A long-wave infrared focusing type light field camera parameter design method

Abstract

This invention discloses a parameter design method for a long-wave infrared focusing light field camera, belonging to the field of computational imaging technology. The method includes: determining the parameters of the main lens and the pixel size of the detector based on the imaging object distance, while satisfying the long-wave infrared diffraction limit constraint; employing a high-fill-rate microlens array structure; calculating the axial distance between the microlens array, the detector, and the main lens based on pupil matching and multi-view depth recovery requirements; determining the allowable circle of confusion according to the long-wave infrared diffraction limit, and designing a multi-focal-length microlens array to achieve continuous depth-of-field coverage; finally, optimizing the microlens aperture using a depth resolution model to balance depth resolution and depth-of-field range. This invention, through the collaborative design and overall optimization of the parameters of the main lens, microlens array, and detector, achieves long-distance, large depth-of-field, and high depth-resolution light field imaging in the long-wave infrared band, providing effective design guidance for infrared three-dimensional sensing systems.

Description

Technical Field

[0001] This invention relates to the field of computational imaging technology, and specifically to a parameter design method for a long-wave infrared focusing light field camera. Background Technology

[0002] Light field imaging technology can simultaneously record the spatial position and propagation direction of light in a single exposure, thereby acquiring multi-dimensional light field data containing spatial and angular information. Subsequent calculations can then be used to achieve multi-view imaging and single-frame 3D reconstruction. Infrared imaging, on the other hand, images by detecting the thermal information radiated by an object itself, offering advantages such as independence from external lighting and adaptability to day / night cycles and complex weather conditions.

[0003] In the prior art, there has been a large amount of research on the parameter design of focusing light field cameras. For example, Chinese invention patent application CN113189603A (published on July 30, 2021) discloses a method and system for designing parameters of a structured light depth camera. The method includes: determining the angle between the focal plane and the optical axis based on the working range and field of view of the structured light depth camera; determining the installation position of the structured light depth camera, as well as the relationship between the tilt angle and the lens focal length, wherein the image sensor in the structured light depth camera is installed at the tilt angle to the lens, and the optical parameters after installation conform to Scherm's law; determining the depth of field of the structured light depth camera based on the working range, thereby determining the relationship between the aperture size and the pixel size of the structured light depth camera.

[0004] For example, Chinese invention patent application CN115150607A (published on October 4, 2022) discloses a parameter design method for a focusing all-optical camera based on a multi-focal-length microlens array. Based on the design method of traditional focusing all-optical cameras, it combines the sub-pixel recognition capability of optical system parameters and algorithms, establishes a parameter design analysis model for an all-optical camera based on a multi-focal-length microlens array according to binocular stereo vision, and simplifies the model by analyzing the constraints between various parameters. Theoretically, it provides guidance for the design of an all-optical camera system based on a multi-focal-length microlens array, enabling the design of the entire focusing all-optical camera to achieve a balance between the optical system and the design algorithm, and achieve the best imaging effect.

[0005] For example, Chinese invention patent application CN112235508A (published on January 15, 2021) discloses a parameter design method for a focusing light field camera system. Utilizing the flexible structure of a focusing light field camera, it analyzes the resolution of light field images to determine the influence of the camera's internal geometric parameters on the system's imaging effect. This allows for the selection of appropriate system structural parameters based on actual needs, maximizing the performance of existing detectors and optical structures to complete the system design. However, existing light field cameras are mostly designed for close-range visible light scenes. Due to the small microlens aperture and equivalent parallax baseline length, the parallax signal formed between different viewpoints is extremely weak at long distances, resulting in a significant decrease in depth estimation accuracy. This makes it difficult to meet the application requirements of long-distance 3D perception, and their effective range is usually limited to the order of ten meters. At the same time, in the long-wave infrared band, because the imaging wavelength is significantly larger than that of visible light, the system diffraction effect is more obvious, further limiting the imaging resolution and effective depth of field, thus exacerbating the problems of weak parallax signal and blurred imaging in long-distance light field imaging. In addition, existing technologies usually design the parameters of the main lens, microlens array, and detector relatively independently, failing to systematically and collaboratively consider the coupling relationship between imaging characteristics and the parameters of each component in the long-wave infrared band, especially the overall trade-off between diffraction limit, light flux requirement, parallax baseline length, and depth of field continuity.

[0006] Therefore, there is an urgent need for a parameter design method for a focusing light field camera specifically designed for long-distance imaging scenarios in the long-wave infrared band, so as to achieve large depth-of-field focusing light field imaging suitable for long-distance scenarios in a single-camera structure, thereby improving the depth resolution capability of long-distance light field imaging while ensuring continuous depth-of-field coverage. Summary of the Invention

[0007] To address the above technical problems, this invention provides a parameter design method for a long-wave infrared focusing light field camera. The focusing light field camera includes a main lens, a microlens array, and a detector. The parameter design method includes the following steps: Step S1: Based on the thin lens approximation conditions, determine the range of the main lens focal length F according to the imaging object distance u and the target size, and select the entrance pupil diameter A of the main lens in combination with the signal-to-noise ratio constraint of the long-wave infrared band, while matching the number of detector pixels M and the pixel size s.

[0008] Step S2: Determine the geometry of the microlenses. The microlens array adopts a row-aligned staggered arrangement of hexagonal apertures to improve pixel fill rate and effective sampling efficiency. Microlens aperture... The constraint formula for the pixel size s is: Where N is the number of pixels covered by a single microlens on the detector plane; Step S3: Determine the position of the microlens; based on the geometric matching relationship between the exit pupil of the main lens and the aperture of the microlens, calculate the distance d between the microlens array and the detector and the axial distance D from the main lens to the microlens array; Step S4: Determine the focal length of the microlens. Based on the characteristics of the long-wave infrared band, determine the working range that the microlens array needs to cover and effectively image, that is, the range of the virtual image position formed by the main lens in the image space. Step S5: Optimize the microlens aperture based on depth resolution.

