Calibration of the Nikon D200 for Close-Range Photogrammetry Lassana Sheriff Office of Science,...

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 NYSLAC National Accelerator Laboratory, Menlo Park, California

August 13, 2009

August 13, 2009 Lassana Sheriff SULI 2009 2

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


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


Camera

• Nikon D200 and built-in flash.

• DX format 23.7mm x 15.7mm

• 10.2 megapixels(6 micron square pixels)

• Nikkor 20mm lens


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


Reflective Targets

• Coded

• Spherical targets

• Rotatable targets


Projection plane

y

p rx

Object point

M

X

Y

C

c i

iPerspective center

MMM ZYX ,,

Image point

Z

o

m

xp

yp

X

Y

Z

Object co-ordinate systemO


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 camera’s stability


Interior Orientation


Central Perspective Projection

• This equation illustrates an ideal basic photogrammetry model

dxZZrYYrXXr

ZZrYYrXXrcxx

CMCMCM

CMCMCMpM

)()()(

)()()(

333231

131211

dyZZrYYrXXr

ZZrYYrXXrcyy

CMCMCM

CMCMCMpM

)()()(

)()()(

333231

232221


2D wall

• One partial wall in AEG Laboratory

• Coded Targets

• 13 points measured with a laser tracker

• Different Angles


Flat Wall without Processing

• No Australis


Australis window for the wall


3D

• 3D Structure

• Coded Targets

• Reflective Sphere

• Same Angles as 2D

• Started late


3D without Processing

• No Australis


Graphs

• Line Graphs (trends)

• Histogram (distribution)

• 41 data sets 2D wall

• 6/29-8/7

• 23 data sets 3D structure

• 7/15-8/7


Line Graph c


Line Graph xp


Line Graph yp


Histogram c


Histogram xp


Histogram yp


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.


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.


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!!

Calibration of the Nikon D200 for Close-Range Photogrammetry Lassana Sheriff Office of Science,...

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