Reliable Versatile Low Noise Laser Empowering Sensing Technologies

Author Institution: Redfern Integrated Optics, Inc.Slides presented at the 2014 Photonic Doppler Velocimetry (PDV) Workshop Hosted by National Security Technologies, LLC, and the University of Nevada Las Vegas, June 24-26, 2014, Las Vegas, Nevada

Characteristics of the Single-Longitudinal-Mode Planar-Waveguide External Cavity Diode Laser at 1064 nm

We describe the characteristics of the planar-waveguide external cavity diode laser (PW-ECL). To the best of our knowledge, it is the first butterfly-packaged 1064 nm semiconductor laser that is stable enough to be locked to an external frequency reference. We evaluated its performance from the viewpoint of precision experiments. Using a hyperfine absorption line of iodine, we suppressed its frequency noise by a factor of up to 104 at 10 mHz. The PWECL's compactness and low cost make it a candidate to replace traditional Nd:YAG nonplanar ring oscillators and fiber lasers in applications that require a single longitudinal mode

Efficient modeling of entangled details for natural scenes

Proceedings of Pacific Graphics 2016 (Okinawa)International audienceDigital landscape realism often comes from the multitude of details that are hard to model such as fallen leaves, rock piles orentangled fallen branches. In this article, we present a method for augmenting natural scenes with a huge amount of details suchas grass tufts, stones, leaves or twigs. Our approach takes advantage of the observation that those details can be approximatedby replications of a few similar objects and therefore relies on mass-instancing. We propose an original structure, the GhostTile, that stores a huge number of overlapping candidate objects in a tile, along with a pre-computed collision graph. Detailsare created by traversing the scene with the Ghost Tile and generating instances according to user-defined density fields thatallow to sculpt layers and piles of entangled objects while providing control over their density and distribution

Refining scores based on patient reported outcomes – statistical and medical perspectives

Background: Patient Reported Outcomes (PRO) are gaining more and more importance in the context of clinical trials. The assessment of PRO is frequently performed by questionnaires where the multiple items of a questionnaire are usually pooled within summarizing scores. These scores are used as variables to measure subjective aspects of treatments and diseases. In clinical research, the calculation of these scores is mostly kept very simple, e.g. by a simple summation of item values. In the medical literature, there is hardly any guidance for performing a refinements of questionnaires and for deducing adequate scores. In contrast, in psychometric literature, there are plenty of more sophisticated methods, which overcome typical assumptions made in traditional (sum) scores, however to the prize of more complicated algorithms, which might be difficult to communicate. When faced with the practical task to refine an existing questionnaire, there exist a clear gap of guidance for applied medical researchers. By this article we try to fill this important gap between psychometric theory and medical application by illustrating our methodological choices on the example of a clinical PRO questionnaire. Methods: Based on our experiences with the refinement of the BCTOS, a PRO questionnaire to assess aesthetic and function after breast conserving therapy in breast cancer patients, we present the following general steps that we performed by refining the BCTOS questionnaire and its scores: 1. Refinement of the length of the questionnaire and the (item-factor) structure. 2. Selection of the factor score estimation method. 3. Validation of the refined questionnaire and scores with respect to validity, reliability and structure based on a validation cohort. Results: Our step-step-step procedure helped us to shorten the current form of the BCTOS and to redefine the factor structure. By this, the compliance of patients can be increased and the interpretation of the results becomes more coherent. Conclusions: We present a step-by-step procedure to refine an existing medical questionnaire along with its scores illustrated and discussed by the refinement of the BCTOS. Trial registration: Due to the character of the study (no intervention study), no registration was performed

Coarse-to-fine medial surfaces

We study the problem of computing the medial surface of a polyhedral solid. As this problem is difficult to solve exactly, we consider an approximate solution that locates regions of space through which the medial surface passes. The algorithm we design is based on the measure of the average outward flux of the gradient of the Euclidian distance transform of the polyhedron through the surface of a spherical region shrinking to a point. We extend previous methods by developing a completeness criterion that adopts this measure for spheres of non-zero size. As a result, we obtain a coarse-to-fine algorithm that reveals those voxels that contain sections of the medial surface. Such an implementation has the advantage that digital thinning with homotopy type preservation can be borrowed from past work. We argue that the error due to discrete flux computations is bounded

Medial spheres for shape representation

This thesis presents a particular set of spheres as new representation of the shape of a 3D solid. The spheres considered are maximal inscribed spheres in the solid and their centres are chosen in such a way that at most one sphere centre lies in a cubic region of space.The shape representation proposed is a discretization of the medial surface transform of a solid. Part I of this thesis presents algorithms for the computation of this representation given a boundary representation of a solid by approximating its medial surface transform. Properties of those medial spheres that are not detected by our algorithm in 3D are described and a complete characterization of those medial circles that are not detected by a 2D version of our algorithm is given. In Part II, recent results from differential geometry are used to compute principal curvatures and principal curvature directions on the boundary of the smooth solid represented using the union of medial spheres. This computation is performed using only the medial sphere centres and a pair of points on each medial sphere that lies on the surface of the solid being modeled. It is shown how the union of medial spheres allows a part-based description of the solid, with a significance measure associated with each part. In Part III, it is shown that our shape representation can offer a tight volumetric fit to a polyhedron, using a small number of spheres. The spheres used in our representation can be quickly updated as the solid undergoes a certain class of deformations. It is shown how our set of medial spheres allows efficient and accurate proximity queries between polyhedra.Cette thèse présente une nouvelle représentation de la forme de solides 3D, décrite par un ensemble spécifique de sphères. Les sphères de cette représentation sont des sphères inscrites maximalement dans le solide et leur centre est choisi de telle manière que tout au plus un seul centre de sphère occupe une région cubique de l'espace. La représentation de forme proposée est une discrétisation de la surface médiane d'un solide. La première partie de cette thèse présente des algorithmes pour le calcul de cette représentation à partir d'une description de la frontière d'un solide, en approximant sa surface médiane. Certaines propriétés des sphères médianes qui ne sont pas détectées par notre algorithme en 3D sont décrits, ainsi qu'une caractérisation complète des cercles médians qui ne sont pas détectés par une version 2D de l'algorithme.En deuxième partie, des résultats récents en géométrie différentielle sont utilisés pour calculer les courbures principales et les directions principales de courbure sur la surface d'un solide lisse représenté par une union de sphères médianes. Ce calcul est effectué en utilisant seulement le centre et une paire de points relatifs à chaque sphère médiane qui se trouve sur la surface du solide. Il est aussi démontré comment l'union des sphères médianes permet une description par partie du solide, tout en donnant une mesure de l'importance associée à chaque partie.En troisième partie, il est démontré que notre représentation de forme peut servir à l'ajustement volumétrique serré d'un polyèdre, tout en utilisant un nombre restreint de sphères. Les sphères utilisées dans notre représentation peuvent être rapidement adaptées au solide lorsqu'il est sujet à une certaine classe de déformations. Notre ensemble de sphères médianes permet d'effectuer des requêtes de proximité efficaces et précises entre des polyèdres