Minimum Detectable Temperature Difference Research Articles

Development and application of infrared imaging check and evaluation system

According to the parameters of various kinds of infrared imaging equipment was performance full automatic detection and evaluation of research in this paper. The evaluation system will to accuracy, slit function (SRF), minimum resolvable temperature difference (MRTD), minimum detectable temperature difference (MDTD) and noise equivalent temperature difference (NETD) and other parameters as the basis, the establishment of infrared imaging evaluation system database, to convergence of digital interface to realize automatic detection and evaluation of infrared imaging device, solving the technical problem of performance evaluation of grid infrared imaging equipment, ensure the accuracy of condition based maintenance for power transmission system.

Research on Performance Evaluation and Optimization Theory for Thermal Microscope Imaging Systems

Infrared imaging theory is an important theoretical basis for the design of infrared imaging systems, but there is no research on infrared imaging theory for designing thermal microscope imaging systems. Therefore, we studied the performance evaluation and optimization theory of thermal microscope imaging systems. In this paper, we analyzed the difference in spectral radiant flux between thermal microscope imaging and telephoto thermal imaging. The expression of signal-to-noise ratio of the output image of the thermal microscope imaging systems was derived, based on the analysis of the characteristics of thermal microscope imaging. We studied the performance evaluation model of thermal microscope imaging systems based on the minimum resolvable temperature difference and the minimum detectable temperature difference. Simulation and analysis of different detectors (ideal photon detector and ideal thermal detector) were also carried out. Finally, based on the conclusion of theoretical research, we carried out a system design and image acquisition experiment. The results show that the theoretical study of thermal microscope imaging systems in this paper can provide reference for the performance evaluation and optimization of thermal microscope imaging systems.

Processing and fusion of passively acquired, millimeter and terahertz images of the human body

A passive, millimeter wave (MMW) and terahertz (THz) dual-band imaging system composed of 94 and 250 GHz single-element detectors was used to investigate preprocessing and fusion algorithms for dual-band images. Subsequently, an MMW and THz image preprocessing and fusion integrated algorithm (MMW-THz IPFIA) was developed. In the algorithm, a block-matching and three-dimensional filtering denoising algorithm is employed to filter noise, an adaptive histogram equalization algorithm to enhance images, an intensity-based registration algorithm to register images, and a wavelet-based image fusion algorithm to fuse the preprocessed images. The performance of the algorithm was analyzed by calculating the SNR and information entropy of the actual images. This algorithm effectively reduces the image noise and improves the level of detail in the images. Since the algorithm improves the performance of the investigated imaging system, it should support practical technological applications. Because the system responds to blackbody radiation, its improvement is quantified herein using the static performance parameter commonly employed for thermal imaging systems, namely, the minimum detectable temperature difference (MDTD). An experiment was conducted in which the system’s MDTD was measured before and after applying the MMW-THz IPFIA, verifying the improved performance that can be realized through its application.

Minimum detectable gas concentration performance evaluation method for gas leak infrared imaging detection systems.

Thermal imaging technology is an effective means of detecting hazardous gas leaks. Much attention has been paid to evaluation of the performance of gas leak infrared imaging detection systems due to several potential applications. The minimum resolvable temperature difference (MRTD) and the minimum detectable temperature difference (MDTD) are commonly used as the main indicators of thermal imaging system performance. This paper establishes a minimum detectable gas concentration (MDGC) performance evaluation model based on the definition and derivation of MDTD. We proposed the direct calculation and equivalent calculation method of MDGC based on the MDTD measurement system. We build an experimental MDGC measurement system, which indicates the MDGC model can describe the detection performance of a thermal imaging system to typical gases. The direct calculation, equivalent calculation, and direct measurement results are consistent. The MDGC and the minimum resolvable gas concentration (MRGC) model can effectively describe the performance of "detection" and "spatial detail resolution" of thermal imaging systems to gas leak, respectively, and constitute the main performance indicators of gas leak detection systems.

1H-MRS internal thermometry in test-objects (phantoms) to within 0.1 K for quality assurance in long-term quantitative MR studies

Many magnetic resonance test-object properties are temperature-dependent, with typical temperature coefficients of approximately 2-3% K(-1). Therefore, to achieve consistent quality assurance measurements to within 1%, test object temperatures should ideally be known to within 0.3 K. Proton magnetic resonance spectroscopy has previously been used to estimate accurately absolute tissue temperature in vivo, based on the linear temperature dependence of the chemical shift difference between water and temperature-stable reference metabolites such as N-acetylaspartate. In this study, this method of 'internal thermometry' in quality assurance test-objects was investigated, and in particular the value of sodium 3-(trimethylsilyl)propane-1-sulfonate (DSS) as a chemical shift reference was demonstrated. The relationship between the DSS-water chemical shift difference (sigma, expressed in ppm) and temperature tau (in K) was shown to be tau = 764.55 (+/-5.05) - 97.72 (+/-1.05) sigma (286 <or= tau <or= 309 K). Internal thermometry in MRI test-objects is feasible and straightforward, using readily available (1)H-MRS pulse sequences and standard spectroscopy evaluation packages, with a minimum detectable temperature difference of 100 (+/-20) mK.

