Tamron Telephoto Lens Calibration Slide Lens Specifications Tamron
Tamron Telephoto Lens Calibration Slide
Lens Specifications • Tamron SP AF 28 -300 mm – – Ashperical Lens Elements 13 groups and 15 elements Angle of view 75 -8 deg. Focal length 28 -300 mm (11 X) – Distortion • Some barrel distortion at 28 mm • Very slight pin-cushion distortion at 300 mm • Good performance for a wider range zoom lens • http: //www. photo. net/equipment/tamron/28_300_Di/page 3. html 300 mm/5 m 9/30/2020 Slide 2/29
Nikon D 70 CCD Specifications • Modified version of the Sony ICX 413 AQ • Size: 0. 93 x 0. 61” (23. 7 x 15. 6 mm) • Pixel size: 7. 8 microns Source: Thomas Hogan’s Complete Guide to the Nikon D 70 • 8 to 10 images captured for each focal length settings – 28 mm, 100 mm, 200 mm, and 300 mm • At each focal length the focus was fixed to best capture the whole calibration pattern. 9/30/2020 Slide 3/29
Model Complexity Selection 28 mm Criterions AIC MDL BIC SSD CAIC Radial 5 5 4 Tangential 4 4 2 Criterions AIC MDL BIC SSD CAIC Radial 4 3 2 3 3 Tangential 4 3 3 Criterions AIC MDL BIC SSD CAIC Radial 3 3 2 Tangential 3 3 0 0 0 Criterions AIC MDL BIC SSD CAIC Radial 4 4 2 Tangential 4 4 0 100 mm 200 mm 300 mm 9/30/2020 Slide 4/29
Calibration Error for Tamron 28 -300 mm Lens Effective Focal Length (mm) 28 100 MSE 0. 1664 0. 1991 200 300 0. 3631 Pixel Error [x-dir. , y-dir. ] [0. 24, 0. 27] Pixel Error (Open. CV) [x-dir. , y-dir. ] [0. 31, 0. 37] [0. 35, 0. 22] [0. 60, 0. 31] [0. 0, 0. 0] [0. 47, 0. 31] [2. 00, 0. 39] Calibration Error for Other Lenses Effective Focal Length (mm) MSE Wide Angle 0. 9520 Full Frame Fisheye 0. 6639 Fisheye 0. 9405 • Reprojection error of calibration points is relatively small and less then the error obtained with wide angle and fisheye lenses. • Pixel error in both x an y direction are better than using Open. CV method 9/30/2020 Slide 5/29
Calibration Results • Principal point estimation Reason for the shift in the principal point is the misalignment of the optical components found in the lens. The position and orientation of the lens components are changed by adjusting the focus and zoom. (1 -28 mm, 2 -100 mm, 3 -200 mm, 4 -300 mm) 9/30/2020 Slide 6/29
Calibration Results • Principal point estimation using Open. CV calibration method (1 -28 mm, 2 -100 mm, 3 -200 mm, 4 -300 mm) 9/30/2020 Slide 7/29
Calibration Results • Center of distortion estimation with Hartley/Kang method using epipolar geometry constraints (1 -28 mm, 2 -100 mm, 3 -200 mm, 4 -300 mm) 9/30/2020 Slide 8/29
Focal Length Estimation Results Using IRIS Implementation Effective Focal Length 28 mm 100 mm 200 mm 300 mm Measured Focal Length 31 89 81 234 * % Error 12% 11% 60% 22% Results Using Open. CV * Focal length % error is placed only for reference. Focal length measured by the camera calibration may be different from focal length specified by the manufacturer. 9/30/2020 Slide 9/29 Effective Focal Length 28 mm 100 mm 200 mm 300 mm Measured Focal Length 28 89 82 231 * % Error 7% 11% 59% 23%
Results with Varied Focus (focus setting: 1 -2. 5 m, 2 -4 m, 3 -5 m) 9/30/2020 Slide 10/29
Zoom Lens Calibration • If we look only at the reprojection error then the performance of the calibration method is very good • If we consider the actual extraction of camera parameters, the estimated parameters are more erroneous at larger focal length settings • It is difficult to determine at what focal length setting calibration fails due to coupling of different lens settings • Future work will be to find reasons for the error in the parameter estimation and comparing the performance of other methods on the obtained data set. 9/30/2020 Slide 11/29
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