Infrared LED Research Articles

High-speed and High-current Phase Width Modulator Driver for High-power Infrared LEDs

High-speed and High-current Phase Width Modulator Driver for High-power Infrared LEDs

Energy Generating Electronic Skin With Intrinsic Tactile Sensing Without Touch Sensors

Electronic skin (eSkin) with various types of sensors over large conformable substrates has received considerable interest in robotics. The continuous operation of large number of sensors and the readout electronics make it challenging to meet the energy requirements of eSkin. In this article, we present the first energy generating eSkin with intrinsic tactile sensing without any touch sensor. The eSkin comprises a distributed array of miniaturized solar cells and infrared light emitting diodes (IRLEDs) on soft elastomeric substrate. By innovatively reading the variations in the energy output of the solar cells and IRLEDs, the eSkin could sense multiple parameters (proximity, object location, edge detection, etc.). As a proof of concept, the eSkin has been attached to a 3-D-printed hand. With an energy surplus of 383.6 mW from the palm area alone, the eSkin could generate more than 100 W if present over the whole body (area ~1.5 m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ). Further, with an industrial robot arm, the presented eSkin is shown to enable safe human-robot interaction. The novel paradigm presented in this article for the development of a flexible eSkin extends the application of solar cell from energy generation alone to simultaneously acting as touch sensors.

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Earlier design and use of photographic rigs for recording insects in free flight, and the applications and shortcomings of those efforts are reviewed. Improvements included the following: Replacement of laser beams with infrared (IR) LED beam-emitters and IR phototransistor detectors; an array of nine intersection points to increase the possibility of capturing images; improved electronic circuitry to avoid multiple image capture; more energy-efficient and smaller UV light sources to attract insects; a more rigid aluminium frame to support the UV and IR LED transmitters and detectors; development of an ultra-high-speed flash system 5 μs, or faster, to produce even sharper images than those produced by the 25 μs standard speedlight flash units set at 1/128th power; and a transportable wooden box to house all the electronic components and mounts for cameras and speedlights. This paper describes the design features of the rig and its use in the field and illustrates and compares photographic results obtained using a variety of photographic techniques aimed at providing high quality, sharp, images of insects in free flight, continuous traces of the flight pattern of insects, strobe images, and combinations of these techniques. From these images reasonably accurate estimates of insect size, wing beat frequency, flight speed, and information on mechanics of flight can be obtained.

Quantitative analysis of fat and protein concentrations of milk based on fibre-optic evaluation of back scattering intensity

Optical back-scattering from milk with various fat and protein concentrations were evaluated in a back-scattering configuration using white, violet, blue, green, red or near infrared (NIR, λ = 850 and 940 nm) LEDs as the light source. The tip of the optical fibre bundle was dipped into the milk with fat and protein concentrations from 8.2 to 39 g L−1 and 32 to 37.7 g L−1, respectively. The back-scattering intensities varied linearly with the fat and protein concentrations of the milk. The slope (G) of calibration lines varied with the wavelength of the incident light. The G of the fat concentrations became zero at wavelength around λ = 520 nm and that of the protein concentrations was much smaller than that of the fat concentrations at NIR wavelengths. The fat and protein concentrations can therefore be measured separately based on the scattering intensities by selecting the wavelength for measurement.

Efficacy of LED Infrared Warming in the Periphery of the Human Body – First Investigations in a Subject using Thermography

In this technical report, we present for the first time a newly developed multimodal light-emitting diode (LED) pad for photobiomodulation (PBM). In order to demonstrate the range of possibilities for its application, we carried out a comparison of measurements with and without infrared (IR) LEDs in a volunteer, and are presenting the results. The pad consists of several components, which are mainly composed of LEDs of different modalities (IR, red, yellow, and blue). This multicolor system was applied to a peripheral area of the body in the volunteer. Thermal imaging of the region of interest showed that additional stimulation with IR LEDs increased temperature by about 113% compared to stimulation without IR LEDs. Our results concluded that non-visible IR LED stimulation techniques could be extremely helpful in improving the quality of PBM.

An LED-Driven AuNPs-PDMS Microfluidic Chip and Integrated Device for the Detection of Digital Loop-Mediated Isothermal DNA Amplification.

