The total luminous flux is one of the most important characteristics of LEDs. The total luminous flux measurement of traditional LEDs with low power (0.05W@20mA), low heat and single package must conform to the specifications of CIE 127: 2007 Measurement of LEDs. Compared to traditional low-power LEDs, the latest LEDs have higher power (1W@350mA), higher heat and exhibit more complex packages. Because of their own characteristics, high-power LEDs have put forward some new measurement requirements for standard light source, heat dissipation structure, special fixture and integrating sphere. Therefore, a new type of 2π standard light source has been designed and used for the total luminous flux calibration of high-power LEDs.
This paper focuses on the irradiance metrology of single LED. In reference to the latest domestic and international standard, the method is based on the current dissemination system of LED. We study on the similarities and differences between traditional radiation standard lamps and the LED light source. As a result, the color compensation factor is added and an accurate and reliable measurement system for single LED irradiation is established. The uncertainty of the measurement results is evaluated while the measurement results are obtained through experiments.
This paper briefly introduces the methods of calibrating the irradiance in the Xenon lamp aging test chamber. And the irradiance under ultraviolet region is mainly researched. Three different detectors whose response wave range are respectively UVA (320~400nm), UVB (275~330nm) and UVA+B (280~400nm) are used in the experiment. Through comparing the measuring results with different detectors under the same xenon lamp source, we discuss the difference between UVA, UVB and UVA+B on the basis of the spectrum of the xenon lamp and the response curve of the detectors. We also point out the possible error source, when use these detectors to calibrate the chamber.
The total luminous flux is one of the most important characteristics of a LED. According to the CIE standard, the luminous flux for LEDs can be measured by an integrating sphere equipped with a spectroradiometer. The luminous flux of LEDs has been measured in the 4π geometry, which is suitable for LEDs with different luminous intensity distributions. The results between NIM and SIMT validate our calibration ability. The experiments indicate that the standard LEDs and the measurement repeatability play important roles in the uncertainty analysis.
In the field of optical metrology, luminous flux is an important index to characterize the quality of light source. There are two kinds of method to measure it that one is light distribution surface method and the other is integrating sphere method. In the integrating sphere method, the baffle which is a key part of integrating sphere has important effects on the measurement results. The paper analyzes in detail the principle of an ideal integrating sphere. We change the relative position and shape of baffle inside the sphere during testing. By experiments, measured luminous flux values at different distances between the light source and baffle are obtained, which we used to take analysis of the effects of different baffle position and shape on the measurement. And then we obtain the optimum position and shape of baffle for luminous flux measurements. Based on the conclusion, we develop the methods and apparatus to improve the luminous flux measurement accuracy and reliability, which makes our unifying and transferring work of the luminous flux more accurate in East China and provides effective protection for our traceability system
This paper introduces standard diffusion reflection white plate method and integrating sphere standard luminance source method to calibrate the luminance parameter. The paper compares the effects of calibration results by using these two methods through principle analysis and experimental verification. After using two methods to calibrate the same radiation luminance meter, the data obtained verifies the testing results of the two methods are both reliable. The results show that the display value using standard white plate method has fewer errors and better reproducibility. However, standard luminance source method is more convenient and suitable for on-site calibration. Moreover, standard luminance source method has wider range and can test the linear performance of the instruments.
In this paper, a new system has been introduced for the calibration of lux meter. This apparatus is designed to use comparison method in high illumination based on integrating sphere source. Experiment has been performed in this apparatus. Meanwhile, the results are compared to that of the superposition method.
Specular gloss is the fraction of light reflected in the specular direction for specified incident and receptor apertures, it is the perception by an observer of the mirror-like appearance of a surface. The measurement of specular gloss consists of comparing the luminous reflectance from a test sample to that from a calibrated gloss standard which generally is a polished piece of black glass, under the same experimental conditions. Gloss is a dimensionless quantity whose accurate determination requires standardized experimental conditions such as spectral distribution of the incident beam of light, incident and viewing angles, and a gloss standard. The Shanghai Institute of Measurement and Testing Technology (SIMT) provides test service to calibrate gloss reference standards. This facility is built around a reference goniophotometer, containing an instrument that measures flux as a function of angles of illumination or observation and a primary gloss standard, which is a piece of three wedges of highly polished, high-quality optical glass. The system has an overall (<i>k</i>=2) uncertainty of 0.5 Gloss Unit(GU). The service offers calibration measurements of working gloss standards at the geometries of 20°, 60°, and 85°, in compliance with the ISO 2813 and the ASTM D523 documentary standards. This article describes a bilateral comparison of specular gloss scales between SIMT and the National Institute of Standards and Technology (NIST) that has been performed. The results of this comparison show agreement within the combined uncertainties for the measurement of specular gloss of highly polished black glass.
This paper focuses on traceability work on total luminous flux of single LED based on the direct camparison method applied for quantity transfer of incandescent lamps. During the test different color groups of LEDs have been chosen as standard to measure total luminous flux of sample LEDs. The test is accomplished in the current integrating sphere measurement system under specific conditions according to LED characteristics. As results obtained from the experiment, the uncertainties are also evaluated.
The specifications accuracy of ultraviolet, visible, near-infrared (UV-VIS-NIR) spectrometer may change after used for a period of time, due to optoelectronic devices inside and environment. It directly affects the accuracy of scientific research and product quality measurement. Therefore this requires that the instrument should be checked after working a period of time. How various specifications are checked? What is chosen as a standard to check? Which method is more reasonable? If we choose unreasonable standard and checking method, the instrument will lose its accuracy. All of these are described in this paper in detail.
An apparatus for determining the spectral response of large area solar cells based on filter method has been introduced. The spectral response of a solar cell is measured by irradiating it by means of a narrow-bandwidth light source at a series of different wavelengths covering its response range, and measuring the short-circuit current density and irradiance at each of these wavelengths. Experiments have been performed to analyze the factors which can affect the spectral response measurements such as the full width at half maximum (FWHM) of filters, the non-uniformity of monochromatic light. The results indicate that less FWHM of filters, more uniformity of monochromatic light will lead to a more accurate measurement.
A reference goniophotometer and primary standards for specular gloss established at the SIMT have been described, as well as the theory and measurement equations relevant to the measurements. The instrumentation, standards, and measurement techniques used to measure specular gloss have been described, including the illuminator, goniometer, receiver, sample-holding system and the characterization of the instrument. The new primary specular gloss standard and its characterization are presented.
A solar simulator is a device that provides illumination approximating natural sunlight. Solar simulators are classified as A, B or C for each of the three categories based on criteria of spectral distribution, irradiance non-uniformity on the test plane and temporal instability of irradiance. In this paper, we find that spectral match may change during the pulse of a pulsed solar simulator. In our experiments, a second PV device, which is placed at a fixed position outside the test area, has been used for monitoring the irradiance during the pulse and correcting the measurement results. We focus on the temporal instability measurements of pulsed solar simulators, especially for those whose irradiance changes rapidly during the time of data acquisition, and make a conclusion.