Laterally expanded field-of-view camera system

Abstract

The present application discloses a laterally expanded field-of-view camera system, comprising an image acquisition unit and an imaging lens, wherein the imaging lens is arranged in front of the image acquisition unit. A positional relationship between the image acquisition unit and the imaging lens is configured so that the center of the imaging lens is offset horizontally relative to the center of the image acquisition unit; and the plane where the imaging lens is located and / or the plane where the image acquisition unit is located is tilted in a pan direction, so that the plane where the imaging lens is located and the plane where the image acquisition unit is located form a predetermined angle, thereby extending to intersect at an intersection line, and the intersection line is located at one side of the imaging lens and the image acquisition unit, close to the side of a target field-of-view region. The camera system of the present application can achieve field-of-view adjustment without tilting a main body, thereby solving the problems such as perspective distortion and magnification imbalance caused by the necessity of tilting an entire camera to meet the field-of-view requirement on a side of the camera.

Description

A camera system with extended lateral field of view

[0001] Related applications

[0002] This application claims priority to Chinese patent application 202422072653.2, filed on August 26, 2024, entitled "A Camera System with Lateral Field of View." Technical Field

[0003] This application relates to the field of photography, specifically to a camera system with lateral field of view extension. Background Technology

[0004] When a camera system takes pictures, the camera is usually positioned directly facing the subject, with the object plane and image plane parallel. This shooting method is called "front-facing shooting." However, in certain application scenarios, this "front-facing shooting" does not provide the best shooting and application results. For example, when the field of view is not symmetrical, or when there is a lateral offset between the target object and the camera system, the camera must be tilted to shoot. In this case, perspective distortion will occur in the image of the subject, affecting parameters such as aspect ratio and magnification.

[0005] For example, with the development of electronic camera technology, more and more vehicles are adding auxiliary camera equipment for in-vehicle camera systems. However, the view closest to the vehicle body is often obstructed, rendering it ineffective in improving the driver's field of vision. Conversely, the view further away from the vehicle body is more valuable to the driver. To capture a wider view away from the vehicle body, the camera is often installed off-center, tilted to the outside. This installation method causes the camera's focal plane to be out of sync with the subject. Furthermore, since the image is displayed to the driver on a screen, the sense of distance obtained by tilting the camera outwards differs from that obtained by shooting directly backwards, potentially misleading the driver and causing them to misjudge distances. Additionally, this shooting method results in perspective distortion of the subject in the image, severely affecting parameters such as aspect ratio, magnification, and MTF.

[0006] Taking a grid test board as an example; when shooting at an angle towards a vertical grid test board, the center of the lens optical axis will shift from the center of the grid test board. As a result, the grid test board will appear larger at the top and smaller at the bottom, and smaller on the left and larger on the right in the image (which is called vertical convergence distortion and horizontal convergence distortion in the photography world). The aspect ratio and magnification will also be unbalanced.

[0007] If a camera is installed at an angle, the magnification and aspect ratio of objects in the captured image will be unbalanced. The image must be corrected by software, which requires significant manpower and financial resources to write the software code and more computing power to run. High-performance chips reduce the available models and increase purchase costs. At the same time, high computing power means increased power consumption, and thermal management is a pain point in electronic system design. Furthermore, running a large amount of graphics code increases the likelihood of product bugs.

[0008] Application content

[0009] To address the aforementioned problems, this application aims to provide a camera system that can achieve lateral adjustment of the field of view without requiring the camera body to be tilted outwards (rotated) for shooting. This system can meet the changing field of view while reducing perspective distortion and magnification imbalance caused by tilting the camera body to one side to meet the shooting field of view requirements. The camera system of this application can save image acquisition unit resources and reduce the workload of writing and developing image correction software code.

[0010] Principle Explanation

[0011] During the research and development process, the inventors noticed that the rearview camera device has a greater need for a field of view to the outside and rear of the vehicle than for the inside of the vehicle (the limit of the field of view to the inside is the vehicle body, and the area further inside is blocked by the vehicle body, and this field of view is not of practical significance for driving).