The sensitive quantification of low-abundance nucleic acids holds importance for a range of clinical applications and biological studies. In this study, we describe a facile microfluidic chip for absolute DNA quantifications based on the digital loop-mediated isothermal amplification (digital LAMP) method. This microfluidic chip integrates a cross-flow channel for droplet generation with a micro-cavity for droplet tiling. DNA templates in the LAMP reagent were divided into ~20,000 water-in-oil droplets at the cross-flow channel. The droplets were then tiled in the micro-cavity for isothermal amplification and fluorescent detection. Different from the existing polydimethylsiloxane (PDMS) microfluidic chips, this study incorporates gold nanoparticles (AuNPs) into PDMS substrate through silica coating and dodecanol modification. The digital LAMP chip prepared by AuNPs-PDMS combines the benefits of the microstructure manufacturing performance of PDMS with the light-to-heat conversion advantages of AuNPs. Upon illumination with a near infrared (NIR) LED, the droplets were stably and efficiently heated by the AuNPs in PDMS. We further introduce an integrated device with a NIR heating unit and a fluorescent detection unit. The system could detect HBV (hepatitis B virus)-DNA at a concentration of 1 × 101 to 1 × 104 copies/μL. The LED-driven digital LAMP chip and the integrated device; therefore, demonstrate high accuracy and excellent performance for the absolute quantification of low-abundance nucleic acids, showing the advantages of integration, miniaturization, cost, and power consumption.

Penetrating Biological Tissue Using Light-Emitting Diodes with a Highly Efficient Near-Infrared ScBO3:Cr3+ Phosphor

Recently, infrared (IR) light-emitting diodes (LEDs) have attracted considerable interest in the research field worldwide. IR phosphors, the basic materials utilized in LEDs, have become a research hotspot as well. Here, we introduce the high-quantum-efficiency IR ScBO3:Cr3+ phosphor, which provides a spectral range of emission from 700 to 1000 nm with a peak maximum at 800 nm. Electron paramagnetic resonance spectroscopy, with high element selectivity, was used to elucidate the unusual small peak in the photoluminescence spectrum. Phonon structure and electron–lattice interaction were well observed and discussed via temperature-dependent measurements. Moreover, the high quantum efficiency of 72.8% was achieved. To evaluate their potential practical application, phosphor-converted LED packages were designed, which revealed high stability and high output power of 39.11 mW. Furthermore, the fabricated IR LED demonstrated a remarkable ability to penetrate biological tissues. This study provides insights into the luminescent properties and the practical applications of IR LEDs.

Rapid stimulation of cellular Pi uptake by the inositol pyrophosphate InsP8 induced by its photothermal release from lipid nanocarriers using a near infra-red light-emitting diode.

Inositol pyrophosphates (PP-InsPs), including diphospho-myo-inositol pentakisphosphate (5-InsP7) and bis-diphospho-myo-inositol tetrakisphosphate (1,5-InsP8), are highly polar, membrane-impermeant signaling molecules that control many homeostatic responses to metabolic and bioenergetic imbalance. To delineate their molecular activities, there is an increasing need for a toolbox of methodologies for real-time modulation of PP-InsP levels inside large populations of cultured cells. Here, we describe procedures to package PP-InsPs into thermosensitive phospholipid nanocapsules that are impregnated with a near infra-red photothermal dye; these liposomes are readily accumulated into cultured cells. The PP-InsPs remain trapped inside the liposomes until the cultures are illuminated with a near infra-red light-emitting diode (LED) which permeabilizes the liposomes to promote PP-InsP release. Additionally, so as to optimize these procedures, a novel stably fluorescent 5-InsP7 analogue (i.e., 5-FAM-InsP7) was synthesized with the assistance of click-chemistry; the delivery and deposition of the analogue inside cells was monitored by flow cytometry and by confocal microscopy. We describe quantitatively-controlled PP-InsP release inside cells within 5 min of LED irradiation, without measurable effect upon cell integrity, using a collimated 22 mm beam that can irradiate up to 106 cultured cells. Finally, to interrogate the biological value of these procedures, we delivered 1,5-InsP8 into HCT116 cells and showed it to dose-dependently stimulate the rate of [33P]-Pi uptake; these observations reveal a rheostatic range of concentrations over which 1,5-InsP8 is biologically functional in Pi homeostasis.

