An optical field imaging apparatus and method

Abstract

The application relates to the technical field of imaging devices, and particularly discloses a light field imaging device and method, which comprises a main lens configured to receive light rays in a scene and refract to form a first image; a diffraction element arranged on the side of the main lens away from the scene, the diffraction element is arranged in an array and has a plurality of diffraction elements, the diffraction element is configured to perform isofocal diffraction focusing on monochromatic light of a target wavelength in the first image to form focused light rays; a light filtering element arranged on the side of the diffraction element away from the main lens, the light filtering element is configured to receive the focused light rays and allow the monochromatic light to pass through the light filtering element; and an image sensor arranged on the side of the light filtering element away from the diffraction element, the image sensor is configured to receive the monochromatic light passing through the light filtering element to form an element image. The light field imaging device and method can effectively eliminate imaging chromatic aberration and reduce the cost.

Description

Technical Field

[0001] The present invention relates to the technical field of imaging devices, and in particular to a light field imaging device and method. Background Art

[0002] In order to eliminate the chromatic aberration of the light field imaging system based on diffractive optical elements, the following two aspects are taken into consideration: (1) Designing a single achromatic diffraction lens: For example, using aluminum, silver, and gold micro-nanoparticles embedded in silicon dioxide sheets to design a single-layer metasurface with the same focusing power for wavelengths of 30-600nm, 550nm, and 650nm, these metasurfaces are then arranged in coaxial concentric rings in the structure of Fresnel zone plates to achieve achromatic aberration of a single diffraction lens. The achromatic diffraction lens is arrayed to build a light field imaging system; (2) Post-correction of chromatic aberration images is performed based on algorithms. Currently, the design and manufacture of achromatic diffraction lenses are very difficult (especially for centimeter-level aperture devices required for some imaging systems), the cost is very high, and the scope of application is limited. Image restoration methods based on deep learning and other methods are limited by the generalization and computational complexity of the algorithm and cannot obtain completely achromatic images. Therefore, the technical solution of this application is urgently needed to solve the above problems. Summary of the Invention

[0003] The object of the present invention is to provide a light field imaging device that can effectively eliminate imaging chromatic aberration and reduce costs.

[0004] In order to achieve the above objectives, the present invention provides a light field imaging device, comprising:

[0005] a primary lens configured to receive light from a scene and refract it to form a primary image;

[0006] a diffraction element disposed on a side of the main lens facing away from the scene, wherein a plurality of the diffraction elements are provided and distributed in an array, and configured to perform diffraction focusing with equal focal length on the monochromatic light of the target wavelength in the first imaging to form focused light;

[0007] a filter element disposed on a side of the diffraction element away from the main lens, the filter element being configured to receive the focused light and allow the monochromatic light to pass through the filter element; and

[0008] The image sensor is arranged on a side of the filter element away from the diffraction element, and is configured to receive the monochromatic light passing through the filter element for a second imaging and form an element image.

[0009] In some embodiments, the first imaging is located in front of the front focal plane of the diffraction element.

[0010] In some embodiments, the diffraction element is one of a Fresnel lens, a Pancharatnam-Berry (PB) phase liquid crystal lens, and a meta-lens.

[0011] In some embodiments, the diffraction element has three types, which are respectively denoted as the first diffraction element, the second diffraction element and the third diffraction element. The focal lengths of the red, green and blue light corresponding to the first diffraction element are respectively denoted as f 1R 、f 1G and f 1B , the focal lengths of the red, green and blue lights corresponding to the second diffraction element are expressed as f 2R 、f 2G and f 2B , the focal lengths of the red, green and blue lights corresponding to the third diffraction element are expressed as f 3R 、f 3G and f 3B , then the relationship is satisfied: f=f 1R =f 2G =f 3B .

[0012] In some embodiments, the first diffraction element, the second diffraction element and the third diffraction element are horizontally arranged in sequence along a longitudinal straight line.

[0013] In some embodiments, the first diffraction element, the second diffraction element and the third diffraction element are horizontally arranged in sequence along a transverse straight line.

[0014] In some embodiments, the first diffraction element, the second diffraction element and the third diffraction element are horizontally arranged in sequence along straight lines inclined at 30-60 degrees.

[0015] In some embodiments, the filter element is a narrow-band filter, a plurality of narrow-band filters are provided, and the narrow-band filters are arranged in a one-to-one correspondence with the diffraction elements.

