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The paper presents the assessment of equivalence of the spectral radiance scales in the wavelength range from 250 to 2500 nm, reproduced at the national metrology institutes of Korea (KRISS), China (NIM), and Russia (VNIIOFI), carried out in the framework of international comparisons. The common set of three tungsten strip lamps was used as an artefact. Based on a series of blind measurements of the lamps spectral radiance performed at each laboratory alternately, the reference value of the comparison was determined at each wavelength as a weighted mean of the measured data of three laboratories. The degree of equivalence of each laboratory was then calculated as the deviation of the measurement data of that participant from the reference value. A data analysis method was proposed for calculating the degree of equivalences and their uncertainties. The method is based on processing spectral radiance ratios, rather than differences, which allows eliminating the influence of a result of one particular participant to results of other laboratories. The comparison results confirm the equivalence of spectral radiance scales of all the laboratories within their expanded uncertainties (k = 2) except a few wavelength points.

An upper-air simulator (UAS) has been developed at the Korea Research Institute of Standards and Science (KRISS) to study the effects of solar irradiation of commercial radiosondes. In this study, the uncertainty in the radiation correction of a Vaisala RS41 temperature sensor is evaluated using the UAS at KRISS. First, the effects of environmental parameters including the temperature (T), pressure (P), ventilation speed (v), and irradiance (S) are formulated in the context of the radiation correction. The considered ranges of T, P, and v are −67 to 20 ∘C, 5–500 hPa, and 4–7 m s−1, respectively, with a fixed S0=980 W m−2. Second, the uncertainties in the environmental parameters determined using the UAS are evaluated to calculate their contribution to the uncertainty in the radiation correction. In addition, the effects of rotation and tilting of the sensor boom with respect to the irradiation direction are investigated. The uncertainty in the radiation correction is obtained by combining the contributions of all uncertainty factors. The expanded uncertainty associated with the radiation-corrected temperature of the RS41 is 0.17 ∘C at the coverage factor k=2 (approximately 95 % confidence level). The findings obtained by reproducing the environment of the upper air by using the ground-based facility can provide a basis to increase the measurement accuracy of radiosondes within the framework of traceability to the International System of Units.

An upper-air simulator (UAS) has been developed at the Korea Research Institute of Standards and Science (KRISS) to study the effects of solar irradiation of commercial radiosondes. In this study, the uncertainty of the radiation correction of a Vaisala RS41 temperature sensor is evaluated using the UAS at KRISS. First, the effects of environmental parameters including the temperature (T), pressure (P), ventilation speed (v), and irradiance (S) are formulated in the context of the radiation correction. The considered ranges of T, P, and v are −67 to 20 °C, 5–500 hPa, and 4–7 m·s−1, respectively, with a fixed S0 = 980 W·m−2. Second, the uncertainties in the environmental parameters determined using the UAS are evaluated to calculate their contribution to the uncertainty in the radiation correction. In addition, the effects of rotation and tilting of the sensor boom with respect to the irradiation direction are investigated. The uncertainty in the radiation correction is obtained by combining the contributions of all uncertainty factors. The expanded uncertainty associated with the radiation correction for the RS41 temperature sensor is 0.119 °C at the coverage factor k = 2 (approximately 95 % confidence level). The findings obtained by reproducing the environment of the upper air by using the ground-based facility can provide a basis to increase the measurement accuracy of radiosondes within the framework of traceability to the International System of Units.

Results from KSTAR powder injection experiments, in which tens of milligrams of boron nitride (BN) were dropped into low-power H-mode plasmas, show an improvement in wall conditions in subsequent discharges and, in some cases, a reduction or elimination of edge-localized modes (ELMs). Injected powder is distributed by the plasma flow and is deposited on the wall and, over the course of several discharges, was observed to gradually reduce recycling by 33%, and decrease both the ELM amplitude and frequency. This is the first demonstration of the use of BN for ELM mitigation. In all of these experiments, an Impurity Powder Dropper (IPD) was used to introduce precise, controllable amounts of the materials into ELMy H-mode KSTAR discharges. The plasma duration was between 10 s and 15 s, I p = 500 kA, B T = 1 . 8 T, P NBI = 1 . 6 MW, and P ECH = 0 . 6 MW. Plasma densities were between 2 and 3 × 1 0 19 m−3. In all cases, the pre-fill and startup gas-fueling was kept constant, suggesting that the decrease in baseline D α emission is in fact due to a reduction in recycling. The results presented herein highlight the viability of powder injection for intra-shot and between-shot wall conditioning.

