Light-emitting Diode Light Source Research Articles

Study about photoinduction-based technology for trapping small brown planthopper

To provide a theory to guide the selection of the illumination parameters of light emitting diode (LED)-based light sources used for trapping Laodelphax striatellus, we used LED light sources and devices built in-house to detect L. striatellus phototactic behavior. Through phototaxis screening experiments of different light sources and the comparative experimental method, we analyzed the response patterns of L. striatellus to wavelength, light intensity, layout, flash frequency of monochromatic light sources, as well as combined color light sources, and discussed the mechanisms of the phototactic behavior of L. striatellus under different light sources. The results of the monochromatic light experiment showed that the trapping rate of the L. striatellus to the linear blue light source of 460 nm was the highest and was also significantly affected by the light intensity. The results of the experiments with the combined color light sources showed that compared with the linear 460 nm blue light source, the trapping rate of the L. striatellus was significantly improved by the polychromatic light, and the blue–green light led to the best improvement, reaching 1.5 times that of the trapping rate in the case of monochromatic light sources. The wavelength composition, light intensity, shape, and flash frequency of the light source used in this study can provide a theoretical basis for the development of LED-based light traps specifically for L. striatellus.

Performance evaluation of an LED flatbed scanner for triple channel film dosimetry with EBT3 and EBT-XD film.

We investigate the properties of a light emitting diode (LED) flatbed scanner for use with EBT3 and EBT-XD film types in a clinical radiochromic film (RCF) dosimetry program with modern treatment techniques. The flatbed scanner was characterised in terms of lateral and longitudinal response, X-Y scaling integrity, scanning reproducibility, scanner warm up dependence and film orientation dependence. The preferred lateral response artefact (LRA) corrections are investigated for the LED light source. Supporting evidence is provided regarding the dose independent nature of the corrections while also providing results suggesting a potential film type independence. Results from 2D gamma analysis of four patient treatments were compared between the new 12000XL and existing 10000XL model. Lastly, a dose uncertainty analysis was performed for the film-scanner system combination. It may be concluded that the lateral response variation requires correction while the longitudinal response variation is insignificant. The linear scaling in the lateral and longitudinal directions are within 0.5% and the scanner reproducibility is stable. Scanner warm up dependence no longer exists, and effort should be made to maintain all film orientation in a study set within 15°. The LRA corrections are as reported substantially dose independent and there is evidence to support film type independence. Comparative gamma analysis of patient specific dose maps between the EPSON 10000XL (xenon fluorescent lamp) and 12000XL (LED) scanners showed that results are indistinguishable for both film types across the two scanner models when the necessary corrections are applied. Dose uncertainty is in agreement with the literature and can be kept below 3% with necessary corrections applied.

A 3D printed photoreactor for investigating variable reaction geometry, wavelength, and fluid flow.

Research in the field of photochemistry, including photocatalysis and photoelectrocatalysis, has been revitalized due to the potential that photochemical reactions show in the sustainable production of chemicals. Therefore, there is a need for flexible photoreactor equipment that allows for the evaluation of the geometry, light wavelength, and intensity of the vessel, along with the fluid flow in various photochemical reactions. Light emitting diodes (LEDs) have narrow emission spectra and can be either pulsed or run continuously; being flexible, they can be arranged to fit the dimensions of various types of the reactor vessel, depending on the application. This study presents a 3D printed photoreactor with the ability to adjust distances easily and switch between high-power LED light sources. The reactor design utilizes customized printed circuit boards to mount varying numbers and types of LEDs, which enables multiple wavelengths to be used simultaneously. These LED modules, comprised of heat sinks and cooling fans, fulfill the higher heat dissipation requirements of high-power LEDs. The flexibility of the reactor design is useful for optimizing the reaction geometry, flow conditions, wavelength, and intensity of photochemical reactions on a small scale. The estimates for incident light intensity under five possible reactor configurations using ferrioxalate actinometry are reported so that comparisons with other photoreactors can be made. The performance of the photoreactor for differing vessel sizes and distances, in both the flow and batch modes, is given for a photochemical reaction on 2-benzyloxyphenol-a model substance for lignin and applicable in the production of biobased chemicals.

