How does an optical comparator work? The best analogy to think about when describing how an optical comparator works, is that of the classic classroom projector that your teacher likely used to go over homework or explain concepts to you when you were in middle school. Similar to this projector, the optic comparator works on the basic principle of projecting a magnified image of the part you are measuring against a screen. The optical comparator is built with a series of very accurate lenses that magnify and transpose the part image. Additionally, optical comparators are built to be stable devices that are placed at fixed distances from the screen being used, in order to ensure a highly precise image and therefore measurement. The whole process through which an optical comparator works uses optics, or the physical principles of light, in order to make measurement easier and more flexible.