In general, ultrasonic sensors are sensors that make use of the characteristics of high-frequency sound for a range of applications such as distance measurement, non-destructive testing of materials, or medical applications.

For distance measurement, a typical ultrasonic sensor uses a transducer to periodically send out ultrasonic pulses in the air. These pulses get reflected from objects in the detection area of the sensor and are received back by the sensor. By measuring the time it takes an ultrasonic pulse to travel to the object and get reflected back to the sensor, the distance to the object can be calculated. This principle is called time-of-flight measurement.

In addition to measuring the distance to an object, Advanced Ultrasonic Sensors can also calculate the horizontal and vertical position of an object relative to the sensor itself (i.e. they provide 3D coordinates for detected objects). The localization of objects in three-dimensional space also allows an advanced ultrasonic sensor to detect multiple objects in a single scan. In that sense, the principle behind our 3D ultrasonic is similar to echolocation, as applied for example by bats. In comparison, a typical ultrasonic sensor, as described in the previous section, will normally only give the distance to the nearest object. Because of this, a limited opening angle is usually applied for this type of sensor. In contrast, our sensors systems allow for opening angles of up to 160°.

The surface size of an object plays a pivotal role in reflecting the ultrasonic wave that is sent out by the transducer. An object, for which only a small surface faces the sensor, has a lower chance of detection.

The orientation of an object determines which part of the ultrasonic pulse gets reflected to the sensor. At an adverse angle (= surface not perpendicular to sensor), a smaller proportion of the pulse is received by the sensor, in which case the object has a lower chance of detection.

Ultrasonic pulses are attenuated in air, which limits the detection range that can be achieved by Advanced Ultrasonic Sensors. The further away an object is from the sensor, the lower its chance of detection becomes.

Material characteristics of an object also determine which part of the ultrasonic pulse gets reflected to the sensor. For weakly reflecting or sound absorbing materials, such as foam, the chance of detection decreases.

At the beginning of each measurement cycle, a transducer on the sensor sends out an ultrasonic pulse. This pulse is reflected by surrounding objects and received by an array of microphones on the sensor. Based on the different times of when echoes arrive at the individual microphones, the origins of the echoes are calculated as 3D coordinates. These 3D coordinates are put out at the end of each measurement cycle.