Archive for September, 2014

Optical Shenanigans

Wednesday, September 24th, 2014

When I was in my third year at the North Avenue Trade School, I finally escaped from the core curriculum courses, and began taking classes in Physics, my declared major. One of my early physics courses was an optics class, which had an associated hands-on lab component.

My roommate at the time was Robert S., a fellow Physics major who was not only taking the class with me, but also spent his co-op quarters in the bowels of the Central Intelligence Agency. I assume he was in the bowels; he never explicitly mentioned his work setting. And, for some reason, I had decided that it would be not be polite for me to ask Robert about his work, which required a security clearance. It would have been sorta awkward if he had to kill his roommate, not to mention the paperwork.

But I managed to get a pretty good idea of some of the things he was working on, simply by observing what he already knew how to do in our optics lab. I’m pretty sure he didn’t learn those tricks in south Georgia.

One of our primary lab projects was an experiment with spatial filtering. Spatial filtering allows an optical image to be modified to enhance aspects of the image (edges, for example) by physically obscuring components of the image. It seemed a little like magic, but it eventually came down to frequency distribution, which is why you can hear the bass from your loud neighbor’s music, but not the cymbals. That, and Fourier transforms.

The professor, whose name escapes me, asked each student to write his own lab report, even though we were working in pairs. Fortified with the over-zealous wisdom that only a third-year college student can muster, I decided that making each of us write separate reports was, well, dumb. So for our mid-quarter assignment, as a not-so-subtle form of protest, I turned in a report that was frankly awful. A terse page, consisting mostly of our numerical results.

And my prof let me know how awful it was, in no uncertain terms. His words were something on the order of, “If you ever turn in anything that shoddy again, I will flunk you, not just in the lab, but also in the class.”

He got my attention. It was a well-timed correction for my college experience, and a useful learning experience.

When the end of the quarter came around, I took my spatial filtering lab report seriously. I found that I could enjoy technical writing as much as I did English composition. I drew elegantly concise diagrams explaining the experiment, and formulas showing what I understood of the math.

At least that’s the way I remember now, with the caveat that our memories change as we re-tell our stories. I do know that I received an “A” for the report, and passed the optics class.

Leaf shadows with light grid pattern

Boots, bowed legs, and odd shadows

Wandering around campus a few years later (it took me years to escape), I bumped into one of the physics lab technicians that I had become friends with. He told me that they were still using my lab report as an explanatory handout for the project.

When I noticed this odd pattern of shadows on a recent early morning walk from bus stop to office, those optics lab experiences came flooding back, eventually reminding me of what I had really learned: precise writing is important and useful. That lesson continues to guide my technical writing, even to this day.

That same morning, I posted the leaf picture on Instagram, and my good friend Craig L. (artist, inventor, and deep thinker) commented, accurately, “Space between leaves makes a pinhole lens – an image of the lights. Saw this in 84 as infinite half-moons during a *partial solar eclipse.”

I took a closer look at the lights a few days later. Each street light consists of two four-by-four arrays of light-emitting diodes (LEDs), 32 in all, bright white in the city night. Each LED acts as a “point source”, producing the grid effect that I saw on the ground, and that Craig described.

As for spatial filtering, the functions Robert and I were experimenting with have been replaced by computer algorithms, many of which quietly do their work in your smart phone when you tweak a snapshot before posting it. The primary use for spatial filtering today is to improve the purity of a laser beam. Which is still pretty cool, because of my previously noted affinity for coherent light.

By the way, if you need any advice on technical writing, or just want someone to proofread or edit your stuff, I’ll be glad to give you a hand. Or an eye, I guess.