Light Control Film for Cholesteric LCD Image Quality Enhancement Speaker: Ching-Yao Huang (黃靖堯) Advisors: Prof.Yi-Pai Huang (黃乙白教授) Prof.Chung-Hao Tien (田仲豪教授) Institute of Electro-Optical Engineering, National Chiao Tung University, Hsinchu, Taiwan Oct.13 2008

Outline Introduction Motivation and objective Simulation module Conclusions and future works

Introduction of Cholesteric LCD E-book Billboard Advantages: Low power consumption Stable structure No color filter Disadvantages: Specular reflection The glare effect Color shift

Outline Introduction Motivation and objective Simulation module Conclusions and future works

Motivation Line light source X LCF Viewing region Substrate Electrode Alignment layer LCF Cholesteric LC Ch-LCD Viewing region Alignment layer Electrode Substrate The lens specification can be determined by the position of light source, display, and viewers.

The position of light source and display size Objective Measurement (BRDF of the display) Indoor large billboard Ch-LCD The position of light source and display size Optical film Mathematical module Film design Light source The viewing region Uniform illumination

Outline Introduction Motivation and objective Simulation module Conclusions and future works

BRDF Bidirectional reflectance distribution function(BRDF) Definition: BRDF defines the reflective characteristic of the surface.

Simulation Structure 10cm 20cm 30cm 14.03 ° 5.71 ° 180cm 160cm 20mm LCF Up glass Ch-LC cell Low glass Light source Light source 20cm 10cm Ch-LCD 30cm 14.03 ° 10mm 20mm 5.71 ° 180cm 160cm 2m 15mm

Microstructure ρ=25° ρ=50° ρ: incident angle σ: reflection angle α, β: inclined angle of slope ρ=60° The mark area is the slope range of micro-lens corresponding to the expected reflection angle.

Simulation result The reflected light redistributed to the expected region by adding the LCF in front of the display. Bare Ch-LCD With LCF

Outline Introduction Motivation and objective Simulation module Conclusions and future works

Conclusions The design process can get the appropriate parameters of the micro-lens. The angular distribution of reflected light with LCF redistributed to the expected value in simulation. The incident angle can’t be too large that causes the shadow effect.

Future Works Realize the design of LCF . Verify the design process with the experimental result and improve if there is any drawback. (1) BRDF (2) Experimental setup

Thanks for your kind attention

The curved surface can be expressed as: Its tangent vector is: The wavefront unit vector of incident light

Light source

Conic constant k = 0 sphere -1 < k < 0 ellipse with major axis on the z axis k = -1 parabola k < -1 hyperbola k > 0 oblate sphere (ellipse swept about minor axis)

Planar texture Focal conic texture Homeotropic texture