Tatsuya Sugita

Collimated Light Source Using Patterned Organic Light-Emitting Diodes and Microlens

We developed for the first time a collimated organic light-emitting diode (OLED) light source using a patterned OLED and a microlens. The structure of the collimated OLED light source was designed by conventional ray-tracking simulation. We demonstrated that the collimated OLED light source enhanced the luminance of a liquid crystal display (LCD) with a low aperture ratio by a factor of more than two compared with a conventional OLED light source, which was not patterned. The collimated OLED light source with the patterned OLED and microlens is thus very effective for achieving a highly efficient LCD with OLED backlight.

Optical time-domain reflectometry of bent plastic optical fibers

Optical time-domain reflectometry (OTDR) signals of step-index plastic optical fibers (POFs) and graded-index POFs were measured with a laser diode and an avalanche photodiode. When bent step-index and graded-index POFs were used, the OTDR signal behavior differed. The OTDR signal of the bent graded-index POFs had a step that corresponds to a curvature loss, but the step-index POFs had a spike signal at a bend, which indicated the occurrence of backscattering. The peak intensity was proportional to the square of the curvature. The refractive-index variation of the bent step-index POFs was measured, and the dependence of the peak intensity on the curvature was shown to agree with that predicted by the scattering from the refractive-index perturbation.

Bidirectional optical coupler for plastic optical fibers

We have developed a low-loss bidirectional optical coupler for high-speed optical communication with plastic optical fibers (POFs). The coupler, which is fabricated by an injection molding method that uses poly (methyl methacrylate), has an antisymmetric tapered shape. We show that the coupler has low insertion and branching losses. The tapered shape of the receiving branch reduces beam diameter and increases detection efficiency coupling to a photodetector, whose area is smaller than that of the plastic optical fiber. The possibility of more than 15-m bidirectional transmission with a signaling bit rate up to 500 Mbits/s for simplex step-index POFs is demonstrated.

Aberration properties in a chirped grating for coarse wavelength division demultiplexing

We studied the imaging performance of a chirped grating for a demultiplexer designed for coarse wavelength division multiplexing using a wavefront aberration analysis and the ray tracing simulation. The demultiplexer was composed of a chirped grating, cylindrical lenses, and a waveguide. The best image point and the spot shape focused by the chirped grating were effectively calculated with the wavefront aberration. We applied the aberration analysis to design a waveguide to connect branched beams to photodetectors, and we confirmed the demultiplexing performance experimentally.

Evaluation of Electrophoretic Migration of Submicron Particles in a Microgap by Optical and Current Responses

We studied the electrophoretic migrations of submicron particles in nonpolar inks sealed in narrow gap cells of 5.3 µm by using optical and current responses. We evaluated the mobility of particles by using the optical responses of the total reflection at interfaces between electrodes and the solvent in addition to simultaneously measuring current, from which the concentrations of ions and charged particles were analyzed. The mobility of the particles in the narrow gap was similar to that of the bulk ink, except for the case with no charge director and less dependence on the charge director concentration. We also analyzed how the mobility was distributed and how the particles interacted with the interface by using the optical responses.

P‐192L: Late‐News Poster: Moiré Reduction of Luminance Enhanced LCDs with a Wobbled Micro‐Lenticular Lens

We developed a novel lenticular lens, whose edge lines were modulated with a sinusoidal form, for a luminance enhanced LCD to reduce moire fringe between lenses and prism sheets and demonstrated the moire reduction to 1/5 with the wobbled lenticular lens formed by a printing method.

Pattern generation method by direct toner irradiation

A novel method for toner pattern generation is proposed. The image pattern is simply formed by direction of a light flash through a pattern mask to expose toner on a transparent support. The force of movement from light of which the optical energy density was 0.73 J/cm(2) and the exposure time was 0.43 ms FWHM was estimated to be more than 2.8 x 10(-9) N. The cause of the transfer was examined, and ablation of toner was determined to be the most likely. If this method can be applied to a printer, a simple process to form images may be realized.

Evaluation of Electrophoretic Migration by Optical and Current Responses to Cyclic-Polarity-Reversed Triangular Voltage

We studied the electrophoretic migration of electrophoretic inks by measuring the total reflection at the interface between the electrode and the ink solvent simultaneous with the current response to a cyclic-polarity-reversed triangular voltage. We demonstrated that the current peaks and optical responses to the cyclic-polarity-reversed triangular voltage are effective for the easy evaluation of mobility, the charge amount of ions and ink particles, and the interactions of particles with the electrode and inter-particles. The mobility of the ink particles was measured from the slopes of these peak voltages as functions of the square root of the time rate of the scanning voltage. The offset of line extrapolation indicated the interaction of the particles with the electrode. The optical response was effective for measuring the mobility even when the conductivity of the cell was too large to detect the drift current peaks.

P-249L: Late-News Poster: Collimated OLED Light Source with Patterned OLED and Microlens

We developed for the first time a collimated OLED light source using a patterned OLED and a microlens. We demonstrated that the collimated OLED light source enhanced the luminance of an LCD with low aperture ratio by a factor of more than two compared with a conventional OLED light source, which was not patterned. Moreover, the luminance efficiency of this system was shown to be 7.3 times higher than that of the system with a conventional OLED light source that was not patterned. The collimated OLED light source with patterned OLED and microlens is thus very effective for achieving a highly efficient LCD with OLED backlight.

Segmented chirped grating for coarse wavelength division demultiplexing with multimode optical fibers

A chirped grating segmented into partitions each having a constant blaze angle to use in a demultiplexer for coarse wavelength division multiplexing with multimode optical fibers is developed. Its designed configuration utilizes a resonance region to achieve high diffraction efficiency and large dispersion. The width, blaze angle, and diffraction order of each partition were optimized by vector diffraction analysis. The diffraction loss of the manufactured grating was less than 1.5 dB, and polarization-dependent loss was less than 0.6 dB within a wavelength width of at least 70 nm. It is confirmed that a demultiplexer with the developed chirped grating had a wide passband and low cross talk.