Date of Award
Doctor of Philosophy (PhD)
Electrical and Computer Engineering
Aspherical lenses--Testing, Interferometry, Random Fiber Test (RFT)
Cylindrical optics of high quality are coming more and more into use. With the advances of cylindrical optics manufacture, interferometric testing of such optics is difficult and continues to be a challenge. The main reason of this challenge is the lack of a well characterized cylindrical reference surface. This dissertation work was motived by the need of finding efficient, convenient and economical techniques to improve the measurement accuracy of cylindrical optics. A new approach, the Random Fiber Test (RFT) for absolute interferometric testing of cylindrical optics, is presented. The RFT is a method to obtain the cylindrical interferometric testing system error which can be then subtracted from the actual measurement of the tested cylindrical optic. The RFT is based on the merging of two well-known techniques, the random ball test method with the fiber optic reference method. The random ball test assumes a large number of interferograms of a good quality sphere with errors that are statistically distributed such that the average of the errors goes to zero. The fiber optic reference test utilizes a specially processed optical fiber to provide a high quality reference wave from an incident line focus from the cylindrical wave under test. By taking measurements at different rotations and translations of the fiber, an analogous procedure can be employed. Several aspects of the RFT technique have been investigated in this dissertation to assure the validation and the feasibility of this technique. First, geometric error of the fiber surface has been studied to develop measurement algorithms that eliminate the fiber surface error contribution. A simulation of the RFT is then presented which indicates that this method can significantly reduce the effects of fiber surface errors, yielding more accurate cylindrical wave measurements. Misalignments always occur at some level in real optical systems. The fiber reference is no exception. Therefore, the fiber reference alignment introduced errors has been studied so that the proper algorithms can be used to numerically remove them, which greatly simplifies the RFT procedure since exact alignment is no longer necessary. Finally, experimental verification of the RFT technique presented. It is shown that this new technique is feasible for absolute measurement of cylindrical optics.
Alatawi, Ayshah, "The random fiber test for absolute measurement of cylindrical optics" (2015). Dissertations. 267.