Spectral Luminous Efficiency Function Research Articles

Evaluating Energy Efficiency and Colorimetric Quality of Electric Light Sources Using Alternative Spectral Sensitivity Functions

Photometric and colorimetric quantities are calculated using spectral luminous efficiency and color matching functions (CMFs), respectively. Past studies highlighted the limitations of the standard sensitivity functions based on visual experiments conducted over a century ago. There have been new alternatives proposed, but the effect of the proposed alternatives functions on energy efficiency, and the colorimetric quality of light sources has rarely been investigated. It is reasonable to assume that updating photometric and colorimetric calculation procedures will make significant impacts on the characterization of electric light sources. Here, the impact of six luminous efficiency functions and six CMFs on luminous efficacy of radiation and chromaticity calculations were analyzed. Results indicate a significant effect of alternative functions on luminous efficacy of radiation (LER), chromaticity coordinates (CIE 1931 x,y and CIE 1976 u′,v′) and Duv. The biggest impact was caused by the change in the visual field of view (2-degree vs. 10-degree observer), highlighting the importance of visual field size for color and luminosity function. Updating the standardized luminous efficiency function may impact the performance characterization of electric light sources, but cost-benefit analysis should be studied to understand the broad impacts.

Evaluation of different general V(λ) mismatch indices of photometers for LED-based light sources in general lighting applications

The general V(λ) mismatch index, , of a photometer quantifies the deviation between its determined relative spectral responsivity, , and its nominal responsivity, the spectral luminous efficiency function for photopic vision, V(λ). LED-based light sources now dominate in general lighting, displacing incandescent and fluorescent lamps. Furthermore, the calibration of photometers will very likely see the replacement of the reference CIE standard illuminant A with CIE reference spectrum L41. The article evaluates the consequences. Should we also change the definition of the general V(λ) mismatch index? Based on performance criteria, the individual indices are evaluated using various datasets with the help of statistical analyses. As a result, the authors can conclude that the current definition works very well even under changed calibration and application conditions and does not need to be changed. Other evaluated indices for a new index definition perform only slightly better in some cases, but do not generate generally better properties.

On the accurate characterization of quantum-dot light-emitting diodes for display applications

Quantum dot light-emitting diodes (QLEDs) are a class of high-performance solution-processed electroluminescent (EL) devices highly attractive for next-generation display applications. Despite the encouraging advances in the mechanism investigation, material chemistry, and device engineering of QLEDs, the lack of standard protocols for the characterization of QLEDs may cause inaccurate measurements of device parameters and invalid comparison of different devices. Here, we report a comprehensive study on the characterizations of QLEDs using various methods. We show that the emission non-uniformity across the active area, non-Lambertian angular distributions of EL intensity, and discrepancies in the adopted spectral luminous efficiency functions could introduce significant errors in the device efficiency. Larger errors in the operational-lifetime measurements may arise from the inaccurate determination of the initial luminance and inconsistent methods for analyzing the luminance-decay curves. Finally, we suggest a set of recommended practices and a checklist for device characterizations, aiming to help the researchers in the QLED field to achieve accurate and reliable measurements.

Transformations from cone responses to opponent color spaces

AbstractWe have described a number of transformations by mapping the cone signal vector , formed by , to opponent space , formed by achromatic signal , red‐green signal and yellow‐blue signal . Two new transformations, and , are proposed, based on the CIE 2006 spectral luminous efficiency function, , and Hurvich's opponent spectral red‐green and yellow‐blue responses, and , without and with constraints, respectively. is better than in terms of best fit of and , and both transformations improved previously proposed ones. Finally, we discuss the neutral conditions in cone space using each of the new and some of the extant transformations, as well as choosing scaling factors so that the neutral conditions in cone space are satisfied.

Experimental study on brightness perception changing effect of pulsed light in short wavelengths

Visual perception of pulsed light (PL) in wavelength of 400 nm–500 nm with different duty ratio (Dr) was studied. The pulsed light frequency was set as 100Hz, above human critical fusion frequency (CFF). Based on self-built experiment system, Brightness Changing Factor (BCF) values was defined and calculated via a quantitative measure for visual perception of pulsed light. We found some Brightness Reduction effects on visual perception of PL at certain wavelength, in addition to the general Brightness Enhancement effects found by previous research. Further, logarithmic function fitting between BCF values and duty ratio in different wavelengths was conducted. Finally, we propose a modulated spectral luminous efficiency function (Vp(λ)) of PL based on the logarithmic fitting and make a discussion on the relationship between the BCF and the physiological basis of human vision.

