Presenter

Mr Dave Geerardyn - ETRO, Vrije Universiteit Brussel [Email]

Abstract

Introduction: Since the launch of the Kinect®, depth sensing cameras became known to the general public. Currently these type of systems mostly use structured light and time-of-flight measurement techniques to achieve the 3D images.
Both the structured light and time-of-flight measurement techniques have been showing a good performance in various applications, like gaming, distance measurements and as a human-machine interface. However, they give incorrect measurements when a semi-transparent or partially-reflective surface is placed in-between the scene and the camera. As a consequence, they cannot be used in for example swimming pools because the water surface would disturb the measurements. Therefore, we developed a modified time-of-flight measurement algorithm which enables the formation of 3D images behind a partially reflective surface and demonstrate its application as a drowning-people detection system in swimming pools.
Research objectives: Develop a time-of-flight sensing system which enables accurate measurements in a setup with multiple reflections, such that distances of objects behind primary confusing reflections can be measured. This incorporates the investigation and creation of a new type of measurement setup based on an FPGA with a time-of-flight sensor, designing a near-infrared light source capable of modulating laser light at high power (800 mW) and high frequencies (1 GHz), and executing distance measurements of objects behind semi-transparent and partially reflecting surfaces.
Research results: For the first time to our knowledge, we demonstrated the use of time-of-flight image sensors towards a drowning-people detection system for swimming pools. We first developed an algorithm which allows the use of the pulsed time-of-flight technique in combination with a continuous-wave time-of-flight sensor. Next, we created a new light source, enabling very high-speed modulation of laser light. Using the modified time-of-flight technique and the newly developed light source, we successfully created a proof-of-concept demonstrator illustrating the operation of our pulsed time-of-flight technique for the measurement of object distances behind a primary confusing reflecting surface. We were able to measure distances of objects behind primary confusing reflections, coming from either a water surface or a semi-transparent and partially reflecting sheet.

Short CV

Civil engineer, Photonics, University of Ghent , 2009