Brightness Of Light Research Articles

Assessment of ecosystem service flow and optimization of spatial pattern of supply and demand matching in Pearl River Delta, China

Exploring the spatial flow pattern of ecosystem services and clarifying the transmission path between the supply area and the demand area will help to formulate more scientific and reasonable ecological protection policies. This paper takes the rapid urbanization area representing the Pearl River Delta urban agglomeration as an example. Using Invest model to quantitative the assessment of the supply and demand of carbon sequestration services and water ecosystem services from 2000 to 2020, a spatial flow model of ecosystem services is constructed to clarify the spatial flow of regional ecosystem services pattern. In addition, the Geo-detector model is used to explore the driving factors of the supply and demand relationship of ecosystem services, and the spatiotemporal geographic weighted regression model is further used to analyze the temporal and spatial differentiation of the impact degree. Finally, based on the Bayesian belief network, the optimal state factor configuration is selected to optimize the spatial pattern, and the corresponding optimization strategy is given. The main conclusions are as follows: (1) The supply of carbon sequestration services in the Pearl River Delta decreased gradually during 2000–2020, while the demand increased gradually. The supply of water ecosystem services increased first and then decreased, while the demand showed a downward trend. (2) In terms of spatial heterogeneity of supply and demand matching, the main driving factors of carbon sequestration services included night light brightness value, temperature and vegetation index; The main driving factors of water ecosystem services include night light brightness value, land use type and vegetation index. (3) In terms of optimal areas for supply and demand matching, carbon sequestration services were mainly distributed in Zhaoqing, Huizhou and Jiangmen; The optimal matching areas of water ecosystem service supply and demand were mainly distributed in Zhaoqing, Guangzhou, Huizhou and other cities.

A method of laser stripe centerline extraction based on deep learning for structured light 3D reconstruction

To overcome the stray light noise in the centerline extraction method during line structured light 3D reconstruction process, an end-to-end trainable neural network for laser stripe centerline extraction based on Convolutional Neural Network and Multi-Layer Perception is proposed. The proposed network can self-adapt to a variety of lighting (brightness) conditions and overcome the interference of different stray lights. In addition, unlike prior work on enhancing the accuracy of centerline extraction using deep learning methods that only performs it for noise reduction in pre-processing, the proposed network unifies the noise reduction and prediction processes, so that it can be optimized end-to-end directly on centerline extraction performance. The network learns an intermediate feature representation of noise reduction, which requires less complexity for data annotation, reduces the training difficulty, and has more scalability. Experiments show that the proposed method can perform centerline extraction with relatively high accuracy for laser stripes of different widths, brightness, and inclination, thus obtaining a smooth and stable reconstructed surface in the structured light 3D reconstruction process.

A Spatiotemporally Constrained Interpolation Method for Missing Pixel Values in the Suomi-NPP VIIRS Monthly Composite Images: Taking Shanghai as an Example

The Visible Infrared Imaging Radiometer Suite Day/Night Band (VIIRS/DNB) nighttime light data is a powerful remote sensing data source. However, due to stray light pollution, there is a lack of VIIRS data in mid-high latitudes during the summer, resulting in the absence of high-precision spatiotemporal continuous datasets. In this paper, we first select nine-time series interpolation methods to interpolate the missing images. Second, we construct image pixel-level temporal continuity constraints and spatial correlation constraints and remove the pixels that do not meet the constraints, and the eliminated pixels are filled with the focal statistics tool. Finally, the accuracy of the time series interpolation method and the spatiotemporally constrained interpolation method (STCIM) proposed in this paper are evaluated from three aspects: the number of abnormal pixels (NP), the total light brightness value (TDN), and the absolute value of the difference (ADN). The results show that the images simulated by the STCIM are more accurate than the nine selected time series interpolation methods, and the image interpolation accuracy is significantly improved. Relevant research results have improved the quality of the VIIRS dataset, promoted the application research based on the VIIRS DNB long-time series night light remote sensing image, and enriched the night light remote sensing theory and method system.

