Spectrum Of Light Source Research Articles

Effects of light source spectrum and background colour on the perception of paintings

This paper presents an experiment on the effect of light on the perception of paintings. The experiment was performed in a test-room where a typical museum exhibition set-up was simulated. Two different paintings were shown to 44 participants, under different light scenes obtained by using tuneable LED (Light Emitting Diode) wallwashers. To set the light scenes, the following parameters were modified: correlated colour temperature of the lighting, illuminance on the painting and the colour of the background wall. Participants answered a questionnaire to assess the perception of the paintings’ colours, the lighting conditions and the pleasantness of the exhibition set-up. The results demonstrated that illuminance is the parameter mainly affecting perception, for both paintings. However, correlated colour temperature and wall colour, as well as the combination of the three different considered parameters, can more or less influence perception depending on the chromatic composition of the painting.

LRT Digest 3: New colour metrics and their use

Executive summary The two metrics traditionally used to quantify the colour properties of light sources are the correlated colour temperature and the CIE General Colour Rendering Index. With the arrival of LEDs as a major light source questions began to be asked about the merits of both of these metrics. The question asked about correlated colour temperature was how far should the chromaticity of a light source be allowed to depart from the Planckian locus before the light emitted could no longer be said to be white? A tolerance to such a departure ( Duv) already existed but now gathered much more attention. The questions asked about the CIE General Colour Rendering Index were more searching. The limitations of the CIE General Colour Rendering Index were explored and, as a result, several alternative approaches to quantifying the colour rendition properties of light sources were proposed. The most comprehensive approach was produced by the Illuminating Engineering Society of North America, first in its Technical Memorandum IES TM-30-15 and more recently in its revision, Technical Memorandum ANSI/IES TM-30-18, which has been accepted as an American Standard. Both these documents describe a system that contains two high-level summary metrics: One for the average fidelity, i.e. how accurately a test light source renders 99 colour samples relative to how they are rendered under a reference illuminant, and the other for the average colourfulness, i.e. the overall increase or decrease in colourfulness of the same colour samples under the same test light source compared to the same reference illuminant. Associated with these overall average metrics are a number of more detailed metrics and graphical presentations. These aim to quantify and illustrate the variations in fidelity and the direction and magnitude of the shifts in chroma and hue around the hue circle. Compared to the CIE General Colour Rendering Index or the CIE Fidelity Index, a metric published by the CIE in 2017, ANSI/IES TM-30-18 provides a more comprehensive approach to quantifying and understanding the effects of light source spectrum on the perception of colour. Unfortunately, the new colour metrics described in IES TM-30-15 and ANSI/IES TM-30-18 have not yet been accepted by the CIE. Despite this, some light source manufacturers have started to provide information on their products expressed in terms of the ANSI/IES TM-30-18 colour metrics and designers are beginning to request them. The expectation is that, eventually, the ANSI/IES TM-30-18 metrics will be adopted by many countries and authorities, because they provide a much more comprehensive description of the colour properties of a light source than the CIE General Colour Rendering Index. This will be of value to light source manufacturers and lighting designers as well as those who prepare lighting codes and guides. It is expected that in the future the minimum set of data considered acceptable for describing the colour properties of a light source are likely to be the correlated colour temperature and the associated Duv value, the CIE Fidelity Index or the matching ANSI/IES TM-30-18 Fidelity Index, together with the ANSI/IES TM-30-18 Gamut Index and the ANSI/IES TM-30-18 Colour Vector Graphic.

Off-resonant photoacoustic spectroscopy for analysis of multicomponent gas mixtures at high concentrations using broadband vibrational overtones of individual gas species.

The broadband photoacoustic spectroscopy (PAS) technique is proposed and demonstrated for measurement of CH4, CO2, and H2O vapor in the 1.6 to 2.0μm wavelength region. The wide spectrum of a supercontinuum light source is used to cover broadband absorption bands of multiple gas species. This sensor works in the off-resonant frequency of the designed photoacoustic cell and exhibits a wide concentration measurement range of parts per billion by volume (ppb-v) to 100%. The PAS sensor is further tested in real time by measuring the concentration of CO2, CH4, and H2O vapor in biogas plants.

Low-cost optical fiber temperature-sensing system employing optical transceivers for Ethernet and long-period fiber grating.

Optical fiber sensors have numerous advantages over electrical sensors. However, in some cases, sensing systems based on optical fiber sensors are inferior to electrical sensors in terms of cost because expensive instruments are required. Therefore, cost-effective options must be developed. Here, inexpensive optical transceivers (OTRs) for Ethernet were used instead of a broadband light source and optical spectrum analyzer, and a CO2 laser-induced long-period fiber grating (LPFG) was used as a temperature sensor. The sensing system was implemented introducing OTRs and LPFG in an experimental internet protocol (IP) over Ethernet. The results showed that a low-cost sensing system can estimate the ambient temperature of the LPFG based on the no-reply rate for the internet control message protocol echo request. Regarding the sensing performance, the measurable range was ∼100°C with ±4.5°C errors.

