Illumination optical system for metasurface

Abstract

The invention relates to the technical field of non-imaging optical design, in particular to an illumination optical system for a metasurface, and the illumination optical system comprises a halogen lamp bead, an ellipsoidal reflector, an integral square rod and a relay lens group which are sequentially arranged; the halogen lamp bead emits wide-spectrum light covering a visible-near infrared band; wide-spectrum light is converged through the ellipsoidal reflector and coupled to the integral square rod for light field homogenization and square shaping, and then beam shrinkage is completed through the relay lens group. The edge light angle and the light spot uniformity are synchronously controlled; outputting a rectangular light spot; the invention provides an illumination optical system scheme specially designed for a metasurface, and solves the problem of low sensing signal-to-noise ratio caused by light spot shape mismatch and out-of-control incident angle in a general illumination scheme. The system breaks through the limitation of a general illumination optical system, the output characteristics of the system completely meet the requirements of a metasurface experiment performance test, and the system is suitable for the development of a portable sensing instrument with a metasurface as a core.

Description

Technical Field

[0001] This invention belongs to the field of non-imaging optical design technology, and particularly relates to an illumination optical system for metasurfaces. Background Technology

[0002] Artificial two-dimensional metamaterials, or metasurfaces, as subwavelength artificial structure platforms, have become a key research direction in this field due to their advantages in miniaturization integration, optical field manipulation efficiency, and high-sensitivity sensing. The electromagnetic modes they support, such as Fano resonance and continuous-domain bound states (BIC), can generate extremely high quality factors (Q values) and significant local field enhancements, which are the core pathways to achieving ultra-high sensitivity refractive index sensing and have important implications for industry, agriculture, medical diagnostics, and scientific research.

[0003] In metasurface performance testing and practical application detection, the design of the illumination optics system is crucial for achieving ultra-high sensitivity and high signal-to-noise ratio detection. Metasurfaces are typically composed of periodically arranged micro / nano structural units, and their overall optical performance is a macroscopic manifestation of the amplitude and phase modulation of light waves by numerous microstructural units. Non-uniform illumination will lead to inconsistent excitation responses in different regions of the metasurface, introducing measurement errors; therefore, a highly uniform illumination spot must be provided. Secondly, since the detection uses a spectrometer as the detection device to obtain the transmission spectrum, the illumination source must provide a continuous spectrum covering the entire detection band. Furthermore, to excite and maintain specific electromagnetic resonance modes in the metasurface (i.e., magnetic dipole contribution is dominant), the incident light angle should be limited within a certain range to ensure an extremely narrow linewidth of the resonance peak. Finally, given that the maximum single exposure write field of the electron beam exposure equipment currently used for processing metasurface chips is 1mm × 1mm, to balance large-scale yield production and testing accuracy, the metasurface chip packaging size is 1mm. 2 To achieve full-aperture, vignetting-free coverage of the area within the square, and to allow for necessary alignment tolerances to suppress edge effects, the optical extension of the lighting system must be precisely matched to this square.

[0004] In existing research, scholars have proposed various schemes for metasurface illumination, but all have obvious limitations. For example, integrating the refractive index sensing metasurface with an optofluidic device and using single-wavelength illumination can achieve the detection of specific beam patterns, but it does not involve beam spot homogenization design, making it difficult to ensure uniform excitation of large-area metasurfaces. Building a broadband light test optical path and focusing the beam through a combination of aperture and objective lens does not control the edge light angle, which may disrupt the stability of the Fano resonance. Directly using the Olympus BX53 microscope illumination system simplifies the optical path, but the microscope is large, has low integration, and is not conducive to the development of portable detection instruments. Schemes that simply optimize the light source (using a continuous spectrum laser such as 800-1650nm) or collimating element (such as an aspherical collimating lens) generally do not specifically address beam spot shaping and homogenization mechanisms, and cannot solve the problem of "beam spot mismatch with the metasurface sensing area". Summary of the Invention

[0005] In view of this, the present invention provides an illumination optical system solution specifically designed for metasurfaces, which solves the problem of low sensing signal-to-noise ratio caused by mismatch in spot shape and uncontrolled incident angle in general illumination optical systems; it breaks through the limitations of general illumination optical systems, and its output characteristics fully meet the requirements of metasurface experimental performance testing, and is suitable for the development of portable sensing instruments based on metasurfaces.

