Holography is usually considered as the ultimate way to visually reproduce a three-dimensional scene. Computer-generated holography constitutes an important branch of holography, which enables visualization of artificially generated scenes as well as real three-dimensional scenes recorded under white-light illumination. In this article, we present a comprehensive survey of methods for synthesis of computer-generated holograms, classifying them into two broad categories: wavefront-based methods and ray-based methods. We examine their modern implementations in terms of the quality of reconstruction and computational efficiency. As it is an integral part of computer-generated holography, we devote a special section to speckle suppression, which is also discussed under two categories following the classification of underlying computer-generated hologram methods.

We introduce a local signal decomposition method for the analysis of three-dimensional (3D) diffraction fields involving curved surfaces. We decompose a given field on a two-dimensional curved surface into a sum of properly shifted and modulated Gaussian-shaped elementary signals. Then we write the 3D diffraction field as a sum of Gaussian beams, each of which corresponds to a modulated Gaussian window function on the curved surface. The Gaussian beams are propagated according to a derived approximate expression that is based on the RayleighSommerfeld diffraction model. We assume that the given curved surface is smooth enough that the Gaussian window functions on it can be treated as written on planar patches. For the surfaces that satisfy this assumption, the simulation results show that the proposed method produces quite accurate 3D field solutions.

BackgroundThe aim of this study was to evaluate the effect of oral contraceptive pills (OCP) on the macula, the retinal nerve fiber layer (RNFL), and choroidal thickness (CT).Material/MethodsA total of 24 healthy women taking monophasic OCP (3 mg drospirenone and 0.03 mg ethinylestradiol) for contraception only for at least one year were compared with a control group of 24 healthy women who were not taking an OCP. Optical coherence tomography (OCT) was used to evaluate the posterior ocular segments, and measurements were taken in the follicular phase (day 3) of the cycle in all women.ResultsNo disparity in terms of age and body mass index between the groups was observed (p=0.436, p=0.538, respectively). In comparison of the macular region and CT between groups, we found that all variables except foveal center thickness and CT were significantly thinner in the OCP group. Nasal and temporal inferior parts of the RNFL and average RNFL were significantly slimmer in the study group versus the control group (p=0.013, p=0.018, and p<0.001, respectively).ConclusionsOCP resulted in several structural changes in the posterior ocular segment. Thus, women using OCP for more than one year may have some eye problems. Therefore, it OCT should be performed for these women. Further clinical trials researching long-period effect of OCP on the eyes are needed.

No abstract

No abstract

We present a local Gaussian beam decomposition method for calculating the scalar diffraction field due to a two-dimensional field specified on a curved surface. We write the three-dimensional field as a sum of Gaussian beams that propagate toward different directions and whose waist positions are taken at discrete points on the curved surface. The discrete positions of the beam waists are obtained by sampling the curved surface such that transversal components of the positions form a regular grid. The modulated Gaussian window functions corresponding to Gaussian beams are placed on the transversal planes that pass through the discrete beam-waist position. The coefficients of the Gaussian beams are found by solving the linear system of equations where the columns of the system matrix represent the field patterns that the Gaussian beams produce on the given curved surface. As a result of using local beams in the expansion, we end up with sparse system matrices. The sparsity of the system matrices provides important advantages in terms of computational complexity and memory allocation while solving the system of linear equations.

Light field representation is a model for three-dimensional (3D) image representation and integral imaging is an optical 3D imaging and representation method. A comparative investigation of light field representation and integral imaging is given in this paper. The practical integral imaging is shown to be equivalent to the discrete light field representation if some restrictions are imposed on the light field. On the other hand, it is shown that the integral imaging is not equivalent to the continuous light field representation. In any case, physical realisation of an arbitrary abstract light field representation may not be possible due to restrictions associated with the uncertainty principle related to the spatial and angular resolutions.

No abstract