Directional Backlight Research Articles

A novel clinical dynamic stereopsis assessment based on autostereoscopic display system

BackgroundAlthough it is recognized that dynamic stereopsis is vital in daily life, there is still room for improvement in assessment methods. A novel clinical dynamic stereopsis assessment method was created based on an autostereoscopic display system that did not require additional auxiliary glasses. This study evaluated the optical parameters and clinical performance of the autostereoscopic display system for clinical dynamic stereopsis assessment.MethodsThe autostereoscopic dynamic stereopsis assessment device was based on a directional backlight technology. Experiment 1 was performed under the same environmental conditions to compare luminance, crosstalk, and spectrum between the autostereoscopic dynamic stereopsis assessment device and the conventional dynamic random-dot stereopsis measuring instrument. Experiment 2 was an observational, analytic, cross-sectional study involving 135 healthy participants, each of whom was asked to complete measurements on both the autostereoscopic and conventional devices in random order. Stereo acuity, operating time, acceptance, and visual fatigue scores were recorded for clinical evaluation.ResultsThe autostereoscopic device had brighter luminance (139 and 140 cd/m2 for 2 eyes, respectively), lower crosstalk (4.50% for both eyes), and higher color restoration degree than those of the conventional instrument. Clinically, the novel dynamic stereopsis assessment was as accurate as the traditional method [170" (0.00") and 170" (0.00") respectively; P=0.317], and with more efficiency (166±58.9 and 298±116 s, respectively; P<0.001), higher acceptance (3.36±0.93 and 2.02±0.59 points, respectively; P<0.001), lesser fatigue (0.27±0.46 and 0.73±0.66 points, respectively; P<0.001). The autostereoscopic dynamic stereopsis assessment device with brighter luminance, lower crosstalk, and higher color restoration degree was more effective than the traditional instrument at displaying dynamic clues for clinical dynamic stereopsis assessment. Furthermore, its high-quality image and user-friendly interface provided accurate assessment results in all 3 dynamic stereopsis assessment task conditions, with a higher level of acceptance and lesser visual fatigue, than the traditional assessment method.ConclusionsThe autostereoscopic device has excellent functions in both optical parameters and clinical performance, and therefore has the potential to be applied and popularized in future assessments.

P‐65: Autostereoscopic Display for Two Viewers Providing Images Specific to Each Viewpoint

This paper proposes a novel autostereoscopic display with a directional backlight unit using a linear Fresnel lens array. In the proposed system, different stereoscopic image pairs can be provided to each of the two viewers simultaneously, and the viewing zone where two viewers can see the specific views for their own eyes without interfering with each other's view is enlarged.

Multi-user, high-resolution, high-quality directional backlight autostereoscopic display

Autostereoscopy with multi-user, high-resolution, homogeneous luminance, low crosstalk is realized with a directional backlight system consisting of specially tailored backlight and composite Fresnel lens array. Numerical simulation is applied to obtain the viewing zone distribution, which is found to be in good agreement with experiment. The dense-distribution of the backlight array allows the system to provide well-controlled directional illumination for multi-viewers while keeping high-resolution for each viewer. The experimental challenge for small crosstalk between left- and right-eyes for individual viewer, and minimized crosstalk between different viewers are fulfilled with high-quality optics design to allow the multi-viewers to simultaneously perceive 3D image. The crosstalk is controlled below 5%, and the homogeneity is above 85% while the resolution for each eye is kept at 1920*1080.

Integral three-dimensional display system with wide viewing zone and depth range using time-division display and eye-tracking technology

We propose an integral three-dimensional (3D) display system with a wide viewing zone and depth range using a time-division display and eye-tracking technology. In the proposed system, the optical viewing zone (OVZ) is narrowed to a size that only covers an eye to increase the light ray density using a lens array with a long focal length. In addition, a system with low crosstalk with respect to the viewer’s movement is constructed by forming a combined OVZ (COVZ) that covers both eyes through a time-division display. Further, an eye-tracking directional backlight is used to dynamically control the COVZ and realize a wide system viewing zone (SVZ). The luminance unevenness is reduced by partially overlapping two OVZs. The combination of OVZs formed a COVZ with an angle that is ∼1.6 times larger than that of the OVZ, and an SVZ of 81.4 deg and 47.6 deg for the horizontal and vertical directions, respectively, was achieved using the eye-tracking technology. The comparison results of the three types of display systems (i.e., the conventional system, our previously developed system, and our currently proposed system) confirmed that the depth range of the 3D images in the proposed system is wider than that of the other systems.

