Point Light Source Array Research Articles

Slim Maxwellian Near-Eye Display for Virtual Reality Using Point Light Source Array

Slim Maxwellian Near-Eye Display for Virtual Reality Using Point Light Source Array

High-Aperture-Ratio Dual-View Integral Imaging Display.

Low aperture ratio is a problem in the conventional dual-view integral imaging (DVII) display using a point light source array. A high-aperture-ratio DVII display using a gradient width point light source array is reported in this work. The elemental Images 1 and 2, which are alternatively aligned on a liquid crystal panel, are illuminated by the light rays emitted from an assigned point light source. The optical path is optimized by optimizing the widths of the point light sources. The aperture ratio of the proposed DVII display was demonstrated as 1.88 times the conventional DVII display. Experiments showed that the vertical viewing range is related to the vertical width of the first row point light source, whereas the aperture ratio is related to the vertical widths of all point light sources. By optimizing the widths of the point light sources, the aperture ratio is enhanced without loss of viewing range.

20.2: 2D/3D Mixed Display Based on Polarization Division Multiplexing

We propose a two‐dimensional (2D)/ three‐dimensional (3D) mixed display system based on polarization division multiplexing. The polarization division multiplexing device is composed of a polarization switching layer, a polarization‐dependent liquid crystal micro‐lens array (LCMLA) and a scattering polarizer. According to the polarization state of incident light switched by the polarization switching layer, the combined action of polarization‐dependent LCMLA and scattering polarizer can form both point light source array for 3D display and scattered light source for 2D display. The 2D/3D mixed images can be reconstructed through the precise control of the polarization direction of each pixel. The advantage of the proposed system is that a point light source array and a surface light source are formed only by adjusting the state of the polarization switching layer. What's more, our proposed system has low driving voltage and relatively compact system volume.

Integral 3D/2D partially convertible display using geometric phase lens array

Conversion between three-dimensional (3D) and high-definition two-dimensional (2D) images is required to reproduce various video content. Conventional 3D/2D conversion methods based on integral 3D displays mainly aim to convert between 3D and 2D images on the entire display screen. Here, we propose a display method for partial conversion between 3D and 2D images using a geometric phase lens (GPL) array for the backlight control of a liquid crystal (LC) panel. In our method, the backlight is switched between a point light source (PLS) array and diffused light using a GPL array, diffusion plate, and polarization switching element. Integral 3D and high-definition 2D images are simultaneously reproduced on the same screen by displaying elemental images and 2D images on the LC panel according to the state of the backlight. Through numerical simulation experiments, we analyzed the resolution characteristics of 3D images and obtained the design policy of the PLS size and pixel size of the LC panel. Based on the analysis results, we prototyped a display system using a monochromatic LC panel with 8K resolution and evaluated the quality of backlight switching and resolution characteristics of 3D images. Further, we confirmed that 3D images with approximately 16,000 pixels and 2D images with 8K resolution are partially convertible.

360°tabletop floating integral imaging based on spatiotemporal perspective-oriented projecting

Traditional integral imaging (InIm) display fails to effectively support practical 360°tabletop three-dimensional (3D) display, although this method is commonly used as the ideal wall 3D display to exhibit realistic 3D image with correct geometric occlusion. The reason is that the distribution of the viewing zone is omnidirectional, and finite recovered 3D spatial information distributed in the viewing area right above the screen is fully wasted when the traditional InIm display is used as the tabletop display. To address this issue, a 360°tabletop floating InIm display with cylinder-typed viewing zone, instead of the omnidirectional viewing zone, is demonstrated with high utilization rate of the recovered 3D spatial information. A point light source array (PLSA) based integral imaging using the aberration-suppressed biconvex aspheric lens array (BALA) and the directional collimated backlight (DC-BL) is presented and configured to realize the perspective-oriented projecting with a large viewing angle. Meanwhile, the cylinder-typed viewing zone is formed by implementing perspective-oriented projecting with spatiotemporal multiplexing by the use of FGPA and rotating mechanism. Additionally, a novel spatial coding method for 3D light field reconstruction is proposed to guarantee the right spatial perception and occlusion effect with full smooth parallax property within the whole viewing zone. In the experiment, the proposed tabletop display prototype using a 12.5-inch high frame-rate LCD panel with the resolution of 1920 × 1080 presents natural tabletop 3D images with 79 × 79 viewpoints and clear floating focus depth of 18 cm in 360°cylinder-typed viewing zone.

Viewing-angle and viewing-resolution enhanced integral imaging based on time-multiplexed lens stitching.

