A micro camera with a large field of view and a method for manufacturing the same

Abstract

The application discloses a micro camera with a large visual angle and a preparation method thereof, and belongs to the technical field of micro imaging system design and preparation. The micro camera comprises, from top to bottom, a non-uniform curved micro lens array, a window protection glass and a micro image sensor; the non-uniform curved micro lens array is in the shape of a spherical cap and is composed of a spherical base, a central sub-lens and surrounding sub-lenses; the central sub-lens is located at the top of the spherical cap, the surrounding sub-lenses are distributed along the latitudes, and the focal length of the surrounding sub-lenses changes along the latitudes. The non-uniform curved micro lens array is used to replace a traditional multi-lens composite lens, so that a large visual angle and low aberration can be realized under micro scale; the non-uniform curved micro lens array can be directly processed and integrated to the surface of the micro image sensor without additional assembly and alignment; and the profile of the sub-lens is designed to obtain a non-uniform focal length of the sub-lens, so that the sub-lenses with different orientations can focus and image on the same plane, and the defocus problem of the curved focal plane of the curved micro lens array and the planar detector during integration is overcome.

Description

Technical Field

[0001] This invention belongs to the field of micro imaging system design and fabrication technology, specifically relating to a micro camera with a large field of view and its fabrication method. Background Technology

[0002] Miniature cameras possess significant advantages such as small size, light weight, and low power consumption, and hold great promise for applications in fields such as in vivo disease diagnosis and treatment, military camouflage and reconnaissance, visual perception in miniature robots, and internal inspection of precision components. Among these, the optical lens, as the core component of a miniature camera, is a key factor influencing its performance and determining its development potential. A typical example is... Figure 1 As shown, traditional cameras use composite lenses assembled from multiple lenses to correct aberrations and improve image quality. However, the design and fabrication of lens structures at the microscale are greatly limited, making it difficult to achieve the goal of high-quality imaging at microscale.

[0003] Curved microlens arrays possess outstanding advantages such as large field of view, low aberration, dynamic target detection, small size, and light weight. Therefore, using curved microlens arrays to replace traditional complex lens combinations in constructing miniature cameras is an ideal choice for achieving large field of view and low aberration imaging at the microscale. Over the past decade, thanks to advancements in various advanced microfabrication technologies, the fabrication of curved microlens arrays has become relatively mature. For example, Wu and Ma et al. used femtosecond laser 3D printing technology to fabricate customized aspherical and tunable curved microlens arrays, enabling low aberration and zoom imaging with a large field of view. Furthermore, a combined fabrication process based on photoresist thermal reflow, inkjet printing, and laser-modified etching techniques to obtain planar microlens arrays, and then transferring them to curved substrates using techniques such as thermal embossing and air-assisted deformation, can achieve high-throughput rapid fabrication of large-size curved microlens arrays with ultra-high lens counts. The high-quality fabrication of curved microlens arrays has laid the foundation for the realization of miniaturized cameras. However, the curved microlens array devices fabricated above can only function as independent optical lenses. Their imaging performance usually needs to be evaluated using a microscope image acquisition system, and they have not yet been integrated and applied with photodetectors.

[0004] A complete miniature camera must integrate optical lenses and electronic image sensors. Early miniature microlens array cameras primarily utilized the multi-aperture imaging capabilities of lens arrays to achieve functions such as 3D reconstruction and super-resolution imaging. However, limited by their planar structural characteristics, planar microlens arrays suffer from fatal flaws in terms of field of view. Theoretically, if... Figure 2As shown, curved microlens arrays possess a large field of view, but the focal plane of such arrays is also curved. Therefore, fabricating miniature cameras based on curved microlens arrays is challenging, requiring precise alignment of the focal plane of the array and the photosensitive chip on the curved surface. To address the defocusing problem of curved microlens arrays, curved image sensors are a viable alternative. For example, Rogers and Lee et al. integrated microlens arrays with flexible silicon photodiode arrays on a spherical structure to fabricate a small camera with a large field of view. Despite the immense potential of curved detectors, current fabrication techniques are not yet mature enough to achieve high-resolution imaging and device miniaturization. Optical relay lenses and relay waveguides offer effective solutions for integration with high-resolution planar detectors, but these also suffer from system complexity, assembly and alignment difficulties, and low integration density. To date, the fabrication of large field-of-view miniature cameras based on curved microlens arrays remains a significant challenge. Summary of the Invention

[0005] Traditional miniature cameras utilize composite lenses assembled from multiple lenses to correct aberrations and achieve high-quality imaging. However, at the microscale, the design and manufacturing of composite lenses are limited by spatial dimensions, making it difficult to achieve large field of view and low aberration imaging targets at the microscale, which greatly restricts the further development of miniature cameras. This invention provides a miniature camera with a large field of view and its fabrication method. This invention uses a non-uniform curved surface microlens array to replace the traditional multi-lens composite lens, which can achieve a large field of view and low aberration at the microscale. The non-uniform curved surface microlens array can be directly processed and integrated onto the surface of a miniature image sensor without additional assembly and alignment. By designing the contours of the sub-lenses, a non-uniform sub-lens focal length is obtained, so that sub-lenses with different orientations can focus and image onto the same plane, overcoming the defocusing problem when the curved focal plane of the curved surface microlens array is integrated with a planar detector.

