8,038 research outputs found
Optimised multi-camera systems for dimensional control in factory environments
As part of the United Kingdom’s Light Controlled Factory project, University College London aims to develop a large-scale multi-camera system for dimensional control tasks in manufacturing, such as part assembly and tracking. Accuracy requirements in manufacturing are demanding, and improvements in the modelling and analysis of both camera imaging and the measurement environment are essential. A major aspect to improved camera modelling is the use of monochromatic imaging of retro-reflective target points, together with a camera model designed for a particular illumination wavelength. A small-scale system for laboratory testing has been constructed using eight low-cost monochrome cameras with C-mount lenses on a rigid metal framework. Red, green and blue monochromatic light-emitting diode ring illumination has been tested, with a broadband white illumination for comparison. Potentially, accuracy may be further enhanced by the reduction in refraction errors caused by a non-homogeneous factory environment, typically manifest in varying temperatures in the workspace. A refraction modelling tool under development in the parallel European Union LUMINAR project is being used to simulate refraction in order to test methods which may be able to reduce or eliminate this effect in practice
The Fluorescence Detector of the Pierre Auger Observatory
The Pierre Auger Observatory is a hybrid detector for ultra-high energy
cosmic rays. It combines a surface array to measure secondary particles at
ground level together with a fluorescence detector to measure the development
of air showers in the atmosphere above the array. The fluorescence detector
comprises 24 large telescopes specialized for measuring the nitrogen
fluorescence caused by charged particles of cosmic ray air showers. In this
paper we describe the components of the fluorescence detector including its
optical system, the design of the camera, the electronics, and the systems for
relative and absolute calibration. We also discuss the operation and the
monitoring of the detector. Finally, we evaluate the detector performance and
precision of shower reconstructions.Comment: 53 pages. Submitted to Nuclear Instruments and Methods in Physics
Research Section
Three-dimensional scanning of specular and diffuse metallic surfaces using an infrared technique
For the past two decades, the need for three-dimensional (3-D) scanning of industrial objects has increased significantly and many experimental techniques and commercial solutions have been proposed. However, difficulties remain for the acquisition of optically non-cooperative surfaces, such as transparent or specular surfaces. To address highly reflective metallic surfaces, we propose the extension of a technique that was originally dedicated to glass objects. In contrast to conventional active triangulation techniques that measure the reflection of visible radiation, we measure the thermal emission of a surface, which is locally heated by a laser source. Considering the thermophysical properties of metals, we present a simulation model of heat exchanges that are induced by the process, helping to demonstrate its feasibility on specular metallic surfaces and predicting the settings of the system. With our experimental device, we have validated the theoretical modeling and computed some 3-D point clouds from specular surfaces of various geometries. Furthermore, a comparison of our results with those of a conventional system on specular and diffuse parts will highlight that the accuracy of the measurement no longer depends on the roughness of the surface
On the study of the single-stage hole-flanging process by SPIF
Recent studies show the capability of single-point incremental forming to perform successfully hole-flanging operations using
multi-stage strategies. The aim of this work is to investigate the ability of the SPIF process to perform hole-flanges in a single
stage, contributing to a better understanding of the formability of the sheet in this demanding situation. To this end, a series of
experimental tests in AA7075-O metal sheets are performed in order to evaluate the limiting forming ratio. The physical
mechanisms controlling sheet failure during the process are analyzed and discussed. In the test conditions studied this failure is
postponed necking followed by ductile fracture in the wall of the flange.Ministerio de Economía y Competitividad DPI2012-3291
Exploiting multimode waveguides for pure fibre-based imaging
We acknowledge support from the UK Engineering and Physical Science Research CouncilThere has been an immense drive in modern microscopy towards miniaturisation and fibre based technology. This has been necessitated by the need to access hostile or diffcult environments in-situ and in-vivo. Strategies to date have included the use of specialist fibres and miniaturised scanning systems accompanied by ingenious microfabricated lenses. We present a novel approach for this field by utilising disordered light within a standard multimode optical fibre for lensless microscopy and optical mode conversion. We demonstrate the modalities of bright-field and dark-field imaging and scanning fluorescence microscopy at acquisition rates allowing observation of dynamic processes such as Brownian motion of mesoscopic particles. Furthermore, we show how such control can realise a new form of mode converter and generate various types of advanced light fields such as propagation-invariant beams and optical vortices. These may be useful for future fibre based implementations of super-resolution or light sheet microscopy.Publisher PDFPeer reviewe
A THREE DIMENSIONAL (3D) VISION BASED DEFECT INSPECTION SYSTEM FOR GLUING APPLICATION
A Robot Vision System (RVS) is an adaptive and dynamic system that caters to a wide range of jobs where each involves a set of operations required to be done at a predetermined workstation. This research is focused on the development of a vision system to be integrated with KUKA arm robot. Pyramid object is used as a complimentary of the windscreen car as a model. It developed using plain cardboard with dimension of 15cm x 15cm. 2D matching application introduced to identify the characteristic of the object used in the system using CCD camera. Object used must be trained in training phase to create object template and used again in recognition phase for object classification. Then, two CCD cameras are used; placed at the top and front of the object to extract object’s edge location using Harris Point. Data extracted from it are used to find 3D coordination of each edge. Equation of straight line mostly used in this method to identify x, y and z coordinates. Data obtained from the system then used to give instruction to KUKA arm robot for gluing purposes. Pixel coordinates must be converted to robot coordinates for easier understanding by the robot. Three types of defect are trained as model templates and save to the memory known as bumper, gap and bubble defect. Each defect has special characteristic. Inspection system developed to identify problems occurs in gluing process. Template matching method used to call model trained in training phase to identify the uncertainties. Each defect occurs comes with its coordinate’s information for correction. Correction of defect consists of two phase; 1st CoD where correction is completed in first time and 2nd CoD where correction still need to be completed after the first correction. Data for all the process are recorded to prove that this algorithm made improvement with the previous research
Optical tweezer for probing erythrocyte membrane deformability
We report that the average rotation speed of optically trapped crenated
erythrocytes is direct signature of their membrane deformability. When placed
in hypertonic buffer, discocytic erythrocytes are subjected to crenation. The
deformation of cells brings in chirality and asymmetry in shape that make them
rotate under the scattering force of a linearly polarized optical trap. A
change in the deformability of the erythrocytes, due to any internal or
environmental factor, affects the rotation speed of the trapped crenated cells.
Here we show how the increment in erythrocyte membrane rigidity with adsorption
of ions can be exhibited through this approach.Comment: Published in Appl. Phys. Lett. 95, 233703 (2009); Two supplementary
multimedia files are available at the journal page:
http://link.aip.org/mm/APPLAB/1.3272269/083949aplv1.mov and
http://link.aip.org/mm/APPLAB/1.3272269/083949aplv2.mo
- …