There are many methods for reproducing stereo-pictures (three dimensional pictures) such that the observer has the full spatial impressions of the object. This is done, e.g., by arranging the two pictures recorded from two different directions, as the two eyes of an observer view from the corresponding directions, on a screen and viewing the pictures through glasses of different color for non-color reproduction. If a color image is required, the different pictures are illuminated with linear polarized light of perpendicular orientation and glasses are used with the appropriate polarization such that the eyes see the objects separately in stereo. One difficulty with the foregoing is that the eyes are focused in an unnatural way, i.e. looking in different directions on alternate frames, if the reproduced pictures have to be next to each other.
The ideal method requires that the two reproduced pictures of different polarization be located within the same frame. This can be realized, e.g., by holographic production of the color TV picture. This method, however, is basically limited by the coherence length of the radiation such that the stereo effects can be seen only within a certain depth, e.g., 30 centimeters to 1 meter with the current generation of holographic reproduction equipment. This depth, even if extended, is limited by basic principles of physics. A further difficulty is that the granulation of the transmitted picture requires extremely high resolution and very small grain photographic material must be used. The electronic transmission of such pictures also requires an extraordinarily large bandwidth and minimal signal distortion.