[0006] This invention is achieved through the following technical solution:

[0007] A miniature camera with a large field of view includes, from top to bottom, a non-uniform curved surface microlens array 1, a window protective glass 2, and a miniature image sensor 3; the non-uniform curved surface microlens array 1 is spherical and consists of a spherical base 6 and a central sub-lens 4 and peripheral sub-lens 5 located thereon; the central sub-lens 4 is located at the apex of the spherical cap, and the peripheral sub-lens 5 are distributed along the latitude lines, with the focal length of the peripheral sub-lens 5 varying along the latitude.

[0008] Furthermore, the focal lengths of the central sub-lens 4 and the surrounding sub-lens 5 are defined sequentially as F1, F2, F3...F... N The focal lengths of the central sub-lens 4 and the surrounding sub-lens 5 are determined by the following formula:

[0009]

[0010] Where R and n are the radius of curvature of the sub-lens and the refractive index of the material, respectively.

[0011] Furthermore, the field of view (FOV) of the curved microlens array 1 ranges from 60 to 180°, the diameter (D) of the spherical base 6 ranges from 100 μm to 5 cm, and the height (H) of the spherical base ranges from 100 μm to 5 cm; the number (N) of the central sub-lens 4 and surrounding sub-lens 5 ranges from 10 to 10,000, the focal length (F) of the central sub-lens 4 and surrounding sub-lens 5 ranges from 100 μm to 10 cm, the radius of curvature (R) of the central sub-lens 4 and surrounding sub-lens 5 ranges from 50 μm to 5 cm, the refractive index (n) of the material of the central sub-lens 4 and surrounding sub-lens 5 ranges from 1.0 to 2.3, the height (h) of the central sub-lens 4 and surrounding sub-lens 5 ranges from 5 μm to 1 mm, and the radius (r) of the central sub-lens 4 and surrounding sub-lens 5 ranges from 10 μm to 2 mm.

[0012] On the other hand, the present invention also provides a method for fabricating a miniature camera with a large field of view, specifically including the following steps:

[0013] (1) Data conversion of the processing of curved microlens arrays;

[0014] The specific steps are as follows: First, based on the determined design parameters of the curved microlens array 1, the surface contour height information of the curved microlens array 1 is calculated; then, through programming software, a conversion program is written to convert the surface contour information of the device into three-dimensional point cloud data that the processing system can recognize and process, and trajectory optimization is performed to avoid large jumps between points; the format of the exported three-dimensional point cloud processing data is (X,Y,Z,L), where X, Y, and Z are the three-dimensional spatial coordinates of the point, and L is the opening and closing state of the shutter, where 0 represents the shutter being closed and 1 represents the shutter being open;

[0015] (2) Sample preparation;

[0016] The specific steps are as follows: Sample preparation is divided into two types:

[0017] Using the miniature image sensor 3 as a processing substrate, optoelectronic integration fabrication of a large field of view, low aberration miniature camera can be achieved without additional assembly and alignment. The protective tape on the surface of the miniature image sensor 3 is removed, and ultrasonic cleaning is performed for a certain period to remove large glass fragments and dust particles from the surface of the window protective glass 2, preventing light scattering during processing and affecting processing quality. The surface is then repeatedly wiped unidirectionally with cotton balls soaked in acetone and anhydrous ethanol, followed by rinsing with deionized water, and finally placed in a vacuum drying oven for drying. Photosensitive resin is then dropped onto or spin-coated onto the surface of the cleaned and dried miniature image sensor 3. Based on the polymerization principle of the photosensitive resin, a pre-baking treatment is selected.

[0018] (3) Femtosecond laser 3D printing and optoelectronic integration of curved microlens arrays;

[0019] The specific steps are as follows:

[0020] Femtosecond laser 3D printing and integration of curved microlens array 1:

[0021] The prepared sample was loaded into the galvanometer-based femtosecond laser 3D printing system; the sample was moved by the electronically controlled precision displacement stage, and the four boundaries of the square sample were found in turn. Then, the midpoint of each direction was determined by calculation based on the sample boundary position, and the center position of the sample was finally located. The curved microlens array was directly prepared at the center position of the sample without additional assembly and alignment; before formal processing, the laser was focused on the position of the interface between the photosensitive resin film and the sample sheet as the starting interface for processing; then, the three-dimensional point cloud text file of the curved microlens array obtained in step (1) was imported, and the appropriate laser processing power and single-point exposure time were selected to start point-by-point scanning processing to prepare the curved microlens array 1;

[0022] (4) Development, drying and post-processing of the devices:

[0023] The processed sample was immersed in the developing solution for development; after development, the sample was removed from the developing solution and dried naturally; the dried sample was exposed to a high-power ultraviolet lamp. The unexposed resin polymerization during the femtosecond laser direct writing process played a role in uniformizing the refractive index of the structure and improving the long-term stability of the structure. Finally, a micro-camera based on an optoelectronic integrated curved microlens array was prepared.

