CN115265784A - Computed tomography spectrometer based on super-surface diffraction element - Google Patents
Computed tomography spectrometer based on super-surface diffraction element Download PDFInfo
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- CN115265784A CN115265784A CN202210972225.8A CN202210972225A CN115265784A CN 115265784 A CN115265784 A CN 115265784A CN 202210972225 A CN202210972225 A CN 202210972225A CN 115265784 A CN115265784 A CN 115265784A
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- 238000002591 computed tomography Methods 0.000 title claims abstract description 36
- 238000003384 imaging method Methods 0.000 claims abstract description 19
- 230000003287 optical effect Effects 0.000 claims abstract description 15
- 239000000758 substrate Substances 0.000 claims description 13
- 238000000034 method Methods 0.000 claims description 8
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical group O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 6
- 239000002086 nanomaterial Substances 0.000 claims description 5
- 239000011159 matrix material Substances 0.000 claims description 4
- 230000010287 polarization Effects 0.000 claims description 4
- 229910052751 metal Inorganic materials 0.000 claims description 3
- 239000002184 metal Substances 0.000 claims description 3
- 239000000377 silicon dioxide Substances 0.000 claims description 3
- 238000013480 data collection Methods 0.000 claims 1
- 238000004519 manufacturing process Methods 0.000 abstract description 8
- 230000000694 effects Effects 0.000 abstract description 2
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical group O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 238000009826 distribution Methods 0.000 description 2
- 235000012239 silicon dioxide Nutrition 0.000 description 2
- 238000010521 absorption reaction Methods 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000000701 chemical imaging Methods 0.000 description 1
- 239000006185 dispersion Substances 0.000 description 1
- 238000010894 electron beam technology Methods 0.000 description 1
- 238000002372 labelling Methods 0.000 description 1
- 230000000737 periodic effect Effects 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 239000004065 semiconductor Substances 0.000 description 1
- 238000004088 simulation Methods 0.000 description 1
- 230000003595 spectral effect Effects 0.000 description 1
- 238000004611 spectroscopical analysis Methods 0.000 description 1
- 238000001228 spectrum Methods 0.000 description 1
- 239000004408 titanium dioxide Substances 0.000 description 1
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
- G01J3/00—Spectrometry; Spectrophotometry; Monochromators; Measuring colours
- G01J3/28—Investigating the spectrum
- G01J3/2823—Imaging spectrometer
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
- G01J3/00—Spectrometry; Spectrophotometry; Monochromators; Measuring colours
- G01J3/02—Details
- G01J3/0205—Optical elements not provided otherwise, e.g. optical manifolds, diffusers, windows
- G01J3/0208—Optical elements not provided otherwise, e.g. optical manifolds, diffusers, windows using focussing or collimating elements, e.g. lenses or mirrors; performing aberration correction
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
- G01J3/00—Spectrometry; Spectrophotometry; Monochromators; Measuring colours
- G01J3/12—Generating the spectrum; Monochromators
- G01J3/18—Generating the spectrum; Monochromators using diffraction elements, e.g. grating
- G01J3/1838—Holographic gratings
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- Spectroscopy & Molecular Physics (AREA)
- General Physics & Mathematics (AREA)
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Abstract
The invention relates to a computed tomography spectrometer based on a super-surface diffraction element. The computed tomography spectrometer comprises an optical system structure, a focal plane detector and a data acquisition and processing system; the optical system structure comprises a converging lens group, a field diaphragm, a collimating lens group, a super-surface holographic grating and an imaging lens group. The invention combines the super surface with the computed tomography spectrometer, can avoid the difficulty in manufacturing the computed tomography spectrometer, miniaturizes the computed tomography spectrometer and can generate better diffraction effect, so that the overall sizes of the focal plane array target surface and the spectrometer are both millimeter level, and the imaging spectrometer with a mobile phone end and even a smaller structure can be realized.
Description
Technical Field
The invention relates to the field of snapshot type spectral imaging, in particular to a computed tomography spectrometer based on a super-surface diffraction element.
Background
Computed tomography spectroscopy, also known as computed tomography, is a technique for reconstructing high-dimensional objects from low-dimensional projection data. The three-dimensional information of a target image is detected by an optical means through the principle of computer tomography, projection images of a data cube in different directions are recorded by an imaging system, and then the three-dimensional data cube is reconstructed by a reconstruction algorithm. At present, the computed tomography spectrometer has more researches on the aspects of reconstruction of a spectrum data cube and target identification, and great progress is made.
