We propose a novel approach to use OCT speckle analysis to quantify absolute flow speed in skin blood vessels. Using a bespoke scan acquisition pattern, we empirically compute a probability density function for the L1-norm decorrelation measure as a function of displacement. During clinical scanning, we calculate the decorrelation value within a small window at each point. By inverting the probability function, we are able to calculate a probability distribution over the possible values of blood displacement, and hence flow speed. We demonstrate the algorithm on 10 human patients who have suffered heart failure and 10 age-matched healthy control subjects.
Registration of two types of digital holograms is considered: digital hyperspectral holograms and Denisyuk volume holograms (holograms in colliding beams). Hyperspectral holograms are considered as an analogue of thin holograms, in which zero order and a conjugate image are suppressed. Previously proposed principles are developed for the case of thick holograms in their digital representation. It is shown that the displacement of a scanning mirror in the process of hyperspectral holograms capturing is analogous to registering of the blackening function of layers of the volume hologram. The position of the mirror corresponds to the layers in a thick hologram, where the interference pattern is recorded in layers. An analogy is drawn between the restoration of a hologram by a light beam and its processing of its digital analog.
An optical scheme of recording digital holograms of micro-objects based on high numerical aperture off-axis parabolic mirror forming a high aperture reference wave is suggested. Registration of digital holograms based on the proposed optical scheme is confirmed experimentally. Application of the proposed approach for hyperspectral holograms registration of micro-objects in incoherent light is discussed.
It is suggested to measure non-axis parabolic mirrors aberrations and try to compensate for them. For the aberration prediction the computer modeling is used. For the aberration measurement Shack-Hartmann wavefront sensor is applied. For the aberrations compensation a digital algorithm is used.
Novel method is suggested for a hyperspectral wave field holographic recording, based on asymmetrical Fourier spectrometer with a flat microobject placed in one of its arms. The output signal, which is the interference of the reference field with the field diffracted by the object, is registered by CCD. The process of recording is reduced to consecutive registration of two-dimensional interferograms by changing the optical length of the reference arm of the interferometer. One-dimensional Fourier transform of the interferogram in each pixel gives a spatial distribution of the complex amplitude for all spectral components of a hyperspectral object field. Inverse Fresnel transform of this field gives a hyperspectral object field in the object plane. Hyperspectral amplitude and average-phase profile images of standard microscope samples obtained experimentally are presented. Coloring, Fellgett’s advantage and speckle noise reduction are discussed.
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