Drowsy Detection in the Eye Area using the Convolutional Neural Network

Detection of a drowsy driver is an important aspect of driving safety. For this reason, it is necessary to have technology to carry out early detection before fatigue occurs. Mainly focused on driver fatigue that occurs at night. Analysis can be done quickly and accurately. These conditions can be sent via data so that they can be monitored and analyzed in real time. The results of the analysis can be sent by communication via the internet network. In addition, it functions as an early warning and can be used as logging or records that can be stored. This research does not discuss data communication but makes a prototype for detecting sleepy drivers. Prototype created using the Convolutional Neural Network Algorithm. The detection area is in the eye and testing is carried out with the brightness level of the light. In this study, building a prototype to detect signs of driver fatigue using the Convolutional Neural Network algorithm. The detection area used is in the eye, by testing at different light brightness levels. The dataset used in this study consists of a series of eye images, which are divided into two classes, namely open eyes, and closed eyes. After conducting the training process on Convolutional Neural Network, we get results of detection accuracy reaching 90%.

The improvement of the color rendering index using convex-dual-layer remote phosphor geometry with YOCl:Eu3+

White-light emitting diodes (WLEDs) are semiconductor light sources whose construction design is usually made up of a single pumping chip and a single light-conversion film of phosphor compound. The outstanding problem of this traditional setting is the inadequate chroma rendering index (CRI). Introducing a cluster of multiple blue chips with more than one phosphor layer is demonstrated to address that flaw of W-LEDs. This package is called the dual-film remote-phosphor multi-chip WLED. As a consequence, both the light brightness and the CRI are improved. However, for the maximum results, the test on the second layer of phosphor has been performed to continually alter the proportions and densities of phosphor within the silicone. The researchers employed a unique hue design to control the white-light light emitting diode (LED) module. When comparing the actual result to the simulated color coordinates under the hue standard of international commission on illumination (CIE) 1931, the highest difference is found to be around 0.0063 for correlated color temperatures (CCT) of 6600 K and 7700 K. Experiments indicate that the setting of multi-chip and dual-phosphorus is the optimal design for supporting CRI quality and luminous intensity.

Surgical Assistant-friendly Breast Reconstruction Using a Head-mounted Wireless Camera with an Integrated LED Light as an Educational Tool

