Eun-Jung Lee

Emotional Image Quality Evaluation Technology for Display Devices

In this paper, we explained the relation between evaluating display device and emotional image quality evaluation in human perceptual view. It is also suggested two emotional image quality evaluation method of display reflecting human visual function. One is the color space of CIECAM02 and the other is capturing moving image. It is necessry to standardize the evaluation methods of image quality based on emotional evaluation.

Optimum perceived-brightness level considering the practical use environment for the mobile organic light-emitting diode display

ABSTRACT The white-luminance display is generally considered the representative value for screen brightness, but it is not always proportional to the users’ perceived brightness. The demand for the brightness of the display also changes depending on the actual use conditions, such as the ambient condition, contents, viewing object, and display device characteristics. It is important to differentiate the perceived brightness of the display by considering the device characteristics and the use conditions. A display device with a lower black level and a high saturated primary color can make the users satisfied by emitting even a relatively low luminance level. This is the result of the simultaneous contrast and Helmholtz–Kohlrausch effect. A visual experiment considering various illuminant conditions and actual use contents proved that the perceived brightness for OLED is different from the white-luminance value. It is expected that the new luminance criteria developed herein will be used for reproducing high-quality videos like those made with HDR, one of the newly rising image-quality technologies.

A study on the ergonomic aspects of the proper luminance level of displays

In this paper, a displays emotional image quality can be primarily determined by designing the proper luminance level. Though displays with high luminance are preferred, too much light emission from a display may cause glare or visual fatigue to viewers. To find out the proper luminance level based on various video contents, this study was conducted with an OLED display with a real-black level and a wide color gamut, and with an LCD display with a high luminance level, to set the glare threshold under various conditions. The optimum luminance levels according to the displays loading ratio were found, and the maximum luminance that did not cause a glare in the test is proposed.

P‐48: A New Approach Toward Visual Clarity Assessment Using Perceptual Contrast Length

Contrast ratio is one of the most important performance parameters used to evaluate visual clarity of displays. However, conventionally-used absolute contrast ratio value has imperfect correlation to human perception of image quality. A new measurement method, called perceptual contrast length (PCL), is proposed as an improved standard for measuring contrast. Based on human perception tests under various conditions, PCL is shown to have higher correlation to human perception of image quality.

Improved Angle-of-View Measurement Method for Display Devices

Abstract With the increasing demand for a better FPD image quality, better evaluation metrics and advanced display quality measurement methods are required to meet these needs. There are many measurement methods for evaluating the viewing angle of various display devices, but these methods, which include luminance drop, color shift, and contrast ratio decrease, are imperfect considering that human perception does not completely correlate to them. In this paper, a new method of measuring the perceptual angle of FPDs is proposed, considering human visual perception, which uses the color space of the color appearance model.

Extraction of location and energies of traps in nanoscale flash memory using RTN

Recently, several reports have been published on RTS noise which brings about large Vu, fluctuation in floating gate flash memory. However, they have primarily looked at the RTS distribution of the main array without providing a detailed description of the physical mechanism and have not discussed the location and energy of traps. In this paper, we accurately extracted the location (vertical and lateral position) of traps and trap energy from RTS noise. Also, we extracted the trap locations and trap energies with simultaneous extraction method in the device having two traps which shows complex RTS noise.

Two-Phase Flow Simulation of Molded Underfill Process to Mitigate Void and Assure Reliability at Product Level

Molded Underfill (MUF) process, used in Stacked-Up Package Technology, suffers from void formation that significantly impacts yield and compromises reliability at the product level. However, a concrete methodology, to resolve such issues, remains unclear due to the complexity of package structure and convolution of viscous material flow during MUF process. In this paper, we focus on the formulation of void nucleation mechanism and solution to optimize the MUF process. Based on empirical assessments, Computational Fluid Dynamics (CFD) was employed to simulate Epoxy Molding Compound (EMC) flow through bump array in a metal mold frame, where air and liquid EMC coexist as a two-phase flow. When EMC enters the solder bumps, attached to silicon IC in a metal mold, a vortex flow tends to develop due to unbalanced EMC flow associated with bump distribution and pressure gradient during the MUF process. In particular, the vortex flow occurred near the vent zone, in which there is a relatively lower molding pressure compared with the molding entrance. This hardly prevents void nucleation, from air trapping into viscous EMC, which significantly affects micro void formation and leads to a short fail during reflow and solder mount. In fact, location and size of voids depend on bump design such as bump density and structure. Intrinsic key parameters for void formations from MUF process include mold flow direction, cavity pressure, and bump array. Finally, a practical guideline to suppress voids and optimize MUF package process is delivered to ensure a mature and reliable production.

The crease perception in flexible display

There is a growing possibility applied to the foldable display for mobile devices because consumers want to see the big screen and they prefer mobile devices easy to carry around. However, a foldable display has crease because it generally uses laminated films or plastic substrates. In this study, we conducted the experiments in which people perceive crease on the flexible display for the various display viewing environments. The result shows that subjects most easily perceived crease in a bright room and panel off-state when the folding radius is 5u2009mm (5R). They perceived crease at an average height of 143u2009µm in that condition. The subjects perceived crease at an average height of 185.5u2009µm in the outdoor with display off condition. Also we analyzed that the subjects perceived the crease better when the folding radius of the flexible display was smaller than 5R. We expect that this study will contribute to the standardization of the new assessment method and to setting perception standards for the flexible display.