Analysis of Digital Hologram Rendering Using a Computational Method

Active studies on holography, which is the ideal and final goal of 3-dimensional (3D) image display, have been undertaken mainly in the US, Europe, and Japan. In particular, real-time holographic video is the core technology for the next-generation 3D television (TV). The computer-generated hologram (CGH) was proposed by Brown and Lohmann [1] in 1966. It obtains an interference pattern through an arithmetic operation on a personal computer (PC) by approximating optical signals. Thus, it is easy to obtain a digital hologram (DH) with this CGH method for real and virtual objects. The problem with this method is that it exhausts much calculation time. For example, to calculate a DH using the CGH method, approximately 900 seconds are required if a general PC is used to display a significant quantity of computation (3D object measuring approximately 1 × 1 × 1 cm in space). To resolve this problem, Yoshikawa [2] tried to increase the calculation speed by recursively adding only the distance difference between a source point on the 3D object and the digital hologram to be generated. In [3], another recursive technique was proposed where only the leftmost pixel of a row in a digital hologram is fully calculated and the remaining pixels of the row are recursively calculated such as by adding the pre-calculated values and the previously calculated results to the results for the first column pixel of the row. The purpose of this paper is to analyze a CGH method for calculation speed to generate a digital hologram. We analyze previous recursive methods [3] to identify the regularity between the depth-map image and the digital hologram. In section II, previous CGH methods are described. Section III contains analysis of the CGH method and then optimization of the CGH method. Our conclusions are given in section IV.