[0012] To obtain a wider field of view of the vehicle, the rearview camera often needs to be tilted outwards, which leads to perspective distortion. To reduce perspective distortion while increasing the field of view of the camera device, the inventors proposed a forward-facing, offset imaging method.

[0013] That is, firstly, an imaging lens with a larger area of ​​clear imaging circle is selected, so that the diameter of the clear imaging circle of the imaging lens is greater than k times the diagonal length of the image acquisition unit (k is a proportionality coefficient, a constant greater than 1, preferably set to 1.2-2.5, more preferably 1.3), thereby allowing the image acquisition unit to perform a certain translation operation on the back focal plane of the imaging lens, so that the image acquired at the edge position of the image acquisition unit after being offset within the clear imaging circle still meets the image quality requirements in terms of distortion, MTF value and other parameters.

[0014] Then, the positional relationship between the imaging lens and the image acquisition unit is adjusted so that the image acquisition unit is offset horizontally (to the left or right) relative to the imaging lens. Specifically, normally the imaging lens and the image acquisition unit are coaxial, and the projection of the optical axis of the imaging lens onto the image acquisition unit is located at the center of the image acquisition unit. However, in this patent, the image acquisition unit is horizontally offset relative to the imaging lens, so that the center of the imaging lens is located to the side of the center of the image acquisition unit in the horizontal direction. This relative offset can also be achieved by translating the imaging lens in the opposite direction relative to the image acquisition unit.

[0015] Finally, to obtain a greater depth of field within the target field of view, i.e., to achieve clearer imaging of a wider range of objects within the required field of view, a slight offset (also known as deflection) is made between the imaging lens and the image acquisition unit. Specifically, the imaging lens is slightly offset to the side relative to the image acquisition unit, or vice versa, so that their planes are not perfectly parallel but have a small angle. The line of intersection of their planes is located to the left or right of each other, depending on which side of the vehicle they are mounted on. In short, this line of intersection is away from the vehicle body and closer to the side of the target field of view to be captured (for example, to obtain a wider left-hand field of view, the line of intersection is located to the left of both the image acquisition unit and the imaging lens; in vehicle-mounted camera systems, left and right refer to left and right when the driver's direction is forward). Preferably, the object-side focal plane of the camera system (i.e., the plane of the subject), the plane of the imaging lens, and the plane of the image acquisition unit intersect at this line of intersection, thus ensuring that the arrangement of the image acquisition unit and the imaging lens satisfies Scherm's Law.

[0016] With this setup, the object-side focal plane of the camera system will extend from the intersection line of the camera system (e.g., the left intersection line) to the front of the camera system, resulting in a larger effective and clear imaging range.

[0017] Based on the above principles, this patent provides a camera system for lateral field of view expansion, including an image acquisition unit and an imaging lens, with the imaging lens positioned in front of the image acquisition unit. The positional relationship between the image acquisition unit and the imaging lens is configured such that the center of the imaging lens is horizontally offset relative to the center of the image acquisition unit. Furthermore, the plane where the imaging lens and / or the image acquisition unit are located is tilted in a yaw direction, such that the plane where the imaging lens is located and the plane where the image acquisition unit is located form a predetermined angle, thereby extending and intersecting at an intersection line. This intersection line is located on the side of the imaging lens and the image acquisition unit, closer to the target field of view area.

[0018] In a preferred implementation, the object-side focal plane of the camera system intersects the plane where the imaging lens is located and the plane where the image acquisition unit is located at the intersection line.

[0019] In another preferred implementation, the center of the imaging lens is offset to the left or right relative to the center of the image acquisition unit.

[0020] In another preferred implementation, the diameter of the clear imaging circle of the imaging lens is greater than or equal to a predetermined multiple of the diagonal length of the image acquisition unit, so that the offset image acquisition unit can still fall within the clear imaging circle of the imaging lens.