[0006] To achieve the above objectives, the technical solution created by this invention is implemented as follows:

[0007] This invention provides an illumination optical system for metasurfaces, comprising a halogen lamp, an ellipsoidal mirror, an integrating rod, and a relay lens group. The halogen lamp emits broadband light covering the visible-near-infrared band. The broadband light is converged by the ellipsoidal mirror and coupled to the integrating rod for light field homogenization and square shaping. The relay lens group then performs beam contraction and controls the edge ray angle and spot uniformity. Finally, the light spot is output.

[0008] Furthermore, the edge light angle controlled by the relay lens group is ±10.21°; the light spot uniformity is not less than 95%; and the light spot is a rectangular light spot.

[0009] Furthermore, the major axis of the ellipsoidal reflector is 77.5 mm, the minor axis of the ellipsoidal reflector is 45.83 mm, the half focal length of the ellipsoidal reflector is 62.5 mm, the front opening diameter of the ellipsoidal reflector is 12 mm, and the rear opening diameter of the ellipsoidal reflector is 63.38 mm.

[0010] Furthermore, the integral bar is a square bar with a cross-sectional dimension of 2mm.

[0011] Furthermore, a 0.6x beam reduction is achieved through the relay lens group.

[0012] Furthermore, the relay lens group includes a first lens, a second lens, a third lens, and a fourth lens arranged sequentially; the front surface of the first lens is the surface away from the second lens, and the front surface of the first lens is a plane; the second lens and the third lens are combined to form a cemented doublet lens group; the front surface of the third lens is the surface that is combined with the second lens, and the rear surface of the third lens is a plane.

[0013] Furthermore, the object distance of the relay lens group is 35.95 mm, and the effective focal length of the relay lens group is 22.98 mm.

[0014] Furthermore, the object-side aperture angle of the relay lens group is 6.57°, the outgoing ray angle of the relay lens group is controlled within 10.21°, and the back cutoff of the relay lens group is 14.98mm.

[0015] Furthermore, the radius of curvature of the front surface of the first lens is infinite, and the radius of curvature of the rear surface of the first lens is -16.471 mm; the radius of curvature of the second lens is 91.556 mm; the radius of curvature of the front surface of the third lens is -8.347 mm, and the radius of curvature of the rear surface of the third lens is infinite; the radius of curvature of the front surface of the fourth lens is 20.619 mm, and the radius of curvature of the rear surface of the fourth lens is -23.583 mm.

[0016] Furthermore, the thickness of the first lens is 2.618 mm, and the distance between the first lens and the integrating square bar is 37.08 mm; the distance between the first lens and the second lens is 0.5 mm; the thickness of the second lens is 3.304 mm; the thickness of the third lens is 2.48 mm, and the distance between the third lens and the fourth lens is 18.015 mm; the thickness of the fourth lens is 2.584 mm, and the distance between the fourth lens and the image plane is 15 mm.

[0017] Furthermore, the material of the first lens is H-LAF2, the material of the second lens is HZLAF68C, the material of the third lens is H-ZLAF90, and the material of the fourth lens is H-QK1.

[0018] Compared with the prior art, the present invention can achieve the following beneficial effects: 1. Design of a standardized illumination scheme that integrates theory, devices, and systems: In view of the fact that existing research mostly relies on general optical devices (such as microscope illumination, ordinary collimating lenses) or single module optimization (such as only focusing on light spot homogenization), and has not formed a "full-link customized" illumination optical system for metasurface sensing, a standardized metasurface illumination platform is designed by constructing an ellipsoidal reflector, an integrating rod, and a relay lens group. 2. A parameter optimization strategy that balances performance and engineering practicality, overcoming the contradiction of "performance-cost-integration": In the field of optical design, high uniformity illumination often relies on customized devices, resulting in high costs and difficult integration; while low-cost commercial devices are prone to performance compromises. The illumination optical system designed in this invention finds a balance between escape efficiency and energy utilization by optimizing the ellipsoidal reflector shape based on MATLAB numerical simulation, prioritizing the use of commercial devices, and designing details such as aperture blocking and double cemented lens integration, thereby reducing costs and processing difficulty, and providing a feasible path for the engineering implementation of metasurface illumination optical systems.

