Tomoyuki Okuyama

Artificial retina using thin-film photodiodes and thin-film transistors

An artificial retina using thin-film photodiodes (TFPDs) and thin-film transistors (TFTs) is proposed, which is expected to be suitable for living bodies, low-emitting and cost-effective, and which is an improvement of the system-on-panel devices in which the in-pixel and pixel-to-pixel operations are executed using TFTs. The characteristics of a TFPD and TFTs are measured, and their models are made for a circuit simulator. Circuits of the retina pixel and retina array with some improvements are invented, and it is confirmed using a circuit simulator that the artificial retina using TFPDs and TFTs can operate. Edge enhancement is also confirmed, and its dependence on the characteristic deviations of TFTs is analyzed.

Classification of Driving Methods for TFT-OLEDs and Novel Proposal Using Time Ratio Grayscale and Current Uniformization

Driving methods for TFT-OLEDs are explained with their features and classified from the viewpoints of grayscale methods and uniformizing methods. This classification leads us to a novel proposal using time ratio grayscale and current uniformization. This driving method maintains current uniformity and simultaneously overcomes charging shortage of the pixel circuit for low grayscale levels and current variation due to the shift of operating points. Tolerance toward degraded characteristics, linearity of grayscale and luminance uniformity against degraded characteristics are confirmed using circuit simulation.

Time-Ratio Grayscale and Hopping Scan with Current Uniformization for Thin-Film Transistor Driven Organic Light-Emitting Diode Displays

A driving method using time-ratio grayscale and hopping scan with current uniformization has been developed for thin-film transistor (TFT) driven organic light-emitting diode displays. The easiness of pixel charging is superior to that of conventional current program driving. A TFT characteristic is measured, and design parameters are optimized. It is confirmed using a circuit simulator that this driving method maintains current uniformity and simultaneously overcomes charging shortage of the pixel circuit for low grayscale levels and current variation due to the shift of operating points. The influence of feed-through voltage can be neglected by optimizing design parameters. Moreover, it is also confirmed using an image simulator that grayscale linearity and luminance uniformity against the TFT characteristic deviation are much improved.