Curved surface compound eye imaging system based on relay image rotation

Abstract

The invention relates to a curved-surface compound eye imaging system based on relay image rotation, and the system comprises a curved-surface compound eye structure which is a curved-surface micro-lens array composed of a plurality of micro-lenses; the relay image transfer system is used for converting a curved surface image formed on a focal curved surface of the curved surface micro-lens array into a plane image; and the plane receiver is used for receiving the plane image. According to the invention, the problem of conflict between the curved surface image collected by the curved surface optical array and the plane optical receiver can be solved.

Description

Technical Field

[0001] The present invention relates to the technical field of bionic compound eye imaging technology, and particularly to a curved compound eye imaging system based on relay image transfer. Background Art

[0002] Biological compound eyes have advantages such as a large field of view, low distortion, and sensitivity to motion. To simulate such excellent performance, in recent years, artificial bionic compound eye imaging systems have become the focus of research, and the main designs include planar compound eyes, curved compound eyes, and multi-camera array compound eyes. Although planar compound eyes are easy to manufacture, they are prone to problems such as insufficient light sensing and imaging distortion when large-angle light is incident, and complex optical compensation techniques are required to expand the field of view, increasing the design complexity and cost. The multi-camera array compound eye achieves a large field of view through the collaborative work of multiple camera modules, but precise alignment and synchronization are required, and even a slight deviation may lead to image distortion.

[0003] Compared with planar compound eyes and multi-camera array compound eyes, curved compound eyes are more prominent in simulating the advantages of biological compound eyes. Its optical units are arranged regularly on a curved surface, which can achieve wide-angle imaging without increasing the system complexity, and solve the deficiency of planar compound eyes in edge imaging quality. The curved compound eye also does not require an optical compensation system, adapts to incident light at different angles, and achieves excellent light sensing and imaging performance. In addition, the structural design of the curved compound eye is compact, avoiding the complex requirements for module calibration and synchronization in the multi-camera array, simplifying the manufacturing and maintenance costs, and its lightweight advantage is suitable for scenarios such as portable devices and drones. Its low power consumption characteristic reduces the demand for high-performance computing resources.

[0004] The biggest feature of the curved compound eye lies in its curved geometric structure, which distributes photosensitive units on a curved surface. This design enables each photosensitive unit to independently receive light from different directions, thereby covering a larger viewing angle range. This wide field of view characteristic makes the curved compound eye particularly suitable for scenarios that require large field of view and high-resolution imaging, such as environmental monitoring, drone navigation, and medical imaging. Since the photosensitive units are distributed on a curved surface, the curved compound eye can achieve a compact and lightweight system structure while maintaining high-performance imaging. However, since the imaging position of the curved microlens array is on its curved focal plane, the existing technology cannot make a curved optical receiver, and only a planar receiver can be used. At this time, different focal lengths need to be set for each microlens of the microlens array so that the curved microlens array can be imaged on the same plane, greatly increasing the workload. Summary of the Invention

[0005] The present invention provides a curved compound eye imaging system based on relay image transfer to solve the conflict problem between the curved image collected by the curved optical array and the planar optical receiver.

[0006] The technical solution adopted by the present invention to solve its technical problems is to provide a curved compound eye imaging system based on relay imaging, including:

[0007] A curved compound eye structure, which is a curved micro-lens array composed of multiple micro-lenses;

[0008] A relay imaging system for converting the curved image formed by the curved micro-lens array on its focal surface into a planar image;

[0009] A planar receiver for receiving the planar image.

[0010] The relay imaging system includes a negative meniscus lens and a double Gauss lens arranged in sequence; the negative meniscus lens is used to compress the light rays from the curved micro-lens array to the vicinity of the optical axis; the double Gauss lens is used for aberration correction to ensure the imaging quality of the planar image.

[0011] The ratio of the radius of curvature of the rear optical surface to the radius of curvature of the front optical surface of the negative meniscus lens is: where r 1 is the radius of curvature of the front optical surface, r 2 is the radius of curvature of the rear optical surface, γ 1 is the image-side angle of view of the chief ray with a field of view of γ 0 passing through the front optical surface, α 1 is the incident angle of the chief ray with a field of view of γ 0 passing through the front optical surface, β 1 is the refraction angle of the chief ray with a field of view of γ 0 passing through the front optical surface.

[0012] The radius of curvature r 1 of the front optical surface of the negative meniscus lens is determined by h 1 = r 1 sin(γ 0 - α 1 ), where h 1 is the distance between the intersection of the chief ray with a field of view of γ 0 and the optical axis on the front optical surface.