[0024] Furthermore, in step (1), the programming languages ​​used include MATLAB, C++, C#, or Visual Basic.

[0025] Further, in step (2), the ultrasonic cleaning solution is an organic solvent such as acetone, ethanol, isopropanol, n-propanol, cyclopentanone, tetrahydrofuran, etc.; the ultrasonic cleaning temperature is 25-65℃ and the ultrasonic cleaning time is 5-60min; the vacuum drying temperature is 60-150℃ and the drying time is 5-30min; the sample preheating temperature is 65-120℃ and the heating time is 20-120min.

[0026] Furthermore, in step (2), the femtosecond laser 3D printing photosensitive resin mainly includes: epoxy resin SU-8, organic-inorganic hybrid photoresist ip-dip, sz2080, ultraviolet optical curing adhesive NOA61, NOA63, etc.

[0027] Further, in step (3), the galvanometer-based femtosecond laser 3D printing system includes a fiber femtosecond laser oscillator, an attenuator, an optical shutter, a reflector, a beam expander, a scanning galvanometer, a 4F optical system, and an oil immersion objective. The femtosecond pulsed laser generated by the femtosecond laser oscillator passes sequentially through the attenuator and the optical shutter, then through the reflector and the beam expander. The expanded laser beam is deflected at an angle controlled by the scanning galvanometer, and then the 4F optical system projects the laser beam onto the entrance pupil of the oil immersion objective. The beam is focused into the interior of the sample through the oil immersion objective and combined with the movement of the displacement stage to achieve three-dimensional scanning. At the same time, a real-time monitoring system consisting of an illumination source, a filter, and an imaging CCD is used to observe the status of the sample during the processing in real time.

[0028] Furthermore, in step (3), in the galvanometer-based femtosecond laser 3D printing system, the center wavelength of the femtosecond laser is 450-1050nm, the pulse width is 80-500fs, the repetition frequency is 90KHz-100MHz, the magnification of the processing objective is 4-120 times, the numerical aperture is 0.1-1.5, the laser processing power is 5-28mw, and the single-point exposure time is 100-3000μs.

[0029] Further, in step (3), the developing solution includes organic solvents such as ethanol, isopropanol, tetrahydrofuran, acetone, toluene, and propylene glycol methyl ether acetate; the developing temperature is 25-65℃; the developing time is 10-90min; the ultraviolet lamp used for ultraviolet exposure has a wavelength of 300-450nm, a power of 0.5-10W, and an exposure time of 10s-60min.

[0030] In step (3), the image plane size of the miniature image sensor 3 is (100μm-20mm) x (100μm-20mm), and the size of a single pixel is (0.1μm-3μm) x (0.1μm-3μm).

[0031] Compared with the prior art, the advantages of the present invention are as follows:

[0032] (1) A micro camera with a large field of view and its manufacturing method of the present invention uses a curved microlens array to replace the traditional multi-lens combination lens, and achieves low aberration imaging with a larger field of view in a smaller device size.

[0033] (2) A non-uniform curved surface microlens array design is proposed. By carefully designing the sub-lens profile, a non-uniform sub-lens focal length is obtained, so that sub-lenses with different orientations can be focused and imaged onto the same plane. This effectively solves the defocusing problem of integrating curved surface microlens arrays with micro planar detectors and realizes optoelectronic integration with micro planar image sensors.

[0034] (3) By using femtosecond 3D printing technology to directly fabricate the designed non-uniform curved surface microlens array on the surface of the micro image sensor, the required three-dimensional morphology and optical-grade processing quality can be obtained, realizing high-quality fabrication and direct optoelectronic integration of the lens structure without the need for additional assembly and alignment.

[0035] (4) The large field-of-view miniature camera can achieve large field-of-view and low aberration imaging in a compact size, and has the outstanding advantages of simple structural design, universal method and strong applicability. Attached Figure Description

[0036] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the accompanying drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. In all the 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.

[0037] Figure 1 This is a schematic diagram of the structure of the large field-of-view micro-camera based on a non-uniform curved surface microlens array according to the present invention;

[0038] Figure 2 This is a schematic diagram illustrating the focusing principle of a traditional curved surface microlens array.

[0039] Figure 3 This is a schematic diagram illustrating the focusing principle of the non-uniform curved surface microlens array of the present invention;

[0040] Figure 4 This is a schematic diagram of the composition of the galvanometer-based femtosecond laser 3D printing system of the present invention;

[0041] Figure 5 This is a schematic diagram illustrating the principle of directly fabricating and integrating a non-uniform curved surface microlens array onto the surface of a miniature image sensor according to the present invention.

[0042] Figure 6 The morphology characterization results of the non-uniform curved surface microlens array prepared in this invention are shown.

