Multiple Light Sources Research Articles

Proposal of Light Curtain System Using a Hemisphere Mirror with Multiple Frequency-modulated Light Sources

Light curtains are used as a method to detect intruders at a lot of places now. However, in practice, they need to adjust the light detection element accurately in order to receive the irradiating laser light. We propose a new type of Safety Light Curtain System that uses a hemisphere mirror and LEDs in this research. The hemisphere mirror can reflect light rays surrounding of 120◦ in the vertical direction and 360◦ in horizontal direction[1]. When an LED is placed at a position that is higher than the hemisphere mirror, it is possible to reflect the light with the hemisphere mirror even if the LED is arbitrarily set up. When an intruder passes between the LED and the hemisphere mirror, the light of LED is intercepted and the output voltage of the light detecting element decreases. It can be judged by the threshold output voltage whether an intruder passed between LED and the hemisphere mirror or not. Compared with recent market products, our system has the benefits of low-cost, simple configuration, low radiation, and high efficiency.

Design and validation of a fiber optic point probe instrument for therapy guidance and monitoring

Optical techniques for tissue diagnostics currently are experiencing tremendous growth in biomedical applications, mainly due to their noninvasive, inexpensive, and real-time functionality. Here, we demonstrate a hand-held fiber optic probe instrument based on fluorescence/reflectance spectroscopy for precise tumor delineation. It is mainly aimed for brain tumor resection guidance with clinical adaptation to minimize the disruption of the standard surgical workflow and is meant as a complement to the state-of-the-art fluorescence surgical microscopy technique. Multiple light sources with fast pulse modulation and detection enable precise quantification of protoporphyrin IX (PpIX), tissue optical properties, and ambient light suppression. Laboratory measurements show the system is insensitive to strong ambient light. Validation measurements of tissue phantoms using nonlinear least squares support vector machines (LS-SVM) regression analysis demonstrate an error of <5% for PpIX concentration ranging from 400 to 1000 nM, even in the presence of large variations in phantom optical properties. The mean error is 3% for reduced scattering coefficient and 5% for blood concentration. Diagnostic precision of 100% was obtained by LS-SVM classification for in vivo skin tumors with topically applied 5-aminolevulinic acid during photodynamic therapy. The probe could easily be generalized to other tissue types and fluorophores for therapy guidance and monitoring.

Evaluation of the orientation distribution of fibers from reflection images of fibrous samples

We consider illumination systems and mathematical algorithms for determination of the anisotropy and topographical features of an illuminated surface from its reflection images. As a particular example we study determination of the fiber orientation of paper surface. We also consider illumination systems with multiple light sources, and introduce optimization algorithms that exploit different spectral bands of these light sources. We show that a system of three light sources, e.g., a blue, green and red LED placed in a regular triangular form, efficiently prevents distortion of the above features. It is also easy to implement in applications, e.g., of the paper industry. We furthermore show that a pentagonal illumination system would be even better. However, in this case a five-colour photographic system and the corresponding light sources would be needed.

Estimation of 3D Geometry Using Multi-View and Structured Circular Light System

This paper proposes an approach to multiple view-projection systems planning for a 3D object reconstruction in a practical settings. A I/O system theoretic is adopted and, viewpoints and light sources which are located at different positions are respectively the output and the input. The system identification is defined by a relationship between input and output. Structured circular light patterns are generated by multiple light sources. The proposed approach may be applied to both multiple inputs(projectors)-viewpoints (MPV) or single inputviewpoint (SPV) systems. This contribution is chiefly for an approximate reconstruction sufficient to characterize / clarify a target object rather than a perfect 3D reconstruction. To that end, we propose a development of an efficient 3D system identification frameworks based around an efficient 3D camera system we have developed in the laboratory. We show that these are closely related to the geometric information of an object, and with minimal prior information, an efficient MPV system is achieved.

