Microlens array for light field microscope and light field microscope

Abstract

The invention provides a microlens array for a light field microscope and the light field microscope. A microlens array for a light field microscope is located on a rear pupil plane of an objective lens, each microlens of the microlens array having optimization parameters independently designed based on respective incident light characteristics for correcting aberrations and chromatic aberrations.

Description

Technical Field

[0001] The present invention relates to the field of optical imaging, and in particular to a microlens array for a light field microscope and a light field microscope. Background Art

[0002] The nervous system is composed of a large number of neurons with diverse morphologies and functions, and complex connections between them. When studying complex behaviors, recording the activity of a few neurons is often insufficient to fully understand the connection between neural network activity and the animal's behavioral state. Therefore, simultaneously recording the activity of large groups of neurons can provide a better understanding of brain function. However, traditional optical imaging techniques are often limited in imaging throughput, with low instantaneous imaging throughput, making it difficult to simultaneously achieve the goals of high-speed imaging and large-scale imaging, and unable to simultaneously record the activity of large groups of neurons.

[0003] Light-field microscopy boasts highly parallelized imaging capabilities, enabling rapid volumetric imaging by simultaneously capturing light signals at different depths with a single camera exposure. For example, it can record neural activity throughout the brain of freely swimming zebrafish larvae and rapid blood flow dynamics within the mouse brain. Therefore, light-field microscopy, with its rapid 3D volumetric imaging capabilities, has had a significant impact on neuroscience research.

[0004] like Figure 1A As shown, in a conventional light field microscope, the camera 111 is located at the focal plane of the microlens array 110. In this way, what the camera 111 records is an array combination of the back pupil (Back Pupil) image formed by each microlens of the microlens array 110. The brightness of each pixel of the camera 111 represents the superposition of the light passing through the corresponding microlens and the point. After imaging, all the light in the light field is superimposed together according to the position and angle of the light to reconstruct the original three-dimensional volume. Therefore, the conventional light field microscope can capture the position and direction information of all the light rays that make up the entire light field, and then reconstruct the entire three-dimensional image of the sample through an algorithm.

[0005] like Figure 1B As shown, in a Fourier light field microscope, a microlens array 120 is located at the back pupil plane of an objective lens 121, and a camera 122 is located at the focal plane of the microlens array 120. Each microlens in the microlens array 120 collects light from a specific viewing angle of the sample and forms an image of this light on the camera 122. The sub-image formed by each microlens on the camera 122 represents a projection view of a three-dimensional volume from different angles. Using algorithms related to projection tomography, the three-dimensional volume can be reconstructed from these projection views.

[0006] In the prior art, each microlens in a microlens array is a plano-convex lens with the same radius of curvature. However, the degree of freedom of the plano-convex lens is limited, and various aberrations cannot be corrected by simply changing the curvature of the spherical surface of each microlens.

[0007] In addition, if Figure 1B As shown, existing light field microscopes usually use commercial objective lenses. The back pupil plane of the objective lens 121 is generally located inside the objective lens 121. A set of relay lenses is required to conjugate the back pupil plane of the objective lens 121 to the outer area of the objective lens 121 to leave enough space for the microlens array 120. As a result, the optical path of the entire Fourier light field microscope is relatively large, and miniaturization of the light field microscope cannot be achieved.

[0008] In addition, existing light field microscopes cannot perform imaging with a large field of view while ensuring high resolution. Better resolution often requires an objective lens with a high numerical aperture, and the field of view of an objective lens with a high numerical aperture is often smaller. If the field of view is to be expanded under high numerical aperture, a very complex lens group (usually requiring the participation of a dozen or more lenses) is required in the objective lens to correct the aberrations at the edge of the field of view after the field of view is expanded. Existing commercial objective lenses, such as Nikon's 16× objective lens, have a theoretical maximum field of view diameter of only 1.3mm when the numerical aperture is 0.8. Therefore, the numerical aperture and the size of the field of view are mutually constrained.

