Relative Luminous Efficiency Research Articles

One Hundred Years of Relative Spectral Luminous Efficiency Curve – CIE V(λ) Function

In 1924, the International Commission on Illumination adopted the function of relative spectral luminous efficiency V(λ), which made it possible to move from subjective methods for assessing light sources of radiation to objective methods for measuring light quantities, constructing a system of light quantities, and creating standards for reproducing units of light quantities. Research in the field of physiological perception of light has continued and continues throughout these hundred years. This article is devoted to a brief review of materials from studies of actinic properties of the visual apparatus, i.e. spectral weighting functions of human perception of optical radiation, taking into account adaptation to various lighting conditions, as well as taking into account studies of fundamental physiological reactions of the visual system.

Visual Perception in External Lighting Conditions

LED street lighting is a topical trend in modern outdoor lighting. High light output of LEDs creates all conditions for modernization of electric lighting networks in Ukraine. Human vision is a complex process associated with retinal light perception. Vision is divided into: day vision, night vision, and twilight vision. The function of the eye is highly dependent on the distribution of brightness in the field of vision. The spectral sensitivity of photoreceptors varies for different wavelengths of the visible spectrum and different levels of light intensity. The rationing of the lighting installation is based on detailed studies of the observer’s visual performance depending on different lighting conditions. One of the main luminous parameters that can easily be measured objectively is illumination. Brightness as a function of illumination, the observer’s position and the spectral coefficient of the working surface reflection is more informative, but has some difficulty in measuring. There is a clear need to develop a system that would make it possible to uniquely assess the visual efficiency of a given spectral composition under certain observation conditions. It was decided to introduce the term equivalent brightness as the parameter of such a system. The difficulty of using the function Vek(λ,Lek) to calculate the equivalent brightness is the function’s dependence Vek(λ,Lek) on Lek. The aim of the study is to approximate the function of the relative spectral luminous efficiency in mesopathic regions by a set of standard CIE functions that do not depend on the value of equivalent luminosity. The calculation method Vek(λ,Lek) is proposed using only two normalized functions of the relative spectral radiation efficiency for day V(λ) and night V'(λ) vision. The use of such approximation function makes it possible to determine the equivalent brightness, which adequately reflects the level of visual perception under the conditions of ambient illumination, based on the photometric brightness of the light source. To calculate Vek(λ,Lek) we use the ICE recommended functions of relative spectral light efficiency for the twilight vision, which are based on the spectral composition of the blackbody radiation with a color temperature of 2042 K. The use of the developed methodology provides results that more accurately characterize the efficiency of light sources in outdoor lighting installations compared to the results of calculations obtained when using standard methods.

High Stability of Liquid-Typed White Light-Emitting Diode with Zn0.8Cd0.2S White Quantum Dots

In this study, we demonstrate a new design of white light-emitting diode (WLED) with high stability and luminous efficiency as well as positive aging. Colloidal ternary Zn0.8Cd0.2S (named Zn0.8) white quantum dots (WQDs) were prepared by chemical route and dispersed in xylene, integrating them into an ultraviolet light-emitting diode (UV-LED) to form WQD-white light emitting diode (WQD-WLED). High efficiency, high color quality and excellent reliability of WQD-WLED with neutral white correlated color temperature (CCT) can be obtained. The experimental results indicate that the stability of relative luminous efficiency and color rendering index (CRI) of the WQD-WLED can reach up to 160 and 82%, respectively. Moreover, the WQD-WLED can operate more than 1000 h under 100 mA, and the quantity of WQDs in the glass package can be reduced.

