Blur resolved OCT: full-range interferometric synthetic aperture microscopy through dispersion encoding

We present a computational method for full-range interferometric synthetic aperture microscopy (ISAM) under dispersion encoding. With this, one can effectively double the depth range of optical coherence tomography (OCT), whilst dramatically enhancing the spatial resolution away from the focal plane. To this end, we propose a model-based iterative reconstruction (MBIR) method, where ISAM is directly considered in an optimization approach, and we make the discovery that sparsity promoting regularization effectively recovers the full-range signal. Within this work, we adopt an optimal nonuniform discrete fast Fourier transform (NUFFT) implementation of ISAM, which is both fast and numerically stable throughout iterations. We validate our method with several complex samples, scanned with a commercial SD-OCT system with no hardware modification. With this, we both demonstrate full-range ISAM imaging, and significantly outperform combinations of existing methods.Comment: 17 pages, 7 figures. The images have been compressed for arxiv - please follow DOI for full resolutio

Fast Computation of Minimal Interpolation Bases in Popov Form for Arbitrary Shifts

We compute minimal bases of solutions for a general interpolation problem, which encompasses Hermite-Pad\'e approximation and constrained multivariate interpolation, and has applications in coding theory and security. This problem asks to find univariate polynomial relations between $m$ vectors of size $\sigma$; these relations should have small degree with respect to an input degree shift. For an arbitrary shift, we propose an algorithm for the computation of an interpolation basis in shifted Popov normal form with a cost of $\mathcal{O}\tilde{~}(m^{\omega-1} \sigma)$ field operations, where $\omega$ is the exponent of matrix multiplication and the notation $\mathcal{O}\tilde{~}(\cdot)$ indicates that logarithmic terms are omitted. Earlier works, in the case of Hermite-Pad\'e approximation and in the general interpolation case, compute non-normalized bases. Since for arbitrary shifts such bases may have size $\Theta(m^2 \sigma)$, the cost bound $\mathcal{O}\tilde{~}(m^{\omega-1} \sigma)$ was feasible only with restrictive assumptions on the shift that ensure small output sizes. The question of handling arbitrary shifts with the same complexity bound was left open. To obtain the target cost for any shift, we strengthen the properties of the output bases, and of those obtained during the course of the algorithm: all the bases are computed in shifted Popov form, whose size is always $\mathcal{O}(m \sigma)$. Then, we design a divide-and-conquer scheme. We recursively reduce the initial interpolation problem to sub-problems with more convenient shifts by first computing information on the degrees of the intermediate bases.Comment: 8 pages, sig-alternate class, 4 figures (problems and algorithms

Orientation of the opposition axis in mentally simulated grasping

Five normal subjects were tested in a simulated grasping task. A cylindrical container filled with water was placed on the center of a horizontal monitor screen. Subjects used a precision grip formed by the thumb and index finger of their right hand. After a preliminary run during which the container was present, it was replaced by an image of the upper surface of the cylinder appearing on the horizontal computer screen on which the real cylinder was placed during the preliminary run. In each trial the image was marked with two contact points which defined an opposition axis in various orientations with respect to the frontal plane. The subjects’ task consisted, once shown a stimulus, of judging as quickly as possible whether the previously experienced action of grasping the container full of water and pouring the water out would be easy, difficult or impossible with the fingers placed according to the opposition axis indicated on the circle. Response times were found to be longer for the grasps judged to be more difficult due to the orientation and position of the opposition axis. In a control experiment, three subjects actually performed the grasps with different orientations and positions of the opposition axis. The effects of these parameters on response time followed the same trends as during simulated movements. This result shows that simulated hand movements take into account the same biomechanical limitations as actually performed movements

A (hopefully) friendly introduction to the complexity of polynomial matrix computations

This paper aims at a friendly introduction to the field of fast algorithms for polynomial matrices, and surveys the results of the ISSAC 2003 paper 'On the Complexity of Polynomial Matrix Computations' by Pascal Giorgi, Claude-Pierre Jeannerod, and Gilles Villard

Reply to our critics

Marc Jeannerod and I wrote a Précis of our 2003 book Ways of Seeing. The journal Dialogue asked Tim Schroeder, Alva Noë, Pierre Poirier and Martin Ratte to write a critical essay on our book. In this piece, we reply to our critics

The motor theory of social cognition: a critique

Recent advances in the cognitive neuroscience of action have considerably enlarged our understanding of human motor cognition. In particular, the activity of mirror neurons first discovered in the premotor cortex of macaque monkeys seems to provide an observer with the understanding of a perceived action by means of the motor simulation of the agent's observed movements. This discovery has raised the prospect of a motor theory of human social cognition. In humans, however, social cognition encompasses the ability to mindread. Many motor theorists of social cognition try to bridge the gap between motor cognition and mindreading by endorsing a simulation account of mindreading. Here, we argue that motor simulation is neither sufficient nor necessary for third-person mindreading

Simultaneous floating-point sine and cosine for VLIW integer processors

Accepted for publication in the proceedings of the 23rd IEEE International Conference on Application-specific Systems, Architectures and Processors (ASAP 2012).International audienceGraphics and signal processing applications often require that sines and cosines be evaluated at a same floating-point argument, and in such cases a very fast computation of the pair of values is desirable. This paper studies how 32-bit VLIW integer architectures can be exploited in order to perform this task accurately for IEEE single precision. We describe software implementations for sinf, cosf, and sincosf over [-pi/4,pi/4] that have a proven 1-ulp accuracy and whose latency on STMicroelectronics' ST231 VLIW integer processor is 19, 18, and 19 cycles, respectively. Such performances are obtained by introducing a novel algorithm for simultaneous sine and cosine that combines univariate and bivariate polynomial evaluation schemes