Backlight system using an interleaved Fresnel lens array that attains a uniform luminance and two-dimensional directional light control.

A novel (to the best of our knowledge) Fresnel lens array is proposed to realize a uniform directional backlight with two-dimensional directionality. Autostereoscopic display with the proposed lens array improves image output quality and relieves the viewer's posture restriction without the need for any additional eye aid. In the proposed lens array, tiny prisms composing two adjacent linear Fresnel lenses are interleaved so that the two lenses may be virtually overlapped and work independently. The widths of the elemental prisms vary depending on the distance from the center of each lens. Thus, the light passing through the two lenses is mixed, which results in higher and more uniform luminance intensity. A prototype of an autostereoscopic display based on the time-multiplexed directional backlight method and made with the proposed lens array attained uniform luminance as well as low cross-talk between left-eye and right-eye images.

Display illumination with modulated directional backlight

AbstractIllumination is essential for modern life as colorful world is perceived by human visionary system. Display technology has been developing rapidly in recent decades, and the basic principle is related to the way that the image is illuminated and light is emanated. Traditional illumination is provided by different types of light sources, and the display image is visible in large viewing space until the emanating light decays to zero. This work proposes and demonstrates a novel illumination scheme for a display in which the displaying images are visible only in specific spatial regions. The directional backlight ensures the image propagating to specific direction while imaging visibility can be controlled to terminate abruptly at certain distance from the display screen while exerting no influence to nearby regions. The working principle for such an illumination scheme is the use of the modulated coherent directional backlight through an axicon lens. It is shown that the illumination scheme can robustly deliver carried image information to the designated viewing region. This new illumination scheme has many advantages over conventional illumination, including its usage for personal display, very lower energy consumption, as well as minimizing light hazard pollution.

P‐8.2: Display Illumination with Modulated Directional Backlight

P‐8.2: Display Illumination with Modulated Directional Backlight

Doubling the optical efficiency of VR systems with a directional backlight and a diffractive deflection film.

We demonstrate an approach to double the optical efficiency of virtual reality (VR) systems based on a directional backlight and a diffractive deflection film (DDF). The directional backlight consists of a commercial collimated light-emitting diode (LED) array and a two-layer privacy film, while the DDF is a three-domain Pancharatnam-Berry (PB) phase lens. Such a PB phase lens was fabricated by the zone exposure and spin-coating method. The focal length of each domain is designed according to the imaging optics of the VR system. Our approach works well in both Fresnel and "pancake" VR systems. We also build the corresponding models in LightTools, and the simulation results are in good agreement with experiment. In experiment, we achieved a 2.25x optical efficiency enhancement for both systems, which agrees with the simulation results (2.48x for Fresnel and 2.44x for "pancake" systems) well. Potential application for high efficiency VR displays is foreseeable.

Autostereoscopic display for multiviewers positioned at different distances using time-multiplexed layered directional backlight.

In this paper, an autostereoscopic display system based on a time-multiplexed directional backlight using a large aperture Fresnel lens is proposed. High-resolution stereoscopy for multiple viewers positioned at different distances from the screen is achieved in the proposed system by layering polymer dispersed liquid crystal screens behind the Fresnel lens. The screens with segmented electrodes are electrically controlled to change the position of light diffusion, while the time-multiplexed backlight is projected by a digital mirror device projector at a high refresh rate. The light is diffused at the conjugate focal points of the observers' eyes to deliver directional light to each eye. The right-eye image and the left-eye image are alternated on the LCD panel in front of the lens to synchronize with the backlight.

Paper] Autostereoscopic Displays with Time-multiplexed Directional Backlight Using Curved Lens Arrays

Paper] Autostereoscopic Displays with Time-multiplexed Directional Backlight Using Curved Lens Arrays

Space-division-multiplexed catadioptric integrated backlight and symmetrical triplet-compound lenticular array based on ORM criterion for 90-degree viewing angle and low-crosstalk directional backlight 3D light-field display.

