360°‐viewable cylindrical integral imaging system using a 3‐D/2‐D switchable and flexible backlight

Abstract— A 360°‐viewable cylindrical three‐dimensional (3‐D) display system based on integral imaging has been implemented. The proposed system is composed of a cylindrically arranged electroluminescent (EL) pinhole film, an EL film backlight, a barrier structure, and a transmission‐type flexible display panel. The cylindrically arranged point‐light‐source array, which is generated by the EL pinhole film reconstructs 360°‐viewable virtual 3‐D images at the center of the cylinder. In addition, the proposed system provides 3‐D/2‐D convertibility using the switching of EL pinhole film from a point light source to a surface light source. In this paper, the principle of operation, analysis of the viewing parameters, and the experimental results are presented.     

Nonuniform viewing angle of integral imaging display

While the viewing angle (VA) is an important parameter of three‐dimensional (3‐D) displays, a method has not yet been devised to determine the VA. We proposed a new approach to determine a VA of an integral imaging display. An integrated point appears at the cross section between collected rays and a lens array; the VA of the integrated point is thus equal to the angle between the two farthest rays. This approach is useful to determine the VA of all 3‐D displays, because a 3‐D point appears in the cross section of collected rays. The result of this study showed that the VA depends on the position of the integrated point and is smaller than the VA of the conventional calculation.     

Depth‐ and viewing‐angle‐enhanced 3‐D/2‐D switchable display system with high contrast ratio using multiple display devices and a lens array

Abstract— An improved 3‐D/2‐D switchable display system with enhanced depth and viewing angle by adding two LCD panels to an integral imaging system has been realized. The proposed system uses the see‐through property of an LCD panel and displays multiple sets of elemental images on the LCD panels to integrate them on multiple locations simultaneously. As a result, the depth of the 3‐D image can be enhanced. For wide viewing angles, the time‐multiplexing method was adopted by displaying mask patterns on the front LCD panel. In addition, another technique to increase the contrast ratio of the proposed system has also been developed. Some experimental results will be provided.     

Fabrication of pinhole/micro‐lens array for improving resolution of integral imaging 3‐D display

In this paper, we present a new fabrication of micro‐lens array (MLA) with pinhole array—pinhole/micro‐lens array (P/MLA) for integral imaging 3‐D display (II), which combine lithography and ink‐jet printing. A black circular groove array (BCGA) is used as pinhole array, and laser 3‐D microscope and a homemade setup have been used for the characterization of P/MLA. The results show that high‐precision P/MLA can be obtained using BCGA as templates. By controlling the driving voltage at different steps, the distance between nozzle and substrate, as well as the number of liquid droplets, P/MLA with smooth morphology, different sizes, good repeatability of geometry parameters, great uniformity of focusing, and good converging performance can be achieved. For demonstration, P/MLA with curvature, focal length, numerical aperture, and F‐number of 815.8 μm, 1.60 mm, 0.1311, and 3.8 are applied for the reconstruction in II, exhibiting good reconstruction performance with high resolution, and BCGA reduces the influence of stray light on II and improves the quality of the reconstructed image.     

Accommodation and convergence in integral imaging 3D display

In this paper, we analyze the visual fatigue of integral imaging three‐dimensional (3D) display by studying the accommodation and convergence when viewing the integral imaging 3D images. The theoretical analyses show that there is no inconsistency between the accommodation and convergence distances, which means that the integral imaging 3D display has no visual fatigue. Experiments are implemented, and the results finally demonstrate the rationality of the theoretical analyses. These analyses can be quite beneficial for researchers to better understand the performances and promote the practical applications of the integral imaging 3D display.     

