Sensors and Methods for Mobile Robot Positioning

Chapter 4: Sensors for Map-Based Positioning 103
SEO Scanning Helicopter Interference Envelope Laser Detector (SHIELD)
This system was developed for the U.S. Army [SEO, 1995b] as an onboard pilot alert to the presence
of surrounding obstructions in a 60-meter radius hemispherical envelope below the helicopter. A
high-pulse-repetition-rate GaAs eye-safe diode emitter shares a common aperture with a sensitive
avalanche photodiode detector. The transmit and return beams are reflected from a motor-driven
prism rotating at 18 rps (see Figure 4.9). Range measurements are correlated with the azimuth angle
using an optical encoder. Detected obstacles are displayed on a 5.5-inch color monitor. Table 4.5
lists the key specifications of the SHIELD.
Table 4.5: Selected specifications for the Scanning
Helicopter Interference Envelope Laser Detector
(SHIELD). (Courtesy of Schwartz Electro-Optics, Inc.)
Parameter Value Units
Maximum range
(hemispherical envelope)
>60
>200
Accuracy