e shows the timing relationship of the two outputs of the video switch of fig1 and their sync signals i e the signals of fig1 b and 16d with two video projectors shown in fig1 projecting on the same screen using the same selection technique of polarized light as described with reference to fig4 the result is lines which are presented sequentially at nominally 60 fields second eye first the left line i e the signal of fig1 b is written by the left projector then the corresponding right line the signal of fig1 d is written by the right projector by adding additional memory and circuitry at each output the projector or display devices of fig1 could produce continuous images at any refresh rate but this isn 39 t needed for most applications in a practical implementation of this invention it is required to maintain a constant 34 video black 34 signal level during the h 2 time when there is no active video on each channel accordingly fig1 shows that a 34 video black 34 signal is supplied to the video switch when there is active video on a channel appropriate video dc restoration or 34 clamping 34 is required these techniques will prevent black level shifts leading to the possibility of contrast mismatch between the left and right channels and image flicker this technique will work not only for video protocols such as ntsc it will also work for component or composite video or computer generated images i e the system of fig1 could be used to process input signals of any of.