The easiest solution to obtain tri-dimensional pictures to be viewed directly - that is without glasses - consists in using lenticular screens directly associated to matricial scanning. But if we put only with two pictures (as in stereophotography) the right viewing angle is limited. To improve it, the number of pictures must be increased to four at least. The transmission of four pictures is possible on one way only, thanks to the simultaneous use of matricial analysis and numerical modulation. Anyway, we meet the problem of the passing band if we do not want to loose definition. In this point of view, the numerical modulation permits to reduce greatly the passing band, taking into consideration that in several pictures, there are a great number of identical pixels : it is then useless to transmit them on several ways.
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