LED Array Research Articles

Robust full-pose-parameter estimation for the LED array in Fourier ptychographic microscopy.

Fourier ptychographic microscopy (FPM) can achieve quantitative phase imaging with a large space-bandwidth product by synthesizing a set of low-resolution intensity images captured under angularly varying illuminations. Determining accurate illumination angles is critical because the consistency between actual systematic parameters and those used in the recovery algorithm is essential for high-quality imaging. This paper presents a full-pose-parameter and physics-based method for calibrating illumination angles. Using a physics-based model constructed with general knowledge of the employed microscope and the brightfield-to-darkfield boundaries inside captured images, we can solve for the full-pose parameters of misplaced LED array, which consist of the distance between the sample and the LED array, two orthogonal lateral shifts, one in-plane rotation angle, and two tilt angles, to correct illumination angles precisely. The feasibility and effectiveness of the proposed method for recovering random or remarkable pose parameters have been demonstrated by both qualitative and quantitative experiments. Due to the completeness of the pose parameters, the clarity of the physical model, and the high robustness for arbitrary misalignments, our method can significantly facilitate the design, implementation, and application of concise and robust FPM platforms.

Phosphor-Free Golden Light LED Array for 5.4-Gbps Visible Light Communication Using MIMO Tomlinson-Harashima Precoding

Visible light communication (VLC) based on light-emitting diodes (LEDs) is supposed as a candidate in 6G networks because it can provide illumination and wireless communication simultaneously. As the widespread use of LEDs, the concern of light pollution and biological safety has arisen. In this paper, we propose a Si-substrate golden light LED array as a new illumination source, using high-efficacy red and yellow LEDs, which has the merits of no phosphor, no blue light, and low color temperature. Based on the golden light LED array and a 2 × 2 PIN array, a 2 × 4 high-speed multiple-input and multiple-output (MIMO) VLC system is demonstrated. Joint MIMO Tomlison-Harashima precoding (THP) scheme is first proposed and conducted for eliminating the combination of inter-symbol interference (ISI) and inter-channel interference (ICI) for carrierless amplitude and phase (CAP) modulation VLC system. Experimental results indicate that MIMO-THP performs well in interference cancellation. The Q factor is improved by 6 dB compared with conventional pure MIMO feedforward equalizer. The overall data rate exceeds 5.4 Gbit/s.

Contrast Sensitivity and Night Driving in Older People: Quantifying the Relationship Between Visual Acuity, Contrast Sensitivity, and Hazard Detection Distance in a Night-Time Driving Simulator.

Purpose(i) To assess how well contrast sensitivity (CS) predicts night-time hazard detection distance (a key component of night driving ability), in normally sighted older drivers, relative to a conventional measure of high contrast visual acuity (VA); (ii) To evaluate whether CS can be accurately quantified within a night driving simulator.Materials and MethodsParticipants were 15 (five female) ophthalmologically healthy adults, aged 55–81 years. CS was measured in a driving simulator using Landolt Cs, presented under static or dynamic driving conditions, and with or without glare. In the dynamic driving conditions, the participant was asked to simultaneously maintain a (virtual) speed of 60 km/h on a country road. In the with glare conditions, two calibrated LED arrays, moved by cable robots, simulated the trajectories and luminance characteristics of the (low beam) headlights of an approaching car. For comparison, CS was also measured clinically (with and without glare) using a Optovist I instrument (Vistec Inc., Olching, Germany). Visual acuity (VA) thresholds were also assessed at high and low contrast using the Freiburg Visual Acuity Test (FrACT) under photopic conditions. As a measure of driving performance, median hazard detection distance (MHDD) was computed, in meters, across three kinds of simulated obstacles of varying contrast.ResultsContrast sensitivity and low contrast VA were both significantly associated with driving performance (both P < 0.01), whereas conventional high contrast acuity was not (P = 0.10). There was good correlation (P < 0.01) between CS measured in the driving simulator and a conventional clinical instrument (Optovist I). As expected, CS was shown to decrease in the presence of glare, in dynamic driving conditions, and as a function of age (all P < 0.01).ConclusionContrast sensitivity and low contrast VA predict night-time hazard detection ability in a manner that conventional high contrast VA does not. Either may therefore provide a useful metric for assessing fitness to drive at night, particularly in older individuals. CS measurements can be made within a driving simulator, and the data are in good agreement with conventional clinical methods (Optovist I).