[0009] In order to overcome the above-mentioned defects of the existing technology, the field urgently needs a microlens array for light field microscopy and a light field microscope, which can independently optimize each microlens of the microlens array to correct various types of aberrations, miniaturize the light field microscope, and at the same time achieve a large field of view and high resolution of the light field microscope. Summary of the Invention

[0010] The following is a brief summary of one or more aspects to provide a basic understanding of these aspects. This summary is not an exhaustive overview of all conceivable aspects and is neither intended to identify key or critical elements of all aspects nor to define the scope of any or all aspects. Its sole purpose is to present some concepts of one or more aspects in a simplified form as a prelude to the more detailed description that will be provided later.

[0011] In order to overcome the above-mentioned defects of the prior art, the present invention provides a microlens array for a light field microscope and a light field microscope, which can independently optimize each microlens of the microlens array to correct various types of aberrations, thereby miniaturizing the light field microscope while also achieving a large field of view and high resolution.

[0012] Specifically, according to the first aspect of the present invention, the microlens array for light field microscopy is provided, wherein the microlens array is located on the rear pupil plane of the objective lens, and each microlens of the microlens array has optimized parameters independently designed based on the characteristics of the respective incident light, so as to correct aberrations and chromatic aberrations.

[0013] Preferably, in an embodiment of the present invention, the incident light characteristics of each microlens are determined by ray tracing to independently design the optimization parameters of the plurality of microlenses.

[0014] Preferably, in an embodiment of the present invention, the incident light characteristics include the angle and wavelength of the incident light.

[0015] Preferably, in an embodiment of the present invention, the optimization parameters of the plurality of microlenses include radial distance, microlens thickness, microlens diameter, microlens material, microlens combination, clear aperture, spherical type and / or curvature radius.

[0016] Preferably, in one embodiment of the present invention, the plurality of microlenses are divided into inner ring microlenses, sub-outer ring microlenses and outer ring microlenses based on radial distance, wherein the plurality of microlenses include a first surface and a second surface, the first surface faces the objective lens, the first surface of the inner ring microlens is a plane and the second surface is a spherical surface, and the first surfaces of the sub-outer ring microlenses and the outer ring microlenses are cylindrical surfaces and the second surfaces are spherical surfaces.

[0017] Preferably, in one embodiment of the present invention, the first surfaces of the sub-outer ring microlenses and the outer ring microlenses are concave cylindrical surfaces, and the second surfaces are concave spherical surfaces, and the cylindrical directions of the concave cylindrical surfaces are parallel to the radial directions of the microlenses in the microlens array.

[0018] In addition, the light field microscope provided according to the second aspect of the present invention includes an objective lens and a microlens array for a light field microscope provided in any one of the above embodiments.

[0019] Preferably, in an embodiment of the present invention, the objective lens includes two lenses.

[0020] Preferably, in one embodiment of the present invention, the objective lens includes a plano-convex lens and a doublet lens.

[0021] Preferably, in an embodiment of the present invention, the microlens array is located inside the lens barrel of the objective lens. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The above features and advantages of the present invention will be better understood after reading the detailed description of the embodiments of the present disclosure in conjunction with the following drawings. In the drawings, the components are not necessarily drawn to scale, and components with similar related properties or characteristics may have the same or similar reference numerals.

[0023] Figure 1A The figure shows a schematic diagram of the optical path of a light field microscope in the prior art;

[0024] Figure 1B The figure shows a light path schematic diagram of a Fourier light field microscope in the prior art;

[0025] Figure 2 shows a schematic diagram of a microlens array provided according to some embodiments of the present invention;

[0026] Figure 3 shows a schematic diagram of a light field microscope provided according to some embodiments of the present invention;

[0027] Figure 4 A schematic diagram of the optical path of a light field microscope provided according to some embodiments of the present invention is shown;

[0028] Figure 5 shows a schematic diagram of an objective lens barrel provided according to some embodiments of the present invention;

[0029] Figure 6 A schematic diagram showing a microlens provided according to some embodiments of the present invention; and

[0030] Figures 7A-7B A comparison diagram before and after aberration correction according to some embodiments of the present invention is shown.

