Digital Holograms
Another recent development in display holography is the digital computer-generated hologram. It is possible to produce large colour holograms using this new technique. A special printer is required to print the images pixel by pixel on a holographic film. These holograms can be up to 1.2 by 1 m in sized and can be tiled to cover large areas.
There are two ways of producing them.
• Direct recording with a HD colour digital camera recording a scene along a horizontal axis, a static or animated sequence.
• Completely computer-generated 3-D visualization, static or animated.
As mentioned above a hologram may be produced from a series of two-dimensional pictures. These may come from video, computer graphics, artwork, and photography, or can even be hand drawn animation.
If the initial images are made in the correct way, the resulting holographic image can be three-dimensional. Alternatively the images may be animated and appear to move as the view changes from side to side or from top to bottom. A combination of 3D and movement is also possible. This effectively creates a "holo- graphic movie." There is a technical limitation to the number of frames from which the hologram is made. The maximum is about 60 frames. This creates a small piece of animation. An example would be a footballer scoring a goal.
One of the advantages of this type of holography is that images can be appropriated from existing sources such as video and film archives. If the right sequence is chosen, very effective holograms can be made, for example of people who are no longer alive.
Moving holograms can be one-offs or mass reproduced. With the advent of inexpensive digital video, supplying a hologram manufacturer with images suitable for hologram production directly from video or video/computer graphic combinations is no longer an expensive or time consuming process. The Tagged Image File Format (TIFF) is generally considered the most versatile format and most hologram makers use this as a standard. Images can be created using any operating system such as Mac, Windows, SGI etc.
