Identifying Factor Associations Emerging from an Academic Metaverse Event for Scholars in a Postpandemic World: Social Presence and Technology Self-Efficacy in Gather.Town.

COVID-19 has prompted conferences to transition to online formats, inadvertently diminishing their emphasis on the social element. In online events, a sense of presence leading to a sense of companionship is limited in conventional conferencing platforms. Although the extant body of research on virtual conferences is growing, academic events in the Metaverse get little attention. Such events and their relevance to social presence within the Metaverse and associations among observable factors are seldom discussed. This study examined the perspectives of scholars in an online seminar during COVID-19 hosted in Gather.Town, a Metaverse-like conferencing environment. A hypothetical model was built to determine whether social presence and technology self-efficacy impact scholars' satisfaction and facilitate academic interactions. Ninety-three scholars in an academic seminar for research projects in information and computer education were polled to obtain data, which was then evaluated using partial least squares structural equation modeling (PLS-SEM). The proposed model explained 57.1 percent of the variables, and the findings showed that social presence and technology self-efficacy had a positive and significant impact on academic interactions and exchanges, as well as technology self-efficacy playing an essential role in determining overall satisfaction. However, social presence does not appear to have a direct impact on satisfaction, implying that a positive academic experience may still be achieved with or without the feature of being with others supported by the Metaverse. Although digital communication will only become more diverse and intense, it is important to understand how to maintain the basic character of human interactions virtually, even amid a pandemic. This research attempts to shed light on some critical factors in creating a conducive environment for future Metaverse-like academic events.

See-through holographic display with randomly distributed partial computer generated holograms.

Holographic displays have the feature to show images out of the plane of the device itself, which is especially favored for augmented reality (AR) applications where the images need to be merged with the real world. In existing cases of AR holographic display, a combiner is used to converge the light path of the display image and surrounding scene toward the viewer's eye. In this paper, the idea of combining the holographic device and the combiner has been proposed, resulting in a see-through holographic display. In order to maintain the see-through quality of the device, the concept of partial hologram has been introduced, which means only a part of the area on the device has the holographic fringe pattern while leaving the rest fully transparent. Experiment and theoretical investigation shows that an evenly yet randomly distributed partial hologram provides the best holographic image quality assuming a fixed percentage of the holographic area on the device. A passive computer generated hologram (CGH) with two phase levels has been designed and fabricated for the verification. With partial hologram sharing 25% of the whole area, the CGH exhibits 90.9% of total transmission and 72.2% of parallel transmission. The demonstration shows a high see-through quality while providing a clear holographic image.

Zoomable head-up display with the integration of holographic and geometrical imaging.

Head-up displays (HUDs) have already penetrated into vehicle applications and demand keeps growing. Existing head-up displays have their image fixed at a certain distance in front of the windshield. New development could have two images displayed at two different yet fixed distances simultaneously or switchable upon request. The physical distance of HUD image is associated with the accommodation delay as a safety issue in driving, and could also be a critical parameter for augmented reality (AR) function. In this paper, a novel architecture for HUD has been proposed to make the image distance continuously tunable by exploiting the merit of both holographic and geometrical imaging. Holographic imaging is capable of changing image position by varying the modulation on a spatial light modulator (SLM) without any mechanical movement. Geometrical imaging can easily magnify longitudinal image position with short depth of focus by using large aperture components. A prototype based on liquid crystal on silicon (LCoS) SLM has demonstrated the capability of changing image position from 3 m to 30 m verified with parallax method.

Diffractive distortion of a pixelated computer-generated hologram with oblique illumination.

Computer-generated holograms (CGHs) have their phase and/or amplitude modulation pattern calculated rather than recorded as for traditional holograms. In practice, the CGH devices are normally pixelated, no matter if they are passive or active ones. In many cases, the reconstruction light illuminates on the CGH devices obliquely, and the pattern generated on the target plane will be distorted from the originally desired one, even if the modulation on the CGH devices has been calibrated for the corresponding illumination angle in CGH calculation and optimization. The distortion is purely related to the diffraction behavior resulting from the geometry of the pixel on the CGH, and therefore diffractive distortion has been coined for this specific phenomenon. In this paper, quantitative analysis of diffractive distortion and a corresponding scheme for correction have been given based on scalar diffraction theory. The proposed concept is that the distortion of the reconstructed image is proportional to the distortion of the signal window. An experiment has been conducted with a phase-type liquid crystal on silicon spatial light modulator (SLM). Both the distortion analysis and the correction scheme have been verified quantitatively for various illumination angles and the direction of the reconstruction light.

Dual-focal-plane augmented reality head-up display using a single picture generation unit and a single freeform mirror.