ミカンキイロアザミウマの走光性に関する作用スペクトルと複眼分光感度との関係

We measured the phototactic behavior of the western flower thrips, Frankliniella occidentalis (Pergande) under the LED light of various spectral content and intensity. The light intensity required to elicit a 50% behavioral response to the stimulus yielded the action spectrum of the phototactic behavior. The action spectrum peaks at 525 and 355 nm, between 355 to 660 nm. This profile reasonably fits the spectral sensitivity of the compound eye as determined by the electroretinographic method. In a choice experiment where the insects were subjected to select either 355 nm or 525 nm of equal photon flux, they preferred 355 nm to 525 nm, indicating that the insects prefer ultraviolet (UV) radiation under the condition of multiple light sources.

Improving Edge based Color Constancy using Grid based Sampling

Color constancy refers to stable psychological tendency in perception even the lighting circumstances changed and it plays an important role in many computer vision applications. Color constancy is the ability to measure the impact of light onto a digital image independent of the color of the light source. Many color constancy algorithms for estimating the color of the light source, are developed so far but all the existing algorithm are based on single light source i.e. they consider that an image is affected by only one light source or single uniform illumination, which is not the case every time, because an image may be affected with more than one illuminations. The illusion of single light source is now violated by multiple sources of light. In this paper, we will discuss a new method which considers that an image is affected by multiple sources of light, without any clue about the color of the light sources. Grid based sampling technique along with Grey Edge algorithm is used to estimate the color of multiple light sources. The use of Bilateral Filter after applying color correction is giving most promising results and it has provided the consistency of this algorithm over different types of images taken from different datasets. Experimental and visual results show that the proposed method achieves much better results than existing methods for color constancy. The qualitative results are tested over some well known parameters i.e. Median Angular Error (MAE), Peak Signal to Noise Ratio (PSNR) etc.

Shadow moiré technology based fast method for the measurement of surface topography

We present a fast phase-shifting shadow moiré device for surface topography measurement. In our setup, multiple light sources located at different positions are controlled to illuminate the grating sequentially. Therefore, the phase shift across the field of view shadow moiré is introduced by changing the distance between the light source and the camera. Thanks to the necessity for mechanical movement being omitted here, the proposed setup can capture the phase-shifting fringe patterns at a high speed. However, affected by the bias modulation and amplitude modulation of the captured fringe patterns, the phase of interest cannot be demodulated by the standard phase-shifting algorithm directly. Thus the principal component analysis (PCA) demodulation approach is used to extract the wrapped phase map. In addition, we develop an iterative procedure to reduce the detuning error introduced by the PCA algorithm. The proposed method implements a fast way to determine the topography of a surface through a simple experimental setup. It is applied to obtain an external surface of a specimen. Both the simulation results and the experimental results show the validity of the proposed technique.

Miniaturized amorphous-silicon based chemical imaging sensor system using a mini-projector as a simplified light-addressable scanning source

This paper reports the development of a chemical imaging sensor configuration addressing two important issues of imaging systems: the flexibility of the scanning technique and the resolution of the image. In this set-up, a commercial pico-projector in combination with an objective lens is placed directly below the sensor plate and is utilized as a light-addressing source to scan the sensor surface. The pico-projector provides the computer software interface that enables the user to generate a programmable light beam with control over its size, shape, color, movement, and even modulation frequency. This approach eliminates the requirement of complicated mechanics and optics in conventional scanning techniques based on linear X–Y stages or multiple light sources and effectively miniaturizes the set-up. Furthermore, no additional control unit is required to access the internal control of digital micro-mirror, thus simplifying the scanning set-up. An amorphous-silicon-based thin-film light-addressable potentiometric sensor (LAPS) structure is used as a sensor chip. At the present stage, pH sensitivity close to the ideal Nernstian value and a visibility of patterns of 25μm chemical image were exhibited. Finally, the chemical imaging of a complex pattern was successfully demonstrated using this simple low-cost, miniaturized system.

