Electro-holographic Display Research Articles

Speckle control for electro-holographic display using high-brightness yellow phosphor light source in projector

Speckle control for electro-holographic display using high-brightness yellow phosphor light source in projector

Accommodation and Vergence Responses to Electronic Holographic Displays and Super Multiview Holographic Stereograms

Electronic holography is an ideal 3-D display technique to ameliorate the vergence-accommodation conflict, which is a possible cause of visual fatigue and discomfort from viewing conventional stereoscopic 3-D displays. Previous studies have measured accommodative and vergence responses to holographic images and to real objects, and the results showed that these responses are in good agreement. To demonstrate the effectiveness of electronic holography as a possible solution to the vergence-accommodation conflict caused by viewing conventional stereoscopic 3-D displays, we measured both accommodative and vergence responses to reconstructed images of holograms and super multiview holographic stereograms. We also measured responses to real objects located at various distances and conventional two-view stereo images for comparison. The results indicate that the accommodative responses to the electro-holographic display and super multiview holographic stereogram change with the vergence response in a similar manner, as is the case with real objects as compared to conventional two-view stereo display. This suggests that the electronic holographic display and super multiview holographic stereograms are promising candidates for resolving the vergence-accommodation conflict.

30‐4: Electroholographic Display Based on a Horizontal Array of Edge‐Emitting Surface Acoustic Wave Modulators

An emerging enabling technology for electronic holographic displays is the surface acoustic wave (SAW) acousto‐optical modulator family. The authors describe successful demonstration of a horizontal parallax only (HPO) electroholographic display composed of 10 edge‐emitting SAW modulators with 8 channels each. It features innovations in display architecture, modulator design, packaging, and illumination.

Submicron-scale light modulation device driven by current-induced domain wall motion for electro-holography

A submicron-scale magneto-optical light modulation device driven by current-induced domain wall motion (CIDWM) was fabricated for an electro-holographic display application. The device consists of a Gd–Fe nanowire for light modulation and two Co/Pd hard magnets (HMs) with different coercivities. We succeeded in fabricating two HMs with different coercivities from a Co/Pd film by simply changing their length and realizing an anti-parallel magnetization direction configuration for the HMs, which is very important for initial domain nucleation and the CIDWM. We confirmed successful domain wall motion and light modulation when a pulse current of ±0.8 mA was injected into the device, whose size was as small as 0.5 × 2 μm2. The current value was lower than that required for the previously reported light modulation device driven by spin-transfer switching.

Wide visual field angle holographic display using compact electro-holographic projectors.

Electro-holography has the problem of having a narrow visual field angle, because the resolution of a spatial light modulator is insufficient for displaying a fringe pattern. To solve this problem, this paper proposes a projector-type electro-holographic compact display that achieves a wide visual field angle by using the combination of an optical system and calculation algorithms. The results of experiments show that the visual field angle is three times larger than that of a normal electro-holographic display. In addition, it is demonstrated that the system has the ability to display 3D reconstructed images with binocular, full-color, high-resolution, and accurate depth presentation.

Real-time three-dimensional video reconstruction of real scenes with deep depth using electro-holographic display system.

Herein, we demonstrate a real-time, three-dimensional (3D) video-reconstruction system using electro-holography in real-world scenes with deep depth. We calculated computer-generated holograms using 3D information obtained through an RGB-D camera. We successfully reconstructed a 3D video (in real time) of a person moving in real-world space and confirmed that the proposed system operates at ~14 frames per second. In addition, we successfully reconstructed a full-color 3D video of the person. Furthermore, we varied the number of persons moving in the real-world space and evaluated the proposed system's performance by varying the distance between the RGB-D camera and the person(s).

Electro-holographic display using a ZBLAN glass as the image space.