[0009] Furthermore, for target imaging at object distances of tens to hundreds of meters, the imaging satisfies the thin lens model approximation. At that time, the imaging scale of the target on the image plane It is approximately linearly related to the focal length. ,in This represents the actual size of the target. It can be seen that increasing the focal length of the main lens... It can effectively improve the magnification of the image plane, enabling the target to form a sufficient image size on the detector, thereby improving spatial sampling conditions and enhancing the effective parallax signal between microlenses.

[0010] In the long-wave infrared band, due to the limited target radiation energy and high detector noise level, the system signal-to-noise ratio is highly sensitive to the incident light flux. To ensure sufficient entrance pupil light flux and suppress noise amplification effects, the main lens should preferably adopt a smaller F-number design, i.e., a larger entrance pupil diameter A. Considering existing long-wave infrared optical processing capabilities and system integration feasibility, the F-number of the main lens is usually limited to the range of 1.0-2.0, and the entrance pupil diameter A is 50-400 mm.

[0011] Regarding detector parameter selection, the number of pixels M must match the imaging object distance u and the focal length F of the primary lens. Under long-distance imaging conditions, the system's minimum resolvable line dimension in the object space is... It can be approximated as: , Where u is the imaging object distance, F is the focal length of the principal lens, s is the pixel size of the detector, and M is the number of pixels in the detector. The imaging scale of the target on the image plane; Given an imaging object distance *u* and a primary lens focal length *F*, increasing the number of detector pixels (or equivalently reducing pixel size) can effectively reduce the minimum resolvable size of distant targets, allowing for a sufficient number of sampling points on the image plane. For long-wavelength infrared imaging applications at the hundred-meter level, a megapixel or higher area array configuration is preferred, for example... , Or even higher, to ensure sufficient sampling density of the target on the image plane while maintaining the imaging signal-to-noise ratio.

[0012] Furthermore, given the significant diffraction effect in the long-wave infrared band, the pixel size should match the system's diffraction-limited resolution. To avoid undersampling and oversampling, it is generally necessary to satisfy both the diffraction limit and Nyquist sampling constraints. The constraint formula for the detector's pixel size s in step S1 is: , in, Indicates the radius of the Airy disk. Indicates wavelength. The F-number of the main lens, through The above parameters are calculated and used as initial constraints for system design. They can be iteratively adjusted in subsequent optical structure and microlens array design processes according to imaging quality and performance requirements.

[0013] Furthermore, the formula for calculating the distance d between the microlens array and the detector in step S3 is as follows: ,in, Let F be the aperture of the microlens array, F be the focal length of the main lens, and A be the entrance pupil diameter of the main lens.

[0014] Furthermore, the formula for calculating the axial distance D from the main lens to the microlens array in step S3 is as follows: , in, This represents the distance from the entrance pupil of the primary lens to the virtual image point, where n is the number of microlenses in the microlens array, and n≥2. Let F be the aperture of the microlens array, F be the focal length of the primary lens, and A be the entrance pupil diameter of the primary lens. The relative position of the microlens array and the primary lens is not only constrained by the imaging object distance and the focal length of the primary lens, but also closely related to the number of microlenses involved in imaging and their equivalent distribution on the exit pupil surface of the primary lens. This parameter directly affects the effective parallax baseline length and depth recovery capability of the system.

[0015] Furthermore, step S4 includes the following steps: Step S41: Assume the object space imaging distance designed by the system is... According to the thin lens imaging model, the range of the virtual image position formed by the main lens in the image space is the area that needs to be covered and effectively imaged by the microlens array. Step S42: Determine the diameter of the circle of confusion based on the perfected imaging diffraction-limited resolution model. ; Step S43: Based on the similar triangle relationship and the thin lens imaging model, determine the diameter r of the circle of confusion formed on the detector plane after the virtual image point is imaged by the i-th type of microlens; Step S44: Based on the focal length of the first type of microlens Determine the corresponding front and back depth of field boundaries of the image under this focal length condition; Step S45: Determine the constraint relationship of the multifocal microlens array.

[0016] Furthermore, the range of the virtual image position formed by the main lens in the image space in step S41 is expressed as follows: , Where F is the focal length of the main lens, and D is the axial distance from the main lens to the microlens array. The minimum object-space imaging distance for the system design. The maximum value of the object space imaging distance designed for the system.

[0017] Furthermore, the diameter of the dispersion circle described in step S42 The calculation formula is: , in, The radius of the smallest resolvable Airy disk formed by the optical system under the diffraction limit is given. For the operating wavelength, denoted by F-number, where s is the F-number of the microlens and s is the pixel size of the detector.

[0018] Furthermore, the formula for calculating the diameter r of the dispersion circle formed by the detector plane in step S43 is as follows: , in, Let d be the aperture of the microlens array, and d be the distance between the microlens array and the detector. Let the focal length of the i-th type of microlens be i = 1, 2, 3. This is the position of the nearest virtual image on the image side.

[0019] Furthermore, in step S44, to ensure image sharpness, at the depth of field boundary, make... The position of the nearest virtual image on the image side is taken as As a design reference point, the focal length of the first type of microlens can be calculated. Under this focal length condition, the corresponding front and back depth-of-field boundaries of the image side can be expressed as follows: , , in, For the deep boundary of the foreground, This represents the boundary of the background depth of field.

[0020] Furthermore, the constraint relationship of the multifocal microlens array described in step S45 is expressed as follows: , After determining the focal length of the first type of microlens and its corresponding image-side depth of field range, the focal length and depth of field range parameters of the other types of microlenses can be solved sequentially, thereby completing the systematic design of the multi-focal-length microlens array and achieving continuous coverage of the target imaging distance range.

[0021] Furthermore, the specific method of step S5 includes the following steps: Step S51: Determine the depth resolution. Combining the imaging geometry of the main lens, map the error in the virtual depth domain to the object space to obtain the object-space depth resolution. The formula is: , in, Let F be the distance from the object to the plane of the primary lens, and F be the focal length of the primary lens. The parallax precision is represented by d, where d is the distance between the microlens array and the detector. This represents the virtual depth estimation error.

