ExpertEyes: Open-source, high-definition eyetracking

• Published in: Behavior research methods 2015-03, Vol.47 (1), p.73-84
• Main Authors: Parada, Francisco J., Wyatte, Dean, Yu, Chen, Akavipat, Ruj, Emerick, Brandi, Busey, Thomas
• Format: Article
• Language: English
• Subjects: Behavioral Science and Psychology; Blinking - physiology; Cognitive Psychology; Computer peripherals; Eye Movements; Humans; Image Processing, Computer-Assisted - instrumentation; Image Processing, Computer-Assisted - methods; Open source software; Psychology; Pupil - physiology; Research methodology; Software; Software packages; Systems Integration; Tracking control systems; Video Recording - instrumentation; Video Recording - methods
• ISSN: 1554-3528; 1554-3528
• DOI: 10.3758/s13428-014-0465-z

ExpertEyes is a low-cost, open-source package of hardware and software that is designed to provide portable high-definition eyetracking. The project involves several technological innovations, including portability, high-definition video recording, and multiplatform software support. It was designed for challenging recording environments, and all processing is done offline to allow for optimization of parameter estimation. The pupil and corneal reflection are estimated using a novel forward eye model that simultaneously fits both the pupil and the corneal reflection with full ellipses, addressing a common situation in which the corneal reflection sits at the edge of the pupil and therefore breaks the contour of the ellipse. The accuracy and precision of the system are comparable to or better than what is available in commercial eyetracking systems, with a typical accuracy of less than 0.4° and best accuracy below 0.3°, and with a typical precision ( SD method) around 0.3° and best precision below 0.2°. Part of the success of the system comes from a high-resolution eye image. The high image quality results from uncasing common digital camcorders and recording directly to SD cards, which avoids the limitations of the analog NTSC format. The software is freely downloadable, and complete hardware plans are available, along with sources for custom parts.