Image pickup system capable of expanding transverse visual field

Abstract

The utility model discloses a transverse visual field expanding camera system comprising an image acquisition unit and an imaging lens, and the imaging lens is arranged in front of the image acquisition unit; the position relation between the image acquisition unit and the imaging lens is set, so that the center of the imaging lens deviates in the horizontal direction relative to the center of the image acquisition unit; the plane where the imaging lens or / and the image acquisition unit are located is inclined in the deflection direction, so that the plane where the imaging lens is located and the plane where the image acquisition unit is located form a preset included angle and extend to intersect at an intersection line, and the intersection line is located on the side portions of the imaging lens and the image acquisition unit and is close to the side of a target view area. According to the camera system, view field adjustment can be realized without inclination of the main body, and the problems of perspective deformation, magnification imbalance and the like caused by overall inclination of the camera due to the view field requirement of the side part of the camera are solved.

Description

Technical Field

[0001] The utility model relates to the field of cameras, in particular to a camera system for expanding the horizontal field of view. Background Art

[0002] When a camera system is shooting, the usual shooting method is that the camera faces the object to be photographed directly, and the object plane is parallel to the image plane. This shooting method is called "forward shooting". However, in some specific application scenarios, this "forward shooting" cannot bring the best shooting and application effects. For example, when the left and right of the field of view area are not symmetrical, or there is a lateral offset between the target object and the camera system, the camera must be tilted for shooting. At this time, the perspective distortion of the object to be photographed will occur, affecting parameters such as aspect ratio and magnification.

[0003] For example, for a vehicle-mounted camera system, with the development of electronic camera technology, more and more vehicles are equipped with auxiliary camera devices. However, on the side close to the vehicle body, due to being blocked by the vehicle body, this part of the field of view has no practical effect on improving the field of view in application. On the contrary, the field of view on the side far from the vehicle body is more valuable to the driver. If a wider field of view on the side far from the vehicle body is to be photographed, the camera will be installed non-forwardly tilted outward from the vehicle body. Such an installation method causes the focal plane of the camera and the object to be photographed not to be in the same plane, and the image obtained by shooting needs to be presented to the driver through the screen. The sense of distance obtained after tilting outward is different from the sense of distance obtained by shooting directly backward. And in such a shooting method, perspective distortion of the object to be photographed will appear in the image, seriously affecting parameters such as aspect ratio, magnification, and MTF of the image.

[0004] Taking a grid test board as an example; when the vertical grid board is tilted and photographed, the center of the lens optical axis and the center of the grid test board are displaced, and the grid board in the image shows perspective distortion of being larger at the top, smaller at the bottom, smaller on the left, and larger on the right (which is called vertical convergence distortion and horizontal convergence distortion in the photography field), and the aspect ratio and magnification are unbalanced.

[0005] When the camera is tilted and installed, the magnification and aspect ratio of the object in the photographed image are unbalanced, and the image must be corrected by software. The writing of software code is labor-intensive and costly, and the operation requires large computing power support. Large computing power chips will reduce the optional models and increase the purchase cost. At the same time, large computing power means increased power consumption, and thermal management is a pain point in the design of electronic systems. And the operation of a large number of graphic codes will increase the probability of the product having BUGs. Summary of the Utility Model

[0006] In view of the above problems, the present utility model aims to provide a camera system that can achieve lateral field of view adjustment without the need for the main body of the camera system to swing outward for shooting. While meeting the requirements of the field of view change, it can reduce problems such as perspective distortion and magnification imbalance caused by tilting the camera body to meet the field of view requirements for shooting by swinging the camera to one side. The camera system of the present utility model can save resources of the image acquisition unit and reduce the workload of writing and developing image correction software code.

[0007] Principle description

[0008] During the research and development process, the inventor noticed that in the rear-view camera device, the field of view requirements for the outer side and the rear of the vehicle are greater than those for the inner side of the vehicle (the limit field of view on the inner side is the vehicle body, and the area more inside is blocked by the vehicle body, and this field of view area has no practical significance for driving).

[0009] In order to obtain a wider field of view outside the vehicle, it is often necessary to tilt the rear-view camera outward, which in turn brings the problem of perspective distortion. In order to reduce the problem of perspective distortion and increase the field of view range outside the camera device, the inventor proposed a camera shooting method of forward shooting and offset imaging.

[0010] That is, first, an imaging lens with a large clear imaging circle area 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). Then, it is allowed that the image acquisition unit performs a certain translation operation on the rear focal plane of the imaging lens, so that the imaging collected at the outermost edge position of the offset image acquisition unit within the clear imaging circle still meets the image quality requirements in terms of parameters such as distortion and MTF value.

