Superlens spectral imaging system
By employing a spectroscopic imaging system with biconvex lenses, aspherical mirrors, and reflective planar dispersive superlenses, the problems of large size and heavy weight in existing spectral imaging systems have been solved, achieving compact, high-resolution spectral imaging that is suitable for the miniaturization requirements of aerospace payloads.
Patent Information
- Application Number
- CN202521328853.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2025-06-26
- Publication Date
- 2026-03-20
- Estimated Expiration
- 2035-06-26
AI Technical Summary
Existing spectral imaging systems are large and heavy, and are difficult to manufacture and assemble, making them unsuitable for civilian use and unable to meet the miniaturization requirements of aerospace payloads.
A beam splitting imaging system is adopted, consisting of two biconvex lenses, one aspherical mirror, and one reflective plane dispersive superlens. The reflective plane dispersive superlens is used to disperse and split the light rays, and the aspherical mirror and biconvex lenses are combined to converge and correct the beam. The slit incident plane of the system is located on the same side as the image plane, and the aperture stop is set at the reflective plane dispersive superlens.
It achieves compact spectral imaging with high spatial and spectral resolution. The system is small in size and light in weight, which simplifies the manufacturing and assembly process and improves the imaging quality.
Smart Images
Figure CN224019157U_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The utility model relates to a kind of spectroscopic imaging systems using reflective plane dispersion superlens as light splitting element, belong to spectral imaging technical field. BACKGROUND
[0002] Spectral imaging detector not only can collect the color image of target area, but also can obtain the corresponding spectral information of spatial point in working waveband, i.e. obtain the three-dimensional data cube of target area. With the cross development of computational imaging, optical process detection and other disciplines, the imaging performance of spectral imaging system is continuously improved, has become one of the research hotspots in current optical field, and has been applied in many fields such as environmental monitoring, forestry exploration, food quality analysis, biological medicine. In the early stage of the development of spectral imaging technology, limited by the technology level at that time, spectral imaging system is bulky and has poor imaging quality. With the development of modern aerospace and unmanned aerial vehicle technology, to meet the detection needs of aerospace load wide spectrum and miniaturization, the detection instrument carried by aircraft is required to have high resolution while having smaller volume and lighter quality.
[0003] Before the utility model is made, the document "Design of Offner-type hyperspectral imaging system" (see document: China Science and Technology Papers, 2016, 11 (20): 2316-2320) reports a kind of spectroscopic imaging system based on offner structure and introducing curved surface dispersion prism;The system is composed of two concave spherical mirrors, a convex spherical mirror and two pieces of glued curved surface dispersion prism;The system separates the large-aperture mirror in the initial offner structure into two small-aperture mirrors, increases the variables such as deviation and tilt angle as degrees of freedom, at the same time, the curvature radius, deviation and tilt angle of curved surface prism are used as variables, to further improve the correction ability of system off-axis aberration, but its design complexity is high, system volume is large, mass is heavy, and processing and adjustment difficulty is large, not suitable for civilianization. SUMMARY
[0004] The utility model provides a kind of superlens spectroscopic imaging system for realizing high space and spectral resolution, structure light and small type in view of the deficiency of prior art.
[0005] The technical scheme for achieving the object of the utility model provides a superlens light-splitting imaging system, slit incidence planes and image planes of the system are located on the same side in space, optical elements of the system include two pieces of double convex lenses, an aspherical mirror that is bent towards the direction of light incidence, and a reflective plane dispersion superlens, an aperture stop of the system is arranged at the reflective plane dispersion superlens; after polychromatic incident light passes through the incidence slit, the polychromatic incident light is converged to the aspherical mirror by the first piece of double convex lens, the aspherical mirror reflects the convergent light beam to the reflective plane dispersion superlens, after dispersion of light by the superlens, monochromatic divergent light beams of different wavelengths are reflected to the aspherical mirror, and the aspherical mirror reflects the obtained monochromatic divergent light beams to the second piece of double convex lens and converges the monochromatic divergent light beams at the image plane.
[0006] Each surface of the first piece of double convex lens and the second piece of double convex lens is a spherical surface, and in the direction of light incidence, the radii of curvature of the front and rear surfaces thereof are R 21 , R 22 , R 51 , R 52 , respectively, and satisfy the conditions 67mm≤R 21 ≤70mm, -58mm≤R 22 ≤-56mm, -52mm≤R 51 ≤-46mm, and 60mm≤R 52 ≤77mm.
