Liquid-Crystal-on-Silicon microdisplays with novel frame buffer pixels

This paper presents the recent developments in our Active Matrix Liquid Crystal Displays for military, avionic and automotive applications. Data is presented for PIN diode driven active matrix liquid crystal display, with full color and high resolution (164 lines per inch). Optimization of color coordinates versus transmission has led us to better overall display performance. The contrast ratios were measured for various viewing angles (+/-60H and +45,-15 V) at different temperatures (-54 C to +85 C). The display shows good high ambient contrast ratio both by theoretical model and experimentally. The discrimination index model is used together with measurements to get the index for different high ambient light levels.

Time-dependent color simulation of active-matrix liquid crystal display adopting the field sequential driving method

A new, lower-cost, and 10FPS-attainable lidar scanning system has been developed. The functions of the system include steering the incident laser, correcting the alignments and aberrations, outputting the signal of the misalignment, and laser incident timing. The system incorporates low-cost parts that include a Liquid Crystal on Silicon (LCOS), a spherical mirror with a transparent layer (SMT), a spherical surface meniscus lens, and photosensors. The key component in this system is the SMT, which increases the LCOS scanning area, reduces the aberration, and creates a reference reflection for optical system correction. Beam steering by the optical phased array is accomplished by varying the refractive index of the liquid crystal in the LCOS. Scanning flash lidar is realized by the combination of the LCOS and SMT, which can emit an intensity distribution-corrected conical beam. The SMT reference reflection corrects three types of errors by adjusting the control parameters of the LCOS: misalignment upon lidar fabrication, long-term or temperature-dependent variation of the optical system, and installation error. In addition, the alignment process manhours and investments for a factory are reduced by eliminating the need for mechanical adjustments. The system can realize flash area-varying lidar, which can achieve a field of view of 1.8 rad in the horizontal direction and 0.3 rad in the vertical direction. An arbitrary irradiation area can be designed using optical phased array techniques.

In this paper, a method for measuring the liquid refractive index based on liquid crystal on silicon (LCoS) is presented. The liquid measuring chamber is composed of two optical lenses, an inlet, and an outlet. By filling the liquid with different refractive indices, the liquid measuring chamber has different focal lengths according to geometric optics. As a reflective micro-display device, the LCoS is another key component, in which the liquid crystal (LC) molecules are arranged in a nematic phase. The programming function of the LCoS, based on the interaction of incident light and the LC molecules in the LCoS, enables the LCoS to form as a digital lens. By using the measuring chamber in the optical system and adjusting the focal lengths of the digital lens, which is loaded on the LCoS, the refractive index of the liquid can be calculated accurately when the sensor receives the focused spot. The experimental results verify the feasibility of our proposed method.

When current domestic Active Matrix Liquid Crystal Display (AMLCD) sources became unavailable, prime contractors for military aircraft faced a severe problem with the sudden obsolescence of these assemblies. AMLCDs had become central to crew station design, but the only qualified North American source had failed. The problem was further complicated as several programs were beginning production, and supplies of existing, useable AMLCDs were rapidly being depleted. Solutions to the availability of AMLCDs had to be found quickly. The F/A - 18E/F program faced a unique situation in that three different displays, manufactured by two different suppliers, were affected by the loss of the AMLCD source. Both of the suppliers, for various technical and programmatic reasons, chose different approaches to the crisis. The advantages and disadvantages of each approach are examined in this paper. In addition, Boeing has formed a Displays Process Action Team (DPAT) to examine whether or not it is possible to use common displays across the Company's diverse product lines.

Chapter 5 - Performance Characteristics

Chapter 6 - Improvement of Image Quality in AMLCDs

Digital Electro-optics Platform is the main concept of Jasper Display Corp. (JDC) to develop various applications. These applications are based on our X-on-Silicon technologies, for example, X-on-Silicon technologies could be used on Liquid Crystal on Silicon (LCoS), Micro Light-Emitting Diode on Silicon (μLEDoS), Organic Light-Emitting Diode on Silicon (OLEDoS), and Cell on Silicon (CELLoS), etc. LCoS technology is applied to Micro Display, Spatial Light Modulator (SLM), Dynamic Optics, Wavelength Selective Switch (WSS), Holographic Display, Microscopy, Bio-tech, 3D Printing and Adaptive Optics, etc. In addition, μLEDoS technology is applied to Augmented Reality (AR), Head Up Display (HUD), Head-mounted Display (HMD), and Wearable Devices.

One of the key technologies to evolve in the displays market in recent years is liquid crystal over silicon (LCOS) microdisplays. Traditional LCOS devices and applications such as rear projection televisions, have been based on intensity modulation electro-optical effects, however, recent developments have shown that multi-level phase modulation from these devices is extremely sought after for applications such as holographic projectors, optical correlators and adaptive optics. Here, we propose alternative device geometry based on the flexoelectric-optic effect in a chiral nematic liquid crystal. This device is capable of delivering a multilevel phase shift at response times less than 100 microsec which has been verified by phase shift interferometry using an LCOS test device. The flexoelectric on silicon device, due to its remarkable characteristics, enables the next generation of holographic devices to be realized.

: This report discusses the results of a Honeywell Technology Center program focused on developing thermal management methodologies and flip-chip-on-glass (FCOG) driver bonding techniques which are key to ruggedizing automotive-grade commercial off-the-shelf (COTS) active matrix liquid crystal displays (AMLCD) for use in military applications like the F-16 high-performance fighter environment. Through extensive thermal modeling, several techniques were identified to facilitate heat flow away from the temperature-sensitive liquid crystal material, keeping the core temperature within acceptable operating limits (below +85 C) in worse case conditions (200 fL with +50C ambient and 883Watts/mA2 solar load in a closed cockpit) without the use of forced air cooling for display sizes up to 5x5-inch. Environmental testing on eight modified Sharp displays verified modeling results. The FCOG bonding has many mherent advantages over traditional tape automated bonding (TAB) techniques, one of which is 75% reduction in off-glass interconnect density, making them much less susceptible to vibration failure. Several FCOG bonding materials (e.g., anisotropic conductive films) have been explored and tested using various test vehicles and subjected to F-16 environmental conditions for temperature shock, temperature cycling, vibration, and humidity.

