Infrared thermography transforms the thermal energy, emitted by objects in the infrared band of the electromagnetic spectrum, into a visible image. This feature represents a great potentiality to be exploited in many fields, but this technique is still not adequately enclosed in industrial instrumentation because of a lack of adequate knowledge; at first sight, it seems too expensive and difficult to use. The aim of the present paper is to shortly overview existing work and to describe the most relevant experiences devoted to the use of infrared thermography in three main fields, i.e. thermo-fluid dynamics, technology and cultural heritage, which have been performed in the department the authors belong to. Results may be regarded from two points of view, either as validating infrared thermography as a full measurement instrument, or as presenting infrared thermography as a novel technique able to deal with several requirements, which are difficult to perform with other techniques. This study is also an attempt to give indications for a synergic use of the different thermographic methods and sharing experiences in the different fields.

http://iopscience.iop.org/article/10.1088/0957-0233/15/9/R01/pdf

Recent advances in the use of infrared thermography

Many different thermal, optical, and thermal/optical carbon analysis methods for organic carbon (OC), elemental carbon (EC) or black carbon (BC) have been applied throughout the world to evaluate visibility and the Earth’s radiation balance. Dozens of intermethod and interlaboratory comparison studies have been conducted. Several of these studies are catalogued and summarized here. BC or EC concentrations are found to differ by up to a factor of 7 among different methods; factor of 2 differences are common. Differences between methods are not consistent among comparison studies, with some methods showing higher BC for one set of samples and lower BC for other sets relative to a common benchmark. The absorption efficiency relating light absorption (babs) to EC that is derived from collocated optical and chemical measurements can vary by a factor of 10, depending on the collocated babs and EC measurement methods. Future intermethod and interlaboratory comparisons must include components that seek to understand the causes of these differences.

/pdf/summary-of-organic-and-elemental-carbon-black-carbon-26jr0dlofz.pdf

Summary of Organic and Elemental Carbon/Black Carbon Analysis Methods and Intercomparisons

The Rosencwaig-Gersho equation for the photoacoustic signal is recast in a manner that emphasizes the crucial role thermal wave interference plays in the production of the photoacoustic signal. This formalism is then used to suggest a technique for extracting thermal information from the structure in the photoacoustic signal resulting from thermal wave interference. Experimental measurements illustrating this technique are presented.

/pdf/thermal-wave-interferometry-a-potential-application-of-the-1faxj22e0o.pdf

Thermal wave interferometry: a potential application of the photoacoustic effect.

1 Introduction- 2 Ionizing Radiation Computed Tomography- 3 Thermal Imaging- 4 Microwave Imaging- 5 Ultrasonic Imaging- 6 Nuclear Magnetic Resonance- 7 Neutron Imaging- References- List of Notations- Color Plates

Nondestructive Characterization and Imaging of Wood

The Design and Manufacture of Biomedical Surfaces

The Colorado State University Aerosol Workshop provided an excellent opportunity to obtain various particulate samples collected on filters. Our results indicate that the photoacoustic technique is preferable to the transmission technique (integrating plate method) for ambient samples with low-filter loadings since the presence of a nonabsorbing scattering aerosol (ammonium sulfate) only slightly perturbs the photoacoustic signal and significantly affects the transmitted signal. Measurements indicate that the photoacoustic signal depends not only on the energy absorbed from the incident beam but also on the existence of thermal wave interference effects and, especially for heavily loaded filters, on the presence of a nonabsorbing scattering aerosol.

Monitoring particulate carbon collected on Teflon filters: an evaluation of photoacoustic and transmission techniques

A widely used nondestructive technique for detecting particulate carbon collected on filters takes advantage of the unique optical properties of elemental carbon by measuring the amount by which a beam of light is attenuated after passing through or reflecting from a field loaded filter. Another absorptive method is photoacoustic detection, a process which may be potentially more advantageous and accurate than optical attenuation for ambient analyses. Since ambient samples contain nonabsorbing particles which scatter light much more effectively than carbon, it is important to examine these detection schemes while using carefully controlled synthetic sample of laboratory generated carbon. In this Letter we report on the generation of a set of weighed carbon calibration samples and the use of these samples to compare photoacoustic signals with measurements using the well-established method of optical attenuation in an environment free of perturbations caused by the highly scattering particles typically observed in ambient samples. We illustrate

C. A. Bennett

Papers

Thermal wave interferometry: a potential application of the photoacoustic effect.

Monitoring particulate carbon collected on Teflon filters: an evaluation of photoacoustic and transmission techniques

Photoacoustic detection of carbonaceous particles

Photoacoustic observation of thermal wave interference effects in thin samples.