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0 前言 通常熟知的X射线焦点尺寸的测试方法有两种,即直接透照法(针孔成象法和狭缝成象法)和分辨力法(栅网法和星图法)。一般多采用前一种直接透照法,实验器具用针孔暗箱,得到的影象尺寸用目视测定,并作为焦点尺寸表示出来。但是,这里所得到的针孔象实际上给出的是射线管靶上的电子分布显示,与X射线底片所要求的分辨力关系不大。另外,如众所周知,第一种方法包括狭缝成象法,对测试器具的形状、尺寸及其透照布置有严,格的附加条件,很难说是一种简单、直观、一般易于测定的方法。 分辨力法虽符合射线透照目的,但其测定器具是网格或晶格,不易搞到手,而且因为是目测,测出的焦点尺寸缺乏客观性。 采用金属丝作测试器具,则可拍摄出焦点的半影,并依此宽度求出焦点的尺寸。这种方法的优点是对常规焦点和微焦点都能适用。缺点是因半影
0 Preface There are two commonly used methods for measuring X-ray focal spot size, direct transillumination (pinhole imaging and slit imaging) and resolution (grid and star charts). Generally use the former direct transillumination method, experimental apparatus with pinhole dark box, the image size obtained by visual determination, and expressed as the focal size. However, the pinhole image obtained here actually shows the distribution of electrons on the tube target, which has little to do with the resolution required for X-ray films. In addition, as is well-known, the first method includes the slit imaging method. It is hard to say that it is a simple, intuitive and generally easy-to-measure method for determining the shape, size, . Although the resolution method in line with the purpose of radiographs, but its measuring apparatus is a grid or lattice, easy to get the hand, and because it is visually, the lack of objectivity measured focus size. The use of metal wire as a test instrument, you can shoot the penumbra focus, and based on this width to find the size of the focus. The advantage of this method is that it can be applied to both normal focus and micro-focus. Drawback is due to penumbra