[0043] Wherein, a is a schematic diagram of an optical microscope, b is a schematic diagram of a fluorescence microscope, and c is a schematic diagram of a scanning electron microscope;

[0044] Figure 7 This is a schematic diagram of the optical path for testing the defocus-free imaging performance of the non-uniform curved surface microlens array of the present invention.

[0045] Figure 8 This is a schematic diagram of the imaging results of the non-uniform curved surface microlens array of the present invention on the bright field mask;

[0046] Where a is a schematic diagram of the letter F, and b is a schematic diagram of the bar pattern;

[0047] Figure 9 This is a schematic diagram of the imaging results of the non-uniform curved surface microlens array of the present invention on the dark field mask;

[0048] Where a is a schematic diagram of the letter F, and b is a schematic diagram of the bar pattern;

[0049] Figure 10 This is a schematic diagram of the optical path for testing the large field-of-view imaging performance of the non-uniform curved surface microlens array of the present invention;

[0050] Figure 11 The intensity distribution of the focused light field of the non-uniform curved surface microlens array of the present invention under different incident angles;

[0051] Where a is 0°, b is 22.5°, and c is 45°;

[0052] Figure 12 A photograph of the curved microlens array-based microcamera fabricated according to the present invention;

[0053] Figure 13 This is a schematic diagram illustrating the dynamic target detection principle of the large field-of-view miniature camera prepared according to the present invention;

[0054] Figure 14 The images show dynamic target images at different times captured by the large field-of-view miniature camera prepared according to the present invention. Detailed Implementation

[0055] To clearly and completely describe the technical solution and its specific working process of the present invention, the specific embodiments of the present invention are as follows, in conjunction with the accompanying drawings:

[0056] Example 1

[0057] This embodiment provides a miniature camera with a large field of view, which includes, from top to bottom, a non-uniform curved surface microlens array 1, a window protective glass 2, and a miniature image sensor 3; the non-uniform curved surface microlens array 1 is spherical and consists of a spherical base 6 and a central sub-lens 4 and peripheral sub-lens 5 located thereon; the central sub-lens 4 is located at the apex of the spherical cap, and the peripheral sub-lens 5 are distributed along the latitude lines, with the focal length of the peripheral sub-lens 5 varying along the latitude.

[0058] The focal lengths of the central sub-lens 4 and the surrounding sub-lens 5 are defined as F1, F2, F3...F... N The focal lengths of the central sub-lens 4 and the surrounding sub-lens 5 can be determined using the following formula:

[0059]

[0060] Where R and n are the radius of curvature of the sub-lens and the refractive index of the material, respectively.

[0061] The curved microlens array 1 has a field of view (FOV) ranging from 60 to 180°, a diameter (D) of a spherical base 6 ranging from 100 μm to 5 cm, and a height (H) of a spherical base ranging from 100 μm to 5 cm. The number (N) of the central sub-lens 4 and surrounding sub-lens 5 ranges from 10 to 10,000. The focal length (F) of the central sub-lens 4 and surrounding sub-lens 5 ranges from 100 μm to 10 cm. The radius of curvature (R) of the central sub-lens 4 and surrounding sub-lens 5 ranges from 50 μm to 5 cm. The refractive index (n) of the material of the central sub-lens 4 and surrounding sub-lens 5 ranges from 1.0 to 2.3. The height (h) of the central sub-lens 4 and surrounding sub-lens 5 ranges from 5 μm to 1 mm. The radius (r) of the central sub-lens 4 and surrounding sub-lens 5 ranges from 10 μm to 2 mm.

[0062] Example 2

[0063] This embodiment proposes a microcamera based on a curved microlens array, breaking the inherent limitations of traditional composite lens-based microcameras. Using a curved microlens array to replace traditional multi-lens composite lenses is an ideal choice for achieving large field of view and low aberrations at the microscale. The non-uniform curved microlens array proposed in this embodiment can be fabricated using femtosecond laser 3D printing technology to obtain the required three-dimensional morphology and optical-grade processing quality, enabling large field-of-view and low-aberration imaging at the microscale.

[0064] This embodiment describes a method for fabricating a curved microlens array with a large field of view and low aberrations. The specific steps are as follows:

[0065] (1) Design of a large field-of-view curved surface microlens array;

[0066] Specific steps: First, select a field of view (FOV) greater than 90° for the curved microlens array 1, and determine the dimensional parameters of the spherical base 6 of the curved microlens array 1 based on the selected field of view parameter, including the diameter and height of the spherical base 6, using the following formula:

[0067]

[0068] Where D and H are the diameter and height of the spherical base 6, respectively. The diameter of the spherical base 6 is determined to be 290 μm and the height to be 75 μm. After determining the field of view of the curved microlens array 1, that is, after determining the diameter and height of the spherical base 6, it is also necessary to determine the size and focal length of the central sub-lens 4 and the surrounding sub-lens 5 to ensure that the central sub-lens 4 and the surrounding sub-lens 5 arranged on the curved surface can be focused and imaged onto the same plane. From the top to the edge of the spherical base 6, the central sub-lens 4 and the surrounding sub-lens 5 are defined as L1, L2, and L3 respectively, and their focal lengths are defined as F1, F2, and F3 respectively. There are a total of 19 central sub-lens 4 and surrounding sub-lens 5. The focal lengths of the central sub-lens 4 and the surrounding sub-lens 5 are calculated by formula (1) to obtain the focal lengths of the central sub-lens 4 with different orientations: F1 = 525 μm, F2 = 552 μm, F3 = 659 μm, and the refractive index of the material is n = 1.5.