[0019] 3. Targeted solutions address the "special needs" of metasurface lighting, overcoming the limitations of general lighting solutions: Metasurface sensing requires significantly different "angle sensitivity" and "area matching" to illumination compared to general lighting (such as displays and imaging). For example, the Fano resonant metasurface maintains its magnetic dipole-dominated characteristics only within a ±11° incident angle, and 1mm... 2 The chip needs precise coverage and no edge distortion. Specifically, the illumination optical system designed in this invention achieves a targeted breakthrough: through optical optimization of a relay lens group with a special structure, the edge light angle is strictly controlled within 10.21° (<±11°) to avoid resonance peak shift; the light spot is designed to be 1.2mm. 2 The square shape (with a 0.1mm alignment tolerance) perfectly matches the chip package size, solving the problem of low signal-to-noise ratio caused by "mismatch in light spot shape and uncontrolled angle" in general lighting. At the same time, for the broadband sensing requirements of metasurface, a broadband light source emitted by halogen lamp beads is selected to adapt to the refractive index detection band, breaking through the application limitations of single-wavelength lighting. Attached Figure Description

[0020] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments and descriptions of the invention are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings: Figure 1 This is a schematic diagram of the overall optical path principle of the lighting optical system in a specific embodiment of the present invention; Figure 2 This is a schematic diagram of the analytical model of the ellipsoidal reflector in a specific embodiment of the present invention; Figure 3 This is a schematic diagram illustrating the relationship between escape efficiency and light flux at the receiving surface and f2 in a specific embodiment of the present invention; Figure 4 This is a schematic diagram of a three-dimensional model of an ellipsoidal reflector in a specific embodiment of the present invention; Figure 5 This is a schematic diagram of ray tracing of an ellipsoidal reflector in a specific embodiment of the present invention; Figure 6 This is an illuminance diagram of the converging light spot of the ellipsoidal reflector in a specific embodiment of the present invention; Figure 7 This is a schematic diagram of the three-dimensional energy distribution of the illuminance of the converged light spot by the ellipsoidal reflector in a specific embodiment of the present invention; Figure 8 This is a schematic diagram illustrating the relationship between the length of the integral square bar and the uniformity of the light spot illuminance in a specific embodiment of the present invention; Figure 9 This is an illuminance diagram of the emitted light spot of the integral square rod in a specific embodiment of the present invention; Figure 10 This is a schematic diagram of the three-dimensional energy distribution of the emitted light spot of the integral square rod in a specific embodiment of the present invention; Figure 11 This is a schematic diagram of the relay lens group in a specific embodiment of the present invention; Figure 12 This is an illuminance diagram of the emitted light spot of the relay lens group in a specific embodiment of the present invention; Figure 13 This is a schematic diagram of the three-dimensional energy distribution of the emitted light spot illumination of the relay lens group in a specific embodiment of the present invention; Figure 14 This is a ray tracing diagram of the illumination optical system in a specific embodiment of the present invention; Figure 15 This is an illuminance diagram of the emitted light spot of the illumination optical system in a specific embodiment of the present invention; Figure 16 This is a schematic diagram of the three-dimensional energy distribution of the emitted light spot illuminance of the illumination optical system in a specific embodiment of the present invention; Figure 17 This is a graph showing the variation of the light source axial tolerance, uniformity, and luminous flux in a specific embodiment of the present invention. Figure 18 This is a graph showing the variation curves of radial tolerance, uniformity, and luminous flux of the light source in a specific embodiment of the present invention. Figure 19 This is a combined tolerance analysis diagram in a specific embodiment of the present invention.

[0021] Figure label: 1. Illumination optical system; 11. Ellipsoidal reflector; 12. Halogen lamp bead; 13. Integrating square rod; 14. Relay mirror group; 2. Microchannel-metasurface chip; 3. Detection optical path; 31. Fiber optic coupling lens; 32. Spectrometer. Detailed Implementation

[0022] 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 specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and do not constitute a limitation thereof.

[0023] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0024] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on this invention. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, features defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0025] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art will understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0026] like Figure 1The diagram shows the overall optical path principle of the illumination optical system for metasurfaces provided in a specific embodiment of the present invention. As can be seen from the diagram, the high-uniformity illumination optical system 1 for metasurfaces provided in this embodiment includes a halogen lamp 12, an ellipsoidal mirror 11, an integrating rod 13, and a relay lens group 14. The integrating rod 13 is located in the object space, and the microchannel-metasurface chip 2 is located in the image space. Its core workflow revolves around "efficient utilization of luminous flux - uniform shaping of light spot - precise beam matching." Specifically, the broadband light emitted by the halogen lamp 12, covering the visible-near-infrared band, is first converged by the ellipsoidal mirror 11 to reduce luminous flux escape; it is then coupled to the integrating rod 13 for light field homogenization and square shaping, solving the problem of non-uniformity of the converged light spot; then, the relay lens group 14 performs 0.6x beam reduction to match the size of the metasurface chip; simultaneously, the relay lens group 14 controls the edge ray angle and light spot uniformity, ultimately outputting a light spot that meets the requirements, specifically a highly uniform rectangular light spot. During detection, the microchannel-metasurface chip 2 is placed on the focal plane of the relay lens group 14, and the liquid to be tested is injected in combination with the microfluidic mechanism. The error is reduced by multiple measurements. Specifically, the optical fiber coupling lens 31 in the detection optical path 3 is used for coupling, and the transmission spectrum is analyzed by the spectrometer 32 to achieve ultra-high sensitivity refractive index sensing.

