摘要
针对天文观测和深空探测需求,提出了星载10 m合成孔径相干成像望远镜概念和形式。给出了波长可调谐激光本振相干探测器形式,分析了大口径衍射薄膜镜的双波段实现方式和系统主要参数。提出了基于子镜结构的光学合成孔径相干成像算法,给出了基于相位恢复的阵列形变误差波前估计仿真结果,由于多个子镜所接收复信号的成像处理在计算机软件中完成,相比传统望远镜,可降低对微调机构等硬件的精度要求。该望远镜在短波红外1.45~1.65μm光谱范围内的中心波长角分辨率为0.15μrad;在中波红外4.55~4.75μm光谱范围内的中心波长角分辨率为0.46μrad,其探测灵敏度在原理上是传统10 m口径望远镜的约2.8倍。
Spaceborne large-aperture infrared optical telescopes are of great significance for astronomical observation and deep space exploration.At present,large-aperture telescopes based on optical synthetic aperture systems are mainly divided into two categories:segmented imaging and interferometric imaging.The segmented telescope obtains the imaging resolution corresponding to the large aperture by splicing multiple small aperture telescopes,and the interferometric telescope achieves the imaging resolution of the aperture corresponding to the baseline length by interferometric processing(cross-correlation)of the signals of two or more small aperture telescopes.Against this background,the telescope in this paper draws on the Fizeau structure,the concept of a spaceborne 10 m synthetic aperture coherent imaging telescope is proposed,which is based on wavelength-tunable laser local oscillator coherent detection and diffractive thin film mirrors.By setting a wavelength-tunable laser local oscillator infrared coherent detector,a low-resolution complex image signal with phase information received by multiple sub-mirrors is sampled firstly,and then a high-resolution images are coherently synthesized in the computer.This imaging method can be defined as optical synthetic aperture coherent imaging.In addition,the optical synthetic aperture imaging processing in this paper is completed on the narrow-band subdivision spectral image signal corresponding to the infrared central wavelength,gating without aliasing of broadband infrared signals in the electronic frequency domain can be realized by adjusting the stepping wavelength of the laser local oscillator,which is equivalent to achieve subdivided infrared spectrum.In this paper,the mixing method of laser local oscillator signal and infrared signal refers to spatial optical path mixing.After spatial superposition of the chromatic aberration-corrected infrared complex image based on the polarization beam splitter and the wavelengthtunable laser local oscillator signal,it enters the array detector to realize photoelectric conversion and simultaneous frequency mixing,and outputs the complex image through narrow-band filtering AD sampling.The form of wavelength tunable laser local oscillator coherent detector is given and the dual band realization method of large aperture diffractive film mirror and main parameters of the system are analyzed.An optical synthetic aperture coherent imaging algorithm based on the sub-mirror structure is proposed and simulation results of array deformation error wavefront estimation based on phase retrieval is given.The telescope in this paper has an angular resolution of 0.15μrad in short-wave infrared 1.45~1.65μm spectral range;it has an angular resolution of 0.46μrad in mid-wave infrared 4.55~4.75μm spectral range,with a detection sensitivity 2.7 times higher than that of a traditional 10 m telescope in theory.And through the optical synthetic aperture processing,when the received infrared center wavelength is 1.55μm,the angular resolution of the telescope array in this paper is 16 times higher than that of the single sub-mirror image pixel angular resolution of 3.2μrad,so its pixel angular resolution is 0.2μrad,which is close to the 10 m aperture telescope’s diffraction limited angular resolution.Compared with the traditional large-aperture optical telescope,the imaging processing of the telescope in this paper is completed on the computer,and the size and weight of the system can be greatly reduced,with good detection performance.Since the imaging processing of complex signals received by the multiple sub-mirrors is completed by software in the computer,compared with the traditional telescope,the accuracy requirements for the fine-tuning mechanism and other hardware can be reduced.When the phase recovery technology of the existing indirect wavefront detection method is adopted,the mechanical control accuracy can be reduced from the order of one-twentieth wavelength to the order of wavelength,and the technical implementation is feasible.
作者
吴疆
李道京
崔岸婧
高敬涵
周凯
WU Jiang;LI Daojing;CUI Anjing;GAO Jinghan;ZHOU Kai(National Key Laboratory of Microwave Imaging Technology,Aerospace Information Research Institute,Chinese Academy of Sciences,Beijing 100190,China;School of Electronic,Electrical and Communication Engineering,University of Chinese Academy of Sciences,Beijing 100049,China)
出处
《光子学报》
EI
CAS
CSCD
北大核心
2023年第1期13-26,共14页
Acta Photonica Sinica
基金
中科院重点部署项目(No.E03701010F)。
关键词
光学合成孔径
相干成像
波前估计
衍射光学系统
红外光谱
天文观测
Optical synthetic aperture
Coherent imaging
wavefront estimation
Diffractive optical system
Infrared spectrum
Astronomical observation
