Full-color holographic display with increased-viewing-angle [Invited

Holographic display system with enhanced viewing angle using boundary folding mirrors

We have previously introduced a computational architecture suitable for driving full-color holographic display systems based around anisotropic leaky-mode modulators; this architecture appropriately handles single-sideband modulation and frequency-division multiplexing of spectral bands that correspond to the independent red, green, and blue color channels in the display output. In this paper, we describe an implementation for driving the MIT Mark IV holographic display system with such a computational approach, in cases of both pre-computed Fresnel CGHs and real-time, GPU-based diffraction specific coherent panoramagrams. Real-time holographic images of nearly VGA-resolution (468 lines) are generated via three dual-head NVIDIA GPUs via a CUDA-based implementation that encompasses the requisite orthographic view generation from 3-D data sources, parallel vector-based fringe computation per hogel and per color, single-sideband modulation, and frequency-division multiplexing. We present the first results of this scheme in driving the Mark IV display system and review the resulting holographic video output and performance metrics.

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.

This study presents an innovative inline dual-phase modulation technique for compact lensless holographic displays. By utilizing a single spatial light modulator (SLM) and employing two-phase components derived from double-phase holography symmetrically positioned in the upper and lower halves of the SLM, we achieve a holographic display through the superposition of a digital phase grating. This approach eliminated the need for bulky 4-F systems, resulting in a compact optical setup. Numerical simulations demonstrate that the proposed method provides high-precision image reconstruction using a single SLM, and the experimental results confirm its efficacy in achieving image reconstruction with minimal speckle noise compared to the conventional iterative random phase method. Additionally, incorporating an initial random phase reduces artifacts in practical experimental settings, producing less speckle noise than the conventional iterative random phase method. Moreover, based on the proposed method, a beam splitter was used for further coupling in the reconstruction plane, resulting in an expanded display area while maintaining a compact system. The proposed method can simplify various holographic display systems, including projection, near-eye, and 3D displays.

Holographic display and imaging are usually implemented with coherent lasers, which usually suffer from speckles. Incoherent light sources have long been highly desired for holographic applications, but the corresponding spatial modulation scheme is still lacking. Here we demonstrate a hyperspectral complex field modulation based on a single spatial light modulator (SLM) for an incoherent white light-emitting diode (LED) with a 200 nm bandwidth. The technique encodes the complex fields of multiple wavelengths into a phase hologram. The hologram has an analytical expression and is the superposition of multiple fringe patterns with different frequencies. By tuning the local fringe frequency on the hologram, one can modulate the local output spectrum. The method is applied for sweeping wavelength and projecting color images, where tens of spectral channels are modulated independently. Moreover, the method can achieve complex modulation and is applied in multi-plane holographic projections.

A liquid crystal panel for a video projector is often used for holographic television. However, its pixel size and pixel number are not enough for practical holographic 3-D display. Therefore, a multipanel configuration is generally used to increase the viewing window and displayed image size, and many spatial light modulators should be used in them. We propose a novel method to increase the viewing window of a holographic display system. The proposed method, which is implemented by using a mirror module and 4-f lens set, is to reconfigure the beam shape reflected by a spatial light modulator. The equipment is applied to a holographic display system, which has only a single spatial light modulator; a hologram could be displayed in a wider viewing window by the equipment than that of the conventional method. By the proposed method, the resolution of the reconfigured spatial light modulator has double resolution in the horizontal direction. Inversely, the vertical resolution is decreased. Even if the vertical resolution is decreased, a viewer could get 3-D effect because humans get more 3-D information in the horizontal direction. We have experimented using a liquid crystal on silicon (LcOS), whose resolution is 4096×2160 pixels. The reconfigured resolution by the mirror module is 8192×1080 pixels. From the experiments, the horizontal viewing window is almost two times wider than that without the mirror module. As a result, the hologram can be observed binocularly.

The application of CGH display technology to AR multi‐depth head‐up displays is a very popular research topic nowadays. However, the system implementation requires multiple projection devices or spatial light modulators with Freeform Mirror or complex optical mechanisms to present multi‐depth projection of automotive head‐up display, which does not meet the development needs in terms of system size and cost. Thus, it is worthwhile to investigate how to realize a multi‐depth projection head‐up display system with a single spatial light modulator. In this study, we attempt to realize a miniaturized multi‐depth CGH head‐up display system with Space‐Division Method (SDM) and a single spatial light modulator.

For practical holographic video display, it is important to generate holographic fringes as fast as possible. It is also important to display the full-color image with a simple display system. In our previous study, a full-color hologram was realized as a rainbow hologram, which discards the vertical parallax to reduce computation complexity. Its color reproduction, however, is not enough. Since this hologram uses the horizontal slit, proper color reproduction can be obtained only from a narrow viewing area in the vertical direction. In contrast, the image hologram provided a good contrast image, although it had only a single color. Also, the image hologram has full-parallax information. In this work, we investigate the image hologram for fast calculation and the display optics for full-color holograms with full parallax. Since image points are located close to the hologram, the required computation area of the image hologram becomes much smaller than that of the entire hologram. Therefore, vastly improved computational speed is obtained. The full-color hologram is displayed on a holographic video display system, which uses part of the original optics and liquid crystal on silicon (LCoS) panels of the conventional video projector to separate and combine color components. From the experimental results, we obtain a full-parallax reconstructed image and better color reproduction compared with the rainbow hologram.

Phase-only liquid crystal spatial light modulator (SLM) has been widely used for accurate phase-manipulation in holographic display, optical tweezers, lithography, etc. Due to the nonlinear optical response of liquid crystal and manufacturing defects, the grayscale-phase response could be different for every single SLM device. The calibration for phase modulation is needed for improving the performance of the SLM involved system. The principles of phase-only SLM are reviewed. The main phase calibration methods for SLM are discussed and compared.

