Visible light imaging method and apparatus

Abstract

The application discloses a visible light imaging method and device, and belongs to the field of optical imaging. The method is used for a visible light imaging lens, and the visible light imaging lens comprises a first lens and a second lens at a near image end. The method comprises the following steps: acquiring an initial imaging image output by the second lens; performing regional division on the initial imaging image to obtain a plurality of initial sub-images; for different initial sub-images and different imaging wavelengths of each initial sub-image, a restored sub-image is obtained by restoration according to different point spread functions respectively; and all the restored sub-images are spliced to obtain a restored imaging image. The imaging field of view is divided into a plurality of sub-fields of view, which correspond to each sub-image one by one, and different point spread functions are determined according to different imaging wavelengths under different sub-fields of view. The method does not need to increase optical components and optical materials for correcting aberration, can reduce the number, volume, weight and cost of optical system lenses, and improves the portability of the lens assembly.

Description

Technical Field

[0001] This invention relates to the field of optical imaging, and more particularly to a visible light imaging method and apparatus. Background Technology

[0002] In conventional lens design, complex optical structures (such as multi-element cemented lenses) and expensive optical materials are required to achieve good image quality. These combinations can completely correct aberrations across various wavelengths and ensure the lens has a good optical transfer function across all fields of view.

[0003] However, the complex optical structure results in lenses that are not only large and heavy after assembly, but also bring high hardware costs. Summary of the Invention

[0004] To address the above problems, the present invention provides a visible light imaging method and apparatus.

[0005] This invention provides a visible light imaging method for a visible light imaging lens. The method includes: acquiring an initial imaging image output by a second lens; dividing the initial imaging image into regions to obtain multiple initial sub-images; reconstructing complex atomic images based on different point spread functions for different initial sub-images and different imaging wavelengths of each initial sub-image; and stitching together all complex atomic images to obtain a restored imaging image. The imaging field of view is divided into multiple sub-fields of view, each corresponding to a sub-image, and the different point spread functions are determined based on different imaging wavelengths under different sub-fields of view.

[0006] In the visible light imaging method of the present invention, before acquiring the initial image output by the second lens, the method further includes: determining an error function based on the sagittal ray transverse aberration, the meridional ray transverse aberration, and the wavelength weight of each imaging wavelength; and determining the lens parameters by gradually adjusting the lens parameters and the weight of each wavelength until the error function converges. The lens parameters include the distance between the first and second lenses, the radius of curvature of the first lens, the radius of curvature of the second lens, and the image distance. The sagittal ray transverse aberration and the meridional ray transverse aberration are determined based on the lens parameters.

[0007] In the visible light imaging method of the present invention, the error function includes:

[0008]

[0009] Where λ represents the imaging wavelength, W λ Δx represents the wavelength weight, and Δy represents the transverse aberration of the sagittal ray and the transverse aberration of the meridional ray, respectively.

[0010] In the visible light imaging method of the present invention, for different initial sub-images and different imaging wavelengths of each initial sub-image, complex atomic images are obtained by restoring them according to different point spread functions, including: determining a target function based on the complex atomic image, the initial sub-image, and the different point spread functions according to a cross-prior algorithm; optimizing the target function to determine the complex atomic image.

[0011] In the visible light imaging method of the present invention, before obtaining the initial image output by the second lens, the method further includes: dividing the field of view of the visible light imaging lens into N×N sub-fields of view, where N is a positive integer greater than 1; for each sub-field of view and each imaging wavelength, determining the point spread function of each imaging wavelength under each sub-field of view based on ray tracing, thereby obtaining the different point spread functions.

[0012] In the visible light imaging method of the present invention, the wavelength weight located at the center of the wavelength range is greater than the wavelength weight located at the edge.

[0013] In the visible light imaging method of the present invention, the different wavelength weight values ​​also include the following constraints:

[0014] W λ = a(λ-b) 2 +c

[0015] Where λ represents the imaging wavelength, a is less than 0, c is greater than 0, and b is between the minimum and maximum imaging wavelengths.

