Different aspects of the characterization of curved displays are presented. The limit of validity of viewing angle measurements without angular distortion on such displays using goniometer or Fourier optics viewing angle instrument is given. If the condition cannot be fulfilled the measurement can be corrected using a general angular distortion formula as demonstrated experimentally using a Samsung Galaxy S6 edge phone display. The reflective properties of the display are characterized by measuring the spectral BRDF using a multispectral Fourier optics viewing angle system. The surface of a curved OLED TV has been measured. The BDRF patterns show a mirror like behavior with and additional strong diffraction along the pixels lines and columns that affect the quality of the display when observed with parasitic lighting. These diffraction effects are very common on OLED surfaces. We finally introduce a commercial ray tracing software that can use directly the measured emissive and reflective properties of the display to make realistic simulation under any lighting environment.
In this paper, we propose the see-through parallax barrier type multi-view display with transparent liquid crystal display
(LCD). The transparency of LCD is realized by detaching the backlight unit. The number of views in the proposed
system is minimized to enlarge the aperture size of parallax barrier, which determines the transparency. For
compensating the shortness of the number of viewpoints, eye tracking method is applied to provide large number of
views and vertical parallax. Through experiments, a prototype of see-through autostereoscopic 3D display with parallax
barrier is implemented, and the system parameters of transmittance, crosstalk, and barrier structure perception are
Elongated dye molecules orient themselves with surrounding liquid crystal molecules. We propose to incorporate such a guest-host cell in a screen of a projection display. This configuration might be applied for digital signage to be installed on building walls. Dual-mode operation is realized by the bias applied to the cell. In display-mode, the dye molecules are oriented in parallel to the substrate of the cell. When excited by ultra-violet light, photoluminescence (PL) is generated. Because it is mostly perpendicular to the long axis of the molecule, it exits the cell efficiently. In powerharvesting mode, they are oriented vertically. The PL generated by ambient light is directed to edge surfaces where solar cells are mounted. In experiment, we fabricated a cell with commonly-available materials (coumarin 6 and a nematic liquid crystal). Anti-parallel alignment condition was adopted. We recorded PL spectra from the cell for the two excitation conditions. First, the center of the cell was irradiated by a 1.69mW blue laser beam. Second, the whole cell was uniformly exposed to the light from a fluorescent lamp at illuminance of 800lx. From the measured spectra for these cases, the contrast of luminance is calculated to be 3.2 ×105 . This factor is improved to 5 7.5×105 by attaching a polarizer sheet on the cell surface. The optical power reaching its edge surfaces is measured and it roughly agrees with the prediction by a simple model neglecting self-absorption. Development of phosphor materials with a large Stokes shift is desired to boost performance of the proposed system.
A spatially multiplexed autostereoscopic 3D display design with a strip barrier consisting of RGB-color filters is
presented. The wavelength selective filter barrier emits the light from a display area larger than that of common
autostereoscopic barrier displays. However, such construction is still used rather rarely. The time sequential operation
mode is a supplemental option. Wavelength selective filter barrier arrangements exhibit characteristics different from
common barrier displays with similar barrier pitch and ascent. In particular these constructions show strong angular
luminance dependency under barrier inclination specified by correspondent slant angle. In time sequential
implementation it is important to avoid that quick eye or eyelid movement lead to visible color artifacts. Those
circumstances limit the possibility to find well working and usable display designs superior to usual barrier displays.
The newly introduced design is usable as a multi user display as well as a single user system with user adaptive control.
In case of tracked single user mode the adaption in x-z-direction is continuously. The design has been modelled with
simulation software developed for that purpose. The modelling of wavelength-selective barriers was used to calculate
the light ray distribution properties of that arrangement. For the experimental verification of the image separation and
evaluation of image quality, commercially available display components were combined for a display demonstrator.
Recently, super multi-view technology has been considered as one of the most popular research topic and many studies
have been done to improve the quality of such super multi-view display. In this paper, we present specific experiments
for human cognition. We designed our system for the special purpose that the human cognition of 3D contents is
examined. In comparison of the previous super multi-view displays, the number of views in our system can be
controlled. Our system has a great advantage that the effect of the number of views can be evaluated at the common
system. We can change the number of views, by changing the synchronization ratio which determines the speed of the
opening of the optical chopper and the refresh time of the DMD. We expect that this system will be useful for
understanding the principle of the human cognition for 3D display.