[0021] In another preferred implementation, the center of the imaging lens is offset vertically relative to the center of the image acquisition unit.

[0022] In another preferred implementation, the angle between the imaging lens and / or the image acquisition unit due to tilt is 0.1-5 degrees, and the horizontal position offset distance Y0 is 0.1-5 mm.

[0023] In another preferred implementation, the horizontal position offset distance OO' ≥ f2(γ+δ), where f2 is the relationship function between the image width of the imaging lens at the current image acquisition unit position and the horizontal field of view, γ is the angle between the optical axis of the imaging lens and the side field of view edge in the horizontal plane, and δ is the angle between the plane where the imaging lens is located and the plane where the image acquisition unit is located.

[0024] In another preferred implementation, the predetermined multiple is 1.2-2.5 times.

[0025] In another preferred implementation, the predetermined multiple is 1.3-2 times.

[0026] In another preferred implementation, the camera system is positioned facing forward to take pictures.

[0027] In another preferred implementation, the camera system is a vehicle-mounted camera system. When the vehicle-mounted camera system is installed on the left side of the vehicle body (shooting backwards), the image acquisition unit is offset to the right or the imaging lens is offset to the left, and the intersection line is located on the left side of the imaging lens and the image acquisition unit. When the vehicle-mounted camera system is installed on the right side of the vehicle body (shooting backwards), the image acquisition unit is offset to the left or the imaging lens is offset to the right, and the intersection line is located on the right side of the imaging lens and the image acquisition unit.

[0028] The "positive" setting here refers to the positive direction relative to the main shooting area. Taking a rearview mirror as an example, the main shooting area of ​​the rearview mirror camera is directly behind it; therefore, directly behind is defined as positive. In other application scenarios, its main shooting direction can be defined as positive.

[0029] It should be noted that the "intersection line" of the object focal plane of the camera system, the plane where the imaging lens is located, and the plane where the image acquisition unit is located mentioned in this application is not an ideal intersection line. A certain degree of error is allowed. It means that the planes where the three are located roughly intersect a straight line, and this intersection line can have a certain range.

[0030] In this application, "the intersection line is closer to the target field of view" means that the intersection line of the plane where the image acquisition unit and the imaging lens are located is located on the side where the user wants to capture more of the scene. For example, for the left rearview mirror, if the user wants to capture more of the scene on the left side of the imaging system or the vehicle, the intersection line is located on the left side of the imaging system, and so on.

[0031] The "plane in which the imaging lens is located" refers to the plane that passes through the center of the imaging lens and is perpendicular to the optical axis of the imaging lens.

[0032] It should be noted that the term "deflection" in this application refers to rotation about a vertical axis of rotation.

[0033] The “offset” mentioned in this application refers to the relative translation between the image acquisition unit and the imaging lens in the mounting plane, with the translation direction perpendicular to the main axis of one of them, which can be adjusted according to the specific mounting method of the camera.

[0034] Of course, those skilled in the art should understand that in the embodiments of this application, the center of the image acquisition unit of the camera system is offset to the left or right relative to the intersection of the optical axis of the imaging lens and the plane where the image acquisition unit is located. This is to provide more field of view on the left or right side of the vehicle. However, those skilled in the art can adjust the direction and angle of the horizontal offset according to the specific application scenario when applying it to other scenarios.

[0035] Those skilled in the art should understand that, since offset is a relative concept, the offset of the image acquisition device relative to the main axis of the imaging lens can be achieved by moving the image acquisition unit or by moving the imaging lens in the opposite direction. Beneficial effects

[0036] The camera device using the lateral field-of-view expansion setting of this application can achieve field-of-view adjustment without tilting the entire camera system to the side. This can reduce problems such as perspective distortion and magnification imbalance caused by tilting the camera due to the need for a side view of the camera.

