1. Articles from Adolf F. Fercher

    1-19 of 19
    1. Key Developments for Partial Coherence Biometry and Optical Coherence Tomography in the Human Eye Made in Vienna

      Key Developments for Partial Coherence Biometry and Optical Coherence Tomography in the Human Eye Made in Vienna

      Purpose : To describe key developments of optical biometry and optical coherence tomography (OCT) for ophthalmic applications made by one of the pioneering research groups. Methods : Partial coherence interferometry (PCI) as the basic ranging technology for modern optical biometry and for OCT was introduced for biomedical applications in the 1980s. Later, Fourier domain (FD) OCT was introduced and demonstrated to provide superior sensitivity as compared to time domain OCT. Further developments comprised ultrahigh-resolution OCT and deep-penetration OCT at wavelengths of approximately 1050 nm. Important functional extensions comprise Doppler OCT/OCT angiography, polarization-sensitive OCT, and adaptive optics OCT. Results : High-precision PCI biometry ...

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    2. Dual-band refractive low coherence interferometry in the spectral domain for dispersion measurements

      Dual-band refractive low coherence interferometry in the spectral domain for dispersion measurements

      We present a spectral domain refractive low coherence interferometry technique (SD-rLCI) using a novel extreme broadband Super Continuum laser source equipped with a dual spectrometer system which is able to measure the dispersion in the visual and near infrared range simultaneously. The setup was verified obtaining the second order dispersion of distilled water. We will use this system for measuring the dispersion sensitivities of important tissue substances in order to determine analyte concentrations within mixtures.

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    3. High sensitivity phase mapping with parallel Fourier domain optical coherence tomography at 512 000 A-scan/s

      High sensitivity phase mapping with parallel Fourier domain optical coherence tomography at 512 000 A-scan/s

      In this paper we present an ultra high speed and highly phase sensitive line-field FD-OCT system for quantitative phase mapping. The system works with a maximum speed of 512 000 A-scan/s (1000 fps) in real time mode. Along the parallel recorded direction excellent phase stability corresponding to a path length variation of only 510 pm was measured. We demonstrate how to exploit this phase accuracy for fast chemical analysis of glucose mixture processes. The system has particular potential for studying micro-fluidic processes.

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    4. Improved sensitivity measurement of the human eye length in vivo with Fourier domain optical coherence tomography

      Branislav Grajciar, Michael Pircher, Christoph K. Hitzenberger et al. We present a system for intraocular distance measurement of the human eye in vivo with high sensitivity. The instrument is based on Fourier domain low coherence interferometry (FD-LCI). State-of-the-art FD-LCI systems are capable to image a depth range of only a few mm, because the depth range is de ... [Proc. SPIE Int. Soc. Opt. Eng. 6844, 68440L (2008)] published Mon Feb 11, 2008.

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    5. High sensitive measurement of the human axial eye length in vivo with Fourier domain low-coherence interferometry

      In this paper we present a system for intraocular distance measurement of the human eye in vivo with high sensitivity. The instrument is based on Fourier domain low coherence interferometry (FD-LCI). Stateof-the-art FD-LCI systems are limited to a depth range of only a few mm, because the depth range is determined by the spectral resolution of the spectrometer. To measure larger distances (e.g. human eye length) we implemented two separate reference arms with different arm lengths into the interferometer. Each reference arm length corresponds to a different depth position within the sample (e.g. cornea and retina). Therefore two ...

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    6. Submicrometer axial resolution optical coherence tomography.

      Optical coherence tomography (OCT) with unprecedented submicrometer axial resolution achieved by use of a photonic crystal fiber in combination with a compact sub-10-fs Ti:sapphire laser (Femtolasers Produktions) is demonstrated for what the authors believe is the first time. The emission spectrum ranges from 550 to 950 nm (lambda(c)=725 nm , P(out)=27 mW) , resulting in a free-space axial OCT resolution of ~0.75 mum , corresponding to ~0.5 mum in biological tissue. Submicrometer-resolution OCT is demonstrated in vitro on human colorectal adenocarcinoma cells HT-29. This novel light source has great potential for development of spectroscopic OCT because ...

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    7. Quantitative differential phase measurement and imaging in transparent and turbid media by optical coherence tomography.

      Differential phase-contrast optical coherence tomography allows one to measure the path-length differences of two transversally separated beams in the nanometer range. We calculate these path-length differences from the phase functions of the interferometric signals. Pure phase objects consisting of chromium layers containing steps of approximately 100-200-nm height were imaged. Phase differences can be measured with a precision of +/-2 degrees , corresponding to a path-difference resolution of 2-3 nm. To investigate the influence of scattering, we imaged the phase objects through scattering layers with increasing scattering coefficients. The limit of phase imaging through these layers was at approximately 8-9 mean free ...
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    8. Method and an apparatus for the simultaneous determination of surface topometry and biometry of the eye

      An apparatus (10, 10') for detecting the surface topography of a cornea (24) of an eye (22) by dynamic or static projection of a pattern onto the surface of the cornea and detection of the pattern reflected by the cornea, providing preferably simultaneous detection of at least one optical property of a layer disposed beneath the cornea.
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      Mentions: Adolf F. Fercher
    9. Numerical a posteriori dispersion compensation in PCI measurement signals and OCT A-scan signals with spatially variant correlation core

      A method and/or arrangement for compensating the dispersion in signals of short-coherence interferometers and/or OCT interferometers, wherein the effect of the dispersion is eliminated by subsequent compensation in that the interferometer signal is correlated with a spatially variant correlation core which corresponds along the measurement axis in z-direction to an interferometer signal of an individual light-reemitting location with the same dispersion which is punctiform in z-direction.
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    10. Optical coherence interferometry and coherence tomography with spatially partially coherent light sources

