Rear view of prototype system showing the continuous loop of 72" x 9 1/2" holographic film, the transport and the motor. Because the transfer of the cine to the hologram results in the laterally spread representation of differing perspectives in time as well as space, the obvious problem of multiple viewers seeing the image in sound sync arises. Because of the endless loop nature of the holographic film we used a Tapecaster unit often used for short radio spots. The "mono" deck actually has an inaudible second track used for sync and cueing beeps. An output port exists on the back of the Tapecaster to send these pulses to other devices. This enabled us to signal relays actuated by the microprocessor to turn the motors on and off along with controlling the lights.    One parameter placed upon the project was for the playback of the two images (one of Sheik Mohammed the other of one of his wives) to appear from seated positions on either side of a breakfast table. This made it easier to assure the lip synchronous appearance of the two images because we knew exactly (give or take a couple of degrees) what the viewers vantage point would be.    In the future we can expect "true" holographic movies (described in March 1984 American Cinematographer) to allow for a broad audience viewing of sound synchronous imagery without the constraints encountered in the system described here. This would occur simply because a "true" holographic motion picture format would yield continuous parallax. The viewers would experience differing perspectives in space only if they changed their seats. Using the integral format of holography, their differing vantage points yield different perspectives in time as well. We were fortunate in this display application that the viewers angle had been fixed. The original footage was shot in 35mm on an Arriflex 11C at twice sound speed to avoid time smearing on the lips. Time smearing is an anomaly that usually takes place in integral format holograms when there is an excessive rate of motion in relation to the frame per second rate. Ordinarily holograms made in this format are shot at 24fps and 45 seconds of action amounts to a hologram 9 1/2 inches high by about 52 inches in length, depicting a 36O degree perspective of the subject as a complete rotation is made on the turntable.    Because I chose to film at 48fps to avoid time smearing, our 52 inch long hologram depicted only 22.5 seconds of action and 18O degrees of perspective shifts. (In other words left profiles to right profiles.) This was acceptable since the backs of the subjects' heads were not visually interesting.    The sound was recorded on a Nagra 4S at 15fps from a microphone mounted on the turntable upon which the subjects were sitting. The mike had to be isolated from the turntable motor vibrations. The articulation needed to be distinct and steady in order to have the appearance of a clear lip sync which proved a little difficult considering the Arabic language. Roughly translated, Sheik Mohammed is heard to say in Arabic "Good morning, welcome, have a nice meal." After each take the action was reviewed on 3/4" tape and ultimately the best takes were used in the transfer to holograms.    Rodd Finlay of Finlay Displays was called in to review preliminary sketches for the "beasts" and help actualize the concept. After some brainstorming we arrived at a workable loop technique for the talking hologram machines. Working closely wth Larry Lieberman of Holographic Research we arrived at two holographic prints suit able for mounting into "the beasts". The holograms being 54" long required a piece of clear acetate 18" long to be spliced on to the hologram to give the complete loop the 72" required for our film train.    The various electromechanical elements of these two systems required exacting and precise interaction. For this reason Alif Kahwand of Disco Lighting Systems (the contractor of this project) designed a microprocesser specifically to coordinate and execute the various commands. In order for the microprocessor to literally make heads or tails of the continuous loop hologram, infrared emitter/detector diodes were positioned facing each other with the film running without physical contact between them. When a piece of infrared opaque tape passed the detectors it would send a cue as to where the film was at that time. After reviewing the possibilities of putting the sound onto the film optically or magnetically we decided to use a separate device for that function, rather than try to reinvent the wheel, so to speak. In the past, several techniques had been considered for syncing sound to a hologram. One concept involved the use of a multi-track tape recorder which would send its timed off set signals to individual head sets positioned at 90 degree increments from each other for synchronous viewing by four people at a time.