We present an experimental method to determine color appearance shifts under high-dynamic-range conditions. A couple of light booths with variable luminance provide high-dynamic-range luminance conditions, and a perceptual color shift between the two booths is determined using color appearance matching. For red, green, yellow, and blue groups of four surface color samples, color shifts were measured for nine subjects under a dual illumination at background luminance levels of $100\,\,{{\rm cd/m}^2}$100cd/m2 and $4700\,\,{{\rm cd/m}^2}$4700cd/m2. We observed significant perceptual hue shifts toward blue with magnitudes of 2.5 to 3.9 and 5.0 to 6.9 CIELAB units, for the red and green samples, respectively, and decreases in chroma for most samples when changed from low to high luminances.

In case the primary realization of the spectral responsivity scale is not conducted at all target wavelengths but at only a small part of them, one needs to extrapolate values at the specific wavelengths to an extended range. In this work, we present a fully experimental procedure to extrapolate a single value of spectral responsivity at 633 nm into the whole working wavelength range (250–1100) nm of Si photodiodes. It is based on spectral responsivity comparison between a Si trap detector and a low-noise equivalent power pyroelectric detector of nearly flat spectral response. For this purpose, we developed a setup specialized to compare a Si-trap detector of dc-current output with a pyroelectric detector of ac-voltage output by using a modulated probing light source and a monitoring technique. To keep the probing light chopped even for the dc-photocurrent readout, we adopted a low chopping frequency of 4 Hz and a triggered readout for the Si-trap detector, which leads to a speedy comparison between the Si-trap detector and the pyroelectric detector. For the reference pyroelectric detector, we characterized the spectral absorptivity of the black-coating and the nonlinearity of the lock-in amplifier readout. Compiling all the required information, the spectral responsivity of the Si trap detector could be measured with the minimum uncertainty of 0.3% (k = 2), which was validated by comparing with that of our previous method based on a numerical extrapolation.

One of the challenges in temperature measurements in the upper air using a radiosonde is the correction of solar radiation effects. A prerequisite for the correction is in situ measurements of solar radiation. In this study, a new technique for the measurement of solar irradiation followed by the temperature correction was developed using dual temperature sensors with different emissivities. The principle is that the radiation intensity is calculated by using the temperature difference between two thermistors coated with different materials (one with graphite and the other with aluminium) and then the irradiance obtained is used for the correction. As a first stage, the effect of air pressure on the temperature correction process using dual thermistors was examined. The temperature difference between the two sensors was found to be linearly proportional only to the irradiance up to 360 W m−2, regardless of air pressure from 10 to 1000 hPa at room temperature. This provides a way to calculate the irradiance by simply measuring the temperature difference between the two sensors. The calculated irradiance showed a difference of less than 45 W m−2 (13% of the maximum irradiance) compared to the irradiance measured with a calibrated pyranometer. The extended uncertainty of the calculated irradiance was 53.5 W m−2 (coverage factor k = 2). A reference temperature sensor in the shade was used to obtain a correction formula as a function of air pressure and calculated irradiance. When the temperature was corrected using the calculated irradiance, the extended uncertainty of the corrected temperature was 0.98 K (k = 2).

We demonstrate that the individual single pulse of a nano-second laser can be used to measure the spectral responsivity of photovoltaic detectors. With this new scheme, the relative spectral responsivity of a photodiode can be determined from the spectral reflectance of the surface of a pyroelectric detector. We also developed the adequate data acquisition procedure, which can eliminate systematic errors caused by the nonlinear pulse response. The method is experimentally demonstrated for Si and Ge photodiodes in a wide wavelength range from 420 nm to 1600 nm and verified by comparison with the method using a CW source.

We present the design of a radiometer that can simultaneously measure both centroid wavelength and irradiance of a light source without recording its spectrum, when the light source has a finite spectral bandwidth. It consists of two photodiodes separated with a beam splitter in its basic construction, which can be referred to as a dual-photodiode radiometer. This radiometer is calibrated by measuring the spectral responsivities of two photodiodes against the spectral irradiance at the input aperture. The concept of the simultaneous measurement is valid under the condition that the spectral responsivities are linear against wavelengths within the spectral bandwidth of the source to be tested. The feasibility and expected accuracy are analyzed by numerical simulations and experimentally tested for the realization of a UVA irradiance meter, which shows an agreement within 0.2 nm and 0.6% for centroid wavelength and irradiance, respectively, with other reference instruments.