3D-printed biological habitats for the protection and persistence of &lt;em&gt;Rhizobia&lt;/em&gt; species in compacted soils

Microorganisms in soils are responsible for many ecosystem services. However, in degraded soils microbial abundance and function are limited which compromises several biologically facilitated processes. Inoculating soils with desirable microbes can help to re-instate or initiate a viable functioning microbial community. However, establishment success is reliant on the survival of the microorganism in an adverse environment. In this proof-of-concept study, artificial microbial refugia have been developed using resin and light-emitting diode array (LED) 3D printing technology. We assessed whether the artificial refugia, termed a Rhiome, would support better microbial growth in degraded soils. Soil compaction, a form of soil degradation, and Rhizobium, an important microorganism for global agriculture, were both selected as the use case application for this assessment. Different materials together with resin were assessed for their suitability as a 3D printing material and for supporting rhizobial growth. The best result was found in materials constructed with a combination of polylactic acid (PLA) resin, yeast extract and mannitol. In a soil compaction experiment with inoculation of rhizobia, the addition of Rhiome significantly increased bacterium survival in the compacted soil to a level similar to, or higher than, the rhizobial loading in non-compacted soils. Augmentation of the resin with yeast extract and mannitol increased Rhizobium growth significantly compared with the Rhiome constructed only with resin. These results indicate that the Rhiome was highly beneficial for instigating and maintaining significant rhizobia survival and growth in compacted soils. Further work, including near-to-field assessments, are required to assess Rhiome performance in a range of applications and to refine material properties relative to important context-specific performance metrics such as degradation rate. We propose the Rhiome concept as a promising asset in the toolbox for soil ecological restoration as a means of improving soil resiliency.

A Multi-LED Dome Bulb Prototype for Dense Visible Light Communication Networks

In this paper, we employ imaging-basedbeam-steering to enable multi-datastream visible light communication networks serving dense Internet-of-Things (IoT) deployments. We demonstrate a “dome bulb” transmitter that consists of a multi-LED array with a dome-shaped lens to separate each LED’s beam for better spatial reuse. Each LED has a Lambertian irradiance distribution that is collected efficiently and directed along a particular line-of-sight using a wide field-of-view lens system. At focus, the image of the LED array is projected to a distant conjugate plane, and LED beam divergence is minimized to the geometric limit. This improves spatial reuse by minimizing interference between adjacent beams but results in spotty illumination due to gaps between LEDs in the array. Moderate defocusing blurs the beams to increase illumination uniformity at the expense of increased cross-channel interference. We present a model for the bulb that correlates to the experimental results and quantify the performance of the prototype for dense IoT networks.

Strain release of formamidinium-cesium perovskite with imprint-assisted organic ammonium halide compensation for efficient and stable solar cells

Residual lattice strain in halide perovskites has been recognized as a key factor that affects device efficiency and stability of perovskite solar cells (PSCs). Here, we reveal that the escape of organic ammonium halide and their inhomogeneous distribution after thermal annealing could cause severe residual strain in intrinsic thermal stable formamidinium-cesium (FACs) perovskite films. Thus, we develop an imprint-assisted organic ammonium halide compensation strategy for residual lattice strain relaxation. We demonstrate the residual lattice strain is well-released after post-treatment, along with further perovskite grain growth/coalescence, crystallinity improvement, and defect repair. As a result, the strain-free PSCs with nickel oxide based inverted architecture exhibit a power conversion efficiency as high as 21.30% and the corresponding encapsulated devices retain 98% of their initial efficiencies at 45 °C under 1-sun equivalent white-light light-emitting diode array illumination with maximum power point tracking in the ambient environment for 1000 h.