In breast reconstruction by a latissimus dorsi (LD) flap, a skin paddle is designed transversely so that the scar overlaps the bra line. Therefore, especially when dissecting the caudal end of the latissimus dorsi muscle, the assistants must always pull hooks blindly because they do it from the patient’s caudal side (Fig. 1). A similar situation occurs when a tissue expander or a silicone breast implant is inserted under the pectoralis major muscle through a lateral thoracic incision because it is done from the contralateral side. These situations make it difficult for the surgeon to simultaneously share the surgical field with the assistants. As a result, the assistants just pull hooks to expand the surgical field without being motivated to understand the details of the surgery. To resolve this, breast reconstruction was performed for six Japanese women, with the surgeon wearing a head-mounted wireless camera with an integrated LED light, FM-105 (Faspro Systems Co., Ltd., Taipei, Taiwan) (Fig. 1); two were reconstructed by LD, three by tissue expander, and one by silicone breast implant. The camera cost approximately $3650, and there were no other costs because we already had a laptop computer and an HDMI cable. The surgical field was projected to external large screen monitors in the operating room, as previously reported.1 The camera actually weighed about 315 g, and it could be used without any physical discomfort for 2 hours, which is enough time to complete elevating the LD or inserting the implant. In addition, the focus was automatically adjusted, and the brightness of the LED light could be manually adjusted in three steps, according to the darkness of the surgical field. Although the camera does not have a zoom function, the image is easily visible by projecting it onto a large screen. The surgical view could be shared simultaneously with the assistants and observers via the monitor in all cases, and the image is shown. (See Video [online], which displays a scene of dissecting the caudal side of the LD muscle and the results of a questionnaire survey following a scene of dissecting the caudal side of the LD muscle.) A questionnaire survey using a five-point scale (1 = unacceptable; 5 = excellent) was conducted among six assistants who participated in the surgery to assess the quality of the actual image and the educational usefulness of the head-mounted camera. All of them answered that it was a useful educational tool for breast reconstruction.Fig. 1.: The LD flap is elevated while the surgeon wears a head-mounted wireless camera with an integrated LED light, FM-105. The surgical assistant can assist from the caudal side while watching the surgical field via the screen in real time during the operation. {"href":"Single Video Player","role":"media-player-id","content-type":"play-in-place","position":"float","orientation":"portrait","label":"Video 1","caption":"displays a scene of dissecting the caudal side of the LD muscle and the results of a questionnaire survey following a scene of dissecting the caudal side of the LD muscle.","object-id":[{"pub-id-type":"doi","id":""},{"pub-id-type":"other","content-type":"media-stream-id","id":"1_lkskropp"},{"pub-id-type":"other","content-type":"media-source","id":"Kaltura"}]} Recently, how to teach surgical techniques to junior doctors is becoming a focus of attention in plastic and reconstructive surgery. The use of AR technology2,3 and model surgery4 has resulted in remarkable progress, and these technologies have contributed greatly to providing images of the details of the operation for young surgeons before surgery. During the operation, by teaching techniques while sharing the operative field that the surgical assistant cannot see directly, they can be involved in surgery as not only workers, but also as trainees or learners. DISCLOSURE The authors have no financial interest to declare in relation to the content of this article.

P‐2.30: Design and Fabrication of an Optical Path Folding Pancake Virtual Reality Head‐mounted Display

Metaverse has been going viral across the globe, and virtual reality head‐mounted displays (VR‐HMDs) as the basic infrastructure and entrance to cater to this evolution of social interaction are showing rapid development recently. Pancake optics based on optical path folding provides the feasibility of VR‐HMDs in the form of glasses and is wide recognition. The pancake system has become the current mainstream owing to its large exit pupil diameter (EPD), high resolution, novel compact, and lightweight. Owing to the use of polarization elements, the birefringence in the lens will change the polarization state of the light, resulting in uneven brightness and stray light, seriously reducing the optical performance of the system, so it is necessary to control the birefringence of the lens. In this study, we proposed a pancake system based on a 2.1‐inch LCD display which achieves 10 mm EPD at 11 mm, diagonal field of view (FOV) of 96°, overall length (OAL) of the system less than 20 mm, and support diopter adjustment from ‐7D to ‐1D. The residual birefringence of the lens can be effectively suppressed in four stages: 1) controlling the thickness ratio between the center and the edge of the lens during the optical design, 2) setting a reasonable position and size of the injection gate and cooling system during the mold design process, 3) adopting reasonable injection parameters during the precision injection molding process and 4) eliminating the birefringence of the lens with the lens annealing process. Ultra‐precision machining and correction of the mold cores have been employed to achieve high surface accuracy and low birefringence of the lens. The optomechanical design, assembly, and adjustment process are discussed. Finally, the prototype of the pancake system is experimentally tested, and the results demonstrate pretty well.

