Desenvolvimento de um sistema de imageamento usando a tomografia por coerÃncia Ãptica no domÃnio temporal e de Fourier

AUTOR(ES)

Bernardo de Barros Correia Kyotoku

DATA DE PUBLICAÇÃO

2006

RESUMO

In this dissertation, we describe the basic theory and details of the implementation of three experimental optical coherence tomography systems, two in the time domain and one in the spectral (Fourier) domain. Optical coherence tomography (OCT) is a non invasive optical imaging method, capable of producing cross-sectional images of materials and biological tissues. The OCT technique is based on the interference of two low coherence beams, in which the longitudinal spacial resolution is determined by spectral bandwidth of the source, and the depth penetration in the sample is a function of the scattering and absorption coefficients. In the systems developed in the work, we used as ligth source to shine a free space Michelson interferometer a Titanium-saphire laser, where the spectral bandwidth was broadened by nonlinear effects in a optic fiber to 50 nm centered at 800 nm, from which we calculated a logitudional resolution of 5.6 mm. In the systems operating in the time domain, the beam was sent to a free space Michelson interferometer. The sample was placed in the end of one interferometerâs arm, while in the other we used two delay lines (non simultaneously). In one of the cases, the delay line consisted on a mirror mounted on a linear translator controlled by a computer. In the second case, we introduced a Fourier delay line, composed by a diffraction grating, a lens, a mirror mounted over galvo driver, and a fixed mirror. The sample was fixed on a base that was translated laterally during the data acquisition. In the detection system, the signal was electronically preprocessed and digitalized. The whole system detection and image generation was developed using Labview programming environment. The time acquisition for a single depth scan was 24 s and 50 ms for the first a second setups, respectively. In the system operating in the Fourier domain, the delay line was replaced by a fixed mirror and the interference signal was collected by a spectrometer. A new program was developed in Labview to control the lateral translation and image acquisition, and a acquisition time for a single depth scan of 500 ms was achieved. The sensitivity was 98 dB for a incident power on the sample of 1 mW. The new system can also be remotely controlled, including over the internet, for data acquisition. As application examples, the developed system was used to generate images of human tooth in vitro, the acquired images were very satisfactory when compared to analysis made on optical microscope or other results described in the literature

ASSUNTO(S)

fisica tco interferometria de baixa coerÃncia tÃcnicas de imageamento imaging techniques optical coherence tomography oct low coherence interferometry tomografia por coerÃncia Ãptica

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