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DMI Distance Measurement Technology

The Basics

DMI --> Distance Measurement Interferometer

Sensing Technology: Infrared Low-Coherence Interferometry (Time Domain mode) 


Measurements: Surface position, center thickness and air gap of all optical elements (lenses, cubes, flats, etc.) of an assembly along the optical axis. 

How does it work?

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  1. Light emitted by an infrared Super Luminous Diode (λ = 1.3µm) is coupled into a monomode optical fiber

  2. The light is split between the measurement arm and the reference arm

  3. The light coming back from both arms is focused onto a photodetector

  4. When the optical path lengths of the measurement arm and the reference arm are equal, interference is visible on the photodetector

  5. High stability mechanics, specific calibration procedure, usage of internal thermal probe and precise encoder index computation enable high accuracy

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