Holographic Functional Screen Research Articles

Three-dimensional light field display for view density enhancement based on lenticular lens time-multiplexed stitching and views compression fitting method

Three-dimensional (3D) light field display technology became an inevitable future development trend but suffers from insufficient view density. With directional backlight, lenticular lens array, lens array, and holographic functional screen, a new time-multiplexed method is demonstrated to enhance the view density of the light field display. By utilizing a lenticular lens array, the beams through the synchronously refreshed LCD from the sequential directional backlight are converged and time-multiplexed stitched in the focal plane. In addition, the views compression fitting method is proposed further to break the tradeoff between view density and spatial resolution. The experimental findings reveal that the proposed light field display system reconstructs realistic full-parallax 3D images with correct perception and a view density of 1.42 mm−2, and the fitting method enhances the sharpness of the reconstructed 3D scene.

Deep neural network-enabled resolution enhancement for the digital light field display based on holographic functional screen

The digital light-field display suffers from low resolution due to lack of planar pixels transformed into spatial information, which limits three-dimensional (3D) visual effect obviously. Herein, a pre-coding optimization of rendering the elemental image array (EIA) using a resolution-enhanced deep neural network (RE-DNN) is proposed, and it is used to enhance each reconstructed view perspective with high clarity besides using the holographic functional screen (HFS). The RE-DNN is used to cooperate with the HFS to form additional effective visual pixels/sub-pixels without increasement of physical planar resolution. The simulation and experimental presented 3D images with high clarity are demonstrated, verifying the feasibility and superiority of the proposed resolution enhancement method.

The pre-coding optimization for the digital horizontal glass-free 3D display based on holographic functional screen

Each reconstructed view perspective suffers low display quality due to the shortage of planar pixels for mapping light rays with designated intensity and directions to integrate the 3D image, which limits the 3D visual effect of the digital glass-free three-dimensional (3D) display. Here, a pre-coding optimization method of rendering the elemental image array (EIA) is further proposed and used to enhance each reconstructed view perspective with high clarity and rich details besides using the holographic functional screen (HFS). The pre-coding is realized by reassigning designated sub-pixels of the parallax images (PIs), which are used to synthesize the EIA, by linearly weighting their adjacent sub-pixels with the normalized Gaussian function before the synthetization of the EIA with the PIs. The normalized Gaussian function based reassignment of sub-pixels is consistent with the visual property of the human eye. The simulation and experimental presented 3D images with high clarity and rich details are demonstrated, verifying the feasibility and superiority of the proposed method.

The Flipping-Free Full-Parallax Tabletop Integral Imaging with Enhanced Viewing Angle Based on Space-Multiplexed Voxel Screen and Compound Lens Array

Tabletop integral imaging display with a more realistic and immersive experience has always been a hot spot in three-dimensional imaging technology, widely used in biomedical imaging and visualization to enhance medical diagnosis. However, the traditional structural characteristics of integral imaging display inevitably introduce the flipping effect outside the effective viewing angle. Here, a full-parallax tabletop integral imaging display without the flipping effect based on space-multiplexed voxel screen and compound lens array is demonstrated, and two holographic functional screens with different parameters are optically designed and fabricated. To eliminate the flipping effect in the reconstruction process, the space-multiplexed voxel screen consisting of a projector array and the holographic functional screen is presented to constrain light beams passing through the corresponding lens. To greatly promote imaging quality within the viewing area, the aspherical structure of the compound lens is optimized to balance the aberrations. It cooperates with the holographic functional screen to modulate the light field spatial distribution. Compared with the simulation results, the distortion rate of the imaging display is reduced to less than 9% from more than 30%. In the experiment, the floating high-quality reconstructed three-dimensional image without the flipping effect can be observed with the correct 3D perception at 96° × 96° viewing angle, where 44,100 viewpoints are employed.

3D light-field display with an increased viewing angle and optimized viewpoint distribution based on a ladder compound lenticular lens unit.

