1. Articles from peter koch

    1-25 of 25
    1. Segmentation of Retinal Low-Cost Optical Coherence Tomography Images using Deep Learning

      Segmentation of Retinal Low-Cost Optical Coherence Tomography Images using Deep Learning

      The treatment of age-related macular degeneration (AMD) requires continuous eye exams using optical coherence tomography (OCT). The need for treatment is determined by the presence or change of disease-specific OCTbased biomarkers. Therefore, the monitoring frequency has a significant influence on the success of AMD therapy. However, the monitoring frequency of current treatment schemes is not individually adapted to the patient and therefore often insufficient. While a higher monitoring frequency would have a positive effect on the success of treatment, in practice it can only be achieved with a home monitoring solution. One of the key requirements of a home monitoring ...

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    2. Method for filtering reflexes in full-field setups for ophthalmologic imaging by separated illumination and detection apertures

      Method for filtering reflexes in full-field setups for ophthalmologic imaging by separated illumination and detection apertures

      A parallel detecting optical coherence tomography (OCT) setup and method, in which the light paths of the illumination of the sample and of the detection of the backscattered light do not use the same apertures. The separation of illumination and detection apertures filters these disturbing reflexes from the backscattered light of the sample and significantly increases image quality.

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      Mentions: Thorlabs
    3. Simple approach for aberration-corrected OCT imaging of the human retina

      Simple approach for aberration-corrected OCT imaging of the human retina

      Aberration-corrected imaging of human photoreceptor cells, whether hardware or software based, presently requires a complex and expensive setup. Here we use a simple and inexpensive off-axis full-field time-domain optical coherence tomography (OCT) approach to acquire volumetric data of an in vivo human retina. Full volumetric data are recorded in 1.3 s. After computationally correcting for aberrations, single photoreceptor cells were visualized. In addition, the numerical correction of ametropia is demonstrated. Our implementation of full-field optical coherence tomography combines a low technical complexity with the possibility for computational image correction.

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    4. Interferometric detection of 3D motion using computational subapertures in optical coherence tomography

      Interferometric detection of 3D motion using computational subapertures in optical coherence tomography

      Doppler optical coherence tomography (OCT) quantifies axial motion with high precision, whereas lateral motion cannot be detected by a mere evaluation of phase changes. This problem was solved by the introduction of three-beam Doppler OCT, which, however, entails a high experimental effort. Here, we present the numerical analogue to this experimental approach. Phase-stable complex-valued OCT datasets, recorded with full-field swept-source OCT, are filtered in the Fourier domain to limit imaging to different computational subapertures. These are used to calculate all three components of the motion vector with interferometric precision. As known from conventional Doppler OCT for axial motion only, the ...

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    5. Reduction of frame rate in full-field swept-source optical coherence tomography by numerical motion correction [Invited]

      Reduction of frame rate in full-field swept-source optical coherence tomography by numerical motion correction [Invited]

      Full-field swept-source optical coherence tomography (FF-SS-OCT) was recently shown to allow new and exciting applications for imaging the human eye that were previously not possible using current scanning OCT systems. However, especially when using cameras that do not acquire data with hundreds of kHz frame rate, uncorrected phase errors due to axial motion of the eye lead to a drastic loss in image quality of the reconstructed volumes. Here we first give a short overview of recent advances in techniques and applications of parallelized OCT and finally present an iterative and statistical algorithm that estimates and corrects motion-induced phase errors ...

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    6. In-vivo retinal imaging with off-axis full-field time-domain optical coherence tomography

      In-vivo retinal imaging with off-axis full-field time-domain optical coherence tomography

      With a simple setup, mainly composed of a low coherence light source and a camera, full-field optical coherence tomography (FF-OCT) allows volumetric tissue imaging. However, fringe washout constrains its use in retinal imaging. Here, we present a novel motion-insensitive approach to FF-OCT, which introduces path-length differences between the reference and the sample light in neighboring pixels using an off-axis reference beam. The temporal carrier frequency in scanned time-domain OCT is replaced by a spatial carrier frequency. Volumetric in-vivo FF-OCT measurements of the human retina were acquired in only 1.3 s, comparable to the acquisition times of current clinically used ...

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    7. Efficient holoscopy image reconstruction

      Efficient holoscopy image reconstruction

      Holoscopy is a tomographic imaging technique that combines digital holography and Fourier-domain optical coherence tomography (OCT) to gain tomograms with diffraction limited resolution and uniform sensitivity over several Rayleigh lengths. The lateral image information is calculated from the spatial interference pattern formed by light scattered from the sample and a reference beam. The depth information is obtained from the spectral dependence of the recorded digital holograms. Numerous digital holograms are acquired at different wavelengths and then reconstructed for a common plane in the sample. Afterwards standard Fourier-domain OCT signal processing achieves depth discrimination. Here we describe and demonstrate an optimized ...