P‐17.3: Visibility Research Based on Ambient Light Contrast

In the development process of displays, the viewer's experience is particularly important. However, in actual use, unlike the dark‐room test, there will be a certain amount of ambient light, which will affect the visibility of the display screen. As ambient illumination increases, the viewing effect of the display screen will also deteriorate. For example, it is difficult to see the screen clearly outdoors with bright sunlight, which is quite different from the viewing effect in dark room. In this article, we will study the visibility of public mode display and privacy mode display. For public mode display, both the central view angle and large view angle can see the screen clearly regardless of the ambient light brightness. For privacy mode display, no matter what the ambient light conditions are, it is invisible for the large view angle, while the center view angle can see clearly. And respectively propose two ways to improve the ambient contrast. In public mode, LCD with advanced reflective invisible technology with embedded system (ARIES) can achieve excellent visibility in various ambient light condition from indoors to outdoors without boosting the backlight brightness and sacrificing other performance for better visibility. In privacy mode, the view angle control cell (VAC) and privacy film are used to reduce the ambient light contrast of the privacy display, which fully satisfies the requirements of being invisible in the outdoor environment at a large view angle conditions, and can meet the privacy performance in some low ambient light. Author Keywords

Hole Depth Prediction in a Femtosecond Laser Drilling Process Using Deep Learning.

In high-aspect ratio laser drilling, many laser and optical parameters can be controlled, including the high-laser beam fluence and number of drilling process cycles. Measurement of the drilled hole depth is occasionally difficult or time consuming, especially during machining processes. This study aimed to estimate the drilled hole depth in high-aspect ratio laser drilling by using captured two-dimensional (2D) hole images. The measuring conditions included light brightness, light exposure time, and gamma value. In this study, a method for predicting the depth of a machined hole by using a deep learning methodology was devised. Adjusting the laser power and the number of processing cycles for blind hole generation and image analysis yielded optimal conditions. Furthermore, to forecast the form of the machined hole, we identified the best circumstances based on changes in the exposure duration and gamma value of the microscope, which is a 2D image measurement instrument. After extracting the data frame by detecting the contrast data of the hole by using an interferometer, the hole depth was predicted using a deep neural network with a precision of within 5 μm for a hole within 100 μm.

Urban waterlogging resilience assessment and postdisaster recovery monitoring using NPP-VIIRS nighttime light data: A case study of the ‘July 20, 2021’ heavy rainstorm in Zhengzhou City, China

In recent years, with the acceleration of urbanization and abnormal changes in the overall climate, cities have been increasingly threatened and affected by disasters. Assessing and improving urban resilience, as well as postdisaster recovery monitoring, are of great significance for relevant municipal departments. Taking the heavy rainstorm event that occurred on July 20, 2021, in Zhengzhou City as an example, this study explored the resilience and postdisaster recovery of Zhengzhou City based on remote sensing data and other multisource data. First, we calculated the resilience assessment index and built an assessment model. Then, we analyzed and evaluated the resilience. Finally, based on NPP-VIIRS nighttime light data, we verified the accuracy of the resilience results and dynamically monitored the postdisaster recovery process. The results show that the overall resilience of Zhengzhou City to waterlogging disasters is low in the southwest and high in the northeast. The changing trend of the nighttime light brightness following the disaster was consistent with the resilience assessment results. Then, due to rescue work, the light index increased briefly in July; Due to the serious impact of the disaster, the facilities were damaged, and the light index was reduced in August. With the development of recovery work, the disaster-influenced and light index areas gradually recovered and exceeded the predisaster level. Corresponding urban resilience strategies were proposed based on the assessment results. This study can provide a scientific basis and reference for relevant aspects such as disaster prevention, recovery, and reconstruction in Zhengzhou City and other cities.

Development of the control system for LEGO Mindstorms EV3 mobile robot based on MATLAB/Simulink elements

