本研究開發一個新穎的相位編碼視覺刺激器應用在穩態視覺誘發電位領域上。視覺刺激器是利用發光二極體當作光源，再將這多個單一光源使用相位編碼來實現連續相位的視覺刺激器。將這視覺刺激器結合於液晶顯示面板發展成為人機互動介面。兩個發光二極體之間的光合成，這是一個非線性處理結果，然而要能夠使用的系統必須是線性的結果。在此利用增加光源數目來解決非線性問題，藉由測量後的結果顯示這樣的方法確實是一個線性結果。根據國際腦電圖10-20系統規範，將電極線放置於Oz的位置，藉此測量視覺誘發的腦訊號。本研究著重於相位編碼視覺刺激器發展，相對在腦訊號上專注於訊號相位的處理。對於訊號中的相位處理方式，本研究將梳狀濾波器與一般的帶通濾波器拿來比較，藉由模擬與實際的訊號來驗證相位訊號去雜訊能力。數據顯示梳狀濾波器擁有較高的相位訊雜比能力。這樣的結果證明梳狀濾波器不僅僅是一個濾波器，它也有助於穩定相位的能力。梳狀濾波器更適合使用在處理相位編碼的穩態視覺誘發腦訊號。This study presents a novel phase encoding visual stimulator of steady-state visual evoked potential (SSVEP). Several single-light sources, generated by phase encoding flashes in light emitting diodes (LEDs), were used to achieve continuous-phase visual stimulator. That is combined with a liquid crystal display (LCD) panel to develop an interactive instrument. The light synthesis is a nonlinear process between LEDs. To consider the system be used singularity, it must be linear result. The nonlinear problem is solved by increasing the number of light sources. The measurement data confirm that the phase is approximately linear. Electroencephalogram (EEG) signals were measured by one EEG electrode placed at Oz position, referring to the international EEG 10-20 system. This study developed phase encoding visual stimulator, and signal processing focuses on signal phase of EEG. For signal processing of phase, the usefulness of comb and bandpass filters are compared by using simulated and real signals to verify phase signal denoising. The data show that comb filters produce a higher phase signal to noise ratio (SNR). The results obtained demonstrate that a comb filter not only filters but also maintains phase stability. The comb filter is more suitable for phase encoding of SSVEP.