Surface-stabilized antiferroelectric liquid crystals (AFLCs) and V-shape smectics share the spontaneous generation of intermediate transmission states, i.e. analogue grayscale. On the other hand, liquid crystal on silicon (LCOS) appears to be a promising alternative to thin-film transistors (TFTs) in the preparation of reflective microdisplays and spatial light modulators (SLMs). The feasibility of preparing LCOS SLMs using AFLC and V-shaped LCs has been analyzed. A comparative study of a number of AFLC and V-shape materials as candidates for LCOS SLMs has been carried out. Test cells below 1 µm have been prepared using an ITO-coated transparent glass plate and an aluminized silicon back plate mimicking the actual LCOS device. AFLC waveforms compatible to low-voltage operation of the silicon backplane have been demonstrated. V-shape waveforms have been designed and demonstrated as well. The results show that both LC families may be employed in this specific application. Dynamic behavior, with frame rates over 200 Hz, is especially remarkable.

We propose a precise circuit model to estimate transient optical responses of an active-matrix liquid crystal display (AMLCD). Liquid crystal (LC) molecules in the pixel is behaviorally modeled by using the first-order system that is described by Verilog-A. Capacitance-voltage (C-V) characteristics of a pixel determine the accuracy of the dynamic responses. Measuring C-V characteristics is impossible because pixels are driven by switching transistors in the AMLCD. We propose a method to obtain the C-V data from natural optical responses. Estimated optical responses based on the C-V data extracted by our proposal show more accurate results than those based on C-V data obtained by using transmittance-voltage data. It is demonstrated that our behavioral model enables us to predict very accurate transient responses, which makes it possible to design LCD products with lower costs.

The performance of advanced flat panel displays is intrinsically linked to critical properties of the substrate material. In the manufacture of active-matrix liquid crystal displays (AMLCDs) and some emissive displays, there are certain process steps that require extreme conditions such as strong chemical washes and temperatures in excess of 600°C. As a result, the glass substrate used in these displays must be able to withstand these environments without degradation of its properties. It has become apparent that the flat panel display (FPD) manufacturers will benefit from substrates with improved acid durability, higher temperature capability, and thermal expansion coefficients consistent with other display materials.This paper focuses on one of the less-understood features of the glass substrate: the expansion characteristics as a function of temperature. Thermal expansion is important as it affects the compatibility of the glass with display materials, which, in the case of AMLCDs and some silicon-microtip field emission displays (FED), require an expansion close to that of silicon. In addition, thermal breakage during processing is directly proportional to the expansion coefficient.This study focused on the thermal expansion characteristics of two different FPD substrate glasses. The first one is code 7059, manufactured by Corning Incorporated and currently the standard in AMLCDs. A new substrate composition, Corning code 1737, with enhanced durability, temperature capability, and expansion tuned to the AMLCD applications will also be discussed.

According to the advent of ubiquitous world, the requirement for the mobile information devices with high display quality and compact device size is surprisingly increased. Among the diverse candidates for this mobile display system for mobile devices, Liquid Crystal on Silicon (LCoS) is the most competitive device due to the high aperture ratio and simple fabrication process. The inorganic liquid crystal (LC) alignment layers are widely used for LCoS devices because of the thermal and photochemical stability. In this work, the reactive sputtering was selected for the preparation method of inorganic LC alignment layers. The nitrogen (N2) gas had the effect on the deposition process of SiO2 and the surface morphology of SiO2 thin layers were affected by the N2 mixing ratio of sputtering gas. In addition, the LC alignment properties on SiO2 thin layer were also closely related with the N2 mixing ratio and other sputtering conditions. In the case of high RF power of reactive sputtering, the N2 mixing ratio has little effect on the LC alignment on SiO2 thin layers. However, in the case of low RF power of reactive sputtering, the LC alignment properties were enfeebled by increasing the N2 mixing ratio. This result might be attributed to the change of the surface morphology of inorganic SiO2 thin layers.

A novel liquid crystal on silicon (LCOS)-based wavelength selective switch (WSS) is proposed, fabricated, and demonstrated. It employs a multilayered arrayed waveguide grating (AWG) as a wavelength multiplex/demultiplexer. The LCOS deflects spectrally decomposed beams channel by channel and switches them to desired waveguide layers of the multilayered AWG. In order to obtain the multilayered AWG with high yield, phase errors of the AWG is externally compensated for by an additional phase modulation with the LCOS. This additional phase modulation is applied to the equivalent image of the facet of the AWG, which is projected by a relay lens. In our previously-reported WSS configuration, somewhat large footprint and increased cost were the drawbacks, since two LCOSs were required: one LCOS was driven for the inter-port switching operation, and the other was for the phase-error compensation. In the newly proposed configuration, on the other hand, both switching and compensation operations are performed using a single LCOS. This reduction of the component count is realized by introducing the folded configuration with a reflector. The volume of the WSS optics is 80 × 100 × 60 mm3, which is approximately 40% smaller than the previous configuration. The polarization-dependent loss and inter-channel crosstalk are less than 1.5 dB and -21.0 dB, respectively. An error-free transmission of 40-Gbit/s NRZ-OOK signal through the WSS is successfully demonstrated.