In mechanism design, it is often necessary to accurately measure the relative motions produced by an assembly of rigid bodies connected by joints. A number of analytical tools exist for the theoretical kinematic analysis of the relative motions produced by such an assembly. However, a relatively limited number of corresponding experimental methods for handling such motions exist. Optical methods are especially useful because they do not require that the measurement system touch the assembly being analyzed. A photo-optical method, holographic interferometry, is presented for the experimental determination of finite screw displacements. The purpose of this paper is to show how double-exposure holographic interferograms can be used to provide information about screw axes for general motions of an object in three-dimensional space. This investigation deals with the translation component of a screw axis and categorizes the fringe patterns resulting from in-plane and out-of-plane translations and their combinations. The resulting screw axis for each special displacement case is computed.
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