Two or more focal planes are required in augmented reality head-up displays (AR HUDs) to respectively present basic and interactive driving information to car drivers; whereas, solutions using two separated picture generation units (PGUs) with two sets of optics incur increased cost, reduced reliability, and expanded volume. To develop an AR HUD using a single PGU and a single curved mirror, we propose to set two logically separated regions on a single PGU and optically relay one of them to a new position to create two focal planes. A single freeform mirror acquired through careful optical and mechanical design optimization produces high image quality in an eyebox of 120 mm by 60 mm, simultaneously for a far image (9 m, 10° by 3°) and a near image (2.5 m, 6° by 2°). Finally, an AR HUD product with a compact volume of 8.5 L is fabricated to experimentally verify the design.

Liquid Type Nontoxic Photoluminescent Nanomaterials for High Color Quality White-Light-Emitting Diode.

High-brightness white-light-emitting diodes (w-LEDs) with excellent color quality is demonstrated by using nontoxic nanomaterials. Previously, we have reported the high color quality w-LEDs with heavy-metal phosphor and quantum dots (QDs), which may cause environmental hazards. In the present work, liquid-type white LEDs composed of nontoxic materials, named as graphene and porous silicon quantum dots are fabricated with a high color rendering index (CRI) value gain up to 95. The liquid-typed device structure possesses minimized surface temperature and 25% higher value of luminous efficiency as compare to dispensing-typed structure. Further, the as-prepared device is environment friendly and attributed to low toxicity. The low toxicity and high R9 (87) component values were conjectured to produce new or improve current methods toward bioimaging application.

Improvement of light quality by ZrO(2) film of chip on glass structure white LED.

A novel combination of blue LED chips, transparent glass substrates and phosphors with PDMS thin film is demonstrated. The flip-chip bonding technology is applied to facilitate this design. The ZrO(2) nanoparticles are also doped into the PDMS film to increase light scattering. The resultant luminous efficiency shows an 11% enhancement when compared to the regular COG device. The variation of correlated color temperature of such devices is also reduced to 132K. In addition to these changes, the surface temperature is reduced from 121°C to 104°C due to good thermal dissipation brought by ZrO(2) nanoparticles.

Near-infrared imaging system for nondestructive inspection of micro-crack in wafer through dicing tape.

Detection of wafer/die crack after the wafer dicing process is important for yield rate control prior to packaging. The traditional approach of microscopic examination is done after the dies are stripped from the dicing tape, and further crack propagation could result from this pick-and-place process. An on-tape crack inspection technique is proposed in this paper so that the crack from the dicing process can be clearly identified. The issues of seeing through the silicon substrate and the scattering at the dicing tape have been resolved, respectively, using a near-infrared wavelength of 1100 nm for illumination and using a feeding index matching liquid for filling the rough surface of the tape. Both the illumination and imaging optics of the inspection system have been designed and simulated with a ray-tracing program, and the prototype demonstrates the ability of seeing through the silicon substrate and dicing tape as well as detecting micro-crack down to 1.25 µm, whose resolution is sufficient for most applications of die crack inspection.

Thin hollow light guide for high-efficiency planar illuminator.

Light guides have been widely used for transforming line sources into planar illuminators for lighting and display applications. Solid light guides provide good uniformity but still have the issues of heavy weight and material absorption, especially for large applications. Hollow light guides solve the problem of weight, but the uniformity is relatively poor or efficiency could be sacrificed for enhancing uniformity. In this paper, a hollow light guide with edge-lit LED sources has been proposed to simultaneously resolve the issues of weight, uniformity, and efficiency. The major approach is to modulate the LED luminous intensity profile by a ring of parabolic surface with continuously varied focal length. The modulated light emitting profile directly makes up sufficient uniformity on the planar surface, and extra components are not required. The prototype is a circular planar illuminator with a diameter of 178 mm and a weight of 240 g. The experiment shows an overall efficiency of 82.37%, with a uniformity of 83.7%. The weight of the whole module is 40% lighter than that of a solid light guide with the same size.

Optical and thermal design of light emitting diodes omnidirectional bulb.

The penetration of LED light bulbs into the lighting market is growing quickly in recent years due to significant increase of LED efficiency and reduction of cost. One major issue to be improved is the overall light bulb efficiency, which can fulfill "Energy Star for Lamps" while keeping sufficiently high efficiency. The efficiency issue results mainly from the high directionality of the LED sources and the corresponding solutions to make the emission more diverse. In this paper, a diffusion white reflection sheet (DWRS) with an array of holes is proposed as a high efficiency solution for modulating a light emission profile with SMD type LED source. The hole size is adjusted with fixed hole pitch to both maximize the efficiency and meet the omnidirectional specification. In addition, the concept of thermal plastic insertion molding metal is proposed for thermal management without fins for cooling. The prototype demonstrates the efficiency (Ef.) of 87.6% and LED pad temperature of 85°C, which shows the feasibility as a total solution for high efficiency LED omnidirectional bulbs.

Development of a modularized seating system to actively manage interface pressure.

