Display Luminance Research Articles

Optimizing Bipolar Reset Waveform to Improve Grayscale Stability in Active Matrix Electrowetting Displays.

The electrowetting display (EWD) device is a new type of electrowetting-on-dielectric (EWOD) equipment that can achieve a paper-like display effect under the control of an electric field. In this microfluidic system, the stability of grayscale can be affected by various factors, such as the physicochemical properties of the materials, the device structure, and electric field distribution. To improve the grayscale stability of active matrix electrowetting displays (AM-EWDs), the impact of different polarities of driving voltage on oil backflow was investigated in this study. Based on the driving principles of AM-EWD, an optimized inter-frame bipolar reset driving waveform was designed to overcome oil backflow. The proposed driving waveform maintained the stability of the oil state by periodically and rapidly releasing trapped charges in the dielectric layer through a reverse driving voltage. Additionally, the effect of feed-through voltage on pixel driving voltage was eliminated by compensating for the driving voltage on a common electrode. Finally, the performance of the designed driving waveform was evaluated with a 6-inch AM-EWD driving platform. Compared to the conventional unipolar reset driving waveform, the backflow speed decreased by 2.70 a.u./s. The standard deviation of the display luminance was also reduced by 11.24 a.u. Experimental results indicated that both the oil backflow speed and the fluctuation range of luminance were effectively suppressed by the proposed driving waveform.

(Invited) Blue Organic Light-Emitting Diode Using Dynamic Exciton for Low Driving Voltage

Among the three primary colors, blue emission in organic light-emitting diodes (OLEDs) are highly important but very difficult to develop. OLEDs have already been commercialized; however, blue OLEDs have the problem of requiring a high applied voltage due to the high-energy of blue emission. Herein, an ultralow voltage turn-on at 1.47 V for blue emission with a peak wavelength at 462 nm (2.68 eV) is demonstrated in an OLED device. This OLED reaches 100 cd/m2, which is equivalent to the luminance of a typical commercial display, at 1.97 V. Blue emission from the OLED is achieved by the selective excitation of the low-energy triplet states at a low applied voltage by using the charge transfer (CT) state as a precursor and the triplet-triplet annihilation, which forms one emissive singlet from two triplet excitons. We found that the essential component for efficient blue emission is a smaller energy difference between the CT state and triplet exciton, accelerating the energy transfer between the two states and achieving the optimal performance by avoiding direct decay from the CT state to the ground state. Our study demonstrates that the developed OLED allows for a much longer operation lifetime than that from a typical blue phosphorescent OLED because the blue emission originates from a stable low-energy triplet exciton that avoids degrading the constituent materials.

P‐70: A Novel Peak Luminance Correction Method Based on Global IR Drop Compensation System on AMOLED

In the past year, AMOLED have been widely used in smartphones, laptops, and vehicles. Local excitation luminance is one of the important parameters to measure AMOLED quality. This feature is of great significance for realization of HDR video and getting better visual experience in sunlight environment. Due to IR drop effect in the local display, the performance of peak luminance is often skewed by luminance, chrominance, and gamma curves. The solution is adding a set of Gamma curve debugging at peak luminance of local display, which results in longer take time (TT) and greater aging pressure at high luminance. In this paper, we propose a novel peak luminance correction method based on Global IR (GIR) voltage drop compensation system. In the compensation system, GIR compensation Look‐Up Tables (LUT) is used to accurately tune the luminance, chrominance, and gamma curves that correspond to the local excitation luminance.

P‐122: Dependence of Aerial image quality on Display parameters in aerial Display system

In this paper, we report the relationship between the imaging spatial resolution and display parameters of the AIRR (aerial imaging by retro‐reflection) system, which we constructed using displays of different brightness, luminance spatial distribution and pixel pitch, respectively, and a line‐pair MTF‐based measurement method is applied to the system. The MTF measurement results show that the spatial resolution depends on the display pixel period size, luminance intensity and luminance spatial distribution.

65‐5: Light Control Polarizer for Automotive as an Alternative to Light Control Films

We have developed a new polarizer system named “Light Control Polarizer (LCP)” that has a shading effect comparable to that of light control films (LCF) while significantly improving on‐axis luminance loss. The LCP exhibits a louver effect of 1.4% at a 60° polar angle and 1.1% at a ‐60° polar angle in vertical direction, with a 20% increase in on‐axis luminance over LCF and a 12% increase in contrast ratio (CR). These characteristics allow the LCP to work as an alternative to LCF providing with effective light shielding in the vertical direction without sacrificing display luminance.

