3D time-of-flight MEMS-scanning camera from Fraunhofer improves robot vision

IMAGE: The optical scan head of a 3D ToF camera is shown with the Fraunhofer IPMS integrated MEMS scanning mirror array. (Image credit: Fraunhofer IPMS)

Dresden, Germany--The Fraunhofer Institute for Photonic Microsystems (IPMS) has designed and built a microelectromechanical systems (MEMS) scan technology as a key hardware component for a time-of-flight camera that is part of the European TACO project. For three-and-a-half years, five research institutions and two industrial companies have been working within the scope of the European joint research project TACO (Three-dimensional Adaptive Camera with Object detection and foveation) to develop a new kind of three-dimensional (3D) camera system that should allow robots to perform more demanding tasks.

The Fraunhofer camera allows objects in the surroundings to be detected with a higher resolution--similar to human vision--without having to increase the volume of data. At the 2014 SPIE Photonics West conference in San Francisco, Fraunhofer IPMS will be presenting the complete camera system for the first time as a fully functional prototype.

Differentiate between colors and brightnesses, judge distances, identify objects and movements in our surroundings in 3D and in a matter of seconds: things that are easy for humans thanks to our eyes and brain pose a big problem for machines. Because robots lack either spatial information that is resolved in real-time or the necessary focus for artificial, 3D vision, or because too much image information is recorded to be processed quickly enough to be translated into actions, it has only been possible to develop relatively rudimentary robots up to now that are only able to perform services such as cleaning, building, servicing, security or personal care tasks. But things don't have to stay that way, believe researchers at Fraunhofer IPMS.

The scientists have developed an extremely compact scanning technology for time-of-flight (ToF) telemetry systems based on production methods from microsystems technology that allows 3D image acquisition with a flexible scanning rate and thus scanning with an adapted resolution. 3D camera systems equipped with this LinScan technology could enable future generations of robots to roughly search their surroundings for objects that appear in their visual field and to only resolve the objects they are looking for at a higher accuracy. The robot would work with a relatively small volume of data and would still be able to gain a better understanding of its surroundings so as to better interact with everyday objects and our environment.

A precondition for the realization of this so-called principle of foveation is, however, that the robot knows what it is looking for and that it is also able to identify and interpret the objects being sought in a matter of seconds. Apart from the hardware (eye) it also needs corresponding image analysis software algorithms (brain). What's more, the robot should also be equipped with image sensors and software for 3D vision to gain a spatial idea of its surroundings and thus be able to navigate to objects precisely.

The heart of the camera system is an optical scanner with five synchronously operated LinScan mirrors from Fraunhofer IPMS. The MEMS scanner array guarantees the necessary receiving aperture for the ToF system of effectively 5 mm and was designed for an adaptive 3D camera system with an optical scanning range of at least 40° x 60°, 1 MVoxel/s measuring rate of the TOF telemetry system with a 3 mm measuring uncertainty at a measuring distance of 7.5 m. The quasi-static drive of the microscanner allows a line-by-line image formation with a variable refresh rate of < 1-100 Hz, whereby the vertical measuring point density in the relevant image section can be locally increased by reducing the scanning rate. The horizontal image acquisition by means of the gimbal-mounted 1.6 kHz resonant micromirror guarantees a larger receiving aperture compared to a 2D-quasi-static drive and thus a higher resolution of TOF telemetry with a simultaneous larger optical scanning angle of up to 80°.

The TACO project was recently concluded with the development of a fully functional complete system that will be presented to the public for the first time at Photonics West booth number 4407. MEMS scan technologies from the Fraunhofer IPMS are also the subject of a paper at the parallel symposium 8977. TACO is a research project co-financed by the European Union within the scope of the 7th general program. The project was launched in the first quarter of 2010 under the leadership of Technikon Forschungsgesellschaft GmbH with a term of 36 months.

SOURCE: Fraunhofer IPMS; http://www.ipms.fraunhofer.de/en/press-media/press/2014/2014-01-20.html