Light Source Variations Research Articles

Investigation Between Recover Behavior and Defect With Variation of Light Source in AlGaN/GaN HEMTs After Hot-Carrier Stress

<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">In this paper, a light recovery method is proposed to analyze defect concentration and energy level distribution by changing the wavelength. The AlGaN/GaN high electron mobility transistors (HEMTs) under hot carrier stress (HCS) conditions will experience a severe electrical degradation. The threshold voltage (V_th) shifts to the right, and the on current and the off current both decrease. TCAD simulations of the electric field distribution and energy bands are performed to examine the degradation behaviors under HCS on the GaN-based HEMTs. The degradation of electrical characteristics can be effectively recovered by using the illumination method in AlGaN/GaN HEMTs. In addition, the light wavelength of illumination is positively correlated with the recovery effect, which is expected to provide effective measurements and analyses for AlGaN/GaN HEMT devices, which is expected to clarify the defect energy level distribution of HEMT device degradation</i> .

Research on the Extraction Method of Test Light Source Variation Based on Directional Polarimetric Camera Data

Research on the Extraction Method of Test Light Source Variation Based on Directional Polarimetric Camera Data

Light transmittance performance of sustainable translucent self-compacting concrete

Translucent self-compacting concrete (TSCC) is an innovative energy-saving construction material. TSCC was prepared by Portland cement, limestone powder, silica fume, coarse aggregate, fine aggregate, water, superplasticizer, and plastic optical fibers (POF) to allow inward sunlight transmission. This research investigates the compressive strength as well as the natural and artificial light transmittance performance of TSCC containing different POF volume ratios and diameters. The natural light transmittance performance investigated at natural light conditions from 7 a.m. to 7 p.m. The artificial light transmittance performance was analyzed at voltage variation, light source variation, using a group of light-dependent resistors (LDRs) instead of single LDR and varying the distances from light source to specimen. TSCC was also compared with that of translucent self-compacting mortar (TSCM) and it was found that the artificial light transmittance performance of TSCC was somewhat similar to that of TSCM. The experimental study showed that although the compressive strength increased with increasing POF volume ratios and diameters, the light transmittance significantly increased in a direct quadratic relationship with increasing POF volume ratios. In this research, TSCC performs up to 21.35% and 24.7% of natural and artificial light transmittance near-cube face, respectively, which is enough lighting for commercial and residential buildings.

Method Standardization for Conducting Innate Color Preference Studies in Different Zebrafish Strains.

The zebrafish has a tetrachromatic vision that is able to distinguish ultraviolet (UV) and visible wavelengths. Recently, zebrafish color preferences have gained much attention because of the easy setup of the instrument and its usefulness to screen behavior-linked stimuli. However, several published papers dealing with zebrafish color preferences have contradicting results that underscore the importance of method standardization in this field. Different laboratories may report different results because of variations in light source, color intensity, and other parameters such as age, gender, container size, and strain of fish. In this study, we aim to standardize the color preference test in zebrafish by measuring light source position, light intensity, gender, age, animal size to space ratio, and animal strain. Our results showed that color preferences for zebrafish are affected by light position, age, strain, and social interaction of the fish, but not affected by fish gender. We validated that ethanol can significantly induce color preference alteration in zebrafish which may be related to anxiety and depression. We also explored the potential use of the optimized method to examine color preference ranking and index differences in various zebrafish strains and species, such as the tiger barb and glass catfish. In conclusion, zebrafish color preference screening is a powerful tool for high-throughput neuropharmacological applications and the standardized protocol established in this study provides a useful reference for the zebrafish research community.

Single lens logarithmic confocal distance measurement array.

This article presents a method and results based on confocal microscopy for non-contact axial distance measurement from a lens to a partially reflective surface using an array of photodetectors. The ratio of the photodetector signals is independent of the surface reflectivity and light source variations over a range of distance. By using logarithmic photodetector signals the object distance is proportional to the difference between the signals. This technique potentially allows measurement of sound produced by single living cells, or the high velocity surface shape changes in the hohlraum in laser fusion experiments.