Three-dimensional (3D) light-field displays (LFDs) suffer from a narrow viewing angle, limited depth range, and low spatial information capacity, which limit their diversified application. Because the number of pixels used to construct 3D spatial information is limited, increasing the viewing angle reduces the viewpoint density, which degrades the 3D performance. A solution based on a holographic functional screen (HFS) and a ladder-compound lenticular lens unit (LC-LLU) is proposed to increase the viewing angle while optimizing the viewpoint utilization. The LC-LLU and HFS are used to create 160 non-uniformly distributed viewpoints with low crosstalk, which increases the viewpoint density in the middle viewing zone and provides clear monocular depth cues. The corresponding coding method is presented as well. The optimized compound lenticular lens array can balance between suppressing aberration and improving displayed quality. The simulations and experiments show that the proposed 3D LFD can present natural 3D images with the right perception and occlusion relationship within a 65° viewing angle.

Reduction of pixel deviation effect in three-dimensional light-field display based on the fitting algorithm with dense-viewpoints

In three-dimensional (3D) light-field displays, the quality of a reconstructed image degrades with increasing depth of field due to the pixel deviation effect. A fitting algorithm of dense-viewpoints is proposed to reduce the pixel deviation with high image quality. To analyze the pixel deviation effect, the human vision-based perspectives perceived from 3D light-field display system with the holographic functional screen are mathematically modeled. The optimized synthetic image is coded according to the mapping relationship from the display model and the optimal Gaussian distribution parameters achieved with the maximum likelihood estimation method. The effectivenesses of the proposed model and the optimization method are verified through simulations as well as optical experiments. A human vision-based high resolution 3D light-field display with 45-degree viewing angle and the large depth of field is achieved.

Depth of field analysis for a three-dimensional light-field display based on a lens array and a holographic function screen

Compared with traditional integral imaging systems, light-field displays (LFDs) based on a holographic functional screen (HFS) shows significant advantages in terms of the number of viewpoints, large viewing angle, and high viewing resolution. LFDs usually suffer from a limited depth range, and the reason majorly originates from the pixel deviation effect in the reconstruction process. Here, an analysis method for the depth of field (DOF) based on the pixel deviation effect observed on the HFS plane is presented. Simulation experiments are carried out to show that the percentage of pixel deviation is a more accurate measure to calculate the DOF. The feasibility of this method is verified in optical experiments.

A full-parallax tabletop three dimensional light-field display with high viewpoint density and large viewing angle based on space-multiplexed voxel screen

A full-parallax tabletop three dimensional (3D) light-field display with high viewpoint density and large viewing angle is demonstrated based on the space-multiplexed voxel screen, which consists of nine projectors and a holographic functional screen. Each voxel point on the space-multiplexed voxel screen emits nine light beams with different directions to reconstruct nine different viewing areas, and the viewpoint density in the large viewing angle is significantly improved. As the viewpoint density increases, the aliasing phenomenon is reduced. Simulation and comparison experiments of the 3D light-field display system with the liquid crystal display (LCD) panel and space-multiplexed voxel screen are carried out, and results show the effectiveness of the proposed method. A high quality of 3D light-field image is achieved with 44100 viewpoint perspectives in 96° viewing angle along vertical and horizontal directions.

Three-dimensional light-field display with enhanced horizontal viewing angle by introducing a new lenticular lens array

Three-dimensional (3D) light-field display simulates the authentic light-field distribution of objects, but its narrow viewing angle remains an obstacle for medical and educational applications. Here, a light-field display system based on lenticular lens array (LLA), lens array (LA) and holographic functional screen (HFS) is demonstrated, which can regenerate the high viewpoint density 3D light-field with both large horizontal viewing angle and appropriate vertical viewing angle. The LLA is introduced in the system to expand crucial horizontal viewing angle and to improve stereo perception. The application of optical optimization lens and HFS can suppress aberration and improve the accuracy of reconstructed light-field distribution. In the experiment, a full-parallax 3D light-field display prototype with the correct geometric occlusion is realized with 70 degrees horizontal viewing angle and 30 degrees vertical viewing angle, where 11000 viewpoints are obtained. A sophisticated 3D scene is optically reconstructed with the synchronization of capture and image encoding, which proves the feasibility and applicability of the method.

