Demonstration of a large-size real-time full-color three-dimensional display

Crosstalk Suppressed 3D Light Field Display Based on an Optimized Holographic Function Screen

A holographic function screen (HFS) can recompose the wavefront and re-modulate the light-field distribution from a three-dimensional (3D) light field display (LFD) system. However, the spread function of existing HFSs does not particularly suit integral imaging (II) 3D LFD systems, which causes crosstalk and reduces the sharpness of reconstructed 3D images. An optimized holographic function screen with a flat-top rectangular spread function (FRSF) was designed for an II 3D LFD system. A simulation was carried out through ray tracing, which verified that the proposed diffusion function could suppress crosstalk and improve the overall effect.

Automatic co-design of light field display system based on simulated annealing algorithm and visual simulation

Accurate, fast, and reliable modeling and optimization methods play a crucial role in designing light field display (LFD) system. Here, an automatic co-design method of LFD system based on simulated annealing and visual simulation is proposed. The process of LFD content acquisition and optical reconstruction are modeled and simulated, the objective function for evaluating the display effect of the LFD system is established according to the simulation results. In case of maximum objective function, the simulated annealing optimization method is used to find the optimal parameters of the LFD system. The validity of the proposed method is confirmed through optical experiments.

Investigation of Autostereoscopic Displays Based on Various Display Technologies

The autostereoscopic display is a promising way towards three-dimensional-display technology since it allows humans to perceive stereoscopic images with naked eyes. However, it faces great challenges from low resolution, narrow viewing angle, ghost images, eye strain, and fatigue. Nowadays, the prevalent liquid crystal display (LCD), the organic light-emitting diode (OLED), and the emerging micro light-emitting diode (Micro-LED) offer more powerful tools to tackle these challenges. First, we comprehensively review various implementations of autostereoscopic displays. Second, based on LCD, OLED, and Micro-LED, their pros and cons for the implementation of autostereoscopic displays are compared. Lastly, several novel implementations of autostereoscopic displays with Micro-LED are proposed: a Micro-LED light-stripe backlight with an LCD, a high-resolution Micro-LED display with a micro-lens array or a high-speed scanning barrier/deflector, and a transparent floating display. This work could be a guidance for Micro-LED applications on autostereoscopic displays.

Light Engineering in Nanometer Space

Significant advances have been made in photonic integrated circuit technology, similar to the development of electronic integrated circuits. However, the miniaturization of cavity resonators, which are the essential components of photonic circuits, still requires considerable improvement. Over the past decades, various optical cavities have been utilized to implement next-generation light sources in photonic circuits with low energy, high data traffic, and integrable physical sizes. Nevertheless, it has been difficult to reduce the size of most commercialized cavities beyond the diffraction limit while maintaining high performance. Herein, recent advancements in subwavelength metallic cavities that can improve performance, even with the use of lossy plasmonic modes, are reviewed. The discussion is divided in three parts according to light engineering methods: subwavelength metal-clad cavities engineered using intermediate dielectric cladding; implementation of plasmonic cavities and waveguides using plasmonic crystals; and development of deep-subwavelength plasmonic waveguides and cavities using geometric engineering. A direction for further developments in photonic integrated circuit technology is also discussed, along with its practical application.

Backward ray tracing based high-speed visual simulation for light field display and experimental verification

The exiting simulation method is not capable of achieving three-dimensional (3D) display result of the light field display (LFD) directly, which is important for design and optimization. Here, a high-speed visual simulation method to calculate the 3D image light field distribution is presented. Based on the backward ray tracing technique (BRT), the geometric and optical models of the LFD are constructed. The display result images are obtained, and the field of view angle (FOV) and depth of field (DOF) can be estimated, which are consistent with theoretical results and experimental results. The simulation time is 1s when the number of sampling rays is 3840×2160×100, and the computational speed of the method is at least 1000 times faster than that of the traditional physics-based renderer. A prototype was fabricated to evaluate the feasibility of the proposed method. From the results, our simulation method shows good potential for predicting the displayed image of the LFD for various positions of the observer's eye with sufficient calculation speed.

Integral imaging based light field display with holographic diffusor: principles, potentials and restrictions

Under the framework of light field, the diffusing angle and spatial location of holographic diffusor is investigated for the integral imaging based light field display. These two parameters are considered in terms of continuous light field reconstruction of the object point and blind visual spots elimination for the viewer. The concept of joint view reconstruction as well the essence of this view interpolation is analyzed theoretically, and a new phenomenon caused by the additional holographic plane called double window violation is also deduced. To the best of our knowledge, this is the first report on the quantitative analysis of the two key parameters of the holographic diffusor, which is deduced theoretically and verified experimentally.

