mvs saram, what on earth are you talking about? Shutter glasses have been used for years, and they generally switch at around 60hz. The problem is the DEPTH of their switching. When off one eye is almost completely black, then it turns back on.. This modulation depth is what causes the problems not the frequency. If the modulation depth is deep enough (on off for example) I can see flicker at upwards 1000hz if the duty cycle is 50%, but only when the source is moving, or there's another out of phase modulation nearby (I can see the harmonic flicker) The fact that the switching of the eyes is perfectly anti phase that causes motion sickness when you move your head. I bet if you looked at the optical cortex of a person looking at a 3D screen with LCD shutter glasses on it'd be lit up like a Christmas tree.