Author: Hughes
Year: 2010
- Radial barrel distortion noticeable on fish eye lenses => resolution decrease on peripherical areas of the image
- odd-order polynomial models cannot sufficiently compensate for radial distortion => alternative models studied here
- assumption : lens displacement curve (?) is linear near the foveal and is monotically increasing
- Displacement curve = describes the radial dusplacement of points from pinhole to fisheye plane given any radial value
- pinhole model preserves straightlines
$r_u = f tan(\theta) $
projection models:
- equidistant $ r_d = f \theta $
- equisolid: length of the chord on the unit sphere $ r_d = 2f sin(\frac{\theta}{2} )$
- orthographic $ r_d = f sin(\theta) $ but suffer from strong distortion
- stereographic $ r_d = 2f tan(\frac{\theta}{2})$ the center of reprojection is the oposite of the tangential point
- PFET (polynomial Fisheye transform) $ r_d = P(r_u)$ 5th order is good
- FET (fish eye transform)
$r_d = s ln(1+\lambda r_u)$ - FOV model
$r_d = \frac{1}{\omega} arctan \left ( 2 r_u tan (\frac{\omega}{2})\right )$ with$\omega$ the FOV of the camera - radial distortion can model deviation from real model
$\Delta r_d = P(r_u)$
Results:
- Most of fish eye lenses are supposed to fit with equidistant or equisolid projection model
- Init f = 2 / FOV and 0 for the radial distortion parameters
Commentaire:
Décrit précisément les modèles de lentille, top! Pas hyper bien compris la technique de calibration