Novel protocol of hyperspectral data acquisition by means of an acousto-optical tunable filter with synthesized transmission function

A new protocol of hyperspectral data acquisition with an acousto-optical tunable filter is proposed and tested experimentally. Correction for the illumination source spectrum and regular spectral sensitivity factors is embedded in the data acquisition routine. The protocol is based on the adaptive electronic setting of the filter transmission passband inversely proportional to the power spectrum of the light source. Spectral equalization of the light source spectrum in a hyperspectral imaging spectrometer is demonstrated with 3% standard deviation over the bandwidth 465-820nm. The broadening of the point-spread function does not exceed 20% at fourfold bandwidth extension owing to a confocal configuration of the spectrometer.

Response to White Light Emitting Diode Aviation Signal Lights Varying in Correlated Color Temperature

Airfield lighting for runways and taxiways is currently undergoing a transition from filament-based incandescent sources to light emitting diodes (LEDs). Although models to assess the relative brightness, discomfort glare, and peripheral detectability of signal lights such as those used for aviation exist, their applicability to white LED airfield lighting has not been verified independently. A series of three experiments was conducted to compare white LED sources, having correlated color temperatures of 2,700 K and 5,900 K, in terms of their relative brightness, discomfort glare, and peripheral detectability. The perceived brightness and discomfort glare from the light sources closely matched predictions from the published models, demonstrating the usefulness of these models at characterizing these responses in airfield lighting. In the case of peripheral detectability, there was little to no difference in how quickly the two LEDs were perceived at low light levels, suggesting that there is no need to consider spectral differences between light source spectra for this response when the intensities are similar to those used in the present study.

Reflection Phase Microscopy by Successive Accumulation of Interferograms

Imaging three-dimensional (3-D) structures of biological specimens without exogenous contrast agents is desired in biological and medical science in order not to disturb the physiological status of the living samples. Reflection phase microscopy based on interferometric detection has been useful for the label-free observation of such samples. However, the achievement of optical sectioning has been mainly based on the time gating set by the broad spectra of light sources. Here we propose wide-field reflection phase microscopy using a light source of narrow bandwidth, which is yet capable of achieving the optical sectioning sufficient for 3-D imaging of biological specimens. The depth selectivity is achieved by successive accumulation of interferograms (SAI) produced by synchronous angular scanning of a plane wave on both the sample and reference planes. This intensity-based cumulative process eventually results in a coherent addition of object fields that quickly attenuates the out-of-focus information alo...

THE EVALUATION METHOD FOR THE EFFICIENCY OF PHOTOSYNTHESIS DEPENDING ON THE COMPOSITION AND INTENSITY OF LIGHT ON THE EXAMPLE OF CUCUMIS SATIVUS L.

The article calculates potentially effective for photobiological processes density light fluxes arc tube sodium lamps (HPS) and 250 watt Light Emitting Diode (LED) lamps 46 watts. The concept of light utilization for photobiological reactions is proposed to evaluate the energy component of the light spectrum suitable for optimal activation of plant photoreceptor systems that control the shaping process by changing the orientation of the biological system in space at an early stage of development in order to achieve maximum photosynthetic response. The calculations used the experimentally obtained values of the absorption coefficients of the leaf ofCucumis sativus L. Based on the data on the linear dimensions of the leaf of the plant and the dependence of the absorption spectrum on the age of the plant, as well as the action spectra of photobiological reactions (photosynthesis, dissipation of excess energy as heat, phototropic reaction, chlorophyll, photomorphogenesis) and emission spectra of light sources, we have calculated the mass of accumulated carbohydrates at an early stage of developmentCucumis sativus L. In order to test the reliability methods of analytical evaluation, an experimental study of the effect of radiation data illuminators was carried out. For HPS 250, the weight of carbohydrates and the dry weight of the plant were0.24 g and0.20 g, respectively, for LED 46, the weight of carbohydrates and dry weight of the plant were0.05 g and0.05 g, respectively. The proposed system for assessing the efficiency of the spectrum and the intensity of radiation by the linear parameters of a plant is an intelligent basis for creating an energy-efficient system for automatically controlling LED lighting of a greenhouse with feedback on a measured parameter of a plant.