Lighting control of LEDs considering ambient sound variations to meet the requirements of smart cities

This study provides an innovative solution by including sound levels in the energy management of light-emitting diodes (LEDs). At the same time, this method increases the accuracy of individuals' decisions regarding the environmental parameters of light and sound. The introduced system determines the environment's activity level using sound sensors. By applying this strategy, the amount of light and the energy consumption of LED light sources is restricted under conditions where no activity occurs in the environment or the level of the performed activity is limited. The results of system simulation and implementation demonstrate the effectiveness of this technique. According to the findings, this method reduces energy consumption by more than 40% in the stated scenario when environmental activity is reduced. This approach is recommended as an innovative solution for the energy management of LED light sources to satisfy users' requirements in smart cities.

Silicon optrode array with monolithically integrated SU-8 waveguide and single LED light source

Objective. This paper presents a conventional light emitting diode (LED) and polymer waveguide coupled silicon optrode array. Approach. Unique lens design at the waveguide inlet enables a high light coupling efficiency with a single LED light source, and provides small power consumption compatible with a wireless optogenetic neuromodulation system. To increase the light intensity at the waveguide tip, a lensed waveguide is fabricated with epoxy-based photoresist SU-8, which has a plano-convex lens shape at the waveguide inlet to focus the light in the horizontal direction. In addition, a cylindrical lens is assembled in front of the waveguide inlet to focus the source light in the vertical direction. Main results. The glass cylindrical lens and SU-8 plano-convex lens increased the light coupling efficiency by 6.7 dB and 6.6 dB, respectively. The fabricated 1 × 4 array of optrodes is assembled with a single LED with 465 nm wavelength, which produces a light intensity of approximately 2.7 mW mm−2 at the SU-8 waveguide outlet when 50 mA input current is applied to the LED. Each optrode has four recording electrodes at the SU-8 waveguide outlet. The average impedance of the iridium oxide (IrO x ) electroplated recording electrodes is 43.6 kΩ. Significance. In-vivo experiment at the hippocampus region CA1 and CA2 demonstrated the capability of optical stimulation and neural signal recording through the LED and SU-8 waveguide coupled silicon optrode array.

Assessment of spectral properties of positive dysphotopsia or glare caused by LED sources for different types of intraocular lenses.

Light emitting diodes (LEDs) have become a major source of lighting conditions. The increased prevalence of LED light sources introduces new concerns for the spectral effects of positive dysphotopsia (PD) or glare type photic phenomena for pseudo-phakic patients with intraocular lenses (IOLs). A significant amount of work has been published in the area of spectral discomfort and sensitivity of LEDs as well as automotive lighting. The wavelength dependence or spectral properties of PD due to LEDs for IOLs has not been reported. This study, to our knowledge, is the first one to assess the glare characteristics of four commercially available IOL models with different material types and design features using an optical bench and non-sequential ray trace simulations with LEDs of different wavelengths. A novel approach of representing the reflected and transmitted IOL glare utilizing Fresnel coefficients is found to be in close agreement with the measurements.

Large-molecular-weight acyldiphenylphosphine oxides as low-mobility type I photoinitiator for radical polymerization

In recent years, the light source for photopolymerization technology is evolving from energy-hungry mercury lamps to the safer light-emitting diodes (LEDs), and it is urgent to develop new photoinitiator adapted to the photopolymerization system with LED light source. Some acyldiphenylphosphine oxide photoinitiators have been designed and developed for LED light source, but their application is severely limited in the fields of food packing, medical equipment, environmentally-friendly product etc. due to their high mobility in photocured polymers. In this study, eight acyldiphenylphosphine oxide molecules (DAPO-1 ∼ DAPO-8) were synthesized by introducing large molecular weight groups and their UV–visible absorption, photodegradation quantum yield, photopolymerization properties, mobility and solubility in monomer were determined. Thereinto, photoinitiators show lower mobility than TPO, the photoinitiator commonly used in industry, as well as good solubility in monomers and excellent photopolymerization performance. Therefore, they can serve as potential substitutes for commercial TPO, especially in the application of low-migration photocurable system.

