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