In the experiment of measuring the emissivity distribution characteristics by integrating sphere reflection method, the laser output power stability is an important guarantee for the accurate emissivity measurement. However, there is a lack of research on the influence of laser power stability on measurement results. Therefore, a measurement system for the infrared radiation source emissivity distribution characteristics is designed and built based on the complete hemispherical laser integrated reflection scheme in this paper. The stability of the laser light source subsystem is evaluated, and the laser power drift is corrected by means of a alternating measurement sequence. The experiment of measuring the flat plate radiation source emissivity distribution characteristics is carried out with a laser power of 3 W. The results show that the laser power shows a periodic drift and one period is about 70 s. The macroscopic power of the laser increases linearly throughout the measurement process. After correcting the laser power drift, the relative standard deviation of the flat plate radiation source is 0.56%, and the volatility is 2.99%. After drift correction, the measurement accuracy is improved by 28.2%.
We present a simple quad-band terahertz (THz) metamaterial absorber for perfect absorption. Unlike most reported absorbers, the proposed structure achieves perfect absorption based on high-order plasmon resonance, with the absorptivity of the first three peaks all >99.4 % . First, the resonance absorption mechanism of the absorber involving fundamental resonance mode and high-order resonance mode is analyzed in detail. Next, the sensing performance is also studied by changing the ambient refractive index, the numerical results show that the designed multiband metamaterial absorber is very sensitive to small changes in refractive index, and appears highly sensitive in its sensing performance. In particular, figure of merit of the last absorption peak reaches 26.6, which is far superior to most multiband metamaterial absorbers operating in the THz regime. The proposed simple structure not only greatly simplifies the fabrication, but also is insensitive to the polarization of incident waves. The results show that the quad-band metamaterial absorber has potential applications in sensing, imaging, detection, and other fields.
Fiber-optic temperature sensor based on thermo-chromic materials is a kind of effective facility to solve the problem of measuring temperature in the electrical power system. But the measuring range by this method is narrow, it is necessary to improve the measuring range by the means of append an attenuator. In this paper,based on traditional fiber optic temperature sensor , the purpose and principle of thermo-chromic optical fiber temperature sensing probe is introduced. The degree of attenuation of temperature which is obtained through ANSYS software thermal simulation is used as an evaluation index to make the choice of probe structure, and analyzes the result of simulation in detail. Finally, the functional between the temperature of heat source and the temperature of attenuator is fitted. So, this paper could be a reference or an example for the application of fiber-optic temperature sensor based on thermo-chromic materials.
In the view of the situation that single-sensor image cannot fully reflect the scene information efficiently. A fusion method of infrared and visible images based on discrete wavelet transform is presented and comparatively analyzed with traditional methods. Firstly, the wavelet multi-scale decomposition technique is applied to the source images that will be fused to give a series of sub-band coefficient. Feature extraction and weighted average with adaptive weighting factors are used to process the high-frequency coefficients. A strategy of the absolute value comparing is adopted to the low-frequency coefficients. Finally, the fusion image is reconstructed by multi-scale wavelet inversing transformation for low frequency and high frequency coefficients. Experimental results demonstrate that infrared and visible images can be more effectively fused by the algorithm presented than traditional methods.
KEYWORDS: Signal to noise ratio, Modulation transfer functions, Imaging systems, Charge-coupled devices, Spatial frequencies, Image quality, CCD image sensors, Modulation, Data conversion, Data processing
The Modulation Transfer Function (MTF) is a fundamental imaging system design specification and system quality metric often used in remote sensing. The MTF describes the attenuation of sinusoidal waveforms as a function of spatial frequency. Practically, MTF is a metric quantifying the sharpness of the reconstructed image. The Knife-Edge method is becoming widely applied for its advantage of simplified target and accurate computer calculation. Noise in CCD image system is inevitable, thus the SNR becomes a factor influencing the MTF measurement. In this paper, we build relationships between SNR, luminance and MTF. In conclusion, SNR is related with luminance levels linearly. SNR rises with increasing luminance. The higher SNR, the more curves conform to the theoretical MTF.
KEYWORDS: Temperature metrology, Black bodies, Data modeling, Thermometry, Mathematical modeling, Tungsten, Lamps, Transmission electron microscopy, Error analysis, Lithium
Aiming at the problems of temperature measurement and the defects of radiance thermometry theory, one method of spectral-based inferential measurement is proposed, which adopts the Empirical Risk Minimization (ERM) functional model as the temperature measurement model. Then, the radiance thermometry theory and inferential measurement technology are discussed comparatively. Temperatures of some targets, such and tungsten lamp and solar surface, are measured by spectral-based inferential measurement.
