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G 0 Figure 6.
all faults common to methods using the fixed stretched network screen.
In an attempt to remedy these faults, the Russians sought to achieve a selector system consisting of conical converging diopters. Unable to achieve the diopters mechanically by means used in optics, they tried to obtain the results by photographic means, probably by utilizing the properties of bichromate on the film emulsion, which permits an apparent relief.
Nevertheless, the Russians have made a careful study of the momentous problems of stereoscopic motion pictures, but they have struck a technical impossibility in realizing a suitable selector of transmission that does not produce the faults of light absorption and diffraction already discussed.
We have discussed the principal obstacles stopping the use of lined networks so that you will know of the difficulties of direct-vision stereoscopic projection.
Noaillon proposed to solve the problems by utilizing oscillating grills starting with a selector system with much larger openings between grills, which simplifies the construction of the stereoscopic network.
A New DirectVision Stereo-Projection Screen
Francois Savoye, member of the Commission of Color and Relief of the French National Cinema Centre, solved some of these problems in the design of this new free-vision screen.
This system is based on the properties of stereo-selection given by a rotating conical shaped grill T as shown in Figs. 6 and 8, moving around the surface of the screen E. This is part of the Noaillon theory with formation of converging zones, on the plane perpendicular to the plane on the screen. This device enables the collective directvision of stereoscopic pairs.3 The impressions of relief are obtained in the same manner as by natural vision. Each spectator sees the right picture D for the right eye and the left picture G for the left eye. The rotating grill driven by motor M produces total shading, by persistence of vision sweeping the screen, thus showing the whole picture with all its detail in color or black-and-white.
Figure 7 shows a 5-ft screen with a projected stereo-image. This was photographed with a stereo-camera from the spectator's seat.
For the sake of simplicity, we will describe the engineer's model. The revolving grill in Fig. 8 is constructed of 108 aluminum bars forming the conical section. The top support of the cone is 36 in. in diameter. This accommodates a beaded screen 18 in. X 24 in. Each bar is set on geometric lines at
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July 1952 Journal of the SMPTE VoL 59