Development of Contact Portable Microfade Tester to Assess Light Sensitivity of Collection Items

The microfade tester is used to assess fading rates of fugitive colors of collection items. The paper presents the research considerations to design a simple, less expensive and portable contact microfade tester that could serve as a screening tool for conservators. Hardware design for such an instrument is presented that includes variations in light source (xenon or LED) and measuring head (ball lens or angled holder fiber), and does not need refocusing between measurements. Performance of the portable microfade tester versions was tested on lab samples and a paper based collection item and based on the ability to rank light sensitivity relative to that of ISO Blue Wool Standards 1, 2 or 3. The results are compared to the ranking obtained with the bench instrument when testing sensitivity of the same items for the same duration. All versions of the portable hardware were found suitable for use as a screening tool to discriminate light-sensitive collection items, with performance of the portable microfade testers using an LED optimized for samples more fugitive than Blue Wool Standard 3. These portable microfade testers need not replace the bench microfade tester as the presented portable microfade tester versions are only suitable to test collection items tolerating surface contact with the instrument.

Application of white-light scanning interferometer on transparent thin-film measurement

A method to measure thin-film thickness, refractive index, and dispersion constants based on white-light interferometry is described. The thin-film property is retrieved from the Fourier amplitude of the white-light correlogram. The sources of errors in Fourier amplitude, which include the accuracy of wave number, light source variation in time, and illumination nonuniformity, are investigated. With all these errors reduced, the film thicknesses and refractive indices of four samples measured by white-light interferometry are within 1% of the ellipsometry results.

Modified correlation criterion for digital image correlation considering the effect of lighting variations in deformation measurements

The Newton-Raphson (N-R) algorithm based on the sum of squared differences (SSD) function used in the digital image correlation (DIC) may obtain unreliable results in deformation measurements because light source variation is not taken into account. Here, a modified N-R algorithm that includes the effect of light source variations on the measurement results is presented. Instead of involving the mean value and square sum of the gray value of the object, variables were employed in the proposed algorithm. Thus, we refer to it as variables-based sum of squared differences (VSSD) function. VSSD has been validated by comparing the computer generated speckle images, which indicates that it could give rise to more accurate results in calculating deformation than SSD when the surrounding light source changes. In addition, VSSD is compared with the zero-normalized sum of squared differences (ZNSSD) function that is often used to remove the light source variation. The results show that VSSD can achieve the same accuracy within in less time compared to ZNSSD.

PEMANFAATAN FOTOKATALIS TiO2 UNTUK MEREDUKSI ION TIMBAL

TiO2­ photocatalyst can be used to reduce heavy metal ions into common metal ion or metal ion with lower coordination number. This research aimed to (1) study the influence of pH on the photoreduction activity of Pb2+ion by TiO2­, (2) study the influence of hole scavenger on the photoreduction activity of Pb2+ ion by TiO2­, (3) study the influence of light source on the photoreduction activity of Pb2+ ion by TiO2­. The method used on this research is laboratory experiment consist of the making of TiO2 thin film, standard Pb2+ photoreduction with the variation of pH, standard Pb2+ photoreduction with the variation of light source. The results of Pb2+ photoreduction are analyzed by Atomic Absorption Spectroscopy. The result of the research showed that the activity of TiO2 to reduce Pb2+ can be optimum at pH 6, oxalic acid as hole scavenger and UV lamp use. The sunlight can also be used as the light source to reduce Pb2+ by TiO2 photocatalyst.

Prediction of apple fruit firmness and soluble solids content using characteristics of multispectral scattering images

Multispectral scattering is a promising technique for non-destructive sensing of multiple quality attributes of apple fruit. This research developed new, improved methods for processing and analyzing multispectral scattering profiles in order to design and build a better multispectral imaging system for real-time measurement of apple fruit firmness and soluble solids content. Spectral scattering images were obtained from Golden Delicious apples at four selected wavebands (680, 800, 900 and 950 nm) using a common-aperture multispectral imaging system. The scattering intensity and distance were corrected by incorporating the effect of individual apples’ size. A new method of correcting scattering image profiles was proposed to minimize the effect of light source variation on the calculation of scattering function parameters. Modified Gompertz and Lorentzian functions with four parameters and their variants were evaluated and compared for predicting fruit firmness and soluble solids content using multi-linear regression and cross-validation methods. The modified Gompertz function had better prediction results with a correlation coefficient ( r) of 0.896 and a standard error of prediction (SEP) of 6.50 N for firmness, and r = 0.816 and SEP = 0.92% for soluble solids content. This new function, coupled with the scattering profile correction methods, improved the multispectral scattering technique for measuring fruit quality.

