Intermediate pupil mask is adopted for synthesis of computer-generated holograms via Fourier ptychographic method. The problem of the conventional Fourier ptychographic method is that the exact target images cannot be created, when it utilized to synthesize computer-generated holograms. In the previous study, the diffraction effect on target images is ignored, and the target images are generated by light-field scheme. However, the mismatched target images degrade the quality of holographic images. The degradation can be mitigated by choosing the optimal size of the sub-regions. The optimal size of the sub-regions can be derived by considering the all-in-focus condition. It is also shown that the computation load can be reduced by setting the pupil mask to Gaussian function. The proposed method has an advantage in computation load for their image quality compared with other hologram synthesis algorithms. The proposed method is verified by numerical simulation.
Recent developments in ultra-high-definition (UHD) displays have a major impact on holographic displays as well as conventional display systems. A spatial light modulator (SLM) can reproduce hologram data through wavefront modulation of the incident light, and a holographic printer can record a high-quality hologram by sequentially recording a number of holograms reproduced by the SLM on a holographic material. As UHD (4K) resolution SLMs have been popularized, higher quality holograms can be reproduced compared to previous 2K resolution SLMs. When applied to the holographic printer, it is possible to manufacture holographic optical elements (HOEs) having a multifunctioning property and a wide field of view. In this paper, we introduce the holographic printer system using an amplitude UHD SLM and its applications. The holographic printer consists of optical systems to generate high-quality hologram from UHD SLM and mechanical systems to record the hologram on holographic material. The details of the total system are introduced. Furthermore, we introduce a holographic near-eye display system using UHD SLM and an image combiner HOE which is manufactured by the holographic printer.
Multifocal displays which physically float multiple focal planes are one of the promising solutions to provide focus cues for near-eye displays. With respect to the focal plane arrangements, several works proposed to dynamically change focal plane configuration as it could efficiently cover wide depth range with a few focal planes to reduce focusing error. Although they optimize the plane locations based on the resultant retinal images for target volumetric scenes, computational loads to synthesize retinal images become significantly larger as the resolution of target contents increases. Here, we propose to exploit the deep neural network to figure out the optimized focal plane configuration without directly depicting resultant retinal images. We demonstrate that designed network computes the focal plane positions to achieve optimal retinal images through numerical simulations.
In this paper, an end-to-end optimization of optics and image processing which consider angle of incidences is proposed. By considering the various angle of incidences to the optics, the optimized system can capture and reconstruct a real image even for non-paraxial input light. The optimization pipeline includes diffractive wave simulation, effects from wavelength differences, and image processing. Several points spread functions are used to simulate captured images for tilted input light. Captured images are reconstructed by different deconvolution kernels according to the sub-section of the images. To apply the system to real-world experiments, we consider the limitation of diffraction angle for given memory constraints and differences between manufacturing and sensor resolution by using Fourier optics. We demonstrate the simulation results of the proposed approach by applying it to various angle of incidences.
Computational accommodation-invariant (AI) display attempts to mitigate vergence-accommodation conflict (VAC) by showing a constant imagery no matter where the observer focuses on. However, due to the usage of an electrically focus-tunable lens, the contrast of imagery is degraded as point-spread functions of multiple foci are integrated. In this paper, we introduce the content-adaptive approach to improve the contrast at the depth of highly salient region in the image. The position of focal plane is dynamically determined considering the zone of comfort and the mean focal distance of salient region. The contrast enhancement compared to conventional accommodation-invariant display is shown through simulation results using USAF resolution target image. We demonstrate our proof-of-concept prototype and its optical feasibility is verified with experimental results.
Currently, commercial head-mounted displays suffer from limited accommodative states, which lead to vergenceaccommodation conflict. In this work, we newly design the architecture of head-mounted display supporting 15 focal planes over wide depth of field (20cm-optical infinity) in real time to alleviate vergence-accommodation conflict. Our system employs a low-resolution vertical scanning backlight, a display panel (e.g. liquid crystal panel), and focus-tunable lens. We demonstrate the compact prototype and verify its performance through experimental results.
Even now that DNA test has become common, latent fingerprints are still a useful evidence for finding criminals. However, the latent fingerprints are often damaged and overlapped with each other. At present, these overlapped fingerprints are separated manually by a person. It is not only time-consuming task, but also less likely to be adopted as evidence because it is difficult to rule out of the intention of a person. In this paper, non-destructive method to capture and separate overlapped fingerprints using digital holography and machine learning is presented and demonstrated.
Although there have been a desire to implement ideal three-dimensional (3D) displays, it is still challenging to satisfy commercial demands in resolution, depth of field, form factor, eye-box, field of view, and frame rate. Here, we propose shape scanning displays that may have extremely large depth of field (10cm-infinity) without loss of frame rate or resolution, and enough eye-box (7.5mm) with moderate field of view (30°). Furthermore, our prototype provides quasi-continuous focus cues as well as motion parallax by reconstruction of 120 tomographic layers. Shape scanning displays consist of a tunable lens, a display panel, and a spatially adjustable backlight. The synchronization of the tunable lens and spatially adjustable backlight could provide additional dimension of depth information. In summary, we introduce a novel 3D display technology called shape scanning displays that present superior performance in resolution, depth of field, and focus cue reproduction. This approach has a lot of potential to be applied for various field in 3D displays including head-up displays, tabletop displays, as well as head-mounted displays. It could be efficient solution for vergence-accommodation conflict as providing accurate focus cues.