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Frequency Scanning Interferometry (FSI) measurements PACMAN internal meeting 28/04/2014 Solomon William Kamugasa.

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Presentation on theme: "Frequency Scanning Interferometry (FSI) measurements PACMAN internal meeting 28/04/2014 Solomon William Kamugasa."— Presentation transcript:

1 Frequency Scanning Interferometry (FSI) measurements PACMAN internal meeting 28/04/2014 Solomon William Kamugasa

2 Frequency Scanning Interferometry (FSI) Measurements 1.Background concepts 2.Interferometry: (Displacement & FSI) 3.Sources of error in FSI 4.System components 5.How to determine 3D position using FSI 6.FSI in CLIC 7.Other applications of FSI 8.Ongoing work PACMAN internal meeting, 28/04/2014 Contents

3 Frequency Scanning Interferometry (FSI) Measurements Superposition: Resultant displacement produced by a number of waves at a point is the algebraic sum of displacements of the individual waves. Interference: Combination of 2 waves to form composite waves. PACMAN internal meeting, 28/04/2014 Constructive interference Background Destructive interference In phase Out of phase

4 Frequency Scanning Interferometry (FSI) Measurements PACMAN internal meeting, 28/04/2014 Background λ

5 Frequency Scanning Interferometry (FSI) Measurements Technique based on interference that measures properties of light waves such as wave length and optical path length. Requires: Coherent light source. Monochromatic light. Measures displacement by observing fringes. PACMAN internal meeting, 28/04/2014 Interferometry Coherent light source Detector Beam Splitter Movable Reflector Michelson Interferometer Fixed Reflector

6 Frequency Scanning Interferometry (FSI) Measurements PACMAN internal meeting, 28/04/2014 Displacement Interferometry Intensity minima Intensity maxima

7 Frequency Scanning Interferometry (FSI) Measurements PACMAN internal meeting, 28/04/2014 FSI PACMAN internal meeting, 28/04/2014 Tunable laser

8 Frequency Scanning Interferometry (FSI) Measurements Advantages Measures absolute distance. Beams can be interrupted as does not rely on fringe counting. Ability to measure several interferometers simultaneously. Disadvantages Tend to be less accurate than displacement interferometry (because it measurements are made relative to a physical reference). Accuracy reduced by drift errors (dominant source of error in FSI). PACMAN internal meeting, 28/04/2014 FSI

9 Frequency Scanning Interferometry (FSI) Measurements PACMAN internal meeting, 28/04/2014

10 Frequency Scanning Interferometry (FSI) Measurements Drift management Limited by control of environmental factors that cause drift. Using faster electronics that make measurements quicker. Using a stable reference such as Invar (nickel-iron alloy) with low CTE ≈ 1.2 ppm per °C in range of °C. Reference interferometer drift can be eliminated by replacing physical length reference. PACMAN internal meeting, 28/04/2014

11 Frequency Scanning Interferometry (FSI) Measurements PACMAN internal meeting, 28/04/2014 Measurement interferometer Reference interferometer Tunable laser Drift cancellation

12 Frequency Scanning Interferometry (FSI) Measurements PACMAN internal meeting, 28/04/2014

13 Frequency Scanning Interferometry (FSI) Measurements PACMAN internal meeting, 28/04/2014 Determining the position of fibre launchers

14 Frequency Scanning Interferometry (FSI) Measurements PACMAN internal meeting, 28/04/2014 Determination of fiducial coordinates

15 Frequency Scanning Interferometry (FSI) Measurements Physical length standard Reference needs to be calibrated in order to be traceable. Measurements rely on stability of reference. Alternative Wavelength of a He-Ne laser determined by energy levels in the gas atoms in the laser cavity (little dependence on ambient conditions). Atomic transitions lines in an absorption gas cell (weak dependence on ambient conditions). Benefit: Requires a single calibration, valid for the life of the instrument. PACMAN internal meeting, 28/04/2014 Reference Interferometer

16 Frequency Scanning Interferometry (FSI) Measurements PACMAN internal meeting, 28/04/2014 Measurement interferometer Each measurement interferometer consists of a quill (two parallel optical fibres and a beam splitter) and a reflector. Return fibre Delivery fibre Beam Splitter Retroreflector

17 Frequency Scanning Interferometry (FSI) Measurements Laser Narrow line width: Provides good fringe visibility. Wide tuning range: Better measurement precision. Diode laser most commonly used for FSI. Replaced dye lasers. PACMAN internal meeting, 28/04/2014 Main System components

18 Frequency Scanning Interferometry (FSI) Measurements Optical fibres Used to deliver light waves from laser to interferometer and to deliver the return signal from interferometer to photo detector. Light propagated through fibres by total internal reflection. Single mode fibres (D=8-10μm). Sharper light longer distances. PACMAN internal meeting, 28/04/2014 Main system components

19 Frequency Scanning Interferometry (FSI) Measurements Retroreflectors Incident light is reflected exactly in the direction of origin. Typically corner cube (3 mutually orthogonal surfaces). Retroreflectors are made of various materials. Aluminium pellets coated with gold to enhance reflectivity (ATLAS). Commercially - Glass prisms (utilise total internal reflection). Mirror reflectors are also available. PACMAN internal meeting, 28/04/2014 Main system components

20 Frequency Scanning Interferometry (FSI) Measurements PACMAN internal meeting, 28/04/2014

21 Frequency Scanning Interferometry (FSI) Measurements CMMs show systematic deviations resulting from aging & elastic deformations etc. FSI will be used to continuously monitor the CMM to provide control of systematic deviations. PACMAN internal meeting, 28/04/2014 Monitoring and Control

22 Frequency Scanning Interferometry (FSI) Measurements PACMAN internal meeting, 28/04/2014

23 Frequency Scanning Interferometry (FSI) Measurements FSI at ATLAS Used to remotely monitor shape changes of the SCT. Measurement precision of 1μm. 3D coordinate reconstruction to 10μm. 842 measurement interferometers. Radiation-hard low mass components. No maintenance over 10 years. Fibres 100m long from interferometer to detector/laser. PACMAN internal meeting, 28/04/2014 Other FSI applications ATLAS Experiment © 2014 CERN

24 Frequency Scanning Interferometry (FSI) Measurements Work in progress Develop fiducials measureable by FSI, Micro-triangulation & CMM. Why? More redundancy and ability to detect faults. Study the mechanics of fibre ends and targets in order to determine their systematic offsets/errors and those of the target holders. Study various configurations of the FSI network in order to select the best one through simulations. Extrapolate to a portable solution. PACMAN internal meeting, 28/04/2014 Project 1.2

25 Frequency Scanning Interferometry (FSI) Measurements Coe P. A (2001) An Investigation of Frequency Scanning Interferometry for the alignment of the ATLAS semiconductor tracker. Dphil thesis, University of Oxford. Dale J. (2009) A Study of Interferometric Distance Measurement Systems on a Prototype Rapid Tunnel Reference Surveyor and the Effects of Reference Network Errors at the International Linear Collider. Dphil thesis, University of Oxford. Griffet S., Cherif A., Kemppinen J., Mainaud Durand H., Rude V., Sterbini G. Strategy and validation of fiducialisation for the pre-alignment of CLIC components, CERN Geneva, Switzerland. Griffet S (2010) Fiducialisation and Dimensional Control: Study of existing means and expected performances. EDMS Warden M.S (2011) Absolute distance metrology using frequency swept lasers. DPhil thesis, University of Oxford. Absolute Multiline®-Technology A revolution in length metrology. Available on Indico, Presented by Mainaud Durand H. PACMAN internal meeting, 28/04/2014 References


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