Tuesday, November 2, 2010

Optimization and Dynamic Simulation of a Parallel Three Degree-of-Freedom Camera Orientation System (T. Villgrattner, 2010)

Moving a camera 2500 degrees per second is such an awesome accomplishment that I cannot help myself, shamelessly long quote from IEEE Spectrum:


German researchers have developed a robotic camera that mimics the motion of real eyes and even moves at superhuman speeds. The camera system can point in any direction and is also capable of imitating the fastest human eye movements, which can reach speeds of 500 degrees per second. But the system can also move faster than that, achieving more than 2500 degrees per second. It would make for very fast robot eyes. Led by Professor Heinz Ulbrich at the Institute of Applied Mechanics at theTechnische Universität München, a team of researchers has been working on superfast camera orientation systems that can reproduce the human gaze.

In many experiments in psychology, human-computer interaction, and other fields, researchers want to monitor precisely what subjects are looking at. Gaze can reveal not only what people are focusing their attention on but it also provides clues about their state of mind and intentions. Mobile systems to monitor gaze include eye-tracking software and head-mounted cameras. But they're not perfect; sometimes they just can't follow a person's fast eye movements, and sometimes they provide ambiguous gaze information.

In collaboration with their project partners from the Chair for Clinical Neuroscience, Ludwig-Maximilians Universität MünchenDr. Erich Schneider, and Professor Thomas Brand the Munich team, which is supported in part by the CoTeSys Cluster, is developing a system to overcome those limitations. The system, propped on a person's head, uses a custom made eye-tracker to monitor the person's eye movements. It then precisely reproduces those movements using a superfast actuator-driven mechanism with yaw, pitch, and roll rotation, like a human eyeball. When the real eye move, the robot eye follows suit.

The engineers at the Institute of Applied Mechanics have been working on the camera orientation system over the past few years. Their previous designs had 2 degrees of freedom (DOF). Now researcher Thomas Villgrattner is presenting a system that improves on the earlier versions and features not 2 but 3 DOF. He explains that existing camera-orientation systems with 3 DOF  that are fast and lightweight rely on model aircraft servo actuators. The main drawback of such actuators is that they can introduce delays and require gear boxes.

So Villgrattner sought a different approach. Because this is a head-mounted device, it has to be lightweight and inconspicuous -- you don't want it rattling and shaking on the subject's scalp. Which actuators to use? The solution consists of an elegant parallel system that uses ultrasonic piezo actuators. The piezos transmit their movement to a prismatic joint, which in turns drives small push rods attached to the camera frame. The rods have spherical joints on either end, and this kind of mechanism is known as a PSS, or prismatic, spherical, spherical, chain. It's a "quite nice mechanism," says Masaaki Kumagai, a mechanical engineering associate professor at Tohoku Gakuin University, in Miyagi, Japan, who was not involved in the project. "I can't believe they made such a high speed/acceleration mechanism using piezo actuators."

The advantage is that it can reach high speeds and accelerations with small actuators, which remain on a stationary base, so they don't add to the inertial mass of the moving parts. And the piezos also provide high forces at low speeds, so no gear box is needed. Villgrattner describes the device's mechanical design and kinematics and dynamics analysis in a paper titled "Optimization and Dynamic Simulation of a Parallel Three Degree-of-Freedom Camera Orientation System," presented at last month's IEEE/RSJ International Conference on Intelligent Robots and Systems.




The current prototype weighs in at just 100 grams. It was able to reproduce the fastest eye movements, known as saccades, and also perform movements much faster than what our eyes can do.  The system, Villgrattner tells me, was mainly designed for a "head-mounted gaze-driven camera system," but he adds that it could also be used "for remote eye trackers, for eye related 'Wizard of Oz' tests, and as artificial eyes for humanoid robots." In particular, this last application -- eyes for humanoid robots -- appears quite promising, and the Munich team is already working on that. Current humanoid eyes are rather simple, typically just static cameras, and that's understandable given all the complexity in these machines. It would be cool to see robots with humanlike -- or super human -- gaze capabilities.