[0011] Then, the positional relationship between the imaging lens and the image acquisition unit is adjusted so that the image acquisition unit has an offset in the horizontal (left or right) direction relative to the imaging lens. Specifically, usually, the imaging lens and the image acquisition unit are coaxial, and the projection of the optical axis of the imaging lens on the image acquisition unit is located at the center of the image acquisition unit. 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 on 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.

[0012] Finally, in order to obtain a greater depth of field within the target field of view area, that is, in order to make the imaging of a larger range of scenes clearer within the required field of view area, one of the imaging lens and the image acquisition unit is set to be slightly yawed, that is, the imaging lens is slightly deflected in the lateral direction relative to the image acquisition unit, or the image acquisition unit is slightly deflected in the lateral direction relative to the imaging lens, so that the planes where they are located are not completely parallel, but there is a small included angle, and the intersection line of the two planes is located on the left or right side of the two, which depends on which side of the vehicle it is installed on. In short, this intersection line is far from the vehicle body and closer to the target field of view side to be photographed (for example, in order to obtain more left-side views, then this intersection line is located on the left side of the image acquisition unit and the imaging lens). Preferably, the object-side focal plane of the imaging system (that is, the plane of the object to be photographed), the plane where the imaging lens is located, and the plane where the image acquisition unit is located intersect at this intersection line, and further, the setting methods of the image acquisition unit and the imaging lens satisfy the Scheimpflug's law.

[0013] With this setting method, the object-side focal plane of the imaging system will extend forward from the intersection line of the imaging system (such as the left intersection line) to obtain a larger effective and clear imaging range.

[0014] Based on the above principle, this patent provides a camera system for expanding the lateral field of view, including an image acquisition unit and an imaging lens, and the imaging lens is arranged in front of the image acquisition unit; the positional relationship between the image acquisition unit and the imaging lens is set so that the center of the imaging lens has a horizontal offset relative to the center of the image acquisition unit; and the plane where the imaging lens or / and the image acquisition unit is located has an inclination in the yaw direction, so that the plane where the imaging lens is located and the plane where the image acquisition unit is located form a predetermined included angle, and then extend and intersect at an intersection line, and 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.

[0015] In a preferred implementation, the object-side focal plane of the imaging system intersects the plane where the imaging lens is located and the plane where the image acquisition unit is located at this intersection line.

[0016] 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.

[0017] 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.

[0018] In another preferred implementation, the center of the imaging lens has a vertical offset relative to the center of the image acquisition unit.

[0019] In another preferred implementation, the included angle of the yaw direction generated by the tilt between the imaging lens and / or the image acquisition unit is 0.1 - 5 degrees, and the distance Y0 of the horizontal position offset is 0.1 - 5 mm.

[0020] In another preferred implementation, the distance OO’ of the horizontal position offset ≥ f2(γ + δ), where f2 is the relationship function between the image width and the lateral field of view angle of the imaging lens at the current position of the image acquisition unit, γ is the included angle between the optical axis of the imaging lens and the edge of the lateral field of view in the horizontal plane, and δ is the included angle between the plane where the imaging lens is located and the plane where the image acquisition unit is located.

[0021] In another preferred implementation, the predetermined multiple is 1.2 - 2.5 times.

[0022] In another preferred implementation, the predetermined multiple is 1.3 - 2 times.

[0023] In another preferred implementation, the imaging system is set to face forward for shooting.

[0024] In another preferred implementation, the imaging system is a vehicle-mounted imaging system. When the vehicle-mounted imaging system is installed on the left side of the vehicle body, the image acquisition unit shifts to the right or the imaging lens shifts 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 imaging system is installed on the right side of the vehicle body, the image acquisition unit shifts to the left or the imaging lens shifts to the right, and the intersection line is located on the right side of the imaging lens and the image acquisition unit.

[0025] The forward setting here is the forward direction relative to the main shooting area. Taking the rearview mirror as an example, the main shooting area of the rearview mirror camera is directly behind, so the directly behind is defined as the forward direction. In other application scenarios, its main shooting direction can be defined as the forward direction.

[0026] It should be noted that the "intersection line" of the object-side focal plane of the imaging system, the plane where the imaging lens is located, and the plane where the image acquisition unit is located mentioned in the present invention is not an ideal intersection line, and a certain error is allowed. It means that the planes of the three generally intersect at a straight line, and this intersection line can have a certain range interval.

[0027] In this application, "the side of the intersection line close to the target field of view area" refers to the side where the intersection line of the planes of the image acquisition unit and the imaging lens is located on the side where the user hopes to capture more scenes. For example, for the left rearview mirror, the user hopes to capture more scenes of the imaging system or the left side of the vehicle, and the intersection line is located on the left side of the imaging system, and so on.

[0028] The "plane where 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.

[0029] It should be noted that the "deflection" mentioned in this application refers to the rotation around the vertical rotation axis.