Single photon detectors, which are capable of ultra-sensitive detection in a low light level, have been widely used in a variety of applications such as remote sensing, biochemical science, and quantum information science [1–4]. In particular, the rapid development of quantum information science has greatly improved the development of single photon detectors because it played a key role in achieving successful results in quantum key distribution and quantum communication [2–4].

We report on the calibration of the relative spectral responsivity of the reference radiation thermometer, model LP4, which is used for the experimental realisation of the international temperature scale of 1990 above 960 °C at the Korea Research Institute of Standards and Science. The relative spectral responsivity of LP4 is measured by using a monochromatic source consisting of a super-continuum laser and a double-grating monochromator. By monitoring the wavelength of the output beam directly with a calibrated wavelength-meter, we achieved a high-accuracy measurement of spectral responsivity with a maximum wavelength error of less than 3 pm, a narrow spectral bandwidth of less than 0.4 nm, and a high dynamic range over 8 decades. We evaluated the contributions of various uncertainty components of the spectral responsivity measurement to the uncertainty of the temperature scale based on a practical estimation approach, which numerically calculates the maximal effects of the variations of each component. As a result, we evaluate the uncertainty contribution from the spectral responsivity measurement to the temperature scale to be less than 64 mK (k = 1) in a range from 660 °C to 2749 °C for the LP4 with a filter at 650 nm.

We present a practical calibration method of the detection efficiency (DE) of single photon detectors (SPDs) in a wide wavelength range from 480 nm to 840 nm. The setup consists of a GaN laser diode emitting a broadband luminescence, a tunable bandpass filter, a beam splitter, and a switched integrating amplifier which can measure the photocurrent down to the 100 fA level. The SPD under test with a fibre-coupled beam input is directly compared with a reference photodiode without using any calibrated attenuator. The relative standard uncertainty of the DE of the SPD is evaluated to be from 0.8% to 2.2% varying with wavelength (k = 1).

We present the concept of and the procedure for realizing the primary scale of the spectral responsivity based on an absolute cryogenic radiometer at the Korea Research Institute of Standards and Science (KRISS). A detailed error and uncertainty analysis is performed by calibrating the standard detectors in the wavelength range from 300 nm to 1000 nm. The relative expanded uncertainty of the spectral responsivity calibration for a Si trap detector is 0.06% at 632.8 nm and 0.4% for other wavelengths (k = 2). The calibration results are validated by comparing with the results from a theoretical model of quantum efficiency for a transmission-type trap detector.

Photoluminescence (PL) quantum efficiency (QE) is one of the important parameters to characterize photoluminescent materials especially for lighting and display application. Under a few assumptions, IEC standard (IEC62607-3-1) provides two methods of high simplicity and moderate accuracy with an integrating sphere for absolute measurement of QE named 'collimated incident light method (CILM)' and 'diffuse incident light method (DILM)', respectively [1,2]. However, the simplification unavoidably causes systematic errors, which could be significant in certain cases of sphere reflectance or material properties. In this paper, we numerically investigate the systematic errors that can occur in the standardised methods employing Monte Carlo ray-tracing simulation and also present their correction method based on additional measurement to estimate diffusivity of sample reflectance at excitation wavelength and absorption of sample at PL emission wavelength.

Korea Research Institute of Standards and Science (KRISS), National Institute of Metrology (NIM), and All-Russian Research Institute for Optical and Physical Measurements (VNIIOFI) started an international comparison on the spectral radiance over the spectral region from 250 nm to 2500 nm in 2012 and completed all measurements in 2016. The aim of this comparison was to assess the equivalence of the spectral radiance scales between the three laboratories. This comparison was carried out according to the technical protocol listed in the KCDB under the identifier APMP.PR-S6. The difference from the reference value (RV) and its uncertainty of each participant of this comparison were calculated by using the relative difference model recommended by the Guidelines for CCPR Comparison Report Preparation. A method (ratio method) to calculate the difference from the RV and its uncertainty was proposed to eliminate the pilot effects involved in the relative difference model. In the ratio method, spectral radiance ratios to the pilot and geometric means were used to calculate the difference from the RV and its uncertainty of each participant. Results of this comparison analyzed using the ratio method showed that differences from the RV of all participants were within their uncertainties (k = 2) except a few wavelengths for each participant. Main text To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCPR, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

