Lock-in Thermal Imaging Research Articles

Investigating a Lock-In Thermal Imaging Setup for the Detection and Characterization of Magnetic Nanoparticles.

Magnetic hyperthermia treatments utilize the heat generated by magnetic nanoparticles stimulated by an alternating magnetic field. Therefore, analytical methods are required to precisely characterize the dissipated thermal energy and to evaluate potential amplifying or diminishing factors in order to ensure optimal treatment conditions. Here, we present a lock-in thermal imaging setup specifically designed to thermally measure magnetic nanoparticles and we investigate theoretically how the various experimental parameters may influence the measurement. We compare two detection methods and highlight how an affordable microbolometer can achieve identical sensitivity with respect to a thermal camera-based system by adapting the measurement time. Furthermore, a numerical model is used to demonstrate the optimal stimulation frequency, the degree of nanomaterial heating power, preferential sample holder dimensions and the extent of heat losses to the environment. Using this model, we also revisit some technical assumptions and experimental results that previous studies have stated and suggest an optimal experimental configuration.

Lock-In-Thermography, Photoemission, and Time-Resolved GHz Acoustic Microscopy Techniques for Nondestructive Defect Localization in TSV

Through silicon via (TSV) is the most promising technology for vertical system integration and novel 3-D chip architectures. Reliability and quality assessment necessary for process development, root-cause analysis, and manufacturing require appropriate nondestructive testing techniques to achieve high processing yield and reliability. This paper presents two advanced approaches for nondestructive localization of defects in TSVs. The first method investigated here was lock-in thermal imaging by thermography and photoemission microscopy to inspect and localize electrical shorts within the 3-D geometry of the TSV insulation liner. In addition, filling defects in the TSVs have been inspected using acoustic microscopy in the gigahertz frequency band in time and spectral domains.

Research on finite element analysis of the infrared grating lock-in thermal imaging method

Infrared grating lock-in thermal test is a kind of infrared nondestructive testing methods with the combination of grating incentive and infrared lock-in thermal technology. This method is adopted to realize the vertical crack detecting inside the components. There is no related research up to now by using a grating which changes according to sine rule to the defects detection. In this paper, the numerical simulation of this method is carried out, and the finite element analysis process is introduced in detail. Results show that the choice of appropriate detection frequency and level speed is the key for the infrared grating lock-in method to detect. Our study verifies the feasibility of effective detection for superficial cracks in the film.

Defect Detection in Solid-State Battery Electrolytes Using Lock-In Thermal Imaging

Defective regions in battery materials often generate excess or non-uniform heat profiles during operation. Here, we discuss lock-in thermography as a high-sensitivity, spatially-resolved, and non-destructive technique to characterize defects and guide the targeted optimization of new battery materials and cell designs. As an example, we thermally image all-solid-state cells with β-Li3PS4 electrolyte, showing point-like heat signatures that correlate with cell breakdown. Based on the current/voltage cycling characteristics and electrochemical impedance spectroscopy, we attribute heating at the breakdown sites primarily to resistive current flow through dendrites. To assist in enabling wider application of lock-in thermography to emerging battery materials, we discuss several parameters necessary to optimize this technique, including the influences of surface thermal emissivity, thermal diffusivity, and lock-in modulation frequency.

A lock-in thermal imaging setup for dermatological applications.

Lock-in thermal imaging is a thermographic method that is widely used in the nondestructive testing of materials. The technique allows detecting under the sample surface, small variations of the thermophysical properties in a noninvasive and noncontact manner. Surprisingly, this method has, to our knowledge, never been used in dermatology although it is particularly suited. We present in this article the first lock-in thermal imaging setup dedicated to dermatological applications. The apparatus uses a temperature-modulated airflow to periodically stimulate the skin surface. The infrared images recorded by a high sensitive camera are demodulated according to the digital lock-in principle to compute a phase and amplitude image. First results obtained on benign skin lesions are presented. The images allow to detect small variations of the tissue thermophysical properties like for example, perfusion variations. Lock-in thermal imaging has the ability to reject disturbing thermal signals coming from subcutaneous tissues. The localization of the lesions is more accurate due the suppression of the lateral heat spreading. Lock-in thermal imaging is a promising method for the detection of lesions exhibiting modified thermophysical properties compared to the surrounding healthy skin.

Lock-in thermal imaging for the early-stage detection of cutaneous melanoma

This paper theoretically evaluates lock-in thermal imaging for the early-stage detection of cutaneous melanoma. Lock-in thermal imaging is based on the periodic thermal excitation of the specimen u...

Lock-in thermal imaging for the early-stage detection of cutaneous melanoma: A feasibility study

This paper theoretically evaluates lock-in thermal imaging for the early-stage detection of cutaneous melanoma. Lock-in thermal imaging is based on the periodic thermal excitation of the specimen under test. Resulting surface temperature oscillations are recorded with an infrared camera and allow the detection of variations of the sample׳s thermophysical properties under the surface. In this paper, the steady-state and transient skin surface temperatures are numerically derived for a different stage of development of the melanoma lesion using a two-dimensional axisymmetric multilayer heat-transfer model. The transient skin surface temperature signals are demodulated according to the digital lock-in principle to compute both a phase and an amplitude image of the lesions. The phase image can be advantageously used to accurately detect cutaneous melanoma at an early stage of development while the maximal phase shift can give precious information about the lesion invasion depth. The ability of lock-in thermal imaging to suppress disturbing subcutaneous thermal signals is demonstrated. The method is compared with the previously proposed pulse-based approaches, and the influence of the modulation frequency is further discussed.

Improvement of the non-destructive evaluation of plasma facing components by data combination of infrared thermal images

To increase the reliability of non-destructive examinations of plasma facing components (PFC), we present steps in order to make data combination in this study. The industrial issue is the inspection of manufacturing quality of these components which must support a very high-heat flux in Tokamaks. The experimental study was conducted on trial components for the Wendelstein 7X stellarator using two benches of infrared thermal imaging equipment. The first bench measures the surface temperature with an internal excitation of the components. The second bench uses a lock-in thermal imaging method. The data fusion method makes use of the Dempster–Shaffer theory of evidence. We show that we can improve the decision making for the quality diagnostic. This study could be generalized to other combinations of non-destructive tests for current Tokamaks or those under development like the future ITER reactor.