Uniform Light Research Articles

Microlens array device for laser light shaping in laser scanning smart headlights.

We present, what we believe to be, a novel microlens array (MLA) scheme for laser light shaping in laser scanning smart headlight. The laser spot has a Gaussian distribution that may reach a high peak power density in the central part, which is called hot spot. When the laser beam is applied to a phosphor plate for luminous conversion, the hot spot of Gaussian beam causes thermal quench and decreases luminous efficacy. To avoid this effect, an MLA is used, so as to achieve a uniform energy distribution. In this study, we propose a laser scanning smart headlight fabricated by a new MLA structure, with an arrangement providing both light uniformity and shaping. The novel MLA is designed by two-dimensional micro-concave lens array yielding a flat-top beam. The flexible fabrication process employs laser drilling to shape the micro-hole array on the glass substrate surface and then etch it to form MLA without requiring any mask lithography process. The full-width half maximum (FWHM) of light output distribution can be adjusted by the glass etching parameters, and the light distribution could be controlled by the arranged layout of the array. Thus, beams with FWHM divergence ranging from 5° to 34° has been fabricated and characterized. The typical pixel shape is a rectangle with two different FWHMs in two orthogonal directions, and the fabrication method achieves this goal as well. This novel design and unique maskless process of the MLAs is a promising tool for development the next generation laser scanning smart headlight.

Microfluidic paper-based device coupled with 3D printed imaging box for colorimetric detection in resource-limited settings

Rapid and effective methods for the detection of analytes such as water contaminants, food adulterants and biomolecules are essential for the protection of public health and environmental protection. Most of the currently established analytical techniques need sophisticated equipment, centralized testing facilities, costly operations, and trained personnel. Such limitations make them inaccessible to the general populace, particularly in regions with limited resources. The emergence of microfluidic devices offers a promising alternative to overcome several such constraints. This work describes a protocol for fabricating a low-cost, open-source paper-based microfluidic device using easily available tools and materials for colorimetric detection of analytes. The ease and simplicity of fabrication allow users to design customized devices. The device is coupled with an imaging box assembled from 3D printed parts to maintain uniform lighting conditions during analytical testing. The platform allows digital imaging using smartphones or cameras to instantaneously capture images of reaction zones on the device for quantitative analysis. The system is demonstrated for detecting hexavalent chromium, a toxic water contaminant. The image analysis is performed using open-source ImageJ for quantification of results. The approach demonstrated in this work can be readily adopted for a wide range of sensing applications.

Influence of luminance and luminance longitudinal uniformity of tunnel lighting on drivers' comprehensive visual performance

The present study aimed to investigate the comprehensive influence of the average luminance Lav and luminance longitudinal uniformity U1 on the diver’s visual performance under the stage of driving in the tunnel’s interior zone during the experiment. Specifically, we collected reaction time, pupil area change rate, and blink frequency from 40 participants through the indoor visual performance experiments. The present study quantitatively characterized the mechanism of the antagonism between luminance intensity and difference, and established the Lav-U1 curve which succeeds in satisfying the safety threshold of the driver's comprehensive visual performance. The results show that the driver's visual performance deteriorated continuously as the test time increases. Increasing the luminance was beneficial for accelerating the reaction speed, but also caused greater stimulation of light and dark changes. The change ratio of reaction speed and the increased amplitude of perceived luminance increased exponentially with the increase of luminance, resulting in an antagonism effect. The visual performance decreased with the increase of average luminance under low uniformity levels, and increased with the increase of average luminance under high uniformity levels. Furthermore, we found that the luminance longitudinal uniformity should match up the luminance in the interior zone, instead of separation under the current specification. Based on our findings, we propose specific recommendations for the luminance longitudinal uniformity under different average luminance levels. For the interior zone of tunnels with an average luminance of 2.5, 4.5, and 6 cd/m2, the luminance longitudinal uniformity should be increased from 0.6 to 0.67, 0.72, and 0.75, respectively. Current findings demonstrate that the implementation of the proposed U1 standard in tunnel lighting design can significantly fasten drivers' reaction time, contribute to a decrease in traffic accidents, and thus improve the safety level of tunnel lighting design in the interior zone of tunnel. These results have significant implications for the design of tunnel lighting.

