Study On The Technology Of Planar Hyperspectral Imaging Based On Metasurface

With the proliferation of smart devices,capturing and reproduction of the color,luster,and texture of real-world objects is demanded for high-resolution imaging applications.The hyperspectral imaging technology that integrates spectroscopy and imaging technology can simultaneously obtain two-dimensional spatial information and spectral information of an object,and is widely used in remote sensing,space exploration,art conservation,agriculture,and other scientific and industrial fields.However,the conventional hyperspectral imaging technology faces main barriers:the imaging system is cumbersome and thus is difficult to achieve planarization and integration.Due to its planar structure and sub-wavelength size,metasurfaces can flexibly modulate the optical characteristics of phase,amplitude,polarization of light.Therefore,it can be used in conventional hyperspectral imaging systems to achieve planarization and integration,and has greater application potential in Drones,satellites,mobile phones and other equipment.In view of the above problems,the main research contents of this article are as follows:1.The planar hyperspectral imaging technology based on two metasurfaces was researched,and the pushbroom hyperspectral imaging system was designed.The system can achieve a spectral resolution of 3.5 nm in 850 nm to 1000 nm band under a30°field of view(FOV).The evaluation function is applied to limit smile and keystone of the system,and smile and keystone are minimized as much as possible while ensuring the near diffraction-limited focusing.The corresponding values obtained by optimization are 124.4μm and 33.6μm,respectively.The estimated volume of the entire planar hyperspectral imaging system is only 45.5mm~3.According to the imaging requirements,the dispersive metasurface and the focusing metasurface based on the transmission phase modulation principle are designed in sequence,and the FOV and wavelength insensitivity of the unit cell are verified.The proposed spectral imaging camera has the advantage of light volume,small weight and easy integration,and is expected to be applied in the portable imaging field.2.The broadband planar hyperspectral imager with elimination of smile and keystone based on metasurfaces was designed.A dispersive metasurface and two focusing metasurfaces are coplanar with each other to achieve near-diffraction limit focusing by modulating light.The system works in 1000 nm to 1500 nm band under a5.4°FOV(corresponding to a spectral resolution of 5.5 nm-12 nm),and basically eliminates smile and keystone through the setting of the sequential merit function,which overcomes spectral distortion and provides highly consistent spectral data.The estimated volume of the entire system is only 27.2 mm~3.According to the phase matching mechanism,the dispersive metasurface and two focusing metasurfaces suitable for broadband are designed based on the geometric phase.In order to reduce the complexity of the process,the design of different metasurfaces needs to ensure the same thickness.In addition,the insensitivity to wavelength and FOV of the unit cell was verified,which proved that it met the imaging requirements.The designed system with broadband characteristics can obtain more spectral information and avoid the spectral aliasing effect to a certain extent.