Below is a video of the camera-orientation system (the head-mount device is not shown). First, it moves the camera in all three single axes (vertical, horizontal, and longitudinal) with an amplitude of about 30 degrees. Next it moves simultaneously around all three axes with an amplitude of about 19 degrees. Then it performs fast movements around the vertical axis at 1000 degrees/second and also high dynamic movements around all axes. Finally, the system reproduces natural human eye movements based on data from an eye-tracking system." (source)

Monday, November 1, 2010

ScanMatch: A novel method for comparing fixation sequences (Cristino et al, 2010)

Using algorithms designed to compare DNA sequence in eye movement comparison. Radical, with MATLAB source code, fantastic! Appears to be noise tolerant and outperform traditional Levenshtein-distance.

Abstract
We present a novel approach to comparing saccadic eye movement sequences based on the Needleman–Wunsch algorithm used in bioinformatics to compare DNA sequences. In the proposed method, the saccade sequence is spatially and temporally binned and then recoded to create a sequence of letters that retains fixation location, time, and order information. The comparison of two letter sequences is made by maximizing the similarity score computed from a substitution matrix that provides the score for all letter pair substitutions and a penalty gap. The substitution matrix provides a meaningful link between each location coded by the individual letters. This link could be distance but could also encode any useful dimension, including perceptual or semantic space. We show, by using synthetic and behavioral data, the benefits of this method over existing methods. The ScanMatch toolbox for MATLAB is freely available online (www.scanmatch.co.uk).
  • Filipe Cristino, Sebastiaan Mathôt, Jan Theeuwes, and Iain D. Gilchrist
    ScanMatch: A novel method for comparing fixation sequences
    Behav Res Methods 2010 42:692-700; doi:10.3758/BRM.42.3.692
    Abstract   Full Text (PDF)   References





An improved algorithm for automatic detection of saccades in eye movement data and for calculating saccade parameters (Behrens et al, 2010)

Abstract
"This analysis of time series of eye movements is a saccade-detection algorithm that is based on an earlier algorithm. It achieves substantial improvements by using an adaptive-threshold model instead of fixed thresholds and using the eye-movement acceleration signal. This has four advantages: (1) Adaptive thresholds are calculated automatically from the preceding acceleration data for detecting the beginning of a saccade, and thresholds are modified during the saccade. (2) The monotonicity of the position signal during the saccade, together with the acceleration with respect to the thresholds, is used to reliably determine the end of the saccade. (3) This allows differentiation between saccades following the main-sequence and non-main-sequence saccades. (4) Artifacts of various kinds can be detected and eliminated. The algorithm is demonstrated by applying it to human eye movement data (obtained by EOG) recorded during driving a car. A second demonstration of the algorithm detects microsleep episodes in eye movement data."

  • F. Behrens, M. MacKeben, and W. Schröder-Preikschat
    An improved algorithm for automatic detection of saccades in eye movement data and for calculating saccade parameters. Behav Res Methods 2010 42:701-708; doi:10.3758/BRM.42.3.701
    Abstract  Full Text (PDF  References





Thursday, October 28, 2010

Gaze Tracker 2.0 Preview

On my 32nd birthday I'd like to celebrate by sharing this video highlighting some of the features in the latest version of the GT2.0 that I've been working on with Javier San Agustin and the GT forum. Open source eye tracking have never looked better. Enjoy!


HD video available (click 360p and select 720p)

Friday, October 1, 2010

Tuesday, August 17, 2010

How to build low cost eye tracking glasses for head mounted system (M. Kowalik, 2010)

Michał Kowalik of the Faculty of Computer Science and Information Technology at the West Pomeranian University of Technology in Szczecin, Poland, has put together a great DIY instruction for a headmounted system using the ITU Gaze Tracker. The camera of choice is the Microsoft LifeCam VX-1000 which has been modified by removing the casing and IR filter. In addition, three IR LEDs illuminate the eye using power from the USB cabel. This is then mounted on a pair of safety glasses, just like Jason Babcock & Jeff Pelz previously have done. Total cost of the hardware less than 50€. Neat. Thanks Michal.

