Paulo Torrão Fiadeiro

Effects of operational conditions on the supercritical solvent impregnation of acetazolamide in Balafilcon A commercial contact lenses

In this work we employed a supercritical solvent impregnation (SSI) process using a scCO(2)+EtOH (5% molar) solvent mixture to impregnate acetazolamide (ACZ) into commercially available silicone-based soft contact lenses (Balafilcon A, Pure Vision, Bausch & Lomb). Contact lenses (SCLs) drug-loading was studied at 40°C and 50°C, and from 15 MPa up to 20 MPa, and using low depressurization rates in order to avoid any harm to SCLs. The effect of impregnation processing time on the loaded ACZ amounts was also studied (1, 2 and 3h). In vitro drug release kinetics studies were performed and the released ACZ was quantified spectrophotometrically. Several analytical techniques were employed in order to characterize the processed and non-processed SCLs in terms of some of their important functional properties. Obtained results demonstrated that ACZ-loaded therapeutic Balafilcon A SCLs can be successfully prepared using the employed SSI process. Furthermore, it was possible to control ACZ loaded amounts and, consequently, to adjust the final ACZ release levels into the desired therapeutic limits, just by changing the employed operational conditions (P, T, processing time and depressurization rate) and without change some of their most important thermomechanical, surface/wettability and optical properties. Obtained soft contact lenses can be potentially employed as combined biomedical devices for simultaneous therapeutic and correction of refractive deficiencies purposes.

Fusing iris and periocular information for cross-sensor recognition

Announcement of an iris and periocular dataset, with 10 different mobile setups.Mobile biometric recognition approach based on iris and periocular information.Improvements from a sensor-specific color calibration technique are reported.Biometric recognition feasibility over mobile cross-sensor setups is shown.Preferable mobile setups are pointed out. In recent years, the usage of mobile devices has increased substantially, as have their capabilities and applications. Extending biometric technologies to these gadgets is desirable because it would facilitate biometric recognition almost anytime, anywhere, and by anyone. The present study focuses on biometric recognition in mobile environments using iris and periocular information as the main traits. Our study makes three main contributions, as follows. (1) We demonstrate the utility of an iris and periocular dataset, which contains images acquired with 10 different mobile setups and the corresponding iris segmentation data. This dataset allows us to evaluate iris segmentation and recognition methods, as well as periocular recognition techniques. (2) We report the outcomes of device-specific calibration techniques that compensate for the different color perceptions inherent in each setup. (3) We propose the application of well-known iris and periocular recognition strategies based on classical encoding and matching techniques, as well as demonstrating how they can be combined to overcome the issues associated with mobile environments.

Color constancy by asymmetric color matching with real objects in three-dimensional scenes.

Color matching experiments use, in general, stimuli that are poor representations of the natural world. The aim of this work was to compare the degree of color constancy for a range of illuminant pairs using a new matching technique that uses both real objects and three-dimensional (3-D) real scenes. In the experiment, observers viewed a 3-D real scene through a large beamsplitter that projects on the right-hand side of the scene (match scene), the virtual image of a 3-D object (match object) such it appeared part of the scene. On the left-hand side of the scene (test scene), observers viewed a symmetrical scene containing a test object identical to the match object. Test and match objects were both surrounded by the same reflectances with identical spatial arrangement. The illuminant on the test scene had always a correlated color temperature of 25,000 K. The illuminant on the match scene could be any of seven different illuminants with correlated color temperatures in the range 25,000 K-4000 K. In each trial, the observers, who were instructed to perform surface color matches, adjusted the illuminant on the match object. Constancy indices were very high (0.81-0.93), varied with the color of the match object, and increased with the extent of the illuminant change. Observers mismatches, however, were independent of the extent of the illuminant change.

Effect of Scene Dimensionality on Colour Constancy with Real Three-Dimensional Scenes and Objects

The effect of scene dimensionality on colour constancy was tested with real scenes and objects. Observers viewed a three-dimensional (3-D) scene, or its two-dimensional (2-D) planar projection, through a large beam-splitter that projected the virtual image of a real test object (a cube or its 2-D projection) so that it appeared part of the scene. Test object and scene could be illuminated independently with high chromatic precision. In each trial, the illuminance of the scene changed abruptly from 25 000 K to 6700 K and the illuminant of the test object changed either consistently or inconsistently with it by a variable quantifiable amount. Observers had to decide whether the test object underwent a change in its materials. The extent of constancy obtained in the experiment was not influenced by scene dimensionality and varied significantly with the colour of the test object. These results suggest that color constancy in the conditions tested here may be determined by local spectral quantities.

Effect of scene complexity on colour constancy with real three-dimensional scenes and objects

The effect of scene complexity on colour constancy was tested with a novel technique in which a virtual image of a real 3-D test object was projected into a real 3-D scene. Observers made discriminations between illuminant and material changes in simple and complex scenes. The extent of colour constancy achieved varied little with either scene structure or test-object colour, suggesting a dominant role of local cues in determining surface-colour judgments.