Holographic display method with a large field of view based on a holographic functional screen.

In this paper, we propose a method to increase the field of view (FOV) in a holographic display. Different from the traditional method, a large-sized computer-generated hologram (CGH) is generated, and a holographic function screen is used in the proposed method. The CGH is formed by superposition of interference fringes. The diffraction boundary angle of the interferogram is set to be equal to the maximum diffraction angle of the reconstructed light. In the holographic reconstruction, three spatial light modulators (SLMs) arranged side by side in a linear configuration are used to load the CGH. The holographic functional screen is used for eliminating the seams between the SLMs and further enlarging the diffraction light. With the proposed method, the reconstructed light after each image point is expanded, so that the FOV can be increased effectively. Experimental results prove the feasibility of the proposed method.

Full-parallax 3D light field display with uniform view density along the horizontal and vertical direction

For traditional integral imaging display systems with usual lens array, there is the same viewing angle in the horizontal and vertical direction. Due to usual display has vertically long sub-pixels, this sub-pixel shape makes the view density be lower in vertical direction than the horizontal one. Here, a clear full-parallax 3D light field display with uniform view density along the horizontal and vertical direction is demonstrated. The proposed 3D display system consists of a collimated backlight source, a 31.5-inch LCD with the resolution of 3840×2160, an aspherical cylindrical compression lens (ACCL) array and a holographic functional screen (HFS). The ACCL array is used to compress the vertical viewing angle to increase the view density in the vertical direction. After combining the collimated backlight, the aberration of the system is suppressed. Compared with traditional integral imaging display, the viewpoint density in the vertical direction is increased and the aliasing phenomenon is reduced. Experimental results show that a clear full-parallax light field 3D image can be achieved in the horizontal viewing angle of 81 degrees and the vertical viewing angle of 27 degrees.

Computational Super-Resolution Full-Parallax Three-Dimensional Light Field Display Based on Dual-Layer LCD Modulation

Due to physical limitation in resolution of display device, it is usually very difficult to achieve a high spatial resolution and a high angular resolution simultaneously for a three-dimensional (3D) light field display. Here, a computational super-resolution full-parallax 3D light field display is demonstrated, which can achieve both high spatial resolution and angular resolution. The proposed display consists of a specially designed backlight unit with controlled scattering angle, two cascadedly arranged LCDs with a resolution of 3840 × 2160, an aberration-suppressed compound lens array, and a holographic functional screen. The optical image formation processing of the display is analyzed and modeled as a whole process, and the superresolution light field synthesis method is presented. By co-designing the optical elements with computation processing, our proposed display architecture can improve the spatial resolution and angular resolution with a factor of 2× in both horizontal and vertical directions, comparing with these of the conventional light field display with single LCD and standard lens array. Finally, a super-resolution full-parallax 3D light field display with a designed spatial resolution of about 640 × 360 in a display area of 21.5 inches and an angular resolution of 166 × 166 in a viewing angle of 45 × 45 degrees is constructed, and an excellent 3D visual experience with improved image quality can be perceived.

Time-multiplexed light field display with 120-degree wide viewing angle.