Infrared light-emitting diodes based on colloidal PbSe/PbS core/shell nanocrystals**Project supported by the National Key Research and Development Program of China (Grant No. 2016YFB0401702), the National Natural Science Foundation of China (Grant Nos. 61674074 and 61405089), Development and Reform Commission of Shenzhen Project, China (Grant No. [2017]1395), Shenzhen Peacock Team Project, China (Grant No. KQTD2016030111203005), Shenzhen Key Laboratory for Advanced Quantum

Colloidal PbSe nanocrystals (NCs) have gained considerable attention due to their efficient carrier multiplication and emissions across near-infrared and short-wavelength infrared spectral ranges. However, the fast degradation of colloidal PbSe NCs in ambient conditions hampers their widespread applications in infrared optoelectronics. It is well-known that the inorganic thick-shell over core improves the stability of NCs. Here, we present the synthesis of PbSe/PbS core/shell NCs showing wide spectral tunability, in which the molar ratio of lead (Pb) and sulfur (S) precursors, and the concentration of sulfur and PbSe NCs in solvent have a significant effect on the efficient PbS shell growth. The infrared light-emitting diodes (IR-LEDs) fabricated with the PbSe/PbS core/shell NCs exhibit an external quantum efficiency (EQE) of 1.3 % at 1280 nm. The ligand exchange to optimize the distance between NCs and chloride treatment are important processes for achieving high performance on PbSe/PbS NC-LEDs. Our results provide evidence for the promising potential of PbSe/PbS NCs over the wide range of infrared optoelectronic applications.

Leaf Scanner: A portable and low-cost multispectral corn leaf scanning device for precise phenotyping

During recent years, portable plant phenotyping instruments have become increasingly important to monitor conditions of plant health non-destructively in the greenhouse and field environments. These devices, such as the Soil Plant Analysis Development (SPAD) meter, leverage indices that represent leaf chlorophyll content due to its strong correlation with leaf nitrogen (N) content. However, instruments such as SPAD meters are expensive and measure only individual, restricted leaf regions per data capture. In this publication, we developed a Leaf Scanner device to analyze the chlorophyll content distributions of whole leaves with greater efficiency and precision. The validating samples for this device were top-collared corn leaves grown under high and low N treatments in a greenhouse. For each region of a corn leaf, this device rapidly flashed visible and near infrared (NIR) LEDs to obtain the visible and NIR transmittance images of leaves. These images were summarized pixel-wisely into the Green NDVI index. A sufficient high framerate permitted continuous collection of regional index images. Using image registration techniques, these regional images were stitched together into a ‘leaf panorama’. The total pixel amount of each leaf panorama, thus, served as a substitute for leaf area. A Minolta SPAD-502Plus meter collected ground-truth measurements along the length of each leaf sample. The results showed that there was a strong correlation between the average Leaf Scanner’s measurements and averaged SPAD values (R2 = 0.92), and the Leaf Scanner was able to clearly detect differences between high and low fertilized samples in terms of chlorophyll content and leaf area. Furthermore, this Leaf Scanner device enabled us to study the chlorophyll content distributions on the plants under different treatments.

Modular Carrier Board and Package for Infrared LED Arrays

Infrared scene projectors (IRSPs) are a critical laboratory tool for setup, calibration, and testing of infrared sensors. Infrared light emitting diode projectors are evolving to handle higher resolution, faster frame rates, and higher cooling power. New cryogenic packaging that can support these advanced features is needed. This paper describes a new cryogenic package design that enables higher resolutions and faster frame rates. The resulting modifications to the IRSP system hardware are described.

Effect of Al co-doping on the luminescence properties of Nd3+-doped TiO2 thin films

Co-doping Aluminium (Al) with neodymium (Nd) is shown to have a sensitizing effect on the rare earth luminescence in thin film titanium dioxide (TiO2) host materials. Whilst the Al co-doping has the effect of quenching the direct (resonantly) excited, steady state photoluminescence from Nd3+ emitting centers, for indirect (non-resonant) excitation, the emission is enhanced with increasing Al. Time-resolved PL measurements reveal a decrease in both the excitation/de-excitation rates (increases in lifetime) with increasing Al co-doping, confirming the indirect nature of excitation and implying a suppression of non-radiative de-excitation of the Nd3+ centers in TiO2. Suppression of non-radiative processes by Al is considered to be the result of reduced rare earth clustering, which is known to promote de-excitation via energy migration and thus has important implications for improved efficiency infra-red LED materials.

Transition and Motion Sensing System with Nintendo Wiimote and Infra-Red LEDs Array

In this work, a gesture and motion sensing system is explored with the Nintendo Wiimote and infra-red LEDs array. With the eminent Nintendo Wiimote controller, the personal computers and terminals can be connected to the system easily via Bluetooth wireless communication system. Although there are many devices that can be used to track the gesture and motion, they are able to connect to another device easily. The developed system is capable of making different applications as the interfacing problem has resolve. C# programming language is used to develop the graphical user interface and the mathematical algorithm. In order to verify the developed system, the transition of presentation slide is tested. By adjusting the sensitivity and threshold via mathematical formula, the gesture and motion sensing system is working excellently.