[0022] Step S52: Determine the virtual depth range. In a hexagonal microlens array, the baseline length between different microlens pairs can be expressed as the product of the microlens aperture and the scaling factor ki. When the i-th level baseline length is used for depth estimation, the corresponding virtual depth range satisfies: , Where, k1=1, k2= k3=2, k4= k5=3, k6= k7= k8=4, k9= k 10 = k 11 =5; This represents virtual depth. The selection of the microlens aperture not only affects the angular sampling density of the micro-image but also directly determines the equivalent parallax baseline length of the system, thus having a crucial impact on depth estimation uncertainty. Increasing the microlens aperture can effectively improve the system's depth resolution and reduce the minimum resolvable depth difference. Therefore, during the design process, through the synergistic optimization of the aforementioned microlens aperture, position, and focal length parameters, the depth resolution of the light field camera can meet the performance requirements of the target application scenario.

[0023] Compared with existing technologies, the advantages and effects of this application are as follows: 1. This invention is the first to systematically propose a parameter design method for a focusing light field camera for long-wave infrared band and long-distance (e.g., 10-100 meters) imaging scenarios. By taking the two core challenges of significant diffraction effects in long-wave infrared and weak parallax signals in long-distance imaging as design constraints, it overcomes the performance bottlenecks of existing visible light or short-distance design methods when directly transplanted to this scenario, and realizes an important expansion of the application scenarios of the technology.

[0024] 2. This invention breaks through the limitations of traditional step-by-step or isolated design of component parameters, and creatively proposes a systematic design process that starts from the imaging object distance and uses depth-of-field continuity and depth resolution as dual constraints to jointly constrain and synergistically derive key parameters such as the main lens (focal length, entrance pupil diameter), microlens array (geometry, position, multi-focal length), and detector (pixel size). This overall optimization method ensures that the system achieves the best balance among performance indicators such as luminous flux, spatial-angular sampling, equivalent parallax baseline length, and depth-of-field coverage.

[0025] 3. By deriving and applying a depth-of-field criterion based on the long-wavelength infrared diffraction limit and a design principle for seamless depth-of-field connection of multi-focal-length microlens arrays, this invention ensures continuous depth-of-field coverage within a long-distance target range (e.g., 10-100m). Furthermore, through the established depth resolution model, the quantitative impact of parameters such as microlens aperture on depth estimation accuracy is clearly revealed, and optimization methods are provided. This significantly improves depth resolution at long distances while maintaining a large depth of field.

[0026] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, the preferred embodiments of this application are described in detail below with reference to the accompanying drawings.

[0027] The above and other objects, advantages and features of this application will become more apparent to those skilled in the art from the following detailed description of specific embodiments in conjunction with the accompanying drawings. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. In all drawings, similar elements or parts are generally identified by similar reference numerals. In the drawings, the elements or parts are not necessarily drawn to scale.

[0029] in: Figure 1 A flowchart illustrating a parameter design method for a long-wave infrared focusing light field camera; Figure 2 This is a schematic diagram illustrating the constraint conditions between the beam cone received by the microlens array in the detector plane and the image-side beam formed by the main lens in the microlens array plane. Figure 3A schematic diagram of an image formed by an object point passing through a main lens and then captured by n microlenses and captured by the detector. Figure 4 A schematic diagram of light rays refracted by a microlens to form a circle of confusion on the sensor from a virtual image point; Figure 5 Schematic diagram of depth of field range for three focal length microlenses; Figure 6 Comparison of depth resolution as object distance under different microlens aperture designs; Figure 7 A simulation model of a long-wave infrared light field camera built on Zemax; Figure 8 Simulated infrared light field white image; Figure 9 The original image of the infrared light field obtained from simulation; Figure 9 (a) is the original image of the infrared light field obtained from the simulation; Figure 9 (b) is the original infrared light field image obtained from the simulation; Figure 10 Parameter diagram of the actual structure of the infrared microlens array; Figure 10 (a) is a front elevation view of the actual infrared microlens array; Figure 10 (b) is a side elevation view of the actual infrared microlens array; Figure 10 (c) is a diagram of the actual infrared microlens array with microlenses arranged. Figure 11 Infrared light field principle prototype structure diagram. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. In the following description, specific details such as specific configurations and components are provided merely to help fully understand the embodiments of this application. Therefore, those skilled in the art should understand that various changes and modifications can be made to the embodiments described herein without departing from the scope and spirit of this application. In addition, for clarity and brevity, descriptions of known functions and structures are omitted in the embodiments.

[0031] It should be understood that the phrase "an embodiment" or "this embodiment" throughout the specification means that a specific feature, structure, or characteristic related to the embodiment is included in at least one embodiment of this application. Therefore, "an embodiment" or "this embodiment" appearing throughout the specification does not necessarily refer to the same embodiment. Furthermore, these specific features, structures, or characteristics can be combined in any suitable manner in one or more embodiments.

[0032] Furthermore, reference numerals and / or letters may be repeated in different examples within this application. Such repetition is for the purpose of simplification and clarity and does not in itself indicate a relationship between the various embodiments and / or settings discussed.

[0033] In this article, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can mean: A exists alone, B exists alone, and A and B exist simultaneously. The term " / and" describes another type of relationship between related objects, indicating that two relationships can exist. For example, A / and B can mean: A exists alone, and A and B exist alone. In addition, the character " / " in this article generally indicates that the related objects before and after it have an "or" relationship.

[0034] In this article, the term "at least one" is merely a description of the relationship between related objects, indicating that there can be three relationships. For example, "at least one of A and B" can mean: A exists alone, A and B exist simultaneously, or B exists alone.

[0035] It should also be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion.

[0036] Example 1 This embodiment introduces a parameter design method for a long-wave infrared focusing light field camera.