Download instructions as PDF (8.1Mb)

    Monday, August 16, 2010

    Call for Papers: ACM Transactions Special Issue on Eye Gaze

    ACM Transactions on Interactive Intelligent Systems
    Special Issue on Eye Gaze in Intelligent Human-Machine Interaction

    Aims and Scope

    Partly because of the increasing availability of nonintrusive and high-performance eye tracking devices, recent years have seen a growing interest in incorporating human eye gaze in intelligent user interfaces. Eye gaze has been used as a pointing mechanism in direct manipulation interfaces, for example, to assist users with “locked-in syndrome”. It has also been used as a reflection of information needs in web search and as a basis for tailoring information presentation. Detection of joint attention as indicated by eye gaze has been used to facilitate computer-supported human-human communication. In conversational interfaces, eye gaze has been used to improve language understanding and intention recognition. On the output side, eye gaze has been incorporated into the multimodal behavior of embodied conversational agents. Recent work on human-robot interaction has explored eye gaze in incremental language processing, visual scene processing, and conversation engagement and grounding.

    This special issue will report on state-of-the-art computational models, systems, and studies that concern eye gaze in intelligent and natural human-machine communication. The nonexhaustive list of topics below indicates the range of appropriate topics; in case of doubt, please contact the guest editors. Papers that focus mainly on eye tracking hardware and software as such will be relevant (only) if they make it clear how the advances reported open up new possibilities for the use of eye gaze in at least one of the ways listed above.

    Topics

    • Empirical studies of eye gaze in human-human communication that provide new insight into the role of eye gaze and suggest implications for the use of eye gaze in intelligent systems. Examples include new empirical findings concerning eye gaze in human language processing, in human-vision processing, and in conversation management.
    • Algorithms and systems that incorporate eye gaze for human-computer interaction and human-robot interaction. Examples include gaze-based feedback to information systems; gaze-based attention modeling; exploiting gaze in automated language processing; and controlling the gaze behavior of embodied conversational agents or robots to enable grounding, turn-taking, and engagement.
    • Applications that demonstrate the value of incorporating eye gaze in practical systems to enable intelligent human-machine communication.

    Guest Editors

    • Elisabeth André, University of Augsburg, Germany (contact: andre[at]informatik[dot]uni-augsburg.de)
    • Joyce Chai, Michigan State University, USA

    Important Dates

    • By December 15th, 2010: Submission of manuscripts
    • By March 23rd, 2011: Notification about decisions on initial submissions
    • By June 23rd, 2011: Submission of revised manuscripts
    • By August 25th, 2011: Notification about decisions on revised manuscripts
    • By September 15th, 2011: Submission of manuscripts with final minor changes
    • Starting October, 2011: Publication of the special issue on the TiiS website and subsequently in the ACM Digital Library and as a printed issue
     Source http://tiis.acm.org/special-issues.html

    Tuesday, August 10, 2010

    Eye control for PTZ cameras in video surveillance

    Bartosz Kunka, a PhD student at the Gdańsk University of Technology have employed a remote gaze-tracking system called Cyber-Eye to control PTZ cameras in video surveillance and video-conference systems. The movie prepared for system presentation on Research Challange at SIGGRAPH 2010 in Los Angeles.

    Wednesday, August 4, 2010

    EOG used to play Super Mario

    Came across some fun work by Waterloo labs that demos how to use a bunch of electrodes and a custom processing board to do signal analysis and estimate eye movement gestures though measuring EOG. It means you'll have to glance at the roof or floor to issue commands (no gaze point-of-regard estimation). Good thing is that the technology doesn't suffer from issues with light, optics and sensors that often makes video based eye tracking and gaze point-of-regard estimation complex. Bad thing is that it requires custom hardware, mounting of electrodes and wires, besides that the interaction style appears to involve looking away from what you are really interested in.

    Sunday, July 18, 2010