The final image in Figure 3 could potentially take hours to produce using photo-editing software. Original image courtesy of Thierry Thomasset, Université Technologique de Compiègne. From one step to the next required only a single mouse click. Images from left to right show a sequence of stages in the colorization process using MountainsMap ® SEM software. In the corrected image, each color represents a different mineral phase that can yield a quantitative volume fraction.įigure 3 Image of erythrocytes (red blood cells). This type of image processing consists of subtracting the 2nd degree polynomial that best fits (least square method) the homogeneous (low variance) areas of the gray-level image. Figure 1c shows the result of applying mathematical correction of the gray levels. In Figure 1b, false color has been added by arbitrarily matching a color to each gray level however, because the gray levels were not uniform across the field, it is not possible to distinguish the phases confidently at this stage. This image exhibits non-uniform brightness, the right side being visibly darker than the left. Figure 1a shows a raw BSE image displayed in grayscale. This is the case when color is applied to SEM backscattered electron (BSE) images in which image brightness increases with increasing atom number in the specimen. Using this approach obviously doesn’t add any additional information to the image, but it can allow better visualization of image detail (or material phases) in a sample. This is known as pseudocolor or “false color.” Lookup tables may be based on the colors of the rainbow (blue-green-yellow-orange-red-white), the colors of the thermal scale (black, red, orange, white), or some arbitrary color scale. The numbers representing each pixel intensity can be arbitrarily matched to a color via a lookup table. Note: scale bars have been eliminated from some images in this article in order to concentrate on the image processing. Applying colors that were not present in the original image can change the viewer’s impression of the data, so the original image always should remain available to the viewer.This article describes how color (and 3D) can be added to SEM images using both traditional techniques and modern computer methods. Of course, whether color is applied manually or semi-automatically, the researcher has a responsibility not to cause misinterpretation of the data. Thanks to the increasing power of computer software and computer graphics, the technology surrounding electron microscopes is gradually moving toward both color and 3D. When it comes to viewing the nanoscopic world, researchers spend hours of their precious time manually “colorizing” SEM images in order to more clearly communicate their findings to other humans.īut that could soon change. Thus our brains rely on color (and stereoscopic vision) to correctly perceive objects. Color helps our brain to differentiate and identify objects. For millions of years perception of color helped our ancestors to survive, for example by allowing them to distinguish a ripe fruit hidden amongst the green leaves of a tree. Yet color is something important to us humans, and not just from an aesthetic point of view. Of course grayscale images from an SEM are normal since this technology forms images with electrons instead of photons of visible light. However, images provided by the SEM are black and white, and single images contain information in only two dimensions. Images produced are particularly appreciated for their high depth of field and excellent image resolution, both orders of magnitude better than light microscopy. The scanning electron microscope (SEM) is widely used in various fields of industry and science because it is one of the most versatile imaging and measurement tools.
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