Enhanced depth of field of integral imaging display using bifocal microlens array fabricated by two-step lithography

Due to the limitation of traditional microlens arrays (MLAs) in integral imaging display, the depth of field (DOF) is restricted in space and the center depth plane is difficult to extend in a large range. Here, we propose a microfabrication method based on bifocal MLAs to improve DOF. The bifocal MLAs for extended DOF were fabricated by using two-step photolithography and thermal reflow. This method allows diverse microlenses of high to low numerical aperture to achieve high spatial resolution as well as accurate depth estimation. Microlenses of different focal lengths were simultaneously deposited on a substrate by repeated photolithography with multiple photomasks with alignment mark to define micro-posts of different thicknesses. Hexagonally packaged bifocal MLAs clearly show the DOF extended from 0.004 to 4.908 mm for 57.6 μm in lens diameter, and their corresponding object distance ranges from 0.125 to 0.165 mm. Based on the proposed scheme, this method provides potential applications in integral imaging 3D display or light field display.     

Depth‐enhanced integral‐imaging 3D display using different optical path lengths by polarization devices or mirror barrier array

Abstract— Depth‐enhanced integral three‐dimensional (3D) imaging using different optical path lengths by using a polarization selective mirror pair or mirror barrier array is proposed. In the proposed approach, the enhancement of image depth is achieved by repositioning two types of elemental image planes, thus effectively two central depth planes are obtained. One of the two implementation methods makes use of the two‐arm structure that has different optical path lengths and polarization‐selective mirrors. The other utilizes the mirror barrier array. The primary advantage of the method with polarization devices is that we can observe 3D images that maintain some level of viewing resolution with a large depth difference without any mechanical moving part. The mirror barrier array has the advantage of the compact thickness. We demonstrated and verified our proposals experimentally.     

Dual‐lenticular‐lens‐based 2‐D/3‐D convertible autostereoscopic display

Abstract— A 2‐D/3‐D convertible display using two lenticular lenses has been developed. It shows 2‐D pictures in full resolution and 3‐D autostereoscopic pictures in half resolution by moving one lens relative to the other. The lens assembly consists of thin metal frames, two lenticular lenses, and two shape‐memory‐alloy (SMA) wires used as actuators. While this assembly is applicable to flat‐panel displays of any kind, its simple structure and low power consumption make it best suited to mobile terminals, such as PDAs and mobile phones. Here, we describe its structure and present evaluation results.     

High‐quality direct‐view display combining multiple integral 3D images

This paper proposes a method for combining multiple integral three‐dimensional (3D) images using direct‐view displays to obtain high‐quality results. A multi‐image combining optical system (MICOS) is used to enlarge and combine multiple integral 3D images without gaps. An optical design with a simple lens configuration that does not require a diffuser plate prevents the deterioration in resolution resulting from lens arrangement errors and the diffuser plate. An experiment was performed to compare a previously developed method with the proposed method, and the latter showed a significant improvement in image quality. A method for expanding the effective viewing angle of the proposed optical design was also developed, and its effectiveness was confirmed experimentally. A prototype device of the proposed optical design was constructed using a high‐density organic light‐emitting diode (OLED) panel with 8K resolution and 1058 ppi pixel density to achieve 311 (H) × 175 (V) elemental images, a viewing angle of 20.6° in both the horizontal and vertical directions, and a display size of 9.1 in. In addition, the proposed optical design enabled making device considerably thinner, ie, with a thickness of only 47 mm.     

Practical implementation of a depth‐feeling‐enhanced two‐plane electro‐floating display system using three‐dimensional integral images

Abstract— Although there are numerous types of floating‐image display systems which can project three‐dimensional (3‐D) images into real space through a convex lens or a concave mirror, most of them provide only one image plane in space to the observer; therefore, they lack an in‐depth feeling. In order to enhance a real 3‐D feeling of floating images, a multi‐plane floating display is required. In this paper, a novel two‐plane electro‐floating display system using 3‐D integral images is proposed. One plane for the object image is provided by an electro‐floating display system, and the other plane for the background image is provided with the 3‐D integral imaging system. Consequently, the proposed two‐plane electro‐floating display system, having a 3‐D background, can provide floated images in front of background integral images resulting in a different perspective to the observer. To show the usefulness of the proposed system, experiments were carried out and their results are presented. In addition, the prototype was practically implemented and successfully tested.     