[0016] The present invention also provides a visible light imaging lens, comprising: an optical component and a structural component for fixing the optical component; the optical component includes a first lens and a second lens at the near-image end; wherein, the lens parameters are determined according to the convergence of an error function, the error function being determined based on the sagittal ray transverse aberration, the meridional ray transverse aberration, and the wavelength weight of each imaging wavelength, the sagittal ray transverse aberration and the meridional ray transverse aberration being determined according to the lens parameters, the lens parameters including the distance between the first lens and the second lens, the radius of curvature of the first lens, the radius of curvature of the second lens, and the image distance.

[0017] In the visible light imaging lens of the present invention, the structural components include a lens spacer and a retaining ring for fixing the lens, and a lens barrel for carrying optical components.

[0018] The present invention also provides a visible light imaging device, including any of the above-mentioned visible light imaging lenses and a restoration component. The restoration component includes: an acquisition module for acquiring an initial imaging image output by a second lens; a splitting module for dividing the initial imaging image into regions to obtain multiple initial sub-images; a restoration module for restoring different initial sub-images and different imaging wavelengths of each initial sub-image according to different point spread functions to obtain complex atomic images; and a stitching module for stitching all complex atomic images to obtain a restored imaging image. The imaging field of view is divided into multiple sub-fields of view, each corresponding to a sub-image, and the different point spread functions are determined according to different imaging wavelengths under different sub-fields of view.

[0019] The visible light imaging method and apparatus of the present invention selectively perform aberration correction and optimization on specific bands for different sub-fields of view, which can correct aberration to the greatest extent and obtain a restored image consistent with a clear image. In addition to two lenses, no additional optical components and optical materials for aberration correction are required, thereby reducing the number of lenses, size and weight of the optical system, thereby reducing the cost of the optical system and improving the portability of the lens assembly. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a schematic flowchart of the visible light imaging method according to an embodiment of the present invention;

[0022] Figure 2 This is a two-dimensional diagram of the visible light imaging lens optical system according to an embodiment of the present invention;

[0023] Figure 3 It is a two-dimensional diagram of a standard imaging lens optical system;

[0024] Figure 4 This is the initial imaging image of an embodiment of the present invention;

[0025] Figure 5 This is a restored image from an embodiment of the present invention;

[0026] Figure 6 It is a simulated image from a standard imaging lens;

[0027] Figure 7a This is a schematic diagram of the 0.486µm point spread function in an embodiment of the present invention;

[0028] Figure 7b This is a schematic diagram of the 0.546µm point spread function in an embodiment of the present invention;

[0029] Figure 7c This is a schematic diagram of the 0.656µm point spread function in an embodiment of the present invention;

[0030] Figure 8 This is the curve showing the variation of the optimized weights with wavelength in an embodiment of the present invention;

[0031] Figure 9 This is a schematic diagram of the visible light imaging lens structure according to an embodiment of the present invention;

[0032] Figure 10a This is a schematic diagram of the visible light imaging lens dot array according to an embodiment of the present invention;

[0033] Figure 10b It is a standard lens dot diagram;

[0034] Figure 11a This is a schematic diagram of the transfer function of a visible light imaging lens according to an embodiment of the present invention;

[0035] Figure 11b This is a schematic diagram of the transfer function of a standard lens;

[0036] Figure 12a This is a schematic diagram of visible light imaging lens aberrations according to an embodiment of the present invention;

[0037] Figure 12b This is a diagram illustrating the aberrations of a standard lens;

[0038] Explanation of reference numerals in the attached drawings: 101, first lens; 102, second lens; 103, filter; 104, lens barrel; 105, spacer for the first lens; 106, spacer for the second lens; 107, pressure ring; Detailed Implementation

[0039] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0040] This invention aims to reduce lens size, weight, and cost while ensuring image quality. It designs a joint optimized visible light imaging method and corresponding lens based on a multi-band cross-channel prior algorithm for image restoration. By combining the image restoration algorithm's performance, it selectively corrects aberrations in specific bands and samples and controls the point spread function of each field of view, thereby reducing the number of lenses and the overall size and weight of the optical system. The actual image produced by the optical-algorithm co-designed lens is blurred and chromatic aberration-laden. The image restoration algorithm restores this blurred and chromatic aberration-laden image, ultimately achieving a clear, chromatic aberration-free image.