Dose Response Effect of Photobiomodulation on Hemodynamic Responses and Glucose Levels in Men with Type 2 Diabetes: A Randomized, Crossover, Double-Blind, Sham-Controlled Trial

This study verifies the acute dose response effect of photobiomodulation (PBM) by light emitting diodes (LEDs) on hemodynamic and metabolic responses in individuals with type 2 diabetes mellitus (T2DM). Thirteen participants with T2DM (age 52 ± 7 years) received PBM by a light-emitting diode array (50 GaAIAs LEDs, 850 ± 20 nm, 75 mW per diode) on the rectus and oblique abdomen, quadriceps femoris, triceps surae, and hamstring muscle areas, bilaterally, using different energy treatments (sham, 75, 150, 300, 450, and 600 Joules) in random order with a washout of at least 15 days apart. The PBM by LEDs statistically decreased plasma glucose levels (primary outcome) in 15 min after application of the 75 and 450 J irradiation protocol, reduced blood lactate levels 15 min after application of the 75, 450, and 600 J irradiation protocol, increased cardiac output (Q˙) and cardiac index (CI) in the 1st minute after application of the 75 and 300 J irradiation protocol, and reduced Q˙ and heart rate (HR) in the 15 min after application of the 300 J and 600 J irradiation protocol, respectively. For hemodynamic variables, including Q˙, total peripheral resistance (TPR), and HR, we observed that the ideal therapeutic window ranged between 75 and 300 J, while for metabolic variables, glucose and lactate, the variation was between 450 and 600 J.

Optical and Electrical Considerations for Developing Pulsed High-Power LED for Volumetric Particle Tracking Velocimetry

Volumetric Particle Tracking Velocimetry (PTV) in volumes larger than 103 cm3 with 15 μm Air Filled Soap Bubbles (AFSB) requires a powerful pulsed laser source of few tenth of mJ pulse energy, depending on the optical arrangement of the experiment. Initial experiments in our lab with 15 μm AFSB and 1 mJ pulse energy from a 532 nm laser source showed that in order to image turbulence flow phenomena in volumes about 4x10^3 cm^3 at 1 m working distance and an f-number of 8, one would need a laser source with about 315 mJ pulse energy and 1260 W average power at 4 kHz repetition rate. Such high-power 532 nm lasers are not simple to build and are expensive and complicated to develop. By reducing the working distance and increasing the diameter of the camera aperture, the required laser power was reduced by a factor 18 to 17.5 mJ pulse energy and 70 W average power, which is still a very high power laser. As a possible alternative, we report here on the development of a collimated beam, high-power, pulsed 460 nm LED for volumetric PTV measurements of turbulence flow in a large volume seeded with AFSB p articles. We report of the optical and electrical consideration that are required in development of such an LED source. First, we combined a practical model for the output power of an LED with a model that estimates the signal level on a CMOS detector in a volumetric PTV experiment with AFSB particles. It predicted that our LED should be driven by 277 A in order to generate 1 mJ of optical pulse energy with 20 μs pulse duration. In order to avoid power drooping at high currents density in the LED, we chose an architecture of LEDs array where each LED unit of the array operates at 20 μs pulse duration, 4 kHz repetition rate and with peak current of 200 A. Each such LED will deliver 0.72 mJ pulse energy and 24 such LED units will supply the required optical density. Second, we report of the optical and electrical features of the collimated , high-power, pulsed 460 nm LED unit we built. We tested the LED in a PTV experiment where the LED operated with 0.72 mJ pulse energy, 1 kHz repetition rate and 20 A peak current. The measured signal current from a CMOS-pixel due to Mie scattering AFSB particles was in good agreement with the predicated signal level.

