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"Optical comparators are precision instruments that are used to measure various aspects of manufactured parts and other workpieces. Optical comparators do this by projecting a magnified image of the part in 2D on a screen. This allows the part to be compared with a set ideal. By understanding the variance between the projected image and the set ideal, quality control experts can determine if the part meets quality standards. A typical optical comparator uses a non-contact approach meaning that there is very little wear and tear. It is important to understand what exactly optical comparators measure in order to be able to perform their quality control function. Here are some of the parameters that these useful instruments measure.\n\nMeasuring Angles\n\nOptical comparators can measure angles easily using a process known as screen rotation. Here, vernier scales are used when rotating the screen ring. When the screen ring is rotated, the centerlines align with the first edge. The machinist then zeroes in on the angle display and then rotates the screen to align with the second edge. The optical comparator then displays the angle between the two edges in the display window for analysis.\n\nLength and Width – Method One\n\nThese are the most basic of measurements that one can take with an optical comparator. When measuring the length and width of a part, the part is first held in place (called staging).  When the optical comparator projects the image of the part on the screen, this then makes it very easy for the machinist or quality control operator to compare the calibrated settings against the image and determine if there is variance.\n\nLength and Width – Method Two\n\nThe second way optical comparators can be used to measure length and other parameters is by moving the stage on which the object being analyzed is secured. By having the center point of the screen lined up with various points of the image, the machine can then work out how far the stage moved to reach each of those points and thus giving an accurate assessment of the object’s dimensions.\n\nIn addition to length and width, optical comparators can measure the roundness of an object, the straightness of an object as well as the diameter and radius. The process for each of these differs slightly but centers around the same principles.\n\nChecking for Imperfections\n\nOne can use the magnifying abilities of the optical comparator to also check parts for any imperfection. During the manufacturing process, it is possible for many imperfections to occur on a part. By projecting and magnifying an image on a screen, machinists and quality control staff can check parts for indentations and chaffing.\n\nAs technology advances, optical comparators can do more and provide more accurate readings. For example, newer models of optical comparators come with touchscreens allowing operators to manipulate the image on the screen. There are also optical comparators that can measure and display the dimensions of a part without the need to rotate the screen or move the stage to get a reading."
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