[0069] Furthermore, based on the radius of curvature of the corresponding oriented sub-lens 4, the dimensional parameters of the central sub-lens 4 and the surrounding sub-lens 5 are determined, including the radius and height of the central sub-lens 4 and the surrounding sub-lens 5. This can be determined using the following formula:

[0070] R 2 =(Rh) 2 +r 2 (3)

[0071] Where h and r are the height and radius of the central sub-lens 4 and the surrounding sub-lens 5, respectively. The radius r of the central sub-lens 4 and the surrounding sub-lens 5 is 20 μm. Based on the above parameters, the surface profile height information of the entire curved microlens array 1 can be determined.

[0072] (2) Data conversion of curved surface microlens array processing:

[0073] Specific steps: First, based on the design parameters of the curved microlens array 1 determined in step (1), the surface contour height information of the curved microlens array 1 is calculated. Then, using the programming language C#, a conversion program is written to convert the surface contour information of the device into three-dimensional point cloud data that the processing system can recognize and process, and trajectory optimization is performed to avoid large jumps between points. The format of the exported three-dimensional point cloud processing data is (X,Y,Z,L), where X, Y, and Z are the three-dimensional spatial coordinates of the point, and L is the on / off state of the shutter, where 0 represents the shutter being closed and 1 represents the shutter being open.

[0074] (3) Sample preparation:

[0075] Specific steps: A microscope coverslip was used as the substrate for the non-integrated curved microlens array 1. It was ultrasonically cleaned in acetone solution at 25°C for 20 minutes to remove large glass fragments and dust particles from the glass surface, preventing light scattering during processing and affecting the processing quality. The substrate was then repeatedly wiped unidirectionally with cotton balls soaked in acetone and anhydrous ethanol, followed by rinsing with deionized water. Finally, it was placed in a vacuum drying oven and vacuum-dried at 65°C for 20 minutes. An organic-inorganic hybrid photoresist SZ2080 was spin-coated onto the cleaned and dried substrate surface. The sample after spin-coating the photosensitive resin was placed on a constant-temperature heating stage and pre-baked at 95°C for 60 minutes. The pre-baked sample was then allowed to cool naturally for later use.

[0076] When characterizing and testing curved microlens arrays, the following preprocessing method is used:

[0077] A microscope coverslip was used as the processing substrate for the non-integrated curved microlens array 1, allowing for the separate characterization and testing of the curved microlens array. Ultrasonic cleaning for a certain period removed large glass fragments and dust particles from the glass surface to prevent light scattering during processing and its impact on quality. The substrate was then repeatedly wiped unidirectionally with cotton balls soaked in acetone and anhydrous ethanol, followed by rinsing with deionized water, and finally dried in a vacuum drying oven. Photosensitive resin was then drop-on or spin-coated onto the cleaned and dried substrate surface. Pre-baking was selected based on the polymerization principle of the photosensitive resin.

[0078] (4) Femtosecond laser 3D printing of curved microlens arrays:

[0079] Specific steps:

[0080] Femtosecond laser 3D printing and integration of curved microlens array 1:

[0081] Load the previously prepared samples into such a container. Figure 4The galvanometer-based femtosecond laser 3D printing system is shown. In this system, the femtosecond laser has a center wavelength of 780 nm, a pulse width of 150 fs, and a repetition rate of 80 MHz. The laser beam passes sequentially through an attenuator and a shutter, then through a mirror and a beam expander, resulting in a beam size five times larger. A scanning galvanometer controls the deflection angle of the laser beam, which is then projected onto the entrance pupil of the objective lens by a 4F optical system. The objective lens has a magnification of 60x and a numerical aperture of 1.35. A reflective imaging system within the system images the surface of the sample. An electrically controlled precision displacement stage moves the sample, sequentially locating the four boundaries of the square sample. Based on the boundary positions, the midpoint in each direction is calculated, ultimately determining the center of the sample. Figure 5 As shown, a curved microlens array 1 is directly fabricated at the center of the sample. Before formal processing, the laser is focused at the interface between the polymer film and the substrate, and this position is used as the starting interface for processing. Then, the three-dimensional point cloud text file of the curved microlens array 1 obtained in step (2) is imported, the laser processing power is selected as 18Mw and the single-point exposure time is 300μs, and point-by-point scanning processing is started to fabricate the designed curved microlens array 1.

[0082] Developing, drying and post-processing of the device:

[0083] The processed sample was developed in n-propanol at room temperature for 20 minutes. After development, the sample was removed from the developer and allowed to air dry. The dried sample was then exposed to a high-power ultraviolet lamp with a wavelength of 395 nm, a power of 2 W, and an exposure time of 1 minute. A large field-of-view, low-aberration curved microlens array1 was finally fabricated.

