1. Photogrammetry for stress analysis of the hydrogen absorber window

2. Purpose of Photogrammetric Measurememnts zMeasure the deflection of the window (delta Z) to compare with the delta Z computed by FEA Delta Z Pressure = 0 PSI Pressure = X PSI

3. FEA input: applied pressure

4. FEA output: resultant deflection

5. Window testing input: apply pressure

6. Window testing output: resultant deflection

7. Desired features Adequate resolution Typical deflection: At operating pressure~ 250um Max deflection~2200um Non-contact targeting To avoid altering the window’s properties

8. Solution Adequate resolution Use a photogrammetric system 10um resolution Non-contact targeting Use a projection targeting system

9. What is photogrammetry? Photogrammetry is 3-dimensional coordinate measuring technique that uses photographs as the fundamental medium for metrology (or measurement).

10. Photogrammetic system yV-STARS yVideo Stereo Triangulation And Resection Software yGeodetic Services, Inc.

11. V-STARS V-STARS uses high-resolution video cameras instead of film cameras. This is also referred to as videogrammetry or digital photogrammetry.

12. 3 pieces of equipment required 1) Camera 2) Targets 3) Software

13. Camera INCA INtelligent CAmera Image size : 18.2 x 27.6 mm Resolution (pixels): 2044 x 3072 Lens focal length: 17mm Field of view: 56 deg x 76 deg

14. INCA camera

15. 3 pieces of equipment required 1) Camera 2) Targets 3) Software

16. Targets a)Reference targets (Autobar and coded targets) b)Object targets (we chose Pro-Spot projector) c) Scale bars

17. Autobar

19. Coded targets

20. Targets a)Reference targets (Autobar and coded targets) b)Object targets (we chose Pro-Spot projector) c) Scale bars

21. PRO-SPOT projector

23. Projected targets

24. PRO-SPOT projection targeting system Projector strobe Camera flash 24ms 14ms10ms0ms

25. Targets a)Reference targets (Autobar and coded targets) b)Object targets (we chose Pro-Spot projector) c) Scale bars

26. Scale bars

27. 3 pieces of equipment required 1) Camera 2) Targets 3) Software

28. V-STARS input V-STARS measures the target positions on CCD a)Reference targets (Autobar and coded targets) b)Object targets (we chose Pro-Spot projector) c) Scales

29. V-STARS analysis - input

30. V-STARS analysis Using the measured the target positions, V-STARS performs: a)Resection (determines camera positions) and camera calibration b)Triangulation to determine the x,y,z position of each target c) Dimensions the measurements

31. V-STARS output x,y,z position of each target

32. V-STARS output

33. V-STARS output with quadrant information

34. V-STARS output with azimuthal information

35. How does digital photogrammetry work? Step 1 Determine camera locations from known (identifiable by the software) targets Step 2 Determine unknown target locations from known camera positions

36. Step 1 Determine camera location Unknown CAMERA location Known, fixed focal length Known TARGET location Known TARGET location CCD image plane

37. Step 2 Determine unknown target locations Unknown TARGET location Known CAMERA location Known CAMERA location

38. Resolution is a function of: zThe resolution and quality of the camera zThe size of the object being measured zThe number of photographs taken zThe geometric layout of the pictures zCorrectness of the lens calibration

39. Resolution VSTARS can measure to better than 1/50 of a pixel How? The software finds the centroid of an intensity weighted analysis of the target. Optimally, 50 or more pixels/target are used for making that determination

40. Resolution So, accepting this: For INCA (2000 x 3000 pixel camera): (2000 pixels/field width) * (1/50 parts/pixel) = 1part / 100,000 Assuming the field of view is 1 meter in diameter, this corresponds to a resolution of 1part/100,000 = 1m/100,000 = 10um which is adequate for our purposes:

41. Sources of error zV-STARS analysis zDetermination of pressure zFEA

42. Error: V-STARS analysis zV-STARS calculates the rms error for all 3 dimensions Unknown object TARGET location Camera 1Camera 2 Note: V-STARS discards all 2-ray intersections as trivial

43. Error: V-STARS analysis zV-STARS calculates the rms error in all 3 dimensions Unknown object TARGET location Camera 1Camera 3Camera 2 region of uncertainty

44. Error: V-STARS analysis z12-ray intersection is typical, resulting in an ellipsoid of uncertainty. zThe rms errors reported by V-STARS are the semimajor axes of the ellipsoid Unknown object TARGET location Camera 1Camera 3Camera 2

45. Error: V-STARS analysis Xrms, Yrms, Zrms ~5um

46. Improvements made Increased information in central regions Increased stability of system yProjector yCamera (tripod, remote shutter) yPressurization system

47. Old slide pattern

48. Location of projected targets (old slide)

49. New slide pattern

50. Location of projected targets (New slide)

51. Improvements made Increased information in central regions Increased stability of system yProjector yCamera (tripod, remote shutter) yPressurization system

52. Initial projector mount Learned that the projector support should be in the focal plane of the projector

53. Improved projector mount

55. Improvements made Increased information in central regions Increased stability of system yProjector yCamera (tripod, remote shutter) yPressurization system

56. Tripod, remote shutter

57. Improvements made Increased information in central regions Increased stability of system yProjector yCamera (tripod, remote shutter) yPressurization system

58. Pressurization system

59. Pressurization (0-50psi)

60. Pressurization (50-100psi)

61. Pressurization (100psi-burst)

62. Equipment protection

66. New plan zPlan to measure window thickness using photogrammetry (currently use CMM) zProcedure: perform photogrammetric measurements on both sides of the window.

67. Newest discovery

68. Periodic variation in deflection as f(azimuth) may be an indication of harmonic variations in the circumferential direction.