[0016] In some embodiments, the image sensor is a two-dimensional image sensor.

[0017] In another aspect, the present invention provides a light field imaging method, comprising:

[0018] The primary lens receives light from the scene, and the primary lens refracts the light to form a primary image;

[0019] The light formed by the first imaging is received by a plurality of diffraction elements distributed in an array, and a single diffraction element performs diffraction and focusing of the monochromatic light of the target wavelength at an equal focal length to form a focused light;

[0020] receiving the focused light through a filter element, and allowing the monochromatic light to pass through the filter element;

[0021] The monochromatic light transmitted through the filter element is received by an image sensor, and a second imaging is performed on the image sensor to form an element image.

[0022] The present invention provides a light field imaging device and method, which have the following advantages compared with the prior art:

[0023] The diffraction element is arranged on the side of the main lens away from the scene. The diffraction element is provided in plurality and distributed in an array. The diffraction element is configured to perform diffraction focusing with equal focal length on the monochromatic light of the target wavelength in the first imaging to form focused light. The filter element is configured to receive the focused light and allow the monochromatic light to pass through the filter element. The image sensor is configured to receive the monochromatic light passing through the filter element for a second imaging and form an elemental image. The image finally formed can eliminate chromatic aberration, and there is no need to configure an achromatic diffraction lens, which can reduce costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 A schematic diagram of the principle of a light field imaging device provided in some embodiments of the present invention.

[0025] Figure 2 A schematic diagram of the imaging principle of a light field imaging device provided by some embodiments of the present invention, in which the diffraction elements are arranged horizontally along a longitudinal straight line.

[0026] Figure 3 A schematic diagram of the imaging principle of a light field imaging device provided by some embodiments of the present invention, in which the diffraction elements are horizontally arranged along a horizontal straight line.

[0027] Figure 4 Schematic diagram of the imaging principle of a light field imaging device provided by some embodiments of the present invention, in which the diffraction elements are arranged horizontally along an inclined straight line

[0028] Figure 5 A flowchart of a light field imaging method provided in some other embodiments of the present invention.

[0029] In the figure: 1. Main lens; 2. Diffraction element; 3. Filter element; 4. Image sensor; 5. Scene; 6. First imaging. DETAILED DESCRIPTION

[0030] The technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments.

[0031] It should be understood that in the description of this application, the terms "upper", "lower", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on this application. The terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated, that is, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In addition, unless otherwise specified, "multiple" means two or more.

[0032] In addition, the technical features involved in the different embodiments of the present application described below can be combined with each other as long as they do not conflict with each other.

[0033] like Figure 1-5 As shown, some embodiments of the present invention provide a light field imaging device, comprising a main lens 1, a diffraction element 2, a filter element 3, and an image sensor 4. Light in a scene is refracted by the main lens 1 to form a primary image. After being diffracted by the diffraction element 2 and filtered by the filter element 3, a secondary image is formed on the image sensor 4, forming an elemental image with chromatic aberration eliminated.

[0034] The main lens 1 is configured to receive light from a scene 5 and refract it to form a primary image 6. Specifically, the main lens is an existing common imaging convex lens.

[0035] The diffraction element 2 is provided on the side of the main lens 1 facing away from the scene 5. There are multiple diffraction elements 2 and they are distributed in an array. The diffraction element 2 is configured to perform diffraction focusing of the monochromatic light of the target wavelength in the first imaging 6 with equal focal length to form focused light. In addition, light of wavelengths other than the target wavelength also has a diffraction focusing effect, but the focal length does not need to be specifically set, and can serve as a source of chromatic aberration. To achieve three-dimensional image reconstruction, the position of the resulting element image can be found on the image sensor 4 according to the projection relationship of the main light passing through the center of each diffraction element 2 through similar triangles, which is recorded as (x, y). Therefore, each corresponding recorded element image has a certain parallax relationship with the element image imaged by other diffraction elements 2. All element images with certain parallax are arranged in an array on the image sensor 4 in a certain pattern, and the image array formed is called an element image array. In light field imaging, the large number of parallax relationships recorded in the element image array contains the spatial information of the three-dimensional object. The translation amount (Δx) required for each element image to overlap and combine can be obtained by inferring the imaging light path propagation process of the array-distributed diffraction elements 2 through the parallax relationship on the plane of the image sensor 4. i ,Δyj ), the post-processing algorithm is used to add the corresponding translation amount to the element image to complete the three-dimensional image reconstruction with spatial information.

