Space-frequency analysis of pseudo-periodic patterns for subpixel position control

International audienceThis paper reports on visual position measurement based on space-frequency analysis of a pseudo-periodic pattern. This approach can be seen as a two-dimensional extension of the Vernier principle as used in the Vernier caliper. The pseudoperiodic pattern fixed on the target is seen as a secondary scale that is compared to the reference scale formed by the image pixel frame. By performing space-frequency analysis and phase computations, the center of the pseudo-periodic pattern is retrieved with a subpixel accuracy and the in-plane orientation is determined as well. Several configurations allow different kinds of measurement. A single camera vision system leads to in-plane pose estimation. Stroboscopic illumination can be used to quantify vibration amplitudes down to the nanometer range. A two camera setup can be used for displacement measurements along the three spatial directions while the choice of an interference objective, sensitive to out-of-plane direction, can complement the measurement to address the six degrees of freedom. An extended pseudo-periodic pattern was also designed to locate any field of observation within a wide dimension surface

Pseudo-periodic patterns for subpixel accuracy visual control: principle, pattern designs, and performances

International audienceA vision system is used for measuring in-plane target displacement, position and orientation. Pseudo-periodic patterns fixed on the target forms a phase reference. Absolute position is determined with subpixel accuracy by phase computations. Various position encoding designs are proposed for different displacement ranges and resolution. Performances obtained are compared and discussed for both displacement and orientation measurements. The capability to resolve position on depth ranges larger than the lens depth of focus is demonstrated

Pseudo-Periodic Encryption of Extended 2-D Surfaces for High Accurate Recovery of any Random Zone by Vision

International audienceThis article presents a binary position encoding method for extended two-dimensional surfaces. Position encryption is based on linear feedback shift register sequences inserted within a periodic frame of spots. The position and orientation of any local view is retrieved accurately with respect to the encrypted surface. Image processing combines phase computations with binary image feature analysis. Measurement resolution is in the range of 10-2 pixel in position and 10-3 degree for in-plane orientation. The method is used as a visual sensor in a position control loop applied to fluorescence optical microscopy for the recovery of cells of interest within culture dishes

Position-referenced microscopy: Regions of interest localization and subpixel image comparison by means of pseudo-random patterns embedded in cell culture boxes.

International audienceThis work presents micro-grids integrated to cell culture boxes. These grids allow the systematic registration of the position of a zone observed by optical microscopy in a such way that it is possible to find it again easily for new observations for instance after culture on drug injection. The position knowledge allows also the numerical superimposition of recorded images in a common position reference system with a sub-pixel precision. It become thus straightforward to perform a site by site analysis of the possible evolutions that may have occurred in the biological medium

Twin-scale Vernier Micro-Pattern for Visual Measurement of 1D in-plane Absolute Displacements with Increased Range-to-Resolution Ratio

Abstract—This paper presents a visual method for 1D in-plane displacement measurement which combines a resolution of a few nanometers with an unambiguous excursion range of 168 µm. Furthermore, position retrieval is only based on elementary phase computations and thus might become compatible with high-rate processing by implementing the processing algorithm on high speed computing architectures like a DSP or a FPGA device. The method is based on a twin scale Vernier micro-pattern fixed on the moving target of interest. The two periodic grids have slightly different periods in order to encode the period order within the phase difference observed between the two sub-patterns. As a result, an unambiguous range of 168 µm is obtained from grid periods of 8 µm and 8.4 µm. The resolution is evaluated to be of 11.7 nm despite remaining mechanical disturbances. Differential measurements demonstrated indeed a measurement accuracy better than 5 nm. I

Visual in-plane positioning of a Labeled target with subpixel Resolution: basics and application