[0013] The double Gauss lens corrects the field curvature by adjusting the structure of the thick lens in the double Gauss lens, corrects the spherical aberration by adjusting the curvature of the thin lens in the double Gauss lens, corrects the astigmatism by adjusting the distance between the two thick lenses in the double Gauss lens, and corrects the chromatic aberration by introducing a cemented surface in the thick lens of the double Gauss lens.

[0014] The micro-lens is a regular hexagonal micro-lens and is arranged into a regular hexagonal curved micro-lens array.

[0015] The arrangement angle of the microlenses is ω < θ < 2ω, where ω is the half field of view of the microlens and θ is the included angle between the optical axes of adjacent microlenses.

[0016] The parameters of the microlenses satisfy: where f′ is the focal length of the microlens, n is the refractive index of the material of the microlens, r 1 ′ and r 2 ′ are the front surface radius and the rear surface radius of the microlens respectively. The front surface curvature radius of the microlens is the same as the rear surface curvature radius. h is the thickness of the microlens, and D is the diameter of the microlens.

[0017] Beneficial effects

[0018] Due to the adoption of the above technical solution, compared with the prior art, the present invention has the following advantages and positive effects: A relay image conversion system is added between the curved compound eye structure and the planar receiver. Through this relay image conversion system, the curved image formed by the curved compound eye structure on its focal surface can be converted into a planar image, solving the conflict problem between the curved image collected by the curved optical array and the planar optical receptor. The curved compound eye structure used can capture more light rays from different angles, greatly improving the perception range of the system. Description of the drawings

[0019] Figure 1 is a schematic structural diagram of the curved compound eye imaging system based on relay image conversion according to an embodiment of the present invention;

[0020] Figure 2 is a sub-eye configuration and layout diagram;

[0021] Figure 3 is a field of view overlap diagram under different included angles between the optical axes of adjacent sub-eyes;

[0022] Figure 4 is a microlens imaging quality diagram in this embodiment;

[0023] Figure 5 is the main ray passing through the negative meniscus lens optical path diagram when the field of view is γ 0 in an embodiment of the present invention;

[0024] Figure 6 is an imaging quality diagram of the relay image conversion system in an embodiment of the present invention;

[0025] Figure 7 is the field curvature / distortion diagram of the relay image conversion system in an embodiment of the present invention;

[0026] Figure 8 is the MTF curve diagram of sub-eyes at different included angles with the Z-axis in an embodiment of the present invention;

[0027] Figure 9It is the sub-eye RMS spot diagram at the angle of 0° with the Z-axis in the embodiment of the present invention;

[0028] Figure 10 It is the sub-eye RMS spot diagram at the angle of 20° with the Z-axis in the embodiment of the present invention;

[0029] Figure 11 It is the sub-eye RMS spot diagram at the angle of 40° with the Z-axis in the embodiment of the present invention;

[0030] Figure 12 It is the field curvature / distortion diagram of the sub-eyes at different angles with the Z-axis in the embodiment of the present invention. Specific Embodiments

[0031] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of this application.

[0032] The embodiment of the present invention relates to a curved compound eye imaging system based on relay image transfer, as Figure 1 shown, including: a curved compound eye structure, which is a curved microlens array composed of a plurality of microlenses, where a single microlens is equivalent to a sub-eye in the curved compound eye structure; a relay image transfer system for converting the curved image formed by the curved microlens array on its focal surface into a planar image; and a planar receiver for receiving the planar image.

[0033] Figure 2 The common sub-eye configuration and arrangement diagram shown. Among them, when circular microlenses are arranged in a square array, its filling factor ff is where D is the diameter of the sub-eye and T is the spacing between sub-eyes; the filling factor when square microlenses are arranged in a square array is: The filling factor when circular microlenses are arranged in a regular hexagon array is: The filling factor when regular hexagon microlenses are arranged in a regular hexagon array is: Although arranging square microlenses in a square array and arranging regular hexagonal microlenses in a regular hexagonal array have the same filling rate in theory, the hexagonal sub-eyes have greater advantages in optical performance. The hexagonal structure can provide better field of view overlap, reduce aberration and edge effects, and is closer to the design of the bionic compound eye, making it more sensitive when capturing dynamic objects. The edge effects and lower symmetry of the square sub-eyes may affect the imaging quality, especially in complex dynamic scenes. Therefore, the curved compound eye structure in this embodiment uses regular hexagonal sub-eyes and arranges them in a regular hexagonal array on the curved surface, which greatly improves the filling rate, thereby effectively improving the utilization rate of light energy and reducing energy loss.

