Calibration of the Nikon D200 for Close-Range Photogrammetry

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Calibration of the Nikon D200 for Close-Range
Photogrammetry
Lassana Sheriff Office of Science, Science
Undergraduate Laboratory Internship Program City
College of New York, New York NY SLAC National
Accelerator Laboratory, Menlo Park,
California August 13, 2009
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Outline

• (AEG) and Metrology Department
• Camera (Nikon D200)
• Software and Targets
• Camera Model
• Central Perspective Projection
• Brown Extension Model
• 2D Calibration Wall
• 3D Calibration Structure
• Results
• Conclusion and Future

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Alignment Engineering Group (AEG) and Metrology
Department

• Measuring and Aligning objects with survey
  instruments (Laser Tracker)
• For instance Magnets and other components in
  LCLS from the electron gun to the dump
• The project is to evaluate the possibility to use
  photogrametry as another survey technique
• Photogrametry Photographic Metrology

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Camera

• Nikon D200 and built-in flash.
• DX format 23.7mm x 15.7mm
• 10.2 megapixels(6 micron square pixels)
• Nikkor 20mm lens

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Software and Targets
Australis Coded Targets (Retro-reflective) 60
degree lose reflective property. Scale Bar
(Distance between the targets on the bar is
known) can use to scale measurement
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Reflective Targets

• Coded
• Spherical targets
• Rotatable targets

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y
Image point
m
Y
x
p
r
yp
o
xp
X
c
i
Projection plane
Z
C
i
Perspective center
Z
Y
M
Object point
X
O
Object co-ordinate system
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Camera Parameters

• Interior Orientation of the Camera
• Focal length and the principal points of the
  camera c, xp, and yp
• Extended by Brown Model
• k1,k2,k3 (radial distortion)
• p1, p2 (decentering)
• b1, b2 (shearing)
• Compare, analyze and assess the cameras stability

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Interior Orientation
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Central Perspective Projection

• This equation illustrates an ideal basic
  photogrammetry model

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2D wall

• One partial wall in AEG Laboratory
• Coded Targets
• 13 points measured with a laser tracker
• Different Angles

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Flat Wall without Processing

• No Australis

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Australis window for the wall
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3D

• 3D Structure
• Coded Targets
• Reflective Sphere
• Same Angles as 2D
• Started late

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3D without Processing

• No Australis

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Graphs

• Line Graphs (trends)
• Histogram (distribution)
• 41 data sets 2D wall
• 6/29-8/7
• 23 data sets 3D structure
• 7/15-8/7

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Line Graph c
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Line Graph xp
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Line Graph yp
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Histogram c
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Histogram xp
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Histogram yp
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Results

• Line Graphs and their purpose (No trend as data
  is scattered and good stability within the day)
• Example Focal length, some points are far off
  the trend likely due to transportation and
  handling purposes
• Histogram (distribution of the parameters)
• Normal Distribution
• (xp and yp) alike and are not normally
  distributed
• Focal length more like a normal distribution.

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Conclusion and Future

• Camera can be used for Photogrammetry
  measurements but calibrate before each use.
• Mechanical improvement to the camera
• 3D structure from more angles to get true 360
  degree.

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Acknowledgement

• The Science Undergraduate Laboratory Internship
  SULI program wouldn't have been possible without
  the funding of the Department of Energy DOE here
  at Stanford Linear Accelerator Center SLAC.
  Special acknowledgment goes to my mentor BRIAN
  FUSS for his diligent guidance and support. I
  would like to acknowledge CATHERINE LECOCQ for
  her resilient work and direction in the entire
  project. And finally acknowledgement to BRENDAN
  DIX for his participation in building the 3D
  structure and to the rest of the members of
  Alignment Engineering Group for their support.
• and thanks to Stephen and all the students!!

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