Dual-View Integral Imaging 3D Display Based on Multiplexed Lens-Array Holographic Optical Element

We propose a dual-view integral imaging 3D display based on a multiplexed lens-array holographic optical element (MHOE). A MHOE is a volume holographic optical element obtained by multiplexing technology, which can be used for dual-view integral imaging 3D display due to the angle selectivity of the volume HOE. In the fabrication of the MHOE, two spherical wavefront arrays with different incident angles are recorded using photopolymer material. In the reconstruction, two projectors are used to project the elemental image arrays (EIA) with corresponding angles for two viewing zones. We have developed a prototype of the dual-view integral imaging display. The experimental results demonstrate the correctness of the theory.

Dynamic three-dimensional light-field display with large viewing angle based on compound lenticular lens array and multi-projectors

Real-time terrain rendering with high-resolution has been a hot spot in computer graphics for many years, which is widely used in electronic maps. However, the traditional two-dimensional display cannot provide the occlusion relationship between buildings, which restricts the observers' judgment of spatial accuracy. With three projectors, compound lenticular lens array and holographic functional screen, a dynamic three-dimensional (3D) light-field display with 90° viewing angle is demonstrated. Three projectors provide views for the right 30 degrees, center 30 degrees and left 30 degrees, respectively. The holographic functional screen recomposes the light distribution, and the compound lenticular lens array is optimized to balance the aberrations and improve the display quality. In our experiment, the 3D light-field image with 96 perspectives provides the right geometric occlusion and smooth parallax in the viewing range. By rendering 3D images and synchronizing projectors, the dynamic light field display is obtained.

Post-calibration compensation method for integral imaging system with macrolens array

Three-dimensional display with large-format is an inevitable and foreseeable trend for the future display technology, integral imaging is one of the most powerful and promising candidates to achieve this goal with full-parallax, true-color, acceptable viewing resolution and viewing angle. To obtain a 3D display with high quality, calibration is needed to correct optical misalignment and optical aberrations, which is often challenging and time consuming. We propose a post-calibration compensation method for the integral imaging system with macrolens array, the inter-lens position misalignment is corrected by forcing it to image in a regular ideal reference grid. Our method distinguishes itself from previous ones by finding the correct pixel-to-ray correspondence with a relatively simple setup and acceptable precision. A prototype is fabricated to evaluate the feasibility of the proposed method. Furthermore, the proposed method is evaluated in terms of the geometrical accuracy and quality of the reconstructed images.

A crosstalk-suppressed dense multi-view light-field display based on real-time light-field pickup and reconstruction

A crosstalk-suppressed dense multi-view light-field display based on real-time light-field pickup and reconstruction is demonstrated, which is capable of realizing high view density in the horizontal direction with low crosstalk between micro-pitch viewing zones. The micro-pinhole unit array and the vertically-collimated backlight are specially developed and used, instead of refraction-based optical components like lenticular lens, to avoid aberrations and to suppress crosstalk for accurately projecting multiple view perspectives into each eye pupil of the viewer. Additionally, the spatial information entropy is defined and investigated to improve 3D image perception for balancing resolution, which can be generally applicable to better-reconstructed 3D images with the limited number of resolution pixels. To enlarge the viewing angle of 3D images with smooth motion parallax, the novel high-efficient light-field pickup and reconstruction method based on the real-time position of the viewer's pupils is implemented with an eye tracker to scan 750 view perspectives with the correct geometric occlusion in real time at the frame rate of 40 fps. In the experiment, a floating horizontal-parallax 3D light-field image with the view density of 0.75 mm^-1 and the micro-pitch crosstalk of less than 7% can be perceived with the clear floating focus depth of 10 cm and the high resolution of 1920 × 1080 in the viewing angle of 70°.

162-inch 3D light field display based on aspheric lens array and holographic functional screen

Large-scale three-dimensional (3D) display can evoke a great sense of true presence and immersion. Nowadays, most of the large-scale autostereoscopic displays are based on parallax barrier with view zone jumping, which also sacrifices much brightness and leads to uneven illumination. With a 3840 × 2160 LED panel, a large-scale horizontal light field display based on aspheric lens array (ALA) and holographic functional screen (HFS) is demonstrated, which can display high quality 3D image. The HFS recomposes the light distribution, while the ALA improves the quantity of perspective information in a horizontal direction by using vertical pixels and it can suppress the aberration that is mainly caused by marginal light rays. The 162-inch horizontal light field display can reconstruct 3D images with the depth range of 1.5 m within the viewing angle of 40°. The feasibility of the proposed display method is verified by the experimental results.

