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.
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.
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.
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.
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.
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.
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.
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.
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.
This paper studied the standard laser energy meter. A self calibration of the thermoelectric type standard laser energy meter is developed, which is provided with a suitable electric heater. It can be used to simulate and replace the equivalent thermal effect, and to realize the absolute measurement of the laser energy. Because the standard laser energy meter can bulk absorb laser radiation, it can bear higher laser energy density. The material absorption spectrum of the standard laser energy meter is relatively flat from the ultraviolet to the infrared, so it can be used for the measurement of laser energy at any wavelength. In addition, an electric calibration instrument is developed. The electric calibration instrument can be directly displayed or synchronous display by the digital frequency meter. The laser energy calibration device is composed of standard laser energy meter, pulsed laser source, monitoring system, digital multi meter and complete set of electric calibration system. Laser energy calibration device uses split beam detection method. The laser is divided into two beams by means of a wedge shaped optical beam splitter. A laser energy meter is used to monitor the change of the reflected light to reduce the influence of the output laser energy stability of the pulsed laser source, thereby improving the uncertainty of the calibration result. The sensitivity, correction factor and indication error of the laser energy meter can be calibrated by using the standard laser energy meter and the under calibrated laser energy meter to measure the transmission laser beam.
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.
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.
With the rapid development of China's economy, many industries have more requirements for UV light applications, such as machinery manufacturing, aircraft manufacturing using high power UV light for detection, IT industry using high power UV light for curing component assembly, building materials, ink, paint and other industries using high power UV light for material aging test etc. In these industries, there are many measuring instruments for high power UV irradiance which are need to traceability. But these instruments are mostly imported instruments, these imported UV radiation meter are large range, wide wavelength range and high accuracy. They have exceeded our existing calibration capability. Expand the measuring range and improve the measurement accuracy of UV irradiance calibration device is a pressing matter of the moment. The newly developed high power UV irradiance calibration device is mainly composed of high power UV light, UV filter, condenser, UV light guide, optical alignment system, standard cavity absolute radiometer. The calibration device is using optical alignment system to form uniform light radiation field. The standard is standard cavity absolute radiometer, which can through the electrical substitution method, by means of adjusting and measuring the applied DC electric power at the receiver on a heating wire, which is equivalent to the thermo-electromotive force generated by the light radiation power, to achieve absolute optical radiation measurement. This method is the commonly used effective method for accurate measurement of light irradiation. The measuring range of calibration device is (0.2~200) mW/cm<sup>2</sup>, and the uncertainty of measurement results can reached 2.5% (<i>k</i>=2).
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.
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.
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.
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.
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 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.
Bolometer is mainly used for measuring thermal radiation in the field of public places, labor hygiene, heating and ventilation and building energy conservation. The working principle of bolometer is under the exposure of thermal radiation, temperature of black absorbing layer of detector rise after absorption of thermal radiation, which makes the electromotive force produced by thermoelectric. The white light reflective layer of detector does not absorb thermal radiation, so the electromotive force produced by thermoelectric is almost zero. A comparison of electromotive force produced by thermoelectric of black absorbing layer and white reflective layer can eliminate the influence of electric potential produced by the basal background temperature change. After the electromotive force which produced by thermal radiation is processed by the signal processing unit, the indication displays through the indication display unit. The measurement unit of thermal radiation intensity is usually W/m<sup>2</sup> or kW/m<sup>2</sup>. Its accurate and reliable value has important significance for high temperature operation, labor safety and hygiene grading management. Bolometer calibration device is mainly composed of absolute radiometer, the reference light source, electric measuring instrument. Absolute radiometer is a self-calibration type radiometer. Its working principle is using the electric power which can be accurately measured replaces radiation power to absolutely measure the radiation power. Absolute radiometer is the standard apparatus of laser low power standard device, the measurement traceability is guaranteed. Using the calibration method of comparison, the absolute radiometer and bolometer measure the reference light source in the same position alternately which can get correction factor of irradiance indication. This paper is mainly about the design and calibration method of the bolometer calibration device. The uncertainty of the calibration result is also evaluated.
The measurement of the modulation transfer function (MTF) is one of the key steps in characterizing the signal transfer
characteristics of an imaging system as a function of spatial frequency in terms of linear response theory. Various
methods have been proposed to determine the MTF of an imaging system which are based on point, slit or edge images.
The slanted-edge method is the ISO 12233 standard for the MTF measurement of electronic still-picture cameras. In this
paper, the method is modified to avoid amplifying the noise during the derivative computation by performing
curve-fitting. In the experiments, we compare several different analytical function models for the ESF fitting and find
that Logistic (Fermi) function gives the best result.