Adaptive display white point under various ambient conditions

AbstractDisplay technologies have been developed to adjust the display brightness and color under different viewing conditions, providing better viewing experiences to users. Solutions have been proposed to adjust the display white point according to the ambient light condition, which roots into the underlying chromatic adaptation mechanism in the human visual system. This study was carefully designed to reveal the necessity to consider the ambient light level and display luminance together, which affects the viewing mode, when adjusting the adaptive display white point. The results clearly suggested that when the display luminance was greater than the ambient light diffuse white luminance, the display was viewed in the self‐luminous mode and the display white point was not significantly affected by the ambient light chromaticities. In contrast, when the display luminance was lower than the ambient light diffuse white luminance, the display was viewed in the surface mode and the ambient light chromaticities had a significant effect on the display white point, especially when the surround ratio was high.

Optimum display luminance and contrast polarity of desktop head-up display under office lighting level based on visual ergonomic study

New type desktop head-up display (HUD) can reduce visual fatigue and protect vision through long viewing distance. In this study, participants evaluated visual performance, fatigue, and discomfort of desktop HUD under two contrast polarity (N = 36) and five display luminance levels (N = 21). A positive polarity advantage was found over negative in visual fatigue and discomfort (p < .05). Statistically significant effect of luminance was found on visual performance, fatigue, and discomfort (p < .05). The calculated optimum display luminance by the proposed inverted-U fitted model was 153 cd/m2 under 300 lx, higher than that of traditional desktop displays. It is speculated that higher luminance is required to offset the reduction in contrast sensitivity due to smaller target angular size, which caused by longer viewing distance. These findings suggest that positive polarity and 153 cd/m2 can be used to improve performance and avoid fatigue and discomfort when utilising desktop HUD under 300 lx.

Pathologists light level preferences using the microscope—study to guide digital pathology display use

BackgroundCurrently, there is a paucity of guidelines relating to displays used for digital pathology making procurement decisions, and optimal display configuration, challenging.Experience suggests pathologists have personal preferences for brightness when using a conventional microscope which we hypothesized could be used as a predictor for display setup. MethodsWe conducted an online survey across six NHS hospitals, totalling 108 practicing pathologists, to capture brightness adjustment habits on both microscopes and displays.A convenience subsample of respondents was then invited to take part in a practical task to determine microscope brightness and display luminance preferences, in the normal working environment. A novel adaptation for a lightmeter was developed to directly measure the light output from the microscope eyepiece. ResultsThe survey (response rate 59% n=64) indicates 81% of respondents adjust the brightness on their microscope. In comparison, only 11% report adjusting their digital display. Display adjustments were more likely to be for visual comfort and ambient light compensation rather than for tissue factors, common for microscope adjustments. Part of this discrepancy relates to lack of knowledge of how to adjust displays and lack of guidance on whether this is safe; But, 66% felt that the ability to adjust the light on the display was important.Twenty consultants took part in the practical brightness assessment. Light preferences on the microscope showed no correlation with display preferences, except where a pathologist has a markedly brighter microscope light preference. All of the preferences in this cohort were for a display luminance of <500 cd/m2, with 90% preferring 350 cd/m2 or less. There was no correlation between these preferences and the ambient lighting in the room. ConclusionsWe conclude that microscope preferences can only be used to predict display luminance requirements where the microscope is being used at very high brightness levels. A display capable of a brightness of 500 cd/m2 should be suitable for almost all pathologists with 300 cd/m2 suitable for the majority. Although display luminance is not frequently changed by users, the ability to do so was felt to be important by the majority of respondents.Further work needs to be undertaken to establish the relationship between diagnostic performance, luminance preferences, and ambient lighting levels.

5‐1: Adaptive Luminance Display Technology based on Neural Network

5‐1: Adaptive Luminance Display Technology based on Neural Network

Pulse-width modulation as a new hygienic factor determining the visual comfort of modern screens

The information revolution and intensive development of electronic devices take place in the recent decades. Furthermore, not so long ago such a hygienic factor, as the display luminance pulse-width modulation (PWM) capable of causing visual discomfort (PWM symptoms) in individuals with increased sensitivity to visual load, has become relevant. The main complaints include eye pain, headache, sometimes nausea, up to the inability to use such screens. Moreover, this characteristic can be peculiar not only to LED (AMOLED, etc.), but also to IPS displays due to the presence of the LED backlight layer. No regulation of the issue has led to the emergence of online resources on PWM and the problem of visual impairment, where users verify the data on their own, which suggests the relevance of the subject selected. The paper reports theoretical aspects of PWM, technical characteristics of displays with PWM; the approaches to PWM measurement are described; the possible ways to reduce visual discomfort are discussed. Furthermore, the paper describes the method to measure PWM of displays using a photo camera with the exposure time set to 1/20 s, along with the method testing results. It has been shown that further research focused on assessing the effects of PWM on vision and the development of the method for hygienic assessment of monitors and smartphone screens with PWM are required.