However, the holographic grating, which is a key element of the computed tomography spectrometer, needs to be manufactured by electron beam exposure, and has complex process and higher manufacturing cost. Moreover, the smallest step of the traditional holographic grating is in the micron order, which causes the volume of the computed tomography spectrometer to be larger, so the microminiaturization of the computed tomography spectrometer is also a problem to be solved.
The super-surface manufacturing process is mature, is compatible with the traditional semiconductor process and has the advantage of easy manufacturing. Meanwhile, the minimum step diameter of the super surface is small, and the super surface belongs to nanometer level, and has light weight and thin thickness, so the super surface is expected to become a key element for manufacturing micro optical equipment. The super surface formed by densely arranging the nano-scale antennas can be used for manufacturing gratings, lenses, prisms and the like, so that the phase, polarization, intensity, frequency and orbital angular momentum can be controlled. Through the adjustment of the nano antenna, the dielectric super surface shows quite good performance in the aspects of frequency mixing, optical switching, efficiency, high absorption and the like. The super-surface is also utilized to achieve structured light projection to evenly distribute a collimated beam of light into an array of spots of uniform intensity, and advances are also made in holographic imaging. Therefore, the all-dielectric metamaterial can solve the manufacturing difficulty of core elements of the computed tomography spectrometer and can realize the miniaturization of the computed tomography spectrometer.
Disclosure of Invention
The invention aims to realize the microminiaturization design of a computed tomography spectrometer by using a super-surface diffraction element to replace a holographic grating.
In order to achieve the above purpose, the invention provides a computed tomography spectrometer based on a super-surface diffraction element, wherein the spectrometer comprises an optical system structure, a focal plane detector and a data acquisition and processing system. The optical system structure comprises a converging lens group, a field diaphragm, a collimating lens group, a super-surface holographic grating and an imaging lens group. The working process is as follows: the converging lens group converges incident light carrying target data cube information, the size of light beams entering the system is limited at a field diaphragm, light is collected and collimated by the collimating lens group and enters the super-surface holographic grating, after the light beams are dispersed by the super-surface holographic grating and the patterns are dispersed, the dispersive patterns are respectively focused by the imaging lens group to form diffraction orders, the focal plane detector simultaneously receives diffraction patterns of all levels, each level of diffraction pattern corresponds to the projection data of the diffraction direction, and the data acquisition and processing system collects the diffraction patterns of all levels and restores the target data cube through an algorithm.
The super-surface holographic grating of the key element of the computed tomography spectrometer is formed by the thickness of h 2 Has a base and a height h 1 Diameter is D i Wherein the substrate has a surface extending in x and y directions, and the surface unit structure is cylindrical and perpendicular to the substrate.
In some embodiments, the array of surface unit structures is arranged in a matrix and is composed of 1 or more macro-periods, and the macro-periods are arranged in a matrix in the x and y directions of the substrate.
In some embodiments, each large period of the surface unit structure is formed by combining a plurality of surface unit structures with different diameters and the same height, and the super-surface holographic grating regulates the number of diffraction orders on a focal plane detector and the shape of a diffraction pattern by changing the diameters of the surface unit structures at different positions.
The super-surface holographic grating is a nano-structure array, and the nano-structure is a polarization-independent structure.
In some embodiments, the super-surface holographic grating substrate is silicon dioxide and the surface unit structure is a sub-wavelength metal or a high refractive index medium.
In some embodiments, the imaging optics group is a zoom lens to change the size of the image on the focal plane detector.
In some embodiments, the converging lens group, the collimating lens group, and the imaging lens group are composed of one or more lenses.
In some embodiments, the field stop is a two-dimensional aperture.
Compared with the prior art, the invention has the beneficial effects that: the invention can avoid the manufacturing difficulty of the computed tomography spectrometer, miniaturize the computed tomography spectrometer and generate better diffraction effect, so that the overall size of the target surface of the focal plane detector and the spectrometer is in millimeter order, and the imaging spectrometer with a mobile phone end and even a smaller structure is expected to be realized.
Drawings
FIG. 1 is a schematic diagram of a computed tomography spectrometer according to the present invention.
FIG. 2 is a schematic structural diagram of a large period of a super-surface holographic grating provided in an embodiment of the present invention.
FIG. 3 is a structural parameter of a super-surface holographic grating with a small period according to an embodiment of the present invention.
