Article

Bifocal-optical coherenc refractometry of turbid media

Optical+Biomedical Engineering Laboratory, Department of Electrical and Electronic Engineering, The University of Western Australia, Crawley, WA 6009, Australia.
Optics Letters (Impact Factor: 3.39). 02/2003; 28(2):117-9. DOI: 10.1364/OL.28.000117
Source: PubMed

ABSTRACT We propose and demonstrate a novel technique, which we term bifocal optical coherence refractometry, for the rapid determination of the refractive index of a turbid medium. The technique is based on the simultaneous creation of two closely spaced confocal gates in a sample. The optical path-length difference between the gates is measured by means of low-coherence interferometry and used to determine the refractive index. We present experimental results for the refractive indices of milk solutions and of human skin in vivo. As the axial scan rate determines the acquisition time, which is potentially of the order of tens of milliseconds, the technique has potential for in vivo refractive-index measurements of turbid biological media under dynamic conditions.

0 Bookmarks
 · 
125 Views
  • [Show abstract] [Hide abstract]
    ABSTRACT: A method for simultaneous measurement of geometric thickness and refractive index of an optical wafer is presented. By using a fiber optic Mach–Zehnder interferometer (MZI) with a free space, the transmission spectrum of a MZI for the optical wafer at different incidence angle is interrogated, and the geometric thickness and the refractive index of the optical wafer are measured simultaneously. With the transmission spectrum, we can obtain a clear interferogram with a high visibility no matter how small the measurement range of the refractive index. Therefore the proposed technique possesses a broad measurement range and low cost. The experimental results show that the maximum errors of the geometric thickness and the refractive index are only 0.007 mm and 0.008, respectively, and that a broad measurement from 1.316 to 3.503 can be achieved.
    Journal of Modern Optics 08/2013; 60(11). DOI:10.1080/09500340.2013.821536 · 1.17 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: We propose and demonstrate a novel technique, termed dual-beam confocal microscopy, for the simultaneous measurement of the refractive index and geometrical thickness of a single layer. The technique is based on the creation of two closely spaced lateral confocal gates for the two orthogonal polarization states of a laser beam in a sample via a Nomarski prism. Thereafter, by applying Gaussian beam theory, the refractive index can be determined with an error of 1% or less for a commercial cover glass. Based on the measured refractive index, the thickness of the sample can also be calculated. To verify the proposed methodology and optical setup, a microlens array was scanned, with the surface profile and refractive index subsequently compared with their catalog specifications.
    Measurement Science and Technology 05/2013; 24(7):075003. DOI:10.1088/0957-0233/24/7/075003 · 1.35 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: We propose and demonstrate a novel refractive index (RI) measurement by using the numerical-sample-motion based the defocus correction method in full field optical coherence tomography (FF-OCT). Overcoming the general problem in FFOCT that is the position of the focal plane is separated from the position of the image plane when imaging a deep region inside a sample, we measure the separation distance from the position of the focal plane to the position of the image plane. The RI is determined from the separation distance that is obtained by the numerically adjusted distance of a sample position. With the proposed method, the depth resolved RIs of double layer materials are determined.
    Proceedings of SPIE - The International Society for Optical Engineering 05/2012; DOI:10.1117/12.922398 · 0.20 Impact Factor

Full-text (2 Sources)

Download
64 Downloads
Available from
Jun 10, 2014