High Q-factor near infrared and visible Al2O3-based parallel-plate capacitor kinetic inductance detectors.

We designed, fabricated and characterized parallel-plate capacitor lumped-element kinetic inductance detectors (LEKIDs) to operate at near-infrared and optical wavelengths (0.3 -1 μm). The widely used interdigitated capacitor is replaced by a parallel-plate capacitor which, for a given resonance frequency, has a larger capacitance value within a much smaller space allowing to strongly reduce the size of the pixels. The parallel-plate capacitor LEKID array comprises 10 × 10 pixels. The inductive meander is patterned from stoichiometric 52 nm-thick TiN film (Tc ≈4.6 K). The parallel-plate capacitor is made of a TiN base electrode, Al2O3 dielectric and Nb upper electrode. More than 90 resonances out of 100 within the 0.994-1.278 GHz band were identified. The resonances exhibit internal Q-factors up to ∼370 000 at 72 mK. The array was illuminated using a white light and 890 nm monochromatic near infrared LEDs. The estimated quasiparticle lifetime is τqp≈13 µs.

IR Transceiver Irradiation Characteristics on Bubble/Slug Flow Regimes in Conventional and Minichannels

Multiphase fluid flows commonly occur in petrochemical, biotech, food, and process industries. Extraction and flow of crude oil is an example of multiphase solid, liquid, and gas flows. In this paper, the output signal characteristics of an infrared (IR) transceiver sensing system during the two-phase flows of air–water mixture inside a 2.64 mm diameter and 0.30-mm-thick glass tube is presented. An optimized distance between IR LED (transmitter) and center of the test section is predicted using COMSOL Multiphysics so that the receiver senses maximum number of photons. The experiments are done for the optimized distance to analyze bubble/slug of varying length and shapes. High-speed imaging is used for image registration of the flow regimes. A numerical model is developed with COMSOL package to understand the signal characteristics for multiple bubble/slug of varying sizes and is validated with the experimental results. Also with the developed model, a method is proposed to predict the liquid film thickness in mini/microtubes of diameters 3.42, 1.51, and 0.62 mm inner diameter and 0.60-, 1.50-, and 2.57-mm thickness, respectively. The results can be used to design IR transceiver array to measure the liquid film thickness in two-phase flow online.

Al-light

Inappropriate alcohol drinking may cause health and social problems. Although controlling the intake of alcohol is effective to solve the problem, it is laborious to track consumption manually. A system that automatically records the amount of alcohol consumption has a potential to improve behavior in drinking activities. Existing devices and systems support drinking activity detection and liquid intake estimation, but our target scenario requires the capability of determining the alcohol concentration of a beverage. We present Al-light, a smart ice cube to detect the alcohol concentration level of a beverage using an optical method. Al-light is the size of 31.9 x 38.6 x 52.6 mm and users can simply put it into a beverage for estimation. It embeds near infrared (1450 nm) and visible LEDs, and measures the magnitude of light absorption. Our device design integrates prior technology in a patent which exploits different light absorption properties between water and ethanol to determine alcohol concentration. Through our revisitation studies, we found that light at the wavelength of 1450 nm has strong distinguishability even with different types of commercially-available beverages. Our quantitative examinations on alcohol concentration estimation revealed that Al-light was able to achieve the estimation accuracy of approximately 2 % v/v with 13 commercially-available beverages. Although our current approach needs a regressor to be trained for a particular ambient light condition or the sensor to be calibrated using measurements with water, it does not require beverage-dependent models unlike prior work. We then discuss four applications our current prototype supports and future research directions.

Indoor mobile robot self-localization based on a low-cost light system with a novel emitter arrangement

This paper proposes a low-cost infrared (IR) LED system with a novel arrangement that enables the self-localization of an indoor mobile robot. The proposed system uses only low-cost IR LED emitters installed on the ceiling of a building and low-cost IR receivers, each equipped with a photodiode, located on top of the mobile robot for detection. The IR LEDs, which are driven by an on-off keying modulator with various frequencies, are used as active landmarks. The mobile robot localizes itself based on the IR LED signals it receives. Although it would be desirable to assign a unique ID to each emitter, this would be difficult to realize because of the limited number of available frequencies and the production cost resulting from the use of independent microcontrollers. Therefore, we designed a novel landmark configuration consisting of an IR LED array with unique ID-encoding capabilities based on a combination of different frequencies and the repeated use of each ID encoding LED to address the problem of limited frequencies. The novel landmark arrangement reduces the costs associated with production, ID encoding, and computation. A Monte-Carlo localization method with a belief function is utilized to estimate the position and orientation of the mobile robot based on the decoded ID information and received signal strength. The proposed system was tested in a real environment and the experimental results confirmed the validity and accuracy of the system and method.