Signal processing algorithm of a position sensitive detector using amplitude modulation/demodulation

The signal processing algorithm for a position sensitive detector (PSD) using an amplitude modulation/demodulation algorithm is addressed in this article. Dark currents and the external noises such as daylight and fluorescent lights are eliminated by using the amplitude modulation/demodulation and a low pass filter. The proposed amplitude modulation/demodulation method for the PSD sensor is compared with a pulse amplitude modulation method (PAM). The proposed amplitude modulation method is proved to be more accurate and robust than the PAM method by using analysis and experiments. Multiple measurements technique using one PSD sensor by the amplitude modulation/demodulation is also addressed. The power variation of light source is compensated by the normalization process using a divider.

Signal Processing Algorithm for a PSD Sensor Using an Amplitude Modulation/Demodulation

The signal processing algorithm for a PSD(Position Sensitive Detector) using an amplitude modulation/demodulation algorithm is addressed in this paper. Dark currents and the external noises such as daylight and fluorescent lights are eliminated by using the amplitude modulation/demodulation and a low pass filter. The proposed amplitude modulation/demodulation method for the PSD sensor is compared with a pulse amplitude modulation method. The proposed amplitude modulation method is proved to be more accurate and robuster than the PAM method by using analysis and experiments. Multiple measurements technique using one PSD sensor by the amplitude modulation/demodulation is also addressed. The power variation of light source is compensated by the normalization process using a divider.

635 2色蛍光法を用いた感温感圧塗料の開発

Recently, Pressure Sensitive Paint Technique (PSP) has been being developed to measure 2-dimensional pressure filed quantitatively. It has been applied to aerodynamics due to high spatial resolution and low cost. However, it cannot reduce the effect of temporal illumination light source variation and it is hardly applicable to moving test surface to be measured. Furthermore, pressure sensitive dyes generally depend strongly on temperature as well. It, therefore, has been quite difficult to apply it to thermal acoustic phenomenon, which is caused by the interaction between pressure and temperature. In the present study, 2-Color Laser Induced Fluorescence method is proposed, in which 2 dyes are used to simultaneously obtain two fluorescence-intensity images emitted at different wavelength. Hence, this can resolve some above-mentioned problems of PSP, i.e. the reduction of illumination noise and applications to moving body. Some promising dyes were investigated to apply to this technique. Consequently, PtTFPP and Pyrromethene 546 combination was found to enhance temperature sensitivity, resulting in one of the best temperature sensitive paint (TSP). In the combination of Ru(dpp) and Pyrromethene 546, its fluorescence intensity at green range becomes more blunt, so temperature-independent pressure sensitive paint can be instrumented.

Color management of reflective‐type LCDs in terms of adaptation of the human visual system to light‐source variation

Abstract—We have investigated the color management, in terms of the color adoption property of the human visual system, of a reflective‐type TFT‐LCD (R‐LCD). Since the R‐LCD depends on ambient light as the light source, it is expected that the colorimetric color on the R‐LCD must be changed if the source of the ambient light is changed. However, due to the adaptation property of the human visual system, the eye does not perceive colorimetrically corrected colors as the same color even for an R‐LCD. In this research, first, we conducted a subjective experiment to obtain the RGB code value that is required in order to display a corresponding color on the R‐LCD under varying ambient‐light conditions. The result of the experiment shows that the corresponding color of the experimental results was reasonably approximated by the color obtained by using the von Kries model. Secondly, we proposed a color‐compensating mechanism that is described as a cascaded simple 3 × 3 linear matrix. Actual colors displayed are adjusted according to the ambient light. The evaluation of the picture quality of the R‐LCD showed that the proposed model is effective.