A method for the viewing angle and viewing resolution enhancement of integral imaging (InIm) based on time-multiplexed lens stitching is demonstrated using the directional time-sequential backlight (DTS-BL) and the compound lens-array. In order to increase the lens-pitch of the compound lens-array for enlarging the viewing angle of InIm, DTS-BL is used to continuously stitch the adjacent elemental lenses in the time-multiplexed way. Through the compound lens-array with two pieces of lens in each lens unit, the parallel light beams from the DTS-BL converge and form a uniformly distributed dense point light source array (PLSA). Light rays emitting from the PLSA are modulated by the liquid crystal display (LCD) panel and then integrated as volumetric pixels of the reconstructed three-dimensional (3D) image. Meanwhile, time-multiplexed generation of the point light sources (PLSs) in the array is realized by time-multiplexed lens stitching implemented with the DTS-BL. As a result, the number of the PLSs, as the pixels of the perceived 3D image, is increased and then the viewing resolution of the 3D image is obviously enhanced. Additionally, joint optical optimization for the DTS-BL and the compound lens-array is used for suppressing the aberrations, and the imaging distortion can be decreased to 0.23% from 5.80%. In the experiment, a floating full-parallax 3D light-field image can be perceived with 4 times the viewing resolution enhancement in the viewing angle of 50°, where 7056 viewpoints are presented.

Flat-Panel See-Through Three-Dimensional Display Based on Integral Imaging Using a Transparent Polarized Point Light Source Array

This study proposes a technique to implement see-through three-dimensional (3-D) display based on point light source integral imaging. This display consists of an edge-lit light guide plate, a polarizer array, and a transparent liquid crystal display (LCD) panel without rear polarizer. The combination of the light guide plate and the polarizer array act as a transparent polarized point light source array (PLSA), and reconstructs the 3-D image with the elemental image array loaded on the LCD panel. The background rays passing through the gaps in the polarized PLSA carry the object information and implement see-through property. The experimental system is constructed based on 1-D integral imaging to verify the proposed method. The see-through and superposition capabilities of the proposed method are demonstrated.

Integral Imaging System using Locally Controllable Point Light Source Array

Integral Imaging System using Locally Controllable Point Light Source Array

A high optical efficiency 3D/2D convertible integral imaging display

We propose a high optical efficiency three-dimensional (3D)/two-dimensional (2D) convertible integral imaging display by using a pinhole array on a reflective polarizer. The 3D mode is realized by adopting a pinhole array on a reflective polarizer to generate a point light source array. Three-dimensional/2D convertible feature is realized by electrically controlling a polarization switcher. The reflective polarizer can reflect the light that has the orthogonal polarization direction with the reflective polarizer and transmit the light that has the same polarization direction with the reflective polarizer. The reflected light is recycled, so the optical efficiencies for both 3D and 2D modes are enhanced. In the practical experiments, the optical efficiencies of the proposed integral imaging display increase by 8.04 times and 1.65 times in 3D and 2D modes comparing with the conventional integral imaging display that has no light recycle, respectively.

High Optical Efficiency Lensless 2D-3D Convertible Integral Imaging Display Using an Edge-lit Light Guide Plate

A thin two-dimensional (2D)/(3D) convertible integral imaging display using an edge-lit light guide plate (LGP) is proposed with improved optical efficiency. The proposed system is composed of an ordinary flat backlight, an edge-lit LGP, and a liquid crystal display panel. The edge-lit LGP is an acrylic sheet edge illuminated with light-emitting diodes (LEDs), and there is a diffuser dot array at the bottom. A point light source array for 3D mode is created by the LGP. The light rays from each point light source are modulated by each elemental image to integrate 3D images. In 2D mode, the flat backlight behind the transparent LGP is turned on while edge-lit LEDs are turned off at the meantime. The 2D and the 3D display modes can be simply switched from one to another by turning on different light sources. The explanation of the proposed system is provided and the experimental results are also presented.

Cross-talk-free integral imaging three-dimensional display based on a pyramid pinhole array

We propose a cross-talk-free integral imaging 3D display based on a pyramid pinhole array. The pyramid pinhole array is used to provide a point light source array. Since the generated point light source array is behind a transmission-type display panel that displays an elemental image array, the pseudoscopic problem can be resolved. By setting the appropriate parameters for the pyramid pinhole array, the cross talk can be eliminated. We experimentally verify the reconstruction of the orthoscopic and cross-talk-free 3D images using the proposed 3D display.

P‐71: A 3D/2D Convertible Integral Imaging Display with High Optical Efficiency

We propose a method for highopticalefficiency three‐dimensional (3D)/ two‐dimensional (2D) convertible integral imaging display. A reflective polarizer can reflect the polarized light which is orthogonal to the transmission axis of the reflective polarizer and transmit the polarized light which is paralleled to the transmission axis of the reflective polarizer. The reflected light can be recycled because of the depolarization property of the diffuser, sothe optical efficienciesfor both 3D and 2D display modesare enhanced. 3D display mode is realized byadopting a pinhole array on a polarizer to generate point light source array. 3D/2D convertible feature is realized by electrically controlling the polarization switcher. In the experiments, the 3D/2D conversion and the improvement of the optical efficiency are demonstrated.

2D/3D Convertible Integral Imaging Display Using Point Light Source Array Instrumented by Polarization Selective Scattering Film

A two-dimensional (2D) / three-dimensional (3D) convertible display system based on integral imaging is proposed to adopt a novel switchable point light source array, which is implemented using the polarization modulator and the polarization selective scattering film that transmits or scatters the incident light due to its polarization direction. The 2D and the 3D display modes of the proposed system can be modulated by controlling the polarization direction of back light using the polarization modulator. We explain the basic principles of the proposed system and verify the feasibility of the system through preliminary experiments.