[0041] The following is combined with Figures 1 to 1 2. The visible light imaging method and apparatus of the present invention will be described. Figure 1 This is a schematic flowchart of the visible light imaging method according to an embodiment of the present invention, as shown below. Figure 1 As shown, the present invention provides a visible light imaging method for a visible light imaging lens, the visible light imaging lens including a first lens and a second lens at the near-image end, the visible light imaging method comprising:

[0042] S1. Obtain the initial image output from the second lens;

[0043] S2. Divide the initial image into regions to obtain multiple initial sub-images;

[0044] S3. For different initial sub-images and different imaging wavelengths of each initial sub-image, complex atomic images are obtained by restoring them according to different point spread functions.

[0045] S4. Stitch together all the complex atom images to obtain the restored image;

[0046] The imaging field of view is divided into multiple sub-fields of view, each corresponding to a sub-image. The different point spread functions are determined according to the different imaging wavelengths under different sub-fields of view.

[0047] like Figure 2 As shown, the visible light imaging lens of the present invention is a co-designed lens, and... Figure 3 Compared with standard imaging lenses, the jointly designed lens suffers from under-optimized aberrations, and the point spread function is inconsistent across different fields of view. Using the same point spread function to reconstruct the image cannot guarantee algorithm performance. Therefore, this invention divides the imaging field of view into multiple blocks, such as N×N blocks. A point spread function is determined for each sub-field of view at different imaging wavelengths.

[0048] Taking the working wavelength range of 0.48μm to 0.65μm as an example, the imaging wavelengths include 0.656μm, 0.546μm, and 0.486μm. For each sub-image, the three imaging wavelengths are restored separately to obtain an imaging wavelength sub-image.

[0049] Initial image as follows Figure 4 The restored sub-images are then stitched together to form a full-frame restored image, as shown below. Figure 5 As shown. By Figure 5 and Figure 4 The comparison shows that the restored image eliminates blur and color difference.

[0050] Furthermore, simulated imaging is performed on the standard lens, such as... Figure 6 As shown. By restoring the image ( Figure 5 ) and standard lens imaging ( Figure 6 The comparison shows that the quality of the restored image is close to the clear imaging quality of the standard lens, eliminating the blur of the image and compensating for the chromatic aberration of the system.

[0051] The visible light imaging method of this invention selectively corrects and optimizes aberrations in specific bands for different sub-fields of view, which can correct aberrations to the greatest extent and obtain a restored image consistent with a clear image. In addition to two lenses, no additional optical components and materials for aberration correction are required, thereby reducing the number of lenses, size and weight of the optical system, thus reducing the cost of the optical system and improving the portability of the lens assembly.

[0052] In one embodiment, before acquiring the initial image output by the second lens, the method further includes: determining an error function based on the sagittal ray transverse aberration, the meridional ray transverse aberration, and the wavelength weight of each imaging wavelength; and determining the lens parameters by gradually adjusting the lens parameters and the weight of each wavelength until the error function converges; wherein the lens parameters include the distance between the first lens and the second lens, the radius of curvature of the first lens, the radius of curvature of the second lens, and the image distance, and the sagittal ray transverse aberration and the meridional ray transverse aberration are determined based on the lens parameters.

[0053] like Figure 2 As shown, the distance between the first lens and the second lens is 2-4 spacing (ignoring the lens thickness), the first lens is 1-2, the second lens is 4-5, and the image distance is 5-6. Taking the working wavelength band of 480nm~65nm as an example, the imaging wavelength includes red, green and blue.

[0054] To further improve the accuracy of image restoration after imaging, this invention specifically designs the lens parameters and uses an error function for optimization. It is easy to understand that the sagittal and meridional transverse aberrations can be obtained from the aforementioned lens parameters; specific calculation formulas are not given here. Furthermore, this invention sets wavelength weights according to different imaging wavelengths; the larger the wavelength weight, the greater its contribution to the error function and the stronger the correction capability. In addition, this invention selectively corrects for different wavelengths, thereby avoiding aberrations caused by different correction results for different wavelengths.