[0037] Please refer to Figure 1 As shown, Figure 1 This is a flowchart of a parameter design method for a long-wave infrared focusing light field camera.

[0038] A parameter design method for a long-wave infrared focusing light field camera, the focusing light field camera comprising a main lens, a microlens array, and a detector, the parameter design method comprising the following steps: Step S1: Determine the basic parameters of the main lens and the detector. Based on the imaging object distance u of the focusing light field camera, determine the focal length F of the main lens, the entrance pupil diameter A of the main lens, the number of pixels M of the detector, and the pixel size s of the detector. Step S2: Determine the geometry of the microlenses. The microlens array adopts a row-aligned staggered arrangement of hexagonal apertures to improve pixel fill rate and effective sampling efficiency. Microlens aperture... The constraint formula for the pixel size s is: Where N is the number of pixels covered by a single microlens on the detector plane; Step S3: Determine the position of the microlens; based on the geometric matching relationship between the exit pupil of the main lens and the aperture of the microlens, calculate the distance d between the microlens array and the detector and the axial distance D from the main lens to the microlens array; Step S4: Determine the focal length of the microlens. Based on the characteristics of the long-wave infrared band, determine the working range that the microlens array needs to cover and effectively image, that is, the range of the virtual image position formed by the main lens in the image space. Step S5: Optimize the microlens aperture based on depth resolution.

[0039] The technical advantages of this embodiment are as follows: It proposes a camera parameter design process and method that starts with a distant object point and is constrained by depth of field and depth resolution. By jointly constraining and synergistically deriving key parameters such as the focal length and entrance pupil size of the main lens, the aperture and arrangement of the microlenses, and the pixel size and number of detector pixels, it achieves overall optimization of spatial sampling, angular sampling, and light transmission capability under a single-camera structure.

[0040] Example 2 Based on Example 1, this example discloses a further design of step S1 in the parameter design method for a long-wave infrared focusing light field camera.

[0041] In the long-wave infrared band, based on the structural characteristics of a focusing light field camera, and constrained by depth of field and depth resolution, the interrelationships between system parameters are obtained, thereby determining the values ​​of each system parameter. These system parameters include the focal length F of the primary lens, the entrance pupil diameter A of the primary lens, the microlens aperture and focal length of the microlens array, the number of pixels M and the pixel size s of the detector, the imaging object distance u, the axial distance D from the primary lens to the microlens array, and the axial distance d from the microlens array to the detector. These parameters collectively determine the spatial-angular sampling characteristics, light transmission capability, and final imaging and depth sensing performance of the light field camera, and are the core variables for system design and optimization.

[0042] In the initial design phase of the system, the imaging object distance u must be determined first, and the basic parameters of the main lens and detector should be determined accordingly, serving as the initial constraints for subsequent optical design and parameter derivation.

[0043] For targets with object distances of tens or hundreds of meters, the imaging satisfies the thin lens model approximation, and the imaging scale of the target on the image plane... It is approximately linearly related to the focal length. in This represents the actual size of the target. It can be seen that increasing the focal length of the main lens... This effectively improves the image magnification, enabling distant targets to form a sufficient image size on the detector, thereby improving spatial sampling conditions and enhancing the effective parallax signal between microlenses. Considering both field of view coverage and system volume constraints, the focal length of the main lens should be selected as [value missing]. The medium to long focal length range is designed to balance long-distance resolution with system feasibility.

[0044] In the long-wave infrared band, due to the limited target radiation energy and high detector noise level, the system signal-to-noise ratio (SNR) is highly sensitive to the incident light flux. To ensure sufficient entrance pupil light flux and suppress noise amplification, the primary lens should ideally have a smaller F-number, i.e., a larger entrance pupil diameter A. Considering existing long-wave infrared optical fabrication capabilities and system integration feasibility, the F-number of the primary lens is typically limited to the range of 1.0-2.0. Under this F-number condition, combined with the focal length range of the primary lens, the entrance pupil diameter can be approximately 50-400 mm. This parameter range can ensure the imaging SNR while also considering the fabrication difficulty and engineering feasibility of the long-wave infrared optical system.

[0045] Regarding detector parameter selection, the number of pixels M must match the imaging object distance u and the focal length F of the primary lens. Under long-distance imaging conditions, the system's minimum resolvable line dimension in the object space is... It can be approximated as: , Where u is the imaging object distance, F is the focal length of the principal lens, s is the pixel size of the detector, and M is the number of pixels in the detector. Let be the imaging scale of the target on the image plane. Given the imaging object distance *u* and the focal length *F* of the primary lens, increasing the number of detector pixels (or equivalently reducing the pixel size) can effectively reduce the minimum resolvable size of distant targets, allowing for a sufficient number of sampling points on the image plane. For long-range, long-wave infrared imaging applications at the hundred-meter level, the detector preferably uses a megapixel array configuration of one megapixel level or higher, such as 1024×1024, 1280×1024, or higher, to ensure sufficient sampling density of the target on the image plane while maintaining the imaging signal-to-noise ratio.

[0046] Furthermore, given the significant diffraction effect in the long-wave infrared band, the pixel size should match the system's diffraction-limited resolution. To avoid undersampling and oversampling, it is generally necessary to satisfy both the diffraction limit and Nyquist sampling constraints. The constraint formula for the detector's pixel size s in step S1 is: , in, Indicates the radius of the Airy disk. Indicates wavelength. The F-number of the main lens, through The above parameters are calculated and used as initial constraints for system design. They can be iteratively adjusted in subsequent optical structure and microlens array design processes according to imaging quality and performance requirements.

[0047] The technical effects of this embodiment are as follows: It clarifies that in long-wave infrared long-distance scenarios, the main lens should preferably be selected with a medium-long focal length and a small F number to balance the image plane scale and light flux. It also gives for the first time the specific mathematical constraint that the detector pixel size must match the long-wave infrared diffraction limit, laying the correct initial conditions for system design and avoiding fundamental performance defects caused by improper selection of basic parameters.

