Yung-Yuan Kao

A new low-voltage-driven GRIN liquid crystal lens with multiple ring electrodes in unequal widths

This work is dedicated to design a novel liquid crystal (LC) lens device with multiple ring electrodes in unequal widths, in order to offer tunability on focusing quality and to lower the level of applied voltage. The number and widths of the multiple ring electrodes are pre-designed and optimized to offer the on-line tunability on individual electrode voltages to render a better refraction index distribution for focusing, as compared to the past hole-type LC lenses. The resulted refractive index distribution is expected to offer similar focusing effects based on the theory of the gradient refraction index (GRIN) lens. The transparent electrodes of this new LC lens are placed at the inner surface of the LC cell to minimize the driving voltages, in results, less than 10 V, for the same level of focusing power and an easy practical operation. A new fabrication process in the wafer level to bury bus lines is developed for generating smooth electrical fields over the lens aperture. In addition, a dielectric layer is coated between electrodes and the LC layer.

11.1: An Auto‐Stereoscopic 3D Display Using Tunable Liquid Crystal Lens Array That Mimics Effects of GRIN Lenticular Lens Array

A tunable liquid crystal lenticular lens array is proposed to compose an auto-stereoscopic 3D display. The focusing can be achieved based on non-uniform phase retardation across the width of the LC lenticular lens, mimicking the effects of gradient index (GRIN) lens. The viewing distance and zones of this display can be adjusted in an on-line fashion to track the viewer position relative to the display. The proposed scheme can present the lenticular lens and the LC GRIN lens simultaneously, so that the simulation results can express the low value of crosstalk of 9% by the lenticular lens array and the LC GRIN lens array.

A New Dual-Frequency Liquid Crystal Lens with Ring-and-Pie Electrodes and a Driving Scheme to Prevent Disclination Lines and Improve Recovery Time

A new liquid crystal lens design is proposed to improve the recovery time with a ring-and-pie electrode pattern through a suitable driving scheme and using dual-frequency liquid crystals (DFLC) MLC-2048. Compared with the conventional single hole-type liquid crystal lens, this new structure of the DFLC lens is composed of only two ITO glasses, one of which is designed with the ring-and-pie pattern. For this device, one can control the orientation of liquid crystal directors via a three-stage switching procedure on the particularly-designed ring-and-pie electrode pattern. This aims to eliminate the disclination lines, and using different drive frequencies to reduce the recovery time to be less than 5 seconds. The proposed DFLC lens is shown effective in reducing recovery time, and then serves well as a potential device in places of the conventional lenses with fixed focus lengths and the conventional LC lens with a single circular-hole electrode pattern.

A new negative liquid crystal lens with multiple ring electrodes in unequal widths

This study is dedicated to the design of a new negative liquid crystal (LC) lens with multiple ring electrodes in unequal widths. The number and widths of the multiple ring electrodes are designed to offer online tunability on focusing length by predetermined individual electrode voltages. This aims to render a smooth refraction index distribution that mimics well a divergent lens based on the theory of a gradient refraction index (GRIN) lens. Finally, the proposed negative LC lens is fabricated with the capability of realizing different focus lengths in a relatively large aperture of 5 mm and a thickness of 0.7 mm. Experiments are conducted to verify expected light-diverging performance. The effective focus length (EFL) is measured based on interference patterns. It is shown that the proposed negative LC lens is able to realize light-divergent effects with an EFL as short as -357.9 mm.

3.4: Sizing Multi‐electrodes in an LCL‐lens for Minimizing the Crosstalk in a 3D Auto‐stereoscopic Display

A liquid-crystal-lenticular-lens LCL-lens with multi-electrodes is proposed to realize an auto-stereoscopic 3Ddisplay. The focusing ability provided by this LCL-lens can be achieved based on non-uniformpotential across the LC-layer, which mimics the effects of GRIN-lens. Moreover, the crosstalk is thoroughly analyzed in varied observer-distances and viewer-angles via the ray-tracing method.