[0007] The reflecting surface of the aspherical mirror is an XY polynomial free surface, a coordinate system thereof is a Cartesian space right-angle coordinate system constructed with the vertex of the free surface mirror as the origin O, the direction of light incidence is the positive direction of the Z axis, the positive direction of the Y axis is upward, and the positive direction of the X axis is outward, and the equation of the XY polynomial free surface in the coordinate system is:
[0008]
[0009] wherein, is a radial coordinate on the mirror surface; c is a curvature, c=-0.01; k is a quadratic surface coefficient, and the value range is -1.31≤k≤-1.28; a 1～ a9 are coefficients of respective monomials, and the value ranges are 0.14≤a1≤0.23, -0.19≤a2≤-0.17, 0.798≤a3≤0.808, 0.005≤a4≤0.012, 0.377≤a5≤0.382, 0.175≤a6≤0.186, -0.070≤a7≤-0.045, -0.030≤a8≤-0.009, and -0.682≤a9≤-0.673.
[0010] The light aperture R of the reflective plane dispersion super lens is 9.92mm≤R≤9.96mm; the super lens comprises a sub-wavelength scale titanium dioxide nanocolumn unit structure, a silver reflection layer and a PDMS polymer; the lattice constant p1 of the nanocolumn unit structure is 255nm; the nanocolumn has a height of 560nm and a square cross section with a side length of 50nm-170nm; the nanocolumn is wrapped by a PDMS polymer with a height of 1000nm, and a silver layer with a thickness of 100nm is deposited at the bottom of the PDMS polymer.
[0011] The polynomial expression of the phase profile of the reflective plane dispersion super lens surface corresponding to different wavelengths is j Satisfying the condition:
[0012]
[0013] Wherein, the diffraction order of the surface of the reflective plane dispersion super lens is M, N is the number of polynomial coefficients, the polynomial E ij (x,y) is the power series of x and y, A ij is the coefficient of each term of the polynomial, represents the coefficient of the i-th term of the phase distribution polynomial of wavelength j, and the value range is 1000≤A 11 ≤1400,5100≤A 21 ≤5600,5≤A 31 ≤25,5≤A 41 ≤25,3365≤A 51 ≤3385,-250≤A 61 ≤-235,-375≤A 71 ≤-350,1≤A 81 ≤25,600≤A 12 ≤1000,1500≤A 22 ≤1850,-50≤A 32 ≤-30,10≤A 42 ≤20,2155≤A 52 ≤2170,-170≤A 62 ≤-155,-255≤A 72 ≤-235,5≤A 82 ≤15,400≤A 13 ≤650,-100≤A 23 ≤-20,-70≤A 33 ≤-55,4≤A 43 ≤12,1561≤A 53 ≤1574,-125≤A 63 ≤-113,-200≤A 73 ≤-180,1≤A 83 ≤7.
[0014] The superlens light-splitting imaging system has a system numerical aperture NA of 0.12<=NA<=0.16, and a barrel length L of 58<=L<=62mm.
[0015] Compared with the prior art, the utility model has the advantages that:
[0016] 1. The light-splitting imaging system provided by the utility model only has two pieces of double-convex lens for correction, one piece of aspheric mirror and one piece of reflective plane dispersion superlens as light-splitting elements, the optical barrel length TOTR of the obtained light-splitting imaging system is less than 65mm, and the light-splitting imaging system has the characteristics of compact structure, small volume and light weight.
[0017] 2. The utility model adopts the mirror with a free curved surface shape, avoids the difficulties caused by the inclination and eccentricity of the mirror in system assembly and alignment, and effectively balances the residual aberration of the system, thereby effectively improving the imaging quality.
[0018] 3. The utility model sets two pieces of correction lenses in the optical path, realizes spectral imaging with high spatial and spectral resolution in a compact structure, the lens surfaces of the lenses are all standard spherical surfaces, the difficulty and cost of lens processing are reduced, the lenses have the advantages of small volume and light weight, and have practical application value. BRIEF DESCRIPTION OF DRAWINGS
[0019] Figure 1 is a structural schematic diagram of the light-splitting imaging system provided by the utility model embodiment;
[0020] Figure 2 is a schematic diagram of the reflective plane dispersion superlens dispersion unit provided by the utility model embodiment;
[0021] Figure 3 is a ray tracing point column diagram of the light-splitting imaging system provided by the utility model embodiment;
[0022] Figure 4 is a transfer function MTF curve diagram of the light-splitting imaging system provided by the utility model embodiment.
[0023] 1, slit plane; 2, first piece of double-convex lens; 3, aspheric mirror; 4, reflective plane dispersion superlens; 5, second piece of double-convex lens; 6, image plane. DETAILED DESCRIPTION
[0024] The specific implementation scheme of the utility model embodiment will be further described below in combination with the drawings and the embodiment.