[0034] Figure 3 The field of view overlap diagrams for different included angles between the optical axes of adjacent sub-eyes are given. When θ > ω 1 + ω 2 , points A and B divide the field of view range into a field of view blind area and an over-overlap area (the overlap rate in this area increases from 0 to 1 in a short distance), and it remains a field of view blind area after point B. The overlap area is within a limited field of view and cannot meet the working requirements of the compound eye system for a large viewing distance; when θ ≤ ω 1 + ω 2 , points A and B divide the field of view range into a field of view blind area, an over-overlap area, and a working area. When θ = ω 1 + ω 2 , the field of view edge lines 1 and 2 of the sub-eyes are parallel, that is, the overlap area between the fields of view of the sub-eyes is a fixed value. When the observation distance is far enough, there is no overlap between the fields of view of adjacent sub-eyes, which cannot meet the working requirements of the compound eye system for a large viewing distance. When θ < ω 1 + ω 2 , there is a certain angle between the field of view edge lines 1 and 2 of the sub-eyes, so as to ensure that the fields of view of adjacent sub-eyes still overlap when the observation distance is far enough; when θ < ω 1 , when the observation distance is far enough, the field of view of the middle sub-eye will completely overlap with the fields of view of its adjacent sub-eyes, resulting in the field of view of the middle sub-eye being completely covered and the system design being redundant, which does not conform to the design concept; where θ is the included angle between the optical axes of adjacent sub-eyes, ω 1 and ω 2 are the half fields of view of two adjacent sub-eyes respectively. Therefore, in this embodiment, the arrangement angle of the sub-eyes is selected as ω < θ < 2ω.

[0035] In this embodiment, the parameters of the sub-eyes are calculated with reference to a positive lens, and the front and rear surface curvature radii are respectively r 1 ′ and r 2 ′; the thickness of the sub-eye is h; the focal length of the sub-eye is f′; the refractive index of the material of the sub-eye is n. Regarding it as a spherical mirror, there are:

[0036]

[0037] In this embodiment, the sub - eye serves as the core imaging unit and plays a crucial role. Each sub - eye independently undertakes the tasks of light collection and transmission, and can capture light from different directions in a complex optical scene. By designing the sub - eye as a regular hexagon and arranging it in a regular hexagon array in a tight manner, the field - of - view overlap between sub - eyes is increased, maximizing the utilization rate of light energy. At the same time, the multi - direction perception ability of the sub - eye enables the system to have higher sensitivity and resolution when capturing dynamic scenes and wide - field - of - view. Overall, the sub - eye not only improves the imaging efficiency of the system but also ensures the imaging quality under large - viewing - angle conditions, and is a key component for achieving high - performance imaging. Figure 4 This is the imaging quality diagram of the sub - eye in this embodiment.

[0038] The relay image - conversion system in this embodiment can convert the curved image collected by the microlens into a planar image and is applicable to different sub - eye shapes and arrangement methods. The relay image - conversion system includes a negative meniscus lens and a double - Gaussian lens arranged in sequence; the negative meniscus lens is used to compress the light from the curved microlens array to near the optical axis; the double - Gaussian lens is used for aberration correction to ensure the imaging quality of the planar image.

[0039] Figure 5 Shows a chief ray with a field - of - view of γ 0 passing through a negative meniscus lens with front and rear optical surface curvature radii of r 1 and r 2 respectively. In the figure, γ 1 is the image - side field - of - view angle of the chief ray with a field - of - view of γ 0 passing through the front optical surface, γ 2 is the image - side field - of - view angle of the chief ray with a field - of - view of γ 0 passing through the rear optical surface, h 1 is the distance from the intersection point of the chief ray with a field - of - view of γ 0 and the front optical surface to the optical axis, h 2 is the distance from the intersection point of the chief ray with a field - of - view of γ 0 and the rear optical surface to the optical axis, α 1 is the incident angle of the chief ray with a field - of - view of γ 0 passing through the front optical surface, α 2 is the incident angle of the chief ray with a field - of - view of γ 0 passing through the rear optical surface, β 1 is the refraction angle of the chief ray with a field - of - view of γ 0 passing through the front optical surface, β 2 is the refraction angle of the chief ray with a field - of - view of γ 0 passing through the rear optical surface, and θ is the angle between the normal of the rear optical surface and the optical axis of the chief ray with a field - of - view of γ 0 where:

[0040]

[0041] The image-space field of view angle can be obtained by tracing the chief ray, and the transmission equation of the chief ray is as follows:

[0042]

[0043] γ 1 = γ 0 + β 1 - α 1

[0044]

[0045] In the formula, n 0 and n 1 are the refractive indices of the object-space and image-space of the front optical surface respectively, and d is the distance between the front and rear optical surfaces.