WITHDRAWN: Using spatial modeling to evaluate LED light intensity and uniformity in commercial broiler houses during brooding and tunnel conditions

WITHDRAWN: Using spatial modeling to evaluate LED light intensity and uniformity in commercial broiler houses during brooding and tunnel conditions

A tunnel coaxial 3D hyperspectral scanning system for underground mine investigation

A hyperspectral scanning system was developed for three-dimensional (3D) surface mapping in underground spaces, such as mine shafts and tunnels. A hyperspectral line-scanning camera was mounted on the rotating driver unit coaxial with the tunnel to image both the mine wall and the ceiling. Uniform light was illuminated on the target surface to be imaged using a halogen lamp rotating together with the hyperspectral imaging sensor. Inertial Measuring Unit (IMU) was also attached to the sensor unit together with the hyperspectral camera so that sensor’s geometric information could be acquired simultaneously during imaging. All sensor and controller units were mounted on a cart-type platform for easy movement in the tunnel, and a battery mounted on the platform supplied power for system operation and the halogen light source. The developed scanning system was tested in an actual mine, and 3D hyperspectral images of the internal surface of the mine shaft were successfully obtained.

Lighting Energy Reduction by Optimizing Daylight while Maintaining Cooling Load in Tropical Educational Building, Depok, Indonesia

This study aims to reduce the lighting energy consumption in educational buildings while avoiding an increase in cooling load. The Faculty of Engineering building in Universitas Indonesia, Depok, West Java, Indonesia is used as a case study. Daylight optimization can have an impact on lighting energy, which is the largest energy consumer in educational buildings. However, given Indonesia’s tropical climate, daylight leading to heat gain is a concern. Current passive design interventions for controlling daylight and heat gain include light shelves, clerestories, and glazing materials. Daylighting performance is simulated using DIALux software. Results of each intervention are analyzed quantitatively and qualitatively by theories and parameters, namely illuminance level, light uniformity, and overall thermal transfer value (OTTV). Light shelves result in increased uniformity and lower OTTV. Clerestories result in increased average illuminance but higher OTTV. Active intervention with a dimming and grouping system is applied after daylight increases. The combination of passive design interventions and active dimming of electric lights reduces lighting energy with the same OTTV as existing. This study recommends the use of passive and active daylighting strategies considering their effect on the cooling load of buildings.

Effect of light source uniformity for imaging ellipsometry measurements

Recently, imaging ellipsometry shown a wide range of applications in a tremendous number of fields, such as material science and biomedicine. Better imaging quality helps improve measurements accuracy. However, light source of present imaging ellipsometer is usually non-uniform and its non-uniformity contributes to the systematic error. The dual microlens arrays (MLAs) can shape the non-uniform beam into a flat-field beam, effectively improving the uniformity of the light source. We simulated and calculated the ellipsometric parameters by non-uniform illumination and uniform illumination. The simulated wavelength was 400–700 nm. Mean squared error (MSE) was used to quantify the accuracy of the measurement results. The results show that a more uniform light source helps to improve the signal-to-noise ratio and measurement accuracy.

Blue-yellow emissive LaAlO<sub>3</sub>:Dy<sup>3+</sup> phosphor for high bright white light-emitting diodes

LaAlO3:Dy3+ (LAO:Dy3+) with blue-yellow emission for brilliant white light of light-emitting diodes (LEDs) was prepared using gel-combustion process. The chemical content of the created material was confirmed using energy dispersive X-ray analysis (EDX). The transmission electron microscopy was used to examine the phosphor crystal size and morphology. The luminescence analysis showed that LAO:Dy3+ phosphors exhibited peaks at 482 nm (blue) and 574 nm (yellow), attributed to the transitions 4F 9/2à6H 15/2 and 4F 9/2à6H 13/2, respectively. The investigating of correlated color temperature (CCT) and Commission International de L'Eclairage (CIE) described that the phosphor LAO:Dy3+ helped to attained good CCT coordination and bright cool-white emission under ultraviolet (UV) stimulation. However, when using in white LED fabrication, the concentration of LAO:Dy3+ should be modified to fulfill the need from manufactures. According to results from this work, the white light luminescence intensity and color rendering performance may be reduced if the LAO:Dy3+ is high (10%) because of too much scattering. On the other hand, such scattering improvements offered by LAO:Dy3+ phosphor is beneficial to reduce the color deviance for better color uniformity of light.