The Mindstorms EV3 robot, developed by LEGO, is one of the popular robots that has been widely used in various fields. Unlike previous versions of mobile LEGO robots, EV3 allows the development of real-time applications for teaching a variety of subjects, as well as for conducting research experiments. The object of research in this case is the Mindstorms EV3 robot connected to MATLAB/Simulink. The design consists of a controller, one color sensor, two servo motors and one support wheel. Each servo motor is built on a DC collector motor with a matching gearbox and has the ability to measure the number of revolutions corresponding. A digital sensor with a sampling frequency of 1 kHz is used as a color sensor, which can determine the color or brightness of light. Despite its popularity, the EV3 robot control system in interaction with the MATLAB/Simulink programming environment is a rather complex solution and therefore requires further research. The scientific part of the research focuses on discovering the regularities of the Mindstorms EV3 control system, developing a control system model, and exploring the potential of MATLAB/Simulink to expand the robot's capabilities. An analysis of the main elements of the control system, such as sensors and servos, was carried out. The graphs of the dependences of the characteristics of the servo drives were built and the efficiency of the robot movement was checked depending on the parameters set in the program. The result of the development of the mobile robot control system was the adjustment of the mobile robot movement regulators along a given trajectory in the form of a drawn line, which allowed estimating the maximum permissible speed of the robot movement. The presented research and development of a control system based on MATLAB/Simulink elements allows using the proposed method to control a mobile robot with high precision, analyze and verify the robot's electromechanical parameters in real time. This control system has a high potential and can practically be integrated into industrial objects of mobile robotics, provided types the sensors and executive mechanisms of the mobile robot match.

Potential of Using Night-Time Light to Proxy Social Indicators for Sustainable Development

Satellite-observed night-time light (NTL) data provide a measure of the lighting brightness seen from space at different times and spatial and temporal resolutions, thus offering opportunities to explore them in many applications at different spatial locations (global, regional, local). However, most applications to date have been at relatively large spatial scales, despite the need to measure indicators at a local level. This paper sets out an analysis of the potential of NTL data for populating indicators at more local (neighbourhood, street) scales. We first reviewed the overall potential of NTL data for social indicators at different spatial scales by using a systematic search of the literature and applying the Maturity Matrix Framework (MMF). We also explored a case study (Durango State, Mexico) using Visible Infrared Imaging Radiometer Suite (VIIRS) imageries, other geospatial data, and the social gap index (SGI) to identify social gaps at the local scale. The literature review showed that NTL can play a role in supporting 49 out of 192 sustainable development goal (SDG) indicators having a focus on social issues, but most of these have been explored at the global or country scales. In the case study, we found that low radiance is indeed associated with higher SGI levels (i.e., more social deprivation) and vice versa. However, more research is needed from other contexts to support a link between NTL radiance levels and social indicators at local scales.

무대 조명과 증강현실 자막 밝기에 따른 사이버 멀미 영향 분석

Recently, as the demand for non-face-to-face communication has soared due to COVID-19, the interest in augmented reality is increasing. In order to conveniently use augmented reality technology in our daily lives, cybersickness should be considered. The purpose of this study is to analyze the effect of stage lighting brightness and AR subtitle brightness on comfort and visibility. A total of 30 subjects conducted human factor evaluation by dividing the stage lighting brightness into 3 levels and AR subtitle brightness into 4 levels. Through two-way ANOVA, it was confirmed that there was a significant difference in both factors, and a significant difference was analyzed through a post-hoc test.

A simple but novel approach to calculate seabird light fallout: A case study from Kauaʻi

Injury and mortality of night flying seabirds due to lights (fallout) affects their long-term viability. However, the cryptic nature of these species hinders direct estimates and projections of fallout. The Kauaʻi Seabird Habitat Conservation Plan (KSHCP) characterizes the current and projected fallout for Newell's shearwaters (Puffinus auricularis newelli), Hawaiian petrels (Pterodroma sandwichensis) and the Hawaiʻi distinct population segment of the band-rumped storm-petrels (Oceanodroma castro) on the island of Kauaʻi across eight permittees. In the KSHCP, each permittee was required to itemize the lighting infrastructure related to their facilities (type, wattage, number of lights, etc.) as well as supply an overall expected seabird fallout number with an estimate of detection probability or ability to find the fallout birds. Light intensity is thought to be correlated to the degree of attraction to a light source. Here we identify seabird fallout using indirect estimates derived from the KSHCP and present a reproducible method to consistently project and calculate fallout between entities that need to reduce seabird mortality due to their light sources. Though the permittees did not provide an estimate of light intensity at their sites, we extrapolated luminous intensity (light brightness) from their itemized light information (i.e., lumens/watt). Using luminous intensity, we then derived the degree of fallout per lumen and its variation across the permittees. As a proof of concept, we then projected the fallout per lumen estimate onto streetlights owned by the Kauaʻi Island Utility Cooperative, as applied over a range of detectability correction factors. Though fallout varies significantly based on the detectability correction factor used, when considering the site differences on Kauaʻi, a previous fallout estimate, and the overlapping characteristics of the projected versus actual luminous intensities, the utilities projected fallout appears applicable. We feel that the methodology can be used as a baseline to infer fallout associated with various entities.

