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Bernhard G. Zagar
A schileren system for in-line quality control in a film extrusion process

This paper addresses the problems arising in continuous film extrusion of thin foils that need to result in optical quality but due to process still not completely understood give suboptimal quality of the resultant foil. The foils show more or less severe chatter marks dependent on certain system parameters like feed rate of the product, temperature of the product casted, spinning rate and differential spinning rate of rolls, cooling rate and so on. An inline capable optical quality measurement system is devised that allows to continuously assess the product quality within seconds after the foil is extruded from the casting unit, thus allowing rapid corrective actions if quality declines below a set standard. It also allows for a continuous documentation of the amount of residual chatter marks for each and every inch of product. The system is based upon a schlieren optical setup able to resolve schlieren-caused refraction of collimated light of less than 1 second of arc.

N. J. Vasa, I. A. Palani, Rajesh Kona, M. Singaperumal
Development of optical gas sensors for emission monitoring

The global increase in N2O and CO2 levels, which contribute to the greenhouse effect, has been attributed to combustion of biomass and fossil fuels. An optical sensor system capable of measuring concentrations of these species and O2 might be incorporated into combustion-control applications to reduce pollutant emissions and increase fuel efficiency. In addition to measuring the gases in the atmosphere and pollution from traffic and industry, it is important to monitor the work environment, industrial process. A compact, widely tunable coherent optical source based on a difference frequency generation technique in a quasi-phase-matched nonlinear crystal pumped by two single-frequency laser diodes for the detection of various gases is reported. A novel approach of using commercially available fibercoupled super-luminescent diode (SLD) along with a spectrometer is also proposed for such application.

T. S. Sriranga, R. Samuel, Raghunatha Behara, P. Radhakrishnan
Dynamic displacement measurements by videogrammetry

Photogrammetry and Videogrammetry techniques are being applied for a variety of spacecraft structural applications including shape, dimensional stability and dynamic displacement measurements. Static object measurements serve to provide either shape or distortions in a statically loaded structure during qualification tests. Dynamic measurements are essential during motion measurement and determination of mode shape of flexible appendages and Synthetic Aperture Radar antenna panels. Configuration of a PC-based image measurement and processing system for motion measurements using two time-synchronized video cameras is reported here. Time synchronization hardware details, automated image processing using video module of PhotoModeler as also visualization are explained in this paper. The number of images, and target points that can be used for measurement are only limited by the PC hardware infrastructure. Displacement measurements have been done on targets mounted on crosshead of an X-Y motion system to ascertain the accuracy of measurements within the range of two video cameras. Laser Tracker was used to verify the camera measurements.

K. Ashokan, K. Ramesh
Smoothing of isochromatic data of stereolithography built spline shaft

Digital Photoelasticity is an experimental method for determining stresses in 2D and 3D models. Recently Stereolithography, one of the Rapid Prototyping (RP) techniques, is being used widely to produce 3D photoelastic models of complicated shapes directly from Computer Aided Design (CAD) models. But with such models, the fringe data obtained is not continuous as in the case of conventional models. This is due to the porous nature of the stereolithography models attributed to the way in which the models are built. To address this issue, the use of various smoothing techniques is explored in this paper for better data estimation. The performance of different 2D smoothing techniques viz. averaging filter, median filter and Wiener filter on the quality of the fringe order data obtained for a slice cut from the stress frozen model of stereolithography built spline shaft is compared.

Yu. V. Chugui, V. S. Bazin, A. G. Verkhogliad, S. V. Kalichkin, V. E. Kalikin, S. N. Makarov, S. G. Savkov
Optical measuring technology for oil drilling platform

An opto-electronic measurement system for continuous monitoring of displacements and analysis of the friction pendulum bearings for the oil-drilling platforms is presented. Measuring principle of the system is based on target image formation by camera and digital image processing. The passive part of the system (optical target) is fixed on one part of construction while active part - a field measurement sensor (FMS) - is installed on another part of construction that moves relative to the first one. The system is certified as a measuring tool for the use in explosive environments.

A. M. Kovalev, Yu. V. Chugui, M. V. Stepanov, V. E. Lischenko
On geometric structure of visual space

The stages of visual space forming in human mind are considered. Relationships between distances in Euclidean and hyperbolic visual spaces as well as in Klein and Poincare models have been found. A variant of anisotropic visual space is presented.

