Compared to the traditional pixel-coding methods a more efficient way is to approximate the fringes of the phase contours with general polygons. However, even this often requires a considerable amount of computer memory resources and it is therefore desirable for the approximation to remain as coarse as possible. The effects of the polygon quantization have not been extensively analyzed but on visual basis. We have designed and implemented algorithms with which it is possible to quantitatively analyze the deviations from an ideal signal when the coarseness of the quantization is varied. An example of calculated intensity distributions is seen in Fig.
Ion exchange is a process which enables the modulation of refractive index inside glass.
A strong effort initiated in 1994 on theory, numerical modeling and experiments on ion-exchanged DOEs has continued producing new results in all areas of research. Our research has shown that ion exchange can be an attractive alternative for fabrication of DOEs in certain applications demanding robustness or flat surface. A fast finite difference method, previously implemented for modeling of two-dimensional thermal diffusion, has been extended to three dimensions both in rectangular and cylindrical coordinates. Several such elements have already been designed by a special optimization scheme, and Fig. Preliminary theoretical work has been conducted on cylindrically symmetric beam shapers and lenses.