Page 471 - The Mechatronics Handbook

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FIGURE 19.66 The LRF-200 series rangefinder (courtesy Schwartz Electro Optics, Inc.).

FIGURE 19.67 The Class 1 (eye-safe) LD90-3 series TOF laser rangefinder is a self-contained unit available in
several versions with maximum ranges of 150–500 m under average atmospheric conditions (courtesy RIEGL USA).

to the round-trip time-of-flight (Gustavson & Davis, 1992). An analog-to-digital conversion is performed
on the sampled capacitor voltage; at the precise instant a return signal is detected, whereupon the resulting
digital representation is converted to range and time-walk corrected using a look-up table.
The LRF-X series rangefinder shown in Fig. 19.66 features a compact size, high-speed processing, and
an ability to acquire range information from most surfaces (i.e., minimum 10% Lambertian reflectivity)
out to a maximum of 100 m. The basic system uses a pulsed InGaAs laser diode in conjunction with an
avalanche photodiode detector and is available with both analog and digital (RS-232) outputs.
RIEGL Laser Measurement Systems, Horn, Austria, offers a number of commercial products (i.e., laser
binoculars, surveying systems, “speed guns,” level sensors, profile measurement systems, and tracking
laser scanners) employing short-pulse TOF laser ranging. Typical applications include lidar altimeters,
vehicle speed measurement for law enforcement, collision avoidance for cranes and vehicles, and level
sensing in silos.
The RIEGL LD90-3 series laser rangefinder (Fig. 19.67) employs a near-infrared laser diode source and
a photodiode detector to perform TOF ranging out to 500 m with diffuse surfaces, and to over 1000 m
in the case of cooperative targets. Round-trip propagation time is precisely measured by a quartz-stabilized
clock and converted to measured distance by an internal microprocessor, using one of two available
algorithms. The clutter suppression algorithm incorporates a combination of range measurement aver-
aging and noise rejection techniques to filter out backscatter from airborne particulates, and is, therefore,
useful when operating under conditions of poor visibility (Riegel, 1994). The standard measurement
algorithm, on the other hand, provides rapid range measurements without regard for noise suppression,
and can subsequently deliver a higher update rate under more favorable environmental conditions.

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