Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


With light echoes, the invisible becomes visible


Scientists at the University of Bonn and the University of British Columbia (Vancouver, Canada) have developed a novel camera system which can see around the corner without using a mirror. Using diffusely reflected light, it reconstructs the shape of objects outside of the field of view.

The researchers will be reporting their results at the international Conference for Computer Vision and Pattern Recognition (CVPR) from June 24-27 in Columbus (Ohio, USA).

Prof. Dr.-Ing. Matthias Hullin from the Institute of Computer Science II at the University of Bonn.

Photo: Hullin

A laser shines on the wall; a camera watches the scene. Nothing more than white ingrain wallpaper with a bright spot of light can be seen through the lens. A computer records these initially unremarkable images and as the data is processed further, little by little, the outlines of an object appear on a screen.

Yet, this object is behind a partition and the camera cannot possibly have seen it – we have apparently looked around the corner. A magic trick? "No," says Prof. Dr.-Ing. Matthias B. Hullin from the Institute of Computer Science II at the University of Bonn. "This is an actual reconstruction from diffusely scattered light. Our camera, combined with a mathematical procedure, enables us to virtually transform this wall into a mirror."

Scattered light is used as a source of information

The laser dot on the wall is by itself a source of scattered light, which serves as the crucial source of information. Some of this light, in a roundabout way, falls back onto the wall and finally into the camera. "We are recording a kind of light echo, that is, time-resolved data, from which we can reconstruct the object," explains the Bonn computer scientist. "Part of the light has also come into contact with the unknown object and it thus brings valuable information with it about its shape and appearance."

To be able to measure such echoes, a special camera system is required which Prof. Hullin has developed together with his colleagues at the University of British Columbia (Vancouver, Canada) and further refined after his return to Bonn. In contrast to conventional cameras, it records not just the direction from which the light is coming but also how long it took the light to get from the source to the camera.

The technical complexity for this is comparatively low – suitable image sensors came onto the mass market long ago. They are mainly found in depth image cameras as they are used, for instance, as video game controllers or for range measurements in the automotive field. The actual challenge is to elicit the desired information from such time-of-flight measurements. Hullin compares the situation to a room which reverberates so greatly that one can no longer have a conversation with one's partner. "In principle, we are measuring nothing other than the sum of numerous light reflections which reached the camera through many different paths and which are superimposed on each other on the image sensor."

This problem, known as multipath interference, has been giving engineers headaches for a long time. Traditionally, one would attempt to remove the undesired multipath scatter and only use the direct portion of the signal. Based on an advanced mathematical model, Hullin and his colleagues, however, developed a method which can obtain the desired information exclusively from what would usually be considered noise rather than signal. Since multipath light also originates from objects which are not at all in the field of view, the researchers can thus make visible what is virtually invisible.

Minimal technical complexity and intelligent programming

"The accuracy of our method has its limits, of course," says Prof. Hullin – the results are still limited to rough outlines. However, the researchers assume that based on the rapid development of technical components and mathematical models, an even higher resolution can be achieved soon. Together with his colleagues, he will present the method at the international Conference for Computer Vision and Pattern Recognition (CVPR) from June 24 to 27 in Columbus (Ohio, USA). The new technology is received with great interest – Hullin hopes that similar approaches can be used, for example, in telecommunications, remote sensing and medical imaging.

Publication: Felix Heide, Lei Xiao, Wolfgang Heidrich und Matthias B. Hullin, "Diffuse Mirrors: 3D Reconstruction from Diffuse Indirect Illumination Using Inexpensive Time-of-Flight Sensors“.

Contact information:

Prof. Dr.-Ing. Matthias B. Hullin
Institute of Computer Science II
University of Bonn
Tel. 0228/7354169

Weitere Informationen: Publication Podcast

Johannes Seiler | idw - Informationsdienst Wissenschaft

More articles from Innovative Products:

nachricht New Video Camera Released Featuring Ultra-High-Speed CMOS Image Sensor Developed At Tohoku University
11.08.2015 | Tohoku University

nachricht Safe motorcycle helmets – made of carrot fibers?
06.08.2015 | Empa - Eidgenössische Materialprüfungs- und Forschungsanstalt

All articles from Innovative Products >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Kick-off for a new era of precision astronomy

The MICADO camera, a first light instrument for the European Extremely Large Telescope (E-ELT), has entered a new phase in the project: by agreeing to a Memorandum of Understanding, the partners in Germany, France, the Netherlands, Austria, and Italy, have all confirmed their participation. Following this milestone, the project's transition into its preliminary design phase was approved at a kick-off meeting held in Vienna. Two weeks earlier, on September 18, the consortium and the European Southern Observatory (ESO), which is building the telescope, have signed the corresponding collaboration agreement.

As the first dedicated camera for the E-ELT, MICADO will equip the giant telescope with a capability for diffraction-limited imaging at near-infrared...

Im Focus: Locusts at the wheel: University of Graz investigates collision detector inspired by insect eyes

Self-driving cars will be on our streets in the foreseeable future. In Graz, research is currently dedicated to an innovative driver assistance system that takes over control if there is a danger of collision. It was nature that inspired Dr Manfred Hartbauer from the Institute of Zoology at the University of Graz: in dangerous traffic situations, migratory locusts react around ten times faster than humans. Working together with an interdisciplinary team, Hartbauer is investigating an affordable collision detector that is equipped with artificial locust eyes and can recognise potential crashes in time, during both day and night.

Inspired by insects

Im Focus: Physicists shrink particle accelerator

Prototype demonstrates feasibility of building terahertz accelerators

An interdisciplinary team of researchers has built the first prototype of a miniature particle accelerator that uses terahertz radiation instead of radio...

Im Focus: Simple detection of magnetic skyrmions

New physical effect: researchers discover a change of electrical resistance in magnetic whirls

At present, tiny magnetic whirls – so called skyrmions – are discussed as promising candidates for bits in future robust and compact data storage devices. At...

Im Focus: High-speed march through a layer of graphene

In cooperation with the Center for Nano-Optics of Georgia State University in Atlanta (USA), scientists of the Laboratory for Attosecond Physics of the Max Planck Institute of Quantum Optics and the Ludwig-Maximilians-Universität have made simulations of the processes that happen when a layer of carbon atoms is irradiated with strong laser light.

Electrons hit by strong laser pulses change their location on ultrashort timescales, i.e. within a couple of attoseconds (1 as = 10 to the minus 18 sec). In...

All Focus news of the innovation-report >>>



Event News

EHFG 2015: Securing healthcare and sustainably strengthening healthcare systems

01.10.2015 | Event News

Conference in Brussels: Tracking and Tracing the Smallest Marine Life Forms

30.09.2015 | Event News

World Alzheimer`s Day – Professor Willnow: Clearer Insights into the Development of the Disease

17.09.2015 | Event News

Latest News

IP-cores for real-time signal processing in digital communication systems

07.10.2015 | Information Technology

Research initiative presents new traffic technologies for cities

07.10.2015 | Transportation and Logistics

Kick-off for a new era of precision astronomy

07.10.2015 | Physics and Astronomy

More VideoLinks >>>