P‐52: Higher Brightness Mini‐LED Displays: Optimizing Collimation and Uniformity in a Thinner Form Factor

We propose a novel method for improving brightness and efficiency of BEF‐less mini‐LED displays in a thinner form factor. In place of BEFs an array of Fresnel lenses positioned over each LED followed by micro lens array diffusion films create a uniform light output. Best practices and backlight design recommendations will be discussed.

High uniformity red µ-LED array with a current efficiency of 2.6 cd/A and ns-level response time.

This paper demonstrates an AlGaInP-based 620-nm red micro-light-emitting-diode (µ-LED) array and studies the enhancement effect of the surface treatments using (NH4)2Sx solutions by comparing the characteristics of µ-LED arrays with and without the (NH4)2Sx treatment. Furthermore, our µ-LED array demonstrates a measurement of the current efficiency (2.6 cd/A), which improves the light output uniformity. Also, we apply a setup for measuring the response time at the fast ns-level to analyze the effect of passivation in AlGaInP-based µ-LED arrays.

High-sensitivity strain sensor with micron-scale imitation dumbbell structure based on differential temperature self-compensation

A micron-sized dumbbell-like -MZI structure has been developed using hydroxide flame melt taper and arc fusion discharge, with the dumbbell rod region prepared by melt taper drawing and the dumbbell sheet region prepared by arc fusion discharge. This structure has a sensitive light intensity response in the sensing field due to a double-order mode-field coupled excitation region. The geometrical parameters of the dumbbell-like system are optimized theoretically, and the feasibility of the microstructure to achieve high strain sensing sensitivity is analyzed. Experimental results show that the microstructure has a high strain sensing sensitivity of ∼ 0.074 dB/µε and a consistent temperature sensing sensitivity over the entire monitoring wavelength range. Therefore, a light intensity-dependent temperature self-compensation calculation is proposed to achieve a uniform light intensity-strain response for each characteristic peak in the monitored wavelength domain. Since the device has a significant advantage in light intensity modulation and is not affected by polarization light perturbations, it can be used as an alternative light intensity modulation device in optical communication networks and laser research. It can also be used as a probe for medical diagnostic testing based on its enhanced evanescent field properties.

Daylight And Artificial Lighting Integration In Achieving Lighting Uniformity In Educational Building

Cities are currently facing many difficulties and challenges from the effects of climate change, population growth, infrastructure, cyber attacks, to disease outbreaks. The Malioboro area is a tourist, cultural, and economic center in Yogyakarta. The Malioboro area is also one of the cultural heritage areas in the Special Region of Yogyakarta based on the Governor's Decree No. 186/2011. The Covid-19 pandemic is a newly discovered type of coronavirus which is a new virus and disease that was previously unknown before the outbreak in Wuhan, China, in December 2019 and did not take long to spread to all corners of the world (WH0,2020), including in the cultural heritage area. This paper raises research on the resilience of cultural heritage to hazards in cultural heritage areas with the aim of research as an effort to preserve cultural heritage areas with the method used is Content Analysis by collecting literature studies related to the extent to which Urban Heritage Resilience has developed to date. especially in the face of the Covid-19 pandemic. Keywords: Content Analysis; Covid-19; Malioboro; Urban Heritage Resilience

Effect of 450 nm Visible Blue Light from Light-Emitting Diode on Escherichia coli O157:H7 in Agar Gels: Optimizing the Lighting Array and Quantitative Microbial Exposure Assessment

Visible blue light emitting diodes (LED) have been studied to inactivate Escherichia coli (E. coli) O157:H7 in agar gels. The LED array was optimized to attain uniform light illumination, and the light intensity distribution was visualized through optical simulation. The uniformity of LED light intensity was assessed, and the evenly spaced array showed the best uniformity with a Petri factor of 0.99. Microbial populations in agar gels prepared with and without a dye were analyzed after light irradiation. Each segment of the gels with different heights was taken to measure microbial reduction, and the results indicated that optical properties, such as opaqueness, played an important role in microbial reduction. The agar gel without and with a dye showed a maximum reduction of <3.4 and <2.1 log CFU/g, respectively. An exposure assessment for E. coli O157:H7 was conducted based on the assumption for the agar gel product after LED illumination. The probability results indicated that a risk (>5 log CFU/g) existed mainly in the bottom layer of the sample, despite the average contamination being <5 log CFU/g. This study provides a suitable approach for designing the LED photoinactivation process and subsequent exposure assessment to avoid risk.