We demonstrate that the individual single pulse of a nano-second laser can be used to measure the quantum efficiency of photovoltaic detectors. With this new scheme, the relative quantum efficiency of a photodiode can be determined from the spectral reflectance of the surface of a pyroelectric detector. We also developed the adequate data acquisition procedure, which can eliminate systematic errors caused by the nonlinear pulse response. The method is experimentally demonstrated for Si and Ge photodiodes in a wide wavelength range from 420 nm to 1600 nm and verified by comparison with the method using a CW source.

We present a novel instrumentation scheme for measuring the two-dimensional distribution of spectral reflectance based on the spectral imaging technique. It takes digital spectral images of a test sample using a LED-based monochromatic integrating sphere source and a monochrome CCD camera. We developed a calibration algorithm to assign the digital counts of the images to the reflectance values at each wavelength. The measurement uncertainty is evaluated to be less than 1.5% (k = 2) for high-reflectance samples (with reflectance ≥0.4) and less than 3% (k = 2) for low-reflectance samples (with reflectance

A laser diode-based flowmeter based on the infrared absorption method that can measure in situ micro flow rates from 0.2 to 20 ml h−1 was developed. A 1450 nm laser absorbed in water was irradiated to form a heated spot at 0 mm, and the temperature was measured upstream and downstream of the heated spot. The flow rate was measured by the temperature difference obtained by two diode lasers and photodetectors upstream and downstream of the heated spot. We measured the temperature profile of the flow rate by changing the temperature measurement position and the heating laser energy upstream and downstream of the heated spot, and compared the measurements with the simulation results. As the flow rate increased, the temperature profile shifted downstream, and the measured temperature upstream and downstream were analyzed according to the flow rate. The flow measurement range was adjusted according to the temperature measurement position. Increasing the energy of the heating laser also improved the measurement accuracy in the lower flow range. The developed flowmeter was calibrated by the gravimetric method, and the deviation and measurement uncertainty according to the flow rate were obtained. The maximum measurement uncertainty was 6.8% at a 1 ml h−1 flow rate, and the minimum measurement uncertainty was 1.78% at 8 ml h−1. Thus, it was confirmed that the flow rate can be measured through the temperature difference gauged using a simple diode laser set. Using the laser diode-based flowmeter developed in this study, one can measure the flow rate in situ without injecting contaminants, such as particles, for measurements without cutting the piping. In addition, it can be manufactured in a miniaturized form at a low cost, and thus, it can be used for multi-drug infusion analysis, semiconductor process monitoring, etc.

We demonstrate the measurement of detection efficiency, the probability for the successful detection of a single photon incident on a detector, in a wide wavelength range from 250 nm to 1000 nm. The method is based on the responsivity comparison of two detectors by using a tunable monochromatic light source at a radiant power controlled to the pico-Watt level. As the reference detector, a photodiode with a switched integrating amplifier is used, whose spectral responsivity is calibrated at a photo-current level of pico-Ampere. A fibre-based spatial filter is used to form a beam focus that is focused to a diameter of less than 100 µm at the detector under test. The typical uncertainty of the detection-efficiency measurement for a Si-based single photon avalanche photodiode is evaluated to be less than 1% as a relative standard uncertainty (k = 1), which is currently limited by the characteristics of the tunable source.

We present an instrumental realization of linearity measurement of optical detectors based on flux addition of two light-emitting diodes (LEDs) in an integrating sphere. The instrument measures the linearity ratios at pre-defined photocurrent levels according to the algorithm which eliminates the drift effect of LED flux (Shin D J et al 2005 Metrologia 42 154). As a result, the non-linearity correction factors for detector responsivity are determined with their relative standard uncertainties ranging from 2 × 10−5 to 6 × 10−5 (k = 1) for photocurrent ranges from 10−8 A to 10−3 A. By changing the type of LEDs, the wavelength dependence of non-linearity can also be measured, which is demonstrated at 390 nm, 670 nm and 750 nm for a Si photodiode used as a transfer standard for spectral responsivity scale comparisons.