一种表征EDFA放大宽谱光源的噪声估测方法

一种表征EDFA放大宽谱光源的噪声估测方法

Photocatalytic techniques to prevent and combat healthcare associated infections

An ever-increasing rate of morbidity and mortality caused by healthcare associated infections is reported annually. Air circulation mediates contact with microbial contaminated aerosols and represents a major risk of transmitting healthcare associated infections. We propose a revolutionary technique for the protection of interior surfaces based on a photocatalytic composition with doped TiO2 or ZnO type semiconductor metal oxides which exert antimicrobial effect. In principle, there is an activation of the photocatalytic coating with light from the normal lighting apparatus, which may incorporate one or more sources of photocatalytic excitation light. By studying the air circulation in the hospital, it is possible to design light fixtures with specific design of light distribution, in order to perform the disinfection of the air and surfaces and to amplify the antimicrobial effect. The disinfection process does not affect patients or healthcare professionals, it can be done in their presence and has a continuous, controllable effect. Photocatalytic paint in combination with a prototype luminaire with a precise spectrum light sources, light output and a light intensity distribution curve relative to the shape and dimensions of the rooms, shows that the proposed method may represent a successful alternative to classical methods of disinfection in hospitals. This technique can also be used in other areas of interest.

Spectral Optimization to Minimize Light Absorbed by Artwork

ABSTRACTLight is needed to appreciate artwork, but visible radiation causes damage by photochemical action. Photons trigger photochemical action only when they are absorbed by the object. Damage to sensitive materials can be reduced by optimizing the spectrum of a light source to the reflectance factor of a museum artifact. Absorption minimization approaches can be utilized to quantify and optimize typically conflicting parameters, such as damage due to light absorption, color quality of artwork, and energy consumption. In this project, seven narrowband light emitting diodes (LEDs) are optimized using a multi-objective genetic algorithm to reduce light absorption and energy consumption, while maintaining the color appearance of five paints (blue, green, yellow, orange, red). Results indicate that optimized test spectra can reduce light absorption between 18% and 48%, without causing perceptible color or hue shifts in the paintings. Parallel to absorption, energy consumption is almost halved for all of the paints (between 42% and 48%). Optimizing the light source spectrum can aid in conservation of art collections in museums by reducing damage caused by optical radiation while preserving color fidelity.

Correlations among lighting quality metrics for interior lighting

Correlations between selected lighting quality metrics derived from the spectrum were computed and interpreted for a representative set of interior light source spectra. Metrics of brightness and the melanopic effect were strongly correlated with each other but not with the metrics of colour quality. Results can be used to establish a two-dimensional diagram with criterion values to ensure the general user acceptance of a lighting system. This diagram can be extended in the future by further metrics describing light intensity and spatial and temporal light distributions. Relationships between lighting quality metrics and colorimetric quantities as well as photoreceptor signal values are also shown.

Appearance of Achromatic Colors Under Optimized Light Source Spectrum

Light source spectrum can be optimized for object reflectance to reduce the energy consumption by reducing the amount of light absorbed by surfaces. While the feasibility of this approach to architectural lighting has been demonstrated, this concept has only been tested with objects of highly saturated colors. Here, the color appearance of 24 Macbeth ColorChecker test samples, which includes achromatic surfaces (i.e., gray, black, and white), illuminated by optimized theoretical test spectra and reference light sources (incandescent, equal-energy radiator, and phosphor-coated white LED) were calculated using a color space based on the International Commission on Illumination's (CIE) color appearance model, CIECAM02-UCS. Results show that energy consumption could be reduced to between 39% and 90%, with small shifts in color appearance, when considering all object colors. When lighting is optimized for achromatic test samples, energy consumption and light absorption were reduced more than when optimized for colorful surfaces, with imperceptible shifts in color appearance.

LIGHTING ENVIRONMENT IN EDUCATIONAL AND MEDICAL INSTITUTIONS: THE PROBLEM OF THE OPTIMAL CHOICE

For the public health, it is essential to determine in what light environment people will develop, live and work in the near future. The present and future of the light environment determine trends in the development of lighting sources. It is important to make a hygienic assessment of the spectra of modern light sources to match the spectrum of the safe sunlight. Trends in the development of led lighting until 2020 and methods of experimental and computer (numerical) modeling of the spectrum of sunlight based on LEDs of various types and their analytical models are considered. The proposed models are shown to allow synthesizing the spectra of led lamps close to sunlight, but they do not meet the requirements of biological adequacy for the human visual analyzer in spectrum width, continuity, uniformity and a set of wavelengths of photon streams that ensure the effective functioning of the human visual analyzer and its hormonal system. The limitations must be taken into account in the development of led lamps by the criterion of root mean square approximation to the spectrum of sunlight and technical implementation to protect the light sensitivity of ganglion cells.

An optical fiber Fabry–Pérot micro-pressure sensor based on beam-membrane structure

In this paper, an optical fiber Fabry–Pérot (FP) sensor for micro-pressure measurement is proposed. The FP interferometric cavity is composed of an end face of the incident optical fiber and a sensitive silicon diaphragm. The sensitive silicon diaphragm creatively utilizes a beam-membrane structure which is fabricated by micro-electro-mechanical system manufacturing technology. The finite element method simulation results show that the beam-membrane structure can achieve higher sensitivity and better linearity. The sensor performance test platform is built by a ASE-wide spectrum light source, optical spectrum analyzer, micro-pressure gas source and so on. The phase demodulation method is employed to demodulate the cavity length signal from the spectrum. The measure range of the sensor is 0–10 KPa, and the experimental sensitivity of the cavity length can reach to 242 nm KPa−1.