Lightness Perception of Fabrics Under Non-uniform and Uniform Lighting Conditions

Lightness Perception of Fabrics Under Non-uniform and Uniform Lighting Conditions

Structure optimization, optical design and thermal management of UVC LED photoreactor to improve its inactivation efficiency

Compared with the chlorine disinfection, ultraviolet light emitting diode (UV LED) has attracted extensive interest due to its advantages of environmental friendliness, wide inactivation range and easy automation. However, there are still some challenges on how to apply UV LED to water disinfection more effectively by designing and optimizing some parameters. In this manuscript, the optimal numbers, spacing and configuration of UVC LEDs are systematically studied using the thermal and optical software simulation and experiment methods. Then, the influence of the reactor shape and reflective material on inactivation efficiency of the photoreactor was studied in detail. The results show that the appropriate numbers and spacing of UVC LEDs is helpful not only to increase the average irradiance and petri factor of reactor surface but also to keep a low chip junction temperature. The simulation results of three UVC LED configurations indicate the four corners configuration exhibits the highest average irradiance and petri factor value. The introduction of reflective materials can enhance the inactivation performance, and especially the polytetrafluoroethylene (PTFE) material can effectively increase the inactivation efficiency of module by ∼42% because of higher reflectivity and light uniformity. The further inactivation experiments reveal that the designed cylinder reactor covered with PTFE materials has the maximum log inactivation value. The current research results can provide some reliable suggestions for the design and optimization of UVC LED photoreactor to improve its inactivation effect through optical simulation and experimental methods.

Design, Development and Evaluation of Photovoltaic Integrated Solar Greenhouse Dryer for Paddy

The present study was conducted at College of Agricultural Engineering, Bapatla, Andhra Pradesh, India during the month of January, 2021 to develop photovoltaic power assisted forced circulation solar greenhouse dryer and to evaluate its performance for drying of paddy. A free standing greenhouse structure with arch roof was selected to have high light transmission and low cost of construction. To get adequate and uniform light inside the greenhouse east-west orientation was selected. A frame of solar greenhouse dryer having 4.467 m length, 2.134 m width and 2.591 m height was constructed and was covered with twin wall polycarbonate sheet of 6 mm thickness. Freshly harvested paddy was filled in perforated tray with size 142.5×80×12.5 cm up to 10 cm height the trays were placed in drying chamber consists of three tires and two columns. Forced ventilation was provided with four 40 W DC fans which were powered with two 150 W photovoltaic panels. During drying, the green house and ambient air temperature, relative humidity data was collected at every 1 h interval using data logger, the moisture content of the paddy was determined at every 2 h interval. The paddy was dried till getting 12% (w.b.) final moisture content. The highest greenhouse dryer temperature of 48.1°C was recorded as compared with highest ambient temperature of34.2°C. Moreover, the air flow rate achieved was varied between 75.52‒34.25 m3m-1.In this dryer the paddy was dried from 25.3‒12.0% (w.b.) moisture content in 21 h whereas open sun drying took 28 h of drying time.

Random Silica-Glass Microlens Arrays Based on the Molding Technology of Photocurable Nanocomposites

Random microlens arrays (rMLAs) have been widely applied as a beam-shaping component within an optical system. Silica glass is undoubtedly the best choice for rMLAs because of its wide range of spectra with high transmission and high damage threshold. Yet, machining silica glass with user-defined shapes is still challenging. In this work, novel design and fabrication methods of random silica-glass microlens arrays (rSMLAs) are proposed and a detailed investigation of this technology is presented. Based on the molding technology, the fabricated rSMLAs with tunable divergent angles demonstrate superior physical properties with 1.81 nm roughness, 1074.33 HV hardness, and excellent thermal stability at 1250 °C for 3 h. Meanwhile, their characterized optical performance shows a high transmission of over 90% in the ultraviolet spectrum. The fabricated two types of rSMLAs exhibit excellent effects of beam homogenization with surprising energy utilization (more than 90%) and light spot uniformity (more than 80%). This innovative process paves a new route for fabricating rMLAs on solid silica glass and breaking down the barrier of rMLAs to broader applications.

