• Journal of the Architectural Institute of Korea Structure & Construction
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• v.35 no.5
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• pp.191-202
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• 2019

This study examines the effect of luminance contrast ratio of character on readability and visual fatigue during an hour-long reading session while using a tablet PC in ambient environments having low luminance limited to $25cd/m^2$. Experiments were conducted with four patterns of the tablet's luminance contrast ratio of characters, namely 1:2.5, 1:4.5, 1:6.5, and 1:8.5, in low ambient luminance of $9cd/m^2$ and $25cd/m^2$. The obtained results show that the characters can be easily read at the luminance contrast ratio of character of 1:8.5 under surface luminance of $25cd/m^2$. Visual fatigue was evaluated through a subjective survey of symptoms. Physical, psychological, and visual fatigue were observed at a surface luminance of $9cd/m^2$, whereas solely visual fatigue was felt at a surface luminance of $25cd/m^2$. By assessing the physical fatigue using the value, it has been found that smaller the luminance contrast ratio of character, greater is the CFF variation rate. Furthermore, readability is poor and visual fatigue can be observed when the surface luminance is lower than the ambient luminance. However, readability can be improved by increasing the luminance contrast ratio of character to a value of 1:8.5. Thus, in low luminance environments, luminance contrast ratio of characters can affect readability and fatigue. Consider providing the full form of "CFF" so that the acronym can be used unambiguously throughout the manuscript.

• Science of Emotion and Sensibility
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• v.20 no.4
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• pp.135-142
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• 2017

In the present study, we investigated the physiological effects of smartphone use at night when the display luminance and white balance were differently manipulated. Two levels of luminance and two types of white balance were combined to form four types of displays. Subjects were instructed to use smartphones between 23:00 to 01:00 twice a week for two weeks, and for each trial, subjects were given one of the four display types. Melatonin concentration in the saliva, body temperature and heart rate were measured before and after each experiment. The experimental result showed that the low luminance display supported melatonin secretion and thermoregulation compared to the high luminance display. With regard to the white balance, higher melatonin level was observed when using the display that filtered blue light. The low luminance display together with yellowish tint best supported restful sleep at night in terms of every physiological response. This study collectively demonstrates that bright and blue light emitted from smartphone displays adversely affect melatonin secretion, body temperature, and heart rate, and therefore, suggests the use of a display with low luminance or a display that filters blue light for a restful sleep at night.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 2003.09a
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• pp.567-570
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• 2003

A color restoration algorithm for dynamic images under multiple luminance conditions is proposed by using correction vectors, defined for sub regions that the original target is divided into and calculated from color information given in well-illuminated regions. These vectors restore chromatic information of the restored image obtained by the color restoration algorithm in a low luminance condition. Under the condition that the size of dynamic color images in multiple luminance conditions is $320\times240$, experimental results show that the restored image by the proposed algorithm decreases the color-difference about 30％ than that of the restoration algorithm with color change vectors in a low luminance condition. The proposed algorithm aims to construct the surveillance system with a low cost CCD camera in the real world.

• Transactions on Electrical and Electronic Materials
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• v.3 no.1
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• pp.38-41
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• 2002

We have investigated current-voltage-luminance characteristics of organic light-emitting diodes based on TPD/Alq$_3$organics depending on the application of forward-backward bias voltage. Luminance-voltage characteristics and luminous efficiency were measured at the same time when the current-voltage characteristics were measured. We have observed that the current-voltage characteristics shows a reversible current maxima at low voltage, which is possibly not related to the emission from Alq$_3$. Current-voltage-luminance characteristics imply that the conduction luminance mechanism at low voltage is different from that of high voltage one.

• 한국정보디스플레이학회:학술대회논문집
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• 2009.10a
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• pp.991-994
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• 2009

This paper reports of camera detection of Mura. The type, location, size, orientation and amplitude are found. As the luminance variation in Mura is down to less than app. 0.3 %, measurement apparatus, techniques and algorithms are developed to measure low noise data and to extract the Mura from data with the residual noise in the same magnitude as the Mura.

• JSTS:Journal of Semiconductor Technology and Science
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• v.15 no.1
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• pp.60-67
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• 2015

This paper proposes an image-dependent color image enhancement method that uses adaptive luminance enhancement and color emphasis. It effectively enhances details of low-light regions while maintaining well-balanced luminance and color information. To compare the structure similarity and naturalness, we used the tone mapped image quality index (TMQI). The proposed method maintained better structure similarity in the enhanced image than did the space-variant luminance map (SVLM) method or the adaptive and integrated neighborhood dependent approach for nonlinear enhancement (AINDANE). The proposed method required the smallest computation time among the three algorithms. The proposed method can be easily implemented using the field-programmable gate array (FPGA), with low hardware resources and with better performance in terms of similarity.

• Journal of the Optical Society of Korea
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• v.14 no.2
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• pp.152-162
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• 2010

This study examined the effects of surround luminance on the shape of the spatial luminance contrast sensitivity function (CSF). The reduction in brightness of uniform neutral patches shown on a computer controlled display screen is also assessed to explain the change of CSF shape. Consequently, a large amount of reduction in contrast sensitivity at middle spatial frequencies can be observed; however, the reduction is relatively small for low spatial frequencies. In general, the effect of surround luminance on the CSF appears similar to that of mean luminance. Reduced CSF responses result in less power of the filtered image; therefore, the stimulus should appear dimmer with a higher surround luminance.

• 한국정보디스플레이학회:학술대회논문집
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• 2004.08a
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• pp.860-865
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• 2004

Field emission display(FED) using carbon nanotubes (CNT) as field emitters is expected to large-area panels with high luminance and low power consumption. In order to perform the uniform luminance with low driving voltage, we introduced a new electrode to apply higher electric potential over the CNT cathode in 2003.[1] In the study, we described the luminance uniformity of the panel and the improvement of emission uniformity by increasing the emission-site density. The luminance uniformity of the several ideal dots which were selected over the display area in the panel was 2.8%. [2] The CNT cathode was irradiated by excimer-laser, which was effective to improve emission uniformity and lower driving voltage. A prototype of CNT-FED character display was performed for middle size message displays. The prototype panel had 48 x 480-dots and the resolution was 1-mm. The panel realized high luminance at low power consumption. It will be important characteristics for legible and ubiquitous displays. [3]

• Journal of Korean Ophthalmic Optics Society
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• v.4 no.1
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• pp.63-68
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• 1999

It was made of a chart by new method to be measured the contrast sensitivity for a spatial frequency, and the mean luminance of a lattice frequency was made to three forms of 25, 50, 75% and let it to be ready a CS value from 0 to $10^3$. As a result of measuring of the CS value for a spatial frequency on a target of 12 year old students, CS value decreased of according to down the average luminance value and also the peak position shift to low spatial frequency. The low visioned person decreased the CS value in side of high frequency or in space of total frequency. By the lattice adaptation, a measured CS value was decreased in circumstance regions of adapted space frequency.

• 한국정보디스플레이학회:학술대회논문집
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• 2008.10a
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• pp.461-464
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• 2008

We have developed low voltage driving red phosphorescent organic light-emitting devices using a new electron transport layer. $Ir(piq)_3$ and CBP were used as a phosphorescent dopant and an emission host, respectively. The device exhibits a luminance of $1000\;cd/m^2$ at a voltage of 2.8 V. This high luminance at low voltage results from a high electron conduction behavior of the new electron transport layer.