[0036] Filter element 3 is disposed on the side of diffraction element 2 facing away from main lens 1. Filter element 3 is configured to receive focused light and allow monochromatic light to pass through filter element 3. In the same plane, the diffraction elements 2 are arranged from left to right in the order of the first diffraction element, the second diffraction element, and the third diffraction element. At a predetermined position on the image sensor 4 plane, the R channel elemental image of the first diffraction element, the G channel elemental image of the second diffraction element, and the B channel elemental image of the third diffraction element are not defocused. However, without filtering, the image sensor will still record the G and B channel elemental images of the first diffraction element, the R and B channel elemental images of the second diffraction element, and the R and G channel elemental images of the third diffraction element with different defocus information. By adding a wavelength selection device between the diffraction lens array and the image sensor to only screen the R channel element image of the first diffraction element, the G channel element image of the second diffraction element, and the B channel element image of the third diffraction element, an element image array consisting of single-channel element images without defocus information can be obtained. For this purpose, the design of the wavelength selection device also needs to be arranged periodically, and the arrangement of the selected wavelengths corresponds to the R wavelength of the first diffraction element, the G wavelength of the second diffraction element, and the B wavelength of the third diffraction element in sequence.

[0037] Image sensor 4 is located on the side of filter element 3 facing away from diffractive element 2. Image sensor 4 is configured to receive monochromatic light transmitted through filter element 3 for secondary imaging, forming an elemental image. During installation, the position of image sensor 4 needs to be determined based on the imaging relationship of diffractive element 2 and the primary imaging position of main lens 1.

[0038] Based on the above structural setting, image chromatic aberration can be eliminated, and there is no need to configure an achromatic diffraction lens, which can reduce costs.

[0039] In some embodiments, the first imaging is located in front of the front focal plane of the diffraction element 2. This facilitates diffraction transmission imaging by the diffraction element 2. Specifically, the distance between the first imaging position and the diffraction element 2 (i.e., the imaging object distance) is greater than the focal length of the diffraction element 2 (real image type).

[0040] In some embodiments, the diffraction element 2 is one of a Fresnel lens, a PB phase liquid crystal lens, and a meta-lens.

[0041] In some embodiments, the diffraction element 2 has three types divided according to the focal length, which are respectively denoted as the first diffraction element, the second diffraction element and the third diffraction element. The focal lengths of the red, green and blue light corresponding to the first diffraction element are respectively denoted as f 1R 、f 1G and f1B The focal lengths of the red, green, and blue lights corresponding to the second diffraction element are expressed as f 2R 、f 2G and f 2B The focal lengths of the red, green and blue lights corresponding to the third diffraction element are expressed as f 3R 、f 3G and f 3B , then the relationship is satisfied: f=f 1R =f 2G =f 3B This ensures that image information of one color channel, R, G, and B, under each diffraction element 2 is recorded on the two-dimensional image array without defocusing.

[0042] like Figure 2 As shown, in some embodiments, the first diffraction element, the second diffraction element and the third diffraction element are horizontally arranged in sequence along a longitudinal straight line to achieve the function of eliminating chromatic aberration along the horizontal and longitudinal directions.

[0043] like Figure 3 As shown, in some embodiments, the first diffraction element, the second diffraction element and the third diffraction element are respectively and sequentially arranged horizontally along a horizontal straight line to achieve the function of eliminating chromatic aberration along the horizontal direction.

[0044] like Figure 4 As shown, in some embodiments, the first, second, and third diffraction elements are sequentially arranged horizontally along straight lines inclined at 30-60 degrees. Compared to the above two arrangements, this embodiment provides the first, second, and third diffraction elements with an additional degree of freedom for controlling the color channels of the elemental image in one direction. This increases the upper limit of the achromatic aberration capability in the post-processing elemental image synthesis algorithm, enhances the robustness of the achromatic light field imaging system, and achieves better chromatic aberration elimination.

[0045] In some embodiments, the filter element 3 is a narrowband filter, and a plurality of narrowband filters are provided, each narrowband filter being arranged in a one-to-one correspondence with a diffraction element. The narrowband filter is used to allow monochromatic light to pass through.

[0046] In some embodiments, the image sensor 4 is a two-dimensional image sensor, and illustratively, a CCD sensor is used.