Van der Waals integration of GaN light-emitting diode arrays on foreign graphene films using semiconductor/graphene heterostructures

We report the van der Waals integration of micropatterned GaN light-emitting diodes (LEDs) onto foreign graphene films. GaN micro-LEDs were selectively grown on a graphene substrate using a patterned SiO2 mask, and then the whole device structure was laterally fixed by a polyimide insulator to form a united layer. After device fabrication, the LED/graphene heterostructure device was piled on the foreign graphene layers using a typical wet transfer technique of 2D crystals where the bottom graphene layer of the heterostructure was adhered to the foreign graphene only by van der Waals interactions. The transferred micro-LEDs showed well-aligned crystallographic orientations as well as reliable device performances, including strong light emissions, good rectifying behaviors of the current density–voltage curve, and good simultaneity between the electroluminescence intensity and the applied currents, ensuring reliable electrical connections and mechanical adhesions of the light-emitting layer to the foreign graphene films. Furthermore, the reliable adhesiveness allowed us to achieve device wearability, while the LEDs exhibited homogeneous light emissions under various bending conditions because of negligible external stress in the discrete micro-LEDs.

Symmetrical indoor visible light layout optimized by a modified grey wolf algorithm.

The indoor visible light communication system's LED layout and power factor affect the uniformity of the received power. To reduce the mean square error (MSE) of received power, a symmetrical optimization strategy based on the modified grey wolf optimization algorithm (mGWO) is proposed and applied in the square, rectangular, and circular rooms with different numbers of LED arrays. The received power uniformity, SNR uniformity, bit error rate, and channel capacity of the optimized layout with the proposed method are improved compared to the classical layout. The comparison results show that the mGWO can find the optimal layout efficiently.

Fast hyperspectral single-pixel imaging via frequency-division multiplexed illumination.

Hyperspectral imaging that detects 3D spectra-spatial information has been used in a wide range of applications. Among reported techniques, multiplexed spectral imaging with a single-pixel detector provides as a photon-efficient and low-cost implementation; however, the previous spectral modulation schemes are mostly complicated and sacrifice the imaging speed. Here, we propose a fast and compact hyperspectral single-pixel imaging technique based on programmable chromatic illumination. A multi-wavelength LED array modulated by independent carriers achieves stable and accurate spectral modulation up to MHz in a frequency-division multiplexed manner, hence allowing the full use of the spatial light modulation speed. Additionally, we propose a multi-channel deep convolutional autoencoder network to reconstruct hyperspectral data from highly-compressed 1D measurement. Experimental reconstructions of 12 spectral channels and 64 × 64 pixels are demonstrated for dynamic imaging at 12 fps image rate. The proposed imaging scheme is highly extensible to a wide spectrum range, and holds potential for portable spectral imagers in low-light or scattering applications.

Implementation and uniformity calibration of LED array for photodynamic therapy

Irradiance uniformity is an important parameter for a Photodynamic Therapy (PDT) device. The calibration and verification of a LED array light source based on computer vision technology were implemented and carried out. First, the correlation coefficients between the pulse width modulate value and the irradiance were calibrated. Then, the correction of the actual light center and divergence angle were solved by image processing to reduce errors from each LED lens. Finally, uniformity was optimized according to the irradiance formula of the Lambertian source. The lowest coefficients of variation of irradiance were 4.87% in a [Formula: see text] area and 3.55% in a [Formula: see text] area within the depth range of 8–12[Formula: see text]cm when the expected irradiance was 100[Formula: see text]mW/cm2. This finding indicated that the light source can achieve a more uniform illumination and provide a better therapeutic effect for the PDT of port-wine stains.