An Er3+-doped ZBLAN glass is used to display a 360° viewable reconstructed image from a hologram on a DMD. The reconstructed image, when the hologram is illuminated by a 852 nm wavelength laser beam, is situated at the inside of the glass, and then a 1530 nm wavelength laser beam is crossed through the image to light it with an upconversion green light, which is viewable at all surrounding directions. This enables us to eliminate the limitation of the viewing zone angle imposed by the finite size of pixels in electro-holographic displays based on digital display chips/panels. The amount of the green light is much higher than that known previously. This is partly caused by the upconversion luminescence induced by 852 and 1530 nm laser beams.

On the Expansion of the Displaying Volume of the Reconstructed Images in the Electro-Holographic Display Using Mist Screen

On the Expansion of the Displaying Volume of the Reconstructed Images in the Electro-Holographic Display Using Mist Screen

電子ホログラフィの再生像の奥行きに対する静的輻輳・調節応答の測定

Theoretically, it is expected that a display based on an electro-holography shows three-dimensional (3D) images which satisfy all physiological factors of the depth perception of persons. A novel electro-holographic display for binocular vision was fabricated for measurements of physiological responses to 3D images. The display has a wide field of view, full parallax, and also ability to display 3D images that provide accurate accommodative and convergence stimuli correlated with depth position estimated by the viewers. The vergence and accommodation responses of viewers to the 3D images were measured objectively using an infrared optometer, and moreover depth perceptions were assessed. The comparison between measured values to the images and to real objects indicated that 3D images were displayed at the correct depth position. The results suggest that an electro-holographic display satisfy physiological factors of the depth perception.

전자 홀로그래피 및 초 다시점 3차원 영상 디스플레이

Supermultiview and electro-holographic displays are promising displays for the future because they provide continuous parallaxes as their depth cue. But they are still in the early development stage due to the lack of supporting technologies. Achieving the continuous parallax in the supermultiview relies more on the number and size of pixels in the pixel cell/elemental image rather than the number of different view images. For the electro-holographic display, it also relies on the number and size of pixels in the panel. So these two methods share the same requirements for achieving the parallax. But the image displayed on the holographic display provides more impressive visual appeal than that on the supermultiview because the image can be floated on the front space of the display.

State of the Art in Holographic Displays: A Survey

True-3D imaging and display systems are based on physical duplication of light distribution. Holography is a true-3D technique. There are significant developments in electro-holographic displays in recent years. Liquid crystal, liquid crystal on silicon, optically addressed, mirror-based, holographic polymer-dispersed, and acousto-optic devices are used as holographic displays. There are complete electro-holographic display systems and some of them are already commercialized.

A computer aided design tool for developing an electroholographic display

An electroholographic display is a three-dimensional (3D) display, using electroholography, for recording and reconstructing a 3D object. An electroholographic display has advantages as compared with other 3D displays; for example it can reconstruct 3D images with full parallax. However, an electroholographic display requires complex design and development of the optical system. In this paper, we report our computer aided design (CAD) tool for developing an electroholographic display. By calculating the diffraction of light, the CAD tool can rapidly evaluate a 3D reconstructed image from an electroholographic display system without developing the actual system.

Electroholographic display unit for three-dimensional display by use of special-purpose computational chip for holography and reflective LCD panel

We developed an electroholography unit, which consists of a special-purpose computational chip for holography and a reflective liquid-crystal display (LCD) panel, for a three-dimensional (3D) display. The special-purpose chip can compute a computer-generated hologram of 800x600 grids in size from a 3D object consisting of approximately 400 points in approximately 0.15 seconds. The pixel pitch and resolution of the LCD panel are 12 mum and 800x600 grids, respectively. We implemented the special purpose chip and LCD panel on a printed circuit board of approximately 28cmx13cm in size. After the calculation, the computer-generated hologram produced by the special-purpose chip is displayed on the LCD panel. When we illuminate a reference light to the LCD panel, we can observe a 3D animation of approximately 3cmx3cmx3cm in size. In the present paper, we report the electroholographic display unit together with a simple 3D display system.