The radiation temperature scale for a pyroelectric detector based thermal infrared thermometer with its spectral response from 8??m to 14??m was realized in the temperature range from 0??C to 232??C by using four fixed-point blackbodies (ice, Ga, In and Sn). The Planck version of the Sakuma?Hattori equation was used to interpolate the scale between the fixed-point temperatures that are corrected by considering a size-of-source effect (SSE). The expanded uncertainties (k?=?2) of the scale were estimated to be 108?mK for ice, 99?mK for Ga, 175?mK for In and 234?mK for Sn.

This work introduces a switched integration amplifier (SIA)-based photocurrent meter for femtoampere (fA)-level current measurement, which enables us to measure a 107 dynamic range of spectral responsivity of photometers even with a common lamp-based monochromatic light source. We described design considerations and practices about operational amplifiers (op-amps), switches, readout methods, etc., to compose a stable SIA of low offset current in terms of leakage current and gain peaking in detail. According to the design, we made six SIAs of different integration capacitance and different op-amps and evaluated their offset currents. They showed an offset current of (1.5-85) fA with a slow variation of (0.5-10) fA for an hour under opened input. Applying a detector to the SIA input, the offset current and its variation were increased and the SIA readout became noisier due to finite shunt resistance and nonzero shunt capacitance of the detector. One of the SIAs with 10 pF nominal capacitance was calibrated using a calibrated current source at the current level of 10 nA to 1 fA and at the integration time of 2 to 65,536 ms. As a result, we obtained a calibration formula for integration capacitance as a function of integration time rather than a single capacitance value because the SIA readout showed a distinct dependence on integration time at a given current level. Finally, we applied it to spectral responsivity measurement of a photometer. It is demonstrated that the home-made SIA of 10 pF was capable of measuring a 107 dynamic range of spectral responsivity of a photometer.

We report on a self-guided operation of a green-pumped singly resonant continuous-wave optical parametric oscillator with a bulk MgO-doped PPLN crystal. It is achieved by increasing the OPO cavity length beyond the stability boundary so that the OPO can only oscillate with formation of a thermally induced waveguide inside the crystal. The effects of the thermal waveguide on the OPO performance are studied by measuring output power characteristics at different cavity lengths. Improvement of spatial mode quality and stability of output power by self-guiding is demonstrated. Measurement of temporal characteristics proves that formation of the waveguide originates from the photo-thermal effect in the nonlinear crystal by absorption of pump power.

This paper presents the development of a compact charge-coupled detector (CCD) spectrometer. We describe the design, concept and characterization of VNIR linear variable edge filter (LVEF)- based mini-spectrometer. The new instrument has been realized for operation in the 300 nm to 850 nm wavelength range. The instrument consists of a linear variable edge filter in front of CCD array. Low-size, light-weight and low-cost could be achieved using the linearly variable filters with no need to use any moving parts for wavelength selection as in the case of commercial spectrometers available in the market. This overview discusses the main components characteristics, the main concept with the main advantages and limitations reported. Experimental characteristics of the LVEFs are described. The mathematical approach to get the position-dependent slit function of the presented prototype spectrometer and its numerical de-convolution solution for a spectrum reconstruction is described. The performance of our prototype instrument is demonstrated by measuring the spectrum of a reference light source.

We describe a novel method to measure the relative spectral responsivity of Si and Ge photovoltaic detectors from 250 nm to 1700 nm based on a tunable nano-second pulsed optical parametric oscillator (OPO).

We developed a 62 m-baseline transmissometer to establish the national standard on visibility observation. A 75 W, white LED with 3000 K CCT1 is used for transmitter, and two photometers for receiver and monitor.

We introduce a new prototype instrument for measuring the 2D spatially resolved distribution of spectral reflectance based on new spectral imaging technique. The instrument captures digital spectral images of a test sample using a pulsed LED-based monochromatic source and a scientific grade CCD array and special data acquisition algorithm is used to extract the useful image data corresponding to the target application. In earlier version of this instrument, we used a commercial CCD camera with 8-bit ADC without any cooling stages which has many drawbacks. In this work, we have modified our setup by introducing a new scientific grade CCD; deep-cooled interline transfer sensor with 16-bit ADC and electronic shutter. With this new instrument we could achieve a higher accuracy, higher spatially resolved measurements, higher dynamic range, mush better sensitivity and lower uncertainty and we could avoid many sources of errors in the old setup. With one wavelength scan, one can get the full reflectance data of the sample under test which saves a lot of time in comparison with conventional methods. This new instrument is promising with a potential of applications in the field of optical material testing.

