Note: The first entry must be smaller than the second – the system only scans in a
counterclockwise direction. If the first number is larger than the second, the
program automatically makes the second number larger.
Note: Make sure that the cables to the DeltaSphere (DeltaSphere power,
Ethernet, 1394 and Camera power) have enough slack for the system to
rotate.
It is often desirable to scan a limited horizontal range to cover an object like a car or body. The
easiest way to aim the DeltaSphere in this case is to use the Pan controls described in Section
4.3.2.
Vertical Field of View
The Vertical Field of View specifies the range of elevation to be scanned. The vertical rotation
mirror always rotates 360º and always in the same direction. The Vertical FOV determines
which points are recorded and which are discarded.
0º in the vertical direction is defined to be a horizontal line from the center of the rotating mirror
– again perpendicular to, and coming from, the front face of the DeltaSphere-3000. Positive
values are measured up from that horizontal line; negative values are measured down. For
example, a Vertical FOV from 0º to 90º would scan from the horizontal to the vertical overhead.
The negative limit of the Vertical FOV is approximately -55º. Below that angle the laser
intersects the DeltaSphere’s case. The upper limit is 90º (straight overhead) – but with the
optional camera mounted the limit is approximately 75º. The Vertical FOV will accept values
from -55º to 90º.
To scan a complete panorama with the DeltaSphere, typical Vertical FOV values would be -55º
to 90º (or 75º). To eliminate an upward view, one might set the Vertical FOV from -55º to 45º
(or whatever elevation is appropriate).
Scanning Density
The scanning density (labeled
Samples/Deg
) specifies how many points per degree will be
acquired. The highest-density scan is 20 samples/degree for the red laser and 15 for the IR laser.
The lowest-density scan is 5 samples/degree. Note that this setting specifies the scan density for
both azimuth and elevation – though the actual number of samples in the elevation range will
vary slightly. Preset values are 5, 6.66, 10, 13.33, 15 and 20 samples per degree.
The default value is 13.33 samples/degree – which produces 4800 samples in a single 360º
circle. For this setting, if the horizontal field of view is 360º and the vertical field of view is -55
to 90 (the maximum), the DeltaSphere will acquire approximately 4800 by 1900 samples (9.1
million). Higher density values will result in greater detail, longer scan times and larger scan
files.
DeltaSphere-3000 3D Scene Digitizer
27
9/23/05