[0046] In the design of a negative meniscus lens, according to the initial field of view angle γ 0 and the field of view compression ratio γ 0 / γ 2 are used as initial parameters to determine the conditions that the subsequent parameters of the system structure need to meet. Under the conditions of the initial field of view angle γ 0 , the field of view compression ratio γ 0 / γ 2 , the constant k, and the refractive index of the material being certain, the following set of equations can be obtained by combining the above formula:

[0047]

[0048] Applying this set of equations can obtain the radii of curvature of the front and rear optical surfaces (since the lens thickness d is much smaller than the radius of curvature, it is ignored):

[0049]

[0050] The function of the negative meniscus lens is to compress the field of view, so the value range of its constant k is 0.75 - 0.95, and the value is positively correlated with the size of the initial angle γ 0 .

[0051] The distance between the intersection point of the chief ray and the front optical surface and the optical axis is:

[0052] h 1 = r 1 sin(γ 0 - α 1 )

[0053] That is:

[0054]

[0055] Reasonably allocate the field-of-view compression ratio of the negative meniscus lens through the initial field-of-view angle, set the value of the constant k, and then obtain the ratio of the front and rear optical surface curvature radii At the distance h between the intersection point of the chief ray and the front optical surface and the optical axis 1 Under the limitation of, determine the front optical surface r 1 The value of, then the rear optical surface r 2 The value of is also determined accordingly.

[0056] The double-Gauss lens in this embodiment serves as the core structure of the relay image rotation system and undertakes more complex aberration correction tasks. Due to the compact symmetric design of the double-Gauss objective lens itself, the double-Gauss lens has good aberration control ability, especially excellent in the correction of lateral aberration. When designing this type of system, the correction problems of spherical aberration, chromatic aberration, field curvature, and astigmatism mainly need to be considered. The double-Gauss lens in this embodiment effectively corrects spherical aberration by adjusting the curvature of the thin lenses in the double-Gauss lens to ensure that light rays with different incident angles can be accurately focused. In addition, the thick lens structure in the double-Gauss lens helps to correct the field curvature problem, ensuring that light rays within the entire field of view can be imaged on the same plane and avoiding imaging blur or distortion in the edge region.

[0057] For the correction of astigmatism, the double-Gauss lens ensures that light rays in different directions can be focused at the same position by changing the distance between its two thick lenses, thereby obtaining a clear and stable image. And to correct chromatic aberration, a cemented surface is introduced in the thick lens of the double-Gauss lens, and the dispersion of light rays with different wavelengths is corrected through the optical properties of different materials to ensure that the system can maintain a consistent imaging effect when processing multi-band light rays. With these characteristics, the double-Gauss lens can comprehensively optimize and control the aberrations in the complex optical path, significantly improving the imaging quality.

[0058] During the optimization process, it is necessary to constrain the curvature radii of each lens to ensure that the lenses do not deform during the design process. At the same time, use operands such as GMTA and DIMX to precisely control the value of the system at the MTF cut-off frequency and the distortion, thereby ensuring the overall imaging quality.

[0059] Through the collaborative work of the negative meniscus lens and the double-Gauss lens group, the relay image rotation system in this embodiment can not only efficiently transmit the optical information of the curved compound eye, but also perform multi-stage aberration correction to ensure the accuracy and stability of the final imaging quality. The design of this relay image rotation system enables the optical system to still maintain excellent imaging performance under the conditions of a large field of view and high resolution, giving full play to the potential of the bionic compound eye system. Figure 6 and Figure 7 show the imaging quality of the relay image rotation system in this embodiment.

[0060] In this embodiment, the design of the double-Gauss lens group enables the entire system to better correct various aberrations, ensuring that light rays of different wavelengths and angles can be accurately focused. In addition, the regular hexagonal sub-eye arrangement structure and the efficient light transmission design further improve the utilization rate of light energy and enhance the system's response ability to weak light and dynamic scenes. This enables the system to maintain high sensitivity even under complex lighting conditions and capture moving objects more precisely. Figures 8 - 12 For the imaging quality of sub-eyes at 0°, 10°, 20°, 30°, and 40° on one side of the main array of the compound eye lens.

