Research on Holography and Optics in Flat-Panel Displays
|School||Shanghai Jiaotong University|
|Course||Information and Communication Engineering|
|Keywords||Holography Interference 3D display Backlight module Ambientcontrast ratio|
Holography is known for its ability to reconstruct light field with bothintensity and phase information by recording interference fringes of twocoherent light waves in a recording material. It is an important researchsubject in modern optics, and has been widely used in light shaping, lightfield recording, wave-front reconstruction. Due to recent advance in micromechanical machining, especially the emergence of spatial light modulator,holography is able to get rid of the recording materials, and modulates boththe intensity and phase of the light field freely. Before the emergence of thistechnology, researchers in display area have already used the concept ofbinocular parallax to achieve3D display, and find some applications in3Dmovie and3D TV, but these applications are not the real3D display. However,the invention of SLM(Spatial Light Modulator) will lead to an ’UltimateDisplay’, the holographic3D display, which simulates the light field of realobjects and scenes by using the SLM to modulate both intensity and phase ofthe incident light, and creates a virtual reality for the viewers. Thus theresearch on the key technologies of holographic3D display based on SLM isof great theoretical and practical importance, and will be widely used in thefuture3D display realm.In this paper, recent researches on SLM based holographic3D displaysystem is firstly briefed, important conclusions on current holographic3Ddisplay system is then analyzed, and requirements on the backlight modulesused in SLM based holographic3D display system is thoroughly discussed, atlast a coherent backlight module well fit in a flat-panel design is proposed.Other researches concerning the contrast ratio of traditional LED displaysystem and OLED display system are also presented.In the research on the coherent backlight module, SLM based3D displaysystems are thoroughly analyzed, aiming to understand the structure of these systems and the important conclusions already presented, then therequirements on the backlight modules used in SLM based holographic3Ddisplay system are summarized, and limitations of current SLM based3Ddisplay system in a flat-panel design are listed. Based on this, a compactcoherent backlight module is proposed, and the feasibility of its keycomponent is verified by a proof-of-concept experiment.In OLED display, holography is used to improve the ambient contrast ofthe current OLED devices. Important factors in the ambient contrast issue ofthe OLED devices are studied, and a break-through has been made that iscompletely different from current methods. We propose to use a holographiclayer that reacts differently to the ambient light and the emitted light fromOLED, so that reflection of ambient light into the viewing zone of the deviceis suppressed while the emitted light from OLED is unaffected within theviewing zone.In traditional LED display, a new optical design is proposed to improveboth the off state appearance and the on state ambient contrast ratio of thecurrent LED display panel. In previous designs, brightness of the panel iscompromised for a better off state appearance, leading to higher powerconsumption. By comprehensively considering the existed problem, aninterference based device is proposed to deflect the ambient light while thelight emitted from the LED panel remains unaffected. Through simulation,one can see that not only the off state appearance is improved, but also the onstate ambient contrast ratio is promoted.