1/2014

Facial expressions control and reveal

Ville Rantanen

 

Ville Rantanen is currently finalising his doctoral thesis on capacitive facial activity measurement.

 

The measurement of voluntary facial muscle activity yields information that can be used as control signals in human-computer interaction. Spontaneous facial expression measurement provides information that can be used in psychological tests and even in gaming applications.

A head-mounted prototype device measures facial activity caused by raising and lowering the eyebrows, and raising and pulling down the mouth corners. It can register both voluntary and spontaneous facial activity, as human facial expressions can be a rich source of information.

Information obtained by measuring voluntary facial muscle activity can be used as control signals in human-computer interaction. It enables physically disabled users to control their computers without hands, just by smiling, frowning, or lifting their eyebrows. Spontaneous facial expressions, on the other hand, can provide information that is valuable for behavioural sciences and healthcare applications.

User-friendly wireless measurement technology

Researchers in the Sensor Technology and Biomeasurements group at the Department of Automation Science and Engineering of Tampere University of Technology have developed a contactless method for detecting facial movements called capacitive facial activity measurement. The measurement is applied by a prototype of a head-mounted measurement device that incorporates several electrodes that are supported in front of the face to register the movement of facial muscles. The information registered by the device is transferred wirelessly to a computer that processes the measurement data. The wireless technology can also be used in a mobile environment.

“Because our capacitive facial activity measurement method is non-invasive and does not require facial contact, it is more user-friendly than surface electromyography (EMG), an alternative measurement method that requires uncomfortable electrodes to be attached to the face. It is also less demanding computation-wise than vision-based automated facial activity measurement,” says researcher Ville Rantanen.

Early adopters from the gaming industry?

The users who benefit from this new measurement technology are not limited to disabled patients, psychologists and healthcare professionals. Ville Rantanen believes the earliest adopters may well be found in the gaming industry.

Head-mounted facial activity measurement device

  • The head-mounted prototype measurement device is similar to an acoustic hearing protector
  • The required electronics are integrated into the earmuffs. The finger-like extensions positioned in front of the user’s face, yet not touching it, house the electrodes that perform the capacitive measurements
  • There are 22 measurement electrodes measuring 22 different signals indicating the distance between the face and the electrode
  • When the face moves, the distance between the electrode and the face varies
  • Ball joints between the electrodes allow the extensions to be adjusted according to the shape of the user’s face
  • A Bluetooth connection transfers the measurement data wirelessly to a computer running storage software
 

“People in the entertainment business are known for being receptive to new solutions and ideas. The ability to spot a tiny muscle twitch on a gamer’s face and transfer the information to another gamer might be an attractive proposition for a game developer,” he suggests.

Further work is required before the measurement technology can be commercialised, according to Rantanen.

Result of a collaborative effort

The technology for the new head-mounted prototype device has been developed in collaboration with the Research Group for Emotions, Sociality and Computing in the School of Information Sciences at the University of Tampere, who have carried out testing of the head-mounted prototype hardware that Rantanen and his colleagues at TUT have constructed.

The development work started already in 2007 as part of the four-year Face Interface project funded by the Academy of Finland. Subsequent work was funded by Nokia Research Center and Tekes – the Finnish Funding Agency for Technology and Innovation. Rantanen has also received personal funding for his research from several sources, such as the Finnish Cultural Foundation.

Text: Leena Koskenlaakso
Photo: Mika Kanerva

 
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