Emerging Organic and Organic/Inorganic Hybrid Photovoltaic Devices for Specialty Applications: Low‐Level‐Lighting Energy Conversion and Biomedical Treatment

AbstractThis article reviews the progress made in emerging photovoltaic devices, including dye‐sensitized solar cells, organic solar cells, and perovskite solar cells, for specialty applications. Because they all feature tunable band structures, which can be modified through molecular design and/or altered compositions, the properties of emerging photovoltaic devices can be tailored to fit the special requirements of a particular application. For instance, they can be designed according to the emission spectrum of an artificial light source (e.g., fluorescence lamp and white light‐emitting diode), thereby efficiently converting the indoor lighting to electricity. Furthermore, because there exists a near‐infrared window—ranging from 650 to 1350 nm—in which photons can penetrate deeply into tissues, the absorption bands of these photovoltaic devices can be tailored specially to this therapeutic window to harvest tissue‐penetrating light, thereby wirelessly providing power to biomedical devices positioned beneath the skin. The rapid progress made in these two representative areas suggests further promising applications of such emerging photovoltaic devices.

Assessment of Double Modulation Pyrometry as a diagnostic tool for use in concentrated solar facilities

Double modulation pyrometry (DMP) is a pyrometric method developed to enable radiometric temperature measurements in solar simulators, where solar blind pyrometry cannot be applied due to the continuous spectrum of the artificial light source. Sofar, DMP has been characterized in two solar simulator facilities, but no direct comparison to a reference pyrometer has been performed until now due to the limitations of applying pyrometry in solar simulators. Here, a series of experiments is reported that were conducted in concentrated natural sunlight where reference pyrometers are available. They demonstrate the performance enhancement gained by utilizing the inherent advantages of DMP, i.e. the in-situ reflectance measurement and the freedom to select the operation wavelength.

Application of Fresnel diffraction from a phase step to determination of the spectral line profile

Determination of the spectral profile of light signals is an effective way to characterize the structure and dynamics of materials, and also light sources. In this work, we introduce a simple, fast, and cost effective line fitting technique, in which Fresnel diffraction from a phase step is used to determine the central wavelength and linewidth of the spectra of light sources. In principle, a single diffraction pattern suffice to determine the line profile. As proof-of-principle examples, two light emitting diode sources have been investigated using phase steps with different heights. Reproducible results are obtained with relative uncertainties in the order of 10−2 for both the central wavelength and linewidth. Comparison with conventional spectroscopy measurements are also provided.

The association between correlated colour temperature and scotopic/photopic ratio

The scotopic/photopic ratio (S/P) is a parameter that may be considered in the design of road lighting. This paper compares the S/P ratio and correlated colour temperature (CCT) for 297 light source spectra identified in IES Technical Memorandum TM-30-15 to test the assumption that higher S/P ratios demand higher CCTs. The results suggest that, for a given lamp type, there is a strong association between S/P ratio and CCT, and hence that for a given CCT only a small variation in S/P ratio is available. However, the results also suggest that a larger variation in S/P ratio is possible if the lighting designer is able to consider a change in lamp type.

Study of the Light Emitting Diode as a photoreceptor: Spectral and electrical characterization as function of temperature and lighting source

In this study, the temperature influence on the spectral responsivity of a Light Emitting Diode (LED) used as a photoreceptor, combined to light source spectrum is correlated to electrical characteristics in order to propose an alternative method to estimate LED junction temperature, regardless of the absolute illumination intensity and based on the direct correlation between the integral of the product of two optical spectra and the photo-generated currents. A laboratory test bench for experimental optical measurements has been set in order to enable any characterizing of photoelectric devices in terms of spectral behaviour, in a wavelength range placed between 400–1000 nm, and of current-voltage characteristics as function of temperature by using two different illumination sources. The temperature is analysed in a range from 5 °C up to 85 °C, so as to evaluate thermal variation effects on the sensor performance. The photo-generated current of two LEDs with different peak wavelengths has been studied. Research has observed and mathematically analysed what follows: since the photo-generated current strictly depends on the combination between the spectral response of the photoreceptor and the lighting source response, it becomes possible to estimate indirectly the junction temperature of the LEDs by considering the ratio between the photogenerated currents obtained by using two different illumination sources. Such results may for one thing increase knowledge in the fields where LEDs are used as photo-detectors for many applications and for another, they could be extended to generic photodetectors, thus providing useful information in photovoltaic field, for instance.