Current Research: Ultrasonic 3D Range Sensor on a Chip

Optical 3D imagers for gesture recognition, such as Microsoft Kinect, suffer from large size and high power consumption. Their performance depends on ambient illumination and they generally cannot operate in sunlight. These factors have prevented widespread adoption of gesture interfaces in energy- and volume-limited environments such as tablets and smartphones. Gesture recognition using sound is an attractive candidate to overcome these difficulties because of the potential for chip-scale solution size, low power consumption, and ambient light insensitivity. Our research focuses on building a 2D ultrasonic depth sensor system using batch-fabricated micromachined aluminum nitride (AlN) ultrasonic transducer arrays and custom CMOS electronics. We have made significant progress towards this goal by demonstrating a 2D rangefinder which measures distance and angle to objects up to 750mm away.

Earlier Research: Ultrasonic Rangefinder

In this project, we built an ultrasonic rangefinder which has a working range of 30mm to 450mm and operates at a 375 Hz maximum sampling rate. The range measurement principle is based on pulse-echo time of flight measurement using a single transducer for transmit and receive consisting of a piezoelectric AlN membrane which was fabricated using a low-temperature process compatible with processed CMOS wafers. The performance of the rangefinder exceeds the performance of other micromechanical rangefinder systems.

Ultrasonic Distance Measurement

In this project, we built an ultrasonic distance sensor which measures the distance between two sensor nodes up to 1.3m apart. Ultrasonic distance sensors based on piezoceramic transducers have >1m range and millimeter accuracy but require the use of bulky transducers. Existing micromachined sensors deliver inferior performance, with maximum range in the tens of centimeters. We present theory, design equations, and measured results for a micromechanical ultrasonic distance sensor which approaches the performance of piezoceramic-based solutions. The sensor has a maximum range >1300mm and random errors (3σ) of <1.7mm at 1.3m.