Switching directional BLUs for full‐resolution auto‐stereoscopic 3D/2D and 2D/3D LCDs

Directional backlight unit (BLU) design concept was applied to realize full‐resolution field alternate auto‐stereoscopic liquid crystal displays (LCDs) with built‐in 3D/2D and 2D/3D. The application‐oriented BLU design requires priority in realizing 2D mode or 3D mode. The switching characteristic of BLU with two confronting illuminating sets was applied to build 2D mode into 3D display and 3D mode into 2D display. An LCD with 2D mode as primary function requires higher double‐sided luminance uniformity than 3D mode. On the other hand, an LCD with 3D mode requires higher single‐sided luminance uniformity than 2D mode. For increasing the double‐sided luminance uniformity for 2D mode as a primary function of the display, the former BLU design was realized by using uniform prismatic structure, that is, using uniform bilateral prismatic structure with a cross section of isosceles triangle on the back surface of the light‐guide plate. For increasing single‐sided luminance uniformity for 3D mode as a primary function of the display, the latter was realized by using graded angle design, that is, unilateral prisms with a cross section of a scalene triangle on the back surface of the light‐guide plate. The LCDs of small‐sized‐handheld game devices and still cameras were fabricated using the 3D/2D and 2D/3D displays.     

Stereoscopic 3‐D display with optical correction for the reduction of the discrepancy between accommodation and convergence

Abstract— This paper describes a method for reducing the discrepancy between accommodation and convergence when viewing stereoscopic 3‐D images. The method uses a newly developed stereoscopic 3‐D display system with a telecentric optical system and a mobile LCD. The examination of a mono‐focal lens showed that a correction lens having the appropriate refractive power and conditions for presenting stereoscopic 3‐D images clearly reduces the discrepancy between accommodation and convergence. The authors also developed a stereoscopic 3‐D display that uses dynamic optical correction to reduce the discrepancy between accommodation and convergence. The display equalizes the theoretical points of accommodation and convergence. The purpose of the development was to expand the regeneration range of a stereoscopic 3‐D image having the appropriate accommodation. An evaluation of the developed display showed that it resolves the discrepancy between convergence and accommodation.     

Tabletop integral imaging 3D display system based on annular point light source

When the viewers sitting around the table observe 3D images, the viewing direction is generally oblique and the viewpoints should be distributed as annular. In this paper, a tabletop integral imaging (II) three-dimensional (3D) display system based on annular point light sources is demonstrated, which can present 3D images to multiple viewers in a standard annular viewing area with oblique viewing direction. The proposed system consists of annular point light sources, a Fresnel lens, a lens array, a two-dimensional (2D) display panel, and a diffuser screen. Each point light source illuminates the Fresnel lens to form parallel light and then illuminates the lens array and the display panel. A viewing sub-area is generated at the position of the diffuser screen, in which the 3D images can be viewed. Multiple viewing sub-areas are created in a way of time-division multiplexing to form a 360° annular viewing area. Compared with the previous tabletop 3D display, the viewing area can be concentrated at an oblique angle near the tabletop. The experimental results demonstrate the feasibility of the tabletop II 3D display system.     

Development of a 42‐in. 2‐D/3‐D switchable display using multi‐view technology for public‐information‐display applications

Abstract— A 42‐in. 2‐D/3‐D switchable display operating in a parallax‐barrier‐type system consisting of liquid‐crystal displays (LCDs) has been developed. The system displays 2‐D images in full resolution, without any degradation to the original 2‐D images, and 3‐D autostereoscopic images with resolutions higher than SVGA with wide viewing zones electrically controlled by the parallax‐barrier system. The system is intended for use in public‐information displays (PIDs), a booming field, and as displays for gaming, medical, and simulation applications.     

