Fatigue evaluation by detecting blink behaviour using eyeglass‐shaped optical sensor system

Abstract

Death from overwork and severe accidents caused by mental fatigue and sleepiness are becoming one of the more pressing social problems of developed countries. Such mental fatigue and sleepiness often comes from declines and/or changes in wakefulness in our daily life. Recently, numerous researchers have focused on possible ways of utilising physiological signals to deduce alertness; however, the characteristic behaviours that can be used to deduce wakefulness are difficult to measure. To better understand the indices of change in wakefulness states, the authors fabricated a micro-optical sensor system that can measure physiological signals from eye and eyelid conditions without imposing stress on the user. Using the newly fabricated micro-optical sensor system, they have found and reproduced characteristic blink behaviours that are indicative of changes in a person's wakefulness. Herein, new indices are proposed that have potential for use in fatigue evaluation tests. The experimental results demonstrate that the sensor system can detect declines in and/or changes in wakefulness that indicate mental fatigue and sleepiness.

Fatigue Assessment by Blink Detected with Attachable Optical Sensors of Dye-Sensitized Photovoltaic Cells

“…The experiments were conducted for four subjects, and the average and standard deviation is shown in Figure 5 . It was found to be as high as 94% and showed no significant difference ( p -value > 0.05) from our previous device [ 15 ].…”

“…Table 1 summarizes the results obtained in our prior work with an eyeglass-type system [ 15 ] and this work with the smart glass. The indices obtained by the smart glass system were found to be better than those obtained by the eyeglass system.…”

“…In our prior work, we investigated the successful detection of the eye blinks with respect to the threshold. Based on the experimental results, we set the threshold to be 70% of the maximum voltage change rate [ 14 , 15 ], as illustrated in Figure 1 b. The optimal position of the cells to have the most reliable detection was experimentally deduced.…”

“…Information acquired from eyes, including movement of the eye and eye blinks, provides the state of the subjects [ 11 , 12 , 13 ]. In order to obtain the information with minimal physical and mental stress, we used a wearable, see-through eyeglass-type eye-tracking system [ 14 , 15 ]. The system had an array of transparent optical sensors, which were dye-sensitized photovoltaic devices [ 16 , 17 , 18 ].…”

“…The sensor system was wearable and light, and did not have cameras pointing at the user, and therefore, provided little physical and mental stress. In our prior work, the indices related to eye blinks were found to reflect the fatigue of the subjects [ 15 ]. In this work, in order to further reduce stress to the users, we designed and fabricated a system to detect eye blinks, which can be attached to the temple of the eyeglasses and positioned at the lateral side of the face, as shown in Figure 1 .…”