Research On The Super Restoring OLED-on-silicon Microdisplay

The microdisplay is a special type of display. Its physical size is rather small, butit may create large view size through the optical system. It can be used in the projectorsand the NTE (Near-To-Eye) systems. With the technical progressing of the organiclight emitting, the microdisplays based on the OLED (Organic Light Emitting Diode)begin to grow these years. Compared with the currently dominating microdisplays likeDMD (Digital Mirror Device) and LCD (Liquid Crystal Display) microdisplay, theOLED microdisplay has its special feature, such as self light emitting, solid statedisplay, light weight and thin, full color gamut, low driving voltage, fast response,wide temperature adaptation, low power, etc. This dissertation will give research on themanufacture process, the scan algorithm, the driving circuit and the system design forthe OLED-on-silicon microdisplay. The content includes:1. Discuss the principle and the manufacture process flow of the OLED-on-siliconmicrodisplay. Propose the one-time process flow for the pixel anode patterning of thebackplane silicon chip based on the semiconductor process instead of the traditionaltwo-time process flow. Design a test chip with the pixel anode metal using Al and TiN,and fabricate the OLED on the surface of the chip to obtain a test OLED-on-siliconmicrodisplay. The test result shows, when the pixel anode metal is Al and the drivingvoltage is4.8V, the current density will reach0.11mA/mm2and the luminance reach1472cd/m2and so the light efficiency is13cd/A. The current density and the luminancewill be higher when the pixel anode metal is TiN. These results provide the physicaldevice basis for designing the OLED microdisplay.2. Analyze the structure of the human eyes and the vision generating process.Discuss the luminance and chrominance response of the eyes. Propose the conceptionof the super restoring display. Propose the optimal scan strategy for the super restoingdisplay and build its fractal model based on the time-space mapping topology structurefor the digital scan of the flat panel display. Discuss the advantage of the optimal scan strategy on eliminating the time redundancy to improve the scan efficiency and reducethe hardware requirement. Also discuss the advantage of the optimal scan strategy onincreasing the display resolution to higher than HD (1920×1080) and increasing thegrayscale level to higher than4096. Give stress on the nonlinearity correction, thegamma correction and the hardware requirement of the optimal scan strategy whichwill provide a new solution to the super restoring OLED microdisplay.3. Analyze the traditional amorphous silicon and the poly silicon based TFT(ThinFilm Transistor)-OLED pixel driving circuits and the single crystal silicon basedMOSFET(Metal Oxide Semiconductor Field Effect Transistor)-OLED pixel drivingcircuit. Propose the current source PWM (Pulse Width Modulation) pixel drivingcircuit particularly for the optimal scan strategy. This circuit will create the accuratecurrent PWM signal to drive the OLED pixel with the digital PWM driving method.On the other hand, this circuit will also provide the current compensations for theOLED pixel degradation non-uniformity. The simulation results show that the staticcharacteristics and the dynamic characteristics of the current source PWM pixel drivigcircuit can meet the timing requirement of the super restoring OLED microdisplay.4. Research on the system design of the OLED-on-silicon microdisplay which isdivided into two parts: the silicon backplane chip and the optimal scan controller.Discuss the design methodology on the pixel driving circuit array, the row driver, thecolumn driver and the digital circuit, and also discuss the design methodology on theanalog-digital mixed circuit deisgn of the full chip. Show the silicon backplane chipdesign and tape out sample. The display resolution supports1280(×3)×1024. The testresults show the chip will create4096grayscale levels when the pixel clock is about100MHz. Also discuss the design methodology of the optimal scan controller based onthe time-space topology sequence. Give the design examples of all the sub-modules ofthe optimal scan controller. Show the result of the FPGA (Field Programmable GateArray) implementation of the optimal scan controllerThis dissertation researches on the full development flow of the OLED-on-siliconmicrodisplay, discusses the design methodology of the super restoring display andgives the develop examples to prove the design method. It provides a new solution for researching and developing the super restoring OLED-on-silicon microdisplay. Finally,it shows the development platform of the OLED microdisplay, exhibit its excellentdisplay feature and look forward to its application in the near future.