Sky subtraction in an era of low surface brightness astronomy

ABSTRACT The Vera C. Rubin Observatory Wide-Fast Deep sky survey will reach unprecedented surface brightness depths over tens of thousands of square degrees. Surface brightness photometry has traditionally been a challenge. Current algorithms which combine object detection with sky estimation systematically oversubtract the sky, biasing surface brightness measurements at the faint end and destroying or severely compromising low surface brightness light. While it has recently been shown that properly accounting for undetected faint galaxies and the wings of brighter objects can in principle recover a more accurate sky estimate, this has not yet been demonstrated in practice. Obtaining a consistent spatially smooth underlying sky estimate is particularly challenging in the presence of representative distributions of bright and faint objects. In this paper, we use simulations of crowded and uncrowded fields designed to mimic Hyper Suprime-Cam data to perform a series of tests on the accuracy of the recovered sky. Dependence on field density, galaxy type, and limiting flux for detection are all considered. Several photometry packages are utilized: source extractor, gnuastro, and the LSST science pipelines. Each is configured in various modes, and their performance at extreme low surface brightness analysed. We find that the combination of the source extractor software package with novel source model masking techniques consistently produce extremely faint output sky estimates, by up to an order of magnitude, as well as returning high fidelity output science catalogues.

Spatial Pattern of Changing Vegetation Dynamics and Its Driving Factors across the Yangtze River Basin in Chongqing: A Geodetector-Based Study

Revealing the spatial dynamics of vegetation change in Chongqing and their driving mechanisms is of major value to regional ecological management and conservation. Using several data sets, including the SPOT Normalized Difference Vegetation Index (NDVI), meteorological, soil, digital elevation model (DEM), human population density and others, combined with trend analysis, stability analysis, and geographic detectors, we studied the pattern of temporal and spatial variation in the NDVI and its stability across Chongqing from 2000 to 2019, and quantitatively analyzed the relative contribution of 18 drivers (natural or human variables) that could influence vegetation dynamics. Over the 20-year period, we found that Chongqing region’s NDVI had an annual average value of 0.78, and is greater than 0.7 for 93.52% of its total area. Overall, the NDVI increased at a rate of 0.05/10 year, with 81.67% of the areas undergoing significant expansion, primarily in the metropolitan areas of Chongqing’s Three Gorges Reservoir Area (TGR) and Wuling Mountain Area (WMA). The main factors influencing vegetation change were human activities, climate, and topography, for which the most influential variables respectively were night light brightness (NLB, 51.9%), annual average air temperature (TEM, 47%), and elevation (ELE, 44.4%). Furthermore, we found that interactions between differing types of factors were stronger than those arising between similar ones; of all pairwise interaction types tested, 92.9% of them were characterized by two-factor enhancement. The three most powerful interactions detected were those for NLB ∩ TEM (62.7%), NLB ∩ annual average atmospheric pressure (PRS, 62.7%), and NLB ∩ ELE (61.9%). Further, we identified the most appropriate kind or range of key elements shaping vegetation development and dynamics. Altogether, our findings can serve as a timely scientific foundation for developing a vegetative resource management strategy for the Yangtze River basin that duly takes into account local climate, terrain, and human activity.

