全色域移动显示与四原色液晶显示器的发展--Essay代写范文

Essay代写范文:“全色域移动显示与四原色液晶显示器的发展”，这篇论文主要描述的是四原色技术的成功研发大大提高了液晶显示器在色彩表现方面的性能，并且成为了研发下一代液晶显示器的重要基础，在原有的红绿蓝三色的基础上，新加了多个混合的彩色液晶，如素红、蓝色、黄绿色等等满足了全色域移动显示的需求，也能够达到低功耗的设计理念。

Abstract

We developed a multiple color LCD with pixels composed of red (R), blue (B), yellowish green (YG) and emerald green (EG) sub pixels, combined with a white LED backlight. The color gamut was extended to 105% of the NTSC standard. Also the 3- to 4- primary-color conversion algorithm using the three-dimensional look-up-table (LUT) is described with the color reproduction characteristics for driver-integrated circuits on mobile LCDs. 

1. Introduction

LCDs are widely used as displays in applications where powerconsumption is critical, such as cellular phones, PDAs, and notebooks PCs. The growing demands of mobile broadcasting,visual telecommunications, and viewing photographs have made wide color gamut characteristics as well as contrast and brightness of mobile LCDs the most important features for the next generation mobile products.Various types of LCD have been demonstrated to meet these requirements and to realize a world of “Color Image Matching” where images taken with a camera are equivalent to printer performance levels, and print output has the same level of quality as the image in the digital still camera’s (DSC) LCD viewfinder(Figure 1). For example, more than three primary-color per sub pixel type displays were reported for TV applications [1].

However, these prototypes have been developed for commercial use, due to rising costs, gaps in the technology and excessive power requirements.

Figure 1.

“彩色图像匹配”的基本概念Basic concept of “Color Image Matching”

We have developed a new, mobile, direct view, wide color gamut, 4-primary-color LCD called “Photo Fine Chromarich”. This mobile LCD reproduces a wide color gamut to more than 100% of the NTSC gamut by using newly developed red, blue, yellowish green (YG), and emerald green (EG) color filters, combined with a typical white LED backlight. In this paper, we describe the key technologies for developing this 4-primary-color LCD such as (1) the optical properties and sub pixel arrangements of the color filters, (2) white LED backlight and (3) color conversion algorithms, and we present the color characteristics and the display performance of fabricated panels.

2. Methods and Results

2.1 The 4-primary-color filter system

Standard LCDs use red, green, and blue (RGB or 3-primary-color) filters to produce the color sub pixels that combine to produce color images on the displays. These conventional RGB primary color LCDs cover only about 40% to 70% of the NTSC gamut and are not good at displaying cyan or emerald colors. But the market demands a deeper, richer and more vivid overall color gamut. In a conventional LCD with RGB sub pixels, the color gamut can be increased by making a narrower spectrum of color filters, but this leads to lower transmission of the LCD panels. To extend the color gamut of LCDs they can also be combined with an RGBLED back-light, but these systems have low power efficiency, are thicker than conventional white LED systems and are white point temperature-dependent. Alternatively, color sequential LCDs do not need a color filter and can have both a relatively large gamut and high transmission. But they need very high frame rates to avoid flicker, and to eliminate color break up.

Figure 2. Concept of 4-primary-color filter and a micro-photograph of a filter

To overcome these trade off problems, we have developed a new 4-primary-color filter. Figure 2 shows the basic concept of the 4- primary-elements color filter. The conventional green color is divided into YG color and EG color. By adopting YG a rich Golden Yellow color of gold or fallen leaves can be achieved that conventional 3-primary-color LCDs have difficulty in displaying.

Also, EG enriches Emerald and Cyan color areas found in images of deep mountains and dark valleys or deep water. In addition,thickening the Red and Blue primary colors makes it possible to have a far wider reproduction gamut of over 100%. Figure 2 also shows a microphotograph of the newly developed 4-primary-color filter.