Research on the Impact of Road Landscape Color on the Driving Fatigue of Drivers

In the closed-loop system of human-vehicle-road-environment, the environment has a very important impact on drivers. The long-term monotonous environment will lead to the visual fatigue of drivers, thus affecting the driving safety; while a good road landscape environment will give drivers a comfortable visual experience, which can relieve the visual fatigue of drivers to some extent. This paper takes the Impact of landscape color on the driving fatigue of drivers as the view of research and reflects the impact of landscape color on driving safety. This paper analyzes the basic attributes of color and analyzes the color fatigue characteristics of drivers using the spectral sensitivity (spectral luminous efficiency) function. Due to the uncertainty of the color attribute value of roadside landscape environment, the eye tracker is used to record the characteristics of the eye movement of drivers in the experiment. Also, based on the example of the landscape color of Qinghai-Tibet Highway, this paper selects the blinking frequency of drivers as the analysis index to quantitatively measure the driving fatigue of drivers, which can indirectly reflect the relationship between landscape color and driving safety.

Effect of optical filters and light source spectra on the spectral luminous efficiency function measurement

During the measurement of spectral luminous efficiency function $$V\left( \lambda \right)$$, monochromatic visual stimuli of higher luminance can be obtained by narrow band optical filters with broad band light sources, compared to monochromators. However, the distortion of $$V\left( \lambda \right)$$ is inevitably caused due to the bandwidth of the optical filters. In this paper, the effect of optical filters and light source spectra on the spectral luminous efficiency function $$V\left( \lambda \right)$$ measurement is studied. Filters with different spectral transmittances and light sources with different spectral power distributions are considered in the model to simulate visual sensitivity experiment. Compared with real $$V\left( \lambda \right)$$, the distortion of the simulated $$V\left( \lambda \right)$$ caused by the bandwidth of filters is quantitatively evaluated with the aid of a quality indicator, mismatch error $$f'$$. Results and conclusions in this paper can be used as a guide to optimize the design of the visual sensitivity experiments for $$V\left( \lambda \right)$$ measurement.

Black-body luminance and magnitudes per square arcsecond in the Johnson-Cousins BVR photometric bands

A relevant amount of light pollution studies deal with the unwanted visual effects of artificial light at night, including the anthropogenic luminance of the sky that hinders the observation of the celestial bodies which are a main target of ground-based astrophysical research, and a key asset of the intangible heritage of humankind. Most quantitative measurements and numerical models, however, evaluate the anthropogenic sky radiance in any of the standard Johnson-Cousins UBVRI photometric bands, generally in the V one. Since the Johnson-Cousins V band is not identical with the visual CIE V() used to assess luminance, the conversion between these two photometric systems turns out to be spectrum-dependent. Given its interest for practical applications, in this Letter we provide the framework to perform this conversion and the transformation constants for black-body spectra of different absolute temperatures. Full Text: PDF ReferencesF. Falchi et al. "The new world atlas of artificial night sky brightness", Sci. Adv. 2, e1600377 (2016). CrossRef M. Kocifaj, "A review of the theoretical and numerical approaches to modeling skyglow: Iterative approach to RTE, MSOS, and two-stream approximation", Journal of Quantitative Spectroscopy & Radiative Transfer 181, 2 (2016). CrossRef M.S. Bessel, "UBVRI PASSBANDS", Publications of the Astronomical Society of the Pacific, 102, 1181 (1990).. CrossRef CIE, Commision Internationale de l'Éclairage. CIE 1988 2° SpectralLuminous Efficiency Function for Photopic Vision. (Vienna, Bureau Central de la CIE, 1990) DirectLink S. Bará, "Variations on a classical theme: On the formal relationship between magnitudes per square arcsecond and luminance", International Journal of Sustainable Lighting IJSL 19(2), 104 (2017). CrossRef A. Sánchez de Miguel, M. Aubé, J. Zamorano, M. Kocifaj, J. Roby, C. Tapia. "Sky Quality Meter measurements in a colour-changing world", Monthly Notices of the Royal Astronomical Society 467(3), 2966 (2017). CrossRef M.S. Bessell, "Standard Photometric Systems", Annual Reviews of Astronomy and Astrophysics, 43, 293 (2005). CrossRef J.B. Oke, "Absolute Spectral Energy Distributions for White Dwarfs", The Astrophysical Journal Suppl. Series 236(27), 21 (1974). CrossRef J.B. Oke, J.E. Gunn, "Secondary standard stars for absolute spectrophotometry", The Astrophysical Journal 266, 713 (1983). CrossRef M.R. Blanton, S. Roweis S., "K-Corrections and Filter Transformations in the Ultraviolet, Optical, and Near-Infrared", The Astronomical Journal, 133(2), 734(2007). Table 1. CrossRef

