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The research in holographic cinematography has been conducted in Russia (Soviet Union) since mid-70s. Our research group at NIKFI has worked out the following principles. First, the holographic film was made by two methods: in laser light and in ordinary non-coherent light (the lens-raster method with subsequent conversion of the raster image into a holographic image). Second, we used lenses with large aperture (about 200 mm) for photography and projection. Third, the special screens focus and multiply the image according to the number of viewers. Fourth, we used the holographic film stocks with a thick emulsion layer of about 10 micrometers for storing and reproducing the colored 3-dimensional image.
These principles were tested out at NIKFI experimentally by photographing and projecting (simultaneously for several viewers) short holographic films with a 3-dimensional monochromatic (1976) and colored (1984) image. The overall running time of the holographic films was about five minutes.
The Theoretical Foundations of the Holographic Cinema Process
Using the holographic cinematography schemes studied by Emmet Leith (a large lens), Yuri Denisyuk (a large mirror) and
Takanori Okoshi (a set of mirrors), it is impossible to show holographic movies simultaneously for more than one or two viewers.
There is only a single zone of the reproduction of 3D image in these methods
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In our holographic cinematography system we were able to create a multi-zone image reproduction scheme, where the image is multiplied by a special holographic screen. Thus, our system overcomes the major limitations of the holographic filmmaking, and it is possible to have an arbitrary number of seats in the holographic movie theatre.
In the holographic cinema schemes, where an image is roughly equidistant from the film stock and from the viewer's eyes, the image quality is very low. This is the result of the extremely intense speckle or extremely low depth sharpness. In our holographic cinema system this problem is solved by using a rotating light-scattering disk located near the center of homocentric reconstructing beam in the laser projector. As a result, the speckle is removed and the depth sharpness increases.
We also worked out: a) the frame size on the holographic film stock was determined mathematically during raster photography depending on the distance between the viewer and the image (the holographic camera and the nearest object); b) the minimum camera-object distance was determined with the acceptable frame size on the film stock; c) the energy of the laser pulse during the shooting of holographic films was determined depending on the film stock sensitivity and the object's area; d) we found out the photographed scene size attainable with relatively low laser radiation energies; e) the laser power for the holographic projection has been determined depending on the number of seats (it is shown that the appropriate laser power for projection puts practically no limit on the number of seats in the holographic movie theatre).
Furthermore we determined the optimum laser radiation wavelengths for achieving the most exact color rendering in holographic cinema. It has been shown in our work that the high quality of the colored image can be obtained with only three laser wavelengths. As a result, a holographic screen with high diffraction efficiency and with the acceptable noise level can be designed for a practically unlimited number of viewers.
The Experimental Holographic Movie System
Our first holographic color cine-system, worked out in 1981-85, consisted of the following elements: a) a camera for photography on 70 mm holographic film stock with a frame size of 51 by 47 mm (with the interrupted holographic film stock moving at a rate of up to 24 frames per second); b) the lens with a focal length of 150 mm and an aperture of 22 mm; c) laser camera for photography with pulsed lasers and continuous lasers; d) laser camera for vacuum clamping of the holographic film stock.
Two different projectors were also developed. They had lens with a focal length of 250 mm and with an aperture of 200 mm. In the first projector the lasers were used, in the second one there was a mercury-cadmium lamp. Of course, the projector with the laser gives a larger depth of image sharpness, but it is more complex. The projector with the lamp is simpler and cheaper, but depth is low.
There were three versions of devices for reproducing holographic movie image. In the first and second versions the projection was performed immediately on a multiplying point-focusing holographic screen by size 1x0.8 m. In the first version the holographic screen for monochromatic projection (0.578 mm in the yellow spectrum) had five viewing zones. In the second version the holographic screen for colored projection (0.647 mm in the red spectrum and 0.510 mm in the green spectrum) had two viewing zones.
In the third version, projection was made onto a mirror-film round vacuum screen 2m in diameter. The light beam from the cine-projector fell on the intermediate holographic screen. The screen reflected 24 separate beams, which ware directed and focused on 24 mirror lenses. Beams reflected from mirror lenses were directed and focused on a large mirror-film vacuum screen. Beams reflected from the screen formed 24 viewing zones in the movie theatre. In these zones viewers could see three-dimensional images.
Two printers were developed for printing copies of holographic films. In the first printer the original film and the holographic film stock were placed close to each other. In the second printer the lens was placed between them. The advantage of the second device is that it ensures reversal of the image and choice of the optimum ratio of the intensities of the object beam and the reference beam separately.
Several short experimental holographic films with an overall running time of about five minutes were made at NIKFI. The NIKFI two-layered film stock was used for colored holographic frames. The sensitivity of this 70 mm film stock in the red (0.647 mm) and green (0.514 mm) regions of the spectrum was about 5,000 erg/sq cm, the diffraction efficiency was 70 percent, a noise level was 0.007 (a ratio of the intensity of scattered light to the intensity of reconstructing beam). For shooting of the colored miniature holographic films we used lasers Spectra Physics (model 171). A krypton laser (0.647 mm) was used when the power was 0.8 W, and an argon laser (0.514 mm) was used when the power was 1.2 W. Monochromatic frames were photographed on the Agfa-Gevaert 8E75 HD and 8E56 HD film stock, using a ruby (0.695 mm) and a garnet (0.530 mm) pulsed laser (with a pulse energy of 0.1 j and with a pulse repetition rate of up to 24 per second).
Studies, conducted under the guidance of Prof. Anatoly Boubinov, have shown that shooting and printing holographic films can be made with the use of lamp-pumped dye lasers at optimum wavelengths. A pulse radiation energy of 5-10 j can be obtained with a repetition rate of 16-24 pulses per second, with a coherence length of 10-20 m and a pulse width about l m sec. Research carried out under Lev Logak's direction has shown that it is feasible to manufacture the appropriate holographic film stock for colored pulsed photography in laser light (red, green and blue).
The experimental holographic films are shown on the special screens. The holographic screen has a glass base covered by a photosensitive layer. We built a special installation for manufacturing holographic screens and exposition their photosensitive layers. Studies, performed under direction of the author of this article and Oleg Serov, have demonstrated technical possibility of commercial manufacturing holographic screens for colored projection for hundred seats and more.
After solving the problem of number of viewers we turned to the next stage of
developing our system: the technology of shooting and production the full-size holographic feature films,
including shooting on locations where the big objects couldn't be illuminated by
lasers. In the beginning of 2000s we conducted the research, which
confirmed a feasibility of 3D filming using a camera with only two lenses in regular non-coherent light.
Then a large number of intermediate angle-aspects is obtained by method of digital conversion.
As a result of this research the method of multi-angle landscape filming was completed, which in application to
holographic motion pictures meant taking off the limitation of film production by pavilion shooting. At the present
our technology allows making filming of any landscape in regular light with the subsequent transferring these images into
holographic ones. Thereby the last key disadvantage of our holographic movie system was eliminated.
Conclusions
What are the possibilities of applying these results? Technically it is feasible
to make the holographic feature films with normal running time up to 150
minutes, to manufacture on the commercial bases all equipment for holographic
movies and to open a holographic movie theater with unlimited number of seats.
Now we can say with confidence that this holographic movie system surpasses the
regular 35mm and stereoscopic-polarization motion pictures systems by all major
parameters, including brightness, sharpness and quality of color.
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