A thermal-stable Mn4+-doped far-red-emitting phosphor-converted LED for indoor plant cultivation

Artificial light-emitting diode (LED) light source, regarded as a front-runner technology for the promoting of plant growth, has attracted much attention toward the burgeoning fertilizer-free indoor plant cultivation. It still remains a challenge that explore a far-red-emitting phosphor of high-thermal stability. Overall, we report a Mn4+ ion-doped ordered double perovskite tungstates prepared by high-temperature solid-state reaction method in air. The crystal structure, morphology, and fluorescence properties were investigated and discussed in detail. The far-red emission of the optimized CaSrMgWO6:1%Mn4+, covering the wavelength region of 630–780 nm, matches the absorption ranges of the chlorophyll a and phytochrome (Pfr). The value of Dq/B is estimated to be 2.81. Most notable is the excellent thermal quenching resistance of the Mn4+ emission, remaining 86.7% at 150 °C, thereby suitably fabricating a far-red LED device. The LED light-driven regulation of the physiological and biochemical changes enables a proof-of-concept garlic cultivation. The growth of weight, stem length, and root length of the garlic was significantly promoted with the extra supply of the far-red light. This work demonstrates that the as-obtained far-red-emitting phosphor holds a promising perspective for the phosphor-converted far-red LED light sources toward the flourishing fertilizer-free indoor plant cultivation.

ARM-Based Indoor RGB-LED Visible Light Communication System

As a new green solid-state light source, semiconductor light-emitting diodes (LEDs) have the advantages of low power consumption, small size, long life, short response time, and good modulation performance. At the same time, the frequency band to which LED light sources belong does not require regulatory registration, thus alleviating the current problem of spectrum scarcity for wireless communications. However, white LED-based visible light communication (VLC) systems suffer from limited bandwidth and low energy efficiency. Therefore, an ARM-based indoor RGB-LED VLC system is proposed. Firstly, the three RGB colours are mixed into white light, thus obtaining a larger modulation bandwidth than normal white LEDs while illuminating normally. Secondly, the S3C6410 processor is used to modulate and demodulate the RGB-LEDs with biased light OFDM, thus obtaining a high spectrum utilisation while ensuring system transmission stability. Then, according to the characteristics of the light source of the VLC system, the leading and window functions used in the optical network transceiver module are designed to improve the communication energy efficiency of the system. Finally, functional tests were carried out on an ARM development board. The experimental results show that with a single RGB-LED light source, the maximum transmission distance is 5 cm, the maximum average delay is 68 ms, the maximum throughput is 25 Mbps, and the BER is controlled below 3.2 × 10−3, which meets the basic communication requirements.

Light-Emitting Diode (LED) Phototherapy versus Non-LED Phototherapy Devices for Hyperbilirubinemia in Neonates: A Systematic Review and Meta-analysis.

This review was conducted to evaluate the efficacy of light-emitting diode (LED) phototherapy as compared with the conventional phototherapy in neonates with unconjugated hyperbilirubinemia and their adverse effects. We searched the following databases right from their inception till April, 2021: MEDLINE, EMBASE, Cochrane Library, and LILACS. Randomized clinical trials (RCTs) comparing the LED phototherapy with other light sources, which enrolled newborns (term and preterm) with unconjugated hyperbilirubinemia were included. We included 21 articles in this review. The treatment with the LED light therapy had a lower failure rate as compared with the non-LED one (RR = 0.60, 95% CI: 0.39-0.94). The mean duration of phototherapy was significantly shorter in the group with the LED light source as compared with the one with the non-LED light source (mean difference [hours]: -8.07, 95% CI: -8.45 to -7.68), regardless of the type of non-LED units. However, the rate of bilirubin showed a comparable decline (mean difference [mg/dL/h]: 0.01, 95% CI: -0.00, 0.03) in both the light sources, irrespective of irradiance or distance. No studies reported primary outcomes related to the neurotoxicity effects of hyperbilirubinemia in neonates. The LED light devices caused a significantly higher risk of hypothermia. Neonates were at a lower risk of developing hyperthermia and skin rash with the LED light therapy. Our findings provide support for the use of LED light source phototherapy due to its better clinical efficacy, which is evidenced by its shorter duration and lower rate of treatment failure, as compared with the non-LED light sources. KEY POINTS: · The efficacy of phototherapy is dependent on specific characteristics of light sources of phototherapy devices.. · LED phototherapy demonstrated better efficacy with shorter duration and lower rate of treatment failure.. · Adverse effects of phototherapy devices such as hypothermia, hyperthermia, and skin rash should be monitored..