Synthesis and characteristics of nano-size sandwich structure (Y,Gd)BO 3: Eu 3+ phosphors

The sandwich structure core–shell–shell nanospheres SiO 2@(Y,Gd)BO 3:Eu 3+@SiO 2 (SiO 2@YGB@SiO 2) have been synthesized by depositing YGB nanoparticles on silica core surface through the precipitation method, followed by sol–gel processing of tetraethoxysilane (TEOS) to form smooth silica shell over the surface of YGB. The phosphors were characterized by X-ray diffraction (XRD), scanning electronic microscope (SEM), transmission electronic microscope (TEM) and photoluminescence spectra. The results showed that the phosphors with spherical morphology can be produced easily by assembling the core–shell or core–shell–shell structure, and the XRD patterns indicated that the crystallinity of YGB is weakened due to the core–shell structure, which resulting from the local site symmetry of Eu 3+ was decreased. The photoluminescence properties of the product are compared with those of the pure YGB, the core–shell structure SiO 2@YGB and YGB@SiO 2. The emission intensity, relative luminous efficiency and Red/Orange values of phosphors are increased in the order SiO 2@YGB@SiO 2>SiO 2@YGB>YGB@SiO 2>YGB; and the chromaticity coordinates of the phosphors are shifted from orange of pure YGB to red of SiO 2@YGB@SiO 2.

Spatiotemporal Behavior of Excited Xenon-Atom Density in Accordance With Xenon Mole Fraction to Neon in Alternating-Current Plasma Display Panels by Laser-Absorption Spectroscopy

In this paper, spatiotemporal behavior of the excited Xe-atom density of metastable state was investigated by laser-absorption spectroscopy in alternating-current plasma display panel in accordance with the Xe mole fraction to Ne, which can be connected to the relative luminous efficiency over all spaces in a discharge cell. The various test panels with Xe mole fractions of 4%, 7%, 10%, and 15% to Ne have been used in this paper, in which discharge cell with T-typed indium-tin-oxide electrode and closed-barrier rib has been adopted. In this paper, the density of metastable state for the excited Xe atom is found to increase slowly beyond the Xe mole fraction of 10%. It is also accordingly noted that the luminous efficiency increases slowly beyond the Xe mole fraction of 10%, which is similar to that of the density of the excited Xe atoms in the metastable state in this paper.

A Novel Time Based Current Compensator for LED Back Light Modules

The paper proposes a novel time based brightness compensation circuit for LED back light modules. The brightness of LED decays while running under constant current driven condition. We have designed a suitable controller to compensate the driving currents to maintain the brightness. The compensation data were calculated from the relative luminous efficiency – time curve provided by the LED manufacturer and were stored in the microprocessor. -The embedded system used the running time of the LED in the back light module as an independent variable for tuning the driving current. The experiment results showed that the brightness of different operating times’ LED arrays can be held almost the same as the new ones.

生体リズムを考慮した光環境評価

Recent lines of research show that light is important not only to human vision but also to human circadian regulation. The photometric quantities based on the relative photopic luminous efficiency function are used to express lighting condition. However it has been shown that the spectra sensitivity curve for circadian regulation is different from the spectra sensitivity curve for the photopic visual system. In order to support lighting design considering circadian regulation, in this paper, a method to evaluate light based on melatonin suppression, one of circadian rhythms, was proposed. A formula, using spectrum distribution of radiant flux and action spectrum of melatonin suppression shown in a previous study, was developed to calculate the effect of light on human circadian regulation. Also a simplified formula was proposed in which illuminance and color temperature were used. The applicability of the simplified formula to actual spaces was tested by measuring light from lamps, the sun, and computer display and light in houses.

Saccadic suppression of achromatic and chromatic responses measured by increment-threshold spectral sensitivity.

We measured spectral-sensitivity functions during saccadic eye movement by the increment-threshold method to test whether saccades selectively suppressed achromatic or chromatic responses. A circular monochromatic test stimulus of 12-deg diameter was presented for 10 ms on a 62 deg x 43 deg white background, and observations were made under three conditions: during fixation, during 6-deg saccades, and immediately after saccades. In two additional conditions the test stimulus was made to move during fixation and during 6-deg saccades at the same speed and in the same direction as the saccades. The during-fixation spectral-sensitivity function was found to resemble the relative luminous efficiency V (lambda) function in shape except for the case of short wavelengths, whereas the during-saccade spectral-sensitivity function showed lower sensitivity for all wavelengths and had three prominent peaks at approximately 440, 530, and 600 nm. These characteristics did not depend on whether the stimulus was stationary or moving. These results indicated that saccadic suppression was greater for achromatic than for chromatic response. A possible suppression mechanism was discussed involving the magno and parvo pathways.

