Petri Helin

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Starting from the orthogonal (greedy) least squares method, we build an adaptive algorithm for finding online sparse solutions to linear systems. The algorithm belongs to the exponentially windowed recursive least squares (RLS) family and maintains a partial orthogonal factorization with pivoting of the system matrix. For complexity reasons, the(More)
This paper studies the lossless compression of rectified light-field images captured by plenoptic cameras, exploiting the high similarity existing between the subaperture images, or views, composing the light-field image. The encoding is predictive, where one sparse predictor is designed for every region of a view, using as regressors the pixels from the(More)
This research work concerns the application of modern signal processing methods, based on sparse modeling and convex optimization, to the problems arising in passive underwater surveillance. Starting from recently proposed sparse methods for direction of arrival (DOA) estimation we have constructed greedy sparse algorithms for estimation of wideband sources(More)
This paper proposes a complete lossless compression method for exploiting the redundancy of rectified light-field data. The light-field data consist of an array of rectified subaperture images, called for short views, which are segmented into regions according to an optimized partition of the central view. Each region of a view is predictively encoded using(More)
We introduce and investigate several criteria for matching the outer contour generated by a model of the manipulation target against the image data captured with a stereo camera rig. The more complex criteria are intended for the initial stage of scene analysis, to provide pose and location estimation for path planning, and the faster methods can be used in(More)
A plenoptic camera consists of microlenses that enable the measuring of directional information. A common image formation model of the plenoptic camera is based on geometrical optics and provides an object reconstruction with a resolution equal to the number of microlenses. We use a more accurate model that takes into account the wave properties of light. A(More)
This paper studies the lossless compressibility of raw sensor images acquired by plenoptic cameras, when optimally interpolating the microlens images in terms of already encoded microlens images. The geometrical information necessary for splitting the sensor image into projections of microlenses, together with a relatively small bitstream for encoding the(More)
We propose a method for the estimation of direction of arrival (DOA) of wideband sources using a sensor array, especially directed for improving the DOA estimation accuracy in the case of close sources. Starting from the spatial spectrum estimated by MVDR separately in each subband, we select a number of peaks in each subband and build the likelihood of a(More)
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