[0031] Reference numerals:

[0032] 110, 120, 200: microlens array;

[0033] 111, 122: Camera;

[0034] 121: objective lens;

[0035] 300: Light field microscope;

[0036] 310: Plano-convex lens;

[0037] 320: Doublet lens;

[0038] 410: posterior pupillary plane;

[0039] 610: Page 1;

[0040] 620: Side 2; and

[0041] A: Radial direction. DETAILED DESCRIPTION

[0042] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. Note that the various aspects described below with reference to the accompanying drawings and specific embodiments are merely exemplary and should not be construed as limiting the scope of protection of the present invention.

[0043] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed, detachable, or integral connections; mechanical or electrical connections; direct or indirect connections through an intermediate medium; and internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances.

[0044] Furthermore, the terms "upper," "lower," "left," "right," "top," "bottom," "horizontal," and "vertical" used in the following description should be understood to refer to the orientations depicted in that section and the accompanying drawings. These relative terms are used solely for convenience of description and do not necessarily imply that the devices described herein must be manufactured or operated in a specific orientation. Therefore, they should not be construed as limiting the present invention.

[0045] It will be understood that although the terms "first," "second," "third," etc. may be used herein to describe various components, regions, layers, and / or portions, these components, regions, layers, and / or portions should not be limited by these terms, and these terms are merely used to distinguish different components, regions, layers, and / or portions. Thus, a first component, region, layer, and / or portion discussed below may be referred to as a second component, region, layer, and / or portion without departing from some embodiments of the present invention.

[0046] As described above, in the prior art, each microlens in a microlens array adopts a plano-convex lens with the same curvature radius. However, the plano-convex lens has limited degrees of freedom and cannot correct various aberrations by simply changing the curvature of the spherical surface of each microlens.

[0047] In addition, if Figure 1B As shown, existing light field microscopes usually use commercial objective lenses. The back pupil plane of the objective lens 121 is generally located inside the objective lens 121. A set of relay lenses is required to conjugate the back pupil plane of the objective lens 121 to the outer area of the objective lens 121 to leave enough space for the microlens array 120. As a result, the optical path of the entire Fourier light field microscope is relatively large, and miniaturization of the light field microscope cannot be achieved.

[0048] Furthermore, existing light-field microscopes are unable to image a large field of view while ensuring high resolution. Better resolution often requires a high numerical aperture objective lens, and high numerical aperture objectives often have a smaller field of view. If the field of view is to be expanded at a high numerical aperture, a very complex lens group is required in the objective lens to correct the aberrations at the edge of the field of view after the field of view is expanded. Existing commercial objective lenses, such as Nikon's 16× objective lens, have a theoretical maximum field of view diameter of only 1.3 mm at a numerical aperture of 0.8. Therefore, the numerical aperture and the size of the field of view are mutually constrained.

[0049] In order to overcome the above-mentioned defects of the prior art, the present invention provides a microlens array for a light field microscope and a light field microscope, which can independently optimize each microlens of the microlens array to correct various types of aberrations, thereby miniaturizing the light field microscope while also achieving a large field of view and high resolution.

[0050] Please refer to Figure 2 and Figure 3 , Figure 2 shows a schematic diagram of a microlens array provided according to some embodiments of the present invention, Figure 3 A schematic diagram of a light field microscope provided according to some embodiments of the present invention is shown.

[0051] like Figure 2 As shown, in a non-limiting embodiment, the microlens array 200 can be composed of three circles of microlenses, each circle of microlenses having different aberration characteristics. Different parameters can be selected for each microlens to correct aberrations and chromatic aberrations. Specifically, optimized parameters for each microlens in the microlens array for correcting aberrations and chromatic aberrations can be independently designed based on the incident light characteristics of each microlens. Preferably, the incident light characteristics can include the angle and wavelength of the incident light.

[0052] like Figure 3 As shown, the light field microscope 300 may include an objective lens and Figure 2 As shown, the microlens array 200 can be arranged on the back pupil plane of the objective lens.