      An airbag cover is defined by a predetermined breaking line which is introduced into a shaped flat material in a recessed manner. The recesses are achieved by removing material by means of laser radiation. According to the invention, the flat material is provided with a barrier layer. The barrier layer, by reason of its material properties, has greater resistance to removal of material by laser action than the material of the rest of the flat material. The recesses made by removing material extend along the predetermined breaking line in the flat material up to the barrier layer. The barrier layer ...
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    11. Optical multiplex short coherence interferometry on the eye

      The invention is directed to the detection and imaging of the internal geometry of the eye, particularly of the important components for imaging in the eye such as the cornea, lens, vitreous body and retinal surface, by multichannel short coherence interferometry. A method and arrangement for obtaining topograms and tomograms of the eye structure by many simultaneously recorded interferometric depth scans through transversely adjacent points in the pupil using spatially coherent or spatially partially coherent light sources. The depth scan is carried out by changing the optical length of the interferometer measurement arm by means of a retroreflector. By continuously ...
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    12. Arrangements for coherence topographic ray tracing on the eye

      Topographic measurement of eye structures based on short coherence interferometry is the subject of the invention. The problem occurring in this connection is that longitudinal and transverse eye movements during signal registration lead to errors in the measured structure. The influences of longitudinal eye movements are compensated in that the reference beam, independent from the measurement beam, is directed to the corneal vertex and is reflected at the latter. The influences of longitudinal eye movements are minimized in that the transverse position of the eye is monitored by means of a direction-dependent registration of the light reflected at the corneal ...
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    13. Method and apparatus for the simultaneous determination of surface topometry and biometry of the eye

      An apparatus (10') for detecting the surface topography of a cornea (24) of an eye (22) by dynamic or static projection of a pattern onto the surface of the cornea and detection of the pattern reflected by the cornea, providing preferably simultaneous detection of at least one optical property of a layer disposed beneath the cornea.
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      Mentions: Adolf F. Fercher
    14. Arrangement for spectral interferometric optical tomography and surface profile measurement

      An arrangement is provided for optical surface profile measurement and for obtaining optical sectional images of transparent, partially transparent and opaque objects by the spectral interferometric OCT method. In the spectral interferometric OCT method, the depth position of the object locations from which light is diffusely reflected is given by the light diffusely reflected by the object through a Fourier transform. Because of the path difference between the object light and reference light which is required for this purpose, large spatial frequencies occur in the spectrum which impair the resolution capacity of this method. According to the invention, the reference ...
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    15. Method and arrangement for transverse optical coherence tomography

      A problem occurring in the acquisition of planar sectional images by means of transverse optical coherence tomography consists in that the frequency of the photoelectric interferometer signal is not constant during the scanning process. The corresponding frequency bandwidth impedes the electronic bandpass filtering required for noise reduction. However, planar tomographic images are particularly important. A beam path which is telecentric on the object side is realized in that the center of rotation of the pair of scanning mirrors which directs the scanning measurement beam onto the object is arranged in the focal plane of the focussing optics. In this way ...
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    16. Optical coherence tomography with dynamic coherent focus

      In coherence tomography, an interferometric measurement light beam scans the measurement object and is focused for improving the transverse resolution. In order to achieve a high transverse resolution over the entire object depth, the focal displacement and the change in path length in the measurement light beam for maintaining the coherence of the focus is achieved by one and the same moving optical element in the measurement light beam. The present invention achieves this by a particularly simple and easily adjustable arrangement which is characterized by especially low light loss in the measurement beam path.
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    17. Methods and arrangement for increasing contrast in optical coherence tomography by means of scanning an object with a dual beam

      In optical coherence tomography, a sectional image I(x,z) of an object is obtained in that a light beam scans the object along a x-line on the surface, and the depth z from which light of intensity I is reflected is measured by means of a partial-coherence interferometer. In so doing, a strong medium intensity can cover and conceal small differences in adjacent object points. The invention renders small differences in adjacent object points visible in that the object is illuminated by a dual beam which simultaneously illuminates the object at two adjacent points and whose two components are ...
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    18. Coherence biometry and coherence tomography with dynamic coherent

      In the application of coherence distance measurement in medical biometry and in medical coherence tomography, an interferometric measurement light path is directed on the object to be measured and is focussed in order to improve the transverse resolution. Since the focus of the measurement light beam is fixed in the axial direction, high transverse resolution cannot be achieved over the entire object depth at all interferometric measurement points along the measurement light beam. This problem is not solved merely by displacing the focus along the measurement beam, since the focus will then lose coherence with respect to the reference light ...
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    1-19 of 19
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  2. Topics in the News

    1. (18 articles) Adolf F. Fercher
    2. (11 articles) Carl Zeiss Meditec
    3. (8 articles) Medical University of Vienna
    4. (5 articles) Christoph K. Hitzenberger
    5. (4 articles) Rainer A. Leitgeb
    6. (4 articles) Branislav Grajciar
    7. (2 articles) Michael Pircher
    8. (2 articles) Wolfgang Drexler
    9. (2 articles) Harald Sattmann
    10. (2 articles) Oliver Findl
    11. (2 articles) Heidelberg Engineering
    12. (1 articles) University of Ulsan
    13. (1 articles) The Chinese University of Hong Kong
    14. (1 articles) Fernando Alfonso
    15. (1 articles) Optovue
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