[0055] In one embodiment, the error function includes:

[0056]

[0057] Where λ represents the imaging wavelength, W λ The wavelength weights are represented by Δx and Δy, which represent the sagittal and meridional transverse aberrations, respectively. Larger weights contribute more to the error function and thus have a stronger correction capability.

[0058] In one embodiment, for different initial sub-images and different imaging wavelengths of each initial sub-image, complex atomic images are obtained by restoring them according to different point spread functions, including: determining an objective function based on the complex atomic image, the initial sub-image, and the corresponding point spread function using a cross-prior algorithm; and optimizing the objective function to determine the complex atomic image.

[0059] Ray tracing can be performed in optical design software to simulate and obtain a blurred image (i.e., the initial image). The blurred image block is also divided into N×N blocks, corresponding one-to-one with the point spread function. The calculation method for the height m and width n of each sub-block image is as follows:

[0060] m = I H / N

[0061] n = I V / N

[0062] Among them, I H The horizontal resolution of a full-frame image, such as 1080, I V This represents the vertical resolution of the full-frame image, such as 1920.

[0063] Based on the clear and blurred images of the current channel, and using a cross-prior algorithm, image restoration processing is performed on N×N sub-images to determine each complex atomic image. The cross-prior algorithm assumes that the gradients of the image are consistent across all channels. The objective function for restoration calculation includes the complex atomic image, the initial sub-image, and the point spread function. Essentially, optimization (e.g., minimizing the objective function) determines the complex atomic image.

[0064] In one embodiment, before obtaining the initial image output by the second lens, the method further includes: dividing the field of view of the visible light imaging lens into N×N sub-fields of view, where N is a positive integer greater than 1; for each sub-field of view and each imaging wavelength, determining the point spread function for each imaging wavelength under each sub-field of view based on ray tracing, thereby obtaining the different point spread functions.

[0065] The imaging field of view is divided into N×N, and the segmentation method is as follows:

[0066] W Hi =i·W H / N

[0067] W Vi =i·W V / N

[0068] Among them, W H For the full field of view in the horizontal direction, W V For the full field of view in the vertical direction, W Hi For the horizontal angle corresponding to the i-th field of view, W Vi Let be the vertical angle corresponding to the i-th field of view. By inputting the horizontal and vertical angles into optical design software, point spread functions for different angles can be obtained, such as... Figure 3 and 4 Set N=9.

[0069] Different point spread functions such as Figure 7a -c is shown. Figure 7a For the 0.656μm band, Figure 7b For the 0.546μm band, Figure 7c It is the 0.486µm band.

[0070] In one embodiment, the wavelength weight at the center of the wavelength range is greater than the wavelength weight at the edges. Because this invention has the ability to compensate for chromatic aberration at lens position, optimization of the central wavelength monochromatic aberration is prioritized in optical design, rather than requiring achromatic aberration.

[0071] In one embodiment, the different wavelength weights also include the following constraints:

[0072] W λ = a(λ-b) 2 +c

[0073] Where a is less than 0, c is greater than 0, and b is between the minimum and maximum imaging wavelengths.

[0074] As shown in the above formula, coefficient 'a' controls the maximum value of its weight, coefficient 'b' controls the position of the center wavelength, and coefficient 'c' controls the minimum value of the weight. By gradually adjusting the coefficients, iterative optimization can be completed in optical design software until the error function converges, thus completing the design of the combined lens. Figure 8 As shown, in one example, the value of coefficient b in the optimization can be -1.00E-3, the value of coefficient b can be 571, and the value of coefficient c can be 8.00.

[0075] like Figure 9 As shown, the present invention also provides a visible light imaging lens, comprising: an optical component and a structural component for fixing the optical component; the optical component includes a first lens 101 and a second lens 102 at the near-image end.

