Far-Distance Moiré device

Displacement and vibration measurement with the Moiré technique

By superposing two Ronchi gratings with close pitches, a new periodic pattern, i.e., the so-called Moiré fringes, is generated with much greater pitch. The advantage of the Moiré fringes is its magnification compared to the constructing gratings pitch. Furthermore, it has a great sensitivity to movement and rotation of the primary gratings which leads to precise measurements.

Device Specification & Advantages (customizable)

  • Far-distance and nondestructive measurement
  • Financially beneficial compared similar measurement devices
  • User-friendly Software based on R Programming languages
  • Simple physical method
  • Uncomplicated elements
  • Optics simplicity
  • Conventional optical/mechanical/electronic elements
  • Fast results achieving
  • Distance from target: up to 200 m (customizable)
  • Focal length ∼1 m
  • Exit pupil diameter ∼ 20 m
  • First and second Grating with pitches ∼ 3 mm & 50 μm
  • CCD Sensor with 750 frame 750 frame/s , and Nyquist frequency ∼ (10-4_375)Hz 44444
  • 20 μm Displacement Precision from 76 m and 40 µm precision from ∼100 m
  • 6 m field of view from 80 m

Application of FDMM Device:

  • Displacement Measurements (Megastructures, buildings, Earth – Faults, compressors …)
  • Measurement of Structures vibration, structures damping and vibration modes
  • Vertical nodes displacement measurement
  • Sub-degree (mili degree) angle measurement
  • Measurement of atmospheric turbulence
  • Temperature profile measurement
  • Structure’s stress-strain measurements
  • Landslide measurement in geology application



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