Parallel Vector Lock-In Thermal Wave IR Video Imaging of Microcracks in Cu Foils Deposited on Polyimide

Ahmed, T.; Kuo, P. K.; Favro, L. D.; Jin, Han; Thomas, R. L.; Woods, C.M.; Houston, G. L.

doi:10.1007/978-1-4613-0817-1_76

Cited by 2 publications

(2 citation statements)

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“…This technique is equivalent to 256 × 256 synchronized lock-in amplifiers detecting radiometric signals from adjacent pixels. A difference between previously reported lock-in methods (Ahmed et al 1989) is that our implementation does not require additional hardware for coherent processing of high-speed video data flow. However, significant computer RAM (up to 500 MB) is required for storage of digital image data recorded by the IR FPA camera.…”

Section: Amplitudementioning

confidence: 98%

Coherent thermal wave imaging of subsurface chromophores in biological materials

et al. 2002

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Thermal wave imaging of discrete subsurface chromophores in biological materials is reported using a phase sensitive coherent detection technique applied to recorded infrared (IR) images. We demonstrate that utilization of a periodically modulated laser source for thermal wave excitation and coherent detection applied to each pixel may be used to compute images of thermal wave amplitude and phase at the laser modulation frequency. In comparison to recorded IR images, the narrow-band detection technique significantly improves the quality of thermal wave amplitude images of subsurface chromophores in biological materials. Additionally, the technique provides phase information, which may be used to estimate chromophore depth in tissue. Application of the technique is demonstrated using tissue phantoms and in vivo biological models. We present a theoretical analysis and computer simulations that demonstrate the effect of tissue optical and thermal properties on thermal wave amplitude and phase. In comparison to the pulsed photothermal technique, coherent thermal wave imaging of subsurface chromophores in tissue for diagnostic applications allows reduction of peak incident laser fluence by as much as four orders of magnitude and is safer and more amenable to in vivo imaging.

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