Tracking, recognition, and distance detection of hand gestures for a 3-D interactive display

— This study proposes an interactive system for displays, the technologies of which consists of three main parts: hand-gesture tracking, recognition, and depth measurement. The proposed interactive system can be applied to a general 3-D display. In this interactive system, for hand-gesture tracking, Haar-like features are employed to detect a specific hand gesture to start tracking, while the mean-shift algorithm and Kalman filter are adopted for fast tracking. First, for recognizing hand gestures, a principal component analysis (PCA) algorithm is used to localize colored areas of skin, and then hand gestures are identified by comparison with a prepared database. Second, a simple optical system is set up with an infrared laser source and a grid mask in order to project a proposed horizontal stripe pattern. Third, the projected patterns are deciphered to extract the depth information using the Hough-transform algorithm. The system containing hand-gesture localization, recognition, and associated depth detection (the distance between the display and the hand), was included in a prototype of an interactive display. Demonstration of rotation recognition of a finger-pointing hand gesture was successful by using the algorithm of radar-like scanning.

An LCL-Lens Array with Electrodes of Interlaced Structure in Applications of Auto-Stereoscopic

Commercial auto-stereoscopic display systems have equipped optical lenticular lens sheets in order to realize the function which is able to support two images or views to right and left eyes of viewers. In applications of auto-stereoscopic display, the method of using the lenticular lens sheet, also called time- or spatial-multiplexed method, is first proposed as a patent by Ichinose [1]. The method has more advantages, which includes high luminous performance, movable of eyes position with constant view distance and watchable of multi-viewer. Besides, it can be also easily manufactured to make it very popular. Owing to the superiority, some studies about lenticular lens sheets have been proposed. Berkel et al. [2] have proposed several researches about the method of using lenticular lens sheets on multi-view auto-stereoscopic displays, and he has also proposed that slanted lenticular lens sheets or pixels could be improved the effect of flipped image by boundaries of lens and pixel [3–5]. 2D/3D switchable display is first realized by a method of dual-lenticular lens sheets [6]. Moreover, the method of using lenticular lens sheets has been proposed to be replaced by liquid crystal, LC, lens arrays, [7–9] in order to control viewer distance based on a function of tunable focal length. For the method, some issues of LC lenses should be solved like non-smooth potential in the LC layer and to improve the lens power [10–12].Copyright

Developing a quality assessment method for evaluating focusing quality of an LC lens used in an optical pickup

The liquid crystal (LC) lens with multi-ring electrodes for cameras in cell phones is designed in this study based on theoretical analysis, simulations and optimization. This study starts with the calculations to show that a substantial size reduction of a lens module can be offered by an insertion of LC lens. As compared to conventional cameras, the lens module in phone cameras particularly requires shorter focal length (around 8cm) and larger aperture (greater than 3 mm). The currently available LC lenses, however, fails to provide both the above capabilities. To remedy the problem, the method to design a large-aperture LC lens with multi-ring electrodes is developed in this study, and a new quality-assessment method is developed to evaluate the designed multi-ring LC lens via point spread function (PSF) and modulation transfer function (MTF). The number and widths of the ring-type electrodes are further optimized to reach certain required levels of PSF and MTF for the LC lens. This is achieved by designating a finite number of ring electrodes first and then assigning the width of each electrode proportional to the slope of the required applied voltage along the radius of the LC lens. Optimization results show that the three-ring LC lens with ring widths particularly designed reached satisfactory MTF of 65% for 5 and 48% for 7 line pairs per millimeter, which are not increased significantly even with the ring number increased to seven.

P-194: Tracking Hand-gestures with Depth Detection for a 3D Interactive Display

This study proposes a new system for tracking and recognizing the human-hand, furthermore distance between hand and camera can also be measured the capabilities of hand-tracking and depth-detection. One of the algorithms is able to track the hands in real time with a camera. Another one detects the depth from the sensing camera to the hands.

Performance prediction of a small-sized herringbone-grooved bearing with ferrofluid lubrication considering cavitation

The small-sized herringbone groove journal bearing (HGJB), i.e., so-called “magnetic bearing,” filled with Newtonian ferrofluid lubrication is investigated via finite difference analysis (FDA), with consideration of cavitation zones in HGJB. The FDA starts with constructing the mass flux equations of the HGJB filled with ferrofluid. Discretization for FDA is next performed over the bearing clearance domain, from which algebraic finite difference equations based on the mass flow balance over the clearance domain are derived. Solving the equations, rotordynamic coefficients, cavitation zones, and side leakage rate are successfully predicted to show effectiveness in enhancing bearing performance by ferrofluid.