A novel optical reverse mapping (ORM) method and an ORM criterion are proposed to evaluate the relevance between the directional backlight (DB) 3D light-field display system aberration and the crosstalk. Based on the ORM criterion, the space-division-multiplexed catadioptric integrated backlight (SCIB) and symmetrical triplet-compound lenticular array (triplet LA) are designed. The SCIB is composed of hybrid Fresnel integrated backlight unit (hybrid Fresnel unit) and space-division-multiplexed microprism unit (microprism unit). The hybrid Fresnel unit is used to provide the directional light, and the divergence angle is 2.4-degrees. The average uniformity of 83.02% is achieved. The microprism unit is used to modulate the directional light distribution into three predetermined directions to establish a 90-degree viewing area. Combined with SCIB, the triplet LA is used to suppress the aberrations and reduce the crosstalk. In the experiment, a DB 3D light-field display system based on SCIB and triplet LA is set up. The displayed light-field 3D image can be observed in a 90-degree viewing angle. Compared to the conventional DB 3D display system, the light-field 3D image is aberration-suppressed, and the SSIM values are improved from 0.8462 to 0.9618. Meanwhile, the crosstalk measurement results show that the average crosstalk is 3.49%. The minimum crosstalk is 2.31% and the maximum crosstalk is 4.52%. The crosstalk values in 90-degree are lower than 5%.

Holographic optics for thin and lightweight virtual reality

We present a class of display designs combining holographic optics, directional backlighting, laser illumination, and polarization-based optical folding to achieve thin, lightweight, and high performance near-eye displays for virtual reality. Several design alternatives are proposed, compared, and experimentally validated as prototypes. Using only thin, flat films as optical components, we demonstrate VR displays with thicknesses of less than 9 mm, fields of view of over 90° horizontally, and form factors approaching sunglasses. In a benchtop form factor, we also demonstrate a full color display using wavelength-multiplexed holographic lenses that uses laser illumination to provide a large gamut and highly saturated color. We show experimentally that our designs support resolutions expected of modern VR headsets and can scale to human visual acuity limits. Current limitations are identified, and we discuss challenges to obtain full practicality.

P‐72: An Autostereoscopic Display with a Deep Viewing Zone Using Time‐Multiplexed Directional Backlight

We propose a high‐resolution autostereoscopic display that has a deep viewing zone based on time‐multiplexed directional backlight using a large aperture Fresnel lens. When the distance of a viewer from the display changes, the depth of light source should be changed to avoid stereoscopic crosstalk. By combining a DMD projector with layered PDLC screens, the depth of the light source is electronically changed to follow the viewer's motion, which expands the viewing zone in the depth direction.

68‐2: View‐Dependent Light‐Field Display that Supports Accommodation Using a Commercially‐Available High Pixel Density LCD Panel

Super multiview displays generally support only a small range of viewpoints. We describe a view‐dependent light‐field display approach that combines custom optics, eye position tracking, a high‐density display and a directional backlight to provide full parallax and a 3D volume from which a viewer can see 3D objects with accommodation.

Large viewing angle floating three-dimensional light field display based on the spatial data reconstruction (SDR) algorithm

A large viewing angle floating three-dimensional (3D) light field display based on spatial data reconstruction (SDR) algorithm is presented. It consists of the 3D light field display unit (LFDU) and the floating display unit (FDU). With the time-sequential directional backlight system, LFDU can provide 3D scenes with a large viewing angle in the horizontal direction. Based on FDU, the floating display has a large off-screen display depth, and the SDR algorithm is introduced to improve the 3D image quality. Combining the SDR algorithm with the time-sequential directional backlight system, a large viewing angle and image quality enhanced floating 3D light field display is realized. For the demonstrated floating 3D light field system, the floating 3D images can be reconstructed by the optical system within the viewing angle of 60 degrees. The feasibility of the proposed display method is verified with experimental results.

