根據視覺誘發電位(Steady-State Visual Evoked Potentials, SSVEP)設計的大腦人機介面(Brain-Computer Interface, BCI)並執行特定動作已經是腦波在科學方面應用常見的例子，針對不同頻率所造成的反應，發現出兩個問題：若刺激為低頻，會有不舒適的現象，反之刺激若為高頻則誘發能量反應不明顯。從演算法或是硬體其實都沒有辦法改善這兩種狀況。 本論文提出改變刺激源呈現方式：調整刺激源Onset、和Offset的時間，藉以達成降低疲勞度的好處，不僅可以改變刺激源外觀，還可以保留大部分的誘發能量，達到既不耗損能量、又能夠提高舒適度的非對稱低頻閃爍刺激源。 在應用方面將非對稱刺激源利用相位編碼(Phase Coding)控制家電，其正確率平均可達到接近90%，簡單來說改變了刺激源的方式並不會造成推動BCI系統上面的影響，利用這樣的變化所帶來的好處，可以使受測者更舒適。 Due to high transfer rate (ITR), minimal training and noninvasiveness of the features in electroencephalography (EEG) system, steady-state visual evoked potentials (SSVEP) recorded from occipital scalp have been used as signal input for implementing brain computer interface (BCI) systems. These SSVEP-based BCIs require subjects to gaze at one or more flickering sources to evoke SSVEPs for system control. Nevertheless, due to the frequency preference of SSVEPs in human, the flickering frequency used for SSVEP stimulation is usually controlled lower than 27 Hz. The use of stimulation frequency equaled or lower to medium stimulation range (? 27 Hz) inevitably causes subjects’ uncomfortableness. Accordingly, this thesis aims to present a brain-computer interface (BCI) with adjustable on-off duration in order to suppress users’ uncomfortableness. The proposed system has been used to control six functions of a remote controller with acceptable accuracy (~90%) and high information transfer rate (ITR).
