Microdisplay Devices Research Articles

Monolithic Integration of Full-Color Microdisplay Screen with Sub-5µm Quantum-Dot Pixels.

Monolithic integration of color-conversion materials onto blue-backlight micro-light-emitting-diodes (micro-LEDs) has emerged as a promising strategy for achieving full-color microdisplay devices. However, this approach still encounters challenges such as the blue-backlight leakage and the poor fabrication yield rate due to unsatisfied quantum dot (QD) material and fabrication process. Here, the monolithic integration of 0.39-inch micro-display screens displaying colorful pictures and videos are demonstrated, which are enabled by creating interfacial chemical bonds for wafer-scale adhesion of sub-5 µm QD-pixels on blue-backlight micro-LED wafer. The ligand molecule with chlorosulfonyl and silane groups is selected as the synthesis ligand and surface treatment material, facilitating the preparation of high-efficiency QD photoresist and the formation of robust chemical bonds for pixel integration. This is a leading record in micro-display devices achieving the highest brightness larger than 400 thousand nits, the ultrahigh resolution of 3300 PPI, the wide color gamut of 130.4% NTSC, and the ultimate performance of service life exceeding 1000h. These results extend the mature integrated circuit technique into the manufacture of micro-display device, which also lead the road of industrialization process of full-color micro-LEDs.

All Silicon Microdisplay Fabricated Utilizing 0.18 μm CMOS-IC With Monolithic Integration

A low voltage all silicon microdisplay is presented based on MOS-like gate-control all-Silicon light-emitting diode (LED) in standard 0.18 μm complementary metal oxide semiconductor (CMOS) technology. The MOS-like LED is designed under a PN alternate structure with polysilicon gate control electrode for high luminous intensity and low operating voltage. The microdisplay device is fabricated based on the LED as pixel units. The size of the proposed microdisplay device is 6.2 mm × 5.0 mm with a about 368 mW/mm2 luminous intensity at the stable operating voltage of 1.8 V.

Design and assessment of a wide FOV and high-resolution optical tiled head-mounted display.

It has always been a challenge to break the resolution/field-of-view (FOV) invariant to design a large FOV and high-resolution optical system, especially for a head-mounted display (HMD) system. In this study, a tiled HMD using two compact rotationally symmetrical eyepieces was designed and developed. Some issues on exit pupil and eye relief were analyzed in detail and taken into consideration during the design procedure. The overall optical system is compact with high performance. The system volume is smaller than 30 mm×35 mm×30 mm. Based on two 0.61 in. microdisplay devices, the overall tiled system demonstrates an FOV of 66°(H)×32°(V) with a 7.5 mm exit pupil diameter and a 15.7 mm eye relief.

18.2: Bistable FLCOS Devices for Doubled‐Brightness Micro‐Projectors

AbstractOptical efficiency is of paramount importance to emerging ultra‐miniature projector products. We have developed experimental bistable ferroelectric‐liquid‐crystal‐on‐Silicon (FLCOS) projection microdisplay devices using newly developed FLC materials aligned on obliquely‐deposited SiO2. These devices enable doubling of illumination duty cycle, and hence doubling of achievable projector light output, while maintaining DC‐balanced electrical drive.

8.2: Bi‐Directional OLED Microdisplay for Interactive HMD

AbstractFirst prototypes of bi‐directional OLED microdisplay devices have been designed, that combine both display and camera functionality on a single CMOS chip (OLED‐on‐CMOS). Major aim of this integration is to provide capabilities for eye‐tracking in see‐through HMD to achieve gaze‐based human‐display‐interaction, e.g. in augmented‐reality applications.

19.4: MicroDisplay Panel as Vision Test Chart Imager

Microdisplay device is well known as high resolution imagers. In this study, we propose that using microdisplay as the vision test chart imagers. The measurements, such as vision acuity and contrast sensitivity, can be by using this kind of device.

Fringing-Field Effects on High-Resolution Liquid Crystal Microdisplays

Fringing-field effects on high-resolution liquid crystal microdisplay devices, including the reflection-type liquid-crystal-on-silicon (LCOS) and transmission-type poly-silicon thin-film-transistor liquid crystal displays are simulated by the beam propagation method. The electro-optic performances of six commonly used liquid crystal modes are analyzed by the two-dimensional optical simulator. The vertically aligned (VA) cell exhibits the highest contrast ratio, but its fringing-field effect is severe. A circularly polarized light illuminated LCOS device is presented to eliminate the fringing-field effect of the VA cell. Both simulated and confirming experimental results show that the long-standing problems of poor sharpness, low brightness, and slow transition time of the VA cell can be overcome by using a circularly polarized light.

Blue electroluminescence from MOS capacitors with Si-implanted SiO 2

Electroluminescence (EL) spectra under direct-current (dc) operation are reported for Au/SiO 2/p-Si MOS capacitors with 50 nm Si-implanted SiO 2. The transparent Au gate not only improves measurable wavelength range but also suppresses interference effects among MOS layers. The clear and smooth EL spectra have been measured and the EL spectrum was analyzed by fitting five Gaussian distribution functions. A model of EL emission mechanism is proposed for the Si-implanted MOS EL device. Furthermore, photomicrograph of blue EL emission is given, and a possibility of visible light emitting microdisplay device is demonstrated.

Head-mounted display with LCOS using diffractive optical element

Summary We designed a 60° hybrid refractive-diffractive eyepiece for head mounted display (HMD), and applied it in micro-display of liquid crystal on silicon (LCOS) by introducing a relay system. The hybrid eyepiece design is based on a traditional Erfle eyepiece. It has a 10mm exit pupil and a 22mm eye relief, which satisfies the requirements of HMD used in computer entertainment and visual reality. Moreover, the proposed eyepiece possesses better performances with a considerable reduction in physical size and weight compared to the traditional refractive type. The relay system can solve the matching problem between micro-display device and eyepiece, and provides the space for illuminating light source. The whole optical system is suitable for display of 18 mm-diagonal LCOS with a VGA resolution.

Simple 40° head-mounted display

Summary A simple 40° eyepiece matched with the micro-display device is designed. It consists of two elements, including a binary surface and an aspheric surface. With satisfactory performance, the eyepiece can be used in display with a SXGA resolution sized 1.1 inches diagonal. Because no other relay system is needed, the HMD system could be made more compact with much less weight.

Numerical modelling of light wave propagation in reflective liquid crystal microdisplay devices

Steep variation in the liquid crystal director orientation in more than one dimension is frequently encountered in microdisplay devices in the proximity of pixel edges. It is expected that light wave propagation inside such devices cannot be addressed rigorously if the traditional matrix methods for optics are employed. Numerical modelling is suggested for such demanding situations based on the general solution of Maxwell's equations by the finite difference time-domain method or by properly applying a vector beam propagation method suitable for anisotropic media. Interest is focused on reflective devices. A complete understanding of light diffraction in two-dimensional reflective devices is made possible using the proposed numerical methods, contrary to matrix methods for optics (which are not suitable for such a task). Approaches for addressing cases involving incoherent illumination are also suggested.

26.3: Investigation of the Bow of Silicon Backplanes for Microdisplay Applications

AbstractThe optical performance of ferroelectric liquid crystal over silicon (FLCOS) microdisplay devices can be greatly improved by ensuring that the silicon backplane that forms the core of the display engine is both smooth and flat. In this paper we investigate the effect of the circuit design and manufacturing process on the bow of the silicon CMOS drive circuitry.