Photodynamic Therapy (PDT) Utilizing Multiple Light Sources Significantly Improves Clinical Efficacy and Subject Satisfaction with a Review of PDT Mechanisms of Action

Introduction: Many topically applied devices and medicaments have been developed to give hope to people who want to reduce the signs of visible aging. All modalities have benefits and risks, and no single modality produces complete resolution of photoaging. Although approved by the US Food and Drug Administration for treatment of epithelial neoplasia, photodynamic therapy (PDT) is also reported to produce significant benefits in reducing photoaging. The goal of this study was to determine if clinical response and subject satisfaction can be improved for PDT while reducing downtime and increasing activation of the photosensitizer. Materials and Methods: In a regimen administered monthly for 3 treatments, 14 subjects participated in a prospective intervention pilot trial using an 830 nm light-emitting diode (LED), a 540 nm advanced fluorescence technology laser, a 570 nm advanced fluorescence technology laser, and a 633 nm LED. The photoactivation phase was initiated with the 830 nm LED 10 minutes after application of 20% 5-aminolevulinic acid, followed by each modality in listed order. Baseline global extrinsic aging scores were compared with scores 1 month after the final treatment. Subject satisfaction scores were also obtained 1 month after the final treatment. Results: Twelve subjects completed this trial. The global extrinsic aging score improved from a baseline of 3.3 to 1.0. Of these 12 subjects, 10 (84%) indicated that they were satisfied or very satisfied with the results 1 month after completion of the treatment. Conclusions: This photodynamic therapy regimen is very effective while being better tolerated and involving less downtime. The treatment can also be completed in a shorter time than regimens requiring a longer incubation time.

Calcium Imaging and Optical Manipulation of Neuronal Activity in Axolotl using a LED-Based Microscope

Here we introduce a novel fluorescence microscope concept which expands the application of functional fluorescence imaging and further enables optical manipulation of biological samples. Taking advantage of the LED technique allows a space saving housing of multiple light sources and illumination at various wavelengths. Furthermore, the microscope provides an optical separation into two independently controllable excitation pathways enabling a simultaneous illumination of different regions which are adjustable in size. Image detection is realized via a super resolution high speed camera that allows high resolution image capturing (2560x2160) at rates up to 100 Hz. Moreover, we implemented a voice-coil driven high NA objective to ensure z-movement at maximum speed and precision. The multiple LED arrangement and the separation of excitation pathways therefore facilitate the usage of multiple imaging approaches at the same time.To test the performance of the microscope we used in vitro whole head preparations of Ambystoma mexicanum tadpoles. This preparation allows studying neuronal systems with all sensory pathways intact and can be maintained up to one week. Thus, we were able to use calcium imaging to record sensory evoked neuronal responses of central vestibular neurons elicited by electric stimulation of specific semicircular canals. Further, to quantify the glutamate uncaging efficiency we calculated the required light intensity and duration to optically evoke action potentials by patching those neurons. Finally, we could show that by means of spatially separating calcium imaging and glutamate uncaging we were able to manipulate ipsilateral semicircular canal evoked calcium responses by optically activating contralateral inhibitory/excitatory pathways.

Comparison of SHR Mode IPL System with Alexandrite and Nd: YAG Lasers For Leg Hair Reduction.

Multiple lasers and light sources are currently available for hair removal and many studies comparing efficacy and safety exist. SHR mode IPL is a technique that gives the total energy in divided doses with fewer side effects. We compared a SHR mode IPL system with alexandrite and Nd: YAG lasers for leg hair reduction. Twenty-five female participants with skin types II-IV, underwent treatment of unwanted hair on the cruris. Three selected areas were randomly treated with the SHR mode IPL system, Alexandrite laser and Nd: YAG laser in three sessions. Hair reduction was evaluated with digital photography by a blinded assessor every 6 weeks and 6 months after the last session. Pain severity, side effects and patient satisfaction analysis were also investigated. Twenty-one participants completed the trial. The mean hair reductions in 6 weeks after the last treatment were 50% for the IPL system, 53% for Alexandrite and 39% for the Nd: YAG lasers. However after 6 months; 40%, 49% and 34% hair reduction was observed, respectively. The Alexandrite laser was the least painful system. Although there is no obvious advantage of one laser system over the others in terms of treatment outcome, the Alexandrite laser is still the most efficient and reliable way of hair removal in fair skinned individuals.

Structure-Aware Lighting Design for Volume Visualization.

