An interferometer sounds like something complicated, and in a way, it is. But it is also pretty easy to build one with some common materials. [Let’s Innovate] has instructions for how to make an interferometer using a green laser pointer, some mirrors, and a CD case. one of the most mundane parts, though, might be the most important: Play Dough.
The very sensitive device needs very precise alignment of the mirrors that reflect the beam. Using Play Dough it is easy to adjust the mirrors to the spot that is just right and then have it stay there.
For the best result, the mirrors really need to be first surface mirrors and not the more common kind with the reflective part on the back. Apparently, a green laser gives better results than a red one, too. If you don’t want to hack up a CD jewel case, a DVD player may give up a beam splitter.
So what do you use it for? Well, most of us use it to see the pretty patterns. But the instrument actually has wide-ranging applications to measure very small distances in fields as diverse as astronomy, optics, and photomicroscopy. To do anything really practical, you might need to add a detector of some sort.
If you want a more robust build, this one is similar. If you have a well-stocked test bench, you might be able to get by with even less.
[Calango] is a railway technician, and for a school final project created the Rail Wear Surveillance Trolley (RWST) which is a delightfully designed device made mainly from PVC conduit with one job: travel down a segment of train track while shining a green laser onto the rail, and capture camera images. The trolley holds both the laser and the camera at just the right angles for the camera to capture a profile of the rail’s curved surface. The images are sent via Bluetooth to a smartphone for later analysis. Rail wear can be judged by checking how well the profile of the rail conforms to the ideal profile of an unworn segment. The trolley is manually pushed by an operator, but [Calango] says that ideally, it would be self-propelled and able to inspect a length of the track then return on its own.
The project was made on a tight budget, which led to some clever solutions like using a rotary encoder attached to a wheel as a makeshift distance sensor. If things get desperate enough, it’s even possible to roll your own rotary encoder with a 3D printer and two microswitches.
The news is awash about a 17 year old girl who won a $100,000 scholarship for her spectrograph, but nobody actually linked to information about the thing. After some digging around, I located [Mary]’s web site. It’s a work in progress, but I found an early version of her spectrograph build. The picture shows her project with a spectrograph head made for a meade telescope. Hopefully she’ll get documentation of her spectrograph head up soon. This is one of the better uses I’ve seen for a 5mw green laser.
I forgot to mention her sweet dobsonian telescope build. Very nice work.