[0027] In a specific implementation, the relay lens group 14 achieves 0.6x beam reduction, which allows for a better determination of the ratio between the output beam and the target beam, resulting in an output size of 1.2mm. A 1.2mm square light spot. Specifically, the ideal output light spot size is 1mm, the size of a conventionally fabricated metasurface chip. The input light spot is 1mm, originating from an integrating square rod, which has a designed cross-sectional dimension of 2mm. With a diameter of 2mm, a 0.6x beam reduction is achieved through the relay lens group 14. This takes into account the aberrations of light passing through the optical system, which will cause distortion at the edge of the light spot and a sharp decrease in uniformity. At the same time, it better facilitates the assembly and adjustment of the actual optical path and allows for tolerance.

[0028] In specific implementation methods, such as Figure 1As shown, in the overall optical path, the angle of the light rays emitted from the object space, i.e., the integrating square rod 13, is ±6.57°. Based on the object-image relationship and design results, after being controlled by the relay lens group 14, the angle of the edge light rays can be controlled within ±11°, specifically ±10.21°. Simultaneously, by controlling the uniformity of the light spot, the final output can achieve an illumination uniformity of no less than 95%, specifically an illumination uniformity better than 95.65%, better meeting the requirements of metasurface sensors for illumination spot uniformity. Since common circular light spots, when used for illuminating square metasurface chips, account for 63.66% of the inscribed square area, significantly reducing energy utilization, this invention, by combining current mainstream metasurface processing methods, outputs rectangular light spots, making it easier to draw patterns, facilitate exposure, and achieve processing, while also improving energy utilization. Simultaneously, it ensures that the shape and size of the output light spot match the processed metasurface sensor.

[0029] The illumination optical system provided in this invention is designed by reverse-engineering the parameters of each component based on the fundamental constraint of optical extension conservation. Specifically, it is based on the core requirements of the Fano resonant metasurface, including a refractive index detection range of 1–1.4 mm. 2 Based on package size, an 11° incident angle tolerance, and the common standard of >90% uniformity for high-performance optical systems, the optical performance targets of the system terminal are determined. Simultaneously, the calculated required optical extension for the system is 0.1647 mm. 2 •sr, thereby obtaining the key design parameters of the lighting optical system. In addition, in order to achieve the goal of "miniaturization, easy construction, and low cost" of the lighting optical system, the key design parameters take into account the convenience of processing and assembly, and prioritize the use of commercial standard components that meet the design parameters to reduce customization costs and development cycle.

[0030] In a specific embodiment, the illumination optical system 1 of the present invention uses halogen lamp beads 12 as the light source, whose spectral range covers the visible to near-infrared band, which can provide sufficient excitation power for the metasurface. At the same time, the radiation output fluctuates less with temperature, avoiding narrow-band interference from discrete spectral light sources and ensuring the stability of the sensing signal. Specifically, this part uses NARVA miniature halogen lamp beads, so that the illumination optical system 1 can take into account both wide spectrum continuity and light intensity stability.

[0031] Because halogen lamps emit light approximately like a Lambertian beam (resulting in significant energy dispersion), an ellipsoidal reflector is designed for secondary light distribution. A mathematical analysis model of the ellipsoid is constructed in a rectangular coordinate system, as follows: Figure 2As shown, this model diagram demonstrates the ability of the ellipsoidal reflector 11 to converge light rays and provides a visualization of its parameters. The ellipsoidal reflector 11 is a body of revolution, symmetrical about the x-axis; therefore, the analysis model only shows half of the ellipsoid. The ellipsoidal surface of the reflector 11 has two openings: a front opening (close to the origin of the Cartesian coordinate system) and a rear opening, with dimensions d / 2 and D / 2 respectively. H is the thickness of the ellipsoidal reflector. The halogen lamp bead 12, acting as the light source, is located at the first focus of the ellipsoid, at a distance f1 from the origin. Light rays converge at the second focus of the ellipsoidal reflector, defined as the receiving surface, which is f2 from the origin. Ma is the horizontal distance from the light source to the edge of the front opening. To determine the ellipsoidal surface parameters and the diameter of the front opening, the escape luminous flux emitted from the light source is analyzed, and the surface parameters are optimized based on the system length. A numerical calculation program based on MATLAB was written to dynamically adjust the major and minor axis dimensions of the ellipsoid and their ratio by changing the value of f2, under the condition that the focal length f1=15mm is fixed and the maximum edge angle is ≤±14.97° (coupled with the integral bar).