[0084] Depend on Figure 6 It can be seen that the prepared non-uniform curved variable focal length microlens array 1 has a smooth surface, complete structure, good morphology, and good overall preparation effect.

[0085] Depend on Figure 8 It can be seen that the non-uniform curved variable focal length microlens array 1 designed and fabricated has a good imaging effect on the bright field mask, and the sub-lenses 4 with different orientations have uniform imaging.

[0086] Depend on Figure 9 It can be seen that the non-uniform curved surface variable focal length microlens array 1 designed and fabricated has good imaging effect on dark field masks, and the imaging of sub-lenses with different orientations is uniform.

[0087] Depend on Figure 11 It can be seen that the non-uniform curved variable focal length microlens array 1 designed and fabricated has a uniform distribution of focused light field intensity under different viewing angles and small aberrations under a large field of view.

[0088] Example 3

[0089] Replacing traditional multi-lens composite lenses with curved microlens arrays is an ideal choice for achieving large field of view and low aberrations at the microscale. For example... Figure 3 As shown, to overcome the defocusing problem when integrating the curved focal plane of a curved microlens array with a planar detector, the contours of the sub-lenses are designed to obtain non-uniform sub-lens focal lengths, enabling sub-lenses with different orientations to focus and image onto the same plane. Simultaneously, the proposed non-uniform curved microlens array can be fabricated using femtosecond laser 3D printing technology to achieve the required three-dimensional morphology and optical-grade processing quality. In particular, the designed non-uniform curved microlens array can be directly fabricated and integrated onto the surface of a miniature image sensor, enabling the universal fabrication of miniature cameras with large field-of-view cameras without additional assembly and alignment.

[0090] This embodiment provides a method for fabricating a miniature camera with a large field of view, the specific steps of which are as follows:

[0091] Steps (1) and (2) are the same as in Example 1.

[0092] (3) Sample preparation

[0093] Specific steps: Remove the protective tape from the surface of the miniature image sensor 3. The miniature image sensor 3 is a CMOS photosensitive chip, model Omnivision 9734, with an imaging area of ​​1820μm*1033μm and a pixel size of 1.4μm*1.4μm. Clean it ultrasonically in acetone solution at 25℃ for 20 minutes to remove large glass fragments and dust particles from the surface of the window protective glass 2, preventing light scattering during processing and affecting processing quality. Wipe repeatedly in one direction with cotton balls soaked in acetone and anhydrous ethanol, followed by rinsing with deionized water. Finally, place it in a vacuum drying oven and vacuum dry at 65℃ for 20 minutes. Spin-coat the surface of the cleaned and dried miniature image sensor 3 with an organic-inorganic hybrid photoresist SZ2080. Place the sample with the spin-coated photosensitive resin on a constant temperature heating stage and pre-bake at 95℃ for 60 minutes. After pre-baking, allow the sample to cool naturally for later use.

[0094] (4) Femtosecond laser 3D printing and optoelectronic integration of curved microlens arrays

[0095] Specific steps:

[0096] Femtosecond laser 3D printing and integration of curved microlens array 1:

[0097] Load the previously prepared samples into such a container. Figure 4The galvanometer-based femtosecond laser 3D printing system is shown. In this system, the femtosecond laser has a center wavelength of 780 nm, a pulse width of 150 fs, and a repetition rate of 80 MHz. The laser beam passes sequentially through an attenuator and a shutter, then through a mirror and a beam expander, resulting in a beam size five times larger. A scanning galvanometer controls the deflection angle of the laser beam, which is then projected onto the entrance pupil of the objective lens by a 4F optical system. The objective lens has a magnification of 60x and a numerical aperture of 1.35. A reflective imaging system within the system images the surface of the sample. An electrically controlled precision displacement stage moves the sample, sequentially locating the four boundaries of the square sample. Based on the boundary positions, the midpoint in each direction is calculated, ultimately determining the center of the sample. Figure 7 As shown, a curved microlens array 1 is directly fabricated at the center of the sample. Before formal processing, the laser is focused at the interface between the polymer film and the substrate, and this position is used as the starting interface for processing. Then, the three-dimensional point cloud text file of the curved microlens array 1 obtained in step (3) is imported, the laser processing power is selected as 18Mw and the single-point exposure time is 300μs, and point-by-point scanning processing is started to fabricate the designed curved microlens array.

[0098] Developing, drying and post-processing of the device:

[0099] The processed sample was developed in n-propanol at room temperature for 20 minutes. After development, the sample was removed from the developer and allowed to air dry. The dried sample was then exposed to a high-power ultraviolet lamp with a wavelength of 395 nm, a power of 2 W, and an exposure time of 1 minute. This resulted in the fabrication of a photoelectric integrated curved microlens array-based miniature camera.