[0048] Example 3 Based on Embodiment 1 or 2, this embodiment discloses a further design of step S2 of the parameter design method for a long-wave infrared focusing light field camera.

[0049] In optical field imaging systems, the geometric arrangement of the microlens array directly determines the effective sampling structure and pixel utilization of the detector, thus significantly impacting the system's spatial resolution and imaging energy distribution. To quantitatively describe the pixel utilization efficiency under different microlens arrangements, a pixel utilization rate is introduced. Defined as: , in This indicates the area covered by the effective aperture of the microlens. This represents the periodic arrangement area corresponding to a single microlens unit.

[0050] For a circular orthogonal arrangement, its pixel utilization rate The pixel utilization rate of the circular staggered arrangement is high. Square orthogonal arrangement pixel utilization Pixel utilization rate of hexagonal staggered arrangement It can be seen that the staggered arrangement structure is significantly better than the orthogonal arrangement in terms of pixel utilization. To maximize the effective imaging area of ​​the detector and reduce the waste of invalid pixels, a microlens array structure with circular staggered or hexagonal staggered arrangements is more suitable.

[0051] Let the detector pixel size be s, and the number of pixels covered by a single microlens on the detector plane be N, then the microlens aperture... The relationship between the pixel size s and the pixel size s is satisfied. .

[0052] To meet the dual requirements of optical field imaging for equivalent baseline length and macro-pixel angle sampling density, the microlens aperture should not be too small, otherwise it will lead to insufficient angular resolution, thus limiting the performance of long-distance depth estimation.

[0053] The technical effects of this embodiment are as follows: By introducing the concept of pixel utilization, the efficiency of different microlens arrangements is quantitatively analyzed, and the significant advantages of hexagonal staggered arrangement in pursuing high light energy utilization in long-wave infrared systems are clearly pointed out, providing a key design choice for improving the system signal-to-noise ratio and effective sampling efficiency.

[0054] Example 4 Based on Example 3, this example discloses a further design of step S3 in the parameter design method for a long-wave infrared focusing light field camera.

[0055] In a focusing light field camera, the beam cone received by the microlens array on the detector plane should match the image-side beam cone formed by the main lens on the microlens array plane to ensure that the micro-image exactly fills its corresponding pixel area and avoids crosstalk caused by beam clipping or overlap.

[0056] like Figure 2 As shown, this constraint can be described by the geometric relationship between the exit pupil of the primary lens and the aperture of the microlens. Then, the distance d between the microlens array and the detector can be obtained from the similar triangle relationship.

[0057] Furthermore, the formula for calculating the distance d between the microlens array and the detector in step S3 is as follows: ,in, Let F be the aperture of the microlens array, F be the focal length of the main lens, and A be the entrance pupil diameter of the main lens.

[0058] like Figure 3 As shown, furthermore, in order to recover the depth information of the scene from the light field data, at least two or more microlenses are needed to perform multi-view imaging of the same object point. Suppose that a certain object point is simultaneously imaged by n (n≥2) microlenses. Based on the thin lens imaging model and geometric optical relationships, the expression for the distance D between the microlens array and the main lens can be derived as follows: , in, This represents the distance from the entrance pupil of the primary lens to the virtual image point, where n is the number of microlenses in the microlens array, and n≥2. Let F be the aperture of the microlens array, F be the focal length of the main lens, and A be the entrance pupil diameter of the main lens. From the above relationships, it can be seen that the relative position of the microlens array and the main lens is not only constrained by the imaging object distance and the focal length of the main lens, but also closely related to the number of microlenses involved in imaging and their equivalent distribution on the exit pupil surface of the main lens. This parameter directly affects the effective parallax baseline length and depth recovery capability of the system.

[0059] The technical advantages of this embodiment are: it derives key calculation formulas for the distance d between the microlens array and the detector, and the distance D between the microlens array and the main lens. These formulas combine geometric matching conditions with the minimum number of viewing angles (n) required for depth recovery, ensuring that the system can both avoid micro-image crosstalk and form a sufficient equivalent parallax baseline, which is the core geometric guarantee for improving long-distance depth perception capabilities.

[0060] Example 5 Based on Example 1, this example discloses a further design of step S4 in the parameter design method for a long-wave infrared focusing light field camera.

[0061] The focal length of the microlens needs to be determined by the depth of field. Depth of field is generally defined as the range of object space within which a point can be considered in sharp focus during imaging, criterioned by the fact that the diameter of the blur spot formed by the point on the sensor plane does not exceed the permissible circle of confusion allowed by the system. For focusing light field cameras, the imaging process is a secondary imaging structure: the main lens first images the object-side scene in the image-side space, compressing the object-side depth of field to a limited image-side focal depth range; subsequently, this image-side focal depth region is resampled by the microlens array and imaged onto the detector plane. Therefore, the effective depth of field of the system is mainly constrained by the imaging characteristics of the microlenses, rather than the depth of field performance of the main lens itself.

[0062] Furthermore, step S4 includes the following steps: Step S41: Assume the object space imaging distance designed by the system is... According to the thin lens imaging model, the range of the virtual image position formed by the main lens in the image space is the area that needs to be covered and effectively imaged by the microlens array. Step S42: Determine the diameter of the circle of confusion based on the perfected imaging diffraction-limited resolution model. ; Step S43: Based on the similar triangle relationship and the thin lens imaging model, determine the diameter r of the circle of confusion formed on the detector plane after the virtual image point is imaged by the i-th type of microlens; Step S44: Based on the focal length of the first type of microlens Determine the corresponding front and back depth of field boundaries of the image under this focal length condition; Step S45: Determine the constraints of the multifocal length microlens array. Thus, after determining the focal length of the first type of microlens and its corresponding image-side depth of field range, the focal length and depth of field range parameters of the other types of microlenses can be solved sequentially, thereby completing the systematic design of the multifocal length microlens array and achieving continuous coverage of the target imaging distance range.