Adaptive glasses-free 3D display with extended continuous viewing volume by dynamically configured directional backlight

It is highly challenging for the available glasses-free 3D display to simultaneously possess the advantages of viewing freedom, homogeneous illuminance, high resolution and low crosstalk. This work proposes and demonstrates a directional backlight autostereoscopic display having these advantages with a substantially extended viewing volume and densely packed viewpoints. Low crosstalk and homogeneous illuminance are obtained using dynamically configured directional backlight, realized by a novel system design, in conjunction with viewer’s eye tracking and subsequent backlight control scenario. The autostereoscopy allows the viewers to move around continuously, while the illuminance homogeneity on the screen, high panel resolution and low crosstalk between the left and right eyes are realized, providing high-quality glasses-free 3D display with satisfying viewing experience.

Compact auto-stereoscopic display based on directional backlight using side-glowing polymer optical fiber array

A compact directional backlight module of time-multiplexed auto-stereoscopic display based on side-glowing polymer optical fiber (SGPOF) is proposed. The optical system is mainly composed of SGPOF array and cylindrical lens array. Spatial crosstalk is reduced by inserting a grating film as multi-slit diaphragm between the SGPOF array and the cylindrical lens array. A theoretical model is constructed based on the imaging optics principle of the off-axis ray. In the experiments, the cylindrical lens array concentrates a small number of views on three different view zones, the display can provide high luminance. The measurement results show that the luminance uniformity of the backlight module is up to 89.6%, and in the viewing zone the crosstalk is lower than 10%. The backlight module is compacted that the thickness being only 7 mm. The full-resolution and low-crosstalk 3D images are realized by using SGPOF backlight.

Demonstration of a large viewing angle and high-resolution floating three-dimensional display based on the multichannel and multivariable correction algorithm

Floating three-dimensional (3-D) display can provide a natural and realistic 3-D scene. Nowadays, because of stray light and aberration, most floating 3-D displays cannot realize a large viewing angle and high resolution simultaneously, and it directly deteriorates the viewing effect of the 3-D scene. A large viewing angle floating and high-resolution 3-D display based on multichannel and multivariable (MCMV) correction algorithm are presented. The optical system consists of a time-sequential autostereoscopic 3-D display with the directional backlight, a floating lens, and an eye tracker. The 3-D display with the directional backlight provides loss-free resolution for the system. To realize a large viewing angle floating 3-D display, MCMV correction algorithm based on eye tracking is proposed. The 3-D images can be reconstructed by the optical system within the viewing angle of 60 deg. The feasibility of the proposed display method is verified with the experimental results.

Directional backlight module based on pixelated nano-gratings

A directional backlight is of great interest in the field of glasses-free 3D display, privacy display, and energy efficient display. In this paper, a directional backlight module including a LED light bar, a collimating lens, a diffuser, and a waveguide is proposed. The waveguide is covered by nanogratings with a density gradience to optimize the illumination uniformity and to preserve the angular divergence of the emitted light. The proposed directional backlight achieved a divergence angle of ±6.17° and a uniformity of 88%. The directional backlight based on pixelated nanogratings features good uniformity, thin form factor, low cost, and large tolerance of the fabrication process, thus can be used in the illumination of glass-free 3D display, privacy display, and energy efficient display.

Wide color gamut switchable autostereoscopic 3D display based on directional quantum-dot backlight**Project supported by the National Key R&D Program of China (Grant No. 2016YFB0401503) and the R&D Plan of Jiangsu Science and Technology Department, China (Grant No. BE2016173).

A switchable autostereoscopic 3-dimensional (3D) display device with wide color gamut is introduced in this paper. In conjunction with a novel directional quantum-dot (QD) backlight, the precise scanning control strategy, and the eye-tracking system, this spatial-sequential solution enables our autostereoscopic display to combine all the advantages of full resolution, wide color gamut, low crosstalk, and switchable 2D/3D. And also, we fabricated an autostereoscopic display prototype and demonstrated its performances effectively. The results indicate that our system can both break the limitation of viewing position and provide high-quality 3D images. We present two working modes in this system. In the spatial-sequential mode, the crosstalk is about 6%. In the time-multiplexed mode, the viewer should wear auxiliary and the crosstalk is about 1%, just next to that of a commercial 3D display (BENQ XL2707-B and View Sonic VX2268WM). Additionally, our system is also completely compatible with active shutter glasses and its 3D resolution is same as its 2D resolution. Because of the excellent properties of the QD material, the color gamut can be widely extended to 77.98% according to the ITU-R recommendation BT.2020 (Rec.2020).