Eyetracking Hardware:

This page describes some of the eyetracking hardware that I have developed. There are two sections:

(1) Lightweight Eyetracking Headgear (RIT)
(2) Firewire-based Eyetracking Headgear (ISU)

(1) Lightweight Eyetracking Headgear (RIT):

Figure 1.1 shows the eyetracking headgear that I helped develop while I was at the Visual Perception Lab at RIT. The headgear construction greatly simplifies the optics by using a microlens video camera (pointed at the eye) and a single infrared LED for "dark-pupil" eyetracking. The goal was to develop a simple eyetracking device that could be constructed from off-the-shelf parts. I have recently made this headgear compatible with my own custom eyetracking software for Mac OS X Tiger. Figure 1.2 shows a close-up of the microlens camera used to monitor the eye.

More on Dark-pupil

Like many video-based eyetracking systems, this headgear uses an infrared source to illuminate the eye. Figure 1.2 shows the small infrared LED (IRED) positioned next to the eye camera. This configuration is called dark-pupil illumination since the infrared falling into the pupil gets absorbed inside of the eye (instead of being reflected, as in the bright-pupil technique). The eye image in Figure 2.1 also shows the typical characteristics of a dark-pupil eye image.

An adjustable voltage regulator drives the LED, and a potentiometer is used to tune the LED circuit to the desired voltage and correct brightness. An 87c Wratten filter is placed over the camera sensor to block visible light so that only an infrared image can pass. This illumination configuration provides clear pupil and corneal glint boundaries that are easy to track.

Calibration

While looking at a series of points in the scene, the vector distance between the center of the pupil and the center of the corneal reflection (resulting from the IRED) can be mapped to corresponding points in the scene using a simple linear mapping. This "calibration" can be used to map eye position to where the person is looking in the scene camera.

Configuration

The headgear is designed so that minimal adjustment is needed to acquire a good image of the eye. Repositioning the eye camera is easy since it is mounted on flexible wire.

For more details read the PDF:

Babcock, J.S., and Pelz, J. (2004). Building a lightweight eyetracking headgear, ETRA 2004: Eye Tracking Research and Applications Symposium, 109-113.

(2) Firewire-based Eyetracking Headgear (ISU):

As a result of the RIT open-hardware eye-tracker, a project was initiated at the Human Computer Vision Lab at Iowa State University's HCI department (during the summer of 2004) to develop a complete open-hardware and open-software digital image eye-tracking system. Research focused on migrating away from analog video capture devices to a fully digital eye-tracking system. The motivation of this research was to provide a cost-effective eye-tracking tool that would encourage the integration of eye movement research into the human-computer interaction field. Figures 2.1 and 2.2 show a snapshot of the system that I helped develop during August 2004. The headgear is constructed from two firewire webcameras.

Figure 2.2 shows the Linux-enabled backpack used for the ISU project. The backpack carries a Sony PCG-GRT200 series laptop with a 3.1Ghz Pentium processor. The August 2004 prototype performed real-time (30 Hz) pupil tracking and superimposed the fixation position over the scene image. To reduce the laptop's weight and profile, both the LCD and keyboard were removed. The battery attachment was also modified to sit on top of the laptop where the keyboard was previously attached.

This project continues forward and the latest details can be found here:

Winfield, D., Li, D., Babcock, J., Parkhurst, D. J. (2005). Towards an open-hardware open-software toolkit for robust low-cost eye tracking in HCI applications. Iowa State University Human Computer Interaction Technical Report ISU-HCI-2005-04.