[0063] Furthermore, the range of the virtual image position formed by the main lens in the image space in step S41 is expressed as follows: , Where F is the focal length of the main lens, and D is the axial distance from the main lens to the microlens array. The minimum object-space imaging distance for the system design. The maximum value of the object space imaging distance designed for the system.

[0064] Furthermore, in step S42, in the long-wave infrared band, since the operating wavelength is significantly larger than that of visible light, the diffraction effect has a decisive impact on image sharpness. The depth-of-field criterion needs to comprehensively consider the diffraction limit and the detector sampling characteristics. Based on a complete imaging diffraction-limited resolution model, the diameter of the system's allowable circle of confusion is... It can be represented as: , in, The radius of the smallest resolvable Airy disk formed by the optical system under the diffraction limit is given. Where is the operating wavelength, N is the F-number of the microlens, and s is the pixel size of the detector.

[0065] The secondary imaging process of the microlens on the virtual image point of the primary lens is as follows: Figure 4 As shown, further, based on the similar triangle relationship and the thin lens imaging model, the diameter r of the circle of confusion formed on the detector plane after the virtual image point is imaged by the i-th type of microlens can be obtained. The calculation formula for the diameter r of the circle of confusion formed on the detector plane in step S43 is: , in, Let d be the aperture of the microlens array, and d be the distance between the microlens array and the detector. Let the focal length of the i-th type of microlens be i = 1, 2, 3. This is the position of the nearest virtual image on the image side.

[0066] Furthermore, in step S44, to ensure image sharpness, at the depth of field boundary, make... The position of the nearest virtual image on the image side is taken as As a design reference point, the focal length of the first type of microlens can be calculated. Under this focal length condition, the corresponding front and back depth-of-field boundaries of the image side can be expressed as follows: , , in, For the deep boundary of the foreground, This represents the boundary of the background depth of field.

[0067] Furthermore, to achieve continuous depth-of-field coverage within the image space, the multifocal length microlens array needs to satisfy seamless connection or moderate overlap between the depth-of-field intervals of various microlenses. The constraint relationship of the multifocal length microlens array in step S45 is expressed as follows: , .

[0068] Therefore, after determining the focal length of the first type of microlens and its corresponding image-side depth range, the focal length and depth range parameters of the other types of microlenses can be solved sequentially, thereby completing the systematic design of the multi-focal-length microlens array and achieving continuous coverage of the target imaging distance range.

[0069] The technical advantages of this embodiment are as follows: It proposes a depth-of-field criterion applicable to the long-wave infrared band that comprehensively considers the diffraction limit, and provides a systematic design method and recursive formula for achieving continuous depth-of-field coverage in the image space using multi-focal-length microlens arrays. This is a core technical means to achieve continuous depth-of-field coverage and effectively solves the problem of insufficient depth of field of single-focal-length microlenses.

[0070] Example 6 Based on Example 1, the example discloses a further design of step S5 in the parameter design method for a long-wave infrared focusing light field camera.

[0071] Based on the aforementioned design of microlens geometry, positional relationships, and focal length parameters, it is necessary to further evaluate the impact of the selected parameters on the system's 3D perception performance. Depth resolution characterizes the imaging system's ability to distinguish the relative distances of objects in the depth direction and is a key indicator for evaluating the depth recovery accuracy of a focusing light field camera.

[0072] Furthermore, the specific method of step S5 includes the following steps: Step S51: Determine the depth resolution; based on the error propagation model, the depth resolution of the light field camera can be expressed as: , Where d is the distance from the microlens array to the detector. This indicates the virtual depth estimation error; By further combining the imaging geometry of the primary lens, errors in the virtual depth domain can be mapped to the object space, thereby obtaining the object-space depth resolution. The formula is: , in, Let F be the distance from the object to the plane of the primary lens, and F be the focal length of the primary lens. The parallax precision is represented by d, where d is the distance between the microlens array and the detector. This represents the virtual depth estimation error.

[0073] Step S52: Determine the virtual depth range; in a hexagonal microlens array, the baseline length between different microlens pairs can be expressed as the microlens aperture and scaling factor k. i The product of these two factors, when used for depth estimation with the i-th level baseline length, results in a virtual depth range that satisfies the following: , Where, k1=1, k2= k3=2, k4= k5=3, k6= k7= k8=4, k9= k 10 = k 11 =5; Indicates virtual depth.

[0074] As can be seen from the above relationships, the selection of the microlens aperture not only affects the angular sampling density of the micro-image but also directly determines the equivalent parallax baseline length of the system, thus having a crucial impact on the uncertainty of depth estimation. Increasing the microlens aperture can effectively improve the system's depth resolution and reduce the minimum resolvable depth difference. Therefore, in the system design process, through the synergistic optimization of the aforementioned microlens aperture, position, and focal length parameters, the depth resolution of the light field camera can meet the performance requirements of the target application scenario.

[0075] The technical advantages of this embodiment are: it establishes a quantitative model between depth resolution and system parameters (especially microlens aperture), and provides a method for defining virtual depth range based on baseline length ratio. This enables designers to quantitatively evaluate and actively optimize the system's depth sensing accuracy, clearly revealing the positive effect of increasing the microlens aperture on improving long-distance depth resolution and its trade-off with depth of field.

[0076] Example 7 Based on any of the above embodiments, this embodiment discloses an infrared light field camera parameter design scheme.

[0077] Step 1: Based on the application requirements of the focused long-wave infrared light field camera, the basic design parameters of the system are determined as follows: imaging working distance is 10m-100m, main lens focal length is 105mm, entrance pupil diameter is 105mm, detector pixel count is 1920*1280, imaging band is 8-12μm, and the pixel size of the infrared detector is determined by the formula: , Therefore, the pixel size designed in this embodiment is This is to avoid undersampling while taking into account both signal-to-noise ratio and pixel utilization efficiency.

