3D-printed Michelson interferometer delivers precision measurements on a shoestring budget

A Michelson interferometer manufactured using 3D printing shows how sophisticated optical measurement technology can be achieved using simple means. The design was developed by Guillermo Angeris, who documents and explains the project in a detailed blog post. The aim was to create a functional optical measuring device with a minimal budget and predominantly additively manufactured components.

A Michelson interferometer is used to measure very small changes in the optical path length. To do this, a laser beam is split into two beams at a beam splitter. Each beam is reflected by a mirror before both are recombined. Differences in the path length result in interference patterns that are visible as bright and dark stripes. Even minor effects, such as temperature changes in the air in the beam path, can cause measurable shifts in these patterns.

Angeris considers the interferometer to be a suitable experiment for combining mechanical precision, adjustability, and additive manufacturing. Although the design requires tight tolerances, he believes these are within the capabilities of today’s desktop 3D printers. The central design feature is the mirror holders. They must be stable and at the same time allow for fine alignment.

The solution consists of kinematic mirror holders with three adjustment screws, nuts, and tension springs. The screws define the position of the mirror via three support points, while the springs constantly pull the mirror against these points. Other assemblies such as the laser holder, beam splitter mount, and projection surface can be printed directly. The mirror and beam splitter themselves are not additively manufactured.

According to the developer, the material requirement is around 50 grams of PLA. Printing is done without support structures and with moderate infill. In addition, a 650-nanometer diode laser, two simple mirrors, and standard hardware are required. Angeris estimates the cost of the mechanical and electrical parts at around three US dollars. The beam splitter increases the total price to around 20 US dollars.

Despite its simple design, the interferometer should be able to detect path length changes in the order of a laser wavelength of around 650 nanometers.