Fig. 4 is a phase profile of an embodiment of the present invention.
FIG. 5 is a superimposed diffraction pattern of an embodiment of the invention.
Description of the labeling: 1. an optical system structure; 2. a focal plane detector; 3. a data acquisition processing system; 11. a converging lens group; 12. a field stop; 13. a collimating lens group; 14. a super-surface holographic grating; 15. an imaging lens group.
Detailed Description
In order to more clearly illustrate the technical solution of the present invention, the technical solution of the present invention is further described in detail with reference to the accompanying drawings and specific embodiments. It should be understood that the preferred embodiments described herein are for purposes of illustration and explanation only and are not intended to limit the invention:
the invention provides a computed tomography spectrometer based on a super-surface diffraction element, which comprises an optical system structure 1, a focal plane detector 2 and a data acquisition and processing system 3 as shown in figure 1, and is characterized in that the optical system structure 1 comprises a convergent lens group 11, a field stop 12, a collimating lens group 13, a super-surface holographic grating 14 and an imaging lens group 15; the working process comprises the following steps: the converging lens group 11 converges incident light carrying target data cube information, the size of light beams entering the system is limited at a field diaphragm 12, light is collected and collimated by the collimating lens group 13 and enters the super-surface holographic grating 14, after the light is dispersed by the super-surface holographic grating 14 and the patterns are dispersed, the dispersed patterns are respectively focused by the imaging lens group 15 to form diffraction orders, the focal plane detector 2 simultaneously receives diffraction patterns of all levels, each diffraction pattern corresponds to projection data in the diffraction direction, and the data acquisition and processing system 3 collects the diffraction patterns of all levels and restores the target data cube through an algorithm.
To further illustrate the details of the key components of the super-surface holographic grating 14 of the computed tomography spectrometer, fig. 2 and 3 are taken as examples:
the super-surface holographic grating 14 is a nanostructure array, and the nanostructure is a polarization-independent structure.
The super-surface holographic grating 14 is formed by the thickness h 2 Has a base and a height h 1 Diameter is D i Wherein the substrate has a surface extending in the x, y directions, repeating with a period d, the surface unit structure being cylindrical and perpendicular to the substrate. The direction of propagation of the incident light is the z-direction.
Each large period of the surface unit structure array is formed by combining a plurality of surface unit structures with different diameters and the same height, and the super-surface holographic grating 14 regulates the number of diffraction orders and the shape of diffraction patterns on the focal plane detector 2 by changing the diameters of the surface unit structures at different positions.
The substrate of the super-surface holographic grating 14 is silicon dioxide, and the surface unit structure is sub-wavelength metal or high-refractive-index medium.
In a specific embodiment of the invention, the surface unit structure is titanium dioxide.
When the diameter of the surface unit structure is designed, the phase modulation amount of the super-surface holographic grating array 14 meets the phase coverage of 2 pi at the designed central wavelength, and under the condition, the phase coverage is as large as possible at each wavelength in the designed waveband range.
In the structure of the optical system, the converging lens group 11, the collimating lens group 13 and the imaging lens group 15 are composed of one or more lenses, and the field diaphragm 12 is a two-dimensional aperture.
The coordinates referred to herein are the z coordinate of the optical axis, and the x, y coordinates are established perpendicular to the plane of the optical axis.
In the method, after the diffraction pattern information of each level obtained on the focal plane detector 2 is obtained by the data acquisition and processing system 3, the information is restored through an image reconstruction algorithm, and a three-dimensional data cube is obtained again.
In the specific embodiment of the present invention, in the wavelength range of 550nm to 1000nm, the computed tomography spectrometer can implement corresponding phase retardation by setting the diameter of each surface unit structure in the large period of the super-surface holographic grating 14, disperse incident light, implement diffraction projection of light, generate a two-dimensional diffraction pattern of 5 × 5 orders, and implement imaging on the focal plane detector 2.
In a specific embodiment of the present invention, the super-surface holographic grating 14 can disperse and focus the input real three-dimensional data cube sample to form a diffraction pattern. The simulation process of the computed tomography spectrometer described in the present invention is described in further detail below with reference to fig. 2, 3, 4 and 5.
In the embodiment of the present invention, when the number of small periods per large period is 15 × 15, the phase distribution is as shown in fig. 4, and the large periods are repeated 15 times in the x and y directions. The incident wavelength range is 550nm-1000nm.
