Moojong Lim

Analysis of angular dependence of 3‐D technology using polarized eyeglasses

— The cause of the angular dependence of 3-D technology that requires the use of eyeglasses with linear or circular polarization is analyzed. For 3-D technology that requires the use of eyeglasses, anisotropic media such as a polarizer or retardation film determines the polarization state. Therefore, the angular behavior of 3-D display performance is also affected by the characteristics of the anisotropic media that have intrinsic angular dependence. Various conditions of the optic axes of the imaging display and eyeglasses are investigated to understand their effect on 3-D display performance. The result shows that some conditions of the optic axes can cause non-negligible degradation of 3-D display performance.

Response time characteristics of optical shutter of vertical alignment liquid crystal cell for obliquely incident light

The temporal transmittance of a liquid crystal (LC) cell shutter was investigated for various incident angles to verify the possibility of a fast switching time. For a mono-domain vertical alignment (VA) cell, the switch OFF time in which the LC restores to its initial alignment state under no driving voltage is found to relate to the angle of the incident light. A decrease of switch OFF time is observed when the azimuth angle of the incident light approaches the azimuth angle of the LC optical axis. For a 4-domain VA cell, switch OFF time is observed not to decrease for any obliquely incident angle.

Analysis of the dependence of optical response time of liquid-crystal displays on the viewing direction

— The optical response time of liquid-crystal displays (LCDs) has recently been observed to be dependent on the viewing direction. For the vertically aligned LC mode, response time increased as the viewing angle increased when the final state is the zero gray level of the minimum luminance. This change in response time is analyzed to relate to the deformation of the normalized luminance curve of LCDs for different viewing directions. The dependency trends of the optical response time for the oblique direction can be estimated from the temporal luminance measurement data along the normal direction and the normalized luminance curve for oblique viewing directions.

Investigation on optical performance of transparent displays

Transparent displays have been expected to widen the scope of display application utilizing see-through function. There are, however, few studies on transmitted image quality of transparent display until now. This paper, therefore, describes the optical performance of transparent displays. In order to evaluate transmitted see-through performance, novel evaluation method, named purity, was developed by measuring the amount of light which can form a transmitted distinct image. The new proposed method could tell how clear the see-through image can be seen, and is consistent with viewers perception. Our study would give suggestions on the development of transparent displays.

Determination of luminance distribution of autostereoscopic 3D displays through calculation of angular profile

— The luminance distribution of autostereoscopic 3-D displays using the parallax-barrier method was simulated by two different calculation methods. The first method directly calculates the total luminance distribution by summing light rays coming from different positions on the imaging display through a parallax barrier at each eye position. The second method first calculates the angular distribution of light rays coming from the imaging display through a parallax barrier and then derives the spatial luminance distribution for each eye position. The two methods resulted in an equivalent distribution. Yet, the second method outperforms the first method in terms of calculating the speed and versatility.

Evaluation method of electro-optical transfer function for display devices

— Various gamma-evaluation methods are investigated and newly suggested in order to establish a standard gamma metrology. First, test patterns are suggested and compared for display technologies that dynamically adjust gray levels such as global-dimming LCDs and PDPs. Second, two gamma-determination methods are compared and their accuracy determination methods are suggested. Third, two new models for gamma-distortion phenomena are suggested. Finally, the monotonic characteristics of EOTF are investigated. For the most part of this study, a new international standard named ICDM-DMS is suggested.

Image quality evaluation of LCDs based on novel RGBW sub-pixel structure

Many display manufacturers have studied RGBW pixel structure adding a white sub-pixel to RGB LCD and recently revealed UHD TVs based on novel RGBW LCD. The RGBW LCD has 50% higher white luminance and 25% lower primary color luminance compared to RGB LCD. In this paper, the image quality of RGBW and RGB LCD was dealt with. Before evaluating them, TV broadcast video and IEC-62087 video were analyzed for test video clips. In order to analyze them, a TV reference video from TV broadcast content in Korea was firstly collected. As a result of TV reference video analysis, RGBW LCD was expected to improve image quality more because most of colors are distributed around white point and population ratio of achromatic colors is higher. RGB, RGBW and RGBW using wide color gamut (WCG) backlight unit (BLU) LCDs were prepared, and a series of visual assessments were conducted. As a result, RGBW LCD obtained higher scores than RGB LCD about four attributes (‘Brightness’, ‘Naturalness’, ‘Contrast’ and overall image quality) and ‘Colorfulness’ was not higher score than RGB LCD in test still images. RGBW LCD’s overall image quality in the TV reference video clips also was assessed higher than RGB LCD. Additionally, RGBW LCD using WCG BLU shows better performance about especially ‘Colorfulness’ than RGBW LCD.

Moving-picture response time (MPRT) of LCDs for the oblique viewing direction

Abstract— The dynamic performance of displays is an important characteristic for multimedia applications. Motion-picture response time (MPRT) has been used as an indicator of the dynamic performance of LCDs. This paper describes a comprehensive method of MPRT evaluation for the oblique viewing direction. By using a tilted camera configuration, the angular dependency of MPRT is investigated for the condition that the horizontally scrolling patterns are observed from the vertical direction. For each gray-to-gray transition, distinct changes in MPRT and the luminance profile of blur are observed.

P‐83: The Correlation of MPRT and Moving Picture Resolution with Actually Perceived Moving Image Qualities

The motion picture response time (MPRT) methods have been widely used to evaluate the degree of motion blurs in display devices such as liquid crystal displays (LCDs) and plasma display panels (PDPs). Recently, APDC (Advanced PDP development center Corporation) announced the moving picture resolution method to represent the moving image quality of FPDs by using a resolving power as a measure. However, there are some differences in evaluation results of these two methods for same display devices. In this study, we measured the moving picture resolutions of five different FPDs which have different MPRT values and compared these results with actually perceived moving image qualities. The results show that the MPRT has higher correlation with actually perceived moving image qualities than the moving picture resolution method.