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Design and Construction of a Head-Mounted System for the Real-Time Measurement of Pupil Diameter Variations

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"Design and Construction of a Head-Mounted System for the Real-Time Measurement of Pupil Diameter Variations", (2007)
Joshi, V., and Barreto A.


It is well established that both the Sympathetic and the Parasympathetic divisions of the Autonomic Nervous System (ANS) control the diameter of the pupil in humans. Accordingly, changes in pupil diameter reflect the response of human subjects to changes in the environmental illumination and also to affective stimuli capable of triggering sympathetic or parasympathetic activation. In the past, pupil diameter variations had to be evaluated by manual measurements on individual movie frames. Currently, measurements of pupil diameter are frequently available from an Eye Gaze Tracking (EGT) system. However, the resolution of the imaging systems used in these instruments is not optimized for pupil diameter measurements. This paper reports the development of a new head-mounted system for the imaging of the pupil of a human subject. This system provides images at a higher resolution than in EGT systems, yielding a more usable pupil diameter signal. This signal is useful in discriminating relatively small changes in pupil size, which may reflect changes in the affective state of a computer user. The paper outlines the design and construction of the first prototype of our system and includes some sample images that confirm that a higher resolution in pupil imaging is achieved.