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如何改善等离子显示器的亮度--新西兰essay代写范文

2016-11-17 来源: 51Due教员组 类别: Essay范文

新西兰essay代写范文:“如何改善等离子显示器的亮度”,这篇论文主要描述的是通过从用减色法混合颜色方法将显示器中的光亮环境进行改善,在保证显示器保持在明亮的状态下,减少显示器的功耗,有许多的研究人员专门针对PDP进行了研究,其中对液晶显示屏的研究发现,LCD在提升亮度降低功耗方面是比较落后甚至是劣质。

essay代写,Plasma Display Panel,留学生作业代写,减色法,论文代写

摘要 Abstract

We researched to minimize the loss of luminance on display

area and reflection luminance to improve ambient contrast in bright circumstance.

According to the result of our research, we propose that you'd better use compliment colors on transparent dielectric layer and barrier rib of rear glass (rear panel) applying to color's being dark when mixed instead of using a black stripe pattern so as to lowering reflection luminance. We've applied this technique to 42inch VGA panel that shows reflection luminance was diminished to 63% and ambient contrast at 150-lux light was improved from 93:1 to 151:1 recording the improvements of 61% in comparison with conventional panel with black stripe; which is the best result for ambient contrast under the bright circumstance in the PDP panels are being researched.

1. Introduction

Nowadays, as the Digital TV market is growing rapidly in these days, there has been a severe competition to take the initiative on the large-sized flat panel display market among display companies and the sorts of displays such as PDP vs. LCD.

In case of plasma display panel (PDP), many researchers have made a special study of PDP to achieve high brightness and low power consumption that were considered as an inferior specification to other displays including LCD. Besides those specifications, consumers are demanding to increase emotional picture quality in display recently. Therefore, many technologies in PDP currently being investigated to improve ambient contrast that is inferior to the competitor LCD in order to acquire a clear picture quality. Ambient contrast depends on reflection luminance and luminance of display (or display brightness) and reflection luminance is fatal factor especially. The most powerful one in conventional techniques to decrease reflection luminance is using the black stripe pattern between sustain electrodes (bus electrodes) in front glass. However this technique limits the design of panel structure due to electrode line location and cannot decrease reflection luminance below some degree.

In this paper, to minimize the loss of brightness of display and reflection luminance to improve ambient contrast, we proposed new technology that compliment colors are applied in both front and real panel respectively and investigate effect on reflection  luminance and brightness of display in comparison with conventional panel with black stripe pattern

2. The mechanism of reflectance and transmission

As mentioned above, the ambient contrast is directly related to the ratio of luminance of light emitted and transmitted by the front panel and the residual light reflection of ambient light. Thus it is important to understand the mechanism of both reflectance and luminance in panel. Figure 1 and 2 show the schematic diagram of reflection of ambient light and transmission of light emitted by RGB phosphors respectively. Simple description of optical prince- -ples is very helpful to design the panel structure that the ambient contrast improves. First of all, we consider the mechanism of reflectance. Equation 1 expresses simple model of reflectance. As shown in Eq. 1, the reflection luminance is the total sum of the intensity of reflected light on the consecutive interface.

Reflectance on air-glass interface (R1) and glass-dielectrics interface (R2) is about 4%, 0.4% respectively. When these factors substituted into (1), we can get approximately

TL3 : transmittance on dielectrics and open area

A : The percentage of surface area of barrier rib in cell structure

Therefore the reflectance luminance depends on the reflectance of barrier rib (R3) and phosphor (R4), the area of barrier rib, and transmission through front dielectrics. To decrease reflection luminance, many methods to control these factors are used. For example, light that transmitted through front dielectrics (TL3), and reflected in barrier rib (R3) decreases by applying the black stripe

Fig. 1. The schematic diagram of reflectance of ambient light in panel

IT1 = IP×(1-A)× TL2×TL3

IT2 = IP×A× Tp×Rrib × TL2×TL3 (2)

ITL ≈ IL1+IL2 ≈ (0.9-(1-0.27Rrib)A TL2)IP

TL2 : transmittance on dielectrics and open area

TL3 : transmittance on glass

IL1 : direct transmission of light

IL2 : indirect transmission of light

TP : Transmittance through phosphor

RP : Reflectance on barrier rib

IP : light emitted by phosphor

in front panel commonly. In another method that barrier rib change white color into black or gray color, R3 is also decreased. In case of transmission of light in panel, the mechanism of transmission of light is divided into two processes as shown in Fig.

