Research On Photonic Crystal Array Based Hyperspectral Imaging Mechanism And Classification Method

Hyperspectral imaging and detection technology is a comprehensive technology integrating new detection method,precision optical machinery and high-speed signal processing technology,it has been widely used in the field of geology,oceanography,agriculture,atmospheric and environmental detection.The application of hyperspectral detection technology in food,medicine,medical and other industrial detection fields has great potential,it is urgent to break through the miniaturization and highspeed hyperspectral imaging technology to meet the needs of high-speed and high-precision visual detection in industrial production.The existing large-scale hyperspectral imaging equipment is bulky,expensive and slow,which limits its large-scale promotion,and the portable hyperspectral cameras need space scanning or spectrum scanning,the shooting time is too long.This paper studies the small snapshot hyperspectral imaging scheme based on photonic crystal array,which can provide very high-resolution spectral sampling and imaging capabilities,and is easy to manufacture,which is conducive to promoting the application of hyperspectral vision in the field of industrial detection.This thesis focuses on the research of hyperspectral vision perception system of the robot for industrial application.The challenges of hyperspectral detection technology for visual inspection are analyzed,because the spectral sensor in the conventional hyperspectral imaging device need a longer optical path to separate the light of adjacent wavelengths,the design of a long optical path in free space requires many precise optical elements,so the hyperspectral imaging equipment is always huge and expensive,which greatly limits the application of hyperspectral camera in the field of industrial detection.The complex surface structure of the photonic crystal can make the light reflect and refract repeatedly many times,and realize a long optical path in a small space size.The complex light response characteristics enable produce very rich spectral transmission characteristics,which can be combined with the compressive sensing technology to achieve hyperspectral imaging.Therefore,a small snapshot hyperspectral vision perception system based on photonic crystal is proposed,the main research contents include:1.The basic principle of spectral spectroscopy is analyzed,and a small snapshot hyperspectral imaging scheme using photonic crystal filters is proposed.The optical filter array is composed of photonic crystals with different structures,which downsampling or recoding the multi-band composite light,and the image sensor capture the spectral information of different spatial positions and different spectral bands at the same time,the spectral reconstruction component recovers the hyperspectral image of the target scene by using the captured data,the miniaturization and snapshot hyperspectral imaging is met.2.The structural characteristics of photonic crystal are analyzed,a spectrum sensor based on the photonic crystal filter array are designed.The spectral sensing scheme based on narrowband filtering and wideband filtering cooperate with compressive sensing are proposed,the feasibility of hyperspectral image sensing with photonic crystal is analyzed theoretically.And a spectrum sensing experiment are designed,which prove the photonic crystal sensor array can be used for the spectrum measurement and hyperspectral imaging by comparison with the commercial spectrometer.3.Two kinds of dielectric photonic crystal structures with periodic hole array are designed,and the transmission characteristics of photonic crystal are studied by FDTD and CMT methods.The optical reflection characteristics with a ring hole array structure and with a double-period hole array structure are studied.Due to the existence of the optical bound state,the array structure will produce a narrow-band reflection spectrum with high quality factor.By changing the structural parameters such as the inner and outer radius of ring hole,lattice constant and refractive index of the surrounding medium,the reflection characteristics of the photonic crystal influence by the structural parameters are studied.The quality factor of the two type of structures can achieve even more than 10~5.This narrow-band filter can be used to design the spectroscopic device of the hyperspectral imaging equipment.4.The transmission characteristics and modulation method of gold nanoarray structures are studied.The photonic crystals with gold nanowire dimer array,gold nanorod trimer array,metal/dielectric composite array structures are designed,the transmission mechanism of light in metal and dielectric structures are studied.The changes of the transmission spectrum with structural parameters are analyzed,and the basic principles that causes these changes are analyzed.The rule that the transmission curve of the metal nano array structure changes with the structural parameters is obtained.This kind of complex photonic crystal can produce a variety of optical transmission characteristics,and can be adjust and control by changing the structural parameters.The research can provide the theoretical basis for the design of new optical sensors.5.A spectrum sensing method based on the photonic crystal filters and the theory of compressive sensing is proposed,which can achieve a high spectral resolution in the case of small equipment size and low sampling times.The influence of the structure parameters of photonic crystal and the incident angle on the spectrum sensing performance is analyzed.The narrowband spectrum,the real scene spectrum,and the medical hyperspectral image are used as the input signal respectively to carry out the experiment.It is proved that the use of the optical response curve of the photonic crystal as the sensing matrix in the compressed sensing not only adds the luminous flux,but also greatly reduces the sampling times and realizes the accurate light Spectral reconstruction results.6.A new hyperspectral image classification method is proposed,which applied the common edge preservation filtering algorithm in the spectral domain.The method can keep the continuity of spectral curve and effectively integrate the spatial information into the spectral information.By adjusting the filter size,spatial spectral weight and the guidance image parameters and combining with SVM,MLR and RF classifier,the effects on the classification results are analyzed.and several real hyperspectral images are used for experiment,the results show that the spatial and spectral information are fused while the noise is removed,and our method always shows good performance in all tests.In this paper,we propose the hyperspectral imaging scheme by using photonic crystal filter and hyperspectral image classification algorithm.A small portable hyperspectral imaging system is designed,the optical transmission characteristics and regulation mechanism of several types of photonic crystals are studied,the hyperspectral image reconstruction theory using photonic crystal filter array is proposed,and the hyperspectral image classification algorithm is designed,which provides a solution from hyperspectral image sensing to hyperspectral image processing for visual inspection.Because nanostructured photonic crystal devices are easy to be integrated into microdevices,it can greatly improve the integration of hyperspectral imaging equipment,save production costs,benefit the miniaturization of hyperspectral cameras,in combination with hyperspectral image classification algorithm,it is beneficial to promote the further application of hyperspectral vision detection technology in the field of machine vision.