Whoa

Very strong optical illusions based on color - although, I wonder what they look like to someone who's colorblind?

Pew Pew

The Physics of Space Battles

Pedantic note:  He says "In space, laser light will travel almost forever without dissipating from diffraction," which is not true at all.  Diffraction works just fine in a vacuum and a diffraction-limited beam (ie, one that is not limited by any engineering compromises in the optics, but only limited by the fundamental effect of light's wave-like propagation) will spread by an angle roughly equal to the beam diameter divided by the wavelength.  A green (lambda=0.5um) 5 cm diameter diffraction limited laser beam will have an angular spread of about 1/10000 radians, so at 10km it will be about a meter wide.  Ish.  Whether the beam is traveling in vacuum or air or glass doesn't really affect diffraction at all.

There would be less scattering and absorption by random particles and clouds and less refraction by turbulence cells and inversion-layers, etc, ie, things that really do bother current atmospheric propagation of high-intensity laser beams (and stars, that's why they twinkle).  That might be what he meant, but that's not what he said.

Gallery of Sawn-I-Half Cameras

As promised, the Gallery of Sawn-In-Half Cameras

heh

[via]

When the moon hits your eye

How powerful a laser would it take to produce a visible spot on the moon? (Answer: close to 1.21 GW. CW!) (nb, The Tick could not be reached for comment)

World's smallest questionnaire

Olympus sends out microscopic questionnaire. Well played, marketing guys, well played.

Beautiful Specimens

Check out these old slides; Fantastic!

Lessons in Optics

Parabolic glass buildings are hot.

Easter Eggs

Molecular Expressions: The Silicon Zoo: Runaway Train

Noise is the Medium and the Message

I was in Lenox, MA for a few days to give a talk at a MURI workshop. Aside from the lovely New England countryside, which on Tuesday and Wednesday looked just like the photo above, I got to see a talk about single pixel cameras using compressive imaging with L1 norm reconstruction. This is all based on the work of Terry Tau and Emmanuel Candes. Tau is the the youngest guy ever to win a Fields Medal. Apparently he's quite smrt.

So Whitaker-Shannon says that you can perfectly reconstruct a Nyquist sampled-bandwidth limited signal. Okay, everyone knows that, but it turns out Shannon was way too pessimistic - almost nothing is band-limited; Almost everything is sparse, which is to say that the entropy of the universe is low. Anyone who reads blogs knows that. And if it doesn't seem so now, everything is sparse in the right set of basis functions, and for nearly everything the right set of basis-functions turns out to be noise. Weird.

To apply this to imaging, take some binary noise and line it up into a grid; it would look like an empty cross-word puzzle. Take a same-sized image, like the one above, and multiply them together, pixel by pixel, so that you get an image where half the pixels have been set to zero. Then add up all their values into a single number. Write that down. Then start over with a new noise pattern, which is your second basis function, and turn the image into a second number by projecting it onto the basis function. For an image with N pixels, do this about K=(0.05 to 0.20)*N times. Send your friend the K values, and he can asymmptotically reconstruct the image with 99% fidelity using The Magic of the L1 Norm (you can get MATLAB code there if you want to play yourself). At this point, all I can say is that it's magic, but the fundamental insight is that things are sparse, and so there going to be room to maneuver here. The signal is almost never pathological.

The great thing is that you can turn brute force O(n^3) problems into ~O(n log n) problems; A savings of nearly n^2. In an age of cheap CCD cameras, the imaging application turns out to be useful for imaging in non-visible wavelengths, like IR, Gamma Ray, and THz, where silicon doesn't do you a lot of good. Or perhaps you want to take gigapixel+ images using megapixel camera.

This turns out to be similar to one-time pad code-breaking. The low entropy of secret messages induces statistical similarities into the encrypted message.

Anyway, very cool.

Distance from Earth

The Universe: It's a big place. I wonder about the Doppler-shift velocity measurements because of the Wolf effect. Things like inflation, dark matter, and time-varying Universal constants seem ad hoc, and so I am curious if something about the base assumptions going into the measurements is wrong.

Why yes, I do realize that no one cares, but...

I love how I get way more traffic during the weeks when I post nothing than I do when I update, like, every five minutes. I know, it's navel gazing in the extreme, but I suspect that not posting lends the blog a certain air of mystery or something, ie, the stink of desperation reeks less.

I'm getting ready for my final dissertation defense, and I couldn't sleep last night because of that stress (mostly). My slides still need a lot of "polishing." If you want to come, it's this Friday, somewhere in the University's Computer Science building, sometime around 3pm. At this point, I just want to take my dissertation out back behind the barn and shoot it.

Finally, on the long and wearifying drive up to Rochester from DC, there was a lot - and I mean a lot - of lightning. Wrath of God lightning. Sound promising to you?

PS, under the category of way too much information that I am not comfortable with and need to outlet, I am sitting in the foyer of my cheapo hotel here using their WiFi, but some woman is having a very, very good time on the other side of a completely not soundproof door. I'd tell them to get a room, but they already did. Dammit.

But they're done now, so there goes that 2:20 episode of bliss.

DIY $1 Microscope

Excellent write-up on how to make a simple microscope. (via Make) This would be perfect for a grade-school science project, although explaining the optics might be a little out of their ken.

If you want higher quality optics, generic microscope objectives are easy to find on eBay for a few dollars plus shipping.

NB: Magnification is not the same as resolution. A low resolution image can be made large without increasing the fine detail that can be seen. The resolution of an objective is spec'd by the numerical aperture (NA).

New toy

More details once I've something more to say than "It Rules." BTW and FYI, people will look at you funny if you pull out a camera in a bathroom. Trust me pard, do this solo. Also, I have large hands.

Still life at the Institute of Optics eleventy-billion

"Well, it's about the size of a Skoal can."
- Wade Cook, former denizen of Tennessee, describing a light source.

Thesis update

You shouldn't care, but just in case: I estimate I am this close to done:

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Earlier, I said I was posting here as a way to divert the dross from entering my refined thesis prose. Said dross is now being shoveled directly into the thesis. I've really had it up to here with dyadic Green's functions, tip-particle plasmon resonances, intraband metal photoluminescence, ultrafast nonlinear optics, and single molecule and quantum dot fluorescence and absorption imaging of either the far field or near-field variety. Mothers, don't let your kids grow up to be grad students. Seriously, it's totally not worth it.

Still life at the Institute of Optics 10

"Our carpet was supposedly cleaned - but there's cleaning the carpet, and then there's getting the carpet wet and pushing the dirt around." - Proffesor Robert Boyd

Still life at the Institute of Optics 9

Kevin Charles: "Ah! A Fourier transform. We can do these because we're optics bad asses!"
Jason Puth: "No, not really. If we were a biker gang, I would be the guy in the little sidecar."

Still life at the Institute of Optics 8

"Again, the elegant method of solution here will turn out to be guessing." – Lee Casperson

Still life at the Institute of Optics 7

"I think we should all buy boxes of Crisco and do reports on how quickly it yellows." – Russell Gehr