atomic_fungus (atomic_fungus) wrote,

#3010: Thursday: cold, wet, rainy.

Friday's supposed to be sunny and dry. I might take the motorcycle out to run errands tomorrow, if I can. There won't be many more days this year I can do that, unless I go buy some cold weather riding gear.

* * *

Ann Coulter on OWS. I've seen one source claiming that the OWS gits are not pure socialists (Karl Denninger) and the rest of the sources have been showing them as being nothing but.

* * *

Oleg Volk has a link to something very important:

TSA checkpoints on Tennesee highways.

In other words: TSA is now stopping traffic and searching vehicles.

...when the Department of Homeland Security was first announced, I had a dream that I and some friends were on the run from "Office of Homeland Security" troopers. Like enemies of the state on the run from Gestapo or NKVD. Looks like that's getting ever closer to becoming a reality, and it sucks.

* * *

I want to understand how this works.

If I understand the Sunday-supplement-level discussion at the link labeled "the Science Inside", this thing actually captures a holographic image: it detects the the wave information (rather than just recording the number and energy of photons, the way a conventional camera does) and can reconstruct it according to the user's wishes.

In a 2D output mode the user can choose where the image is focused; but this technique lends itself to capturing 3D images because that's how it does things to begin with anyway. Like a hologram made with a laser but with white light. (How one reconstructs that image in 3D using white light without special glasses, screens, or what-have-you is left to the student.)

I'm trying to figure out how to explain it in more concise terms, and failing. I've grasped how the thing does what it does, and I know there's an easy way to explain it, but I'm too tired right now to manage it.

A conventional camera just records the number of photons striking a particular point. The energy of the photons determines color, so if you have nine red photons and a dozen blue ones striking a particular pixel it turns out to be purple of a certain intensity. Right next to it you might have twenty green ones and five red ones, making a weird orange color. And so on, across a million pixels arranged in a 2D plane. What you end up with is a reflection of a certain plane outside the camera--the object of the focal plane inside the camera. Because all you're really doing is counting photons and adding up their energies, you end up storing only the information which is specific to that particular 2D plane. You don't capture any other information except an instantaneous view of how many photons were passing through that particular plane at the instant the camera's shutter was open.

This works very well for capturing a 2D image, and you can do a lot of interesting things with this level of technology.

But there's much more information carried by light than just the number of photons that bounced off something, and their energies. A photon explores all possible paths between its source and its sink.

Assume a particular photon, emitted by the sun, hits a flower and is absorbed by a particular atom in that flower. An electron jumps to a higher energy level in that atom; after a few moments it drops back and emits a photon that corresponds to the change in energy levels. This photon has been emitted by the atom (source) and is absorbed by a cell in your eye's retina a few nanoseconds later. Your eye is the sink, the absorber, of the photon.

Now: the photon exhibits the weird wave/particle duality that all quantum objects do; if you think of it purely as a wave, then it's easier to see how it can explore all the possible paths between source (atom) and sink (eye). The wave is an electromagnetic field, moving from source to sink at the speed of light, spreading out like ripples on a pond.

A hologram captures this information; it's essentially a recording of the interference pattern that results when two waves intersect. This camera does the same thing: it captures each wave (rather than capturing only each particle, which is how conventional photography works) by recording how those waves interfere with each other.

That's about as good as that explanation is going to get right now. I can barely keep my eyes open; I only hope it's coherent enough to make sense.

* * *

I've been up since about 1:30 AM, after sleeping from perhaps 9:30-ish until then. I need to get some more sleep now.

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