Stability of the Stiles-Crawford Function in a Unilateral Amblyopic Subject over a 38-Year Period: A Case Study

The relative luminous efficiency curves for light entering different parts of the entrance pupil [Stiles-Crawford functions (SCFs)] of subject TG, whose right eye is amblyopic, were determined earlier for both the normal and the amblyopic eye. The left eye was found to have a normal SCF, varying from the center to the edge of the entrance pupil by an entire log unit. However, the SCF for the right eye was found to be abnormal, showing peak sensitivity far toward the temporal edge of the pupil and varying from center to edge by only one-third of a log unit. From these data it was inferred that the photoreceptors were in poor alignment. In October, 1993 the subject experienced a retinal detachment in the left (nonamblyopic) eye, requiring cryoretinopexy, drainage of subretinal fluid, and a scleral buckle. Postoperatively, visual acuity recovered to 6/9 to 6/7.5 (20/30 to 20/25), but vision was poor when illumination or contrast was low. In order to determine whether the decrement in visual performance was the result of misalignment of the photoreceptors, the subject's SCFs were determined 9 months postoperatively for both eyes, using a procedure similar to that used earlier. The relative luminous efficiency curves for both eyes were found to be surprisingly similar to the corresponding curves found 38 years earlier. It was concluded that any decrease in visual function resulting from the retinal detachment and repair was not caused by misalignment of the photoreceptors. We infer that the mechanisms resulting in the exceptionally high degree of photoreceptor alignment in the left eye and the disturbed alignment in the right eye are still present.

New method based on random luminance masking for measuring isochromatic zones using high resolution colour displays.

A new method of measuring normal hue discrimination ellipses and dichromatic zones using a high resolution colour monitor is described. The test involves the detection of chromatic bars on a grey background (x = 0.305, y = 0.323) having a luminance of 34 cd m-2. Elements of the background matrix of square checks are varied randomly in luminance in space and time to provide random luminance masking (RLM) which compensates for differences in the relative luminous efficiency of different observers. The measurement technique provides a rapid and comprehensive colour vision test. Typical results are presented for normal trichromats, protanopes and deuteranopes without RLM and with the RLM set of 25%. The size of the discrimination ellipse in normal observers is the same in both viewing conditions, but the use of the RLM technique reveals the extent of the isochromatic zones in colour deficient observers.

Effects of luminance level on the saturation function: Sensitivities based on saturation discrimination

AbstractThe saturation of a monochromatic light λ is defined as the reciprocal of the just noticeable colorimetric purity ΔP(λ) from a white, which is a conventional definition having been used previously often. The present study measures saturation functions of monochromatic lights at various luminance levels ranging from 10 to 1000 Td. The main result of this article is that the saturation function systematically changes in shape with the luminance level; as the luminance increases, the values of 1/ΔP(λ) relatively increase for shorter wavelengths. The chromatic sensitivity function C(λ) is defined by the reciprocal of the radiance of a monochromatic light λ added to the white field in order to detect a difference in chromaticity from the equal‐luminance reference white. The C(λ) functions at various luminance levels are shown to have three peaks at the short‐, middle‐, and long‐wavelength regions. These peaks are similar to those of the increment threshold functions, and the saturation function can be approximated by the ratio of the increment threshold spectral sensitivity to the relative luminous efficiency, except for the 570 nm data.