Along with the low temperature plasmas operated at low pressure, the information on electrons is particularly valuable and indispensable in elucidating unrevealed discharge mechanisms and various physical phenomena occurring in atmospheric pressure plasmas. Due to the limited availability of simple electron diagnostics for atmospheric pressure plasmas, discharge properties were studied using theoretical models with relevant approximations. In this presentation, we report a simple electron density (n e ) and temperature (T e ) diagnostics with high temporal and spatial resolution based on neutral bremsstrahlung due to the electron and neutral atom interaction in the ultraviolet and visible range emitted from atmospheric pressure plasmas. For an argon radio-frequency capacitive discharge, we investigated the electron properties under various plasma conditions. Capacitive discharges in argon and helium show different continuum spectra, and we notice that driving frequency plays an important role in the electron properties. Time-resolved emission spectra and the corresponding n e and T e during one rf cycle of the argon capacitive discharge were obtained. The result showed that T e varied from 2.3 eV to 3.0 eV while electron density did not change significantly. Furthermore, a simple diagnostics for two-dimensional distribution of time-averaged T e using a commercial digital camera with optical filters is presented.

The melting temperatures of three metal-carbon eutectics, rhodium-carbon, platinum-carbon and ruthenium-carbon, were measured by four national metrology institutes: the National Research Laboratory of Metrology (NRLM, Japan, now the National Metrology Institute of Japan, NMIJ), the National Institute of Metrology (NIM, China), the National Measurement Laboratory (NML, Australia), and the Korea Research Institute of Standards and Science (KRISS, Rep. of Korea). The same cells were measured using different radiation thermometers and different high-temperature carbon-tube furnaces by the four institutes, on their independently realized temperature scales. The results were compared to examine the performance of these high-temperature fixed points and to determine their melting and freezing temperatures on the International Temperature Scale of 1990 (ITS-90). The measured fixed-point temperatures were all within 0.4 °C of the calculated mean for each cell, and were within each laboratory's estimated uncertainties. The mean values were (1656.8 ± 0.6) °C, (1737.4 ± 0.3) °C and (1953.0 ± 0.4) °C, respectively, for the melting plateaus of the Rh-C, Pt-C and Ru-C eutectic points, with the uncertainties given for k = 2.

We present experimental realization and validation of the six-port design of integrating sphere photometers for total luminous flux measurement, which significantly improves the uniformity of spatial response compared to the conventional single-port design. Construction, measurement procedure, and data acquisition of the realized instrument with a radius of 1 m are described. Measurement of the spatial response distribution function confirms the expected effect of improving the uniformity by averaging the signals from the six detection ports. The related spatial mismatch error is determined to be less than 1.4% for all the realistic cases of beam angles and directions of a test lamp mounted in the vicinity of the sphere center. As a result, we confirm that the realized six-port instrument allows us to eliminate the complicated spatial mismatch correction procedure by adding a relative standard uncertainty of only 1.4/3%≈0.81%, which offers a great practical benefit for testing solid-state lighting products of various beam characteristics.

We present an instrumentation solution for measurement of normalized spectral responsivity of digital imaging sensors and cameras. The instrument consists of multiple light-emitting diodes (LEDs), a single-grating monochromator, and a small-size integrating sphere. Wavelength tuning is achieved by a proper selection of LED in accordance with the monochromator setting in a range from 380 to 900 nm. High spectral purity with a bandwidth of 5 nm is realized without using double gratings and order-sorting filters. Experimental characteristics and calibration of the instrument are described with the related error and uncertainty sources. The performance is demonstrated by measuring a monochrome charge-coupled device and a trichromatic complementary metal-oxide-semiconductor device. The measurement uncertainty is evaluated to be less than 1% (k=2) except several wavelengths with low LED power.

We present a calibration method of UV index meters under a solar simulator based on a spectroradiometer as reference. The reference spectroradiometer is a double-grating-based type that can measure the erythemal effective irradiance and the global UV index in a wavelength range from 250 nm to 450 nm. After calibration of its wavelength scale and spectral irradiance scale by using the KRISS standard lamp, we applied the spectroradiometer to measure the reference value for calibrating broadband UV index meters under a solar simulator. The uncertainty of the spectroradiometer for measuring the reference value for the global UV index is evaluated to be 5% as a relative expanded uncertainty (k = 2).

