Measurement of the topography, refractive index and thickness in tissues by mean of a chromatic confocal method

The chromatic confocal methods are attractive for various applications, such as imaging of biological samples and semiconductor materials. In this paper a chromatic confocal method to measure the topography, the refractive index and optical thickness of tissues is develop. The experimental model is based on the longitudinal chromatic aberration produced by a diffractive element. The setup is composed by a point polychromatic illumination system, a wavelength-height codification system of confocal microscopy and a spectral detection system. The illumination system has a broad and continuum spectrum and it is constituted by the combination of a high energy pulsed laser and an air-silica microstructured optical fibre. The first two systems form a wavelengths segment on the device output. The coding of the topography and the thickness is based in the spectral analysis of the reflected spectral components coming from the surface of the sample and the interphase of the organic membranes respectively. It mean that the most intense spectral components coming from every layer of the sample is identified. The measurement sensitivity is related to the width of the spectral response, which depends on the resolving power of the dispersive element and the detection system. The experimental results and a briefly discussion of the resolution criterion and the perspectives of the work are provided.