Rational molecular design of efficient yellow-red dendrimer TADF for solution-processed OLEDs: a combined effect of substitution position and strength of the donors

AbstractThe development of high-performance solution-processed red organic light-emitting diodes (OLEDs) remains a challenge, particularly in terms of maintaining efficiency at high luminance. Here, we designed and synthesized four novel orange-red thermally activated delayed fluorescence (TADF) dendrimers that are solution-processable: 2GCzBP, 2DPACzBP, 2FBP2GCz and 2FBP2DPACz. We systematically investigated the effect of substitution position and strength of donors on the optoelectronic properties. The reverse intersystem crossing rate constant (kRISC) of the emitters having donors substituted at positions 11 and 12 of the dibenzo[a,c]phenazine (BP) is more than 10-times faster than that of compounds substituted having donors substituted at positions 3 and 6. Compound 2DPACzBP, containing stronger donors than 2GCzBP, exhibits a red-shifted emission and smaller singlet-triplet energy splitting, ΔEST, of 0.01 eV. The solution-processed OLED with 10 wt% 2DPACzBP doped in mCP emitted at 640 nm and showed a maximum external quantum efficiency (EQEmax) of 7.8%, which was effectively maintained out to a luminance of 1,000 cd m−2. Such a device∙s performance at relevant display luminance is among the highest for solution-processed red TADF OLEDs. The efficiency of the devices was improved significantly by using 4CzIPN as an assistant dopant in a hyperfluorescence (HF) configuration, where the 2DPACzBP HF device shows an EQEmax of 20.0% at λEL of 605 nm and remains high at 11.8% at a luminance of 1,000 cd m−2, which makes this device one of the highest efficiency orange-to-red HF SP-OLEDs to date.

Comparison of four different displays for identification of select pathologic features extracted from whole slide images of surgical pathology cases

BackgroundThe establishment of minimum standards for display selection for the whole slide image (WSI) interpretation has not been fully defined. Recently, pathologists have increasingly preferred using remote displays for clinical diagnostics. Our study aims to assess and compare the performance of three fixed work displays and one remote personal display in accurately identifying ten selected pathologic features integrated into WSIs. DesignHematoxylin and eosin-stained glass slides were digitized using Philips scanners. Seven practicing pathologists and three residents reviewed ninety WSIs to identify ten pathologic features using the LG, Dell, and Samsung and an optional consumer-grade display. Ten pathologic features included eosinophils, neutrophils, plasma cells, granulomas, necrosis, mucin, hemosiderin, crystals, nucleoli, and mitoses. ResultsThe accuracy of the identification of ten features on different types of displays did not significantly differ among the three types of “fixed” workplace displays. The highest accuracy was observed for the identification of neutrophils, eosinophils, plasma cells, granuloma, and mucin. On the other hand, a lower accuracy was observed for the identification of crystals, mitoses, necrosis, hemosiderin, and nucleoli. Participant pathologists and residents preferred the use of larger displays (>30″) with a higher pixel count, resolution, and luminance. ConclusionMost features can be identified using any display. However, certain features posed more challenges across the three fixed display types. Furthermore, the use of a remote personal consumer-grade display chosen according to the pathologists’ preference showed similar feature identification accuracy. Several factors of display characteristics seemed to influence pathologists’ display preferences such as the display size, color, contrast ratio, pixel count, and luminance calibration. This study supports the use of standard “unlocked” vendor-agnostic displays for clinical digital pathology workflow rather than purchasing “locked” and more expensive displays that are part of a digital pathology system.

Blue organic light-emitting diode with a turn-on voltage of 1.47 V

Among the three primary colors, blue emission in organic light-emitting diodes (OLEDs) are highly important but very difficult to develop. OLEDs have already been commercialized; however, blue OLEDs have the problem of requiring a high applied voltage due to the high-energy of blue emission. Herein, an ultralow voltage turn-on at 1.47 V for blue emission with a peak wavelength at 462 nm (2.68 eV) is demonstrated in an OLED device with a typical blue-fluorescent emitter that is widely utilized in a commercial display. This OLED reaches 100 cd/m2, which is equivalent to the luminance of a typical commercial display, at 1.97 V. Blue emission from the OLED is achieved by the selective excitation of the low-energy triplet states at a low applied voltage by using the charge transfer (CT) state as a precursor and triplet-triplet annihilation, which forms one emissive singlet from two triplet excitons.