We derive analytic formulas describing the temporal behavior of the laser-induced incandescence (LII) signal in both case of the heat transfer governed by radiation and collision. Using these formulas, we can describe the temporal behavior of the LII signal and determine the dimension of nanosize particles in low-pressure plasma. Simple calibration procedure is introduced for quantitative measurement of the particle size with the LII technique.

Cuticular nanostructures found in insects effectively manage light for light polarization, structural color, or optical index matching within an ultrathin natural scale. These nanostructures are mainly dedicated to manage incoming light and recently inspired many imaging and display applications. A bioluminescent organ, such as a firefly lantern, helps to out-couple light from the body in a highly efficient fashion for delivering strong optical signals in sexual communication. However, the cuticular nanostructures, except the light-producing reactions, have not been well investigated for physical principles and engineering biomimetics. Here we report a unique observation of high-transmission nanostructures on a firefly lantern and its biological inspiration for highly efficient LED illumination. Both numerical and experimental results clearly reveal high transmission through the nanostructures inspired from the lantern cuticle. The nanostructures on an LED lens surface were fabricated by using a large-area nanotemplating and reconfigurable nanomolding with heat-induced shear thinning. The biologically inspired LED lens, distinct from a smooth surface lens, substantially increases light transmission over visible ranges, comparable to conventional antireflection coating. This biological inspiration can offer new opportunities for increasing the light extraction efficiency of high-power LED packages.

We describe a novel method to measure the relative spectral responsivity of detectors based on a pulsed OPO tunable from 210 nm to 2000 nm. Si and InGaAs photodiodes are compared to a pyro-electric detector as Reference (REF) at each laser pulse from the OPO with a duration of several ns and a repetition rate of 1 kHz based on a beam splitter and single-pulse data acquisition.

We propose an integrating sphere photometer with six detection ports for total luminous flux measurement, which significantly improves the uniformity of spatial response compared to the conventional single-port detection design. Numerical simulations based on the geometric radiative transfer equation show that a spatial response distribution function of the new design is uniform within 2% with respect to all spatial directions. The related spatial mismatch error is calculated to be less than 0.3% for all the realistic cases of angular intensity distribution of a test lamp. As a result, the new design practically eliminates the spatial mismatch error of an integrating sphere photometer, so that a high-accuracy measurement can be achieved without the complicated spatial mismatch correction procedure.

We present a measurement uncertainty evaluation for emission color and luminance of displays. The calibration procedures and the measurement uncertainties of a CCD-based spectroradiometer and a filter-type luminance meter are discussed. As evaluation examples, a Commission Internationale de l' Eclairage illuminant A, a liquid-crystal display with a light-emitting diode backlight, and a liquid-crystal display with a cold-cathode fluorescent lamp backlight are evaluated. The uncertainties in Commission Internationale de l' Eclairage 1931 (x,y) chromaticity coordinates are determined to be in a range from 0.0020 to 0.0050 (k=2). The uncertainties in luminance are obtained from 4.8% to 8.5% by using the spectroradiometer, while the filter-type luminance meter shows the uncertainties from 1.1% to 1.6% (k=2).

This work presents an alternative approach for preparing photometric standard LEDs, which is based on a novel functional seasoning method. The main idea of our seasoning method is simultaneously monitoring the light output and the junction voltage to obtain quantitative information on the temperature dependence and the aging effect of the LED emission. We suggested a general model describing the seasoning process by taking junction temperature variation and aging effect into account and implemented a fully automated seasoning facility, which is capable of seasoning 12 LEDs at the same time. By independent measurements of the temperature dependence, we confirmed the discrepancy of the theoretical model to be less than 0.5 % and evaluate the uncertainty contribution of the functional seasoning to be less than 0.5 % for all the seasoned samples. To demonstrate assigning the reference value to a standard LED, the CIE averaged LED intensity (ALI) of the seasoned LEDs was measured with a spectroradiometer-based instrument and the measurement uncertainty was analyzed. The expanded uncertainty of the standard LED prepared by the new approach amounts to be 4 % ~ 5 % (k=2) depending on color without correction of spectral stray light in the spectroradiometer.