Lei Lai

Research on calibration of lux meter based on integrating sphere source

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.

Research on the measurement of the ultraviolet irradiance in the xenon lamp aging test chamber

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 measurement of luminous flux for single LEDs

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.

Research on the calibration methods of the luminance parameter of radiation luminance meters

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.

The calibration of specular gloss meters and gloss plates

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.

Research on the calibration of ultraviolet energy meters

Ultraviolet (UV) radiation is a kind of non-lighting radiation with the wavelength range from 100nm to 400nm. Ultraviolet irradiance meters are now widely used in many areas. However, as the development of science and technology, especially in the field of light-curing industry, there are more and more UV energy meters or UV-integrators need to be measured. Because the structure, wavelength band and measured power intensity of UV energy meters are different from traditional UV irradiance meters, it is important for us to take research on the calibration. With reference to JJG879-2002, we SIMT have independently developed the UV energy calibration device and the standard of operation and experimental methods for UV energy calibration in detail. In the calibration process of UV energy meter, many influencing factors will affect the final results, including different UVA-band UV light sources, different spectral response for different brands of UV energy meters, instability and no uniformity of UV light source and temperature. Therefore we need to take all of these factors into consideration to improve accuracy in UV energy calibration.

Accuracy of a reference instrument for specular gloss measurements

Specular gloss is the perception by an observer of the mirror-like appearance of a surface. The measurement of specular gloss consists of comparing the luminous flux reflected from an object to that reflected from a gloss reference standard. The accuracy of specular gloss measurements depends not only on the characteristics of the instrument but also on the properties of the gloss reference standard. Experiments have been performed to analyze the possible sources of error such as gloss reference standard variation, photodetector linearity and measurement repeatability, which are three most important components of uncertainty. The results indicate that the instrument should be carefully examined before the specular gloss measurement in order to acquire a satisfied result.

Research on measurement of total luminous flux of single LED in direct comparison method

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.

Influencing factors and error analysis for specular gloss measurement

Specular gloss has been widely used to characterize the ability of a surface to reflect light specularly. Specular gloss is theoretically related to the physical properties of a surface, such as roughness, directionality and uniformity. Specular gloss, mainly determined by incident angle and refractive index of a surface, is a relative measurement quantity. Specular gloss is usually measured by a glossmeter. The topographical and optical properties of a surface have been analyzed on how to affect the measurements. The experiment results indicate that a less rough/flatter, more isotropic and more uniform surface will result in a more accurate measurement value. Therefore, physical properties of a surface must be carefully inspected before the specular gloss measurement in order to acquire a satisfied result.

Research on effects of baffle position in an integrating sphere on the luminous flux measurement

In the field of optical metrology, luminous flux is an important index to characterize the quality of electric light source. Currently, the majority of luminous flux measurement is based on the integrating sphere method, so measurement accuracy of integrating sphere is the key factor. There are plenty of factors affecting the measurement accuracy, such as coating, power and the position of light source. However, 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 use moving rail to change the relative position of baffle and light source inside the sphere. 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 on the measurement. By theoretical calculation, computer simulation and experiment, we obtain the optimum position of baffle for luminous flux measurements. Based on the whole luminous flux measurement error analysis, we develop the methods and apparatus to improve the luminous flux measurement accuracy and reliability. It makes our unifying and transferring work of the luminous flux more accurate in East China and provides effective protection for our traceability system.