[0053] The objective lens can be used to control the anisotropy of light. Here, the objective lens can be a lens combination consisting of two lenses.

[0054] exist Figure 3 In the illustrated embodiment, the objective lens may be a lens combination of a plano-convex lens 310 and a doublet lens 320 .

[0055] Specifically, plano-convex lens 310 can be a single lens L1, and doublet lens 320 can be achromatic doublet lenses L2 & 3. Based on the required field of view, numerical aperture, and magnification of light-field microscope 300, the curvature radius, center thickness, material, and diameter parameters of each lens of the objective lens can be determined. The distances between each lens of the objective lens and between the objective lens and microlens array 200 can also be determined.

[0056] As shown in Table 1, the radius of curvature of the first surface of single lens L1 can be ∞, the radius of curvature of the second surface can be 12.0 mm, the center thickness is 10 mm, the selected material is BK7, and the diameter of single lens L1 is 16 mm. In the achromatic doublets L2 and 3, the radius of curvature of L2 on the first surface can be 100.0 mm, the radius of curvature of the second surface can be -22.0 mm, the center thickness is 3 mm, the selected material is SF6HT, and the diameter is 25 mm. In the achromatic doublets L2 and 3, the radius of curvature of L3 on the first surface can correspond to L2, being 22.0 mm, the radius of curvature of the second surface can be 20.5 mm, the center thickness is 10 mm, the selected material is BAF10, and its diameter is the same as L2, being 25 mm.

[0057]

[0058]

[0059] Table 1

[0060] Please refer to Figure 4 , Figure 4 A schematic diagram of the optical path of a light field microscope provided according to some embodiments of the present invention is shown.

[0061] By using the single lens L1 and the achromatic doublet lenses L2 & 3 shown in Table 1, the field of view can be expanded and the anisotropy of light can be effectively controlled. Figure 4 As shown in the figure, according to the optical simulation results, point light sources at different object-side fields of view are refracted by the single lens L1 and the achromatic doublet lenses L2 & 3, forming nearly parallel beams of the same diameter behind the achromatic doublet lenses L2 & 3, thus forming the back pupil plane 410 of the objective lens. Preferably, the microlens array 200 can be placed 8 mm behind the achromatic doublet lenses L2 & 3, i.e., at the back pupil plane 410 of the objective lens, thereby forming an integrated light-field microscope 300.

[0062] Please refer to Figure 5 , Figure 5 Schematic diagrams of objective lens barrels provided according to some embodiments of the present invention are shown.

[0063] like Figure 5As shown, the light field microscope 300 can position the back pupil plane close to the objective lens and design the back pupil plane inside the lens barrel of the objective lens, thereby providing sufficient space inside the lens barrel to place the microlens array. By placing the microlens array inside the lens barrel of the objective lens, the light field microscope 300 not only achieves imaging, but also simplifies the overall optical path of the light field microscope 300, reduces the size of the light field microscope 300, and realizes the integration of the light field microscope 300.

[0064] Furthermore, if Figure 3 As shown, in a light field microscope 300, a microlens array 200 is placed behind the objective lens, and each microlens in the microlens array 200 can collect light from a specific angle of the sample. Since the equivalent numerical aperture of the microlens is very small (less than 0.1), each microlens receives only a small portion of the light on the rear pupil plane, and the angle covered by this portion of light is limited. In addition, at the microlens array 200, aberrations and chromatic aberrations are introduced due to the expansion of the field of view. Therefore, the aberrations and chromatic aberrations can be independently optimized based on the incident light at a specific angle received by each microlens, thereby simplifying the optical system of the light field microscope and correcting the aberrations and chromatic aberrations through each single lens in the microlens array.

[0065] Theoretical analysis and simulation results show that Figure 3 In the embodiment shown, the aberration and chromatic aberration characteristics of the sample light at different angles collected by each microlens in the microlens array 200 vary greatly. If the microlens array 200 is set with uniform parameters, it will not be able to take into account the correction of various aberrations and chromatic aberrations.