Comparative analysis of autofocus functions in digital in-line phase-shifting holography

Numerical reconstruction of digital holograms relies on a precise knowledge of the original object position. However, there are a number of relevant applications where this parameter is not known in advance and an efficient autofocusing method is required. This paper addresses the problem of finding optimal focusing methods for use in reconstruction of digital holograms of macroscopic amplitude and phase objects, using digital in-line phase-shifting holography in transmission mode. Fifteen autofocus measures, including spatial-, spectral-, and sparsity-based methods, were evaluated for both synthetic and experimental holograms. The Fresnel transform and the angular spectrum reconstruction methods were compared. Evaluation criteria included unimodality, accuracy, resolution, and computational cost. Autofocusing under angular spectrum propagation tends to perform better with respect to accuracy and unimodality criteria. Phase objects are, generally, more difficult to focus than amplitude objects. The normalized variance, the standard correlation, and the Tenenbaum gradient are the most reliable spatial-based metrics, combining computational efficiency with good accuracy and resolution. A good trade-off between focus performance and computational cost was found for the Fresnelet sparsity method.

Optical Estimation of a Set of Pilling Coefficients for Textile Fabrics

This paper presents the results obtained using an experimental system, based on optical triangulation, which enabled topographic reconstructions of textile fabric surfaces. Consequently, one could evaluate and quantify the pilling formation through the optical estimation of a set of pilling coefficients. The proposed method was found to be precise, robust and systematic, and may constitute an alternative and/or complementary approach to quantify the pilling formation.

Virtual subjective pilling evaluation: an alternative

This paper reports an alternative approach for the evaluation of fabric pilling. On this approach, orthogonal projections of the three-dimensional (3D) fabric images are used directly to virtually evaluate the pilling formation of the fabrics. The 3D images of the fabrics are obtained through the reconstruction of the topography of the real textile fabrics. For that, a dual-scanning optical system (triangulation system) was used, which was developed and implemented by our research team. This evaluation approach is performed by comparing the appearance of the orthogonal projections of the 3D fabric images with the same photographic standard sets used in the conventional subjective method. For the validation of the obtained results with this methodology, a comparison was carried out relative to a reference subjective evaluation. This reference evaluation corresponds to a subjective evaluation of the fabrics originally performed by a panel of experts. A comparison was also performed between the results obtained with this methodology and those obtained by an objective evaluation. This objective evaluation corresponds to the automatic attribution of the equivalent pilling grade to the fabrics, based on the calculation of the total volume of pilling formed in their surfaces. The final results obtained with the described methodology were showed to be globally in agreement with both the reference subjective and the objective evaluations. Subsequently, this method shows potential as an alternative approach for the virtual subjective evaluation of fabric pilling.This paper reports an alternative approach for the evaluation of fabric pilling. On this approach, orthogonal projections of the three-dimensional (3D) fabric images are used directly to virtually evaluate the pilling formation of the fabrics. The 3D images of the fabrics are obtained through the reconstruction of the topography of the real textile fabrics. For that, a dual-scanning optical system (triangulation system) was used, which was developed and implemented by our research team.This evaluation approach is performed by comparing the appearance of the orthogonal projections of the 3D fabric images with the same photographic standard sets used in the conventional subjective method.For the validation of the obtained results with this methodology, a comparison was carried out relative to a reference subjective evaluation. This reference evaluation corresponds to a subjective evaluation of the fabrics originally performed by a panel of experts. A comparison was also performed between the results obtaine...

Subjective and Objective Pilling Evaluations of Textile Fabrics: A Comparison

This paper addresses a comparison between three different approaches used to evaluate a set of different textile fabric samples in terms of pilling formation. Originally, the set was subjectively evaluated by a panel of experts, being that, our reference evaluation. Then, the same set of fabrics was analysed by a dual-scanning optical system which has been implemented by our team to reconstruct 3D images of the topography of the fabrics. With the obtained range data, an objective evaluation of the pilling formation was carried out based on the total pilling volume and the results showed to be in agreement with the original subjective evaluation. In this paper, our purpose is to establish a correspondence model in order to automatically attribute the equivalent pilling grade. Furthermore, the same set of fabrics was then subjectively reevaluated by different observers for comparison with the reference evaluation, and the results obtained by the correspondence model.

Iris Recognition: Preliminary Assessment about the Discriminating Capacity of Visible Wavelength Data

The human iris supports contact less data acquisition and can be imaged covertly. These factors give raise to the possibility of performing biometric recognition procedure with-out subjects’ knowledge and in uncontrolled data acquisition scenarios. The feasibility of this type of recognition has been receiving increasing attention, as is of particular interest in visual surveillance, computer forensics, threat assessment, and other security areas. In this paper we stress the role played by the spectrum of the visible light used in the acquisition process and assess the discriminating iris patterns that are likely to be acquired according to three factors: type of illuminant, it’s luminance, and levels of iris pigmentation. Our goal is to perceive and quantify the conditions that appear to enable the biometric recognition process with enough confidence.