Apparent magnitude of earthshine: a simple calculation

The Sun illuminates both the Moon and the Earth with practically the same luminous fluxes which are in turn reflected by them. The Moon provides a dim light to the Earth whereas the Earth illuminates the Moon with somewhat brighter light which can be seen from the Earth and is called earthshine. As the amount of light reflected from the Earth depends on part of the Earth and the cloud cover, the strength of earthshine varies throughout the year. The measure of the earthshine light is luminance, which is defined in photometry as the total luminous flux of light hitting or passing through a surface. The expression for the earthshine light in terms of the apparent magnitude has been derived for the first time and evaluated for two extreme cases; firstly, when the Sun’s rays are reflected by the water of the oceans and secondly when the reflector is either thick clouds or snow. The corresponding values are and respectively. The earthshine value reported by Jackson lies within these apparent magnitudes. This paper will motivate the students and teachers of physics to look for the illuminated Moon by earthlight during the waning or waxing crescent phase of the Moon and to reproduce the expressions derived here by making use of the inverse-square law of radiation, Planck’s expression for the power in electromagnetic radiation, photopic spectral luminous efficiency function and expression for the apparent magnitude of a body in terms of luminous fluxes.

Spectral and photopic studies for high intensity discharge (HID) lamps

Outdoor lighting sources such as High Intensity Discharge lamps (HID) are common in these days. This research is focusing on the relation between the spectral power distribution and luminous efficiency function V (λ ), which describes the average spectral sensitivity of human visual perception of brightness. The most useable HID lamps inside Egyptian markets are high pressure mercury (HPM), high pressure sodium (HPS) and metal halide (MH). A set up based on single monochromator and integrating sphere for relative spectral power distribution and absolute luminous flux measurements are used, respectively. The accompanied standard uncertainties with the measurements are evaluated.

Equivalent Brightness Fitting Calculation Method about White LEDs

White LEDs can show different correlated color temperature (abbreviated as CCT) by adjusting the luminous spectrum peak distribution and relative strength. Recent research results indicate that spectral luminous efficiency function of mesopic vision Vmes(λ) and equivalent brightness are associated with luminous spectra of light sources. A series of white LEDs with different CCT are tested and calculated, it shows white LED with higher CCT has higher mesopic vision equivalent brightness, although the brightness are identical when the tester corrected by traditional photopic vision spectral luminous efficiency V(λ). From the equivalent brightness curve fitting, the curve can be described as a polynomial function, for it excellent correlation, the more value of equivalent brightness could be calculated without complex derivation.

Green Innovation Design Based on TRIZ Theory

The mesopic vision theory is used to study illumination properties of series of light sources, through the test of luminous spectrum and derivation based on the MOVE model, the results show that spectral luminous efficiency function Vmes(λ) is between traditional V(λ) and V′(λ) when the background brightness under mesopic vision condition, and the function of Vmes(λ) is changed with the different of light sources and background brightness. Based on human visual perception, the mesopic vision equivalent brightness can be calculated, which of HPS is lower than test brightness corrected by V(λ), but white LEDs and FL show opposite phenomena, and the different value between mesopic and photopic brightness presents reduce trend with rising of background brightness.

Properties of Light Sources under Mesopic Vision

The mesopic vision theory is used to study illumination properties of series of light sources, through the test of luminous spectrum and derivation based on the MOVE model, the results show that spectral luminous efficiency function Vmes(λ) is between traditional V(λ) and V′(λ) when the background brightness under mesopic vision condition, and the function of Vmes(λ) is changed with the different of light sources and background brightness. Based on human visual perception, the mesopic vision equivalent brightness can be calculated, which of HPS is lower than test brightness corrected by V(λ), but white LEDs and FL show opposite phenomena, and the different value between mesopic and photopic brightness presents reduce trend with rising of background brightness.

