The Research Of VDT Visual Fatigue Based On Pulse Signal

With the change of the way of the modern life and work, the Visual TerminalDisplay (VDT) has been widely used in the people’s life and work. It has become oneof the most representative labor forms in the modern society. However, the healthproblem related to the VDT work has been increasingly concerned by more and morepeople, and the VDT–related visual fatigue is particularly outstanding. Therefore, ithas very great significance to realize the objective detection of the visual fatiguerelated to the VDT work. The complex mechanism of production of pulse signal makesthe pulse signal present non-stationary and nonlinear characteristics. It has closerelationship with the human health. In this paper, the pulse signals were used toevaluate the effect of the VDT visual fatigue on the human physiological signal inhope of finding out the objective physiological indexes to reflect the VDT visualfatigue. The main work of this paper was show as following:Described the relationship between the visual fatigue and the pulse signalrespectively, according to the Traditional Chinese Medicine (TCM) and the nervoussystem control, and demonstrated that it is feasible to realize the objective detection ofvisual fatigue with pulse signal. Meanwhile, the nonlinear generation mechanism andthe chaos characteristics of the pulse signal were analyzed in detail.This paper discussed the application of the wavelet transform in the biomedicalsignal processing. Furthermore, the wavelet function, zero phase filter and simpleintegral coefficients filter were used to remove the noise. The results have shown thatthe simple integral coefficients filter has very good contribution on the pulse noisereduction.Design VDT visual fatigue experiment to simulate the VDT work, acquire thepulse signals and calculate the pulse peak, pulse energy, the wavelet entropy and thepower spectral entropy of the pulse signals with special frequency. The dynamicanalysis was conducted out during the whole experimental process with the waveletentropy, pulse peak and the pulse energy. The experimental results had shown that,after the VDT work, the power spectral entropy with two frequency and the waveletentropy with frequency with156.25Hz increased significantly (p<0.05) compared withthat before the experiment, but there was no obvious change for the wavelet entropywith39.06Hz (p>0.05). The dynamic analysis had revealed that, with the deepening ofthe visual fatigue, the pulse peak and the pulse energy decreased gradually but thewavelet entropy raise significantly.Improve the experiment, add the control group, extend the task duration and add the latter checking task. Similarly, several parameters have been extracted from thepulse signals of the experiment group and the control group respectively: pulse peak,pulse energy, wavelet entropy, power spectral entropy and the approximate entropy.The dynamic analysis has also been carried out with pulse peak, pulse energy and theapproximate entropy. The results have shown that, for the special frequency of thepulse signal, the wavelet entropy, power spectral entropy and the approximate entropyincrease obviously (p<0.05), and the pulse peak and the pulse energy decreasesignificantly (p<0.05) after the VDT work, but no significant change are found for thecontrol group (p>0.05). The error rate rises after the VDT work, and it demonstratethat the long-time VDT work make the operators’ work quality decline. The dynamicchanges of the pulse peak and the pulse energy present more stable than that of the firstexperiment. This study provides a new method to realize the objective detection of thevisual fatigue.