Improvement of printing efficiency in holographic stereogram printing with the combination of a field lens and holographic diffuser

In this paper, we use a field lens and a holographic diffuser together to improve the printing efficiency of a holographic stereogram printing system based on the effective perspective images' segmentation and mosaicking method. The light rays' regulation function of the field lens and the modulation function of the holographic diffuser are analyzed. Holographic diffusers with different expanding angles are optimized by numerical simulations and verified by optical experiments. We can achieve a better holographic stereogram reconstruction effect as well as a better printing efficiency when adopting a field lens and a 10° holographic diffuser together. With the proposed method, the energy efficiency can be improved, and the printing time can be reduced greatly.

Interactive floating full-parallax digital three-dimensional light-field display based on wavefront recomposing

Advanced three-dimensional (3D) imaging techniques can acquire high-resolution 3D biomedical and biological data, but available digital display methods show this data in restricted two dimensions. 3D light-field displays optically reconstruct realistic 3D image by carefully tailoring light fields, and a natural and comfortable 3D sense of real objects or scenes is expected. An interactive floating full-parallax 3D light-field display with all depth cues is demonstrated with 3D biomedical and biological data, which are capable of achieving high efficiency and high image quality. A compound lens-array with two pieces of lens in each lens unit is designed and fabricated to suppress the aberrations and increase the viewing angle. The optimally designed holographic functional screen is used to recompose the light distribution from the lens-array. The imaging distortion can be decreased to less than 1.9% from more than 20%. The real time interactive floating full-parallax 3D light-field image with the clear displayed depth of 30 cm can be perceived with the right geometric occlusion and smooth parallax in the viewing angle of 45°, where 9216 viewpoints are used.

Image quality improvement of multi-projection 3D display through tone mapping based optimization

An optical 3D screen usually shows a certain diffuse reflectivity or diffuse transmission, and the multi-projection 3D display suffers from decreased display local contrast due to the crosstalk of multi-projection contents. A tone mapping based optimizing method is innovatively proposed to suppress the crosstalk and improve the display contrast by minimizing the visible contrast distortions between the display light field and a targeted one with enhanced contrast. The contrast distortions are weighted according to the visibility predicted by the model of human visual system, and the distortions are minimized for the given multi-projection 3D display model that enforces constrains on the solution. Our proposed method can adjust parallax images or parallax video contents for the optimum 3D display image quality taking into account the display characteristics and ambient illumination. The validity of the method is evaluated and proved in experiments.

High-efficient computer-generated integral imaging based on the backward ray-tracing technique and optical reconstruction

A high-efficient computer-generated integral imaging (CGII) method is presented based on the backward ray-tracing technique. In traditional CGII methods, the total rendering time is long, because a large number of cameras are established in the virtual world. The ray origin and the ray direction for every pixel in elemental image array are calculated with the backward ray-tracing technique, and the total rendering time can be noticeably reduced. The method is suitable to create high quality integral image without the pseudoscopic problem. Real time and non-real time CGII rendering images and optical reconstruction are demonstrated, and the effectiveness is verified with different types of 3D object models. Real time optical reconstruction with 90 × 90 viewpoints and the frame rate above 40 fps for the CGII 3D display are realized without the pseudoscopic problem.

Volume holographic printing using unconventional angular multiplexing for three-dimensional display

We propose and demonstrate a volume holographic printing method for dynamic three-dimensional (3D) display with an expanded space-bandwidth product (SBP) using unconventional angular multiplexing techniques. By wavefront encoding of the 3D scene, with the help of computer-generated holography, the object beam is loaded onto a 2D phase spatial light modulator (SLM) with a limited SBP. The printing method then writes a single hologram through the interference of the object beam with a reference beam as a holographic element (hogel) in the volume holographic polymer. In addition, multiple 3D scenes can be recorded and dynamically reconstructed by angular multiplexing in the same hogel location. The SBP can be increased by two orders of magnitude compared to the conventional holographic printing method, showing the potential to realize a dynamic and high-resolution 3D display.

