论文部分内容阅读
1.目前在线性不变的电子光学成象系统(例如各种象管)中,传递函数被普遍承认为象质评价的标准;在电镜中,引进相干传递函数的概念,考虑了影响成象的各种因素,找到等效的相干传递函数,再作逆滤波,这就是电子光学数字图象处理。FFT是数字图象处理中一种有效的算法。 2.电子光学传递函数为点扩展函数的二维傅里叶变换。其优点是把图象处理中繁冗的卷积运算变换为频域中的乘除运算。本文以高斯型点扩展函数为例,求其二维FFT,得到了32个灰度等级的传递函数点染图和MTF曲线。与解析公式相比较,差别小于0.01％。 3.在明场显微术中,物面波经—低通滤波器(物镜光阑)失掉高频信息,因而存在一个衍射极限分辨率。设想物样上有一直径20A的微孔(圆域函数),则在物镜后焦面上形成
1. At present, the transfer function is universally accepted as the criterion for the evaluation of mass in linearly invariant electro-optical imaging systems (such as various image tubes). In electron microscope, the concept of coherent transfer function is introduced to consider the influence of imaging Of the various factors, find the equivalent coherent transfer function, and then for the inverse filter, which is electronic optics digital image processing. FFT is an effective algorithm in digital image processing. 2. The electron optical transfer function is a two-dimensional Fourier transform of the point spread function. The advantage of this is that the convoluted convolution operation in the image processing is transformed into the multiplication and division operation in the frequency domain. In this paper, the Gaussian point spread function is taken as an example to find its two-dimensional FFT, and the transfer function point-spread and MTF curve of 32 gray levels are obtained. Compared with the analytical formula, the difference is less than 0.01%. 3. In bright field microscopy, the surface wave passes through a low-pass filter (the objective aperture) to lose high-frequency information, so there is a diffraction limit resolution. Imagine the sample has a diameter of 20A micro-hole (circular domain function), then the focal plane of the lens to form