[0037] This patent employs horizontal translation to replace the outward tilting of existing cameras, reducing perspective distortion caused by overall tilting and shifting the target's field of view outward. The camera device using this field-of-view offset setting maximizes the effective area of ​​the image acquisition unit. Attached Figure Description

[0038] Figure 1 is a schematic diagram of the positional relationship between the lens and the image acquisition unit in an existing ordinary camera. The upper part of Figure 1 is a schematic view (or front view) looking from the image acquisition unit toward the lens; the lower part is a top cross-sectional view.

[0039] Figure 2 is a schematic diagram of the positional relationship between the lens and the image acquisition unit in the vehicle-mounted camera device in Embodiment 1 of this application. The upper left of Figure 2 is a schematic diagram of the positional relationship between the image acquisition unit and the lens as seen from the image acquisition unit toward the lens (or front view); the lower part is a top view; and the upper right part is a left view (the same below).

[0040] Figure 3 is a schematic diagram showing the positional relationship between the image acquisition unit and the clear imaging circle of the imaging lens.

[0041] Figure 4 shows the actual effect of the frontal shooting using existing technology;

[0042] Figure 5 shows the actual effect of the photo taken using the shooting method in Example 1 (the arrangement and horizontal translation in Figure 2).

[0043] Figure 6 is a schematic diagram of the arrangement of the imaging lens relative to the image acquisition unit in Embodiment 2 of this application;

[0044] Figure 7 shows the actual effect (horizontal translation + sway) captured using the shooting method in Example 2;

[0045] Figure 8 is a schematic diagram of the arrangement of the imaging lens relative to the image acquisition unit in Embodiment 3 of this application;

[0046] Figure 9 shows the actual effect of the shooting method in Example 3 (horizontal translation + upward offset + yaw and satisfying Scherm's Law);

[0047] Figure 10 is a schematic diagram showing the determination of the yaw angle. Detailed Implementation

[0048] The present application will be described in further detail below with reference to the embodiments and accompanying drawings, but the implementation of the present application is not limited thereto.

[0049] Figure 1 shows the positional relationship between the lens and the image acquisition unit in an existing camera device. As can be seen from the figure, the center of the lens 30 in the existing camera device is horizontally aligned with the center of the image acquisition unit, and the lens 30 has no horizontal offset relative to the center of the image acquisition unit 20.

[0050] Example 1

[0051] Figure 2 is a schematic diagram showing the positional relationship between the lens and the image acquisition unit in the offset vehicle-mounted camera device in Embodiment 1 of this application, wherein the image acquisition unit is offset to the left.

[0052] The lateral field-of-view extended camera device of this embodiment includes an image acquisition unit 20 and an imaging lens 30. The imaging lens 30 and the image acquisition unit 20 are sequentially installed inside the camera housing. A mounting base is provided in the middle or rear of the camera housing, and an image acquisition unit mounting position is provided on the camera mainboard, where the image acquisition unit 20 is mounted.

[0053] Figure 3 illustrates the relationship between the clear imaging circle and the image acquisition unit. Compared to existing camera devices, in this embodiment, the size (diameter) of the clear imaging circle of the lens 30 in the camera system is larger than the diagonal length of the image acquisition unit. Preferably, the diameter of the clear imaging circle of the lens is greater than 1.3 times the diagonal length of the image acquisition unit. This description uses a circular lens and a rectangular image acquisition unit as an example. If other shapes of lenses and image acquisition units are used, it is necessary to ensure that the maximum diagonal length of the imaging area is greater than a predetermined multiple of the maximum diagonal length of the image acquisition unit to ensure that the image acquisition unit can be translated within the imaging area. Furthermore, the image acquired at the outermost edge of the image acquisition unit after offset within the clear imaging circle still meets the image quality requirements in terms of distortion, MTF value, and other parameters.