A new holography display technology based on a phase-only spatial light modulator (SLM) is proposed. The normal use of laser diode (LD) light source led to the inevitable speckle noise introduced by the coherence of the laser beam. Algorithms and special diffractive optical elements have been proposed to reduce the speckle noise. In this paper, a selected light-emitted diode (LED) light source was used in the holographic display system to replace the LD light source. The temporal coherence and spatial coherence of the LED were studied. Though the temporal coherence of LED is short, the spatial coherence of the light field can be improved by optimizing the optical paths such as decreasing the emitting area of the light source and so on. A high-power LED with a narrow band-width was selected. An algorithm to generate computer-generated hologram for the SLM was proposed. The phase-only holograms for the display were computed using the coherent light algorithm. Then the phase holograms were uploaded to the SLM. LED was used as the light source to illuminate the SLM uniformly, and the reconstructions can be observed by naked eye. It is demonstrated that LED is an acceptable light source for holographic display. The reconstruction results showed that the speckle noise and multiple reflections were eliminated when LED was used as the light source.

We demonstrate that layered spatial light modulators (SLMs), subject to fixed lateral displacements and refreshed at staggered intervals, can synthesize images with greater spatiotemporal resolution than that afforded by any single SLM used in their construction. Dubbed cascaded displays , such architectures enable superresolution flat panel displays (e.g., using thin stacks of liquid crystal displays (LCDs)) and digital projectors (e.g., relaying the image of one SLM onto another). We introduce a comprehensive optimization framework, leveraging non-negative matrix and tensor factorization, that decomposes target images and videos into multi-layered, time-multiplexed attenuation patterns---offering a flexible trade-off between apparent image brightness, spatial resolution, and refresh rate. Through this analysis, we develop a real-time dual-layer factorization method that quadruples spatial resolution and doubles refresh rate. Compared to prior superresolution displays, cascaded displays place fewer restrictions on the hardware, offering thin designs without moving parts or the necessity of temporal multiplexing. Furthermore, cascaded displays are the first use of multi-layer displays to increase apparent temporal resolution. We validate these concepts using two custom-built prototypes: a dual-layer LCD and a dual-modulation liquid crystal on silicon (LCoS) projector, with the former emphasizing head-mounted display (HMD) applications.

Adaptive optics is used to compensate for modal dispersion in digital transmission through multimode fiber (MMF). At the transmitter, a spatial light modulator (SLM) controls the launched field pattern. An estimate of intersymbol interference (ISI) caused by modal dispersion is formed at the receiver and fed back to the transmitter, where the SLM is adjusted to minimize ISI. Error-free transmission of 10 Gbit/s non-return-to-zero signals through standard 50 microm graded-index MMFs up to 11.1 km long is demonstrated. It is shown that a single SLM can compensate for modal dispersion across a 600 GHz bandwidth.

In this paper, a color holographic display system based on the utilization of effective viewing area (EVA) is proposed. Color reconstruction is achieved by using a single spatial light modulator (SLM). The EVA of three color reconstructed images is analyzed based on the holographic diffraction theory and the principle of geometrical optics. Then, the effective holograms of three colors are calculated based on the EVA of the system. When three color lasers are used to collimate the SLM, three color reconstructed images can be coincided in the same position with a fast speed of calculation. Moreover, the chromatic aberration can be eliminated and the experimental results verify the feasibility of the proposed system.

Fluorescence recovery after photobleaching (FRAP) has remained a powerful tool to probe intracellular dynamics. FRAP relies on two aspects: (1) localized excitation resulting in photobleaching, and (2) fluorescence recovery of the bleached volume which provides insight into kinetics. Existing FRAP systems are limited by a trade-off between time and spatial multiplexing due to galvanometric scanning methods, precluding the study of multiple independent positions simultaneously as well as advanced widefield imaging modes. Hence, they may not capture the dynamic and non-isotropic environments in biological studies. In this paper, we utilize phase profiles corresponding to an array of Fresnel lenses and diffractive masks to switch between simultaneous FRAP of independent spatial positions whilst maintaining epifluorescence, highly inclined laminated optical sheet (HILO), and total internal reflection fluorescence (TIRF) microscopy modalities. Our approach bridges high contrast fluorescence imaging (HILO and TIRF) and a multi-position FRAP technique using a single spatial light modulator. As such, this technique enables high contrast bleaching and screening across volumes, which we envision will be of value to areas such as single particle tracking and single molecule imaging where dynamic photobleaching is necessary to measure fast events across the field of view in a single versatile instrument.

본 논문에서는 기존의 full color LED 전광판 영상 처리 방식을 개선시킨 획기적인 영상 구동 처리 기술을 제안하였다. 이 기술은 고화질의 대형 TV나 LCD Display에 적용 가능하며 선명한 표출구동의 영상제어를 가능하게 한다. 제안한 구동 제어 방식은 기존의 영상처리 기능을 효율적으로 보강할 수 있다. 자동 또는 수동으로 contrast, bright, tint, color, 감마보정 등의 영상 변화처리 조절이 가능하므로 선명한 화질을 얻을 수 있다. 그리고 경제적인 가격으로 구현이 가능하다. In this paper, the new efficient drive control technology based on the conventional full-color electric display board image processing method is proposed. This technology can be applied to high-fidelity large size panel TV and LCD Display, and makes high-fidelity-display-drive control possible in those. The proposed drive control technology can strengthen the image processing function of the conventional technology. Also, the automatic or manual adjustment of contrast, bright, tint, color, gamma revision, etc. can help to achieve high-fidelity vision. This technology can be adopted with lower price.