The light field display can provide vivid and natural 3D performance, which can find many applications, such as relics research and exhibition. However, current light field displays are constrained by the viewing angle, which cannot meet the expectations. With three groups directional backlights and a fast-switching LCD panel, a time-multiplexed light field display with a 120-degree wide viewing angle is demonstrated. Up to 192 views are constructed within the viewing range to ensure the right geometric occlusion and smooth parallax motion. Clear 3D images can be perceived at the entire range of viewing angle. Additionally, the designed holographic functional screen is used to recompose the light distribution and the compound aspheric lens array is optimized to balance the aberrations and improve the 3D display quality. Experimental results verify that the proposed light field display has the capability to present realistic 3D images of historical relics in 120-degree wide viewing angle.

360-degree tabletop 3D light-field display with ring-shaped viewing range based on aspheric conical lens array.

When employing the light field method with standard lens array and the holographic functional screen (HFS) to realize the tabletop three-dimensional (3D) display, the viewing area of the reconstructed 3D images is right above the screen. As the observers sit around the table, the generated viewpoints in the middle of the viewing area are wasteful. Here, a 360-degree viewable light-field display system is demonstrated, which can present 3D images to multiple viewers in ring-shaped viewing range. The proposed display system consists of the HFS, the aspheric conical lens array, a 27-inch LCD with the resolution of 3840×2160, the LEDs array and the Fresnel lens array. By designing the aspheric conical lens, the light rays emitting from the elemental images forms the viewpoints in a ring-type arrangement. And the corresponding coding method is given. Compared with the light field display with standard lens array, the viewpoint density is increased and the aliasing phenomenon is reduced. In the experiment, the tabletop light-field display based on aspheric conical lens array can present high quality 360-degree viewable 3D image with the right perception and occlusion.

14.1: Invited Paper: Glasses‐free large‐size three‐dimensional light‐field displays

According to Human visual characteristics, glasses‐free 3D light‐field display are analyzed. The optimally designed holographic optical element is used to re‐modulate the light distribution with the 3D spatial information, and the clear 3D light field image is perceived. The real‐time interactive 3D light‐field display with the frame rate above 25 fps is realized. The functions of the holographic functional screen and the complex optical device are integrated, and 65inch 3D light field display with the view angel above 100° and acceptable resolution is demonstrated. 162 inch LED based 3D light‐field displays with the continuous viewing angle above 40° and the acceptable resolution are realized. Touchable aerial imaging based floating 3D light‐field displays with the distance of 90 cm from the screen are also demonstrated. Some applications are also discussed.

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.

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.

Multi-rays computational floating light-field display based on holographic functional screen

A computational light-field display system is designed to realize floating three-dimensional (3D) visual effect. To simulate the natural vision of 3D scene, a multi-rays computational encryption method is proposed to obtain the image which is displayed on the LCD. In the process of encrypting image, N×N light rays are evenly involved in optimization to obtain the value of a pixel. The quality of reconstructed 3D image is correlated to N. As the value of N increases, the sharpness is improved and the ringing artifacts are eliminated. Here, the proposed computational light-field display system based on holographic functional screen (HFS) can provide floating 3D visual effect to observers with high quality. The constructed 3D image has continuously varying viewpoints with 40° viewing angle in horizontal and vertical directions. The displayed depth is more man 20 cm, and the center of the 3D object is on the surface of HFS.

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.

Wide field of view tabletop light field display based on piece-wise tracking and off-axis pickup

A wide field of view (FOV) tabletop light field display (LFD) based on piece-wise tracking and off-axis pickup is presented to display the floating three-dimensional (3D) scene, which is 360°surrounding viewable. The demonstrated LFD is specially designed with an integral imaging display (IID) with 83 × 83 viewpoints and a full-parallax holographic functional screen (HFS). To improve the FOV, a piece-wise tracking based FOV enhancement method is proposed. The relationship between the viewing zone and the elemental images (EIs) is formulated. A ray-tracing based method using off-axis pickup instead of parallel pickup directly is adopted to render the 3D scene to EIs. Then the piece-wise tracking method of varying the viewing zone by placing the EIs according to the position of viewer is analyzed. The floating 3D scene with a FOV of 70°× 70°is experimentally demonstrated with a good 3D perception.