2001 VIDERE DESIGN |
Figure 4-1 Range resolution in mm as a function of distance, for
several different lens focal lengths.
4.6Range Resolution
Range resolution is the minimum distance the stereo system can distinguish. Since stereo is a triangulation operation, the range resolution gets worse with increasing distance from the stereo head. The relationship is:
∆r = r 2 ∆d , bf
where b is the baseline between the imagers, f is the focal length of the lens, and ∆d is the smallest disparity the stereo system can detect. For the STH- DCAM, b is 90 mm, and ∆d is 0.35 um (pixel size of 5.6 um, divided by the interpolation factor of 16).
Figure 4-1 plots this relationship for several focal lengths. At any distance, the range resolution is inversely proportional to the focal length.
4.7Field of View
The field of view is completely determined by the focal length, given a fixed imager. The formulas for the FOV in horizontal and vertical directions are:
HFOV = 2 arctan(1.792 / f )
VFOV = 2 arctan(1.344 / f )
where f is in millimeters. For example, a 4.0 mm lens yields a horizontal FOV of 48 degrees. The following table shows the FOV for some standard focal lengths.
Lens focal length | Horizontal FOV | Vertical FOV |
2.1 mm | 81 deg | 65 deg |
4.0 | 48 | 37 |
8.0 | 25 | 19 |
Table
different lens focal lengths.
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