41.1: Viewing Direction Controllable Three‐Dimensional Display Based on Integral Imaging

AbstractA novel method to control the viewing direction of the integral imaging based three‐dimensional display using the 4‐f illumination optics is proposed. Based on integral imaging principle, the light from the point light source array is modulated by the spatial light modulator, displaying three‐dimensional images. The viewing direction of the three‐dimensional image is determined by the diverging direction of the light emanating from each relayed point light source. In the proposed method, a 4‐f optics with a dynamic aperture in the Fourier plane relays the point light source array to the spatial light modulator. The dynamic aperture acts as a band‐pass filter in the Fourier plane, effectively controlling the diverging direction of the light from the point light sources. Resultantly, the proposed system can control the viewing direction of the three‐dimensional image dynamically. The proposed method can be combined with the head tracking system, providing the three‐dimensional image over large viewing angles.

Integral imaging system using an electroluminescent film backlight for three-dimensional-two-dimensional convertibility and a curved structure

We propose a thin and compact integral imaging system using electroluminescent (EL) films as backlight. EL film has the advantage that it can operate continuously even when it is cut or punctured. Using this characteristic, we generate an array of pinholes on EL film to form a point light-source array for reconstructing three-dimensional (3D) images based on integral imaging. The EL pinhole film is attached on another EL film and they are electrically controlled to generate a point light-source array or a surface light source; hence, the system converts between 3D and two-dimensional (2D) modes. Taking advantage of the flexibility of EL films, we also propose a flexible 3D/2D convertible integral imaging system with a wide viewing angle using a curved EL film. We explain the principle of the proposed methods and present experimental results.

Thin-type integral imaging method with an organic light emitting diode panel

A thin and lensless two-dimensional (2D) to three-dimensional (3D) convertible display based on integral imaging using an organic light emitting diode (OLED) panel as a direct emissive light source is proposed with improved optical efficiency. A point light source array for 2D-3D convertible display is formed on the surface light source, i.e., the OLED panel. However, a blurring effect and color separation result from the finite (nonzero) size of point light sources since each point light source is generated by a pixel of the OLED panel. Simulation results for a blurring effect and color separation in terms of rays from a light source with finite size is presented. The proposed system has a thin structure and simple convertibility because it does not need any additional optical element to provide 2D-3D convertibility.

LED를 PLS 배열로 사용한 시역 형성 광학계가 없는 3차원 영상의 시역에 대한 연구

A two dimensional point light source array can replace both the viewing zone forming optics and the back light panel in the contact-type 3 dimensional imaging systems based on LC panels. This replacement can make the system structure of the 3 dimensional imaging systems no different from that of the conventional LCD and can reduce undesirable visual effects caused by the viewing zone forming optics. The problem with the point light source array is the visual quality deterioration of the system due to the non-ideal nature of the array.

Viewing Zones in PLS Based Multiview 3-D Imaging Systems

In 3D imaging systems, with a point light source (PLC) array as a backlight illumination and viewing zone forming, the finite size of the light-emitting surface of each PLC in the array and mismatch between the array period and pixel cell pitch limits the region of individual view image to a small portion of the viewing zone cross section (VZCS). The portion becomes smaller as the size approaches that of a pixel for an individual view image in the pixel cell, and/or the fractional size of the pixel becomes smaller. As a consequence, the VZCS becomes filled with viewing regions for mixed images of two adjacent view images. Hence, the effective number of different images which can be viewed at VZCS could be increased around two times that of the total different view images displayed on the display panel.

Increased horizontal viewing zone angle of a hologram by resolution redistribution of a spatial light modulator

The narrow viewing zone angle is one of the problems associated with electronic holography. We propose a technique that enables the ratio of horizontal and vertical resolutions of a spatial light modulator (SLM) to be altered. This technique increases the horizontal resolution of a SLM several times, so that the horizontal viewing zone angle is also increased several times. A SLM illuminated by a slanted point light source array is imaged by a 4f imaging system in which a horizontal slit is located on the Fourier plane. We show that the horizontal resolution was increased four times and that the horizontal viewing zone angle was increased approximately four times.

３次元映像情報メディア技術 擬似高解像度化によるホログラムの水平視域角拡大

We developed a new technique that enables the ratio of horizontal and vertical resolutions of a spatial light modulator (SLM) to be altered. This technique virtually increases the horizontal resolution of an SLM so that the horizontal viewing angle of a hologram displayed by the SLM is also increased. An SLM illuminated by a slanted point light source array is imaged by a 4f imaging system in which a horizontal slit is located on a Fourier plane. When the number of point light sources is K, the horizontal resolution increases K times and the horizontal viewing angle increases approximately K times. We demonstrated the horizontal viewing angle enlargement using an SLM with a pixel pitch of 9.5 µm and a resolution of 4,096×2,160. The number of light sources was four (K = 4.) The horizontal resolution was increased to 16,384 and the horizontal viewing angle was increased to approximately 15°. The resultant three-dimensional images can be observed by both eyes.