In 1966, I may have accidentally discovered a new optical effect. But for 60 years, I’ve been unsure. Until now.
I noticed the phenomenon on my own, in my dorm room.
The next day, I was sitting in a classroom with a youngish professor, probably of assistant professor rank. I liked both him, and optical physics.
The professor had been lecturing in one of the oldest buildings on the Georgia Tech campus. The wood in the lecture room looked ancient, and smelled like a combination of student sweat and Georgia pine paneling. The room was small, built for a time when class sizes were much smaller, and long before air conditioning. It had been built mostly for engineering students. Not physics students.
For fifty minutes the professor filled the chalkboard with diagrams and equations. When the class time was up, students left hurriedly, heading to their next class. But I lingered.
While the professor was turned away from me, erasing his work from the board, I caught his attention. I told him what I had done and seen in my dorm room.
At first, he said nothing. I assumed he would eventually remember some obscure fact of optics that applied. But all I got was a blank stare followed by shrugged shoulders. He was stumped.
I am badly myopic, with 20/400+ vision. Fortunately, with the correct lenses, my vision was correctable to 20/20. The only upside to needing glasses is that, with them off, I can examine small objects up close. I call it “microscopic vision.”
But it’s not really microscopic vision.
However, what I saw in my dorm room, surely looked like microscopic vision.
But that would be impossible. Wouldn’t it?
Inciting Incident
I used to run during cool summer nights in Kansas. That was when I noticed that if I looked at a bright white, round street light, without my glasses, I would see amazing patterns. The light itself and everything around me would be out of focus, but the complex patterns I could see in the image of the light were sharply defined.
The beautifully detailed, complex patterns a severely myopic person sees are caused by diffraction and interference of light as it passes through the imperfections within their own eyes. I did not know that then, but I do now.
Back in the mid-sixties, Tensor lamps made ideal study lamps. They weren’t cheap, but made ideal Christmas gifts for college students.
One evening, as I sat at the desk in my dorm room, I picked up a Bic pen, and as I looked at the pen to remove its cap, I noticed a light glare off the curved surface of the cap. The small but intense spot of light was from the Tensor light.
Experiment
The chain of thought that led to my next action would not be obvious to most people. But guided by the memory of the beautiful light patterns I had seen during my nighttime runs, I pulled off my glasses and stared at the reflected light spot as I slowly pulled that pen cap closer to my unaided and highly myopic eyeball.
What I saw was magical. It was a highly detailed image of the surface imperfections on the curved surface of that plastic pen cap.
To make sure I was not imagining things, I rummaged around in my messy desk drawer and found a straight pin. With that pin, I scratched the surface of the pen cap. Then I again pulled the cap to within a centimeter from my cornea.
I was looking at the Grand Canyon!
A sense of awe overtook me as I rotated and tilted the cap, mentally absorbing every detail of that chasm in plastic. I could scarcely believe what I was seeing.
Somehow, I had finally turned my eye into a microscope.
This had to be big news! I had seen the impossible.
After I gave up on the physics professor, I tried thinking of ways to industrialize and capitalize on my observation. All I needed was a large pool of myopic people sticking their almost-blind eyes danger-close to a conveyer belt of objects intended to be perfectly smooth.
Yeah, that would never happen.
After a few minutes of daydreaming, I returned to my studies.
But I never forgot about that event.
Revisitation
Recently, I pondered that event again. Since our set of Collier’s Encyclopedia was long ago contributed to a local library, I turned to the most convenient source of knowledge, the Internet.
ChatGPT told me I had essentially built a naked-eye deflectometer, converting microscopic slope changes into visible patterns. I was not actually focusing my eye on the pen-cap surface.
Well, my instincts were mostly correct. It was a microscope—without a conventional objective lens. And the image was an amplified version of the actual surface. Or at least a reasonable facsimile.
It sounds to me like we’re splitting hairs here.
So, I ask again. Is this a well-known phenomenon?
Well, not in the sense that it was, at the time, a familiar optical trick that every optics professor should immediately recognize. The underlying physics is now familiar to engineers, but my particular observation is unusual, or perhaps even unique.
For the past forty-five years optical engineers have routinely exploited the fact that tiny deformations in a glossy surface strongly distort a reflected highlight. The modern field is called deflectometry: rather than directly imaging a shiny surface, one observes how that surface redirects a reflected source or pattern. Slight changes in surface slope can become far more conspicuous than the physical defect itself.
A major review describes deflectometry as ranging from qualitative visual inspection to precision measurement of microscopic optical surfaces. Normally, deflectometry involves a camera, a screen or projected pattern, calibrated geometry, and computer reconstruction. And a price tag of thousands of dollars.
Unwittingly, I had replaced all of that with a lamp, a curved piece of plastic, a pupil and a highly myopic eyeball.
Sometimes, ignorance really is bliss.
Engineering History
The optical principle underlying specular-surface deflectometry can be traced at least to Léon Foucault’s 1858 knife-edge test of reflecting mirrors. The term “moiré deflectometry” appears explicitly in optical literature by 1981, in work by Oded Kafri and A. Livnat[1].
That was fifteen years after I reported my self-experimentation to a Georgia Tech professor. The earliest automated industrial-quality-control application I have located is Lippincott and Stark’s 1982 optical-digital method for detecting dents and scratches on specular metal surfaces[2]. Apparently, none of the above authors were from Georgia Tech.
It looks like a Georgia Tech professor missed an historic opportunity.
Summary
The physical laws that produced my observation are now well known. The naked-eye manifestation is unusual, non-obvious, and apparently not a commonly described phenomenon.
Sadly, no one will ever make a buck off my observation. But it’s worth my mentioning in this blog post, just in case some future physics student asks a physics professor about a strange optical phenomenon they observed.
Instead of responding with a blank stare, that professor could wisely nod their head and say, “There was once this student who accidentally discovered the principle of deflectometry. Let me tell you about it.”
You cannot imagine how satisfying it is to finally get to scratch the curious itch that had been bothering me for sixty years.
[1] Oded Kafri and A. Livnat, “Reflective Surface Analysis Using Moiré Deflectometry,” Applied Optics 20, no. 18 (September 15, 1981): 3098–3100.
[2] Hugh W. Lippincott and Henry Stark, “Optical–Digital Detection of Dents and Scratches on Specular Metal Surfaces,” Applied Optics 21, no. 16 (1982): 2875–2881.