[0047] like Figure 5 As shown, some other embodiments of the present invention provide light field imaging methods, including the following steps:

[0048] S1: The main lens receives light from the scene and refracts the light to form the first image.

[0049] S2. Receive the light formed by the first imaging through multiple diffraction elements distributed in an array, and a single diffraction element performs diffraction and focusing of the monochromatic light of the target wavelength at equal focal length to form a focused light;

[0050] S3, receiving the focused light through the filter element, and allowing the monochromatic light to pass through the filter element;

[0051] S4. The monochromatic light transmitted through the filter element is received by the image sensor, and a second imaging is performed on the image sensor to form an element image.

[0052] Based on the above method, the obtained image can eliminate chromatic aberration and reduce usage costs.

[0053] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and substitutions can be made without departing from the technical principles of the present invention. These improvements and substitutions should also be regarded as the scope of protection of the present invention.

Claims

1. A light field imaging device, characterized in that: include: a primary lens configured to receive light from a scene and refract it to form a primary image; a diffraction element disposed on a side of the main lens facing away from the scene, wherein a plurality of the diffraction elements are provided and distributed in an array, and configured to perform diffraction focusing with equal focal length on the monochromatic light of the target wavelength in the first imaging to form focused light; a filter element, disposed on a side of the diffraction element away from the main lens, the filter element being configured to receive the focused light and allow the monochromatic light to pass through the filter element; and an image sensor, disposed on a side of the filter element facing away from the diffraction element, the image sensor being configured to receive the monochromatic light passing through the filter element for a second imaging and form an elemental image; There are three types of diffraction elements, which are respectively denoted as the first diffraction element, the second diffraction element and the third diffraction element. The focal lengths of the red, green and blue light corresponding to the first diffraction element are respectively denoted as f 1R 、f 1G and f 1B , the focal lengths of the red, green and blue lights corresponding to the second diffraction element are expressed as f 2R 、f 2G and f 2B , the focal lengths of the red, green and blue lights corresponding to the third diffraction element are expressed as f 3R 、f 3G and f 3B , then the relationship is satisfied: f=f 1R =f 2G =f 3B .

2. The light field imaging device according to claim 1, wherein: The first imaging is located in front of the front focal plane of the diffraction element.

3. The light field imaging device according to claim 1, wherein: The diffraction element is one of a Fresnel lens, a PB phase liquid crystal lens and a meta-lens.

4. The light field imaging device according to claim 1, wherein: The first diffraction element, the second diffraction element and the third diffraction element are horizontally arranged in sequence along a longitudinal straight line.

5. The light field imaging device according to claim 1, wherein: The first diffraction element, the second diffraction element and the third diffraction element are horizontally arranged in sequence along a transverse straight line.

6. The light field imaging device according to claim 1, wherein: The first diffraction element, the second diffraction element and the third diffraction element are horizontally arranged in sequence along straight lines inclined at 30-60 degrees.

7. The light field imaging device according to claim 1, wherein: The filter element is a narrow-band filter, a plurality of narrow-band filters are provided, and the narrow-band filters are arranged in a one-to-one correspondence with the diffraction elements.

8. The light field imaging device according to claim 1, wherein: The image sensor is a two-dimensional image sensor.

9. A light field imaging method, characterized in that: include: The primary lens receives light from the scene, and the primary lens refracts the light to form a primary image; The light formed by the first imaging is received by a plurality of diffraction elements distributed in an array, and a single diffraction element performs diffraction and focusing of the monochromatic light of the target wavelength at an equal focal length to form a focused light; receiving the focused light through a filter element, and allowing the monochromatic light to pass through the filter element; receiving the monochromatic light transmitted through the filter element through an image sensor, performing a second imaging on the image sensor and forming an element image; There are three types of diffraction elements, which are respectively denoted as the first diffraction element, the second diffraction element and the third diffraction element. The focal lengths of the red, green and blue light corresponding to the first diffraction element are respectively denoted as f 1R 、f 1G and f 1B , the focal lengths of the red, green and blue lights corresponding to the second diffraction element are expressed as f 2R 、f 2G and f 2B , the focal lengths of the red, green and blue lights corresponding to the third diffraction element are expressed as f 3R 、f 3G and f 3B , then the relationship is satisfied: f=f 1R =f 2G =f 3B .

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