Vision is a convenient tool for position measurements. In this paper, we present several applications in which a reference pattern can be defined on the target for a priori knowledge of image features and further optimization by software. Selecting pseudo-periodic patterns leads to high resolution in absolute phase measurements. This method is adapted to position encoding of live cell culture boxes. Our goal is to capture each biological image along with its absolute highly accurate position regarding the culture box itself. Thus, it becomes straightforward to find again an already observed region of interest when a culture box is brought back to the microscope stage from the cell incubator where it was temporarily placed for cell culture. In order to evaluate the performance of this method, we tested it during a wound healing assay of human liver tumor-derived cells. In this case, the procedure enabled more accurate measurements of the wound healing rate than the usual method. It was also applied to the characterization of the in-plane vibration amplitude from a tapered probe of a shear force microscope. The amplitude was interpolated by a quartz tuning fork with an attached pseudo-periodic pattern. Nanometer vibration amplitude resolution is achieved by processing the pattern images. Such pictures were recorded by using a common 20x magnification lens.La visión es una herramienta conveniente para mediciones de posición. En este artículo, presentamos aplicaciones en las que un patrón de referencia puede ser adherido al objeto de interés. Ésto permite tener un conocimiento a priori de las características de la imagen y así poder optimizar el software. Como patrón de referencia se usan patrones pseudo-periódicos, los cuales permiten una alta resolución en las mediciones de fase absoluta. El método es adaptado para codificar la posición de soportes de cultivos celulares, con el fin de documentar cada imagen biológica registrada con su posición absoluta. Por lo tanto, resulta sencillo encontrar de nuevo una región de interés, observada previamente, cuando una caja de cultivo es traída de nuevo al microscopio luego de estar en una incubadora. Para evaluar el método, éste se utilizó durante un ensayo de “cicatrización de herida” de un cultivo celular derivado de tumores hepáticos. En este caso, el método permite obtener mediciones más precisas de la tasa de “cicatrización”, comparado a los resultados obtenidos con el método usual. El método propuesto también se aplica a la caracterización de la amplitud de vibración en el plano de una sonda de un microscopio de fuerza atómica. La amplitud fue interpolada por medio de un diapasón de cuarzo al cual se la adhirió un patrón pseudo-periódico. A partir del procesamiento de las imágenes del patrón, se logra obtener resolución nanométrica en la medida de la amplitud de la vibración. Estas imágenes fueron obtenidas con un microscopio óptico con magnificación 20x

Cultural Identity, Religion, and Globalization in Latin America. Our Lady of Guadalupe and Saint Martin de Porres as Clear Examples of Interculturalism and Instruments of Mediation among Different Weltanschauungen

Latin America is a part of that Global village where—according to Marc Augé—places, time, and space exist in abundance and where the presumed unique nature of the Western model clashes with the image of the “other”. (Augé (2009); Salgues (2016), p. 114) Thus, while the formation of a multiethnic and multicultural society—one based on the principle of tolerance, in which diversity and homologation should coexist without conflict—is hoped for, the spread of such categories as ethnicity and minority underscores the dissimilarities of our time. Starting from such basic concepts as, for example, religion, culture, otherness, and identity, and with the analysis of two case studies—Our Lady of Guadalupe and Saint Martín de Porres—the aim is to raise a problem: does a Latin American cultural identity exist? And how can it be identified

Switching TNF antagonists in patients with chronic arthritis: An observational study of 488 patients over a four-year period

The objective of this work is to analyze the survival of infliximab, etanercept and adalimumab in patients who have switched among tumor necrosis factor (TNF) antagonists for the treatment of chronic arthritis. BIOBADASER is a national registry of patients with different forms of chronic arthritis who are treated with biologics. Using this registry, we have analyzed patient switching of TNF antagonists. The cumulative discontinuation rate was calculated using the actuarial method. The log-rank test was used to compare survival curves, and Cox regression models were used to assess independent factors associated with discontinuing medication. Between February 2000 and September 2004, 4,706 patients were registered in BIOBADASER, of whom 68% had rheumatoid arthritis, 11% ankylosing spondylitis, 10% psoriatic arthritis, and 11% other forms of chronic arthritis. One- and two-year drug survival rates of the TNF antagonist were 0.83 and 0.75, respectively. There were 488 patients treated with more than one TNF antagonist. In this situation, survival of the second TNF antagonist decreased to 0.68 and 0.60 at 1 and 2 years, respectively. Survival was better in patients replacing the first TNF antagonist because of adverse events (hazard ratio (HR) for discontinuation 0.55 (95% confidence interval (CI), 0.34-0.84)), and worse in patients older than 60 years (HR 1.10 (95% CI 0.97-2.49)) or who were treated with infliximab (HR 3.22 (95% CI 2.13-4.87)). In summary, in patients who require continuous therapy and have failed to respond to a TNF antagonist, replacement with a different TNF antagonist may be of use under certain situations. This issue will deserve continuous reassessment with the arrival of new medications. © 2006 Gomez-Reino and Loreto Carmona; licensee BioMed Central Ltd