Design and Imaging of Multi-frequency Interference System Based on T-lens Arrangement
The angular resolution of conventional optical systems is limited by the size of the system aperture,and high resolution implies a larger system aperture.However,the increase of system aperture will make the volume,weight and power consumption of the whole system increase dramatically,which greatly increases the difficulty of engineering realization.Photonic integrated interferometric imaging technology is a new type of highly integrated detection technology that combines optical interferometric imaging principle and photonic integration technology,which utilizes a photonic integrated chip to replace the sensors in traditional imaging,significantly reducing the volume,weight,and power consumption of the imaging system.However,at present,this technology is still in the stage of theoretical and simulation calculation research,and the research of related experimental imaging system is relatively small,and the existing interferometric imaging system can only collect the spatial frequency of the target point by point.In order to investigate the effect of multi-frequency point sampling on photonic integrated interference technology,this paper proposes and builds a multi-frequency interference imaging system with T-shaped lens arrangement.The system selects laser as the illumination light source.The light from the laser is irradiated to the 2D grating after passing through the fiber collimator.The multi-level diffracted light through the grating is split into multiple paths and incident to the rear fiber collimator.The fiber collimator is used instead of a lens array.The lenses are divided into two groups,S group horizontally and R group vertically,and the T-distributed lens array allows for frequency acquisition of baselines in multiple directions and at different lengths.After the lens array through the optical switch to control the on-off optical path,optical switch on time signal through the optical fiber into the fiber coupler for interference.The detector is used to capture the interference signal and then the spatial frequency information of the target is solved,and the target image can be obtained by doing the inverse Fourier transform of the spectral map.We first simulate the imaging process of the system,the center wavelength of the illumination light source is set to 1 550 nm,the distance from the target to the light source is 1 m,and the orthogonal two-dimensional grating with the spatial frequencies of 80 lp/mm and 40 lp/mm in the transverse and longitudinal directions is selected as the target for the simulation,and the minimum sampling frequency of the system is 40 mm-1.In order to distinguish the target,a pair of black and white stripes of 80 lp/mm is at least 40 mm-1.In order to distinguish the target,a pair of black and white stripes of 80 lp/mm is at least 2 pixels,and the size of the received image is set to 576×576.In order to have a certain degree of redundancy,the size of the spectral image received by the lens is set to 1 152×1 152 in the simulation,corresponding to the highest frequency of 160 lp/mm,which can satisfy the demand for target detection.The actual imaging system is built under the same conditions as the simulation to image the target.After calculation,the Peak Signal to Noise Ratio(PSNR)of the simulated image is 30.79 dB,and the PSNR of the experimental reconstructed image is 27.95 dB,and the overall structure of the reconstructed image has not been changed,so the experiment successfully realizes the reconstruction of the target image.Of course,in the process of the experiment,we also found some problems in the system,such as the lack of spectrum acquisition,the influence of the external environment and other problems,to be further researched and solved.Overall,photon integrated interferometric imaging is a technology with practical value,and the design of the imaging system and the process of system imaging proposed in this paper provide guidance and direction for the practical engineering application of this technology.
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