Lighting design is a complex, but fundamental, problem in many fields. In volume visualization, direct volume rendering generates an informative image without external lighting, as each voxel itself emits radiance. However, external lighting further improves the shape and detail perception of features, and it also determines the effectiveness of the communication of feature information. The human visual system is highly effective in extracting structural information from images, and to assist it further, this paper presents an approach to structure-aware automatic lighting design by measuring the structural changes between the images with and without external lighting. Given a transfer function and a viewpoint, the optimal lighting parameters are those that provide the greatest enhancement to structural information - the shape and detail information of features are conveyed most clearly by the optimal lighting parameters. Besides lighting goodness, the proposed metric can also be used to evaluate lighting similarity and stability between two sets of lighting parameters. Lighting similarity can be used to optimize the selection of multiple light sources so that different light sources can reveal distinct structural information. Our experiments with several volume data sets demonstrate the effectiveness of the structure-aware lighting design approach. It is well suited to use by novices as it requires little technical understanding of the rendering parameters associated with direct volume rendering.

Modeling the light distribution in airlift photobioreactors under simultaneous external and internal illumination using the two-flux model

A simultaneous external and internal illumination method is proposed for cylindrical airlift photobioreactors in this paper, in which multiple light sources are placed around the downcomer region, to achieve a more homogeneous light distribution. Internal light sources are mounted near the wall of the draft tube and external light sources near the wall of the photobioreactor. The light distribution in an airlift photobioreactor under simultaneous external and internal illumination (APBR-SEII) with various biomass concentrations and radii is investigated using the two-flux model. This model is able to obtain reasonable prediction compared with the simulation of more rigorous DO models, and is suitable for real-time control of microalgae cultivation in photobioreactors. Light attenuation profiles are compared with those of only externally illuminated airlift photobioreactors (APBR-EI), showing that the new illumination method can increase the size of the illuminated zone in photobioreactors and enable a more uniform light distribution in the downcomer region. The calculation results also show that the annular distance of the downcomer region (ΔR) is more critical than the radius of the photobioreactor (R) to light distribution and therefore the design of photobioreactors. Asymmetry of light distribution in an airlift photobioreactor with the same radiation flux on the two walls is pronounced for low biomass concentrations and small radii.

User-guided white balance for mixed lighting conditions

Proper white balance is essential in photographs to eliminate color casts due to illumination. The single-light case is hard to solve automatically but relatively easy for humans. Unfortunately, many scenes contain multiple light sources such as an indoor scene with a window, or when a flash is used in a tungsten-lit room. The light color can then vary on a per-pixel basis and the problem becomes challenging at best, even with advanced image editing tools. We propose a solution to the ill-posed mixed light white balance problem, based on user guidance. Users scribble on a few regions that should have the same color, indicate one or more regions of neutral color, and select regions where the current color looks correct. We first expand the provided scribble groups to more regions using pixel similarity and a robust voting scheme. We formulate the spatially varying white balance problem as a sparse data interpolation problem in which the user scribbles and their extensions form constraints. We demonstrate that our approach can produce satisfying results on a variety of scenes with intuitive scribbles and without any knowledge about the lights.

Multiwavelength-integrated local model fitting method for interferometric surface profiling

The local model fitting (LMF) method is a useful single-shot surface profiling algorithm that features fast measurement speed and robustness against vibration. However, the measurement range of the LMF method (i.e., measurable height difference between two neighboring pixels) is limited up to a quarter of the light source wavelength. To cope with this problem, the multiwavelength-matched LMF(MM-LMF) method was proposed, where the plain LMF method is first applied individually to interference images obtained from multiple light sources with different wavelengths, and then the LMF solutions are matched to obtain a range-extended solution. Although the MM-LMF method was shown to provide high measurement accuracy under moderate noise, phase unwrapping errors can occur if individual LMF solutions are erroneous. In this paper, we propose the multiwavelength-integrated LMF (MI-LMF) method, which directly computes a range-extended solution from multiple interference images in an integrated way. The effectiveness of the proposed MI-LMF method is demonstrated through simulations and actual experiments.

Pulsed Dye Laser Does Not Seem as Effective as Red Light in Basal Cell Carcinoma Mal-Pdt: A Small Pilot Study

Multiple light sources can be used for photodynamic therapy (PDT) with good results, but there are few comparative studies. This study compares the efficacy of treatment of basal cell carcinoma with PDT and two light sources, the non-coherent red light and pulsed dye laser 595 nm. In this small pilot study red light is more effective, but many more studies are needed to draw definitive conclusions.