KEYWORDS: Calibration, Imaging devices, RGB color model, Camera shutters, Cameras, Measurement devices, Digital cameras, Light sources and illumination, Solids, Lithium
A method of calibration of imaging luminance measuring devices has been studied. By the device-independent color space transformation, the color image by digital camera could be converted to the CIE's absolute color space lab. Then, the calibration model is fitted between ln(L/t) and luminance. At last, luminance image is obtained and the dynamic range of luminance image could be adjusted by shutter speed.
In this paper, the compact spectrometer has been designed and implemented with concave grating. By using the holographic corrected concave grating, the compact spectrometer without movable parts, with a fixed grating and an array detector, could obtain a relative high spectral resolution in a wide spectral range. Then, the spectral resolution has been estimated by the slit function. The spectral resolution (ΔFWHM) is smaller than 5nm from 300nm to 1100nm. It is very suitable for photometry, colorimetry, and radiometry.
Pyromark 1200 (Tempil Co, USA), which is a type of high-temperature high-emissivity coating, is silicon-based with good thermal radiation performance. Its stably working condition is at the temperature range 589~922 K thus a wide range of applications in industrial, scientific research, aviation, aerospace and other fields. Infrared emissivity is one of the most important factors in infrared radiation characteristics. Data on infrared spectral emissivity of Pyromark 1200 is in shortage, as well as the reports on its infrared radiation characteristics affected by its spray painting process, microstructure and thermal process. The results of this research show that: (1) The coating film critical thickness on the metal base is 10μm according to comparison among different types of spray painting process, coating film thickness, microstructure, which would influence the infrared radiation characteristics of Pyromark 1200 coating. The infrared spectral emissivity will attenuate when the coating film thickness is lower or much higher than that. (2) Through measurements, the normal infrared radiation characteristics is analyzed within the range at the temperature range 573~873 K under normal atmospheric conditions, and the total infrared spectral emissivity of Pyromark 1200 coating is higher than 0.93 in the 3~14 μm wavelength range. (3) The result of 72-hour aging test at the temperature 673 K which studied the effect of thermal processes on the infrared radiation characteristics of the coating shows that the infrared spectral emissivity variation range is approximately 0.01 indicating that Pyromark 1200 coating is with good stability. Compared with Nextel Velvet Coating (N-V-C) which is widely used in optics field, Pyromark 1200 high-temperature coating has a higher applicable temperature and is more suitable for spraying on the material surface which is in long-term operation under high temperature work conditions and requires high infrared spectral emissivity.
As infrared zoom systems change the focal length continuously, remain images stability and keep good image quality during the process of zoom, it is widely applied to infrared navigation, infrared detection, infrared-guided etc vehicular and airborne area. In order to satisfy the growing demand of infrared continuous zoom system, a zoom ratio of ten times long-wave infrared continuous zoom optical system that based on an uncooled detector was designed. System guided by the zoom theory of positive groups of compensation, calculated the initial structure of the system and according to the system of optical parameters with using ZEMAX software for optical design did an aberration balance and optimized, then the optical system image quality was systematically analyzed and evaluated. The result showed that the modulation transfer function (MTF) was above 0.4 within the whole focal range at spatial frequency 16 lp/mm, the root mean square radius of maximum dispersion spot was smaller than a pixel dimension and it met the requirements of the system imaging quality when F/# was 2, continuous zoom range was from 40 mm to 400 mm and the image size was 12 mm. The design of the system realized the requirements of compact structure, large zoom ratio, easily assembled and excellent image quality to optical system for infrared imaging.
In recent years, technology of thermal imager and spectral imaging is becoming mature, and the application of them is
increased. The method is based on the blackbody radiation theory, make use of the infrared thermal imager to collect and
analysis the thermal images, distill the temperature value of different pixel of the thermal images, use Matlab to deal
blackbody radiation emitted curve fitting according with the temperature value of different pixels, and get the values of
the degree of radiation emitted at the same wavelength from the different pixels, then make spectral imaging (1μm~10μm) according to the values. At last, do analysis to spectral imaging of different spectral bands; discuss the limitations
of using this method to achieve spectral imaging.
Based on the development of infrared thermometry all over the world, a problem has been pointed out. Whenever
infrared thermometer has been used in measuring temperature, the field of full vision of target must be considered. Or
else there will be a mistake. In the thesis, base on the theory of infrared thermometer, we analyze the reasons of the error.
And we also deduce the theory equation of partial vision temperature measurement about infrared thermometry. In the
process of deduction, because of the other influences are not considered; so we get the approximate equation of partial
vision temperature measurement, based on measurement value we draw a compensatory curve to compensate the
equation of infrared thermometry. The curve has reflected the compensating effect well. In the end, we analyze the
reasons of error. We draw a conclusion that this method of partial vision temperature measurement is feasible. We
discuss the error which caused by distance and get a feasible method to correct the error.
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