[0100] like Figure 5 As shown, the designed non-uniform curved surface microlens array 1 can be directly fabricated and integrated onto the surface of the micro image sensor 3 using femtosecond laser 3D printing technology, achieving optoelectronic integration fabrication of a micro camera with a large field of view and low aberrations without additional assembly and alignment.

[0101] like Figure 12 As shown, the fabricated large field-of-view, low-aberration miniature camera has a compact structure, small size, light weight, and high integration, with a total mass of less than 250 mg.

[0102] Example 4

[0103] Replacing traditional multi-lens composite lenses with curved microlens arrays is an ideal choice for achieving large field of view and low aberrations at the microscale. For example... Figure 2As shown, to overcome the defocusing problem when integrating the curved focal plane of a curved microlens array with a planar detector, the contours of the sub-lenses are designed to obtain non-uniform sub-lens focal lengths, enabling sub-lenses with different orientations to focus and image onto the same plane. Simultaneously, the proposed non-uniform curved microlens array can be fabricated using femtosecond laser 3D printing technology to achieve the required three-dimensional morphology and optical-grade processing quality. In particular, the designed non-uniform curved microlens array can be directly fabricated and integrated onto the surface of a miniature image sensor, enabling the universal fabrication of a large field-of-view miniature camera without additional assembly and alignment. Finally, the fabricated large field-of-view miniature camera is used to achieve dynamic target detection, breaking the limitations of traditional miniature camera field of view and realizing low-aberration dynamic target detection within a 90° field of view.

[0104] This embodiment provides a method for fabricating a miniature camera with a large field of view, low aberration, and dynamic target detection. The specific steps are as follows:

[0105] Steps (1), (2), (3), and (4) are the same as in Example 2.

[0106] The miniature camera with a large field of view, low aberration, and dynamic target detection observes a moving crab pattern optical mask.

[0107] Depend on Figure 13 It can be seen that the large field of view and low aberration miniature camera prepared in this embodiment can be used to detect the motion of dynamic targets within a large field of view.

[0108] Depend on Figure 14 It can be seen that the large field of view and low aberration miniature camera prepared in this embodiment can acquire motion images of the observed target at different times, and realize real-time tracking and detection of dynamic targets under a large field of view.

[0109] The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the specific details of the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0110] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0111] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A miniature camera with a large field of view, characterized in that, From top to bottom, it includes a non-uniform curved surface microlens array (1), a window protective glass (2), and a miniature image sensor (3); the non-uniform curved surface microlens array (1) is spherical and consists of a spherical base (6) and a central sub-lens (4) and peripheral sub-lenses (5) located on it; the central sub-lens (4) is located at the apex of the spherical cap, and the peripheral sub-lenses (5) are distributed along the latitude lines, with the focal length of the peripheral sub-lenses (5) varying along the latitude; The focal lengths of the central sub-lens (4) and the surrounding sub-lens (5) are defined as F1, F2, F3...F... N The focal lengths of the central sub-lens (4) and the surrounding sub-lens (5) are determined by the following formula: Where R and n are the radius of curvature of the sub-lens and the refractive index of the material, respectively; The field of view (FOV) of the curved microlens array (1) ranges from 60 to 180°, the diameter D of the spherical base 6 ranges from 100 μm to 5 cm, and the height H of the spherical base ranges from 100 μm to 5 cm; the number N of the central sub-lens (4) and the surrounding sub-lens (5) ranges from 10 to 10,000, the focal length F of the central sub-lens (4) and the surrounding sub-lens (5) ranges from 100 μm to 10 cm, the radius of curvature R of the central sub-lens (4) and the surrounding sub-lens (5) ranges from 50 μm to 5 cm, the refractive index n of the material of the central sub-lens (4) and the surrounding sub-lens (5) ranges from 1.0 to 2.3, the height h of the central sub-lens (4) and the surrounding sub-lens (5) ranges from 5 μm to 1 mm, and the radius r of the central sub-lens (4) and the surrounding sub-lens (5) ranges from 10 μm to 2 mm; Ultimately, a non-uniform sub-lens focal length is obtained, enabling sub-lenses with different orientations to focus and image onto the same plane.