[0076] The lens parameters are determined when the error function converges. The error function is determined based on the sagittal ray transverse aberration, the meridional ray transverse aberration, and the wavelength weight of each imaging wavelength. The sagittal ray transverse aberration and the meridional ray transverse aberration are determined based on the lens parameters. The lens parameters include the distance between the first lens 101 and the second lens 102, the radius of curvature of the first lens 101, the radius of curvature of the second lens 102, and the image distance.

[0077] The lens includes optical components and structural components. The optical components include two lenses, and in one embodiment, it also includes a filter 103 at the second lens 102. Taking the case including the filter 103 as an example, light enters from the first lens 101, is refracted by the second lens 102, and then imaged onto the detector by the filter 103.

[0078] In one embodiment, the structural components include a first lens spacer 105, a second lens spacer 106, and a retaining ring 107 for fixing the lens, and a lens barrel 104 for carrying the optical components.

[0079] The focal length can be set to 50mm, the F-number to 6, and it is compatible with a CCD with a resolution of 1920×1080 and a pixel size of 2.75μm. The first lens 101 is a plano-convex lens with a radius of curvature of 42.85mm and infinity, and is fixed in the lens barrel 104 by adhesive. The second lens 102 is a biconvex lens with a radius of curvature of 21.59mm and -185.17mm, and it is pressed and fixed in the lens barrel 104 along with the filter 103 by a retaining ring 107. The lens barrel 104 has threaded holes on its circumferential surface that mates with the first lens 101 and the second lens 102 for adjusting the center offset of the lenses. The center distance between the first lens 101 and the second lens 102 can be maintained by adjusting the thickness of the first lens spacer 105.

[0080] The present invention also provides a visible light imaging device, including the aforementioned visible light imaging lens and a restoration component. The restoration component includes: an acquisition module for acquiring an initial imaging image output by a second lens; a splitting module for dividing the initial imaging image into regions to obtain multiple initial sub-images; a restoration module for restoring complex atomic images based on different point spread functions for different initial sub-images and different imaging wavelengths of each initial sub-image; and a stitching module for stitching together all complex atomic images to obtain a restored imaging image. The imaging field of view is divided into multiple sub-fields of view, each corresponding to a sub-image, and the different point spread functions are determined based on different imaging wavelengths under different sub-fields of view.

[0081] The actual image formed by the lens is a blurry image with chromatic aberration. This invention uses a restoration component to accurately measure the point spread function of the lens spatial changes and an image restoration algorithm to restore the blurry image with chromatic aberration and finally achieve clear, chromatic aberration-free imaging.

[0082] In this invention, a standard imaging lens with the same operating wavelength, focal length, and F-number was designed as a comparison object, as described above. Figure 3 As shown. Compared to the co-designed lens, an additional set of cemented lenses is used to correct aberrations. The dot plot, optical transfer function, and aberration comparison of the co-designed lens are shown below. Figure 10a and 10b , Figure 11a and 11b , Figure 12a and 12b As shown in the figure, the spot size of the co-designed lens is significantly larger than that of the standard lens, its transfer function is lower, and it exhibits a large positional chromatic aberration.

[0083] Simulated imaging using a standard lens produces clear images with no chromatic aberration, specifically as follows: Figure 6 As shown. By restoring the image ( Figure 5 ) and standard lens imaging ( Figure 6 The comparison shows that the quality of the restored image is close to that of the standard lens, indicating that the jointly designed lens of the present invention can match the image restoration algorithm well and can also obtain a clear restored image without color difference, thereby realizing the lens's lightweight and low cost.

[0084] Furthermore, this invention also provides a computer-readable storage medium, such as flash memory, hard disk, multimedia card, card-type memory (e.g., SD or DX memory), random access memory (RAM), static random access memory (SRAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), programmable read-only memory (PROM), magnetic memory, disk, optical disk, server, app store, etc., which stores a computer program, and the program performs corresponding functions when executed by a processor. In this embodiment, the computer-readable storage medium, when executed by a processor, implements a visible light imaging method.

[0085] It should be noted that, depending on the implementation needs, the various steps / components described in this application can be broken down into more steps / components, or two or more steps / components or parts of the operation of steps / components can be combined into new steps / components to achieve the purpose of this invention.

