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Complete Rangefinder System

The complete system consists of the line-scanning laser rangefinder with the high-speed interface card, the pan-tilt unit, a Dell PC with a 200 MHz Pentium Pro. In addition to the 2 special ports on the high-speed interface card, the rangefinder also requires a serial port, as does the pan-tilt unit. A power supply (12V) is also required to power the scanning mirror motor.


  
Figure 6: The movable cart containing the necessary hardware to acquire range data (including power). The rangefinder and panning motor are in the upper right, there is a computer display and B/W monitor (for showing the laser position) in the center, underneath is a Dell PC, and at the bottom is a deep-cycle marine battery and power inverter.
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All of these components have been mounted on a cart, shown in figure 6. The PC has been outfitted with a flat LCD display for two reasons: the first is size, we want to minimize the appearance of the system in the rangefinder's field-of-view; the second is power consumption, since we often rely on battery power.

To allow the operator to ``see'' the laser, we have placed an infrared-sensitive video camera with a wide-angle lens and a small video monitor on the cart. And to be mobile, we have added a deep-cycle marine battery (12V) with an inverter to get 120 VAC to eliminate external power needs. The system can run for several hours on a single charge.


  
Figure 7: The Canon EOS D2000 with mounting bracket to position the center-of-projection of the lens at the same location as the center-of-projection of the rangefinder. Since the light-sensor in this camera is smaller than film, it is necessary to use an extremely wide-angle lens for image collection. Here we show the 14mm lens, which acquires an image similar to a 24mm lens on 35mm film.
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To complete the system, we have built a bracket to hold our digital camera with its center-of-projection aligned with the center-of-projection of the panning, scanning rangefinder (see figure 7). After an environment is scanned, the laser is removed from the panning unit and replaced with the camera, whereupon we take 12 images of the environment.


next up previous
Next: Errors and Compensation Up: Range Acquisition Hardware Previous: Pan-Tilt Unit
Lars S. Nyland
1999-02-19