Road Luminaire’ Mesoptic Luminous Efficiency Analysis

Four kinds of traffic lighting sources HPS, MH, LED and EDL are widely used in roads and tunnels, the luminance at this place almost in the range of 1-10 cd/m2, which is the mesoptic vision. The mesoptic luminous efficiency can be calculated from photopic vision spectral luminous efficiency function. The results indicate that HPS’s luminous efficiency increased with improve of adaptation brightness, while the rest three kinds of light sources’ luminous efficiency reduced. At the same luminance level, HPS, MH, LED and EDL’s mesoptic luminous efficiency reduced in turn.

Highway Tunnel Lighting Research Based on Mesopic Vision

The white LED and high-pressure sodium lamp (HPS) are used to simulate highway tunnel lighting under different background brightness (abbreviated as B) conditions, from a series of reaction time tests, the result shows that white LED can provide shorter reaction time for observers compared with HPS, further research suggests under the mesopic vision, different kinds of light sources maybe have unlike brightness, although which is identical under the photopic vision. From the luminous spectrum test and mesopic vision spectral luminous efficiency function fitting calculation, the mesopic equivalent brightness can be determined with certain light source and B value. This conclusion would provide a more accurate and lower energy consumption lighting design method for highway tunnel.

Spectral discomfort glare sensitivity investigations

The main concern of car headlamp manufacturers is to provide better visibility. Unfortunately, by increasing the luminous intensity of the headlamp, the risk of increasing discomfort glare for the other road users increases. One possibility to increase visibility and decrease glare could be the selection of a spectral power distribution for the headlamp such that it emits in wavelength regions (if such wavelengths exist) where luminous sensitivity is high, and glare sensitivity is low. For this the spectral discomfort glare sensitivity of humans under low photopic conditions has to be determined. Spectral discomfort glare sensitivity was determined using ten young observers, requesting the observers to select medium glare settings of monochromatic radiations based on the de Boer glare rating scale, both at near-foveal and 10 degrees extra-foveal directions of the 2 degrees diameter glare source. It was found that the spectral discomfort glare sensitivity function could not be described by a simple addition of the photopic spectral luminous efficiency function and the short wavelength cone fundamental, but that the contribution of the chromatic channels of human vision may also have to be considered.

Ambulant recording of light for vision and non-visual biological effects

Data on the exposure of the human eye to light are essential for investigation into the interaction of light with man. According to present knowledge, two different spectral sensitivities of the visible irradiance are relevant: (1) the spectral luminous efficiency function for vision and (2) the action spectrum for melatonin suppression, also used for other non-visual biological effects. We developed a device called LuxBlick to measure and record both quantities. It consists of two light sensors that are fixed on the wearer’s head, and a control unit and data recording mini-computer worn in a bag around the waist. Real-time data are accessible to those wearing the device. Suitable to be worn in everyday life, the parts at the head are of low mass at the head and inconspicuous.

Mesopic models—from brightness matching to visual performance in night-time driving: a review

At present, suitable methods to evaluate the visual effectiveness of lighting products in the mesopic region are not available. The majority of spectral luminous efficiency functions obtained to date in the mesopic range have been acquired by heterochromatic brightness matching. However, the most recent studies in the mesopic field have adopted a task performance-based approach. This paper summarizes the major mesopic models proposed so far, presenting in detail the experimental conditions of these studies. The authors represent a research consortium which has adopted the task performance-based approach for night-time driving in which mesopic visual performance has been divided into three subtasks. Data for each sub-task will be generated by using a set of common parameter values and 120 observers. The approach and methods used by the consortium are presented.

Spectral luminous efficiency as a function of age.

Spectral luminous efficiency function for a 2-deg field at a photopic level (100 Td) was measured for 91 observers by flicker photometry (FP) and for 97 observers by direct brightness matching (DBM), to find age-related change in the efficiency function as well as to obtain a reliable data set to be used in photometry. Observers ranged in age from 11 to 78 years. A gradual reduction of luminous efficiency with age was observed for both functions by FP and by DBM in the short-wave region, which was expected because of the age-related increase of optical density of eye lens. A similar age-related reduction of efficiency was observed in the long-wave region for the function obtained by DBM; this reduction was regarded as being due to reduced chromatic contribution to brightness with age. Principal components analysis on the spectral efficiency data and an analysis of the efficiency difference between the data obtained by DBM and FP confirmed this conclusion. Assuming a log-linear change in efficiency with age for any wavelength throughout the life span, spectral luminous efficiency function at any age was derived for photometric use.

年代別の分光視感効率関数

年代別の分光視感効率関数