hobby #180

Thermal Expansion Interferometry

Using optical interference fringes to measure sub-micron dimensional changes in materials as they heat or cool. A Michelson or Fizeau interferometer splits coherent light into two paths—one reflecting off the test specimen, one off a stable reference—and the fringe pattern shift reveals expansion measured in wavelengths of light (sodium D-line: 589 nm). Quantifies thermal expansion coefficients, verifies dimensional stability in precision tooling, and explains why the diffraction grating ruling engine fails when shop temperature drifts 2°C.

Jun 30 8:49 PM #180 6 min

Twenty-Three Where Fifty-Three Appeared

Thermal Expansion Interferometry

Counted fringes to nanometre precision. Aluminum's expansion coefficient: 53 where it should be 23. The bench was expanding too.

scienceopticsmeasurementengineeringphysics