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Advanced Imaging Magazine

Updated: July 8th, 2008 05:26 PM CDT

Runner Up - OPERA: The Oscillation Project with Emulsion-tRacking Apparatus

Category: Machine Vision
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By Advanced Imaging Editorial Staff

European Organization for Nuclear Research (Genève, Switzerland)
Laboratori Nazionali del Gran Sasso (Assergi, Italy)
Tecnocut SpA (Calusco d’Adda, Italy)
(Nominated by Ignazio Piacentini, ImagingLab Srl, Lodi, Italy)

The Challenge:

The OPERA experiment relies, in part, on a massive lead/photographic emulsion target used in long-baseline neutrino research. Scientists at the European Organization for Nuclear Research shoot neutrinos at the Laboratori Nazionali del Gran Sasso, some 700 kilometers (435 miles) away, where a very large modular detector is located. The detector—weighing 1,635 tonnes (1,800 tons)—is made of 206,336 bricks, with each brick having 57 photographic plates interspersed with 56 lead sheets.

Brick assembly initially was based on “blind” robotics. From early trials, it became clear the required alignment accuracy of 50 microns (0.002 inches) could not be achieved. A machine vision solution was needed.

The Solution:

Two high resolution CCD cameras are employed together with pulsed, near-infrared illumination (well outside the spectral response curve of the sensitive emulsion plates). One camera images a brick edge while the other covers a smaller area, roughly five emulsion/lead pairs. Image analysis software assesses a series of parameters.

The Tools Used:

  • Allied Vision Technologies (Stadtroda, Germany) Marlin-145 B2, 1392×1040-pixel, monochrome CCD camera
  • Various optical components from Edmund Optics (Barrington, NJ)
  • Micas (Oelsnitz, Germany) vertical translation stage/camera carrier
  • National Instruments Compact Vision System-1454; LabVIEW, Vision Assistant; and Vision Builder software

The Difference It Made:

Neutrino events are very rare occurrences. Bricks with misaligned emulsion plates do not allow accurate reconstruction of the event trajectory. Off-the-shelf imaging hardware and software enabled a solution to be realized and retrofit with less than three months’ effort.



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