Scarica (PDF – 6.19 MB)

Light from a scene passes through this single point and projects an
inverted image on the opposite side of the box. Cameras using small
apertures and the human eye in bright light both act like a pinhole
camera [40].
The pinhole camera model is based on the principle of collinearity,
where each point in the object space is projected by a straight line
through the projection center into the image plane. Figure 5 shows the
geometric model of a pinhole camera. The camera coordinate system
Q
Y
R
1
Image plane
Y
2
O
X
x 1
Figure 5: Geometric model of the pinhole camera. [40]
(O, X1, X2, X3) has its origin at the camera aperture (which is consid-
ered infinitely small, coincident with a point). Axis X3 is pointing in
the viewing direction of the camera and is referred to as the optical
axis. The plane which intersects with axes X1 and X2 is the front side
of the camera, or principal plane.
1
The image plane is where the 3D world is projected through the
aperture of the camera. It is parallel to axes X1 and X2 and is located
at distance f from the origin O in the negative direction of the optical
axis. f is also referred to as the focal length of the pinhole camera.
11
x 2
f
X
2
x 3
X
P