毛髪のつや測定器の開発

Hair luster is one of the criteria to judge the beauty of hair. Therefore, young women are interested in hair luster.Luster is one of the optical properties. The reproducibility of the data measured optically for hair luster with conventional instruments has been poor and the results obtained have been in less agreement with visual evaluation, because of the influence of color and distortions of hair samples.Maximal reflection value measured at specular reflection angle (S) and diffuse reflection value measured in the vertical direction to the plane of hair shafts (d) were obtained with goniophotometer on hair tresses with the same luster and different color. “S-d Value” was introduced as “Luster Value” to minimize the influence of color of hair. However, it was not possible to eliminate the influence of color completely by this treatment. Therefore the distribution of wavelength of diffuse and specular reflection was controlled by filters to adjust spectral response of optical detector to relative luminous efficiency curve. By these treatments, the influence of color was eliminated. The incident angle was set at 45° to make “signal noise ratio” higher and the apparatus smaller. Hair holder, which is easy to handle, was developed to keep up parallelism of hair fibers, because disorder of them had considerable influence on the measurement of hair luster.A handy apparatus, which makes hair luster measurement possible without cutting hair off, is developed. The results obtained correlate to visual evaluation.

Individual observer data for the 1955 Stiles-Burch 2 degrees pilot investigation.

Although the results of the 2 degrees Stiles-Burch investigation were published in 1955 in the form of mean data, individual results have not been available. It is only recently that they have been in wide demand. Since in 1955 this demand was not anticipated, individual results were left in an unprocessed form; the processing has now been completed. Tables are given for each of 10 observers and their mean for color-matching functions, unit (WDW) coordinates, and relative luminous efficiency functions.

Relative spectral luminous efficiency function of 2.DEG. and 10.DEG. fields determined by flicker photometry and direct heterochromatic brightness matching.

Relative spectral luminous efficiency function of 2.DEG. and 10.DEG. fields determined by flicker photometry and direct heterochromatic brightness matching.

Electrophysiology of retinal ganglion cells in the mouse: a study of a normally pigmented mouse and a congenic hypopigmentation mutant, pearl.

1. The organization of the receptive fields of retinal ganglion cells in te normal mouse was studied qualitatively in recordings from 43 single axons in the optic nerve and optic tract, and the light sensitivity was studied quantitatively in 26 of these cells by measuring incremental sensitivity. 2. The receptive fields of normal animals were elliptical, had concentric center and peripheral subdivisions, and had an antagonistic center/surround organization; the receptive-field centers ranged from 1.95 to 83 degrees in diameter, with a median of 7 degrees. 3. The incremental sensitivity to white light was measured using a criterion response of 10 extra spikes; the most sensitive dark-adapted cell required a stimulus luminance of 3.5 x 10(-3) cd/m2 to generate a criterion response. 4. The action spectrum measured at seven different wavelengths (433-619 nm) from ganglion cells in the normally pigmented mouse resembled the CIE (International Commission on Illumination, CIE 1957 (11)) relative scotopic luminous efficiency function (41) and is consistent with a curve having a peak around 500 nm. 5. On light adaptation with blue light (less than 460 nm), the sensitivity to longer wavelength stimuli increased by 0.2-0.5 log units relative to the sensitivity to the shorter wavelengths; these results are compatible with the presence of a photoreceptor sensitive to long wavelengths in the normally pigmented mouse (C57BL/6J+/+). 6. The organization of the receptive fields of 48 retinal ganglion cells from the hypopigmentation mutant pearl (C57BL/6J-pe) was also studied qualitatively; the receptive field organization was similar to that of the normally pigmented mouse. 7. In 25 cells from dark-adapted pearl mice, the incremental sensitivity to white light was, on the average, 1.6 log units less than that for normal mice. 8. The dark-adapted action spectrum of pearl mice was similar to that of normally pigmented mice. However, a shift in sensitivity to longer wavelengths did not occur on selective light adaptation with the most luminous blue light (less than 460 nm) background that we could produce. 9. We conclude that pearl is one of the mammalian genes that codes for functions that affect dark-adapted retinal sensitivity. The results of this study and past studies suggest that the pearl gene's action on light sensitivity is predominantly within the retina and before (distal to) the ganglion cells.