[0030] The "offset" mentioned in this application refers to the translation relative to each other within the plane of the image acquisition unit and the imaging lens installation plane, and the translation direction is perpendicular to the main axis of one of them, and it can be adjusted according to the specific installation method of the camera.

[0031] 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 imaging system is offset to the left or right relative to the intersection point of the optical axis of the imaging lens and the plane where the image acquisition unit is located, which is to provide more fields of view on the left or right side of the vehicle. However, when those skilled in the art apply it to other scenarios, they can adjust the direction and angle of the horizontal offset according to the specific application scenario.

[0032] Those skilled in the art should understand that since the 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.

[0033] Beneficial effects

[0034] By using the imaging device with the lateral field of view expansion setting of the present utility model, the field of view adjustment can be achieved without the need for the overall lateral yaw of the imaging system, which can reduce problems such as perspective distortion and magnification ratio imbalance caused by having to tilt the camera due to the need for the field of view on the side of the camera.

[0035] This patent adopts the horizontal translation to replace the current operation of the overall outward yaw of the existing camera, reduces the perspective distortion problem caused by the overall yaw operation and realizes the outward movement of the target field of view area. By using the imaging device with the field of view offset setting of the present utility model, the effective area of the image acquisition unit can be maximally utilized. Brief description of the drawings

[0036] Figure 1 It is a schematic diagram of the positional relationship between the lens and the image acquisition unit in an existing ordinary camera. Figure 1 The upper part in is a schematic view (or front view) seen from the direction of the image acquisition unit towards the lens; the lower part is a schematic top view section.

[0037] Figure 2 It is a schematic diagram of the positional relationship between the lens and the image acquisition unit in the vehicle-mounted imaging device in Embodiment 1 of this application. Figure 2The upper left figure is a schematic diagram of the positional relationship between the image acquisition unit and the lens when looking from the image acquisition unit towards the lens direction (or the front view); the lower figure is a top view schematic diagram, and the upper right figure is a left view schematic diagram (the same hereinafter);

[0038] Figure 3 It is a schematic diagram of the positional relationship between the image acquisition unit and the clear imaging circle of the imaging lens.

[0039] Figure 4 It is the actual effect diagram taken by the forward shooting using the existing technology;

[0040] Figure 5 The actual effect diagram taken by the shooting method in Embodiment 1 ( Figure 2 layout method, horizontal translation);

[0041] Figure 6 It is a schematic diagram of the layout of the imaging lens relative to the image acquisition unit in Embodiment 2 of the present invention;

[0042] Figure 7 It is the actual effect diagram taken by the shooting method in Embodiment 2 (horizontal translation + yaw);

[0043] Figure 8 It is a schematic diagram of the layout of the imaging lens relative to the image acquisition unit in Embodiment 3 of the present invention;

[0044] Figure 9 It is the actual effect diagram taken by the shooting method in Embodiment 3 (horizontal translation + upward offset + yaw and satisfying the Scheimpflug's law);

[0045] Figure 10 It is a schematic diagram for determining the yaw angle. Detailed implementation mode

[0046] The present invention will be further described in detail below in conjunction with the embodiments and the accompanying drawings, but the implementation manners of the present invention are not limited thereto.

[0047] Figure 1 The figure shows the positional relationship between the lens and the image acquisition unit in the existing camera device. It can be seen from the figure that the center of the lens 30 in the existing camera device is horizontally aligned with the center of the image acquisition unit, and there is no horizontal offset of the lens 30 relative to the center of the image acquisition unit 20.

[0048] Embodiment 1

[0049] Figure 2 It is a schematic diagram showing the positional relationship between the lens and the image acquisition unit in the vehicle-mounted camera device with offset setting in Embodiment 1 of the present invention, and the image acquisition unit is offset to the left.

[0050] The camera device for expanding the horizontal field of view in 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 in the housing of the camera. An installation substrate is provided in the middle or rear of the housing of the camera, and an image acquisition unit installation position is provided on the camera main board. The image acquisition unit 20 is installed at the image acquisition unit installation position.

[0051] As Figure 3 shown is a schematic diagram of the relationship between the clear imaging circle and the image acquisition unit. Compared with the existing camera device, 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 more than 1.3 times the diagonal length of the image acquisition unit. Here, a circular lens and a rectangular image acquisition unit are taken as examples for description. If lenses and image acquisition units of other shapes 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 range. And for the imaging collected at the outermost edge position of the image acquisition unit after offset within the clear imaging circle, parameters such as its distortion and MTF value still meet the image quality requirements.

[0052] The position O' of the center of the lens 30 projected horizontally on the image acquisition unit 20 does not coincide with the center O of the image acquisition unit. The center of the image acquisition unit is offset to the left relative to the position of the center of the lens 30 projected horizontally on the image acquisition unit 20. The connection line between O and O' is the offset amount of the image acquisition unit 20.