LED lighting as an effective tool for regulating plant morphogenesis

The results of studying the effect of light with different spectral composition on the morphogenesis of wild-type of Arabidopsis thaliana (Col 0), as well as wei8-1tar1-1 and ahk2 mutants with modified signal transduction processes of auxins and cytokinins. We used a specially developed technique that simplifies the assessment of the effect of light on the growth and development of A. thaliana plants, especially the configuration of their root system during the entire growing season. Luminescent (LL) and light-emitting diode (LED) light sources were used, which made it possible to vary the physiologically significant blue (B), green (G), red (R), and far red (FR) spectral ranges. The R/B ratio was equal to 1 and 4 for LED 1 and LED 2 lighting options, respectively, at the same total flux density of B and R light photons. The ratios of R/FR and B/G in the spectra of LED illumination varied in the ranges closest to those observed in natural conditions. The most effective for the formation of the root system, rosette of leaves and inflorescences of A. thaliana (Col 0) was LED illumination with R/B = 4, B/G = 1 and R/FR = 6. The obtained data indicate an important role of AHK2 histidine kinase receptors in stimulation of the formation of vegetative organs of A. thaliana in response to an increase in the level of R and a decrease in B light (an increase in the R/B ratio) in complex spectral compositions. At the same time, LED lighting with a higher level of B and a low level of R light (R/B = 1, B/G = 2 and R/FR = 3) rather effectively stimulated the accumulation of the dry mass of the root system and the formation of inflorescences compared to fluorescent lighting. Stimulation of root growth by light of this spectral composition is probably mediated by a significant increase in the level of endogenous auxins. The decrease in the R/FR ratio in the spectrum of LED sources compared to the fluorescent lamp contributed to the stimulation of flowering of A. thaliana, regardless of the nature of the mutation and despite other differences in the spectral composition.

Ultraviolet actinometry – Determination of the incident photon flux and quantum yields for photochemical systems using low-pressure and ultraviolet light-emitting diode light sources

The study of the interaction of light with photochemical and photobiological systems requires an accurate assessment of the incident photon flux. The determination of photon fluxes for various light sources (monochromatic and polychromatic) has an inherent advantage since the use of standard quantum yields for the actinometer assures that the photon flux has been calculated against accepted standards. Alternatively, if the photon flux is known, chemical actinometry can be used to determine quantum yields. This study illustrates how incident photon fluxes and quantum yields can be estimated for photochemical and photobiological systems. First, an example is developed to calibrate a spectroradiometer using a low-pressure (LP) UV lamp using either the ferrioxalate or iodide/iodate actinometers. The Calibration Factors (CFs) (defined as the ratio between the actinometer and the spectroradiometer) agreed very well, demonstrating the consistency of quantum yields between well-researched actinometers. Second, since UV-LEDs have a bandwidth almost twice that of LP lamps, should UV-LEDs be treated as monochromatic or polychromatic light sources? Results showed no significant differences between the monochromatic analysis and the polychromatic analysis. Third, the uridine quantum yield is 0.025 ± 0.001 over the 254–279 nm wavelength range, independent of these wavelengths.

Near-Infrared Light-Emitting Diodes utilizing a Europium-Activated Calcium Oxide Phosphor with External Quantum Efficiency of up to 54.7.