[0066] Specifically, high-precision ray tracing can be used to determine the characteristics of the incident light on each microlens, such as the incident light angle, so that the optimized parameters of multiple microlenses can be independently designed. This maximizes the correction effect of aberration and chromatic aberration of the entire microlens array 200, further meeting the requirements of clear imaging under a large field of view. Here, high-precision ray tracing can be achieved using optical simulation software, such as Zemax software.

[0067] Please continue to refer to Figure 2 In the optical system of the light field microscope 300 , the microlens array 200 may be provided with one inner ring microlens, seven sub-outer ring microlenses, and fourteen outer ring microlenses.

[0068] As shown in Table 2, the optimized parameters of the multiple microlenses in the microlens array 200 may include radial distance, microlens thickness, microlens diameter, microlens material, microlens combination, clear aperture, spherical surface type, and curvature radius. The radial distance of the sub-outer microlenses is defined as the distance from the center of the inner microlens to the center of the sub-outer microlens, while the radial distance of the outer microlenses is defined as the distance from the center of the inner microlens to the center of the outer microlens.

[0069] The material of the multiple micro lenses of the micro lens array 200 , that is, the micro lens material, can be BK7, the center thickness can be set to 7 mm, and the diameter can be 4 mm.

[0070] Please refer to Figure 6 , Figure 6 Schematic diagram of a microlens provided according to some embodiments of the present invention is shown.

[0071] like Figure 6 As shown, the plurality of microlenses of the microlens array 200 may include a first surface 610 and a second surface 620, wherein the first surface 610 is a surface facing the objective lens. Figure 3 In the illustrated embodiment, the first surface 610 is the surface of the microlens array 200 facing the doublet lens 320 .

[0072] Through optical simulation calculations, it is found that the aberration characteristics of the sub-outer ring microlenses and outer ring microlenses of the microlens array 200 contain astigmatism components. Relying solely on the spherical surface shape cannot effectively correct astigmatism. Therefore, the sub-outer ring microlenses and outer ring microlenses of the microlens array 200 also need to be set with a cylindrical surface shape. Here, the sub-outer ring microlenses and outer ring microlenses of the microlens array 200 can set the first surface as a cylindrical surface and the second surface as a spherical surface. Furthermore, the first surface of the sub-outer ring microlenses and outer ring microlenses can be a concave cylindrical surface, and the second surface can be a concave spherical surface, and, as Figure 2 As shown, the cylindrical direction of the concave cylindrical surface is parallel to the radial direction A of the microlens in the microlens array 200 .

[0073] Therefore, the radial distance of the inner microlens is 0 mm, the clear aperture can be 2.2 mm, the first surface of the inner microlens can be a plane with a radius of curvature of ∞, and the second surface can be a concave spherical surface with a radius of curvature of -14.25. The radial distance of the sub-outer microlens can be 5.6 mm, the clear aperture can be 2.0 mm, the first surface of the sub-outer microlens can be a concave cylindrical surface with a radius of curvature of -456.0, and the second surface can be a concave spherical surface with a radius of curvature of -14.50. The radial distance of the outer microlens can be 9.9 mm, the clear aperture can be 1.8 mm, the first surface of the outer microlens can be a concave cylindrical surface with a radius of curvature of -142.0, and the second surface can be a concave spherical surface with a radius of curvature of -1500.

[0074]

[0075] Table 2

[0076] Please refer to Figures 7A-7B , Figures 7A-7B A schematic diagram showing comparisons before and after aberration correction according to some embodiments of the present invention is shown.

[0077] Taking the outer ring microlens as an example, the point spread function of the outer ring microlens with only spherical surface is as follows Figure 7A As shown in , the point spread function shows that the aberration characteristics of the outer ring microlens contain astigmatism. Figure 7B As shown, the outer ring microlens is a microlens with a surface type that combines a concave cylindrical surface and a concave spherical surface, thereby achieving an ideal correction effect.

