Iterative Dummy Area Method with Flexible Dummy Area Size for the Design of Kinoform

Abstract

As an algorithm that generates a kinoform which is a kind of phase-type computer-generated hologram, there is an iterative dummy area method. However, this algorithm produces the error in dummy area, because it reduces the error in the original image space using the degree of freedom in the dummy area. It is undesirable for an error to occur in the dummy area in use efficiency of the light. In this study, we aim to reduce the error in the dummy area. In the computer generated hologram, the reconstructed image is modulated by a sinc function in both the horizontal direction, vertical direction. Therefore, the peripheral part of reconstructed image darkens in comparison with center. Considering the optical reconstruction, we can ignore the error that exists in the peripheral part of reconstructed image. From this, we use only a peripheral part at the start as a dummy area and widen a range to gradually use as a dummy area. We call the area that newly added flexible dummy area. By this method, we can collect errors in the peripheral part.