Integral 3-D Imaging Techniques

Integral Photography

After Lippmann had perfected his colour process, he began work on techniques for recording 3-D photographs that could be viewed without any optical viewing devices. In 1908 he presented his integral photography (I/P) in which an array of small closely spaced spherical lenses (a fly’s-eye array) is used to photograph a scene, recording images of the scene as it appears from many different horizontal and vertical locations (Lippmann,1908a & b) (see Figure 1). The recorded microlens photograph is then reversal processed, generating a positive image. When this is viewed mounted behind a similar array of lenses, a single integrated image composed of small portions of all the images is seen by each eye. The photograph presents different images to the left and right eye respectively, thus creating the 3-D effect, the position of each eye determining which parts of the small images it sees. The overall effect is that the visual geometry of the original scene is reconstructed so that the limits of the array seem to be the edges of a window through which the scene appears, realistically exhibiting both vertical and horizontal parallax and perspective shift with any change in the position of the observer. Thus all the microimages are combined into a single 3-D image.

Integral photography is based on a principle known as the lens sampling effect. To achieve this effect, the thickness of the lens array sheet is chosen so that incoming light rays focus on the opposite (flat) side of the sheet, at which plane the microimages are recorded on a single film sheet. It is possible to utilise arrays of pinhole apertures in an opaque plate instead of the microlenses. A pinhole behaves like a lens, but depends on the rectilinear propagation of light rather than on focusing by refraction. The radius of the pinholes is selected to provide the best compromise between the effects of geometrical spreading and diffraction. However, when the pinhole array is used as a viewing screen, the radius needs to be much larger; otherwise the image will be too dark to view with normal illumination.

Figure 1.

Fly’s-eye lens array

Figure 3.

Viewing an integral photograph with an inverted-perspective image