Precise and independent position correction strategy for Fourier ptychographic microscopy

Based on a commercial microscope, Fourier ptychographic microscopy (FPM) can achieve high-resolution imaging with wide field-of-view (FOV) by simply replacing traditional light source with a LED array. Since the spatial position of each LED directly determines the location of corresponding collected low-resolution image in the Fourier frequency domain, the positional error of LEDs, which is however inevitable in practical systems, would hurt reconstruction quality. To mitigate this, based on in-depth analysis of the relationship between LED’s positional error and reconstruction degradation across spatial and frequency domains, we propose a novel strategy for correcting random positional errors of LED directly in frequency domain by tackling two key challenges faced by existing position correction methods: (1) to reduce inaccuracy caused by global position error model, we utilize a per-LED frequency-domain position error model with a correlation loss function to lift correction precision; (2) to accelerate correction process, we introduce a high-magnification image, in place of the conventional intensity image that need to be iteratively updated, as a complete new reference for positional correction, enabling correction to be free from time-consuming iterative reference update process. Extensive quantitative and qualitative evaluation on both simulation and real data well demonstrate that our algorithm can greatly improve reconstruction quality with high efficiency.

Investigation of wound healing potential of photo-active curcumin-ZnO-nanoconjugates in excisional wound model

Wound healing, being a dynamic process consisting of hemostasis, inflammation, proliferation, and remodeling, involves the complicated interplay of various growth mediators and the cells associated repair system. Current wound healing therapies usually fail to completely regain skin integrity and functionality. Traditionally, curcumin is considered a potent natural wound healing agent as it possesses antibacterial, antioxidant, and anti-inflammatory properties. It is also known that zinc oxide (ZnO) nanoparticles (NPs) have photocatalytic properties, including the generation of reactive oxygen species. ZnO nanoaprticles are also Food and Drug Administration (FDA) approved as safe substances. While ZnO oxide requires illumination with ultraviolet light to become photocatalytically active, dye-sensitized ZnO can be activated by illumination with visible light. In the present study, we explored the wound healing potential of ZnO nanoparticles sensitized with curcumin (Cu+ZnO Nps) and illuminated with visible (blue) light generated by an array of high power LEDs. We studied the antibacterial effect of our conjugates by percentage reduction in bacterial growth and biofilm formation. The wound healing potential was analyzed by percentage wound contraction, biochemical parameters, and histopathological analysis of the wounded site. Additionally, angiogenesis and wound associated cytokines was evaluated by immunohistochemistry of CD31 and gene expression analysis of IL-1β, TNF-α, and MMP-9 after 16 days of post-wound treatment, respectively. Our study suggests that the therapeutic effect of Cu+ZnO NPs with LED illumination increases its wound healing potential by producing an antibacterial and anti-inflammatory effect. Moreover, the treatment strategy of using a nano formulation in combination with LED illumination further increases its efficacy. It was concluded that the anti-inflammatory and bactericidal effects of the LED illuminated Cu+ZnO Np showed accelerated wound healing with increased wound contraction, collagen deposition, angiogenesis, and re-epithelialization.

Hybrid Laser-LED Transmitter With Closed-Loop Beam-Steering Control for Indoor Optical Wireless Communication

In this paper, we demonstrate a hybrid Laser-LED transmitter module for indoor optical wireless communication with closed-loop, non-mechanical beam steering capability. The hybrid transmitter module consists of a near infrared laser diode for data communication and white LED array for illumination, combined on a diffuser surface. Dual-axis non-mechanical beam steering of the laser beam is implemented using two off-centered liquid lenses. The diffused laser beam directed towards the receiver is steered over an angular range of −7.6 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">o</sup> to 7.6 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">o</sup> (−1.7 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">o</sup> to 2.6 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">o</sup> ) along the horizontal (vertical) axes spanning −200 to 200 mm (−44 to 67 mm) at the receiver placed 1.5-meter from the transmitter. M-QAM/OFDM in combination with adaptive bit-and power-loading is utilized to achieve a total data throughput of 5.15 Gbps for the diffused laser beam with steering. Laser intensity levels as measured at the receiver plane are kept below the maximum permissible exposure limit for indoor usage across the entire beam steering range. Closed-loop beam steering is also demonstrated by scanning the transmitted laser beam horizontally, measuring the signal strength using a low bandwidth photodetector and locking the laser beam to the receiver position for data-communication. Such hybrid transmitters offer the benefit of decoupling the data communication and illumination requirements of the indoor optical link, thereby tailoring the individual light emitter's performance to specific use-case.