Evaluation of thermal cameras for non-destructive thermal testing applications

Thermal cameras are nowadays often used in industry and science for non-destructive thermal testing (NDTT). There have been published, by the American Society for Testing of Materials, two standards that present detailed measurement procedures of the minimum resolvable temperature difference (MRTD) and the minimum detectable temperature difference (MDTD) of commercial thermal cameras for NDTT applications. However, the standards provide only very general guidelines about the use of the measured MRTD and MDTD values for evaluation of thermal cameras for NDTT applications. Precise methods that enable evaluation of a thermal imager for NDTT application on the basis of measurement results of the MRTD and the MDTD are presented in this paper. The methods enable estimation of probabilities of detection, orientation, recognition and identification of thermal anomalies generated by flaws in the materials imaged.

Testing of Thermal Imagers for Nondestructive Thermal Testing Applications

Abstract One of the important areas of application of commercial thermal imagers is nondestructive thermal testing. An analysis of two standards published by the American Society for Testing and Materials describing measurement procedures of the minimum resolvable temperature difference (MRTD) and the minimum detectable temperature difference (MDTD) was made in this paper. It was shown that in the case of modern thermal imagers, the measurement results of these parameters carried out according to the ASTM recommendations may be unreliable. Proposals to update the standards and to enable accurate measurement of the parameters mentioned above are presented. A laboratory setup for measurement of the MRTD and the MDTD that fulfills requirements of the proposals is described. Measurement results of the parameters for a modern commercial imager according to updated procedures are presented. Erratum to this paper appears in 28(6).

A temperature difference-to-frequency converter using resistance temperature detectors

A novel temperature difference-to-frequency (TD/F) converter using two platinum resistance temperature detectors (RTDs) has been developed. The resistance difference of two RTDs is converted into a DC current to control the simulated inductor, which is designed so that its inductance is inversely proportional to the square of the current. The simulated inductor forms the resonant circuit of a Colpitts oscillator and hence the oscillation frequency becomes directly proportional to the resistance difference. A conversion sensitivity of 16 Hz/ degrees C and a residual nonlinearity of less than 2% over the temperature difference range of 35 degrees C to 155 degrees C are obtained by the prototype converter which oscillates at 667 Hz at a 51 degrees C temperature difference. The minimum detectable temperature difference is estimated to be +or-0.013 degrees C. The power dissipations in the RTDs are about 2 mu W. The proposed converter, except for the RTDs, can be fabricated in a monolithic IC form by scaling the component values. >

Derivation of various temperature detection limits for thermal imagers under field conditions

The frequently quoted temperature differences NETD (noise equivalent temperature difference), MRTD (minimum resolvable temperature difference) and MDTD (minimum detectable temperature difference) are actually laboratory figures of merit describing a major property of thermal imaging devices and radiometers. These quantities cannot be simply applied when imaging or measuring in the field since, in deriving the various relations, the atmospheric transmittance has been assumed to be unity and the temperature differences have been assumed to be of the order of one degree centigrade or less. In the field, however, the transmittance encountered is strongly wavelength dependent and often low. The temperature differences might also be of the order of ten degrees centigrade or more. For such field situations the SNR is reassessed in a more exact way than for laboratory conditions, permitting the derivation of practical NETD f, MRTD f and MDTD f. The various derivations and the applicability of the results are dealt with.

Submillimetre and millimetre response of Josephson junctions mounted in a waveguide

Wide-band detection characteristics have been measured for niobium point contact Josephson junctions, mounted in a 1.30 × 0.65 mm 2 rectangular waveguide. Spectral response measurements have been made for different mounting positions in the waveguide as a function of the normal state junction resistance and the backshort position. For the absolute response we measured a minimum detectable external temperature difference (Δ T min) syst ≃ 10mK/Hz 1 2 with a (NEP) syst ≃ 5 × 10 −15 W/Hz 1 2 , at ν ≃ 200GHz.

Performance characteristics of a 300-GHz radiometer and some atmospheric attenuation measurements

A 300-GHz Dicke-type superheterodyne radiometer receiver was used for measurements of atmospheric attenuation of electromagnetic waves over an open path at frequencies near 300 GHz. The average measured values of horizontal attenuation at 304 GHz and 316 GHz, presumably due to atmospheric water vapor absorption, were, respectively, 3.35 dB/km and 5.55 dB/km per g/m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> of water vapor density. Absorption variations at 304 GHz with respect to water vapor density were shown in the measured results. The variation of the effective zenith sky temperature with respect to atmospheric water vapor density was also determined. The minimum detectable temperature difference <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">(\Delta T)_{min}</tex> , was obtained by measuring the rms value of noise in the receiver output. The best value achieved was <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3.16\deg</tex> K. Based on this result, the receiver noise figure and the mixer conversion loss were determined indirectly. The results were 31.4 dB and 22.9 dB, respectively. A blackbody radiation source served to calibrate the radiometer.

Radiometric measurement of atmospheric absorption at 600 Gc/s

Atmospheric absorption in the 600-Gc/s region was measured throughout the actual atmosphere by means of a DICKE-type superheterodyne radiometer receiver using second harmonic mixing. The average measured value of horizontal attenuation was approximately 34 dB/km/g/m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> . The variation of water vapor absorption with respect to water vapor density was also indicated in the measured results. The minimum detectable temperature difference (ΔT) <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">MIN</inf> was obtained by calculating the rms value of output deflection and the use of the calibration curve for the radiometer. The best value achieved was 5.2°K. From this result, the radiometer receiver noise figure and the mixer conversion loss were able to be determined indirectly. The results were 33.2 dB and 26.4 dB, respectively. A thermal calibrator was used to adjust and calibrate the radiometer, and as a source of radiation for the measurement program.