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This study presents the optical design of light guide prisms for automotive tail light applications to obtain the optimum luminous intensity and the illuminance uniformity. The design was achieved using optical design software, SPEOS. By considering the axial luminous intensity and legal requirements, the optimum prism angles of light guides were determined by simulations. After determining the prism angles, the effect of different surface roughness on the luminous intensity and the illuminance uniformity was investigated. The light guides designed by considering data from the simulation were manufactured as prototypes and their photometrical measurements were made. These measurements were compared to the simulation results. It was observed that simulation and prototype results are well in agreement with each other. Furthermore, it was found that as the surface roughness increases both the luminous intensity decreases and the illumination becomes more uniform. T.C. Sanayi ve Teknoloji Bakanlığı (0143.STZ.2013-1) Farba Otomotiv A. Ş.

International audience; The paper presents new results about the geometry of topological interlocking masonries and some possibilities they present to build without formwork. Construction without the use of formwork may be an important issue concerning both productivity increase and decreasing of waste generated on a construction site. Due to the development of computational design and robotics in the construction industry, it makes sense to (re)explore innovative design and process of complex masonry structures. The design of this kind of masonry is standard for planar structures, and in this paper, a generalization is proposed for the parametric design of curved structures. To achieve this, a criterion for translationally interlocked structure based on quadrilateral meshes is exhibited. The application of this criterion is then extended to masonry structures derived from other patterns. Physical prototypes of topological interlocking masonry are also presented. One of these designs seems to allow construction without formwork.

Contemporary personal mobile devices support a variety of authentication approaches, featuring different levels of security and usability. With cameras embedded in smart glasses, seamless, hands-free mobile authentication based on gaze is possible. Gaze authentication relies on knowledge as a secret, and gaze passwords are composed from a series of gaze points or gaze gestures. This paper investigates the concept of free-form mobile gaze passwords. Instead of relying on gaze gestures or points, free-form gaze gestures exploit the trajectory of the gaze over time. We collect and investigate a set of 29 different free-form gaze passwords from 19 subjects. In addition, the practical security of the approach is investigated in a study with 6 attackers observing eye movements during password input to subsequently perform spoofing. Our investigation indicates that most free-form gaze passwords can be expressed as a set of common geometrical shapes. Further, our free-form gaze authentication yields a true positive rate of 81% and a false positive rate with other gaze passwords of 12%, while targeted observation and spoofing is successful in 17.5% of all cases. Our usability study reveals that further work on the usability of gaze input is required as subjects reported that they felt uncomfortable creating and performing free-form passwords.

The project “Brick-topia” was based on a combination of the latest structural analysis and form-finding computational tools with traditional, cheap and effective construction techniques. It is the result of innovation to fight against budget and time. The initial budget was 3000 euros and only seven weeks was the time to look for sponsors, design the pavilion, plan the construction phases and build it. The whole process of designing, decision on the materials, structural analysis and construction is presented in the paper, including exploration on new form-finding methods to redesign a project in situ and research on a new formwork system using scaffolding, cardboard, wire and steel rods and having a cutter as main tool., Case Studies in Structural Engineering, 2, ISSN:22143998

Raman spectroscopy is a powerful tool for analytical measurements in many applications. Traditional Raman spectroscopic analyses require bulky equipment, considerable time of signal acquisition and manual sampling of substances under test. In this paper, we take a step from bulky and manual consuming laboratory testing towards lab-on-chip (LOC) analyses. We miniaturize the Raman spectroscopic system by combining a free-form reflector based polymer LOC with a customized Raman probe. By using the confocal detection principle, we aim to enhance the detection of the Raman signals from the substance of interest due to the suppression of the background Raman signal from the polymer of the chip. Next to the LOC we miniaturize the external optical components, surrounding the reflector embedding optofluidic chip, and assemble these in a Raman probe. We evaluate the misalignment tolerance of internal optics (LOC) and external optics (Raman probe) by non-sequential ray tracing which shows that off-axis misalignment is around +or-400mum and the maximum working distance of our Raman probe is 71mm. Using this probe, the system could be implemented as a portable reader unit containing the external optics, in which a low-cost, robust and mass manufacturable microfluidic LOC containing a freeform reflector is inserted, to enable confocal Raman spectroscopy measurements.

Free-form solar cells are cells of unconventional shapes (e.g. hexagonal, leaf-shaped etc). Their flexible shape adds to the aesthetics of the surroundings as well as allows to place them over objects where conventional solar cells might not fit. Evidently, these cells need to be efficient as well, and one of the important factors that controls their performance is the front metallization design. In this paper, we present the application of topology optimization (TO) to optimize the front metallization patterns for free-form solar cells. TO distributes the electrode material on the solar cell front surface in an efficient manner, such that the total power output is maximized. To demonstrate the capability of the proposed methodology, we use it to optimize front metal grids for several complex solar cell shapes e.g. circular, hexagonal, leaf-shaped, motorbike fairings, etc. The results presented here demonstrate the capability of TO to generate efficient designs for these free-form shapes. cop. 2015 The Authors.

This paper presents an optimization algorithm for the design of structurally efficient free-form reciprocal structures. Because of the geometric complexity of reciprocal structures, only a few structural studies have been carried out so far, and we have a limited knowledge of the relation between geometry and structural behaviour in reciprocal structures. This study takes advantage of the preceding work carried by the author on the Reciprocalizer, a software tool for the generation of reciprocal geometries. The Reciprocalizer has been included into a structural optimization algorithm for the generation of structurally efficient free-form reciprocal structures.

When working with 3D scanner devices, one of the most critical problems is usually the low quality of the point cloud provided by the scanning device. This problem mainly consists of the following two aspects. The first one is surely the choice of the strategy used to acquire the object shape. Most of the times, the selected strategy is based on selective sampling. This choice proved to be valid, especially when working with Free-Form surfaces: by using a selective sampling strategy is in fact possible to limit point density increase to those regions showing high morphological complexity. The second aspect is the difficulty of identifying which 3D scanner device is the one that better fulfils the specific application needs, which vary depending on the specific scenario in which the costumer/user works (resolution, accuracy, …). As far as this last issue is concerned, the presence of many different acquisition technologies and devices on the market is a source of confusion for the users, who sometimes choose the wrong solution instead of finding the most efficient one. Hence, in order to support the potential users in their selection, this paper aims to propose a solution able to integrate the morphological analysis of the object acquired with the costumer needs (resolution, accuracy, …) and with the 3D scanner performances in order to help users to identify the optimal solution.

A new universal non-contact measurement machine design for measuring free-form optics with 30 nm expanded uncertainty is presented. In the cylindrical machine concept, an optical probe with 5 mm range is positioned over the surface by a motion system. Due to a 2nd order error effect when measuring smoothly curved surfaces, only 6 position measurement errors are critical (nanometer level). A separate metrology system directly measures these critical errors of the probe and the product relative to a metrology frame, circumventing most stage errors. An uncertainty estimation has been performed for the presented design, including a calibration uncertainty estimation and a dynamic analysis. Machine dynamics certainly cause relative motion between probe and product, but due to the non-contact nature of the measurement and the short metrology loop, these motions do not cause significant measurement errors. The resulting shape measurement error for aspheres up to medium free-forms is between 24 and 37 nm, and 30 - 85 nm for medium to heavily free-form surfaces. The suitability of the proposed design is herewith confirmed. A detailed design and a prototype of the machine are currently being developed.