Full-color micro-display by heterogeneous integration of InGaN blue/green dual-wavelength and AlGaInP red LEDs.

A full-color micro-display via bonding of a InGaN blue/green dual-wavelength light-emitting diode (LED) array and a AlGaInP red LED array is demonstrated. The micro-display has a 120 µm pixel pitch, and each pixel consists of 40 µm × 120 µm red/green/blue (R/G/B) subpixels. The red LED array was integrated with the blue/green dual-wavelength LED array by Au/In flip-chip bonding to achieve full-color emission. Full-color images presented by the micro-display have high brightness and a wide color gamut. This heterogeneous integration technology using conventional LED materials shows the feasibility of a cost-effective approach for reliable high-performance full-color LED micro-displays in virtual reality (VR) and augmented reality (AR) devices.

An Alternative Experimental Method for Determination of Light Beam Attenuation Coefficient in Underwater Wireless Optical Communication

In wireless optical communication systems, the transmission of optical signals via the channel (air or water) is affected by absorption and scattering. These reduce the signal strength (attenuation) and transmission distance of the signals. In pure water, the blue-green region of the visible light gives low attenuation. Some models have been developed to characterize the underwater optical channel such as Beer Lambert’s law, Radiative Transfer equation and Monte Carlo model. In underwater optical communication, optical power meters are an invaluable tool in the determination of attenuation coefficients. However, optical power meters for underwater optical communication are very expensive. There is a need to be able to determine the attenuation in the underwater optical communication channel at a low cost, especially in the absence of underwater optical power meters. In this paper, we present an alternative low-cost experimental method of obtaining the approximate attenuation coefficient of the visible light beam in underwater optical wireless communication without the use of optical power meters. A wireless visible light communication system was set up experimentally for underwater measurements involving an oscilloscope as the only measuring device. The system uses sub-carrier frequency modulation; a white light-emitting diode array for the transmitter, and a solar panel at the receiver front end. A theoretical transmission model was developed from the experimental setup based on the line of sight method in an unbounded medium, Beer Lambert’s law, and the received sub-carrier signals; in order to provide an alternative method of determining approximately the attenuation coefficient of the underwater medium. Experiments were performed in air, clear water and in saline water. The attenuation in the air was used as a reference upon which attenuation in the clear water and the saline water was based. The saline water has a salt concentration of 6.7 g/100 mL by weight and a total dissolved solid of 86.2 ppt. The trend of the measured received sub-carrier signals showed deviation from the developed theoretical model, and the model was therefore adjusted to conform to the experimental results. From the adjusted model, the attenuation coefficient of 0.0007379 cm-1 and 0.02447 cm-1 were obtained for clear water and the saline water respectively. The method is simple, straightforward, easy to set up in a laboratory, low cost and can be applied to visible light of any wavelength.

Construction of α-MnO2 on Carbon Fibers Modified with Carbon Nanotubes for Ultrafast Flexible Supercapacitors in Ionic Liquid Electrolytes with Wide Voltage Windows.