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      Mentions: Thorlabs
    8. Common approach for compensation of axial motion artifacts in swept-source OCT and dispersion in Fourier-domain OCT

      Common approach for compensation of axial motion artifacts in swept-source OCT and dispersion in Fourier-domain OCT

      Swept-source optical coherence tomography (SS-OCT) is sensitive to sample motion during the wavelength sweep, which leads to image blurring and image artifacts. In line-field and full-field SS-OCT parallelization is achieved by using a line or area detector, respectively. Thus, approximately 1000 lines or images at different wavenumbers are acquired. The sweep duration is identically with the acquisition time of a complete B-scan or volume, rendering parallel SS-OCT more sensitive to motion artifacts than scanning OCT. The effect of axial motion on the measured spectra is similar to the effect of non-balanced group velocity dispersion (GVD) in the interferometer arms. It ...

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    9. Holoscopy—holographic optical coherence tomography

      Holoscopy—holographic optical coherence tomography
      Scanning optical coherence tomography (OCT) is limited in sensitivity and resolution by the restricted focal depth of the confocal detection scheme. Holoscopy, a combination of holography and Fourier-domain full-field OCT, is proposed as a way to detect photons from all depths of a sample volume simultaneously with uniform sensitivity and lateral resolution, even at high NAs. By using the scalar diffraction theory, as frequently applied in digital holographic imaging, we fully reconstruct the object field with depth-invariant imaging quality. In vivo imaging of human skin is demonstrated with an image quality comparable to conventionally scanned OCT.
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    10. Method for scanning optical interference patterns with line sensors

      Method for scanning optical interference patterns with line sensors
      A method is provided for the electronic scanning of the intensity distribution of an optical interference pattern by means of a linear image sensor, wherein the interference pattern is produced by overlapping two temporally partly coherent beams striking at an arbitrarily predefined angle .alpha. in relation to one another and is provided with an interference strip having a carrier frequency greater than the scanning frequency, and amplitude modulation that can be varied slowly in relation to the pixel width, wherein at least one optical grating is disposed in the beam path of at least one of two incident beams and ...
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    11. Comparison of fast swept source full-field OCT with conventional scanning OCT

      Comparison of fast swept source full-field OCT with conventional scanning OCT
      Recently, in-vivo full eld (FF) optical coherence tomography (OCT) with an ultra-high speed camera has been presented for fast in vivo retinal imaging. By parallel A-scans acquisition, imaging with 1,5 million A-scans/s was shown with an extended illumination of the retina. In this paper, the image quality of FF-OCT images will be compared to conventional scanning OCT systems. The eect of the absence of a confocal aperture leading to crosstalk between adjacent image points will be shown and an experimental analysis of the systems lateral point spread function (PSF) in dependence of depth will be given and discussed.
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    12. Real-time volumetric optical coherence tomography OCT imaging with a surgical microscope

      Real-time volumetric optical coherence tomography OCT imaging with a surgical microscope
      Optical coherence tomography is a unique technique to visualize subsurface tissue structures with a resolution below 10μm during microsurgery without tissue contact. Since it was introduced more than 15 years ago imaging speed was boosted by more than three orders of magnitude, from less than 100 to more than 300,000 A-scans per second. Instead of taking only still images of anatomical structures, the increased speed of OCT allows now to image volumes nearly in real time. This enables not only the scanning of larger tissue surfaces, but also opens new application beyond simple diagnosis. A noncontact volumetric imaging with ...
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    13. In vivo Fourier-domain full-field OCT of the human retina with 1.5 million A-lines/s

      In vivo Fourier-domain full-field OCT of the human retina with 1.5 million A-lines/s
      In vivo full-field (FF) optical coherence tomography (OCT) images of human retina are presented by using a rapidly tunable laser source in combination with an ultra-high-speed camera. Fourier-domain FF-OCT provided a way to increase the speed of retinal imaging by parallel acquisition of A-scans. Reduced contrast caused by cross talk was observed only below the retinal pigment epithelium. With a 100Hz sweep rate, FF-OCT was fast enough to acquire OCT images with acceptable motion artifacts. FF-OCT allows ultrafast retinal imaging, boosting image speed by a lack of moving parts and a considerably higher irradiation power.
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    14. Optical coherence tomography with online visualization of more than seven rendered volumes per second