Muralidhara, S. Majumder, N. J. Vasa, M. Singaperumal
Influence of gap voltage and tool material on micro geometry produced on silicon wafer using micro-EDM

In the present work, a Micro EDM (Micro Electro Discharge Machine) is developed in-house with piezoactuated adaptive tool feed mechanism and investigations on Silicon wafer machining is carried out at different machining conditions and with copper and tungsten tool materials. Kerosene is used as the dielectric medium. The influence of the tool feed mechanism on the surface roughness is investigated with different feed back gap voltages and it was found that gap feed back voltage of 23V generates better surfaces when compared to lower feed back gap voltages. The effect of sparking frequency on surface roughness is investigated and it was found that higher frequencies generate a good surface with lower surface roughness value. Side Spark Gap (SSG) is evaluated for copper and tungsten tool materials at different gap voltages and duty cycles. It was found that SSG increases with applied gap voltage. There was no much variation in SSG at different duty cycles. Copper tool material generates higher SSG compared to Tungsten tool.

Kiyoshi Takamasu, Keisuke Yoshida, Tatsuya Senoo, Xin Chen, Kiyoshi Kotani, Satoru Takahashi
Calibration of 6 DOF parallel mechanism driven by planar motors

For high flexibility of assembly works, 6 DOF mechanisms are useful for supporting assembly workers. The 6 DOF mechanism needs to move in sub-mm and sub-degree absolute positioning accuracy over wide working area. For this purpose, we developed a novel 6 DOF parallel mechanism driven by 3 planar motors and a novel calibration method for this mechanism. The calibration experiments using CMM are performed and the results of the calibrations are evaluated.

Albert Weckenmann, J. Hoffmann
A novel pseudo-tactile 3D zero indicating probe for nano metrology

Today several coordinate measuring machines for the measurement of microparts have been developed, some of them are commercially available already. State of the art are axes resolutions of a few nanometers at a measuring volume of a few cm³, what can be achieved by laser interferometry or scale based length measuring systems. However, the most critical part of a conventional CMM, the usually tactile probing system, is difficult to be scaled down for the measurement of microparts. Due to the small contact area between a micro tip ball of e. g. 0.1 mm diameter and a workpiece, Hertzian stress can get significant even at very low static contact forces. Depending on approach velocity and moving mass of the probing system, dynamic reactions during deceleration of the probing element upon contact may exceed the yield stress of the probed component and cause damages. When using very small probing elements this can only be avoided by drastically reducing static and dynamic probing forces.
To achieve this, a novel 3D probing system (patent pending) was designed, which detects and measures vicinity to the work piece surface without actually touching it by the means of tunneling current measurement. Therefore a highly stabilized bias voltage is applied between a conductive work piece and a special probing element that leads to a weak, but measurable current flow if the separation between these electrodes is in the order of a few nanometers. Due to the exponential dependence of the tunneling current from separation, a radial resolution far below 1 nm could be achieved. The system has been set-up, integrated into a long range nano positioning system and tested. It is capable of conventional 2.5D STM measurements with a maximum measuring range of 25 mm x 25 mm x 5 mm, but also coordinate measurements of true 3D geometry.

S. Minamiguchi, S. Usuki, S. Takahashi, K. Takamasu
Thin film thickness measurement for evaluation of residual layer of nano-imprint lithography using near-field optics

Since a thin resin film with thickness of several 10nm remains as a residual film between the imprinted patterns and the substrate in the nano-imprint lithography process, it should be eliminated by reactive ion etching. To implement the etching process with high accuracy and to maintain the original patterns for realizing NIL as a highly reliable lithography process of semiconductor, it is seriously necessary to measure the thickness of the residual resin film before the etching process. In this article, we proposed a novel optical measurement method for the residual film thickness based on the near-field optics. As a result, the near-field optical responses are affected in relation to the film thickness and a distance between the resin surface and a fiber apex. We concluded that it is possible to measure the thin film thicknesses within 80nm with a few nm resolution by evaluating the near-field optical responses.

Page 170 of 977 Results 1691 - 1700 of 9762