Pressure ulcers can be a fatal complication. Many immobile wheelchair users face this threat. Current passive and active cushions do reduce the incidence of pressure ulcers and they have different merits. We proposed an active approach to combine their advantages which is based on the concept that the interface pressure can be changed with different supporting shapes. The purpose of this paper is to verify the proposed approach. With practical applications in mind, we have developed a modular system whose support surface is composed by height-adjustable support elements. Each four-element module was self-contained and composed of force sensors, position sensors, linear actuators, signal conditioners, driving circuits, and signal processors. The modules could be chained and assembled together easily to form different-sized support surfaces. Each support element took up a 3 cm × 3 cm supporting area. The displacement resolution was less than 0.1 mm and the force sensor error was less than 1% in the 2000 g range. Each support element of the system could provide 49 N pushing force (408 mmHg over the 3 cm × 3 cm area) at a speed of 2.36 mm/s. Several verification tests were performed to assess the whole system's feasibility. Further improvements and clinical applications were discussed. In conclusion, this modularized system is capable of actively managing interface pressure in real time.

Sub-15 nm linewidth gratings using roll-to-roll nanoimprinting and plasma trimming to fabricate flexible wire-grid polarizers with low colour shift.

Sub-15 nm-wide gratings with a high aspect ratio of up to 16:1 were fabricated using roll-to-roll nanoimprinting and plasma trimming to achieve high optical performance (up to 12 000:1 extinction ratio with an average transmittance of 82%) and low colour shift (transmittance variation less than 3%) flexible wire-grid polarizers for display applications. We applied two imprint platforms onto glass and plastic substrates to identify the optical properties and characteristics of each fabrication process. To enhance the tolerance, reproducibility, and optical performance of the process, the grating profile symmetry and varying residual layer thicknesses were precisely simulated and controlled to achieve the design targets.

Polarized backlight with constrained angular divergence for enhancement of light extraction efficiency from wire grid polarizer.

Efficiency of liquid crystal displays highly depends on the amount of polarized light emerging from the backlight module. In this paper, a backlight architecture using a nanoimprint wire grid polarizer for polarization recycling is proposed and studied, in which the extraction efficiency of polarized light is the major concern. The backlight module is composed of the stack of a wire grid polarizer, a lenticular array and a light guide plate. The light guide plate features interleaving v-groove and trapezoidal ridge coated with aluminum on the top surface, and scattering dot array on the bottom. The angular divergence of emerging light from the light guide plate can be well constrained so as to exploit the angular range with the best transmission of polarized light for the wire grid polarizer. The prototype of a 2.5-inch module has demonstrated an angular divergence of 48°. The overall extraction efficiency of polarized light enhanced by 21% and uniformity of 76% have been achieved.

Patterned structure of remote phosphor for phosphor-converted white LEDs.

High efficiency white light-emitting diodes with superior color-mixing have been investigated. It is suggested that the patterned remote phosphor structure could improve the uniformity of angular-dependent correlated color temperature (CCT) and achieve high chromatic stability in wider operating current range, as compared to the conventional remote phosphor coating structure. In this experiment, we employed a pulse spray coating method to place the patterned phosphor on the package and to leave a window region. The window area, a clear space without coating of the phosphor not only increases the extraction efficiency of blue rays at large angle, but also improves the stability of angular-dependent CCT. Moreover, the CCT deviation could be reduced from 1320 K to 266 K by this patterned remote phosphor method, and the stray blue/yellow light within the package can be effectively reduced and controlled. The design was verified both experimentally and theoretically.

Color separation system with angularly positioned light source module for pixelized backlighting.

A color-separation system that angularly positions color LEDs to produce color separation and a lens array to focus this light onto the pixels is proposed. The LED rays from different incident angles are mapped into corresponding sub-pixel positions to efficiently display color image, which can be used to replace the absorbing color filter in the conventional liquid crystal layer. In this paper, the prototype backlight has been designed, fabricated and characterized. The measurement results of this module showed that a gain factor of transmission efficiency three times more than that of conventional color filters efficiency improvement and a larger color gamut are expected.

Liquid crystal panel for high efficiency barrier type autostereoscopic three-dimensional displays.

An autostereoscopic display with parallax barrier attached onto a liquid crystal panel suffers from the trade-off between brightness and crosstalk. One approach for making improvement by modifying the layout of light blocking components, such as thin film transistor, storage capacitor, and protrusion, in the liquid crystal pixel has been proposed. Ray tracing simulation shows that the aperture of the slanted barrier can be significantly increased, hence increasing efficiency, while keeping the same crosstalk level if those light blocking components can be shifted to the corner of the pixel. A six-view 2.83 in. (7.19 cm) prototype has shown improvement on both brightness and crosstalk compared to its counterpart using a traditional liquid crystal panel, which demonstrates an effective approach for a high-efficiency barrier-type autostereoscopic 3D display with a liquid crystal panel.

High throughput reflective light guide for planar illuminator.

A light guide fully composed of reflective plate has been proposed for a planar illuminator with the light source located at the side edge. Using mirror reflection as the light guiding mechanism increases the light acceptance angle of the light guide, and the hollow structure allows increasing the source coupling area without inducing further weight. Accompanying with the optical films, for example, a diffuser, a prismatic film, and a reflective polarizer to spread light distribution, the uniformity of the prototype has shown the feasibility for a planar illuminator.