Sandeep sasidharan

1. Presented by:
Sandeep Sasidharan
IIT Kanpur

2.  Purpose of camera calibration
 Calibration distortion models
 Methods of calibration

3.  Determine the IOP of camera
 Focal length (f)
 The principal point co-ordinates (x0,y0)
 Image distortion parameters

4.  For carrying out photogrammetry
 Camera lens must provide perfect central projection
 Camera focal plane is perfectly flat
OR
 Camera lens perspective centre, the ground point
and the corresponding point on the image lies in a
straight line

5.  Radial lens distortion (RD)
 Decentric lens distortion (DLD)
 Atmospheric refraction distortion (ARD)
 Affine deformation distortion (ADD)

6.  Laboratory methods
 Field methods
 Stellar methods

7. Wolf, P.R.,(Elements of
photogrammetry)

8. Wolf, P.R.,(Elements of photogrammetry)

9.  Equivalent focal length
 FL at distortion free central area of lens
 EFL= (gf+ gh+ gs+ gt)/ 4 tan θ
 Radial lens distortion of each angle θ
 RD=EFL x tan n θ ( theoretically for angle n)
 Directly measured and averaged ( practical value)
 Difference of both gives RD for each angle

10.  Calibrated focal length
 FL which produces mean distribution of RD
 CFL is selected so that Max +ve RD = Max –ve RD
(D1-CFL tan θ1 + D2-CFL tan θ2 )=0
 Principal point location

11.  Target points are near to the centre and sparse
in outer areas and radial distortion is
predominant at outer areas
 Method is very expensive
 Measurements must be very accurate

12.  Self calibration
 Calibration using 2D/3D calibration objects
 Bundle Adjustment Method

13.  Development of new algorithms for IOP
determination
 Helped using less expensive digital cameras for
conventional photogrammetry