The following documents an approach to creating stereoscopic photographs and video of small scale objects, for example, live insects. The trick is achieving the small camera separation which is proportional to the size of the object being photographed. In order to take stereoscopic photographs of an object on the scale of a cm, one needs a camera separation on the order of 1/2mm, or less. While this can be achieved for stationary objects with a single camera offset at two different times, this approach is not acceptable for moving objects.
The solution here is to use a beamsplitter to essentially fold the light path for one camera. The cameras are now at right angles to each other and the view frustums can be moved arbitrarily close to each other. A technique is also required to capture the images at the same time, in this case the LANC interface supported by older Sony cameras is used. A stereo LANC controller provides synchronised images within 3 or 4 ms. Unfortunately as of 2009 Sony seems to have discontinued this support in their current range of digital cameras, the solution would seem to reside with Canon cameras and the CHDK (Canon-hack development kit).
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The images above show the very basic prototype: two cameras, beamsplitter at 45 degrees, lanc controller, cover to ensure the second camera only receives light reflected from the beamsplitter.
Notes
The beamsplitter is 50% symmetric transmission/refection, other ratios exist and would clearly result in unmatched intensities between the stereo pairs.
Cameras with good macro lens support are obviously desirable.