SF45/B scanning laser rangefinder

The Lightware SF45/B is a scanning laser rangefinder, a compact LiDAR sensor from Lightware LiDAR that measures distance to objects around a small unmanned aircraft. A single 905 nm laser beam is swept horizontally by an oscillating mechanism, so one sensor covers a wide arc instead of a single line of sight.

The main figures are a measurement range of up to 50 m, an adjustable scanning angle of up to 320 degrees, and up to 5000 point measurements per second. The range figure applies to a white wall in daylight, so darker or smaller targets return shorter distances. Because the scan angle can be narrowed, an integrator can trade coverage against how often each direction is measured. The sensor can report the first and the last pulse return, which helps when a beam partly crosses foliage, wires or other thin obstacles. The laser is listed as eye safe, Class 1M.

The housing measures 51 x 48 x 44 mm. Lightware lists a weight of 59 g, which suits small multirotors and fixed-wing aircraft where payload mass counts. The supply is 5 V with a typical current draw of 300 mA, according to the PX4 documentation, so the sensor can run from an avionics rail; a long supply cable can drop the voltage at the sensor, and a separate step-down converter from battery voltage keeps 5 V where needed.

Connection is by USB, 3.3 V serial (UART) or I2C. On a flight controller running PX4 the sensor connects to a free serial port such as TELEM2, at a baud rate of 921600 set with the Lightware Studio configuration software. The PX4 driver is not in the default build and is enabled in the build configuration, after which the sensor publishes OBSTACLE_DISTANCE messages for obstacle avoidance and collision prevention.

Typical applications are obstacle detection and avoidance, wide-area proximity sensing and altitude or terrain measurement on UAVs, and mapping of the space around a vehicle in confined sites such as buildings, tunnels or stockpiles.