Color holographic display system based on utilization of effective viewing area

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.

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.

Holographic display system with enhanced viewing angle using boundary folding mirrors

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.

Parallel calculations of large-pixel-count computer-generated holograms (CGHs) are suitable for multiple-graphics processing unit (multi-GPU) cluster systems. However, it is not easy for a multi-GPU cluster system to accomplish fast CGH calculations when CGH transfers between PCs are required. In these cases, the CGH transfer between the PCs becomes a bottleneck. Usually, this problem occurs only in multi-GPU cluster systems with a single spatial light modulator. To overcome this problem, we propose a simple method using the InfiniBand network. The computational speed of the proposed method using 13 GPUs (NVIDIA GeForce GTX TITAN X) was more than 3000 times faster than that of a CPU (Intel Core i7 4770) when the number of three-dimensional (3-D) object points exceeded 20,480. In practice, we achieved ∼40 tera floating point operations per second (TFLOPS) when the number of 3-D object points exceeded 40,960. Our proposed method was able to reconstruct a real-time movie of a 3-D object comprising 95,949 points.

The generalised phase contrast (GPC) method provides versatile and efficient light shaping for a range of applications. We have implemented a generalised phase contrast system that used two passes on a single spatial light modulator (SLM). Both the pupil phase distribution and the phase contrast filter were generated by the SLM. This provided extra flexibility and control over the parameters of the system including the phase step magnitude, shape, radius and position of the filter. A feedback method for the on-line optimisation of these properties was also developed. Using feedback from images of the generated light field, it was possible to dynamically adjust the phase filter parameters to provide optimum contrast.

A holographic storage system based on digital holography is proposed for recording and retrieving a phase data page in a compact and simple optical setup. In the proposed recording system, complex amplitude distribution can be modulated using a single phase-only spatial light modulator. The complex amplitude distribution of a retrieved phase data page is detected with the Fourier fringe analysis. The use of digital holographic techniques enables realizing a compact and simple holographic recording system, which is independent of misalignment problem in conventional holographic storage systems. The capability of the proposed recording system is numerically and experimentally evaluated.

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.

Among the important features of holographic displays are the wide viewing angles and the full color of the reconstructed images. The present work focuses on achievement of both features. We propose an increased-viewing-angle full-color holographic display using two tiled phase-only spatial light modulators (SLMs), a 4f concave mirrors system, and a temporal-spatial multiplexing method. The 4f optical system consists of two concave mirrors and serves to increase the viewing angle. A temporal-spatial multiplexing synchronization control (TSMSC) method is developed to achieve a full-color image and to remove the color crosstalk of the image. We calculate RGB phase-only holograms of a computer-generated color pyramid by using a slice-based Fresnel diffraction algorithm. The experimental results indicate that the proposed display system is feasible to reconstruct a full-color holographic 3D image with a viewing angle of 12.8°, which is about 3.8 times wider than the viewing angle formed by a single SLM.

Laser based displays have gathered much attention because only the displays can express full color gamut of Ultra- HDTV, ITU-R BT.2020. There are many types of laser based displays. A projector with single spatial light modulator (SLM) is a main stream in the displays so far. This projector uses the laser light sources under pulse with duty of 20- 50 %. We improved a triple-emitter 638-nm high-power broad area (BA) laser diode (LD) for this application. Countermeasures were adopted to improve the output power characteristics and strengthen the facet to the fatal degradation. The improved triple emitter showed the output of 5.0 W at the injection current of 5 A under pulse with duty of 30%, case temperature of 25°C. The output was increased by 4.1% compared to the former. The peak wall plug efficiency reached to 41.5% under 25°C. The long term aging test was also performed. Mean time to failure of the improved LD was estimated 57,000 hours under the output of 3.5 W, pulse condition with duty of 30%. The value was approximately 2.6 times longer than that of the former.

Laser-based displays have gathered much attention because only the displays can express full color gamut of Ultra-HDTV, ITU-R BT.2020. There are many types of laser-based displays. A projector with a single spatial light modulator is mainstream in the displays so far. This projector uses the laser light sources under pulse with duty of 20% to 50%. We improve a triple-emitter red color 638-nm high-power broad area laser diode (LD) for this application. Countermeasures are adopted to improve the output power characteristics and strengthen the facet to the fatal degradation. The improved triple emitter shows the output of 5.0 W at the injection current of 5 A under pulse with duty of 30%, case temperature of 25°C. The output is increased by 4.1% compared to our former one. The peak wall plug efficiency reaches to 41.6% under 25°C. The long-term aging test is also performed. Mean time to failure of the improved LD is estimated 72,000 h under the output of 3.5 W, pulse condition with duty of 30%. The value is ∼3.3 times longer than that of the former.

We propose a nonlinear joint transform correlator (JTC) based on a joint power spectrum via second-harmonic generation (SHG) in the Fourier domain. The fundamental waves of 1064 nm infrared light illuminate the images displayed by a single spatial light modulator. After SHG in a type-II potassium titanyl phosphate crystal in the Fourier domain, the second-harmonic wave of 532 nm visible light yields the correlation signal. We demonstrate the performance of our SHG-based JTC for human face recognition and quick response code recognition. Our work has the potential in various optical information processing applications such as infrared pattern recognition and remote sensing, security verification, target tracking, and optical computing.

The cumulative achievements in the fields of science and technology have allowed us to substantially approach the solution of the phase problem in optics. Among all phasometric methods, single-beam methods are the most promising, since they are more variable and versatile. Single-beam methods are based either on the analysis of the intensity distribution, as is conducted by interferometers and wavefront sensors, or on the transformation of the phase into an intensity distribution due to spatial filtering, as is conducted by holographic methods. However, all these methods have the problem of working with polychromatic radiation and require spectral filters to process such radiation. This paper presents a new approach to the synthesis of Fourier holograms used in holographic wavefront sensors that make it possible to create achromatic elements and work with white light without the use of additional filters. The approach was numerically and experimentally verified.

A new technique is presented to produce any desired mean far-field irradiance pattern using a partially-coherent Schell-model source. The new method differs from similar approaches in the literature by requiring only phase control. This permits the proposed approach to be easily implemented in the laboratory using a single spatial light modulator. The analytical development of the phase-only method is presented and discussed. Simulation and experimental results are presented to validate the proposed method. Applications for the new technique include free-space optical communications, material processing/manufacture, and particle trapping.