Yi-Kai Cheng

Irradiance formations in hollow straight light pipes with square and circular shapes.

We investigated, both analytically and numerically, the irradiance formation of an asymmetrically located Lambertian light source in hollow straight light pipes with square and circular shapes. The uniform irradiance distribution in a square light pipe and hot-spot localization in a circular light pipe were examined and determined semianalytically. Typical factors of influence, such as light-pipe length, width, and source size, were identified with extensive simulation. When the ratio of light-pipe length and width was less than 0.5, the deviation from uniformity could be more than 20%. But once the source size was large enough (approximately half of the incident port), such that the Lambertian characteristics of the source dominated the irradiance distribution, the uniformity deviation was reduced. Furthermore, a quantity of root-mean-square circular differences was defined in order to identify the shape deformation of the light pipe; it was found that the peak value of the hot spot decreased exponentially with the deformation scale. The influence of nonperfect reflectivity of the pipe wall on irradiance formation was also examined for a square light pipe; when the reflectivity is larger than 90%, the difference in uniformity is less than 10% and uniform irradiance remains, provided that the ratio of light-pipe length and width is larger than 1; even the source is located asymmetrically.

Irradiance formations of on-axis Lambertian pointlike sources in polygonal total-internal-reflection straight light pipes.

Different geometric shapes of light pipes cause different irradiance distributions. We analytically explore the irradiance distributions of on-axis Lambertian pointlike sources in polygonal total-internal-reflection (TIR) straight light pipes. It is analytically shown that the irradiance of pentagonal light pipes concentrates on the center of the exit plane. Numerical verifications are also provided, and experimental explorations with different shapes of acrylic light pipes are carried out for comparison. We also analyze the influence of light-pipe length on distribution uniformity and deduce the smallest uniform-mixing length/circumradius ratios for polygonal light pipes.

Analysis and reduction of dark zone in ultra-thin wedge-plate displays

— A wedge plate can be used as the screen of a display, and the thickness of the display can be incredibly thin. In this paper, a basic formula for ray tracing in such a wedge plate is deduced. The fundamental limitation on the display quality of a wedge plate is explored, and the formation of a dark zone on the display screen is analyzed and verified numerically. Experimental exploration and confirmation of one 14-in. acrylic wedge plate with a white-light-emitting diode is also provided. Two approaches to eliminate the dark zone are proposed, and the corresponding numerical demonstration of a 52-in. wedge-plate display is also shown.

Aberration analysis of a wedge-plate display system.

The aberration characteristics of a wedge-plate display optical system are analyzed. The study shows that a kink-like feature is inherent in the ray-intercept curve due to either the onset of the dark zone in imaging or the coincidence of the ray direction with the vertex. Third-order aberration coefficients are deduced, and the total amount of aberration is investigated to illustrate the basic limitations of image quality in this type of display. The issue of design optimization is also investigated based on the aberration characteristics. A numerical example of a 50 in. display with a 1:10 thickness and a diagonal screen length ratio is also provided.

Far-Infrared Resonance in Split Ring Resonators

We experimentally investigated the resonance effect of planar metallic split ring resonators (SRRs) in the far-infrared region (FIR) (~10.6 µm). Experimental results indicated that they exhibit resonance around 10.6 µm, implying negative permeability in the FIR region. Furthermore, the ratio of effective dimensions of the SRR cell and the wavelength of the incident beam was around 1 which suggested a wide scale independence. This size tolerance is useful in realizing the meta-materials with negative indices of refraction in the optical wavelength domain.

P‐157: Aberration Analysis of an Ultra‐Thin Wedge‐Plate Display

The general aberration behavior of an ultra-thin wedge-plate display is analytically analyzed and numerically verified. Experiment over a plastic Acryl wedge plate with incident-controlled light from a collimated diode laser is also performed to identify the aberration. As an exploration, a 2.5-inch thick wedge display that with 50-inch screen diagonal, in which the ratio of the thickness versus the screen diagonal is 1:20, is analyzed.

Electrically driven nanoarrow array green LED

An electrically driven nanopyramid green light emitting diode (LED) was demonstrated. The nanopyramid arrays were fabricated from a GaN substrate by patterned nanopillar etch, pillar side wall passivation, and epitaxial regrowth. Multiple quantum wells were selectively grown on the facets of the nanopyramids. The fabricated LED emits green wavelength under electrical injection. The emission exhibits a less carrier density dependent wavelength shift and higher internal quantum efficiency as compared with a reference c-plane sample at the same wavelength. It shows a promising potential for using nanopyramid in high In content LED applications.

Polarization-preserving angular shifter

We propose two types of light pipes, namely wedge and circular forms, the incident direction of light propagation could be rotated as necessary while still preserving beam polarization. We also deduce the basic conditions of these preservations of polarization. Several typical cases of light pipes are analyzed by numerical simulation. As one of the examples, it is verified that a collimated beam with +45 degree linearly polarization can be guided to any pre-settled direction where the ellipse ratio variation in polarization is less than 0.1%.

P‐214: Wedge‐Plate Type Circular Display

We propose a wedge-plate type circular display (WCD) and its imaging characteristics are explored and verified by extensive simulation. As a demonstration, the projection of black-and-white and color images on a desk-top WCD that with 20-inch screen diagonal is presented. Critical parameters, such as plate length, or display quality are also evaluated.

P‐213: Imaging and Chromatic Behavior Analysis of a Wedge‐Plate Display

We deduced the basic formula of ray tracing in a wedge plate and investigated, both analytically and numerically, the imaging behavior of wedge-plate display. As an exploration, a 2-inch thick wedge display that with 52-inch screen diagonal, in which the ratio of the thickness versus the screen diagonal is 1:25, is analyzed. The chromatic behaviors are also clarified. Keyword: Wedge plate display, chromatic shift