**9. White light holographic cinematography**

The spectral depth coding by diffraction was first discovered in holograms (18) and matches perfectly the projection on diffracting screens generating the image through the decoding

Fig. 6. Hologram made in 35 mm film enlarged x40 by using white light

In a second approximation, we can consider the diffractive screen as a diffracting lens, that is, a bi-dimensional grating which puts the light it receives converging to a unique position, as a convergent ordinary optical element. A diffracting lens is obtained directly by a hologram made with two point sources. If we project in monochromatic light, the screen acts as the one of Komar, but, projecting in white light and making the screen with the point sources from the same side of the film, the diffracted transmitted images are affected by a horizontal dispersion. The same basic property that gives orthoscopic and pseudoscopic images with two gratings corresponds now to the same images but seen all over the screen extension. When the observer moves laterally, he receives continuous view sequences of the object. In this way it has been possible to observe the enlarged image of objects on a one square meter screen but an intense reduced size projection lamp and a dark ambience is necessary. To avoid the need of having the observer watching at a very precise height, one point source in the the interference process process is substituted by a thin vertical diffuser. It gives the vertical size of the observation region but with a reduced image brightness. Besides the limited diffraction efficiency, another brightness limitation results from the need

The spectral depth coding by diffraction was first discovered in holograms (18) and matches perfectly the projection on diffracting screens generating the image through the decoding

of a thin slit on the projecting lens to get maximum focal depth.

Fig. 6. Hologram made in 35 mm film enlarged x40 by using white light

**9. White light holographic cinematography** 

property a second diffracting element may have. Enlargement is the same for all three dimensions of the object. A small transmission hologram made with a lateral reference beam on 35 mm film can be enlarged on the screen by illuminating it with a halogen lamp (19). To obtain a better luminous efficiency the scene was recorded employing a photographic objective covered with a horizontal slit and it was projected by reversing the light path as in Komar's technique but enlarged and in white light. It was possible then to have an image on a 0,84 m x 1,10 m screen (20) at x40 enlargement (Figure 6).

The observer's space depends vertically on the height of the diffuser and laterally on its width and on the screen dispersion. The angle between the object and the reference beams being of 45 degrees, no more than four observers seated in two rows can see the scene simultaneously. A similar system not enlarging holograms but projecting pictures of classic movies was presented to the public (21). There, the images appeared from six meters behind the screen coming closer little by little until traversing it to one meter from the observer, located two meters away from the screen.

The recording and white light projection of holographic movies was not accomplished due to the lack of resources and concentration of efforts in the application of electronic images. The recording of holograms in white light which is based on an interesting proposal (22) was not accomplished up to now.