[0078] Step 2: To address the combined requirements of light throughput utilization and angle sampling capability for long-distance imaging, the microlens array employs a row-aligned, staggered arrangement of hexagonal apertures to improve pixel fill rate and effective sampling efficiency. Furthermore, to enhance the system's equivalent parallax baseline length and improve depth resolution, a large-aperture microlens structure is selected, with each microlens covering 60 pixels, corresponding to a physical aperture size of approximately 720µm.

[0079] Step 3: Given the focal length F and entrance pupil diameter A of the main lens, the distance d between the microlens array and the detector can be calculated based on the geometric matching relationship between the exit pupil of the main lens and the aperture of the microlens: This determines the design spacing between the microlens array and the photosensitive surface of the infrared detector as follows: This ensures a proper match between microlens imaging and detector sampling, preventing micro-image cropping or overlap.

[0080] To meet the requirements of depth imaging, it is assumed that an object point at a maximum distance of 100m can be simultaneously imaged by n=2.5 microlenses. Based on the geometric relationship between the microlens array and the main lens, the axial distance D can be calculated as follows: , Therefore, the axial design distance between the microlens array and the main lens is determined to be approximately 102.95 mm.

[0081] Step 4: Under the above parameter conditions, the range of the virtual image position formed by the main lens in the image space, that is, the working range that the microlens array needs to cover and effectively image, can be determined as follows: , Considering the dominant role of diffraction in the long-wave infrared band, and based on a perfected imaging diffraction-limited resolution model, the system's allowable circle of confusion diameter is... It can be represented as: , Take the radius of the diffuse spot at the depth of field boundary. And based on the position of the nearest virtual image. Using this as a design reference point for the first type of microlens, its focal length can be calculated as: , Under this focal length condition, the corresponding foreground and background depth of field positions are as follows: , , The negative sign here only indicates a directional convention, meaning the virtual image space is located behind the microlens array. Therefore, the effective depth of field covered by the first type of microlens in the image space is [2.162, 2.405] mm. Further, the far depth of field boundary of the first type of microlens... Using the same method as the near-end design point for the next type of microlens, the focal length of the second type of microlens can be solved. The corresponding image depth coverage range is [2.405, 2.722] mm; similarly, with As a starting point for the design, the focal length of the third type of microlens can be obtained. Its image depth range is [2.722, 3.160] mm.

[0082] Step 5: System Parameter Optimization Through the above design and derivation, the key parameters of the system can be determined. Under infrared imaging conditions, the parallax estimation accuracy is typically... We set this parameter to 0.2 pixels. Substituting this parameter into the depth resolution model, we can calculate that when the object distance is 100m, the theoretical depth resolution of the system is approximately 9.45m.

[0083] To further analyze the impact of microlens aperture on depth resolution performance, while keeping the parameters of the main lens and detector constant, light field imaging systems with microlens apertures of 40, 60, and 80 pixels were designed respectively. Other parameters were then matched accordingly, and the corresponding depth resolution curves were calculated and plotted, as shown in the attached figure. Figure 5 As shown, the results indicate that as the microlens aperture increases, the equivalent parallax baseline length of the system increases accordingly, and the depth resolution is significantly improved.

[0084] However, increasing the microlens aperture also reduces the effective depth of field for a single type of microlens, making it impossible to fully cover the 10-100m imaging range. Considering the trade-off between improved depth resolution and depth of field coverage, this paper ultimately selects a design scheme with a microlens aperture of 60 pixels to maintain a reasonable depth of field coverage while ensuring depth resolution.

[0085] The final detailed design parameters of the long-wave infrared light field camera are as follows: Table 1. Theoretical Parameter Design Table for Infrared Light Field Camera The technical advantages of this embodiment are: It provides a complete and detailed design example with an imaging distance from 10m to 100m and operating in the 8-12μm band. This example demonstrates step by step how to apply all the aforementioned formulas and steps to calculate the specific values ​​of all key parameters (such as the microlens focal length of 1.053mm / 1.003mm / 0.957mm), and finally provides an achievable system parameter table, which is of great engineering reference value.

[0086] Example 8 Based on any of the above embodiments, this embodiment discloses parameter simulation and simulation verification.

[0087] To verify the rationality of the proposed infrared light field camera parameter design and the feasibility of the system structure, the system was simulated and modeled using Zemax optical design software. In the simulation model, the main lens, microlens array, and relay imaging system all adopted ideal lens models to eliminate the influence of specific optical processing errors and aberrations, focusing on verifying the correctness of the system's geometric structure and parameter configuration.

[0088] An infrared light field optical path model was constructed under the condition of an object distance of 100m. The raw light field data was generated using Zemax's geometric bitmap simulation function, and the simulation results were visualized using a light field rendering algorithm. The optical path diagram of the simulation system is shown below. Figure 7 As shown. The white image and the original infrared light field image obtained based on the Zemax geometric bitmap simulation function are shown below. Figure 8 and Figure 9 As shown.

[0089] The white image was obtained by capturing a uniform white light source using a simulated camera. It can be seen that the micro-images formed by the microlenses on the detector plane are arranged in a regular, staggered hexagonal pattern, and the micro-image size is consistent with the designed spacing. Adjacent micro-images are essentially tangent on the detector, with no obvious overlap or gaps, indicating that the microlens aperture and the F-number of the primary lens satisfy the beam cone matching condition. Furthermore, the scale and distribution of the micro-images on the detector plane remain consistent, and no obvious beam clipping or pixel waste at the field of view edges was observed.

[0090] Furthermore, in the original infrared light field image obtained under simulated shooting conditions at 100m, both the target and human body contours can be clearly imaged, and the same object point can be imaged simultaneously by approximately six microlenses, meeting the basic requirements of light field parallax extraction and 3D reconstruction for multi-view imaging. The above simulation results show that the designed optical system can obtain light field data with correct structure and sufficient parallax information under long-distance conditions.