P‐21: Novel Circuit Driving Solutions for Eliminating TFT‐LCD Image Stick Flicker Issue

This paper proposed new effective solutions to solve TFT‐LCD image stick flicker issue when panel received noisy input signal. To eliminate image stick flicker issue, source data polarity inversion mode has been changed. To improve display blinking issue caused from polarity inversion mode change, source data polarity inversion has further optimized and some frame's display luminance has reduced. Compared with normal method, new solutions can solve image stick flicker issue and don't affect display quality.

71‐3: Effects of Circadian Rhythm, Ambient Illuminance and Display Content on Comfortable Display Luminance

The influences of ambient illuminance, display content and circadian rhythm on the perceived brightness were studied through a psychophysical experiment and the comfort zone of display luminance was investigated. The results showed that illuminance and display content, rather than circadian rhythm affected judgment of comfortable display luminance.

79‐1: Display white change by the surround ratio

The perceived display of white was investigated at three levels of surround ratio: 0.12, 0.24, and 0.36. These ratios were generated using a combination of four levels of adapting luminance and four levels of display luminance. The results showed that the surround ratio has a greater influence on the perceived display of white than the adapting luminance, which has been used as a parameter in the degree of adaptation factor for chromatic adaptation transform models.

Comfortable brightness of watching television in the dark

ABSTRACT This study exploits an optimal display brightness for watching television in the dark. Two experiments were carried out in a dark room, and static and moving images were tested in each experiment. In Experiment I, three different, full-screen color images were presented with brightness levels ranging from 20 to 400 nit. A total of 23 college students assessed each stimulus' degree of visual comfort. Experiment II was conducted with 31 participants, and six videos with a range of brightness from 20 to 500 nit were shown. As a result, when watching the static image, the participants' assessments were almost the same among stimuli. However, when watching a video, the characteristics of the stimuli made the evaluation vary. This study provides empirical evidence and estimations of visual comfort based on display luminance that should be considered when designing for more comfortable viewing in a dark environment.

P‐12.7: Front Light Guide Plates for Reflective LCDs

Reflective liquid crystal display has the advantages of energy saving and environmental protection. When the ambient light is low, the front light source is required to provide illumination rays. The front light guide plate has a great influence on display luminance, contrast, etc. Based on Comprehensive considerations on luminance, uniformity, stray light, an analysis and evaluation method for front light guide source is proposed. Taking spherical dots as an example, the influence of dot radius and height on the comprehensive performance of the front light source is analyzed. The simulation results show that when the R:H is 3:1, the comprehensive evaluation parameters of the spherical structure are high, and the signal‐to‐noise ratio is increased by 240%, which can greatly improve the display performance. The analysis and evaluation method proposed in this paper can effectively guide the development of front light guide plates, shorten the development time and reduce the development cost.

44.4: Effects of Circadian Rhythm, Ambient Illuminance and Display Content on Comfortable Display Luminance

The influences of ambient illuminance, display content and circadian rhythm on the perceived brightness were studied through a psychophysical experiment and the comfort zone of display luminance was investigated. The results showed that illuminance and display content, rather than circadian rhythm affected judgment of comfortable display luminance.

PsyCalibrator: An Open-Source Package for Display Gamma Calibration and Luminance and Color Measurement

Studies in vision, psychology, and neuroscience often present visual stimuli on digital screens. Crucially, the appearance of visual stimuli depends on properties such as luminance and color, making it critical to measure them. Yet conventional luminance-measuring equipment is not only expensive but also onerous to operate (particularly for novices). Building on previous work, here we present an open-source integrated software package—PsyCalibrator ( https://github.com/yangzhangpsy/PsyCalibrator )—that takes advantage of consumer hardware (SpyderX, Spyder5) and makes luminance/color measurement and gamma calibration accessible and flexible. Gamma calibration based on visual methods (without photometers) is also implemented. PsyCalibrator requires MATLAB (or its free alternative, GNU Octave) and works in Windows, macOS, and Linux. We first validated measurements from SpyderX and Spyder5 by comparing them with professional, high-cost photometers (ColorCAL MKII Colorimeter and Photo Research PR-670 SpectraScan). Validation results show (a) excellent accuracy in linear correction and luminance/color measurement and (b) for practical purposes, low measurement variances. We offer a detailed tutorial on using PsyCalibrator to measure luminance/color and calibrate displays. Finally, we recommend reporting templates to describe simple (e.g., computer-generated shapes) and complex (e.g., naturalistic images and videos) visual stimuli.