In this study, α-MnO2 and Fe2O3 nanomaterials are prepared on a carbon fiber modified with carbon nanotubes to produce the nonbinder core–shell positive (α-MnO2@CNTs/CC) and negative (Fe2O3@CNTs/CC) electrodes that can be operated in a wide voltage window in ultrafast asymmetrical flexible supercapacitors. MnO2 and Fe2O3 have attracted wide research interests as electrode materials in energy storage applications because of the abundant natural resources, high theoretical specific capacities, environmental friendliness, and low cost. The electrochemical performance of each electrode is assessed in 1 M Na2SO4 and the energy storage properties of the supercapacitors consisting of the two composite electrodes are determined in Na2SO4 and EMImBF4 electrolytes in the 2 V and 4 V windows. The 2 V supercapacitor can withstand a large scanning rate of 5000 mV S−1 without obvious changes in the cyclic voltammetry (CV) curves, besides showing a maximum energy density of 57.29 Wh kg−1 at a power density of 833.35 W kg−1. Furthermore, the supercapacitor retains 87.06% of the capacity after 20,000 galvanostatic charging and discharging (GCD) cycles. The 4 V flexible supercapacitor shows a discharging time of 1260 s and specific capacitance of 124.8 F g−1 at a current of 0.5 mA and retains 87.77% of the initial specific capacitance after 5000 GCD cycles. The mechanical robustness and practicality are demonstrated by physical bending and the powering of LED arrays. In addition, the contributions of the active materials to the capacitive properties and the underlying mechanisms are explored and discussed

Microscopy is better in color: development of a streamlined spectral light path for real-time multiplex fluorescence microscopy.

Spectroscopic image data has provided molecular discrimination for numerous fields including: remote sensing, food safety and biomedical imaging. Despite the various technologies for acquiring spectral data, there remains a trade-off when acquiring data. Typically, spectral imaging either requires long acquisition times to collect an image stack with high spectral specificity or acquisition times are shortened at the expense of fewer spectral bands or reduced spatial sampling. Hence, new spectral imaging microscope platforms are needed to help mitigate these limitations. Fluorescence excitation-scanning spectral imaging is one such new technology, which allows more of the emitted signal to be detected than comparable emission-scanning spectral imaging systems. Here, we have developed a new optical geometry that provides spectral illumination for use in excitation-scanning spectral imaging microscope systems. This was accomplished using a wavelength-specific LED array to acquire spectral image data. Feasibility of the LED-based spectral illuminator was evaluated through simulation and benchtop testing and assessment of imaging performance when integrated with a widefield fluorescence microscope. Ray tracing simulations (TracePro) were used to determine optimal optical component selection and geometry. Spectral imaging feasibility was evaluated using a series of 6-label fluorescent slides. The LED-based system response was compared to a previously tested thin-film tunable filter (TFTF)-based system. Spectral unmixing successfully discriminated all fluorescent components in spectral image data acquired from both the LED and TFTF systems. Therefore, the LED-based spectral illuminator provided spectral image data sets with comparable information content so as to allow identification of each fluorescent component. These results provide proof-of-principle demonstration of the ability to combine output from many discrete wavelength LED sources using a double-mirror (Cassegrain style) optical configuration that can be further modified to allow for high speed, video-rate spectral image acquisition. Real-time spectral fluorescence microscopy would allow monitoring of rapid cell signaling processes (i.e., Ca2+ and other second messenger signaling) and has potential to be translated to clinical imaging platforms.

Smart vector-inspired optical vision guiding method for autonomous underwater vehicle docking and formation.

A smart vector-inspired optical vision guiding (VIOVG) method for autonomous underwater vehicle (AUV) docking and formation is proposed. Unlike traditional optical guiding methods based on LED arrays, the method is inspired by a vector, and uses four laser diodes to form a wing-light pattern to realize smart optical guiding for AUVs. Due to the light scattering effect from water, the four laser diodes can emit four bright and slim laser beams in water, which can be captured by underwater cameras. The intersections of the laser beams form wing-lights as markers for AUV distance and pose estimation. The wing-light pattern is easily tuned and extended by changing the propagation direction and the power of the laser beams beyond the limitation of the physical size of the AUV or docking station. The simulations and experiments show that the proposed method can achieve high precision positioning. A relative distance error of 3.35% is achieved in a positioning experiment at ∼10 m. It has great potential for AUV docking and formation, especially for small AUVs.