Reduction of coherent artifacts in dynamic holographic three-dimensional displays by diffraction-specific pseudorandom diffusion

An electroholographic display based on diffraction-specific computation can reduce speckle by electronic diffusion through selective addition of a pseudorandom sequence. Intensity fluctuation as a result of the introduction of pseudorandom noise does not affect three-dimensional (3-D) images significantly since spatial windows formed by diffused basis fringes do not widen noticeably at low pseudorandom spread, whereas the features of the fluctuation are much smaller than human visual resolution. Experimental results obtained on the Massachusetts Institute of Technology holographic video system confirmed that the diffusion smooths 3-D images and improves the intensity nonuniformity among horizontal holographic lines.

Color Electro Holographic Display for Projecting 3D Images into Space

Color Electro Holographic Display for Projecting 3D Images into Space

Color electro-holographic display using a single white light source and a focal adjustment method

A new method for achieving a color electroholographic display has been developed and tested with promising results. In this method, holographic techniques that use a single white light source instead of the traditional three color lasers are employed. A metal halide lamp is used with each of the three color components required for reconstruction, which are extracted using cold mirrors. The separated color images are formed on three liquid-crystal display panels and are combined by a prism to form a single 3-D image. Image position is controlled by a focal adjustment method. Compared with the usual reconstruction methods that use three-color lasers, this new single-white-light approach appears to have improved color clarity.

Reducing Image-blur for Color Electro-holographic Display by White-light-laser

Reducing Image-blur for Color Electro-holographic Display by White-light-laser

Computer Generated Rainbow Hologram

The rainbow hologram is very practical to display 3-D images because it can be reconstructed with white light. We propose a simplified model to calculate the computer generated rainbow hologram quickly. In the proposed method, we can simply generate the final hologram from intermediate data, whose total number of samples can be less than one tenth of the final hologram. This intermediate format makes fast computation and effective storage/transmission possible. Only multiple and additional operation need be used to convert the intermediate data to final data. Therefore, it is possible that hardware can be added to an electro-holographic display or printer. In this paper, we discuss both theory of the simplified model and experimental results of white light reconstructed images. Full color holograms are also discussed.

Improved electroholographic display using liquid crystal devices to shorten the viewing distance with both‐eye observation

We are constructing an electroholographic display system using liquid crystal devices (LCDs) as spatial light modulators to control the wavefront of laser light for reconstructing 3-D images. A wide horizontal viewing zone is secured with five special LCDs set up in a continuous series by a half mirror. The viewing distance is still considerably long, however, and this distance reduces the perception of image depth. Thus, we suggest setting a field lens at the center of the reconstructed image to shorten the viewing distance. Since the reconstructed 3-D image becomes considerably distorted by the use of a field lens, we propose predistortion to compensate. Each LCD is assumed to have 3200 (H) X 960 (V) pixels with 28 (H) X 56 (V) µm pixel pitch. Although, this LCD is still in trial production, we have confirmed the reconstructed image by replacing the LCDs with computer-generated holograms (CGHs) recorded to five photographic films having the same specifications as real LCDs. In this way, we verified the reconstructed image [50 (W) X 50 (D) X 100 (H) mm] with off-axis, horizontal parallax only. This image can be observed with both eyes at a distance of 900 mm, and we can perceive the image depth sufficiently.

特集 次世代画像技術 ホログラフィック３次元画像の情報圧縮

Since the information content of a hologram is so huge, data compression is important for a practical electroholographic display system. We have therefore investigated the block subsampling method and the interpolation of subsampled data. This procedure, however, also causes a blur on the displayed 3D image. Therefore, there is a trade-off relation between the information reduction rate and the image blur. It is not practical to apply 2D image compression to a hologram because the character of the holographic data is quite different from that of a 2D image. We have demonstrated that 2D compression techniques can be used effectively to compress the fringe pattern by first segmenting it and then performing a transform operation upon it. We have discussed both theoretical and experimental results and have compared the image quality of those two compression methods.