Holographic Stereograms

Unlike a laser hologram a holographic stereogram does not record a portrait directly but utilises a combination of holographic and conventional 3D stereo photographic techniques to produce the final three-dimensional portrait image. A holographic stereogram is in essence a holographic viewing device for a sequence of stereo-photographs. These stereo-photographs are shot using a digital video camera system called the VIP system (Video Images with Parallax) which has been specially developed by Spatial Imaging. To record the sequence of digital stereo-photographs a computer controlled camera is moved past the person on a 2 metre long track. As it moves the camera captures up to 400 images from many different points of view. The VIP system is portable and thus stereo sequences can be recorded at any location. Once a sequence of stereo-photographs has been recorded a holographic stereogram is made at Spatial's studios. As with white light reflection holograms the portrait image straddles the holographic plate i.e. part of the portrait projects in front of the stereogram and part lies behind. Holographic stereograms are true colour 'rainbow' holograms. As with the commercial holograms found on credit cards however the colours change when the stereogram is tilted. The stereogram only displays a correctly coloured image from a particular angle. Ordinarily this is not a problem as a viewer will naturally adjust his or her position until the correct colour is seen. Spatial's holographic stereograms are made on a reflective material, either mirrored glass or solid metal, and front illuminated. In both instances a conventional low voltage spot light can be used to illuminate the holographic stereogram.

Advantages:

• Animation is possible i.e. any movement by the sitter when the photographs are taken will be seen in the holographic stereogram.
• The portrait is in real colour from a particular vertical viewing angle.
• The portrait can project forward and relatively deep images can be recorded in sharp focus.
• The sitter does not need to travel to our studio in Richmond and can be recorded at any venue or outside on location.
• The subject matter does not have to be life sized i.e. the portrait can appear reduced in size. Several sitters within a scene can be recorded at the same time.
• Front lit holographic stereograms are simple to display.

Disadvantages:

• Holographic stereograms do not give in an image which is as realistic as directly recorded laser holograms.
• Holographic stereograms only display horizontal parallax i.e. they have side to side look around only.