Toward Optimum Light Curing of Resin Composite Restorations: A survey on Current Awareness and Practice among General Dentists in Saudi Arabia

Introduction: This study aimed to assess the current awareness and practices of resin composite light curing of general dental practitioners (GDPs) in Saudi Arabia and to set several evidence-based recommendations to improve the quality of the outcome of concern. Methods: An online questionnaire was created. Two hundred and fifty email invitations were sent to GDPs appointed in general governmental hospitals in five main cities in Saudi Arabia to join the survey voluntarily and anonymously. The survey consisted of 24 questions classified into the following domains: 1-Demographic criteria 2- frequency and technical aspects of resin composites application 3- criteria of the currently used light curing units and curing light. Descriptive statistics and chi-square test were used to analyse the obtained responses. Results: One hundred and fifty-six responses were received. A significant number of GDPs are significantly satisfied with the quality of their light curing, not aware of the thermal hazards of light curing, and do not check power output of their LCUs (light curing units) (P<0.05). An insignificant number of respondents use eye shields for eye protection during light curing. Conclusion: There was no uniform light curing protocol followed by respondent GDPs. GDPs in Saudi Arabia should improve their knowledge and clinical skills of light-curing resin composite.

Construction of layered double hydroxides on wood surfaces for wood coloring

Wood dyeing usually requires a large concentration of metal solution, which when released to the atmosphere as waste liquid, causes pollution. In this study, a metal-organic framework (MOF) with micron-size structure was in-situ grown on a wood surface as a template and precursor for a layered double hydroxide (LDH). The LDH had a nanoscale structure and was generated on the wood surface from ultra-low concentration NiCl2 solution. The generation was based on a hydrolytically induced exchange process between the MOF and hydroxide ions. The results of following this procedure showed that petal-like Co/Ni-LDH with micro-nano composite structure was formed on the wood surface. Due to the LDH, a uniform light green color was formed on the wood surface at a reaction temperature and time of 60 ℃ in 34 min, respectively. To improve the hydrophobicity of the LDH layer, a long chain alkyl with low surface energy was introduced into the lamellae from a sodium stearate solution, constructing a superhydrophobic layer on the wood surface. The modified wood surface showed excellent UV light aging and water resistances. Moreover, Ni2+ was replaced with Mn2+, Fe3+, Cu2+, and Zn2+ ions and dark brown, yellow, blue, and white colors, respectively, were formed on wood. The present method is also suitable for other wood. Wood surface color adjusted by LDH uses low concentration of metal salt solution and proved to be a mild and green wood color toning method.

Application of modern approaches to the synthesis of biohydrogen from organic waste

Hydrogen production with the use of biological processes and renewable feedstock may be considered an economical and sustainable alternative fuel. The high calorific value and zero emission in the production of biohydrogen make it the best possible source for energy security and environmental sustainability. Solar energy, microorganisms, and feedstock such as organic waste and lignocellulosic biomasses of different feedstock are the only requirements of biohydrogen production along with specific environmental conditions for the growth of microorganisms. Hydrogen is also named as ‘fuel of the future’. This study presents different pathways of biohydrogen production. Because of breakthroughs in R&D, biohydrogen has been elevated to the status of a viable biofuel for the future. However, significant problems such as the cost of preprocessing, oxygen-hypersensitive enzymes, a lack of uniform light illumination for photobiological processes, and other expenses requiring intensification process limits are faced throughout the biohydrogen production process. Despite concerns regarding nanoparticle (NP) toxicity at higher concentrations, proper NP concentrations may improve hydrogen production dramatically by dissolving the substrates for bacterial hydrogen transformation. The data-driven Machine Learning (ML) model allows for quick response approximation for fermentative biohydrogen production while accounting for non-linear interactions between input variables. Scaling up biohydrogen production for future commercial-scale applications requires combining cost-benefit evaluations and life cycle effects with machine learning.