[0054] The position O' of the horizontal projection of the center of lens 30 onto image acquisition unit 20 does not coincide with the center O of image acquisition unit. The center of image acquisition unit is offset to the left relative to the position of the horizontal projection of the center of lens 30 onto image acquisition unit 20. The line connecting O' and O' is the offset of image acquisition unit 20.

[0055] The horizontal position offset distance OO' ≥ f2(γ+δ), where f2 is the relationship function between the image width of the imaging lens at the current image acquisition unit position and the lateral field of view angle, γ is the angle between the optical axis of the imaging lens and the side edge of the field of view in the horizontal plane, and δ is the angle between the plane where the imaging lens is located and the plane where the image acquisition unit is located (see Figure 10). Typically, the horizontal position offset distance OO' is 0.1-5mm.

[0056] In fact, γ+δ is the angle between the direction directly in front of the camera system and the edge of the left field of view in the horizontal plane.

[0057] As shown in Figure 3, the size of the imaging circle is larger than the diagonal length of the image acquisition unit 20, so that it can move within the imaging circle. The position O' of the horizontal projection on the image acquisition unit 20 does not coincide with the center O of the image acquisition unit.

[0058] This offset is predetermined during camera design and is implemented when mounting the imaging lens and image acquisition unit. This offset is achieved by translating the imaging lens or image acquisition unit. In this embodiment, the translation of the image acquisition unit is used as an example; however, those skilled in the art should understand that this translation can also be achieved by translating the imaging lens.

[0059] Specifically, during the design process, the center of the image acquisition unit is offset horizontally relative to the center of the imaging lens, and the offset direction is generally perpendicular to the optical axis of the imaging lens.

[0060] All the actual renderings in this application were taken under the same real-world layout conditions, with the target area set with two letter marker blocks, six cones, and a grid board.

[0061] Comparing Figures 4 and 5, it can be seen that when shooting from the front in Figure 4, the right side of the image is less than the right side of the image in Figure 5.

[0062] In contrast, after the image acquisition unit in Figure 5 shifted horizontally to the left, more of the image was captured on the right side, allowing for the capture of more transparent images on the right wall. However, the image clarity on the right wall was slightly lower.

[0063] Example 2

[0064] Figure 6 shows a schematic diagram of the positional relationship between the imaging lens and the image acquisition unit in Embodiment 2 of this application. In this embodiment, the image acquisition unit is not only offset to the left, but the imaging lens also has a rotation angle to the right; that is, one of them is skewed (rotated by an angle around a vertical axis passing through the center). Preferably, when adjusting the skew angle, it is ensured that the plane where the imaging lens is located, the plane where the image acquisition unit is located, and the object-side focal plane of the camera system approximately intersect at a single line. This satisfies Scherm's Law and obtains the largest possible clear imaging area.

[0065] Figure 7 shows the actual shooting effect after the image acquisition unit in Figure 6 is horizontally shifted to the left and the imaging lens is tilted to the right. As can be seen from the figure, it can not only capture the projection on the right wall, but also the clarity of the projection on the right wall is significantly improved.

[0066] Based on the actual shooting results, the perspective distortion is less than that when the camera system is shooting at an overall angle.

[0067] Example 3

[0068] Figure 8 shows a schematic diagram of the positional relationship between the imaging lens and the image acquisition unit in Embodiment 3 of this application. In this embodiment, the image acquisition unit is not only shifted to the left, but the imaging lens also has a tilt angle to the right; that is, one of them undergoes a sway change, and the image acquisition unit is shifted upwards.

[0069] Figure 9 shows the actual shooting effect after the image acquisition unit is horizontally shifted to the left in this embodiment (the sway angle is 1.5 degrees in this embodiment), shifted upward, and the imaging lens has a top-down angle. Compared with Figure 7, it can capture more of the scenery below, it can capture the two cones closest to the camera system, it can capture the first letter sign at the foreground, and the letter sign below and the wall image on the right are clearer than in Figure 5.