In a specific embodiment of the present invention, a super-surface holographic grating 14 is obtained by arranging each of the surface unit structures according to the phase distribution of FIG. 4. Wherein a large periodic structure is shown in figure 2. Super surface holographic grating 14 substrate thickness h 2 =150nm, small period substrate side length d =250nm, surface unit structure height h 1 =700nm, diameter 20nm ≤ D i Less than or equal to 250nm. The focal length of the imaging lens group 15 is 15mm, and the size of the target surface of the focal plane detector 2 is 3.6mm multiplied by 3.6mm.
The diffraction pattern obtained by the super-surface holographic grating 14 is shown in FIG. 5, and has a total of five (0, + -1, + -2) diffraction orders. The superposed spectral images have 11 wave bands in total and the wavelength interval is 35nm. And restoring the multispectral superposed dispersion map obtained on the focal plane detector 2 by an expectection-Maximization algorithm to obtain a restored three-dimensional data cube.
The principles and specific embodiments of this structure are explained in detail herein with reference to the drawings and examples. Further, it will be apparent to those skilled in the art that variations may be made in the specific embodiments or applications without departing from the spirit of the invention. In summary, the content of the present specification should not be construed as limiting the present invention, and all applications and inventive creations utilizing the idea of the present invention are protected.
Claims (9)
1. A computed tomography spectrometer based on a super-surface diffraction element comprises an optical system structure (1), a focal plane detector (2) and a data acquisition and processing system (3), and is characterized in that the optical system structure comprises a converging lens group (11), a field diaphragm (12), a collimating lens group (13), a super-surface holographic grating (14) and an imaging lens group (15); the working process is as follows: the converging lens group (11) converges incident light carrying target data cube information, the size of the light beam entering the system is limited at a field diaphragm (12), the light is collected and collimated by the collimating lens group (13) and enters the super-surface holographic grating (14), after being dispersed by the super-surface holographic grating (14) and the pattern is dispersed, the dispersive pattern is focused by the imaging lens group (15) to form each diffraction order, each diffraction order is received by the focal plane detector (2) simultaneously, each diffraction order corresponds to the projection data of the diffraction direction, and the data collection processing system (3) collects each diffraction order and restores the target data cube through an algorithm.
2. The super surface diffraction element-based computed tomography spectrometer according to claim 1, wherein the super surface holographic grating (14) is formed by a thickness h 2 Base and height h 1 Diameter is D i Wherein the substrate has a surface extending in x and y directions, and the surface unit structure is cylindrical and perpendicular to the substrate.
3. The super surface diffraction element-based computed tomography spectrometer of claim 2, wherein the array of surface unit structures is arranged in a matrix consisting of 1 or more large periods arranged in a matrix in the x, y direction of the substrate.
4. The super surface diffraction element-based computed tomography spectrometer according to claim 3, wherein the surface unit structures are combined with a plurality of surface unit structures with different diameters and same height for each large period, and the super surface holographic grating (14) regulates the number of diffraction orders and the shape of the diffraction pattern on the focal plane detector (2) by changing the diameters of the surface unit structures at different positions.
5. The super surface diffraction element-based computed tomography spectrometer according to claim 1, wherein the super surface holographic grating (14) is an array of nanostructures that are polarization independent structures.
6. The super surface diffraction element-based computed tomography spectrometer of claims 5 to 3, wherein the substrate is silica and the surface unit structure is a sub-wavelength metal or a high refractive index medium.
7. The super surface diffraction element based computed tomography spectrometer according to claim 1, wherein the imaging optics group (15) is a zoom lens to change the size of the image on the focal plane detector.
8. The super surface diffraction element-based computed tomography spectrometer according to claim 1, wherein the converging lens group (11), the collimating lens group (13), and the imaging lens group (15) are composed of one or more lenses.
9. The super surface diffraction element-based computed tomography spectrometer according to claim 1, wherein the field stop (12) is a two-dimensional aperture.
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| CN116222433A (en) * | 2023-03-22 | 2023-06-06 | 西安知象光电科技有限公司 | Structured light three-dimensional imaging system and method based on super surface |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN116222433A (en) * | 2023-03-22 | 2023-06-06 | 西安知象光电科技有限公司 | Structured light three-dimensional imaging system and method based on super surface |
| CN116222433B (en) * | 2023-03-22 | 2023-09-05 | 西安知象光电科技有限公司 | Structured light three-dimensional imaging system and method based on super surface |
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