被动综合孔径成像中的光学处理技术

Optical Processing of Passive Synthetic Aperture Imaging

综合孔径技术已被广泛应用于被动式毫米波成像。由于成像系统的电路需要对天线收到的电信号进行长时间的处理以得到足够多的数据来重建图像,因此成像速度慢是这种方法的主要限制。通过电光幅度调制技术把毫米波调制到激光载波上,带有图像信息的光信号通过光纤传输后再经过透镜可以直接成像。本文从原理上比较了新的电光成像系统和原系统的异同,对于提出的新系统,采用10GHz的微波调制信号,载波波长为1550nm的激光进行一维点源成像仿真。成像结果说明了新的电光系统可以得到含有源辐射强度和方向信息的图像,但由于光纤间距远大于光波长,图像的角度范围大大缩小。仿真结果说明新的成像系统可以快速成像,并且通过增加孔径个数可以提高图像的分辨率。

Synthetic sperture has been widely used for passive millimeter-wave imaging. In order to get enough data to recover an image, it would take a long time for the circuit in an imaging system to process the information received by its antenna. So, this traditional imaging method has a disadvantage of low speed. If the millimeter-wave is modulated to a laser carrier by using an electro-optical amplitude modulation technique, the optical signal containing the image information can be transmitted via an optical fiber to a lens and is imaged directly. In this paper, the new and traditional electro-optical imaging systems are compared with each other in principle. The new system proposed is simulated in the form of one-dimensional point source imaging with the 10GHz modulated microwave signal and the laser with the wavelength of 1550nm. The imaging result shows that the new electro-optical system can obtain the image containing such information as the radiation intensity and direction of a point source. However, because the fiber spacing is much larger than the optical wavelength, the image angle spread is reduced greatly. The simulation result shows that the new imaging system can get an image at a high speed and its image resolution can be improved by increasing apertures of the system.