Mechatronics, Industrial Control & Instrumentation

How Interferometers are used as Position Sensors

Interferometer sensors employ energy in the form of light or sound to make precise position/location measurements. There are a number of applications where accurate measurement of very small linear mechanical displacements and distances between objects in the order of nanometers is required, for instances the measurement of deflections of diaphragms and cantilevers in force, acceleration and pressure sensors, and thickness measurements in the microfabrication of LSI circuit chips and nanomachines. The measurement of small distances without contact can be made using optical interferometry.  An interferometer basically compares the phase between a reference light beam and a measurement beam by using the phenomena of constructive and destructive interference which occurs when two, coherent, light wave beams are summed on a surface, or a photodetector.

Basic Principle of Working of an Interferometer

The transmitted wave interacts with the reflected wave. If the peaks of the two waveforms coincide, the resultant waveform is twice the original. If the reflected wave is 180 degrees out of phase with the transmitted wave, the resultant combined waveform has zero amplitude. Between these two extremes, the combined waveforms result in a waveform that is still sinusoidal, but has amplitude somewhere between zero and twice that outputted, and will be phase shifted by between 0 and 180 degrees.

The Principle of Interferometry
Fig: The Principle of Interferometry

This type of sensor can determine distance to a reflective surface within a fraction of a wavelength. Because some light has wavelengths in the region of 0.005 mm, this leads to a very fine precision as a matter of fact.

If laser light is used, the waveforms can travel longer distances without being reduced in energy by scattering.

Examples of interferometers include:

  • Michelson interferometer.
  • Fabry-Perot interferometer.
  • Mach-Zehnder interferometer.
  • Normarsky interferometer.
  • The Sagnac interferometer.
John Mulindi

John Mulindi is an Industrial Instrumentation and Control Professional with a wide range of experience in electrical and electronics, process measurement, control systems and automation. In free time he spends time reading, taking adventure walks and watching football.

Recent Posts

Charging Ahead: Ensuring Your Gear is Compatible with Electric Vehicles

Image source Pixabay Many drivers assume that transitioning to an EV is just about swapping…

12 hours ago

What is an Integrated Circuit (IC)?

Image source Pexels An integrated circuit (IC) is a circuit in which components such as…

3 days ago

The Problems Associated with Embedded Power Generation

Image source Pixabay The rate of the development of energy sources that are alternatives to…

2 weeks ago

The Power of Automation in Construction: How It Transforms Efficiency and Safety

Image by Pixabay Automation is transforming industries worldwide, and construction is no exception. Companies are…

3 weeks ago

LED Beacon Lights: What Does Each Colour Lens Mean?

A closeup shot of a warning lamp in the street at night, image by Freepik…

3 weeks ago

Impeller Flowmeters: Features, Installation Considerations & Uses

Impeller flowmeters at times referred to as paddlewheel meters are one of the frequently utilized…

3 weeks ago