-1), n} is a positive integer; n the basis of the half field angle θ ₁ to [theta] _n Get the image heights r ₁ to r _n corresponding to the n half field angles; according to the adjacent field ratio β ₁ to β _(n-1) and the image heights r ₁ to r corresponding to the n half field angles _n Obtain the image height relationship of adjacent half field angles, and recursively calculate the image height of each half field angle according to the image height relationship corresponding to the maximum field angle and the image height relationship of the adjacent half field angle; And sequentially correct the distortion of the wide-angle lens in the central field of view according to the image height of each half field of view angle; wherein, according to the adjacent field of view ratios β ₁ to β _(n-1) corresponding to the n half field of view angles Obtaining the image height relationship of the adjacent half-field angles from the image heights r ₁ to r _n of the image height, further including: sampling the image heights r ₁ to r _n corresponding to the n half-field angles through a field angle relationship formula Processing, where, Sampling process using the interpolation method; obtain image height relationship adjacent half angle of view according to the viewing angle relationship; image height relationship of the adjacent half angle of view is: In addition, the image height of each half field angle is obtained by recursively calculating the relationship between the image height corresponding to the maximum field angle and the image height of the adjacent half field angle: Among them, r _(n-1) is the image height corresponding to the half field angle θ _(n-1) , r _n is the image height corresponding to the half field angle θ _n , β ₁ is the ratio of θ ₁ and θ ₂ , β ₂ is a ratio of θ ₂ and θ ₃ , and β _{( n -1)} is a ratio of θ _(n-1) and θ _n . The method for correcting distortion of a wide-angle lens according to item 1 of the scope of the patent application, wherein the obtaining of the n half-field angles θ ₁ to θ _{n of} the wide-angle lens further includes: collecting a maximum field angle and a preset number of the wide-angle lens And the half-field angle θ _{1 is} obtained according to the maximum field-angle of the wide-angle lens, and the half-field angles θ ₂ to θ _{n are} obtained according to the preset number of adjacent field angles. The distortion correction method of the wide-angle lens according to item 1 of the scope of patent application, wherein the field angle relationship is: And so on, The distortion correction method of the wide-angle lens according to item 2 of the scope of the patent application, wherein the maximum field angle is greater than or equal to 70 °. The distortion correction method for a wide-angle lens according to item 4 of the scope of the patent application, wherein the maximum field of view angle is 100 ° or more and 190 ° or less. A distortion correction device for a wide-angle lens, comprising: a collection module for obtaining n half field angles θ ₁ to θ _{n of} a wide-angle lens, where θ _n is a phase of θ _(n-1) Adjacent half field angles, and obtain the adjacent field ratios β ₁ to β _(n-1) according to the n half field angles θ ₁ to θ _n , where n is a positive integer; an acquisition module is used to The n half-field angles θ ₁ to θ _n obtain the image heights r ₁ to r _n corresponding to the n half-field angles; a calculation module is configured to use the adjacent field-of-view ratios β ₁ to β _{(n -1)} The image heights r ₁ to r _n corresponding to the n half-field angles are used to obtain the image height relationship of the adjacent half-field angles, and according to the image height corresponding to the maximum field angle and the adjacent half-field angles The image height relationship of is obtained by recursively calculating the image height of each half field of view angle; and a correction module for sequentially correcting the distortion of the wide-angle lens in the central field of view according to the image height of each half field of view angle; wherein, The calculation module further includes: a processing unit, configured to perform a sampling process on the image heights r ₁ to r _n corresponding to the n half field angles according to the field angle relationship, wherein the sampling place Interpolation method is used; an acquisition unit is used to obtain the image height relation of adjacent half field angles according to the field angle relation; the image height relation of adjacent half field angles is: In addition, the image height of each half field angle is obtained by recursively calculating the relationship between the image height corresponding to the maximum field angle and the image height of the adjacent half field angle: Among them, r _(n-1) is the image height corresponding to the half field angle θ _(n-1) , r _n is the image height corresponding to the half field angle θ _n , β ₁ is the ratio of θ ₁ and θ ₂ , β ₂ is a ratio of θ ₂ and θ ₃ , and β _{( n -1)} is a ratio of θ _(n-1) and θ _n . The distortion correction device for a wide-angle lens according to item 6 of the scope of patent application, wherein the collection module further includes: a collection unit for collecting a maximum field angle of the wide-angle lens and the preset number of adjacent Field of view angle; a selection unit for obtaining the half field angle θ ₁ according to the maximum field angle of the wide-angle lens, and obtaining half field angles θ ₂ to θ _n according to the preset number of adjacent field angles . The distortion correction device for a wide-angle lens according to item 6 of the scope of patent application, wherein the field angle relationship is: And so on, The distortion correction device for a wide-angle lens according to item 7 of the scope of the patent application, wherein the maximum field angle is greater than or equal to 70 °. The distortion correction device for a wide-angle lens according to item 9 of the scope of the patent application, wherein the maximum field of view angle is 100 ° or more and 190 ° or less. A distortion correction system for a wide-angle lens, comprising: a wide-angle lens and a pixel sensor corrected by the distortion correction device of the wide-angle lens according to any one of claims 6 to 10 of the scope of patent application. The distortion correction system of the wide-angle lens according to item 11 of the scope of the patent application, wherein the wide-angle lens corrected by the distortion correction device of the wide-angle lens includes a first lens, a second lens, and a third lens in order from the object side to the image side. , An aperture, a fourth lens, a fifth lens, a sixth lens, a seventh lens, and a filter. The distortion correction system of the wide-angle lens according to item 12 of the scope of the patent application, wherein the first lens, the second lens, and the seventh lens are all aspherical lenses.