2. The method for fabricating a miniature camera with a large field of view as described in claim 1, characterized in that, Specifically, the steps include the following: (1) Data conversion of the processing of curved microlens arrays; The specific steps are as follows: First, based on the determined design parameters of the curved microlens array (1), the surface contour height information of the curved microlens array (1) is calculated; then, through programming software, a conversion program is written to convert the surface contour information of the device into three-dimensional point cloud data that the processing system can recognize and process, and trajectory optimization is performed to avoid large jumps between points; the format of the exported three-dimensional point cloud processing data is (X,Y,Z,L), where X, Y, and Z are the three-dimensional spatial coordinates of the point, and L is the opening and closing state of the shutter, where 0 represents the shutter being closed and 1 represents the shutter being open; (2) Sample preparation; The specific steps are as follows: Sample preparation is divided into two types: Using a miniature image sensor (3) as a processing substrate, optoelectronic integration fabrication of a miniature camera with a large field of view and low aberration can be achieved without additional assembly and alignment; the protective tape on the surface of the miniature image sensor (3) is removed, and ultrasonic cleaning is performed for a certain period of time to remove large glass fragments and dust particles on the surface of the window protective glass (2) to avoid light scattering during processing and affecting the processing quality; the cotton balls soaked in acetone and anhydrous ethanol are used to wipe the surface repeatedly in one direction, followed by rinsing with deionized water, and finally placed in a vacuum drying oven to dry; photosensitive resin is dropped or spin-coated onto the surface of the cleaned and dried miniature image sensor (3), and pre-baking treatment is selected according to the polymerization principle of photosensitive resin; (3) Femtosecond laser 3D printing and optoelectronic integration of curved microlens arrays; The specific steps are as follows: Femtosecond laser 3D printing and integration of curved microlens array (1): The prepared sample was loaded into the galvanometer-based femtosecond laser 3D printing system; the sample was moved by the electronically controlled precision displacement stage, and the four boundaries of the square sample were found in turn. Then, the midpoint of each direction was determined by calculation based on the sample boundary position, and the center position of the sample was finally located. The curved microlens array was directly prepared at the center position of the sample without additional assembly and alignment; before formal processing, the laser was focused on the interface between the photosensitive resin film and the sample sheet as the starting interface for processing; then, the three-dimensional point cloud text file of the curved microlens array obtained in step (1) was imported, and the appropriate laser processing power and single-point exposure time were selected to start point-by-point scanning processing to prepare the curved microlens array (1); (4) Development, drying and post-processing of the devices: The processed sample was immersed in the developing solution for development; after development, the sample was removed from the developing solution and dried naturally; the dried sample was exposed to a high-power ultraviolet lamp. The unexposed resin polymerization during the femtosecond laser direct writing process played a role in uniformizing the refractive index of the structure and improving the long-term stability of the structure. Finally, a micro-camera based on an optoelectronic integrated curved microlens array was prepared.

3. The method for fabricating a miniature camera with a large field of view as described in claim 2, characterized in that, In step (1), the programming languages ​​used include MATLAB, C++, C#, or Visual Basic.

4. The method for fabricating a miniature camera with a large field of view as described in claim 2, characterized in that, In step (2), the ultrasonic cleaning solution is an organic solvent such as acetone, ethanol, isopropanol, n-propanol, cyclopentanone, or tetrahydrofuran; the ultrasonic cleaning temperature is 25-65℃ and the ultrasonic cleaning time is 5-60 min; the vacuum drying temperature is 60-150℃ and the drying time is 5-30 min; the sample preheating temperature is 65-120℃ and the heating time is 20-120 min.

5. The method for fabricating a miniature camera with a large field of view as described in claim 2, characterized in that, In step (2), the femtosecond laser 3D printing photosensitive resin mainly includes: epoxy resin SU-8, organic-inorganic hybrid photoresist ip-dip, sz2080, and ultraviolet optical curing adhesive NOA61, NOA63.

6. The method for fabricating a miniature camera with a large field of view as described in claim 2, characterized in that, In step (3), the galvanometer-based femtosecond laser 3D printing system includes a fiber femtosecond laser oscillator, an attenuator, an optical shutter, a reflector, a beam expander, a scanning galvanometer, a 4F optical system, and an oil immersion objective. The femtosecond pulsed laser generated by the femtosecond laser oscillator passes through the attenuator and the optical shutter in sequence, and then through the beam expander after passing through the reflector. The expanded laser beam is deflected at an angle controlled by the scanning galvanometer, and then the 4F optical system projects the laser beam onto the entrance pupil of the oil immersion objective. The beam is focused into the interior of the sample through the oil immersion objective and combined with the movement of the displacement stage to achieve three-dimensional scanning. At the same time, a real-time monitoring system consisting of an illumination source, a filter, and an imaging CCD is used to observe the status of the sample during the processing in real time.

7. The method for fabricating a miniature camera with a large field of view as described in claim 2, characterized in that, In step (3), in the galvanometer-based femtosecond laser 3D printing system, the center wavelength of the femtosecond laser is 450-1050nm, the pulse width is 80-500fs, the repetition frequency is 90KHz-100MHz, the magnification of the processing objective is 4-120 times, the numerical aperture is 0.1-1.5, the laser processing power is 5-28mw, and the single-point exposure time is 100-3000μs.

8. The method for fabricating a miniature camera with a large field of view as described in claim 2, characterized in that, In step (3), the developing solution includes organic solvents such as ethanol, isopropanol, tetrahydrofuran, acetone, toluene, and propylene glycol methyl ether acetate. The developing temperature is 25-65℃, and the developing time is 10-90 min. The ultraviolet lamp used for ultraviolet exposure has a wavelength of 300-450 nm, a power of 0.5-10 W, and an exposure time of 10 s-60 min. In step (3), the image plane size of the miniature image sensor 3 is (100μm-20mm) x (100μm-20mm), and the size of a single pixel is (0.1μm-3μm) x (0.1μm-3μm).

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