A high resolution multi‐view 3D display using switchable liquid crystal lens

A 4.4‐inch 2D/3D switchable full high definition (FHD) six‐view 3D display with 3D resolution greater than 170 ppi has been accomplished. In addition to adopting low temperature polysilicon technology (LTPS), which is most suitable for high resolution displays, a new RGBW pixel arrangement using four‐square sub‐pixels has been devised. In 2D, a resolution greater than 500 ppi, accompanied with high luminance, has been achieved. A new liquid crystal lens (LCL) has been exploited for 2D/3D switching. By employing a special multielectrode structure and dedicated manufacturing process, an optical focal ratio less than 20%, which is essential for low 3D cross talk for a six‐view 3D display, has been attained by adopting the LCL. In the vertical direction of the display, there is no cross talk increase when the viewing position is changed because of the new pixel structure. The strong focal strength of the LCL combined with a revised high‐density multi‐view design give rise to a wide 3D viewing angle greater than 20 degrees in the horizontal direction and minimum cross talk less than 10%.     

Curved OLED display to effectively enhance natural3D

We studied the stereoscopic effect obtained from a two‐dimensional image without using binocular parallax, which we call “natural3D” (n3D). Unlike a parallax‐based three‐dimensional (3D) display system, n3D causes less tiredness and is free from a decrease of the resolution by half because of image division and viewing position dependence. To make the display with these effects comfortable to use, we conducted statistical tests with sensory evaluation experiments and a quantitative evaluation based on physiological responses. These examinations revealed that the n3D effect can be effectively obtained by using, for example, the characteristics of an organic light‐emitting diode display, such as high contrast and easy bendability. This study discusses optimal display curvatures for displays of different sizes that enhance n3D and reduce tiredness, which are revealed through statistical tests. In addition, we performed an experiment with a frame called an n3D window (n3Dw) that is placed before the display such that a subject views the display through the opening of the frame. We found that the combination of a curve and the n3Dw causes n3D more effectively.     

Bare finger 3D air‐touch system with embedded multiwavelength optical sensor arrays for mobile 3D displays

A camera‐free 3D air‐touch system was proposed. Hovering, air swiping, and 3D gestures for further interaction with the floated 3D images on the mobile display were demonstrated. By embedding multiwavelength optical sensors into the display pixels and adding angular‐scanning illuminators with multiwavelength on the edge of the display, the flat panel can sense images reflected by a bare finger from different heights. In addition, three axis (x, y, z) information of the reflected image of the fingertip can be calculated. Finally, the proposed 3D air‐touch system was successfully demonstrated on a 4‐inch mobile 3D display.     

Distributed real-time rendering for ultrahigh-resolution multiscreen 3D display

Large-scale autostereoscopic three-dimensional (3D) displays can give audiences a truly immersive feeling with strong visual impact. However, the traditional autostereoscopic 3D display systems are limited by the display hardware, making it difficult to directly achieve large-scale 3D displays with high resolution. Multiscreen splicing with laser backlights can be used for large-scale and ultrahigh-resolution 3D display, but it normally results in subscreen image asynchronization, view zone error, or obvious edge overlapping. To solve the problems mentioned above, a distributed real-time rendering system for ultrahigh-resolution multiscreen 3D display is proposed. Fifteen 3D LCD display devices are driven through a host, cooperating with laser backlights, a lenticular lens array (LLA), and a directional diffuser to display high resolution, high frame rate, large size, and wide-viewing angle 3D images. The resolution of the whole display system can reach 23,040 × 21,600. The rendering system provides a large-scale and real-time 3D scene image with an ultrahigh-definition resolution at a speed of 40 frames per second and high quality.     

Integral floating‐image display using two lenses with reduced distortion and enhanced depth

Abstract— An integral floating display (IFD) with a long depth range without floating lens distortion is proposed. Two lenses were used to reduce barrel distortion of the floating lens and three‐dimensional (3‐D) image deformation from object‐dependent longitudinal and lateral magnifications in the floating‐display system, combined with an integral imaging display. The distance between the floating lenses is the sum of their focal lengths. In the proposed configuration, lateral and longitudinal magnifications are constant regardless of the distance of the integrated 3‐D images, so the distortions from the distant‐dependent magnifications of the floating lens do not occur with the proposed method. In addition, the proposed floating system expands the depth range of the integral imaging display. As a result, the display can show a correct 3‐D floating image with a large depth range. Experimental results demonstrate that the proposed method successfully displays a 3‐D image without floating lens distortions across a large depth range.