在惯性约束聚变实验的过程诊断研究中,采用环形编码孔径成像技术可以同时获得高的空间分辨力和时间分辨力。获得高的空间分辨力的关键之一是如何准确地获得目标的点扩展函数。通常采用直接投影法。但这种方法忽略了X射线的衍射效应,因此限制了分辨力的提高。依据光的标量衍射理论,考虑X射线的衍射效应,导出了环形编码孔径的点扩展函数。并在此基础上制作了维纳滤波器。在激光等离子体重点实验室,用内直径为250 μm,外直径为260 μm的环形孔径板,对惯性约束聚变(ICF)的过程进行成像实验,得到了靶标的编码图像。采用以衍射为基础的维钠滤波器进行重构,获得的重构图像明显的优于用直接投影法得到的结果。

In the processing diagnosis of the inertiat confinement fusion (ICF), the ring coded aperture imaging technique is applied to gain high-space and time resolutions simultaneously. The key of acquiring high-spatial resolution is to obtain the point spread function of the imaging system correctly. The common method, firsthand projection method, neglects the X-ray diffraction effect, so the resolution of reconstructed image is decreased. Considering the X-ray diffraction effect the point spread function (PSF) of the ring coded aperture is derived from the scalar diffraction theory. And the Wiener filter is fabricated on the basis of the PSF. In National Key Laboratory of Laser Fusion, the imaging experiment on the diagnosis of ICF is completed using a ring coded aperture plate with inner diameter d1=250 μm and outer diameter d2=260 μm. The obtained coded image is processed by the Wiener filter where the diffractive effect is considered. The acquired reconstructive image by author's method is better than the image by the firsthand projection method.