Color Management of Reflective-type LCD in Terms of Adaptation of the Human Visual System to Light Source Variation

In connection with the color adaptation property of the human visual system, we have explored a color management of a reflective-type TFT LCD(R-LCD). Since the R-LCD works together with its ambient light as a light source, it is expected that the colorimetric color on the R-LCD must be changed if the illuminant of the ambient light is changed. However, due to the adaptation property of the human visual system, the eye does not perceive colorimetrically-corrected colors equivalently if they are on the R-LCD. In this paper, we discuss results obtained from subjective experiments which is initiated in order to understand the perceived color differences according to light source changes. Also we show how these properties of the human visual system can be modeled and calibrated in a color management unit of PC, which is applicable to the R-LCD at the practical use condition.

Color Management of Reflective-type LCD in Terms of Adaptation of the Human Visual System to Light Source Variation

Color Management of Reflective-type LCD in Terms of Adaptation of the Human Visual System to Light Source Variation

Smoothing algorithms for clip-and-paste model-based video coding

Model-based video coding has been adopted as a core experiment in the ISO MPEG-4 standard. The clip-and-paste technique for putting video objects in line is an important tool to reduce the transmission rate. To assist the clip-and-pasting method fitting into the 2-D model, we propose several smoothing algorithms for improving the quality of the reconstructed images. In this paper, the proposed smoothing algorithms can adjust the deformation of the zoom, tilt, and rotation of the object images. A luminance smoothing algorithm is also applied to compensate the light source variations. Simulation results show that the smoothing methods help to improve clip-and-paste images to achieve a satisfactory quality in visual perception.

An object-oriented model for brightness perception

An object-oriented model for the brightness perception of static images is presented. The philosophy behind the model is that the visual system aims at a brightness representation that displays object properties, and consequently is insensitive to variations in light source and changes in viewing position. The model assumes an ensemble of neural units that differ in receptive field size, i.e. identical operations are performed at a number of (spatial) scales. The brightness at each retinal position is the weighted sum of the neural activities that exist at this position in the different scales. The weighting function is such that the brightness impression is robust against variation in viewing distance. The operating characteristics of the neural units are derived from ganglion cell behaviour, and are robust against variation in light level. The model is able to unify different aspects of brightness perception, such as brightness induction and brightness assimilation. In order to gain in transparency, the approach adopted in this paper is a general one: we aim at showing how different aspects of brightness perception can be explained and unified within the model, at the expense of a less detailed description of psychophysical data.

Stochastic Photolysis: A New Method for Measuring Rates of Photosensitive Reactions

A new method is introduced for the measurement of photochemical or photobiological reaction rates. Based on linear response theory, the method uses a randomly modulated light source rather than a pulsed one, and uses cross-correlation analysis to extract the desired kinetic information. In operation, a randomly varying light source illuminates the reaction of interest, and the resulting fluctuations in reactant (or product) concentrations are monitored. Mathematical or instrumental cross correlation of the light source variations with those in component concentration then produces the familiar kinetic decay curve. Because the new method produces only minute concentration fluctuations, it can measure reaction rates near equilibrium; moreover, equilibrium position can be shifted by superimposing on the fluctuating light intensity a dc level. Also, because cross correlation is used, the method enjoys high signal-to-noise ratios. In the present study, the utility and practicability of the new technique are demonstrated through examination of the recombination kinetics of photolytically generated iodine atoms.

A fluorescence detector for high-pressure liquid chromatography

We describe a fluorescence spectrophotometer adapted with a micor quartz flow cell to record the output of modern liquid chromatographs. The optical system is double beam in that the light source variations are cancelled out by a second photo- multiplier, thus enhancing the sensitivity of the technique. The emission spectra may be scanned by stopping the flow in the chromatographic column and scanning the fluorescence detector. Many specific applications have been studied: polycyclic aromatic hydrocarbons, several vitamins, porphyrins, methyl anthranilate, etc. These are studied in natural samples and it is shown that the specificity of the fluorescence detector frequently obviates the need for sample preparation. The sensitivity available with the fluorescence detector for fluorescing compounds is often much greater than is available with variable-wavelength ultraviolet spectrophotometers. We report picogram-level detectability in real samples for many of the compounds that we have studied.