[0078] By constructing optical models and performing optical computational simulations on these constructed optical models, compared to existing technologies (for example, a field of view of 1.3 mm and a numerical aperture of 0.8), the light field microscope 300 can provide ideal aberration and chromatic aberration correction effects within a field of view of 3 mm by independently designing and optimizing parameters for each microlens in the microlens array 200, thereby simultaneously meeting the requirements of a large field of view (3 mm) and a high numerical aperture (0.7) of the light field microscope 300, and achieving miniaturization of the light field microscope 300 with a large field of view.

[0079] In summary, the microlens array and light-field microscope provided by the present invention for light-field microscopy substantially simplify the optical system of the light-field microscope, greatly reducing the volume of the imaging system and the cost of the optical components required to construct the optical system. By using a microlens array with independently designed optimized parameters, personalized optimization is performed based on the characteristics of different incident light rays, thereby achieving aberration and chromatic aberration correction over a large field of view, providing a solution for correcting aberration and chromatic aberration over a large field of view. By designing the microlenses of the microlens array with multiple parameters and multiple degrees of freedom, the application prospects of this solution in large-field-of-view imaging technology can be expanded.

[0080] The microlens array for light field microscopy and the light field microscope provided by the present invention can be applied to the observation of various rapid dynamic changes in living animals. For example, the whole brain of zebrafish within 2 weeks after birth can be imaged in vivo, and all labeled neurons within a range of 3*3mm in the mouse cortex can be imaged in vivo. Taking the imaging of blood vessels in the mouse head as an example, the light field microscope provided by the present invention can record blood flow signals in the entire three-dimensional field of view within a range of 3 mm in diameter and 400 microns in thickness in the mouse cerebral cortex at a speed of 200 Hz. In addition, the microlens array for light field microscopy and the light field microscope provided by the present invention can be applied to, including but not limited to, whole-brain imaging of freely behaving living zebrafish, imaging of neurons in living mice, etc., and can also be applied to high-speed imaging scenarios in all transparent or translucent biological tissues in the field of biological imaging.

[0081] The previous description of the disclosure is provided to enable any person skilled in the art to make or use the disclosure. Various modifications to the disclosure will be apparent to those skilled in the art, and the general principles defined herein may be applied to other variations without departing from the spirit or scope of the disclosure. Thus, the disclosure is not intended to be limited to the examples and designs described herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A microlens array for light field microscopy, characterized in that: The microlens array is located on the rear pupil plane of the objective lens. Each microlens of the microlens array has optimized parameters independently designed based on respective incident light characteristics, so as to correct aberration and chromatic aberration.

2. The microlens array according to claim 1, wherein: The incident light characteristics of each microlens are determined by ray tracing to independently design the optimized parameters of the plurality of microlenses.

3. The microlens array according to claim 1, wherein: The incident light characteristics include the angle and wavelength of the incident light.

4. The microlens array according to claim 1, wherein: The optimized parameters of the plurality of microlenses include radial distance, microlens thickness, microlens diameter, microlens material, microlens combination, clear aperture, spherical surface type and / or curvature radius.

5. The microlens array according to claim 1, wherein: The multiple microlenses are divided into inner ring microlenses, sub-outer ring microlenses and outer ring microlenses based on radial distance, wherein the multiple microlenses include a first surface and a second surface, the first surface faces the objective lens, the first surface of the inner ring microlens is a plane and the second surface is a spherical surface, the first surface of the sub-outer ring microlens and the outer ring microlens are cylindrical surfaces and the second surface is a spherical surface.

6. The microlens array according to claim 5, wherein: The first surfaces of the sub-outer ring microlenses and the outer ring microlenses are concave cylindrical surfaces, and the second surfaces are concave spherical surfaces. The cylindrical directions of the concave cylindrical surfaces are parallel to the radial directions of the microlenses in the microlens array.

7. A light field microscope, characterized in that The invention comprises an objective lens and a microlens array for a light field microscope as claimed in any one of claims 1 to 6.

8. The light field microscope according to claim 7, wherein The objective lens includes two lenses.

9. The light field microscope according to claim 8, wherein The objective lens includes a plano-convex lens and a doublet lens.

10. The light field microscope according to claim 7, wherein The microlens array is located inside the lens barrel of the objective lens.

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