Luminous efficiency functions by heterochromatic brightness matching for a wide range of retinal illuminance.

The present photopic photometric system is based on the CIE photopic relative luminous efficiency function V(λ), most of whose data were obtained by the flicker photometry. In recent years, however, it is pointed out that the CIE V(λ) does not necessarily represent the spectral sensitivity for the brightness perception. In the present experiment, the relative luminous efficiency functions were determined by the heterochromatic brightness matching method with a 2° visual field at fovea at the various retinal illuminance levels of 1 troland through 1000 trolands. At illuminance levels higher than 10 trolands, all the relative luminous efficiency curves showed a broader shape than the CIE V(λ). In some observers the relative luminous efficiency curves became broader with increasing the retinal illuminance. The present experimental results sugges that the brightness perception is contributed from the opponent-color channels.

The spectral sensitivities of isolated human color mechanisms determined from contrast evoked potential measurements

Previous attempts to measure human spectral sensitivity curves by physiological methods have not yielded results with the precision and over a sufficiently wide intensity range to enable useful predictions to be made about the fine details of color vision. In the present experiment we have used a contrast evoked response technique to measure a set of spectral sensitivities whose quality is comparable to that of psychophysically obtained data. For this purpose a visual stimulus was prepared that would presumably be seen as a pattern by only one color mechanism. The EP data obtained from one rod-monochromat correspond well with the CIE 1951 scotopic relative luminous efficiency function, whereas the data from normal and dichromatic subjects resemble several of Stiles' πμ mechanisms. At the long wavelength end of the visible spectrum the relative peak sensitivities and the shapes of the spectral sensitivity functions closely agree with Stiles' π4 and π5 mechanisms. The spectral sensitivity of the short wavelength mechanism had the form of either the π1 or π3 mechanism. The dichromat results can be fitted by the same mechanisms. The long wavelength mechanism of a protanope resembled π4 and that of a deuteranope π5.

An Experimental Determination of the Maximum Spectral Luminous Efficacy of Radiation

An experimental determination of the maximum spectral luminous efficacy of radiation has been made. The method uses luminous intensity standard lamps calibrated in "World mean candela 1952", thermopiles calibrated by absolute radiometers of electrical substitution type and filters of which the spectral transmittance is approximately proportional to the relative spectral luminous efficiency. An average value of 683 lm/W has been obtained, and the result is compared with that obtained at the NPL.

Application du perimetre statique de goldmann au releve topographique des seuils differentiels de luminance pour de petits objets colores projetes sur un fond blanc: I—Principes, calibrage de l'appareil et etude comparative de groupes de sujets normaux d'ages differents çois.

The authors first review some fundamental notions concerning the increment thresholds of an isochromatic or heterochromatic object of small angular extent projected on a large luminous background. The topography of such thresholds can be studied by means of Goldmann's static perimeter, of which the basic features and the spectrophotometric calibration are described. The examination of the relative achromatic sensitivities to white, blue, green and red objects along the horizontal meridian of 68 normal eyes, which were subdivided in three groups of different mean ages, allows us to recognise marked differences amongst these relative sensitivities according to eccentricity and to age; these variations are put into relationship with modifications of the spectral curve of relative luminous efficiency.

The effect of age upon colour vision—II. changes with age in light transmission of the ocular media

Data on colour-matching and the relative luminous efficiency of selected spectral wavelengths are given for some 400 observers. Both sets of data are found to be significantly correlated with observer age. The results have been compared with the effects of known and postulated age-changes in light transmission through the ocular media. It is concluded that the lens is the principal source of the observed age variations and the results also show that the macular pigment is not a significant variable with age. Finally, evidence is given which suggests that light-scattering may be the main physical cause of age-changes in light-transmission properties of the ocular media.