[0091] Based on the aforementioned theoretical analysis and simulation results, it can be seen that, under ideal conditions, the designed light field camera system can achieve a depth-of-field coverage capability on the order of hundreds of meters and target detection at relatively long distances, while possessing high spatial resolution and a reasonable field of view. More importantly, the simulation verification methods and parameter design ideas described above are not limited to specific imaging distances or long-wave infrared bands. By adjusting the parameters of the main lens, microlens array, and detector accordingly, it is also applicable to close-range or mid-range imaging scenarios, as well as the design of focusing light field camera systems in other bands such as visible light and near-infrared.

[0092] The above description is merely a preferred embodiment of the present invention and does not limit the scope of protection of the present invention. Various modifications and variations are possible with respect to the present invention. Any changes, modifications, substitutions, integrations, and parameter alterations to these embodiments within the spirit and principles of the present invention fall within the scope of protection of the claims of the present invention.

Claims

1. A method for designing parameters of a long-wave infrared focusing light field camera, characterized in that, Includes the following steps: Step S1: Based on the thin lens approximation condition, determine the range of the main lens focal length F according to the imaging object distance u and the target size, and select the entrance pupil diameter A of the main lens in combination with the signal-to-noise ratio constraint of the long-wave infrared band, while matching the number of detector pixels M and the pixel size s. Step S2: Determine the geometry of the microlenses. The microlens array adopts a row-aligned, staggered arrangement of hexagonal apertures. The microlens aperture... The constraint formula for the pixel size s is: Where N is the number of pixels covered by a single microlens on the detector plane; Step S3: Determine the position of the microlens; based on the geometric matching relationship between the exit pupil of the main lens and the aperture of the microlens, calculate the distance d between the microlens array and the detector and the axial distance D from the main lens to the microlens array; Step S4: Determine the focal length of the microlens. Based on the characteristics of the long-wave infrared band, determine the working range that the microlens array covers and effectively images, that is, the range of the virtual image position formed by the main lens in the image space. Step S5: Optimize the microlens aperture based on depth resolution.

2. The parameter design method for a long-wave infrared focusing light field camera according to claim 1, characterized in that, The constraint formula for the pixel size s of the detector in step S1 is: ， in, Indicates the radius of the Airy disk. Indicates wavelength. The F-number of the main lens, through calculate.

3. The parameter design method for a long-wave infrared focusing light field camera according to claim 1, characterized in that, The formula for calculating the distance d between the microlens array and the detector in step S3 is as follows: ,in, Let F be the aperture of the microlens array, F be the focal length of the main lens, and A be the entrance pupil diameter of the main lens.

4. The parameter design method for a long-wave infrared focusing light field camera according to claim 1, characterized in that, The formula for calculating the axial distance D from the main lens to the microlens array in step S3 is as follows: ， in, This represents the distance from the entrance pupil of the primary lens to the virtual image point, where n is the number of microlenses in the microlens array, and n≥2. Let F be the aperture of the microlens array, F be the focal length of the main lens, and A be the entrance pupil diameter of the main lens.

5. The parameter design method for a long-wave infrared focusing light field camera according to claim 1, characterized in that, Step S4 includes the following steps: Step S41: Assume the object space imaging distance designed by the system is... According to the thin lens imaging model, the range of the virtual image position formed by the main lens in the image space is the area that needs to be covered and effectively imaged by the microlens array. Step S42: Determine the diameter of the circle of confusion based on the perfected imaging diffraction-limited resolution model. ; Step S43: Based on the similar triangle relationship and the thin lens imaging model, determine the diameter r of the circle of confusion formed on the detector plane after the virtual image point is imaged by the i-th type of microlens; Step S44: Based on the focal length of the first type of microlens Determine the corresponding front and back depth of field boundaries of the image under this focal length condition; Step S45: Determine the constraint relationship of the multifocal microlens array.

6. The parameter design method for a long-wave infrared focusing light field camera according to claim 5, characterized in that, The range of virtual image positions formed by the main lens in the image space in step S41 is expressed as follows: ， Where F is the focal length of the main lens, and D is the axial distance from the main lens to the microlens array. The minimum object-space imaging distance for the system design. The maximum value of the object space imaging distance designed for the system.

7. The parameter design method for a long-wave infrared focusing light field camera according to claim 5, characterized in that, The diameter of the dispersion circle mentioned in step S42 The calculation formula is: ， in, The radius of the smallest resolvable Airy disk formed by the optical system under the diffraction limit is given. For the operating wavelength, denoted by F-number, where s is the F-number of the microlens and s is the pixel size of the detector.

8. The parameter design method for a long-wave infrared focusing light field camera according to claim 5, characterized in that, The formula for calculating the diameter r of the dispersion circle formed by the detector plane in step S43 is as follows: ， in, Let d be the aperture of the microlens array, and d be the distance between the microlens array and the detector. Let the focal length of the i-th type of microlens be i = 1, 2, 3. This is the position of the nearest virtual image on the image side.

9. The parameter design method for a long-wave infrared focusing light field camera according to claim 5, characterized in that, In step S44, the focal length of the first type of microlens Under these conditions, the corresponding foreground and background depth boundaries can be represented as follows: ， ， in, For the deep boundary of the foreground, This represents the boundary of the background depth of field.

10. The parameter design method for a long-wave infrared focusing light field camera according to claim 1, characterized in that, The specific method for step S5 includes the following steps: Step S51: Determine the depth resolution. Combining the imaging geometry of the main lens, map the error in the virtual depth domain to the object space to obtain the object-space depth resolution. The formula is: , in, Let F be the distance from the object to the plane of the primary lens, and F be the focal length of the primary lens. The parallax precision is represented by d, where d is the distance between the microlens array and the detector. This indicates the virtual depth estimation error; Step S52: Determine the virtual depth range. In a hexagonal microlens array, the baseline length between different microlens pairs can be expressed as the microlens aperture and scaling factor k. i The product of these two factors, when used for depth estimation with the i-th level baseline length, results in a virtual depth range that satisfies the following: ， Where, k1=1, k2= k3=2, k4= k5=3, k6= k7= k8=4, k9= k 10 = k 11 =5; Indicates virtual depth.

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