Shufflebrain

Leith had worked on sophisticated radar, was a mathematical thinker, and thoroughly understood waves; and in 1955 he had become intrigued by the hologram. Upatnieks was a bench wizard, the kind of person who when you let him loose in a laboratory makes the impossible experiment work.

Gabor's so-called "in-line" method (because object lies between plate and source) put several restrictions on optical holograms. For instance, the object had to be transparent. This posed the problem of what to do about dense objects. Besides, we actually see most things in reflected light. Leith and Upatnieks applied an elaborate version of Fresnel's old trick: they used mirrors. Mirrors allowed them to invent "off-line" holograms, and to use reflected light. The light came from a point source. The beam passed through a special partially coated mirror, which produced two beams from the original; and other mirrors deflected the two beams along different paths. One beam, aimed at the object, supplied the object waves. The other beam furnished the reference waves. They by-passed the scene but intersected and interfered with the reflected object waves at the hologram plate.

Leith and Upatnieks used a narrow beam from an arc lamp to make their early holograms. But there was a problem. The holographed scene was still very small. To make holograms interesting, they needed a broad, diffuse light. But with ordinary light, a broad beam wouldn't be coherent.

So Leith and Upatnieks turned to the laser. The laser had been invented in 1960, shortly before Leith and Upatnieks tooled up to work on holograms. The laser is a source of extremely coherent light, not because it disobeys the uncertainty principle but because each burst of light involves a twin emission--two wave trains of identical phase and amplitude.

The insight Leigh and Upatnieks brought to their work was profound. Back when holograms were very new, I had seen physicists wince at what Leith and Upatnieks did to advance their work. What they did was put a diffuser on the laser light source. A diffuser scatters light, which would seem to throw the waves into random cadence and total incoherence. Leith's theoretical insight said otherwise: the diffuser would add another order of complexity to the changes in the phase spectrum but would not cancel the coherent phase relationship between object and reference waves. Not if he was right, anyway! And Leith and Upatnieks went on to make a

diffuse-light hologram

, in spite of all the conventional reasons why it couldn't be done.

***

Gabor had tried to make his object act like a single point source. The encoded message spread out over the medium. But each point in the scene illuminated by diffuse light acts as though it is a source in itself; and the consequence of all points acting as light sources is truly startling. Each point in the hologram plate ends up with the phase and amplitude warp of every point in the scene, which is the same as saying that every part of the exposed plate contains a complete record of the entire object. This may sound preposterous. Therefore, let me repeat: Each point within a diffuse hologram bears a complete code for the entire scene. If that seems strange, consider something else Leith and Upatneiks found: "The plate can be broken down into small fragments, and each piece will reconstruct the entire object."[9]

How can this be? We'll have to defer the complete answer until later. But recall the sizeless nature of relative phase, of angles and degrees. The uncanny character of the diffuse hologram follows from the relative nature of phase information. In theory, a hologram's codes may be of any size, ranging from the proportions of a geometric point up to the magnitude of the entire universe.[10]

Leith and Upatnieks found that as fragments of holograms became small, "resolution is, of course, lost, since the hologram constitutes the limiting aperture of the imaging process."[11] They were saying that tiny pieces of a hologram will only accommodate a narrow beam of decoding light. As any signal carrier becomes very tiny, and thus very weak, "noise" erodes the image. But vibrations, chatter, static, snow--noise--have to do with the carrier, not the stored message, which is total at every point in the diffuse hologram. Even the blurred image, reconstructed from the tiny chip, is still an image of the whole scene.

Not a word about mind or brain appeared in Leith and Upatnieks's articles. But to anyone even remotely familiar with Karl Lashley's work, their descriptions had a very familiar ring. Indeed, substitute the term

brain

for

diffuse hologram