[0032] Further calculations are performed on the front opening size of the corresponding ellipsoidal reflector 11 and the angle between the front and rear openings relative to the first focal point. The luminous flux escape efficiency of this invention is defined as the proportion of luminous flux emitted by the light source that fails to be converged by the optical device and thus escapes from the optical system. Due to the different ellipsoidal parameters (using f2 as the abscissa), the proportion of the luminous flux escaping through the front and rear openings of the ellipsoidal reflector 11 is obtained through mathematical calculation. The calculated luminous flux escape efficiency is as follows: Figure 3 As shown in the figure, the light-gathering effect of the ellipsoidal reflector 11 can be seen, specifically the light source located at the first focal point of the ellipsoidal reflector. Specifically, as... Figure 3 As shown, this is a double y-plot. The left y-axis represents the escape efficiency, and the right y-axis represents the luminous flux coupled into the integrating square rod 13 after being converged by the ellipsoidal reflector 11. It can be seen from the figure that although increasing the major and minor axis dimensions can further improve the luminous flux, the gain gradually decreases with increasing proportion, and the later improvement effect is limited and negligible. Therefore, the optimal balance is finally achieved between the spot size, edge angle, and luminous flux efficiency. The parameters of the ellipsoidal reflector 11 are: major axis a = 77.5 mm, minor axis b = 45.83 mm, half focal length c = 62.5 mm, and front and rear aperture diameters of 12 mm and 63.38 mm, respectively. At this point, the system luminous flux escape rate is 55.43%, and the generated spot meets the coupling requirements of the integrating square rod 13. In a further preferred embodiment, to ensure that the system performance meets the requirements while taking into account actual processing and cost control, the TCEA-86C-14 / 134-SH20 ellipsoidal reflector from Sigma Optical Machinery Co., Ltd. can be used as the focusing element.

[0033] The three-dimensional model of the ellipsoidal reflector 11 constructed in a specific embodiment of the present invention is shown in the figure below. Figure 4 As shown, the ray tracing diagram of the ellipsoidal mirror 11 is as follows: Figure 5 As shown; the illuminance diagram of the converging light spot of the ellipsoidal reflector 11 is as follows. Figure 6 As shown, the schematic diagram of the three-dimensional energy distribution of the illuminance of the converging light spot of the ellipsoidal reflector 11 is as follows. Figure 7 As shown in the figures, these figures demonstrate the converging effect of the ellipsoidal reflector 11 from two-dimensional and three-dimensional perspectives, respectively. The light spot on the receiving surface has a Gaussian distribution, and the size of the light spot is approximately a circular spot with a diameter of 1 mm. That is, the light converges well after being distributed twice by the ellipsoidal reflector 11, forming an uneven light spot with a bright center and dark edges on the receiving surface.

[0034] In a specific implementation, to improve the uniformity of the light spot, a secondary optical device is designed to homogenize the light spot with an approximately Gaussian distribution. Specifically, a square integrating rod 13 is used as the homogenizing element of the system, which has the best comprehensive performance in terms of continuous spectrum homogenization ability, output uniformity, fabrication feasibility, and ability to generate square light spots. After analyzing the relationship between the angle of the emitted light from the integrating rod 13 and the side length of its cross section, it is found that the edge angle of the emitted light from the integrating rod 13 is negatively correlated with its side length: the larger the side length of the cross section, the smaller the edge angle of the emitted light. At the same time, the relationship between the length of the integrating rod 13 and the uniformity of the light spot illuminance is as follows: Figure 8 As shown, the uniformity of light spot energy γ (see the formula below) combined with the ratio of standard deviation to mean illuminance is used as an evaluation index to assess the homogenization effect of the integral square bar 13.

[0035] ; The above formula is the formula for evaluating the uniformity of light spot energy, where m is the number of sampling points, and E... i The illuminance value at each sampling point, This represents the average illuminance of energy at all sampling points within the light spot area. In the simulation, the light spot was divided into 41... The illuminance value of each of the 41 grids is read and used to calculate the energy uniformity of the light spot using a formula.