[0086] The order of the steps in the above embodiments does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0087] It should be understood that those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. A visible light imaging method, characterized in that, For a visible light imaging lens, the visible light imaging lens including a first lens and a second lens at the near-image end, the method includes: Obtain the initial image output from the second lens; The initial image is divided into regions to obtain multiple initial sub-images; For different initial sub-images and different imaging wavelengths of each initial sub-image, complex atomic images are obtained by restoring them according to different point spread functions; By stitching together all the complex atomic images, a restored image is obtained; The imaging field of view is divided into multiple sub-fields of view, each corresponding to a sub-image. The different point spread functions are determined according to the different imaging wavelengths under different sub-fields of view.

2. The visible light imaging method according to claim 1, characterized in that, Before acquiring the initial image output by the second lens, the process also includes: The error function is determined based on the sagittal ray perpendicular aberration, the meridional ray perpendicular aberration, and the wavelength weight of each imaging wavelength; The lens parameters are determined by gradually adjusting the lens parameters and the weight of each wavelength until the error function converges. The lens parameters include the distance between the first lens and the second lens, the radius of curvature of the first lens, the radius of curvature of the second lens, and the image distance. The transverse aberration and the meridional transverse aberration are determined based on the lens parameters.

3. The visible light imaging method according to claim 2, characterized in that, The error function includes: in, Indicates the imaging wavelength value. Indicates wavelength weighting. and These represent the transverse aberration of the sagittal ray and the transverse aberration of the meridional ray, respectively.

4. The visible light imaging method according to claim 1, characterized in that, For different initial sub-images and different imaging wavelengths for each initial sub-image, complex atomic images are obtained by restoring them according to different point spread functions, including: Based on the cross-prior algorithm, the objective function is determined according to the complex atomic image, the initial sub-image, and the different point spread functions; The objective function is optimized to determine the complex atom image.

5. The visible light imaging method according to claim 1, characterized in that, Before acquiring the initial image output by the second lens, the process also includes: The field of view of the visible light imaging lens is divided into N×N sub-fields of view, where N is a positive integer greater than 1; For each sub-field of view and each imaging wavelength, the point spread function for each imaging wavelength under each sub-field of view is determined based on ray tracing, thus obtaining the different point spread functions.

6. The visible light imaging method according to claim 2, characterized in that, The wavelengths located in the center of the wavelength range have a greater weight than those located at the edges.

7. The visible light imaging method according to claim 6, characterized in that, The weight values ​​for different wavelengths also include the following constraints: in, This indicates the imaging wavelength value, where a is less than 0, c is greater than 0, and b is between the minimum and maximum imaging wavelengths.

8. A visible light imaging lens, characterized in that, include: Optical components and structural components for fixing the optical components; The optical component includes a first lens and a second lens at the near-image end, and it is specifically imaged using the visible light imaging method according to any one of claims 1-7. The lens parameters are determined when the error function converges. The error function is determined based on the sagittal ray transverse aberration, the meridional ray transverse aberration, and the wavelength weight of each imaging wavelength. The sagittal ray transverse aberration and the meridional ray transverse aberration are determined based on the lens parameters. The lens parameters include the distance between the first lens and the second lens, the radius of curvature of the first lens, the radius of curvature of the second lens, and the image distance.

9. The visible light imaging lens according to claim 8, characterized in that, The structural components include a lens spacer and a pressure ring for fixing the lens, and a lens barrel for carrying the optical components.

10. A visible light imaging device, characterized in that, Including the visible light imaging lens and restoration assembly as described in claim 8 or 9, the restoration assembly comprising: The acquisition module is used to acquire the initial image output by the second lens; The splitting module is used to divide the initial image into regions to obtain multiple initial sub-images; The restoration module is used to restore complex atomic images based on different point spread functions for different initial sub-images and different imaging wavelengths of each initial sub-image. The stitching module is used to stitch together all complex atomic images to obtain a restored image. The imaging field of view is divided into multiple sub-fields of view, each corresponding to a sub-image. The different point spread functions are determined according to the different imaging wavelengths under different sub-fields of view.

Images