An improved phase-tagged stimuli generation method in steady-state visual evoked potential based brain-computer interface

This paper proposes an improved method for generating different phases of visual stimulus while liquid crystal display (LCD)/cathode ray tube (CRT) is employed as the visual stimulator. Since using the traditional method can only generate the limited frequencies and phases of visual stimulus, increasing the number of different flickering targets becomes very difficult in steady-state visual evoked potential (SSVEP)-based brain-computer interface (BCI). The experimental result shows that the proposed method can generate the visual stimulus with more phase angles than the traditional method. In addition, the proposed LCD visual stimulator can evoke the subject´s SSVEP with expected phase.