[0036] In the illumination optical system design of this invention, the cross-sectional dimensions of the integrating rod 13 are controlled to prevent excessive increase in its optical extension, which could lead to light energy loss. Simultaneously, while increasing the length of the integrating rod 13 can improve the uniformity of the light spot, according to... Figure 8The uniformity trend shown indicates that the improvement effect on uniformity tends to plateau once the length exceeds a certain threshold. Therefore, excessively long square bars, while offering limited uniformity benefits, increase system volume, hindering miniaturization and compact layout. In a preferred embodiment, the integral square bar 13 can specifically be a square bar with a cross-sectional dimension of 2mm and a theoretical length L of 42.3mm; in practice, an integral square bar with a length of 50mm from Edmund Optics can be used.

[0037] In a specific implementation, LightTools was used to simulate 20 million ray tracing lines. Figure 9 The illuminance diagram of the emitted light spot from the integral square rod is shown. Figure 10 The two figures show a schematic diagram of the three-dimensional energy distribution of the emitted light spot illuminance of the integral square rod. As can be seen from the figures, after homogenization by the integral square rod 13, the uniformity of the light spot in the illumination optical system provided by the specific embodiment of the present invention is higher than 95%, which meets the design requirements of this part.

[0038] To address the issues of low light energy utilization and high scattering background noise caused by geometric mismatch of light spots during direct coupling, the illumination optical system provided in this invention introduces a relay lens group 14 as a beam control link. This relay lens group 14 performs proportional geometric scaling on the light spot output by the integrating rod 13, so that the light spot accurately covers the entire receiving surface of the metasurface chip, thereby significantly improving light energy utilization efficiency, effectively suppressing background noise, and improving the system signal-to-noise ratio.

[0039] In a specific implementation, the initial design of the relay lens group in Zemax includes four independent lenses: a first lens, a second lens, a third lens, and a fourth lens. During the design optimization process, firstly, to improve image quality and facilitate system assembly and calibration, the second and third lenses are combined into a cemented doublet lens group. The front surface of the third lens is the surface that bonds with the second lens, and the rear surface of the third lens is the surface furthest from the second lens. The front surface of the first lens is the surface furthest from the second lens, and the rear surface of the first lens is the surface closest to the second lens. The front surface of the fourth lens is the surface closest to the third lens, and the rear surface of the fourth lens is the surface furthest from the third lens. To reduce manufacturing costs and difficulty, the front surface of the first lens and the rear surface of the third lens are set as planes, i.e., with an infinite radius of curvature. Simultaneously, the structural parameters of the remaining lenses are optimized to compensate for image quality issues. Finally, the structure of the relay lens group 14 used in this specific implementation is as follows: Figure 11As shown, the angle of the light rays emitted from the object space, i.e., the integrating square rod 13, is ±6.57°. Based on the object-image relationship and design results, it can be seen that after being controlled by the relay lens group 14, the angle of the edge light rays can be controlled within ±11°, specifically ±10.21°. Specifically, the relay lens group 14 has an object distance of 35.95mm, an effective focal length of 22.98mm, an object aperture angle of 6.57°, an emitted light ray angle controlled within 10.21°, and a back cutoff of 14.98mm.

[0040] In a specific implementation, the parameters of the four lenses included in the relay lens group 14 are shown in Table 1. The radius of curvature of the front surface of the first lens is infinite, and the radius of curvature of the rear surface of the first lens is -16.471 mm; the radius of curvature of the second lens is 91.556 mm; the radius of curvature of the front surface of the third lens is -8.347 mm, and the radius of curvature of the rear surface of the third lens is infinite; the radius of curvature of the front surface of the fourth lens is 20.619 mm, and the radius of curvature of the rear surface of the fourth lens is -23.583 mm. The first lens has a thickness of 2.618 mm, and the distance between the first lens and the integrating square rod 13 is 37.08 mm; the distance between the first lens and the second lens is 0.5 mm; the thickness of the second lens is 3.304 mm, the thickness of the third lens is 2.48 mm, and the distance between the second lens and the third lens is 0 mm, forming a cemented doublet lens; the distance between the third lens and the fourth lens is 18.015 mm; the thickness of the fourth lens is 2.584 mm, and the distance between the fourth lens and the image plane is 15 mm. The material of the first lens is H-LAF2, the material of the second lens is HZLAF68C, the material of the third lens is H-ZLAF90, and the material of the fourth lens is H-QK1. Through a special structural design, the relay lens group 14 proportionally and geometrically scales the light spot output by the integrating square rod 13, so that the light spot accurately covers the entire receiving surface of the metasurface chip, thereby significantly improving the light energy utilization efficiency and effectively suppressing background noise, and improving the system signal-to-noise ratio.

