| Summary: | 碩士 === 大同大學 === 光電工程研究所 === 88 === The diffractive optical elements ( DOE’s ) based on basic diffraction theory have the advantages of small size, light weight, fiexibility and ease of duplication. In this thesis, the iterative method was modified to design DOE’s for some specified patterns. In the modified iterative method, a technique that resets large noise elements to a pre-determined value is used to increased the efficiency and the SNR. It is called the noise reduction technique. Then, the methods to design double-wavelength DOE’s which are based on the iterative method are presented. Using the double-wavelength DOE’s, a light beam consisting of two wavelength will generate two different patterns associating to individual wavelength.
In this work, efficiency, root-mean-square error, SNR and signal variation are used as the parameters to examine the design performance of DOE’s. The optimal design is obtained by evaluating a linear quality factor which is a linear combination of these parameters. DOE’s of ten target patterns of different numbers of distributed and concentrated signals were designed, and the comparisons of their performance were presented and discussed.
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