Detection of the line-of-sight (LOS) has a variety of applications, such as communication tools for elderly or disabled people, assisting drivers, and effective location of traffic signs. To realize such promising applications, there is strong demand for an LOS detection system that does not restrict users' activities and inflicts no mental stress. The LOS can be obtained by combining the directions of the face and eyes, respectively, where the detection of location and motion of the pupils is a critical technology. In this paper, we propose a novel wearable pupil position detection system, featuring minimum disturbance to users, both physically and mentally, via the use of dye-sensitized photovoltaic devices. These latter are transparent and generate voltage according to the incident light intensity. Arraying the devices on wearable eyeglasses, this system detects the difference in the reflection light from the pupil and the white of the eye and hence determines the position of the pupil. It is wearable as an eyeglass, meaning it does not disturb users' activities or eyesight. More importantly, it involves minimal physical and psychological stress. We fabricated the photovoltaic device and demonstrated their feasibility to determine the location of the pupil. We found it possible to meet the required reaction time of 100 ms by reducing the size of the device and to improve the accuracy of pupil location detection by arraying the devices.
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