[0041] In a specific implementation, to verify the beam-shrinking effect and beam uniformity of the uniform light spot emitted by the relay lens group 14 to the integrating square rod 13, a 2mm×2mm rectangular Lambertian light source was set in the optical simulation software LightTools. The beam uniformity effect was evaluated by tracing 20 million rays. The simulated illuminance grating chart and illuminance line chart of the receiving surface showed that its illuminance across the entire field of view was greater than 99%, which met the design requirements.

[0042] Table 1 Parameters of each lens in the relay lens group

[0043] Specifically, Figure 12 This is the illuminance diagram of the output light spot of the relay lens group. Figure 13 The diagram shows the three-dimensional energy distribution of the illuminance of the emitted light spot after the relay lens group is homogenized and shaped by the integrating rod 13. The two diagrams are a two-dimensional diagram and a three-dimensional diagram of the illuminance of the emitted light spot after homogenization and shaping by the integrating rod 13. It can be seen from the diagram that the integrating rod 13, which adopts the parameters set by the specific embodiment of the present invention, achieves an illuminance uniformity of better than 95% after 20 million ray tracings in Lightools, thus verifying the performance of the integrating rod.

[0044] Further simulations demonstrate that the illumination optical system for metasurfaces provided by the above-described specific embodiments of the present invention is practical and effective.

[0045] Specifically, the illumination optical system designed in this invention was verified through simulation software using optical design software (Zemax) and ray tracing software (LightTools), such as... Figure 14 The figure shows the ray tracing diagram of the illumination optical system in a specific embodiment of the present invention. As can be seen from the figure, the total length of the illumination optical system is 264.5 mm. The performance of the overall illumination optical system is verified by ray tracing simulation.

[0046] The entire illumination optical system designed in the specific embodiments of this invention includes a light source section, a light homogenizing and shaping section, and a relay system section. A complete optical path model was established in LightTools optical simulation software for ray tracing and performance simulation. For example... Figure 15 The image shown is an illuminance diagram of the emitted light spot of the illumination optical system in a specific embodiment of the present invention; as shown... Figure 16 The figures show a schematic diagram of the three-dimensional energy distribution of the emitted light spot of the lighting optical system in a specific embodiment of the present invention. The two figures show the energy distribution effect of the emitted light spot of the overall lighting optical system provided by the present invention. Specifically, as can be seen from the figures, after the control of the optical components of the lighting optical system, the emitted light spot has reached a flat-topped light spot with high uniformity. At the same time, the shape of the light spot is a square with a side length of 1.2 mm. Most of the energy is concentrated in the effective area, and the illuminance uniformity reaches 95.65%.

[0047] The simulation results above all verify the feasibility of the illumination optical system scheme provided in the specific embodiments of the present invention. Through tracing simulations of 50 million rays, the effective illumination area formed by the system on the metasurface receiving surface achieves an illuminance uniformity of 95.65%, and the total system length is 264.5 mm. This fully demonstrates that the illumination optical system scheme proposed in the specific embodiments of the present invention meets the design requirements of metasurface sensing for high-uniformity illumination in all aspects.

[0048] Furthermore, in order to evaluate the manufacturability and assembly tolerance of the lighting optical system provided by the specific embodiments of the present invention, the relative positional tolerance between the halogen lamp 12 and the ellipsoidal reflector 11 was analyzed, with a focus on its impact on the uniformity of output illumination. Figure 17 The figure shows the curves of axial tolerance, uniformity, and luminous flux variation of the light source; as shown... Figure 18 The figure shows the curves of radial tolerance, uniformity, and luminous flux variation of the light source; as shown... Figure 19 The diagram shown is a composite tolerance analysis chart. Simulation analysis was performed to investigate the effects of filament axial and radial positional offsets on uniformity and luminous flux. Results show that when the axial tolerance of the filament position is <0.8 mm and the radial tolerance is <0.4 mm, the system uniformity remains above 90%, demonstrating its good assembly and adjustment tolerance. Currently, a combination of precision fine-tuning threaded pairs and symmetrically distributed compression springs has been applied, and the design of this filament adjustment mechanism has been completed using 3D-printed resin material, verifying the feasibility of constructing the lighting optical system in the specific embodiment of this invention.

