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 CLAM preliminary results

 CLAM preliminary results. Miroslav Šulc Technical University of Liberec. Continuous Line Alignment-Monitoring method. Rectangular grid, made from retro-reflective strips, is illuminated by high luminosity LEDs.

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 CLAM preliminary results

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  1.  CLAM preliminary results Miroslav Šulc Technical University of Liberec Compass meeting

  2. Continuous Line Alignment-Monitoring method • Rectangular grid, made from retro-reflective strips, is illuminated by high luminosity LEDs. • Images of this grid are reflected by RICH mirrors and recorded by 4 cameras CANON EOS 5D, equipped by EF 24mm/2.8 objectives. • Tilt of mirror can change a position of lines at image Compass meeting

  3. Beam pipe Jura topSaleve topJura bottomSaleve bottom Compass meeting

  4. Horizontal overlap about 3x5 mirrors • Vertical overlap impossible – two tilted segments of spherical mirrors Compass meeting

  5. Compass meeting

  6. Scheme of the control system Driven by PC Stefano Takekawa HV on PMTs is off in the time of CLAM measurement Compass meeting

  7. σ Photo taking conditions • Both dark and light areas must be homogenous what concerns intensities. • The standard deviation σs (or σg) of the pixel intensities (taken from histogram) in both areas must be small. The function f= Ig-Is + γ/σsσg must receive a maximum. Compass meeting

  8. Shutter is open 20 sec to avoid camera vibration; the best LED illumination time is 4-5 sec for 1 LED, 2 sec for 2 LEDs. • For searching of position of edges in images is no serious problem with shorter and longer exposition times 2 s 5s 10s Compass meeting

  9. 5 pixel shift • It is equivalent to 0.7 mrad tilt Compass meeting

  10. Relative measurement • Matlab sofware is used to compare images • Positions of cameras are without changes • The most of mirrors are untilted • Some mirrors were tilted still before closing vessel • Some mirrors ?? are tilted during 2007 run. Detail analyses necessary. Compass meeting

  11. Z Z X X Y Y Absolute measurement • Recalculate mirrors positions from Compass coordinates to another ones with respect to center of camera lens • Marek Švec diploma theses Compass meeting

  12. Alignment of camera axes was made with help of some control points from Jean-Christophe Gayde measurement • Mirror was placed to designed position with help of laser based distance meter with accuracy 1mm and special laser beam reflection method • Fine positioning was made by comparing of original photo from RICH and our one made by camera in laboratory • Mirror positioning is time consuming process • Line shifts vs. mirror tilts were measured by laser interferometer – quick experiment Compass meeting

  13. Fine alignment Compass meeting

  14. 1 pixel shift per 30 angular seconds • We have information for both horizontal and vertical tilt vs. image pixel shift for each mirror Compass meeting

  15. Image reconstruction by spherical projection • The paracatadioptric camera consists from combination of parabolic shaped mirror with a camera inducing an orthographic projection • J. P. Barreto, Helder Araujo, Fitting conics to paracatadioptric projections of lines, Computer Vision and Image Understanding 101 (2006), 151–165 • To calculate grid lines position from the images and compare these calculated ones with position from calibration (Jean-Christophe Gayde). The displacement of lines is proportional to the mirror tilt • Lukas Steiger PhD work Compass meeting

  16. Conclusions • CLAM is working method • The analyses of images will be continue • RICH mirrors seem be stable • Same mirrors exhibit initial misalignment • CLAM method can be used for correction of mirror position with accuracy Compass meeting

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