[0070] Figure 10 shows the angular relationships in the vertical plane when the camera system is applied to a vehicle. A represents the lens center, AB represents the optical axis direction after lens tilt, AC represents the desired field of view edge on the right, and AD represents the desired field of view edge on the left. γ is the angle between the optical axis of the imaging lens and the side field of view edge in the horizontal plane, and δ is the angle between the plane where the imaging lens is located and the plane where the image acquisition unit is located.

[0071] In summary, it can be seen that the translation and tilting camera system of this application can obtain high-definition images, expand the effective field of view, improve the clarity of the edge field of view, reduce perspective distortion, save image acquisition unit resources, and reduce the latency caused by video processing.

[0072] Although the principles of this application have been described in detail above with reference to preferred embodiments, those skilled in the art should understand that the above embodiments are merely illustrative explanations of the implementation of this application and are not intended to limit the scope of this application. The details in the embodiments do not constitute a limitation on the scope of this application. Any obvious changes, such as equivalent transformations or simple substitutions, based on the technical solutions of this application without departing from the spirit and scope of this application fall within the protection scope of this application.

Claims

1. A camera system with extended lateral field of view, characterized in that, It includes an image acquisition unit and an imaging lens, with the imaging lens positioned in front of the image acquisition unit; The positional relationship between the image acquisition unit and the imaging lens is configured such that the center of the imaging lens is offset horizontally relative to the center of the image acquisition unit; and the plane on which the imaging lens and / or the image acquisition unit are located is tilted in a yaw direction, so that the plane on which the imaging lens is located and the plane on which the image acquisition unit is located form a predetermined angle, and then extend to intersect at a line of intersection, which is located on the side of the imaging lens and the image acquisition unit, closer to the target field of view.

2. The camera system with lateral field of view extension according to claim 1, characterized in that, The object-side focal plane of the camera system intersects the plane where the imaging lens is located and the plane where the image acquisition unit is located at the intersection line.

3. The camera system with lateral field of view extension according to claim 1, characterized in that, The diameter of the clear imaging circle of the imaging lens is greater than or equal to a predetermined multiple of the diagonal length of the image acquisition unit, so that the offset image acquisition unit can still fall within the clear imaging circle of the imaging lens.

4. The camera system with lateral field of view extension according to claim 1, characterized in that, The center of the imaging lens is offset vertically relative to the center of the image acquisition unit.

5. The camera system with lateral field of view extension according to claim 1, characterized in that, The angle between the imaging lens and / or the image acquisition unit due to tilt is 0.1-5 degrees, and the horizontal position offset distance Y0 is 0.1-5 mm.

6. The camera system with lateral field of view extension according to claim 1, characterized in that, The horizontal position offset distance OO'≥f2(γ+δ), where f2 is the relationship function between the image width of the imaging lens at the current image acquisition unit position and the horizontal field of view angle, γ is the angle between the optical axis of the imaging lens and the side field of view edge in the horizontal plane, and δ is the angle between the plane where the imaging lens is located and the plane where the image acquisition unit is located.

7. The camera system with lateral field of view extension according to claim 3, characterized in that, The predetermined multiple is 1.2-2.5 times.

8. The camera system with lateral field of view extension according to claim 7, characterized in that, The predetermined multiple is 1.3-2 times.

9. The camera system with lateral field of view extension according to claim 1, characterized in that, The camera system is set to shoot from the forward direction.

10. The camera system with lateral field of view extension according to claim 1, characterized in that, The camera system is a vehicle-mounted camera system. When the vehicle-mounted camera system is installed on the left side of the vehicle body, the image acquisition unit is offset to the right or the imaging lens is offset to the left, and the intersection line is located on the left side of the imaging lens and the image acquisition unit. When the vehicle-mounted camera system is installed on the right side of the vehicle body, the image acquisition unit is offset to the left or the imaging lens is offset to the right, and the intersection line is located on the right side of the imaging lens and the image acquisition unit.

Images