[0061] It is not difficult to find that in this embodiment, the initial field of view angle γ is used 0 to design the required negative meniscus lens to compress the field of view, and a double-Gauss lens is combined as the subsequent focusing lens group for optimization. With its compact symmetric structure, the double-Gauss lens has a simpler aberration control ability, reducing the adjustment complexity. At the same time, its miniaturized design greatly reduces the overall volume of the system. Moreover, the larger aperture of the double-Gauss lens allows more light to enter the lens, not only improving the system's sensitivity but also enhancing its imaging performance in low-light environments.

[0062] In terms of the field of view, since the sub-eyes in this embodiment adopt a hexagonal close arrangement and are combined with the wide-angle design of the relay image transfer system, the system can achieve a wider field of view range. Compared with the traditional planar sub-eye structure, the curved micro-lens array used in the present invention can capture more light rays from different angles, greatly enhancing the system's sensing range. This wide-field-of-view design gives the system obvious advantages in applications such as large-area scene monitoring, navigation, or detection.

[0063] In this embodiment, through the combination of the negative meniscus lens and the double-Gauss lens, the parameters of all sub-eyes can be kept the same, eliminating the need for complex adjustment and calibration. This not only simplifies the system design and manufacturing process but also ensures imaging consistency and accuracy. In traditional systems, sub-eyes often require different parameter adjustments to adapt to complex optical path designs, increasing the system complexity and debugging difficulty.

[0064] In addition, the structure of the relay image transfer system in this embodiment only uses two sets of optical devices, and through a compact design, it greatly reduces the volume and weight of the entire optical system. The negative meniscus lens and the double-Gauss lens can effectively reduce the optical path and optimize light transmission, avoiding the large and complex multi-lens group structure in traditional compound eye systems. This improvement enables the system to have the advantage of light weight while maintaining high performance, especially suitable for applications in scenarios with strict requirements for weight and volume, such as drones, wearable devices, and micro-imaging devices.

Claims

1. A curved compound eye imaging system based on relay imaging, characterized in that: include: The curved compound eye structure is a curved microlens array composed of multiple microlenses; A relay image transfer system, used for converting the curved surface image formed by the curved microlens array on its focal curved surface into a flat image; A planar receiver is used to receive the planar image.

2. The curved compound eye imaging system based on relay image according to claim 1, characterized in that: The relay image system comprises a negative meniscus lens and a double Gaussian lens which are arranged in sequence; the negative meniscus lens is used to compress the light from the curved microlens array to the vicinity of the optical axis; the double Gaussian lens is used to perform aberration correction to ensure the imaging quality of the plane image.

3. The curved compound eye imaging system based on relay image according to claim 1, characterized in that: The ratio of the radius of curvature of the rear optical surface of the negative meniscus lens to the radius of curvature of the front optical surface is: Wherein, r1 is the radius of curvature of the front optical surface, r2 is the radius of curvature of the rear optical surface, γ1 is the image angle of the main light with a field of view of γ0 passing through the front optical surface, α1 is the incident angle of the main light with a field of view of γ0 passing through the front optical surface, and β1 is the refraction angle of the main light with a field of view of γ0 passing through the front optical surface.

4. The curved compound eye imaging system based on relay image transfer according to claim 3, characterized in that: The radius of curvature r1 of the front optical surface of the negative meniscus lens is determined by h1=r1sin(γ0-α1), wherein h1 is the distance between the intersection of the main light ray with a field of view of γ0 and the front optical surface and the optical axis.

5. The curved compound eye imaging system based on relay image transfer according to claim 1, characterized in that: The double Gaussian lens corrects field curvature by adjusting the structure of the thick lens in the double Gaussian lens, corrects spherical aberration by adjusting the curvature of the thin lens in the double Gaussian lens, corrects astigmatism by adjusting the distance between two thick lenses in the double Gaussian lens, and corrects chromatic aberration by introducing a cemented surface in the thick lens in the double Gaussian lens.

6. The curved compound eye imaging system based on relay image according to claim 1, characterized in that: The microlenses are regular hexagonal microlenses and are arranged into a regular hexagonal curved microlens array.

7. The curved compound eye imaging system based on relay image transfer according to claim 6, characterized in that: The arrangement angle of the microlenses is ω<θ<2ω, wherein ω is the half field of view of the microlens, and θ is the angle between the optical axes of adjacent microlenses.

8. The curved compound eye imaging system based on relay image transfer according to claim 6, characterized in that: The parameters of the microlens satisfy: Wherein, f′ is the focal length of the microlens, n is the refractive index of the material of the microlens, r1′ and r2′ are the front surface radius and the rear surface radius of the microlens respectively, the front surface curvature radius of the microlens is the same as the rear surface curvature radius, h is the thickness of the microlens, and D is the diameter of the microlens.

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