We have developed novel active matrix driving technology integrating red-green-blue (RGB) microscale light emitting diodes (micro LEDs) and a microscale integrated circuit (micro IC) in each pixel for the Crystal LED display system. The small size and closely placed RGB subpixels of micro LEDs enabled us to achieve an outstanding contrast ratio even in a bright environment. We also achieved superior luminance linearity and chromaticity stability using accurate pulse width modulation (PWM) driving by micro ICs in the active matrix system. To integrate micro LEDs and micro ICs into a scalable display system, an additional fine-patterned layer was applied to a conventional printed circuit board (PCB). In addition, with precise tiling technology, we could produce a large-scale image providing an immersive visual experience. K E Y W O R D Sactive matrix, Crystal LED display, micro IC, micro LED, pulse width modulation | INTRODUCTIONLight emitting diodes (LEDs) have been widely used in general lighting, traffic lights, backlights for liquid crystal displays, and outdoor billboards. LEDs are currently attracting attention as emission devices for display applications that have high energy efficiency, a long lifetime, high brightness, high color purity, and a short response time. In recent years, the use of microscale LEDs (micro LEDs) for emissive display pixels has been proposed and reported by many researchers. [1][2][3][4][5] We have been developing micro LEDs for high-quality display applications. High-quality display applications require not only the micro-sizing of LEDs but also their uniformity in electrical/optical characteristics, precise assembly technology for arraying them, a driving method, and system integration.In 2012, we demonstrated the first prototype of the Crystal LED display, shown in Figure 1, at the Consumer Electronics Show (CES). 6 The display was 55 inches

We have developed a novel active matrix driving technology integrating RGB micro LEDs and a micro IC in each pixel for the Crystal LED display system. With precise tiling technology, a large‐scale image with superior quality can be produced. We will present related key technologies in this paper.

We previously reported a novel optical pick-up using a confocal laser coupler (CLC) and the confocal push-pull (CPP) method of detecting tracking-error signals. The CPP method is very stable in the face of the lens displacement of the optical pick-up, but it remains to determine whether the optical pick-up can be applied to optical disk systems of various parameters. In this paper, the inherent characteristics of the CPP method of detecting tracking-error signals are discussed based on the results of numerical analysis and experiments.

A forward phase-conjugate beam was generated using a copper-doped (K0.5Na0.5)0.2(Sr0.61Ba0.39)0.9Nb2O6 (Cu:KNSBN) crystal with Cat type self-pumped phase-conjugator incident geometry. This Cat self-pumped phase-conjugator was formed simply with a small incident beam diameter of 0.4 mm at an incidence angle of 30°. In this configuration, the forward phase-conjugate beam could be generated at the same time with the self-pumped phase-conjugate beam. Furthermore, it was possible to generate the forward phase-conjugate beam while maintaining the high reflectivity of the self-pumped phase-conjugate beam. A forward phase-conjugate reflectivity of 0.9% was achieved at a self-pumped phase-conjugate reflectivity of 12%.

We propose a novel optical pick-up using a confocal laser coupler for an optical disk player. The laser coupler consists of a glass window and a monolithic optical element which includes a laser diode, 8 photodiodes, and a pyramid-shaped prism mirror positioned near the confocal plane which acts as a knife edge and a photo-coupler. The focusing-error signal is detected using the confocal knife edge (CKE) method and the tracking-error signal is detected using the CKE push-pull method. The jitter of Compact Disc (CD) readout was 6.7 ns at a line velocity of 1.2 m/s, and the DC offsets of the tracking-error signal were sppressed to less than 1/3 for a radial lens displacement of ±400 µm compared to the conventional push-pull method.