[0053] The offset distance OO' in the horizontal position ≥ f2(γ + δ), where f2 is the relationship function between the image width formed by the imaging lens at the current position of the image acquisition unit and the horizontal field of view angle, γ is the angle between the optical axis of the imaging lens and the edge of the side 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 ). Usually, the offset distance OO' in the horizontal position is 0.1 - 5 mm.

[0054] Actually, γ + δ is the angle between the forward direction of the camera system and the edge of the left field of view in the horizontal plane.

[0055] Figure 3 It can be seen from

[0056] This offset is predetermined during the camera design and is implemented when installing the imaging lens and the image acquisition unit. This offset is achieved by translating the imaging lens or the image acquisition unit. In this embodiment, the translation of the image acquisition unit is taken as an example for description, but those skilled in the art should understand that this translation can also be achieved by translating the imaging lens.

[0057] Specifically, during the design, 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.

[0058] In this application, all the actual effect diagrams are taken under the same real scene layout conditions. Two letter identification blocks, six cones, and a checkerboard are set in the target area.

[0059] Comparison Figure 4 and Figure 5 It can be seen that Figure 4 when shooting forward, the right-side picture in Figure 5 is less than the right-side picture in

[0060] In contrast, Figure 5 after the image acquisition unit is horizontally offset to the left in

[0061] Embodiment 2

[0062] As Figure 6 shown is 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, and at the same time, the imaging lens has a rightward rotation angle, that is, one of them undergoes a yaw (rotates by an angle around the vertical axis passing through the center). Preferably, when adjusting the yaw 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 imaging system generally intersect at an intersection line, so that the Scheimpflug law can be satisfied and the largest clear imaging area can be obtained.

[0063] Figure 7 For Figure 6 is the actual shooting effect after the image acquisition unit is horizontally offset to the left and the imaging lens has a rightward yaw angle in

[0064] It can be seen from the figure that not only can the projection on the right-side wall be photographed, but also the clarity of the projection on the right-side wall is significantly improved.

[0065] Embodiment 3

[0066] As shown Figure 8 in the schematic diagram of the positional relationship between the imaging lens and the image acquisition unit in Embodiment 3 of the present application. In this embodiment, not only does the image acquisition unit shift to the left, but the imaging lens has an inclination angle to the right, that is, one of them undergoes a yaw change, and the image acquisition unit shifts upward.

[0067] Figure 9 This is the actual shooting effect after the image acquisition unit shifts horizontally to the left (in this embodiment, the yaw angle is 1.5 degrees), shifts upward, and the imaging lens has a downward viewing angle. Compared with Figure 7 it, it can capture more scenes below, it can capture the two closest traffic cones to the camera system, it can capture the first letter logo in the front, and the letter logo below and the wall image on the right are relatively Figure 5 all clearer.

[0068] Figure 10 is the angular relationship 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 the lens yaws, AC represents the desired field of view edge on the right, and AD represents the required 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.

[0069] In summary, it can be seen that by using the camera system with translation and yaw of the present application, high-definition images can be obtained, the effective field of view area can be expanded, the clarity of the edge field of view can be improved, perspective distortion can be reduced, and the resources of the image acquisition unit can be saved, and the delay caused by video processing can be reduced.

[0070] Although the principle of the present invention has been described in detail above in conjunction with the preferred embodiments of the present invention, those skilled in the art should understand that the above embodiments are only explanations of the illustrative implementation manners of the present invention, and do not limit the scope of the present invention. The details in the embodiments do not constitute a limitation on the scope of the present invention. Without departing from the spirit and scope of the present invention, any obvious changes such as equivalent transformations and simple substitutions based on the technical solution of the present invention all fall within the protection scope of the present invention.

Claims

1. A camera system with a lateral field of view expansion, characterized in that: It includes an image acquisition unit and an imaging lens, wherein the imaging lens is arranged in front of the image acquisition unit; The positional relationship between the image acquisition unit and the imaging lens is set so that the center of the imaging lens is offset in the horizontal direction relative to the center of the image acquisition unit; and the plane where the imaging lens and / or the image acquisition unit are located is tilted in the yaw 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, and then extend to intersect at an intersection line, and the intersection line is located at the side of the imaging lens and the image acquisition unit, close to the target field of view area.

2. The camera system with lateral field of view expansion according to claim 1, characterized in that: The object focal plane of the camera system intersects with 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 expansion 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 image acquisition unit after displacement can still fall within the clear imaging circle of the imaging lens.

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

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

6. The camera system with lateral field of view expansion according to claim 1, characterized in that: The distance OO' of the horizontal position offset is ≥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 edge of the side 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.

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

9. The camera system with lateral field of view expansion according to claim 1, characterized in that: The camera system is set forward to take pictures.

10. The camera system with lateral field of view expansion 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 at 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 at the right side of the imaging lens and the image acquisition unit.

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