Multiple Intensity Differentiation for 3-D Surface Reconstruction With Mono-Vision Infrared Proximity Array Sensor

3-D depth sensor technologies, as manifested in several consumers' electronics products, have potential for a technological breakthrough in various application areas such as industrial, medical, and outdoor vision system. Depth sensing of human body motions can promote intuitive gesture inputs for natural HMI (Human Machine Interface) as well as HRI (Human Robot Interaction) to the next level. In today's industry, the dominant trends in 3-D depth sensing are shifting from the traditional laser based scanning or TOF (Time of Flight) depth sensing to the intensity based Infrared 3-D depth mechanism. For example, Microsoft Kinect is a manifestation of such demands for more affordable and real time 3-D depth sensing. In this paper, we investigate currently available 3-D sensor technologies for comparison followed by the presentations of the results in novel mono-vision based 3-D surface sensing and visualization study. The novel method presented in this paper is to calculate the 3-D depth and the surface angle of an object at the same time. The proposed technology is to generate high quality 3-D surfaces with a pure intensity matrix from multiple light sources. The enabling technology is the multiple intensity differentiation method, which is the main focus of study in the paper.

사용자 요구조도 보장 에너지 효율적 LED 조명 제어 기법

Due to many recent activities on enforcement of the intensified environmental regulation such as the policies of curbing the greenhouse gas and the Restriction of Hazardous Substances (RoHS), the usage of Light emitting diode (LED) has been rapidly increased and energy efficient management of LED light system is regarded as an important technology to enhance the energy efficiency. In this paper, we propose an energy-efficient control scheme of LED light, being composed of multiple light sources. The proposed scheme controls the intensity of LED light source to minimize the total intensity while providing the quality of lighting service. The intensity of light is assumed to be proportional to power consumption, thus the objective is to minimize the total power consumption. A linear programming problem is formulated to find the optimal intensity of each light source and procedure to apply the proposed scheme in the real system is suggested. The performance evaluation results elucidate that the proposed scheme achieves over 20% improvement in power consumption of light intensity in comparison with the conventional dimming control scheme.

Color Constancy for Multiple Light Sources

Color constancy algorithms are generally based on the simplifying assumption that the spectral distribution of a light source is uniform across scenes. However, in reality, this assumption is often violated due to the presence of multiple light sources. In this paper, we will address more realistic scenarios where the uniform light-source assumption is too restrictive. First, a methodology is proposed to extend existing algorithms by applying color constancy locally to image patches, rather than globally to the entire image. After local (patch-based) illuminant estimation, these estimates are combined into more robust estimations, and a local correction is applied based on a modified diagonal model. Quantitative and qualitative experiments on spectral and real images show that the proposed methodology reduces the influence of two light sources simultaneously present in one scene. If the chromatic difference between these two illuminants is more than 1°, the proposed framework outperforms algorithms based on the uniform light-source assumption (with error-reduction up to approximately 30%). Otherwise, when the chromatic difference is less than 1° and the scene can be considered to contain one (approximately) uniform light source, the performance of the proposed method framework is similar to global color constancy methods.

Simultaneous Second Harmonic Generation of Multiple Wavelength Laser Outputs for Medical Sensing

Multiple wavelength light sources in the medical spectral window region are useful for various medical sensing applications in tissue by distinguishing the absorption and scattering coefficients optically. We propose a simultaneous second harmonic generation of multiple wavelength fiber laser output using parallel channels of periodically-poled lithium niobate (PPLN) waveguides. High intensity dual wavelength lasing output is experimentally realized with two tunable fiber Bragg gratings of 1,547.20 nm and 1,554.48 nm for the efficient conversion to the half wavelengths, 773.60 nm and 777.24 nm, by using two parallel PPLN channels. Compared with a conventional dual second harmonic generation (SHG) configuration based on two different input wavelengths from each independent light source, this method has a relatively higher efficiency to align the input light beam into the adjacent parallel PPLN channels simultaneously. The use of fiber lasers offers several advantages since they are relatively inexpensive, provide high power in excess of tens of watts, are widely tunable, and can produce pulses from milliseconds to femtoseconds.