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This is a special optical system which uses s telecentric lens. The most outstanding feature is that the size of the image on the CCD never changes even if the target object moves to the emitted/received light direction. In the case of normal lenses, an image is enlarged/reduced if the object is placed near/far, and thus, the measurements change depending on the position where an object is placed between emitted and received light. However, if the telecentric lens is used, the measurements do not change even if the object is moved. |