In recent years, the development of displays, projectors, and the like which use laser light sources have been advanced. As a laser light source is used, it provide wide color gamut and compact an optical system; on the other hand, the speckle noise is generated. We make a proposal about the microcapsule diffuser screen with the purpose of reducing the speckle noise on a laser rear projection display. This microcapsule diffuser screen has a screen surface in which microcapsules (~100um) containing charged diffuser particles are applied; where an electric field is charged from the outside and, thus, the diffuser particles in the capsule are randomly agitated to reduce the speckle noise. We have separately reported the effect of reducing speckle in relation to the driving parameters. The previous report, however, did not discuss how the configuration parameters within the microcapsule would affect the brightness, diffusion characteristics and other particulars. In this report, the authors used the Monte Carlo ray tracing method to study the diffusion characteristics of the microcapsule diffuser sheet with reference to the refractive index and diameters of the diffuser particles. The study confirmed that while the diffusion characteristics lowered with the diffuser particle diameter being 3.0μm or smaller the optical loss of the transmitting light significantly increased. Where designing the capsule profile based on the simulation model, a simple spherical profile failed to see that the actual measurement and calculated values did not agree with the other. The optical simulation model created based on a microscopic image confirmed that both values agreed. Thus, the authors confirmed that the latter was suitable for an optical simulation model.
Ambient light is destructive to the reflective type projection system’s contrast ratio which has great influence on the
image quality. In contrast to the conventional front projection, short-throw projection has its advantage to reject the
ambient light. Fresnel lens-shaped reflection layer is adapted to direct light from a large angle due to the low lens throw
ratio to the viewing area. The structure separates the path of the ambient light and projection light, creating the chance to
solve the problem that ambient light is mixed with projection light. However, with solely the lens-shaped reflection layer
is not good enough to improve the contrast ratio due to the scattering layer, which contributes a necessarily wide viewing
angle, could interfere with both light paths before hitting the layer. So we propose a new design that sets the draft angle
surface with absorption layer and adds an angle-selective absorber to separate these two kinds of light. The absorber is
designed to fit the direction of the projection light, leading to a small absorption cross section for the projection light and
respectfully big absorption cross section for the ambient light. We have calculated the design with Tracepro, a ray tracing
program and find a nearly 8 times contrast ratio improvement against the current design in theory. This design can
hopefully provide efficient display in bright lit situation with better viewer satisfaction.
A two dimensional sinusoid diffraction grating is developed for a moiré-reducing low-pass filter. Typical display units
have image pixels arranged systematically in two dimensions, with non-illuminating regions between the image pixels.
Using a conventional lens to view this display, the image pixels and the region between the pixels are both magnified,
and the resulting image is unpleasant to the human eye, especially with color displays, called the screen door effect. This
pixel problem is typically solved with a low-pass filter using a diffraction grating. However, depending on the period of
the diffraction grating compared to the period of the image pixels, moiré can be seen.
In recent years, organic electroluminescence displays with a small fill factor are growing popular, but such displays are
usually more prone to the screen door effect and moiré. With conventional optical low-pass filters, only the pixel pitch in
the vertical and horizontal directions are taken into account, but this is insufficient with small fill-factor pixels, and
consideration for various diagonal periods is needed.
A two dimensional sinusoid structure diffraction grating is developed for a moiré-reducing low-pass filter. The angle of
the grating with the image pixel arrangement, the distance between the display and the grating, the grating depth, and the
grating period are all chosen appropriately, and take into account multiple non-adjacent diagonal image pixel periods for
all colors, consequently reducing moiré and the screen door effect. We present the calculations and evaluation results
from plastic samples made by lithography tooled molds.
Capacitive touch sensor screen with the metal materials has recently become qualified for substitution of ITO; however several obstacles still have to be solved. One of the most important issues is moiré phenomenon. The visibility problem of the metal-mesh, in touch sensor module (TSM) is numerically considered in this paper. Based on human eye contract sensitivity function (CSF), moiré pattern of TSM electrode mesh structure is simulated with MATLAB software for 8 inch screen display in oblique view. Standard deviation of the generated moiré by the superposition of electrode mesh and screen image is calculated to find the optimal parameters which provide the minimum moiré visibility. To create the screen pixel array and mesh electrode, rectangular function is used. The filtered image, in frequency domain, is obtained by multiplication of Fourier transform of the finite mesh pattern (product of screen pixel and mesh electrode) with the calculated CSF function for three different observer distances (L=200, 300 and 400 mm). It is observed that the discrepancy between analytical and numerical results is less than 0.6% for 400 mm viewer distance. Moreover, in the case of oblique view due to considering the thickness of the finite film between mesh electrodes and screen, different points of minimum standard deviation of moiré pattern are predicted compared to normal view.