Near-infrared (NIR) luminescence materials with broadband emissions are necessary for the development of light-emitting diodes (LEDs) based light sources. However, most known NIR-emitting materials are limited by their low external quantum efficiency. This work demonstrates how the photoluminescence quantum efficiency of europium-activated calcium oxide (CaO:Eu) NIR phosphor can be significantly improved and stabilized at operating temperatures of LEDs. A carbon paper wrapping technology is innovatively developed and used during the solid-state sintering to promote the reduction of Eu3+ into Eu2+ . In parallel, the oxygen vacancies in the CaO lattice are repaired utilizing GeO2 decomposition. Through this process, a record-high external quantum efficiency of 54.7% at 740 nm is obtained with a thermal stability greatly improved from 57% to 90% at 125°C. The as-fabricated NIR-LEDs reach record photoelectric efficiency (100 mA@23.4%) and output power (100 mA @ 319.5 mW). This discovery of high-performance phosphors will open new research avenues for broadband NIR LED light sources in a variety of photonics applications.

Temperature and luminosity outputs of endoscopes used in transcanal endoscopic ear surgery: an experimental study.

To establish the relationship between endoscope temperatures and luminosity with a variety of light source types, endoscope ages, endoscope sizes, angles and operative distance in transcanal endoscopic ear surgery. Transcanal endoscopic ear surgery was simulated in an operating theatre using 7 mm plastic suction tubing coated in insulating tape. An ATP ET-959 thermometer was used to record temperatures, and a Trotec BF06 lux meter was used to measure luminosity. Luminosity and temperature recordings were taken at 0 mm and 5 mm from the endoscope tip. Thermal energy transfer from operating endoscopes is greatest when: the light intensity is high, there is a light-emitting diode light source and the endoscope is touching the surface. Additionally, larger-diameter endoscopes, angled endoscopes and new endoscopes generated greater heat. It is recommended that operative light intensity is maintained at the lowest level possible, and that the surgeon avoids contact between patient tissues and the endoscope tip.

Optimal Spatial Coherence of a Light-Emitting Diode in a Digital Holographic Display

The coherence of a light source is a vital aspect regarding the image quality of holographic contents. Generally, the coherence of the light source is the reason for speckle noise in a holographic display, which degrades the image quality. To reduce the speckle noise, partially coherent light sources such as light-emitting diodes (LED) have been studied. However, if the coherence of the light source is too low, the reconstructed image will blur. Therefore, using a spatial filter to improve the spatial coherence of LEDs has been proposed. In this study, we analyze the effect of the spatial and temporal coherence of the LED light source in a digital holographic display, and the optimal spatial coherence is determined. For this purpose, we devised an optical structure to control the spatial coherence in a holographic display system using a digital micro-mirror device (DMD). Here, the DMD functions as a dynamic spatial filter. By evaluating the change in the holographic image quality according to the spatial filter size, we obtained an optimal spatial filter size of 270 µm in our system. The proposed method is expected to be useful for selecting the optimal coherence of the light source for holographic displays.

Headlamp design with an additional midfield mask for removal of specific illumination including glare

In this paper, a bicycle light-emitting diode (LED) headlamp is design for the purpose of meeting the regulation and removing the unwanted reflection of some specific parts. In addition to the optical design of the headlamp, a three-dimensional mask is designed to block the LED light source to remove the specific unwanted light on the front tyre of the bicycle and then reduce the glare effect to the rider. The experimental results show that the 3D mask can effectively eliminate 97.7% of the unwanted light on the wheel of the bicycle and keeps 98.6% of the original illuminance at the A point of the K-mark regulation. The proposed mask approach will be helpful to the design by using LED as a light source.

The Embedded System to Control the Illuminance of an Office Workplace with LED Light Sources

In the paper, an embedded system dedicated to control lighting of the workplace is proposed. The construction of the considered lighting system with a power LED (Light Emitting Diode) and the idea of its control are presented. Some results of investigations of the constructed lighting system, particularly those of the measurements of its optical and electrical parameters, are shown and discussed. The presented results show that by using this system, it is possible to obtain a high value of lighting uniformity in the workplace at different values of the main lighting in the room. The control is fast, and none of the reaction times achieved during the tests exceeded even 1 s while ensuring a smooth change. Although the layout and algorithms used are simple, it can be considered an advantage as they do not introduce unnecessary complexity while meeting all the requirements of standards. A discussion of the obtained results is given, particularly in the range of energy savings.

Rose Bengal-Mediated Photodynamic Therapy to Inhibit Candida albicans.

