Steady-state visual evoked potential based brain-computer interface with viewing distance changes

In the Brain-Computer Interface (BCI) based on Steady-State Visual Evoked Potential (SSVEP), the viewing distance is usually fixed in the 1 m. However, the performance of SSVEP was decreased when the viewing distance is increasing. This paper aims to investigate the effects of viewing distance variation to the SSVEP. We designed an experimental environment with different viewing distance and generated four visual flicker which presented on LED monitor flickering in frequencies of 7, 8, 9, and 10 Hz. The Canonical correlation analysis (CCA) and event related spectral perturbation (ERSP) methods were used to analyze the frequency information of the acquired SSVEP signals. Our results show that the latencies of SSVEP were increased according to the viewing distances and visual angles. Therefore, we used phase constrained canonical correlation analysis (pCCA) to reflect the latency in viewing distance changes. As a result, the accuracy obtained from pCCA was higher than standard CCA method.