2.2 Sub pixel arrangements

To minimize the occurrence of edge pseudo colors in the new 4-primary-color system, we studied the relationship between sub pixel arrangements and the occurrence of edge pseudo colors using visual simulations. For the development of 4-primary-color mobile LCDs, we considered all sub pixel arrangements and evaluated their S-CIELAB based simulation results. The details of the S-CIELAB function are described in Reference [2] and [3] with the complete conversion parameters. Figure 3 shows two examples of sub pixel arrangements and the results of visual simulations using the S-CIELAB function for the 4-primary-color filters with a non sub pixel type display. Although all candidates of the sub pixel arrangements have twelve patterns for the four color filters, Figure 3 shows two representative arrangements, the B-YG-R-EG order and the R-B-EG-YG order, because these orders showed the best and the worst characteristics respectively in the simulations.a) Non sub pixel (b) B-YG-R-EG (c) R-B-YG-EG

Figure 3. Results of visual simulations of the sub pixel arrangements using the S-CIELAB function a) Non sub pixel (b) B-YG-R-EG (c) R-B-YG-EG

Figure 4. L*a*b* graphs of sub pixel orders

The edge blur, which is mainly caused by the human visual contrast sensitivity, occurs for all cases in Figure 3, however no pseudo colors arise at the edge area with the non-sub pixel type. The L*, a*, and b* graphs (Figure 4) of the B-YG-R-EG ordershow the better profiles, which are similar to the non-sub pixel type. The simulation image of a vertical line for the B-YG-R-EG order shows fewer blurring and less pseudo colors. The same simulation result is shown in Figure 5 using the word “New” and the B-YG-R-EG order adopted as the best sub pixel arrangement for 4-primary-color filters. Figure 5. Simulation images of the word “New”

2.3 Backlight

To expand gamut values, RGB-LED or color sequential backlight systems can be used [4][5]. But with RGB-LED, for a good white image, white balance must be adjusted by coordinating each current intensity, and both methods result in relatively high power consumption that is not allowable in mobile applications. So we combined a conventional white LED backlight system with the 4-primary-color LCD to achieve a wide gamut LCD with low power consumption suitable for mobile applications.

Figure 6 shows the typical optical properties of our white LED, and it is clear from the figure that the shape of the transmission curve is almost the same as the backlight systems of commercially available cellular phones. Due to the green tinged appearance of our newly developed 4-primary-color system (that is obvious from Figure 2), we adjusted the peak wave length of the white LED to move to a shorter wave length for compensating greenish LCD panels to white. By controlling the peak wave length of the white

LED we were able to achieve a good white image in spite of using green-area-doubled color filters. This backlight system achieve a simple LCD module with low power consumption suitable for mobile applications. Figure 6. Optical property of backlight system

2.4 Color conversion

Generally, input signals from the main system to the LCD modules is consists of R, G, B signals. Some 3- to multi primary color conversion algorithms have been reported for multi primary color displays [6] [7], however a simple algorithm involving low hardware cost and low power consumption was needed for multiprimary color mobile LCDs. To optimize these signals for the 4- primary-color system, we developed 3- to multi primary color conversion algorithms for the driver-integrated circuit in the mobile LCD. Figure 7 shows the outline of the newly developed color conversion algorithm from 3- to 4-primary color. The algorithm includes the gamma conversion, the 3- to 4-primarycolor conversion and the inverse gamma conversion to calculate 4-primary-color in a linear space.

Figure 7. Color conversion algorithm

To get a simple conversion algorithms, we compared the 4x3 matrix conversion with the 3-grid 3-dimantional look-up-table (3DLUT) conversion as a candidate of 3- to 4-primary color conversion algorithm.The 4x3 matrix algorithm converts the color by the following Equation (1), where 4x3 matrix MA is determined by the leastsquares method between (R1,G1,B1) and (R2,YG2,B2,EG2).

Figure 8 shows the structure of 3-grid 3DLUT algorithm. The converted data, (R2,YG2,B2,EG2) are located at its each grid of cubic. For the conversion, (R2,YG2,B2,EG2) data sets are loaded and the interpolation using the sets is performed according to the location of the input.