2. One is transmission of light directly through the front glass. The other is transmission of light after light emitted the direction of phosphor area reflects in barrier rib at first. Equation 2 represents to the mechanism briefly. Tp is almost 30%. As shown in (2), the transmission of light depends on transmittance of dielectrics, reflectance of barrier rib, and surface area of barrier rib. Therefore the controllable main factor is barrier rib and dielectric layer.

3. Experiments

3.1 Design concept

In the preceding chapter, we observed the main factors of both reflectance and transmission in panel briefly. When luminance considered, reflectance and area of barrier rib are control factors to decrease reflection luminance and major reason is due to rib color. It is noted that many research have been performed to remedy for these factors and limit the loss of brightness due to reflectance of barrier rib shown in (2). Therefore it must be considered following as

1) The method that reflectance of barrier rib in ambient light decrease and that in light emitted by phosphor increase at the same time.

2) The method that transmittance of front dielectrics decrease in non-emitting area to minimize loss of brightness

Thus we use the subtractive mixture of colors in this work. Fig. 3 shows the characteristics of color in light and paint. When the three primary colors of light are mixed, the intensities of the colored light are being added. This can be seen where the primary color illumination overlaps. The yellow formed when red light is added to green light is equal to the illumination of the red and green combined. This mechanism is used in the display. By the way, the primary colors for mixing paints, inks, and dyes, are not the same as for mixing light. The red, blue, green of light mixing adds colors to make new hues. The magenta, cyan, and yellow of mixing pigments and dyes subtract colors to create new hues. This is subtractive mixture of color.

3.1 Fabrication and evaluation

Figure 4 shows the schematic diagram of both the conventional method and the new one that is suggested in this paper. In order to exclude effects of cell structure in ambient contrast, we used the same cell structure in both conventional and SMC panel except the method applied to decrease reflectance of ambient lighting. In the CMC panel, both barrier rib and upper transparent dielectric layers paint in brown and dark blue color respectively instead of using black stripe pattern. Experimental measurements were

carried out on 42inch VGA panel. Brightness of panel was measured with luminance meter (Minolta, CA-100plus). Panel color is investigate by using CIE L*a*b* color base. Reflectance in panel and color of panel are measured by using electrophotometer (Minolta, CM-2600d).

Reflection luminance is expressed at the circumstance that 150-lux light illuminate panel and is calculated by equation 3 defined as RL = (Rsce /100) × 47.7 (3)

where RL is the reflection luminance, Rsce is the Reflectance that is the Y component of SCE (secular component excluded) mode in CIE XYZ color space with standard A light source, and it

Fig.2. Schematic diagram of transmission of light emitted

by phosphor

Fig.3. The schematic diagrams of (a) subtractive mixture

of color and (b) additive mixture of light

Fig.4. Schematic diagram of cell structure fabricated in

both the conventional method (with black stripe) and the

SMC method

(a) Conventional panel (b) SMC treated panel

Fig.5. Characteristics of reflectance and decrease of reflectance with respect to panel type. The solid line is for reflectance in various panel types. The dot line is for decrease of reflectance in comparison with the reference is 47.7 cd/m2 that 150-lux light converts in luminance. To evaluate contrast efficiency, equation 4 was used Eac = DL / DR (4) where Eac is ambient contrast efficiency, DL is the decrease of 1% window brightness and DR is the decrease of reflection luminance in comparison with reference panel. The ambient contrast is define to the ratio of reflection luminance to brightness in panel as below

CR = (Lmax + Lambient) / (Lmin + Lambient) (5) with Lambient = RL × Eambient / π RL is the diffuse luminous reflectance of ambient illumination (Eambient). RL is the absolute reflectivity weighted against the spectral (photopic) response of the human eye versus wavelength.

The diffusely reflected surface luminance of display is calculated as RL × Eambient / π [3].

