Stefan Datcu

Infrared emissivity measurement device : principle and applications

Infrared emissivity is a necessary parameter for computing models to predict road surface status and pavement temperature irrespective of the weather situation. In this work a new experimental device based on the indirect method was developed for the measurement of surface emissivities. The surface is exposed to modulated isotropic infrared radiation. The intensity reflected by the surface of the sample in a given direction is measured by a detector operating in the spectral range 1–40 µm. This large spectral range allows measurement of the total hemispheric emissivity defined in this case as emissivity. The effect of the temperature modulation frequency, surface composition and surface roughness on the emissivity measurements was investigated. The results show good ability of the device for the determination of emissivities at room temperature.

Focal plane array infrared camera transfer function calculation and image restoration

Infrared images often present distortions induced by the measurement system. Image processing is thus an essential part of infrared measurements. A distortion model based on a convolution product is presented. The analytical form of the convolution kernel has been obtained from an image formation theory, along with an analysis of the sampling of the focal plane array camera detectors matrix. Image restoration is an ill-posed problem, and its solution can be obtained using regularization methods. In this work, image restoration is performed using a variation of Tikhonov regularization that makes use of the particular form of the convolution kernel matrix, which is built as a block-circulant matrix that admits a diagonal form in the 2-D Fourier space. The restoration procedure is used to restore a knife-edge infrared source image.

Parametric estimation of thermoradiative properties of materials based on harmonic excitation

A simple device for the measurement of emissivity, thermal conductivity, and diffusivity of opaque materials is described. The measurement method is based on the use of a harmonic excitation of a material sample plate. The front surface of the sample is heated periodically and its temperature is measured using a thermocouple. The sample back surface temperature is obtained by infrared thermography. Half of the sample back surface is covered by a black paint of known emissivity used as a reference to compute the sample surface directional emissivity. Thermal conductivity and diffusivity are simultaneously identified from both real and imaginary parts of experimental and theoretical heat transfer functions. Results are presented for a thermally thick sample of PVC, where the sample thickness is greater than the thermal diffusion length. The identified thermophysical properties are in agreement with literature values and reproducible results are obtained. Moreover, some limitations of the method are consider...

Monitoring acupressure stimulation effects by infrared thermography

Acupressure is a healing therapy that provides stimulation without needle by applying any pressure to the meridians of traditional Chinese acupuncture (the most important branch of the tTraditional Chinese medicine). This article presents an application of the infrared thermography to the thermal reactivity of Human body skin due to the acupressure stimulation. To survey an in vivo human skin surface, during the feasibility and material validity test, we will discuss the different sources of uncertainties and slants bound to the measurement by infrared thermography, such as the skin surfaces emissivity, the noise and the drift of the camera as well as the influence of the radiance emitted by the ambient surroundings. The main aim of this work is to highlight in infrared an objective evidence of the acupuncture points by infrared thermography under acupressure stimulation defined by the traditional Chinese acupuncture, by refining infrared thermography measuring methods. And finally twelve healthy acupuncture–naïve volunteers of our University participated to this scientific experimentation: a single-blinded in vivo trial “formula, placebo and sham” session.

Measurement of Thermophysical Properties by Two Different Methods and Study of Their Uncertainties

Thermophysical parameters of a known PVC (polyvinylchloride) sample were investigated by two different measurement methods. An active infrared thermography method (flash method) and a peri odic method were used for simultaneous characterization of thermal conductivity, diffusivity, effusivity and specific heat at room temperature, along with their corresponding statistical uncertainties. The results were compared with values from the literat ure, and show that the two measurement methods are complementary: thermal diffusivity was better estimated with the flash method than with the periodic method; on the contrary, the thermal conductivity uncertainty obtained using the flash method is more im portant. On the other hand, the measurement time is shorter for the flash method.

Regularization Method in Infrared Image Processing

Abstract Infrared images often present distortions induced by the measurement system. Thus, image processing is a vital part of infrared measurements. A distortion model based on a convolution product is presented. Image restoration is an ill-posed problem and its solution can be obtained using regularization methods. In this paper, image restoration is performed using a variation of Tikhonov regularization that makes use of the particular form of the convolution kernel matrix, which is built as a block-circulant matrix that admits a diagonal form in the two-dimensional Fourier space. The restoration procedure is used to restore a knife-edge infrared source image.