Enhanced method for the generation of binary Fresnel holograms based on grid-cross downsampling

Abstract

Past research has demonstrated that digital Fresnel holograms can be binarized in a non-iterative manner by downsampling the source image with a grid lattice prior to the hologram generation process. The reconstructed image of a hologram that is binarized with this approach is superior in quality compared with that obtained with direct thresholding, half-toning, and error diffusion. Despite the success, the downsampling mechanism results in a prominent texture of regularly spaced voids in the shaded regions. To alleviate this problem, an enhanced non-iterative method for the generation of binary Fresnel holograms is presented. Our method is based on a multi-direction line-sampling formed by a combined grid and cross lattice, which is capable of preserving a more solid texture in the shaded regions and enhancing the visual quality of the reconstructed image. Computer simulations and optical reconstructions are shown to demonstrate the effectiveness of our proposed technique.

Generation of integrated binary Fresnel hologram for multiple images

“…For the sake of clarity, the method reported in [14] for generating a real off-axis binary digital hologram, is outlined in this section. To begin with, consider a 3D image in the object scene with the intensity profile and axial distance from the hologram represented by I u v ( , ) and z u v ( , ), respectively.…”

“…Although there are some background noise, they are distributed rather uniformly over the display area. For the sake of comparison, we also generated the binary hologram from the four source images that have been down-sampled with the grid-cross lattice based on a down-sampling factor of 8 (method reported in [14]). The reconstructed image at the focal plane is shown in figure 7(b).…”

“…Next, we printed the holograms prepared with our proposed method, and the grid-cross down-sampling method on a transparent film. The optical reconstructed images of the binary holograms are shown in figure 8(a) (our proposed method) and (b) (based on the method in [14]). Due the imperfection of the printer and the optical setup, the quality of the reconstructed images is not as good as those obtained with numerical reconstruction.…”

“…Despite the success of these methods, printing of phase-only holograms is a more tedious and expensive process as compared with the printing of amplitude-only holograms. Recently, it has been demonstrated that binary amplitude-based hologram can be generated with good diffraction efficiency, as well as preserving the shaded regions in the object scene favorably, by down-sampling the latter with a uniform sampling lattice [13,14]. Despite the success of the above mentioned works, they are applied to record a single image in a binary hologram.…”

“…The details of our proposed method will be elaborated in this article in the following manner. In section 2, a brief introduction on the generation of a real, off-axis binary hologram based on the method reported in [14] is described, together with an illustration on its effectiveness and shortcoming. Our proposed method for generating an IBH for embedding multiple source images is presented in section 3.…”