For decades in theNondestructive Testing (NDT) industry，薄膜一直是选择的射线照相成像方法。它的演化和行业竞争使电影融入了高质量的水平，许多选择几乎需要放射线照相。慢膜用于精细分辨率选项，同时更快的速度涵盖更大或更少的关键材料。今天，我们有许多新的竞争对手试图将替代电影作为行业王。其中许多选项共享一个结果：数字成像。
传统到数字图像的过渡是渐进的跳跃和界限。我们都是，可能是以一种形式呈现它，但最近的NDT行业变化已经在我们未来的许多业务计划中表现出数字。更好质量的预测随着更高的生产的承诺引发了服务提供商和制造商的利益。在我们理解我们反对的新技术之前，让我们了解真正的数字成像。
NDT的数字成像是什么？
If we were to take a digital technology and strip away the hands-on portion, we are left with Digital Imaging. Computed Radiography (CR), Digital Detector Arrays (DDA), Linear Diode Arrays (LDA), and other “Radiographic Techniques” result in digital imaging. The “Imaging Medium” is the receiver of the radiation dose which gives each modality its own “personality”.
虽然数字成像是对这些过程的常数，但由于实际应用，所产生的图像具有它们自己的特性。CR图像倾向于具有高分辨率，但也可以遭受噪音。DDA图像成反比，将倾向于具有较低的分辨率，但应在降噪时excel。替代应用也可能具有效果。
Signal, Noise and Radiography
检测技术在管道均nt noise level than CR on a steel casting. This brings me to our first two topics: signal and noise. Signal is the primary radiation beam transmitted to the imaging medium. Noise, however, is a combination of any extra energy reaching that same imaging medium. Light, scattered radiation, electronic noise, and haloing name just a few sources of noise. Any technique will have signal AND noise characteristics based on the properties of that equipment. Ideally, zero noise with 100% signal would be our target but, because noise is driven by signal and vice versa, that target is not only impractical, but impossible. All Radiography has noise regardless of our best intentions. A well-developed process should give an optimum signal to noise ratio, not eliminate it completely.
The Best Resolution for NDT Digital Imaging
我们应该理解的另一个因素，至少有一点点：解决方案。考虑电视市场作为我们的榜样。电视屏幕由构成图片的微小像素网格组成。一旦高清电视推出市场，我们就开始讨论了解决方案。720p，1080p，现在4k是我们将考虑总分辨率的全部分辨率，或一行或一个面板中的总像素。在1080p电视中，屏幕的垂直线路长度为1080像素。那些1920年的垂直线条，这意味着我们在面板中的分辨率为1920 x 1080，或20.7万像素。
If we considered a television with the exact same resolution, but a larger physical size, the pixels themselves would have to be larger. It still has 1080 pixels in each line with 1920 of those lines in the screen, but each pixel needs to cover more physical area to make up the larger screen size. This forces the industry to format in ‘pixel pitch’ rather than total pixels.
Pixel pitch describes the measurement from the center of one pixel to the center of the next, eliminating the total pixel count as our metric. That standardizes the resolution without an image size, making a simple resolution comparison of differently sized images. Pitch is measured in ‘microns’ or 1/1000 of a millimeter, and a common pixel pitch would be 50-200 microns. Ideally, you would want as many pixels as reasonably possible in an image. Too small of a pitch, however, will result in more noise, so the smallest isn’t always the best. A strong technician should know how to negotiate an acceptable resolution.
4096灰色阴影：确定放射线钻头深度
我们已经确定了像素在二维网格中布置，但尚未讨论如何填补它们。这是位深入游戏的地方。图像中的每个微小像素具有由数字表示的“灰度值”。该数字的电位范围，称为“动态范围”，取决于图像的比特深度。
一位是包含1或0的信息，该信息表示为“ON”或“OFF”。如果我们一起拍摄第二位并将两个串在一起，我们可以获得开/关位置，以及两者之间的两个。两个位（2位深度）可以表示00或11，但也可以是01或10.如果我们添加另一个位（3位深度），则选项可以为000,001,010,100,011,110，101或111.每次添加一点时，选项的数量都会加倍。
现在，让我们考虑从白色到黑色而不是开/关场馆的这些色调。我们也将在更高的比特深度讨论这一点。有点深度为12会给我们212.选项或4096灰色的灰色，而16位会给我们216.或65,536张灰色。一组所有零将导致没有曝光或白色，并且一组所有将导致完全饱和或黑色。介于两者之间的剩余选项是灰色的阴影。
If we were to radiograph a casting with many thickness changes, 16 bit would give us the range to put them all on one image. A weld with minimal thickness changes would be much better at 12 bit since the high range wouldn’t benefit that application. With a higher bit-depth comes a higher radiation exposure and a chance at more noise, the same as higher resolution. Many applications will see no benefit to the higher range so 12 bit is generally plenty. Radiography requiring great detail will likely need a 14-16 bit setting, regardless of the extra noise. It’s a determination the technician needs to make.
数字成像是NDT的未来
Clearly, there are many options and features built into digital images and this may be the most many of us will ever read about something as common as a picture. However, the simple truth is: digital imaging is our future and we need to prepare for it.
电影最终会过时，一盎司的预防值得一磅治疗。行业早期领先于曲线，我们客户将越来越多的时间越来越省。而且，正确培训NDT技术人员可以长途跋涉长期开发一个声音程序。
计算的射线照相网络研讨会
有兴趣了解更多关于NDT和Digital Imaging的未来吗？点击下面的链接报名参加作者的网络研讨会，Wesley Soape。