Abstract
Under certain situations, the eye pupils or heart of any human being represent the body’s states. The measurement of pupil size is one of the most immediate, accurate, and direct methods of autonomic-activity monitoring. For example, the autonomic activity of a subject in a spontaneous state or under any stimulus can be estimated through the size of the subject’s pupil, particularly through the pupil-light reflex (PLR) or pupil-size variability (PSV). Thus, the proper equipment (pupil-monitoring system) and experimental setting (dark room and pupil-image acquisition system) designed to not affect the subjects physically and emotionally have been developed.
The pupil-monitoring system used in this paper features a helmet and weighs about 130 g. It provides a wide field of vision and allows one to vary the position of one’s eyes. It is non-invasive and is less prone to affect the subject. So, it can be used under various postures during an experiment. It also allows the subject to be given certain visual stimuli, such as a visible-light stimulus for pupil-light reflex, or visual-cognitive tasks for pupil-size variability. Because visible light would affect pupil size, infrared light-emitting diode (LED) and monochrome infrared camera were instead used to illuminate and capture the pupil. An infrared passing filter was added in front of the camera lens to capture the images under various illumination conditions.
The pupil-image acquisition system proposed in this paper produces and saves an 8-bit, 640 x 480-pixel grayscale image, with a specific sampling rate, from the output of the pupil-monitoring system. The image-processing algorithm proposed in this paper efficiently distinguishes the pupil from other tissues in the acquired images, which ensures an accurate estimation of pupil size.
In the future, the image may be focused and the camera position may be fixed through simple automation, thereby reducing the length of preparation time.
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© 2007 International Federation for Medical and Biological Engineering
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Lee, JC., Kim, JE., Kyung-Mo, P. (2007). Development of a Pupil-size Monitoring System for Autonomic-activity Estimation. In: Magjarevic, R., Nagel, J.H. (eds) World Congress on Medical Physics and Biomedical Engineering 2006. IFMBE Proceedings, vol 14. Springer, Berlin, Heidelberg. https://doi.org/10.1007/978-3-540-36841-0_351
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DOI: https://doi.org/10.1007/978-3-540-36841-0_351
Publisher Name: Springer, Berlin, Heidelberg
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