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Projeto ótico com controle Arduíno para medição do índice de refração de tecidos biológicos
| Name: | Description: | Size: | Format: | |
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| 5.15 MB | Adobe PDF |
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Abstract(s)
A medição do índice de refração de tecidos biológicos é crucial para compreender as suas propriedades óticas e apoiar aplicações clínicas baseadas na interação luz-tecido. Os métodos laboratoriais convencionais, embora precisos, apresentam custos elevados e elevada complexidade. Este trabalho tem como objetivo desenvolver e validar um protótipo experimental de baixo custo, controlado por Arduino e com interface em Python, para a determinação automática do índice de refração através do ângulo de Brewster. O sistema idealizado e montado, para além da utilização do Arduino Uno, integra também motores de passo, drivers, um fotodetetor com amplificação, e uma estrutura mecânica idealizada, que permite realizar varrimentos angulares precisos com aquisição em tempo real de diferentes intensidades dos feixes lasers utilizados. A validação inicial foi realizada com recurso a um semicírculo de acrílico, o qual permitiu encontrar o ângulo pretendido, confirmando a viabilidade e a exatidão do protótipo montado, com resultados muito próximos dos valores de referência da literatura. Posteriormente foram analisadas amostras de tecido biológico, recorrendo em concreto ao peito de frango. Com o sistema montado foi possível verificar a influência da anisotropia, ou seja, as fibras do tecido orientadas na horizontal e vertical apresentaram índices de refração distintos, em concordância com estudos prévios existentes na literatura. Os testes de feixe laser, com comprimentos de onda na zona do vermelho e azul revelaram limitações, nomeadamente a ausência do mínimo de Brewster espetável no
vermelho, e intensidades demasiado baixas na zona do azul, inviabilizando as medições realizadas, já que não eram fiáveis. O feixe laser na zona do verde, permitiu obter valores fiáveis e com precisão.
Measuring the refractive index of biological tissues is crucial for understanding their optical properties and supporting clinical applications based on light-tissue interaction. Conventional laboratory methods, although accurate, are costly and highly complex. This work aims to develop and validate a low-cost experimental prototype, controlled by Arduino and with a Python interface, for the automatic determination of the refractive index using the Brewster angle. The system was designed and assembled using Arduino Uno that integrates stepper motors, drivers, an amplified photodetector, and a specially designed mechanical structure that allows precise angular scans with real-time acquisition of different intensities of the laser beams used. Initial validation was performed using an acrylic prism, which allowed the desired angle to be found, confirming the feasibility and accuracy of the assembled prototype, with results very close to the reference values in the literature. Subsequently, biological tissue samples were analyzed, specifically using chicken breast. With the assembled system, it was possible to verify the influence of anisotropy, that is, the horizontally and vertically oriented tissue fibers presented different refractive indices, in agreement with previous studies in literature. Laser beam tests, with wavelengths in the red and blue range, revealed limitations, namely the absence of the minimum Brewster angle in the red range and excessively low intensities in the blue range, rendering the measurements unreliable and therefore unusable. The laser beam in the green range provided reliable and accurate values.
Measuring the refractive index of biological tissues is crucial for understanding their optical properties and supporting clinical applications based on light-tissue interaction. Conventional laboratory methods, although accurate, are costly and highly complex. This work aims to develop and validate a low-cost experimental prototype, controlled by Arduino and with a Python interface, for the automatic determination of the refractive index using the Brewster angle. The system was designed and assembled using Arduino Uno that integrates stepper motors, drivers, an amplified photodetector, and a specially designed mechanical structure that allows precise angular scans with real-time acquisition of different intensities of the laser beams used. Initial validation was performed using an acrylic prism, which allowed the desired angle to be found, confirming the feasibility and accuracy of the assembled prototype, with results very close to the reference values in the literature. Subsequently, biological tissue samples were analyzed, specifically using chicken breast. With the assembled system, it was possible to verify the influence of anisotropy, that is, the horizontally and vertically oriented tissue fibers presented different refractive indices, in agreement with previous studies in literature. Laser beam tests, with wavelengths in the red and blue range, revealed limitations, namely the absence of the minimum Brewster angle in the red range and excessively low intensities in the blue range, rendering the measurements unreliable and therefore unusable. The laser beam in the green range provided reliable and accurate values.
Description
Keywords
refractive index biological tissues Arduino Brewster?s angle experimental prototype Índice de refração Tecidos biológicos Ângulo de Brewster Protótipo experimental