We propose three dual-view integral imaging (DVII) three-dimensional (3D) displays. In the spatial-multiplexed DVII
3D display, each elemental image (EI) is cut into a left and right sub-EIs, and they are refracted to the left and right
viewing zones by the corresponding micro-lens array (MLA). Different 3D images are reconstructed in the left and right
viewing zones, and the viewing angle is decreased. In the DVII 3D display using polarizer parallax barriers, a polarizer
parallax barrier is used in front of both the display panel and the MLA. The polarizer parallax barrier consists of two
parts with perpendicular polarization directions. The elemental image array (EIA) is cut to left and right parts. The lights
emitted from the left part are modulated by the left MLA and reconstruct a 3D image in the right viewing zone, whereas
the lights emitted from the right part reconstruct another 3D image in the left viewing zone. The 3D resolution is
decreased. In the time-multiplexed DVII 3D display, an orthogonal polarizer array is attached onto both the display
panel and the MLA. The orthogonal polarizer array consists of horizontal and vertical polarizer units and the polarization
directions of the adjacent units are orthogonal. In State 1, each EI is reconstructed by its corresponding micro-lens,
whereas in State 2, each EI is reconstructed by its adjacent micro-lens. 3D images 1 and 2 are reconstructed alternately
with a refresh rate up to 120HZ. The viewing angle and 3D resolution are the same as the conventional II 3D display.
A method for realizing a three-dimensional see-through augmented reality in Fourier holographic display is proposed. A holographic optical element (HOE) with the function of Fourier lens is adopted in the system. The Fourier hologram configuration causes the real scene located behind the lens to be distorted. In the proposed method, since the HOE is transparent and it functions as the lens just for Bragg matched condition, there is not any distortion when people observe the real scene through the lens HOE (LHOE). Furthermore, two optical characteristics of the recording material are measured for confirming the feasibility of using LHOE in the proposed see-through augmented reality holographic display. The results are verified experimentally.
RGB-light sources with a coherence length of several meters are required for holographic displays. Furthermore, these
emitters must feature a high luminance and must be sufficiently small in size, to be employed in today’s consumer
market products. Therefore, an all-semiconductor based solution is preferred.
We developed red-emitting semiconductor lasers at 635 nm and 647 nm with internal distributed Bragg reflectors and
suitable amplifiers at these wavelengths to boost the lasers output power. We investigated tapered amplifiers containing a
ridge-waveguide section as well as truncated tapered designs in master-oscillator power-amplifier configuration
(MOPA). This allowed the generation of diffraction limited single mode emission by the MO-chip and subsequent
amplification of the radiation by the PA-chip by more than 10 dB, without significantly degrading the coherence
properties. We successfully demonstrated an optical output power of more than 300 mW at 635 nm and 500 mW at
647 nm. The radiation featured a linewidth below 10 MHz, which corresponds to a coherence length of at least several
meters, well suited for a holographic system.
We present a compact binocular head-up display for integration in a motorcycle helmet. A 2D MEMS-mirror reflecting laser beams enables the formation of a bright image superimposed on the user vision by means of retinal scanning. A 3d-printed prototype including the required optical components is presented and characterized. It fits the morphology of most users thanks to several degrees of freedom accessible to the user for fine-tuning.
This paper presented our current research about the intra-oral scanner made by MIRDC. Utilizing the sinusoidal pattern for fast phase-shifting technique to deal with 3D digitalization of human dental surface profile, the development of pseudo-phase shifting digital projection can easily achieve one type of full-field scanning instead of the common technique of the laser line scanning. Based on traditional Moiré method, we adopt projecting fringes and retrieve phase reconstruction to forward phase unwrapping. The phase difference between the plane and object can be exactly calculated from the desired fringe images, and the surface profile of object was probably reconstructed by using the phase differences information directly. According to our algorithm of space mapping between projections and capturing orientation exchange of our intra-oral scanning configuration, the system we made certainly can be proved to achieve the required accuracy of ±10μm to deal with intra-oral scanning on the basis of utilizing active triangulation method. The final purpose aimed to the scanning of object surface profile with its size about 10x10x10mm3.
In this work we report the fabrication of thin film transistors (TFT) with zinc oxide channel and molybdenum doped indium oxide (IMO) electrodes, achieved by room temperature sputtering. A set of devices was fabricated, with varying channel width and length from 5μm to 300μm. Output and transfer characteristics were then extracted to study the performance of thin film transistors, namely threshold voltage and saturation current, enabling to determine optimal fabrication process parameters. Optical transmission in the UV-VIS-IR are also reported.