Comparison of the restorative quality of green spaces between the evening and daytime

Research studies on the restorative quality of environments have grown rapidly; however, the majority of existing literature focuses on daytime landscapes, while the restorative quality of evening landscapes is less studied. In particular, the landscape characteristics and/or lighting features that play an essential role in improving the restorative quality of nightscapes are unknown. To address these gaps, 12 urban green spaces were selected as study sites and the same scene at each site was photographed during the day and evening. The restorative quality and 14 landscape characteristics of all photographs were evaluated quantitatively, and four lighting features of photographs taken during the evening were measured. Statistical analysis indicated that: (a) the restorative quality of daytime landscapes was significantly higher than that of evening landscapes; (b) abundant colours and natural vegetation suggested higher restorative quality during the daytime and (c) increasing the brightness of lighting and setting lighting sources in the distant view of visitors could improve the restorative quality of evening landscapes. Combined with the previous literature, the results suggest that lighting has the ability to redesign nightscapes, which consequently improves their restorative quality by concealing the less restorative features and illuminating the key elements to promote mental restoration.

An international survey on residential lighting: Analysis of summer-term results

Obtaining visual comfort, satisfaction and well-being in residential interiors are now becoming more important, especially in times of extreme events such as the COVID-19 pandemic. It also became important to collect users' evaluations and their own solutions for residential lighting in order to improve the current lighting conditions. For this aim, with a group of international and inter-disciplinary researchers, a comprehensive study was conducted. This study is the last part of a three-stage investigation aimed at increasing our knowledge of the current lighting conditions in residential areas during and after the COVID-19 pandemic. For the current study, an online survey and in-depth interviews were conducted between June and August 2022 in Poland, Turkey, Sweden, and the U.K., with 520 participants. As results of this study show, a correlation was found between daylight satisfaction and its sufficiency. Similar correlations were found between artificial lighting satisfaction, its sufficiency, and its uniformity. The differences between seasons were detected for being very satisfied with daylight quality. Also, the correlation between satisfaction with daylighting and the ratio of windows showed difference among seasons. Stronger correlations between satisfaction with artificial lighting, its sufficiency and uniformity were found in summerterm according to winter-term results. Correlations between artificial lighting brightness – CRI and uniformity weakened in summer-term. Results from open-ended questions and in-depth interviews showed, removing the shading device and augmenting the characteristics of artificial lighting were the mostly done adjustments during the COVID- 19 pandemic. The most prominent theme is visual comfort according to the in-depth interview responses.'

Strengthening Carrier Transmission to Achieve High Brightness and High Efficiency of Perovskite Quantum Dot Light Emitting Diodes

Strengthening Carrier Transmission to Achieve High Brightness and High Efficiency of Perovskite Quantum Dot Light Emitting Diodes

A super-high brightness and excellent colour quality laser-driven white light source enables miniaturized endoscopy.

A laser-driven white light source promises intrinsic advantages for miniaturized endoscopic illumination. However, it remains a great challenge to simultaneously achieve high brightness and excellent colour rendition due to the shortage of highly efficient and thermally robust red-emitting laser phosphor converters. Here, we designed CaAlSiN3:Eu@Al (CASN@Al) converters with neglectable efficiency loss by tightly bonding all-inorganic phosphor films on an aluminium substrate. A layer-by-layer phosphor converter (LuAG/CASN@Al), i.e., stacking a green-emitting Lu3Al5O12:Ce (LuAG) layer on CASN@Al, was constructed to enhance light conversion efficiency and reduce reabsorption loss under blue laser excitation, which thus produces an excellent white light source with a luminous efficacy of 258 lm W-1 and a colour rendering index of 91. A miniaturized endoscopy with a coupling efficiency twice that of the commercial white LEDs was demonstrated by using the laser-driven white light and showed a central illuminance as high as 52 730 lx, more vivid images and long-term reliability.