Invasive Candida albicans infection is a significant opportunistic fungal infection in humans because it is one of the most common colonizers of the gut, mouth, vagina, and skin. Despite the availability of antifungal medication, the mortality rate of invasive candidiasis remains ~50%. Unfortunately, the incidence of drug-resistant C. albicans is increasing globally. Antimicrobial photodynamic therapy (aPDT) may offer an alternative or adjuvant treatment to inhibit C. albicans biofilm formation and overcome drug resistance. Rose bengal (RB)-mediated aPDT has shown effective cell killing of bacteria and C. albicans. In this study, the efficacy of RB-aPDT on multidrug-resistant C. albicans is described. A homemade green light-emitting diode (LED) light source is designed to align with the center of a well of a 96-well plate. The yeasts were incubated in the wells with different concentrations of RB and illuminated with varying fluences of green light. The killing effects were analyzed by the plate dilution method. With an optimal combination of light and RB, 3-log growth inhibition was achieved. It was concluded that RB-aPDT might potentially inhibit drug-resistant C. albicans.

Fabrication and application of a wireless high-definition endoscopic system in urological surgeries.

To introduce a wireless high-definition endoscopic system (WHES) and compare it with a Storz high-definition (HD) system for image resolution, colour resolution, weight, and costs. The WHES incorporated a portable light-emitting diode light source and a wireless camera module, which can be compatible with different types of endoscopes. Images were wirelessly transmitted to a monitor or mobile platform such as smartphone through a receiver. The International Standards Organization 12233 resolution chart image was used for the comparison of image resolution and Munsell Colour Checker Chart for colour resolution. In all, 38 endourologists used a Likert questionnaire to blindly evaluate cystoscopic images from a patient with haematuria. The surgical team was asked about the overall performance of the WHES in 20 laparoscopic adrenalectomies using a unvalidated subjective survey. There was no difference in image resolution between the two systems (5.82 vs 5.89 line pairs/mm). Without lens and respective light sources, there were better purple (ΔE = 21.48 vs 28.73), blue (ΔE = 34.88 vs 38.6) and red colour resolution (ΔE = 29.01 vs 35.45) for the WHES camera (P < 0.05), but orange (ΔE = 43.45 vs 36.52) and yellow (ΔE = 52.7 vs 35.93) resolutions were better for the Storz HD camera (P < 0.05). Comparing the WHES to a Storz laparoscopic system, the Storz system still had better resolution of orange and yellow, while the resolution of purple, blue, and red was similar for the two systems. The expert comments on resolution, brightness, and colour for cystoscopy were not statistically different, but the ergonomics score for the WHES was higher (3.7 vs 3.33, P = 0.038). The overall cost of the WHES was $23 000-25 000 compared with $45 000-50 000 for a Storz system. There were 100% general satisfaction for the WHES in the survey. We developed a new WHES that provides the same resolution images as a Storz laparoscopic system and acceptable colour resolution with the advantages of wireless connection, small volume, low cost, portability, and high-speed wireless transmission.

Enhanced viral inactivation by combined ultraviolet light and heat

Viral sensitivity to high temperature and ultraviolet (UV) irradiation has been extensively studied. However, there is still little attention paid to study the joint effect of these two physical factors. Since the outbreak of the COVID-19 pandemic has necessitated the advances of disinfection techniques, rapid and effective viral inactivation by combining heat and UV light is worth investigating. This work focuses on developing such a device combining UV light-emitting diode light sources and a heater. Moreover, two UV bands have been studied in this work, namely 280 nm ultraviolet-C (UVC) and 365 nm ultraviolet-A (UVA. A) control system is developed to accurately control both the heating temperature of the device and the irradiance of the dual-spectral UV light sources. The performance of the device is verified by a series of experimental measurements. More importantly, the disinfection effect of the device has been verified by the experiments based on non-pathogenic carrier virus commonly used in the laboratory. The disinfection doses of the 280 nm UVC and 365 nm UVA light sources under the high temperature synergy have been examined. The experimental results show that when combined with a heating temperature of 60 ∘C, the cumulative UV radiation doses required for sufficient viral inactivation can be greatly reduced.