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.
Instead of natural exposing tests in atmosphere environment, we use artificial accelerated weathering apparatus to simulate solar radiation in ageing tests. Xenon arc lamps are most widely used to simulate spectral distribution of the sun in chambers. According to JJF1525-2015 Calibration Specification for Irradiance of Artificial Accelerated Weathering Apparatus of Xenon Arc Lamp, there are three methods to detect the irradiance: radiometer method, spectroradiometer method and standard lamp method. In this paper, we compare three methods and focus on the spectroradiometer method. Because different wavelength ranges need different radiometers, the best method to calibrate the irradiance in ageing tests is spectroradiometer method. By experiments, we verify the irradiance correspondence between 300nm~400nm and 340nm or 420nm to test the accuracy of spectroradiometer. We also study the factors affecting the irradiance calibration by spectroradiometer. At last we conclude that spectroradiometer is more suitable for irradiance calibration in different ageing tests and provide guidance for daily calibration.
With the development of LED technology research, more and more UV LED light sources have been used in UV curable coatings industry, instead of traditional UV lamps. Compared with the traditional UV fluorescent lamps, UV LEDs have many advantages, such as single peak, more energy saving, longer life, less thermal diffusivity. In the process of actual application, we need to monitor the intensity and energy of UV LED light sources regularly; therefore it is very important to make sure that the ultraviolet energy meter we adopted is accurate. In this paper, we firstly introduce our UV energy meter calibration device. We obtain the relative spectral distribution of UV LEDs and traditional curing UV light sources through spectrometer. By the analysis of spectral differences between the two, combined with the standard ultraviolet energy meter spectral response curve, we improve the measurement method to adapt to UV LED energy meters calibration. In this paper, the attention in the relevant calibration method is put forward for the characteristics of UV LEDs and the corresponding measurement uncertainty analysis is also evaluated to provide guidance for daily calibration.
Specular gloss is the perception by an observer of the mirror-like appearance of a surface. The primary gloss standard and glossmeter of China is maintained in Shanghai Institute of Measurement and Testing Technology (SIMT), which were originally developed in 1998. Recently, the instrument has been updated in several aspects, such as source arm, optical system and sample holder. The experiments and intercomparison measurements have been performed. The measurement results validate the measurement accuracy of our improved instrument.
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
Specular gloss is the perception by an observer of the mirror-like appearance of a surface. Specular gloss is usually measured by a glossmeter, which can be calibrated by a group of gloss plates according to JJG 696-2015. The characteristics of a gloss meter include stability, zero error, and error of indication. The characteristics of a gloss plate include roughness and spectral transmissivity of a high gloss plate, spectral reflectivity of a ceramic gloss plate. The experiment results indicate that calibration of both gloss meters and gloss plates should be carefully performed according to the latest verification regulation in order to reduce the measurement error.