      Optical coherence tomography with online visualization of more than seven rendered volumes per second
      Nearly real-time visualization of 3-D volumes is crucial for the use of optical coherence tomography (OCT) during microsurgery. With an ultrahigh speed spectral domain OCT coupled to a surgical microscope, on-line display of 7.2 rendered volumes at 87 megapixels per second is demonstrated. Calculating the A-scans from the spectra is done on a quad-core personal computer (PC), while dedicated software for the 3-D rendering is executed on a high performance video card. Imaging speed is practically only limited by the readout of the camera. First experiments show the feasibility of real-time 3-D OCT for guided interventions.
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    15. Using nonequispaced fast Fourier transformation to process optical coherence tomography signals

      In OCT imaging the spectra that are used for Fourier transformation are in general not acquired linearly in k-space. Therefore one needs to apply an algorithm to re-sample the data and finally do the Fourier Transformation to gain depth information. We compare three algorithms (Non-Equispaced DFT, i ... [Proc. SPIE 7372, 73720R (2009)] published Thu Jul 16, 2009.
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    16. Method and device for reading deep barcodes by way of optical interference

      This invention relates to a method for reading, while using optical interference, a barcode that extends into the depth of a substrate. The barcode is represented by an area with marks in the substrate that is partially transparent to electromagnetic radiation. The inventive method comprises the steps of irradiating the substrate with short coherence length light from a broad-band light source, dividing the light up into reference light and measuring light, returning the reference light and the measuring light back-scattered or reflected in the marked area to an analytical unit, determining the reflectance or the reflectivity of the substrate for ...
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    17. Interferometric device

      The invention relates to an interferometric device according to the preamble ofthe main claim. Devices for optical coherence tomography (OCT) comprise an interferometer and an evaluating unit for the electronic detection of an interference pattern.Interferometers and methods for determining the transit time distribution of reflected or scattered light are known under the term "Optical Coherence Tomography (OCT)". For example, DE 199 29 406 A1 describe such a method for the microscopicresolution
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    18. Method For Linear Optical Coherence Tomography (Wo 2008/138317)

      Method for optical coherence tomography for a plurality of depth intervals, at any desired separation, of a sample, wherein the interference signal is produced by superimposition of the measurement light beam, which passes through all the intervals, and a plurality of reference light beams of different reference arm lengths. Each depth interval has an associated reference arm, wherein the distances between two respective depth intervals correspond to the differences between the reference arm lengths of the reference arms associated with the depth intervals. The measurement light beam is called to interfere simultaneously with all the reference light beams on a ...
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    19. Device for changing the length of the running path of an electromagnetic wave

      The device serves the change of the length of the running path of an electromagnetic wave, and specifically of a light beam between the emitter and receiver. It comprises two oppositely lying reflection means between which the beam is reflected, as well as a means for changing the distance of these reflection means. The reflection means are arranged at an angle .beta. to one another which lies between 0.degree. and 45.degree. so that the incident beam is thrown to and fro several times between the reflection means, until it is finally congruently thrown back.
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    20. Process and arrangement for examining a section of the eye

      Systems, methods, and apparatus are provided for deriving the relative position of an eye by tracking a boundary of the eye such as the limbus (i.e., the interface between the white sclera and the colored iris). A technique for tracking the position of the eye of patient comprises directing light to an annular region of the eye between the sclera and the iris and receiving reflected light from that region. The intensity of the reflected light is then measured to determine a relative position of the eye. In some embodiments, the measured region is scanned around the boundary. In ...
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    1-25 of 25
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    1. (18 articles) University of Lübeck
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    Optical coherence tomography with online visualization of more than seven rendered volumes per second In vivo Fourier-domain full-field OCT of the human retina with 1.5 million A-lines/s Real-time volumetric optical coherence tomography OCT imaging with a surgical microscope Comparison of fast swept source full-field OCT with conventional scanning OCT Holoscopy: holographic optical coherence tomography Method for scanning optical interference patterns with line sensors Holoscopy—holographic optical coherence tomography 3D OPTICAL IMAGING: Holoscopy makes ultrafast lensless imaging of scattering tissues possible Post-Doctoral and Graduate Student Research Positions at the University of Illinois Urbana-Champaign Multiscale correlation of microvascular changes on optical coherence tomography angiography with retinal sensitivity in diabetic retinopathy Macrophage targeted theranostic strategy for accurate detection and rapid stabilization of the inflamed high-risk plaque PERSONALIZED CHARACTERISTICS OF MORPHOMETRIC AND FUNCTIONAL PARAMETERS OF RETINA IN ARTERIAL HYPERTENTION ACCORDING TO OPTICAL COHERENCE TOMOGRAPHY-ANGIOGRAPHY DATA