||Liquid crystal display (LCD) has been widely used as an important human interface with typical portable devices such as notebook-type computers, digital camera and cell phones, etc. The LCD panel does not emit light spontaneously, and thus it needs a surface backlight source. The function of light guide plate (LGP) was to guide light from a light source and radiates it homogeneously from all over its output surface. In this thesis, the research object was focused on this optical component. |
This thesis mainly concludes two major parts. The first part focused on the design of cold fluorescent lamp (CCFL) light source LGP. If the bottom structure of the LGP in a backlight module was made up of V-Cut micro-structures, then conventionally, the shape and spacing between any two adjacent columns of micro-structure should be designed specifically in order to obtain a more uniform illuminance distribution. It was required to apply complicated mathematics and cost a lot of time to design. In this study, a simplified bottom structure of the LGP was proposed. The considered bottom structure of the LGP was proposed to be made up of same shape high energy V-Cut micro-structures, and the spacing between any two adjacent columns of the micro-structure was also the same. The design parameters were determined by using optimization technique. Also, the LCD design time could be reduced. In order to eliminate the dark region phenomenon caused by the proposed simplified bottom structure of the LGP, a simple new type of edge structure of the LGP was proposed also. The proposed simplified LGP design concepy has many merits, such as only three design parameters needed, manufacturing easily, the design time can be reduced, and can prevent the consumption of light source energy between the gaps of CCFL and LGP. The proposed design concept was applied on the design of 7 inches, 15 inches and 20 inches of backlight module (BLM). Through the numerical simulation by utilizing commercial software Light Tools, it can be shown that more than 80% of uniformity can be easily obtained.
The second part focused on traditional dot pattern bottom structures. As the same concept mentioned in the first part, the proposed dot pattern was made up of same geometrival shape of dots, and the spacing between any two adjacent columns of the dots was also the same. The design parameters were determined by using optimization technique. The
proposed design concept of the dot patten distribution can be applied on the design of LGP with either LED or CCFL light source. Also, the dark phenomenon did not occur, and so the corresponding edge structure did not need either. The proposed design concept was applied on the design of 7 inches, 15 inches and 20 inches of BLM with CCFL light source and on the design of 7 inches of BLM with LED light sources. The optical simulation results showed that about 90% of uniformity can be easily obtained.