Figure 8. Structure of 3DLUT

Table 1 shows the color reproduction error using the CIE 1994 color difference equation delta E94 between the target color and the reproduced color, where the target color space is set to Adobe RGB. The 3-grid 3DLUT color conversion algorithm achieves a better color reproduction result than the simple 4x3 matrix color conversion. Figure 9 shows the photographs of the reproduced images displayed on the same 4-primaly-color LCD panel, which represent that the 3DLUT conversion is actually suitable for the

reproduction of real images.

Figure 9. Photographs of the reproduced images

We also developed a driver IC that uses this color conversion algorithm. The IC contains the gamut expanding algorithm in compressed form, so there is no need to increase the main memory of the products. With this color conversion system, if conventional 3-primary-color signals are input, the system embedded in the LCD drive circuit converts it to a 4-primarycolor signal, and as the input data still in 3-primary-color format, with this technology old displays can simply be replaced with the new models.

3. Experimental results

Table 2 shows the product performance of LCDs featuring this new technology. In all models we achieved a wide gamut over 100% of the NTSC ratio in spite of the combination with a white LED backlight system. Even though high pixel pitches and the 4- primary-color panel has 4/3 times as many columns as a 3- primary-color panel, it did not have any problem in displaying images.

Table 2. Product specifications of newly developed LCDs

Panel size 2.2" 2. 8" 4.5"

Type of TFT LTPS LTPS a-Si

Numbers of

pixels 240 x 320 640 x 480 640 x 480

Numbers of

colors 16,777,216 16,777,216 262,144

Pixel pitch 185 ppi 290 ppi 180 ppi

NTSC ratio 108 % 105 % 108 %

Backlight White LED White LED White LED

LCD type Transmissive Transmissive Transmissive In Figure 10, the color points of the 2.2" panel (red line) and a typical color reproduction area of an inkjet printer (green line) are shown in combination with Adobe RGB (triangle). It is clear that this technology enables the sRGB area (not shown in the figure) to be filled in, and almost all the Adobe RGB colors, and colors like emerald green and blue can be reproduced to the same level as an inkjet printer which was not previously possible in small and medium sized LCDs (screens currently on mobile phones cover with an average of about 50%).

Figure 10. Measured color coordinates of a 2.2" panel and the gamut of inkjet printer Figure 11. Pointer’s gamut and 2.2" panel gamut

Figure 11 shows the color points of a 2.2" panel (trapezoid) and Pointer’s Gamut [8] (colored line) which is a well known standard of natural real surface color. The coordinates of magenta are somewhat in disagreement with each other, but almost all Pointer’s Gamut points are covered by our 4-primary-color LCD. To put it differently, our 4-primary-color LCD with a white LED backlight can reproduce almost all natural real colors.

4. Conclusion

We have developed the first direct view, R-B-YG-EG, 4-primarycolor LCD. The gamut of the panel exceeds 100% of the NTSC ratio using a white LED backlight. The arrangement of 4-sub pixels is best in B-YG-R-EG-order according to the results of SCIELAB- based simulations. This paper also presented a color conversion algorithm from 3- to 4-primary-color with the color reproduction results. Based on the color reproduction results, we adopted a reasonable and effective color conversion algorithm for the driver integrated circuit in the mobile LCD.

From the comparison between Pointer’s gamut and our 4-primary-color LCD it is clear that our new LCD can reproduce almost all natural, real colors. In conclusion, our new 4-primary-color LCD “Photo Fine Chromarich” offers very attractive performance for high end mobile applications.

51due留学教育原创版权郑重声明：原创留学生作业代写范文源自编辑创作，未经官方许可，网站谢绝转载。对于侵权行为，未经同意的情况下，51Due有权追究法律责任。

51due为留学生提供最好的服务，亲们可以进入主页了解和获取新西兰essay代写的相关资讯 提供以及美国作业代写辅导服务，详情可以咨询我们的客服QQ:800020041哟。-xz