3. Result and discussion

Figure 5 shows the reflectance in various panel types. The reflectance of the panel applied the subtractive mixture of colors (SMC) is decreased more than any other panel using the reflectance reduced methods. In case of the reflectance with the SMC method, especially decreased by 44% compared with the conventional one with black stripe patterns. The reflection luminance can be acquired by substituting the reflectance for (3) and the results are indicated in Fig. 6. In case of SMC treatment, the reflection luminance is below 10cd/m2 contrary to contrast enhancement treatment with black stripe pattern. To increase ambient contrast there is two ways. One is increasing brightness of panel. However this method has been saturated in conventional cell structure. At the reason of that, it is important that reflection luminance can be decreased below 10 cd/m2 to enhance ambient contrast and clear image to the end. To investigate characteristics of profile and intensity in ambient luminance, the color image

mapping was measured as shown in Fig. 7. The distribution of reflection luminance is similar between panel applying black stripe and one with SMC treatment. But the intensity of reflection Ref black stripe black rib SMC

Decrease of reflectance (%) luminance in SMC panel is lower than one in conventional panel with black stripe patterns. Because the value of reflection luminance in Fig. 7 is not absolute but relative, the result between in Fig.6 is compared with one in Fig. 7. However it is agrees with that the SMC treatment is powerful in decreasing the intensity and area of reflection luminance. Though the reflectance decrease easily in conventional method that is applied increase of the width in black stripe or black color in barrier rib. However, according to these methods, the brightness of panel decreases radically. As a Fig.6. Characteristics of reflection luminance in various panel types

(a) Conventional panel with black

Fig.7. Color image mappings of reflection luminance in

(a) conventional panel with black stripe patterns and

(b) panel with CMS treatment.

Panel Type

Reflection luminance (cd/m2) (b) Panel with SMC treatment

Fig.11. Characteristics of color in CIE L*a*b* with respect to color layers (barrier rib and dielectric layer). A black square dot indicates zero point that is black color result, the ambient contrast is constant and decreased. For this reason, it is important to ratio of the loss of brightness of panel to that of reflection luminance shown in fig.8. The result proves that the reflection luminance decreases more than brightness. The SMC effect is efficient in comparison with black stripe method to increase ambient contrast. The ambient contrast that converts according to (1) in 150-lux light is shown in fig. 8. In case of applying the SMC technique to panel without black stripe, the ambient contrast shows a 61% increase over the conventional panel with black stripe pattern. The Figure 9 is the result of the ambient contrast as a function of gray level in 16 gray bar pattern

that is 256 gray levels were divided to 16 levels. The effect of in ambient contrast is increased in comparison with conventional panel with black stripe. Especially in low gray levels, the ratio of contrast in SMC technique to black stripe is so high that the panel with the SMC method is more benefit to express low gray level.

In addition, because we can feel the gray level that higher that the reflection luminance, the lower gray level is conscious in the panel with SMC treatment. As a result, image can be expressed clearly in ambient circumstance by using the SMC technique. To investigate whether subtractive mixture of colors occurs, we measured a*b* value of color [1] in contact area and the result is shown in Fig. 11. If subtractive mixture of colors occur, (a*, b*) coordinate approach to zero point that is indicated to black color level. In case of applying either brown color barrier rib or dark blue dielectric layer, a*b* coordinate become more distant compared with reference a*b* color value (black stripe color).

Panel Type

Ambient Contrast at 150 lux the (a*, b*) coordinate approach to zero when brown color barrier rib and dark blue color dielectric layer are contacted.

4. Conclusion

The conventional technique using black stripe patterns to reflection luminance limits the design of panel structure due to electrode line location and cannot decrease reflection luminance below some degree. In addition, it needs to detail alignment between front and real glass panel because of complexity.

In this work, to minimize the loss of brightness of display and reflection luminance to improve ambient contrast, we applied new technology that compliment colors are used in both barrier rib and front dielectric layer respectively. As a result, subtractive mixture of colors occurs in the contact area of both color layers and the reflection luminance decrease up to 7 cd/m2 in 42 inch VGA panel, which achieve to 151:1 ambient contrast in 150-lux light circumstance.

Fig.8. Ratio of the loss of brightness of panel to that of reflection luminance in various panel types

Fig.9. Characteristics of ambient contrast of in 150-lux light with respect to panel types

Fig.10. Characteristics of ambient contrast at the function of gray levels. Solid line is the panel with SMC treatment and dot line is conventional panel with black stripe patterns.

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