[0025] Embodiment 1:
[0026] This embodiment provides a small-scale spectroscopic imaging system for pushbroom spectral imaging systems. The system consists of only two biconvex lenses, one aspherical mirror, and one reflective planar dispersive superlens, with an object-side numerical aperture NA = 0.13; a slit length of 14 mm; and an operating wavelength range of 400-800 nm. Its spectral resolution within the operating wavelength range is better than 1.2 nm, and it exhibits good dispersion linearity. When this system is mounted on an electric turntable for pushbroom imaging of a target area, the system acquires 333 spectral channels in the visible light band.
[0027] See appendix Figure 1 This is a schematic diagram of the beam splitting imaging system provided in this embodiment. The slit plane 1 and the image plane 6 are located on the same side in space. According to the direction of light incidence, the optical elements are, in sequence, a first biconvex lens 2, an aspherical mirror 3, a reflective planar dispersive superlens 4, and a second biconvex lens correction lens 5. During imaging, the incident light beam passes through the slit on the slit plane and exits. After being corrected by the first biconvex lens, it converges and is incident on different areas of the aspherical mirror. Then, it is reflected by the aspherical mirror to different areas of the reflective planar dispersive superlens. After dispersion, the beam is split into monochromatic diverging beams of different wavelengths and is again incident on different areas of the aspherical mirror. Finally, it is reflected to the second biconvex lens, and after correction, the beam converges at the image plane, achieving simultaneous acquisition of spectral and spatial information within the visible light band of the target area.
[0028] The parameters of each optical element in this embodiment are shown in Table 1.
[0029] Table 1:
[0030]
[0031] The reflective planar dispersive superlens provided in this embodiment includes a subwavelength-scale titanium dioxide nanopillar unit structure, a silver reflective layer, and a PDMS (Polydimethylsiloxane) polymer.
[0032] See appendix Figure 2 This is a schematic diagram of the dispersive unit of the reflective planar dispersive superlens provided in this embodiment. The dispersive unit is a nanopillar unit structure, composed of... Figure 2 As can be seen, the titanium dioxide nanopillars are encapsulated by PDMS polymer. The lattice constant p1 of the nanopillars is 255 nm, the height h1 is 560 nm, the side length D of the square cross-section of the nanopillars is 50 nm to 170 nm, and the height h2 of the PDMS is 1000 nm. After being spin-coated and cured, it serves as a protective layer to prevent the nanopillars from being damaged in subsequent processes. A silver layer with a thickness h3 of 100 nm is deposited at the bottom of the polymer to form a reflective unit structure.
[0033] The light passing aperture of the reflective planar dispersion superlens in this embodiment is 9.83 mm, and the surface phase profile expression of the reflective planar dispersion superlens is j As shown in formula (1), the phase response to different wavelengths is satisfied:
[0034]
[0035] wherein M is the diffraction order of the surface of the reflective superlens, N is the number of polynomial coefficients, and the polynomial E ij (x, y) is the normalized x and y power series, A ij is the polynomial coefficient. The parameters corresponding to different wavelengths in the phase profile expression of the super surface lens in this embodiment are shown in Table 2.
[0036] Table 2:
[0037]
[0038]
[0039] Since the phase distribution of the surface of the reflective planar dispersion superlens is different at different wavelengths, the reflective dispersion unit structure with a square cross section is adopted in this embodiment, and by selecting different square side lengths D, the reflective planar dispersion superlens is constructed to realize the phase response to different wavelengths.
[0040] In this embodiment, the reflecting surface of the aspheric mirror is an XY polynomial free surface, which is represented by the following polynomial:
[0041]
[0042] wherein is the radial coordinate on the mirror surface; c is the curvature, c = -0.01; k is the quadratic surface coefficient, k = -1.294; a1-a9 are the coefficients of each monomial. Exemplarily, the parameters of the aspheric mirror in this embodiment are shown in Table 3.
[0043] Table 3:
[0044] [a1] [a2] [a3] [a4] [a5] [a6] [a7] [a8] [a9] 0.179 -0.181 0.802 0.009 0.380 0.181 -0.058 -0.018 -0.677
[0045] Referring to FIG. 4, Figure 3 which is the ray tracing point list diagram of the light passing through the light splitting imaging system provided in this embodiment, the root mean square radius of the point list diagram of each field corresponding to the three wavelengths of 400 nm, 600 nm and 800 nm is less than 3 μm, and the geometric radius of the point list diagram is less than 8.0 μm.
[0046] Referring to FIG. 5, Figure 4 which is the transfer function MTF curve on the image surface corresponding to each field of the light splitting imaging system provided in this embodiment. As shown in FIG. 5, Figure 3It can be seen that, at the image plane, the MTF values of each field of view at 400 nm (a), 600 nm (b) and 800 nm (c) wavelengths are all greater than 0.72 when the cut-off frequency is 38.5 lp / mm, all close to the diffraction limit, and the curves are relatively smooth, indicating that the lens imaging is clear and uniform, and the system has good imaging quality in the full waveband and full field of view.