Augmented reality three-dimensional display with light field fusion

A video see-through augmented reality three-dimensional display method is presented. The system that is used for dense viewpoint augmented reality presentation fuses the light fields of the real scene and the virtual model naturally. Inherently benefiting from the rich information of the light field, depth sense and occlusion can be handled under no priori depth information of the real scene. A series of processes are proposed to optimize the augmented reality performance. Experimental results show that the reconstructed fused 3D light field on the autostereoscopic display is well presented. The virtual model is naturally integrated into the real scene with a consistence between binocular parallax and monocular depth cues.

Automatic parameter estimation based on the degree of texture overlapping in accurate cost-aggregation stereo matching for three-dimensional video display

Stereo matching plays a significant role in three-dimensional (3D) display applications. The estimation of the regularization parameter, which strikes a balance between the spatial distance and color difference, is essential for successfully solving ill-posed image-matching problems. Based on the cost-filtering algorithm, a degree of texture overlapping is designed to simultaneously estimate the optimal regularization parameter and achieve accurate matching results. The experimental results demonstrate that the proposed model can estimate the smoothing parameter well, and the accuracy is comparable to other methods with manual adjustment. The application of the presented stereo-matching method in the 32-view 3D display is demonstrated.

Enhanced photorefractive performance of polymeric composites through surface plasmon effects of gold nanoparticles

We investigated the photorefractivity enhancement of polymeric composites by introducing gold nanoparticles (NPs). The gold NPs enhance the photocharge generation rate of sensitizers through plasmon resonance coupling achieved between NPs and sensitizers. Systematic studies show that the presence of gold NPs has increased photocharge generation efficiency, photoconductivity, diffraction efficiency, refractive index modulation, and photorefractive (PR) grating formation rate. The gold-NP-doped PR sample exhibits 2 times larger photocharge generation efficiency and photoconductivity, and 2.5 times faster PR grating formation rate compared to the control sample without the NPs.

Reflectance field display

We propose a display for stereoscopically representing an arbitrary object that is responsive to an arbitrary physical illumination source in the display environment. Our scheme is based on the eight-dimensional reflectance field, which contains angular and spatial information of incoming and outgoing light rays of an object, and is also known as the bidirectional scattering surface reflectance distribution function (BSSRDF). This system is composed of an integral photography unit, an integral display unit, and a processor connecting these units. The concept was demonstrated experimentally. In the demonstrations, a stereoscopically represented object responded to changes in physical illumination coming toward the display.

Dual-camera enabled real-time three-dimensional integral imaging pick-up and display

A new real-time integral imaging pick-up and display method is demonstrated. This proposed method utilizes the dual-camera optical pick-up part to collect 3D information of real scene in real-time without pre-calibration. Elemental images are then provided by a computer-generated integral imaging part and displayed by a projection-type integral imaging display part. The theoretical analysis indicates the method is robust to the camera position deviation, which profits the real-time data processing. Experimental results show that the fully continuous, real 3D scene pick-up and display system is feasible with a throughput of 8 fps in real time. Further analysis predicts that the parallel optimization can be adopted by the proposed method for real-time 3D pick-up and display with a throughput of 25 fps.

Single-beam data encoding using a holographic angular multiplexing technique

We propose a novel configuration for angular multiplexing holographic encoding in which the signal beam and the reference beam are combined into a single beam. By using a spatial light modulator based on twisted nematic liquid crystals, the signal and the reference beams are modulated in amplitude mode and phase mode, respectively. The multiplexed interference patterns with the reference beams of different incident angles are recorded near the Fourier transform plane, and then the signals are selectively reconstructed by the corresponding reference beam. Both the simulation and the experiment of single-beam angular multiplexed holography are performed with consistent results. Compared with the traditional angular multiplexing holographic recording system, the single-beam configuration is more compact, easier to adjust, and less sensitive to the vibration of the environment. Therefore, it will be more attractive for potential applications in many fields, such as high-density signal recording and data encryption.

The modulation function and realizing method of holographic functional screen

The modulation function of holographic functional screen (HFS) in the real-time, large-size full-color (RLF), three-dimensional (3D) display system is derived from angular spectrum analysis. The directional laser speckle (DLS) method to realize the HFS is proposed. A HFS by the DLS method was fabricated and used in the experiment. Experimental results show that the HFS is valid in the RLF 3D display, and that the derived modulation function is valuable for the design of the HFS. The research results are important to realize the RLF 3D display system which will find many applications such as holographic video.