[0049] This invention constructs a standardized lighting optical system design scheme that integrates theory, devices, and systems. Based on the requirements of metasurface lighting, it extracts and allocates system indicators, addressing the pain points of existing schemes such as isolated modules and poor adaptability. This achieves efficient and accurate collaboration from design theory to the final system. Specifically, the parameter optimization strategy employed simultaneously balances performance and engineering practicality in design and practice. It overcomes the limitations of relying on high-cost custom devices or being forced to accept performance compromises from commercial devices, achieving a key balance through multi-objective optimization, thus providing a reliable path for the engineering implementation of metasurface lighting systems.

[0050] This invention provides a solution for an illumination optical system specifically designed for metasurfaces. Compared with existing technologies, it solves the problem of low signal-to-noise ratio caused by mismatch in light spot shape and uncontrolled incident angle in general illumination solutions. The solution of this invention breaks through the limitations of general illumination optical systems, and its output characteristics fully meet the requirements for experimental performance testing of metasurfaces. It is also suitable for the development of portable sensing instruments based on metasurfaces.

[0051] It should be understood that the various forms of processes shown above can be used to reorder, add, or delete steps. For example, the steps described in this invention disclosure can be executed in parallel, sequentially, or in different orders, as long as the desired result of the technical solution disclosed in this invention can be achieved, and this is not limited herein.

[0052] The specific embodiments described above do not constitute a limitation on the scope of protection of this invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. An illumination optical system for metasurfaces, characterized in that: The illumination optical system for the metasurface includes halogen lamps, an ellipsoidal mirror, an integrating rod, and a relay lens group. The halogen lamp emits broadband light covering the visible-near infrared band; the broadband light is converged by the ellipsoidal reflector and coupled to the integrating square rod for light field homogenization and square shaping; then the beam is reduced by the relay lens group, and at the same time, the edge ray angle and spot uniformity of the broadband light are controlled by the relay lens group; and the light spot is output.

2. The illumination optical system for metasurfaces according to claim 1, characterized in that: The major axis of the ellipsoidal reflector is 77.5 mm, the minor axis is 45.83 mm, the half focal length is 62.5 mm, the front opening diameter is 12 mm, and the rear opening diameter is 63.38 mm.

3. The illumination optical system for metasurfaces according to claim 1, characterized in that: The edge ray angle controlled by the relay lens group is ±10.21°; the uniformity of the light spot is not less than 95%; and the light spot is a rectangular light spot.

4. The illumination optical system for metasurfaces according to claim 1, wherein the integrating rod is a square rod with a cross-sectional dimension of 2 mm; and 0.6x beam reduction is achieved through the relay lens group.

5. The illumination optical system for metasurfaces according to claim 1, characterized in that: The relay lens group includes a first lens, a second lens, a third lens, and a fourth lens arranged in sequence; the front surface of the first lens is the surface away from the second lens, and the front surface of the first lens is a plane; the second lens and the third lens are combined to form a cemented doublet lens group; the front surface of the third lens is the surface that is combined with the second lens, and the rear surface of the third lens is a plane.

6. The illumination optical system for metasurfaces according to claim 5, characterized in that: The object distance of the relay lens group is 35.95 mm, and the effective focal length of the relay lens group is 22.98 mm.

7. The illumination optical system for metasurfaces according to claim 5, characterized in that: The object-side aperture angle of the relay lens group is 6.57°, the exit ray angle of the relay lens group is controlled within 10.21°, and the back cutoff of the relay lens group is 14.98mm.

8. The illumination optical system for metasurfaces according to claim 5, characterized in that: The first lens has an infinite radius of curvature on its front surface and an infinite radius of curvature on its rear surface; the second lens has a radius of curvature of 91.556 mm; the third lens has an infinite radius of curvature on its front surface and an infinite radius of curvature on its rear surface; the fourth lens has a radius of curvature of 20.619 mm on its front surface and a radius of curvature of -23.583 mm on its rear surface.

9. The illumination optical system for metasurfaces according to claim 5, characterized in that: The thickness of the first lens is 2.618 mm, and the distance between the first lens and the integrating square bar is 37.08 mm; the distance between the first lens and the second lens is 0.5 mm; the thickness of the second lens is 3.304 mm; the thickness of the third lens is 2.48 mm, and the distance between the third lens and the fourth lens is 18.015 mm; the thickness of the fourth lens is 2.584 mm, and the distance between the fourth lens and the image plane is 15 mm.

10. The illumination optical system for metasurfaces according to claim 5, characterized in that: The first lens is made of H-LAF2, the second lens is made of HZLAF68C, the third lens is made of H-ZLAF90, and the fourth lens is made of H-QK1.

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