Claims
1. A superlens beam-splitting imaging system, characterized in that: The slit incident plane (1) and the image plane (6) of the system are located on the same side in space. The optical elements of the system include two biconvex lenses (2, 5), an aspherical mirror (3) bent towards the incident direction of the light rays, and a reflective plane dispersive superlens (4). The aperture stop of the system is set at the reflective plane dispersive superlens. After the polychromatic incident light rays pass through the incident slit, they are converged by the first biconvex lens (2) to the aspherical mirror (3). The aspherical mirror (3) reflects the converged light beam to the reflective plane dispersive superlens (4). After the superlens disperses the light, the monochromatic diverging light beams of different wavelengths are reflected to the aspherical mirror (3). The aspherical mirror (3) reflects the obtained monochromatic diverging light beams to the second biconvex lens (5) and then converges at the image plane (6). The first and second biconvex lenses each have spherical surfaces, and their radii of curvature, according to the direction of light incidence, are Rfront and Rrear, respectively. 21 R 22 R 51 R 52 They respectively satisfy the condition 67mm≤R 21 ≤70mm, -58mm≤R 22 ≤-56mm, -52mm≤R 51 ≤-46mm, 60mm≤R 52 ≤77mm; The reflecting surface of the aspherical mirror is an XY polynomial freeform surface, and its coordinate system is a Cartesian rectangular coordinate system constructed with the vertex of the freeform mirror as the origin O. The incident direction of light is the positive Z-axis, the positive Y-axis is upward, and the positive X-axis is outward. The equation of the XY polynomial freeform surface in the coordinate system is: in, denoted as the radial radius on the mirror surface; c is the curvature, c = -0.01; k is the quadratic surface coefficient, with a value range of -1.31 ≤ k ≤ -1.28; a1 to a9 are the coefficients of each monomial, with values ranging from 0.14 ≤ a1 ≤ 0.23, -0.19 ≤ a2 ≤ -0.17, 0.798 ≤ a3 ≤ 0.808, 0.005 ≤ a4 ≤ 0.012, 0.377 ≤ a5 ≤ 0.382, 0.175 ≤ a6 ≤ 0.186, -0.070 ≤ a7 ≤ -0.045, -0.030 ≤ a8 ≤ -0.009, -0.682 ≤ a9 ≤ -0.673; The aperture R of the aforementioned reflective planar dispersive superlens has a range of 9.92 mm ≤ R ≤ 9.96 mm. The superlens comprises a subwavelength titanium dioxide nanopillar unit structure, a silver reflective layer, and a PDMS polymer. The lattice constant p1 of the nanopillar unit structure is 255 nm. The nanopillars have a height of 560 nm and a square cross-section with a side length of 50 nm to 170 nm. The nanopillars are encapsulated by a PDMS polymer with a height of 1000 nm, and a silver layer with a thickness of 100 nm is deposited at the bottom of the PDMS polymer. The polynomial expression φ for the surface phase profile of a reflective planar dispersive superlens corresponding to different wavelengths. j Conditions met: In this context, the diffraction order of the reflective planar dispersive superlens is M, N is the number of polynomial coefficients, and the polynomial E is... ij (x,y) is a power series of x and y, A ij Let A be the coefficient of each term in the polynomial, representing the coefficient of the i-th term of the phase distribution polynomial for wavelength j, with values ranging from 1000 to A. 11 ≤1400,5100≤A 21 ≤5600, 5≤A 31 ≤25,5≤A 41 ≤25,3365≤A 51 ≤3385, -250≤A 61 ≤-235,-375≤A 71 ≤-350, 1≤A 81 ≤25,600≤A 12 ≤1000,1500≤A 22 ≤1850, -50≤A 32 ≤-30, 10≤A 42 ≤20,2155≤A 52 ≤2170, -170≤A 62 ≤-155,-255≤A 72 ≤-235,5≤A 82 ≤15,400≤A 13 ≤650, -100≤A 23 ≤-20,-70≤A 33 ≤-55,4≤A 43 ≤12,1561≤A 53 ≤1574, -125≤A 63 ≤-113,-200≤A 73 ≤-180, 1≤A 83 ≤7.
2. The superlens beam-splitting imaging system according to claim 1, characterized in that: The system's material-space numerical aperture NA is 0.12 ≤ NA ≤ 0.
16.
3. The superlens beam-splitting imaging system according to claim 1, characterized in that: The system's cylinder length L is 58 ≤ L ≤ 62 mm.