A Low-Profile Digital Eye-Tracking Oculometer for Smart Eyeglasses.

Wearable eye tracking devices have broad uses in medicine, psychology, augmented & virtual reality and consumer market research. Most mobile eye trackers available today utilize infrared imaging of the pupil and corneal reflections with video cameras. This tracking method requires sophisticated real-time processing of video signals consuming substantial electrical power. This method is thus unsuitable for light weight wearables such as adaptive smart eyeglasses for correction of presbyopia. In this paper we present a low-profile, low-power (7.7 mJ/sample) digital eye tracker oculometer based on infrared sclera tracking. The system is implemented using eight, 24-bit infrared proximity sensors and synchronous infrared LEDs. The pupil location is determined from 32 reflected pulsed light measurements independent of ambient illumination. The digital oculometer is 3.1 mm thick and weighs ~3 g. The tracker mounts adjacent to the tunable lenses in the smart eyeglasses frame. The eye tracker showed a pointing error of 1.3 degrees rms over a vertical and horizontal range of 30 degrees when tested by an observer.

Tree vibrations: Determining oscillatory properties by using infra-red marker-tracking system

A state-of-the-art infrared marker-tracking system that consists of eight cameras outfitted with infra-red optical filters and an array of infra-red light-emitting diodes as well as a set of reflective markers, is used to record the motion of a set of markers arranged along a trunk-dominated potted tree, which was pulled and released to perform free vibrations. The time-history diagrams of these markers are numerically fitted to the corresponding analytical mathematical model for each marker, in which the markers are treated as particles performing in-plane oscillations. This combination of experimental, analytical and numerical results yields the main vibration properties of the markers, i.e. the points on the tree: natural frequencies, damping ratios and the position of principal axes in two cases: for the in-leaf and out-of-leaf tree under consideration. The shape of the time history diagrams for the motion along one direction indicates the initial increase of the amplitude, and this property is found to be associated with two closed-valued natural frequencies. These two natural frequencies decreased after the removal of leaves, but stayed closed-valued. Two natural frequencies correspond to two principal axes, whose change along the height of the tree is also determined in both cases. The change of the damping ratios associated with two principal axes is also obtained: only one of them changed after the removal of leaves. Besides providing a proof of concept for the use of the high-tech marker-tracking system for obtaining certain oscillatory characteristics, this study also points out the possibilities for future work in which this system can be beneficial for investigating tree vibrations and deflections under different loads.

Blood vessel detection, localization and estimation using a smart laparoscopic grasper: a Monte Carlo study.

For centuries, surgeons have relied on their sense of touch to identify vital structures such as blood vessels in traditional open surgery. Over the past two decades, surgeons have shifted to minimally invasive surgical (MIS) approaches, including laparoscopic surgery, which include benefits such as less scarring, less risk for infection, and quicker recovery times. In fact, some surgeries such as cholecystectomies have seen more than an 80% adoption of this technique because of those benefits. However, due to the fundamental challenges associated with using laparoscopic surgery, there has been a lower adoption in more complex specialties, such as colorectal and thoracic surgery, where the field of surgery has bleeding, fat, scar tissue, and adhesions. These problems are exacerbated by complicating factors such as inflammation, cancer, chronic disease, obesity, and re-operations. Importantly, surgeons will often convert from laparoscopy to open surgery if they can no longer proceed using the minimally invasive approach because of issues described with these complicating factors, thereby negating the benefits that the patient would have seen. When the surgeon does attempt these procedures with those issues, the surgery takes on average 30 min - 1 hour longer. A new method by which surgeons can visualize structures like blood vessels could reduce the conversion rates and operating time, thereby driving a greater adoption of laparoscopic surgery in these complex procedures. Here, we show that by adding near infrared (NIR) LEDs and a linear image sensor onto the opposing jaws of the laparoscopic graspers, blood vessels that are embedded within tissues can be detected and localized efficiently, even those not visible using current imaging techniques. We show the results of Monte Carlo simulations to support our claim, including that blood vessels ranging from 2 to 6 mm and buried under up to 1 cm of tissue can be detected. We also report developing a smart grasper handheld prototype to run ex vivo experiments. The results of these experiments matched with those of the Monte Carlo simulations and the estimated blood vessel size showed a strong correlation with the actual size. This technology will be incorporated into already existing laparoscopic tools to assist surgeons during MIS procedures.