Application of unconstrained BCG extraction in VDT visual fatigue monitoring

Eye diseases caused by long times of use of visual display terminal (VDT) products is considered as a serious problem in recent years. The eye fatigue monitoring is significant for early warning. Here, an unconstrained measuring method is used to extract Ballistocardiogram (BCG) by acceleration sensor. The acceleration signals are acquired by installing the sensor on seat back. Adaptive threshold wavelet transform is processed for denosing non-linear noise interference such as power line interference, baseline drift, random movement of human body, and ground vibration. Frequency domain filtering and IFFT are applied to extract BCG from acceleration sensor. RR interval of ECG and JJ interval of BCG in time domain have the similar cycle, and the correlation coefficient is up to 0.9918, which prove the feasibility to extract BCG from vibration signals using unconstrained method.