Full-Field Vibrometry - A Complete Guide

The Hitchhikers Guide to Full-Field Laser Vibrometry

Overview

Full‑field laser vibrometry is a non‑contact optical measurement technique that captures vibration, deformation, and mode shapes across an entire surface simultaneously. Unlike scanning vibrometers, which measure one point at a time, full‑field systems acquire complete spatial information in real time — enabling rapid, high‑resolution analysis of mechanical structures, composites, and micro‑devices.

This guide explains the principles, instrumentation, applications, and advantages of full‑field vibrometry, with a focus on interferometric imaging systems such as Optonor’s VibroMap.

What Is Full‑Field Laser Vibrometry?

Full‑field vibrometry measures the out‑of‑plane vibration of a surface by recording optical phase changes across a camera sensor. Each pixel acts as an independent interferometric detector, producing a dense vibration map.

Key characteristics:

Non‑contact
Real‑time measurement
High spatial resolution
High‑frequency capability
Full‑surface mode shape visualization

This makes it ideal for structures where scanning is too slow, too coarse, or physically impractical.

How It Works (Measurement Principle)

Full‑field vibrometry is based on interferometry, where a coherent laser beam is split into a reference beam and an object beam. When the object vibrates, the reflected light experiences a phase shift proportional to displacement.

Measurement workflow:

Illumination A laser illuminates the surface.
Interference formation Reflected light interferes with a reference beam, creating a phase‑encoded pattern.
Imaging A high‑resolution camera captures the interference pattern.
Phase extraction Algorithms compute phase changes for each pixel.
Vibration reconstruction Displacement, velocity, and mode shapes are derived from the phase data.

Why this matters:
Because every pixel measures simultaneously, the system captures complete mode shapes in a single acquisition, even at high frequencies.

Full‑Field vs Scanning Vibrometry

Feature	Full‑Field Vibrometry	Laser-Doppler Vibrometry
Measurement speed	Real‑time	Slow (point‑by‑point)
Spatial resolution	High (camera‑limited)	Moderate
Frequency range	DC to high‑MHz	Typically kHz–MHz
Mode shape capture	Instant	Requires full scan
Sensitivity to motion	Low	High
Best for	Composites, MEMS, complex geometries	Simple structures

Full‑field vibrometry is the superior method when:

The structure has many modes
The geometry is complex
The object cannot remain perfectly still
High‑frequency behavior is important
Time‑to‑result matters

System Components

A typical full‑field vibrometry system includes:

Laser source

Coherent illumination
Wavelength stability
Suitable power for diffuse or specular surfaces

Interferometric optics

Beam splitters
Reference arm
Imaging optics

High‑speed camera

High dynamic range
High frame rate
Low noise

Object excitation

Piezo actuators
Shakers
Acoustic excitation
Thermal load
Vacuum load

Processing software

Phase extraction
Frequency analysis
Mode shape visualization
Export and reporting tools

What Full Field Vibrometry Measures

1. Displacement
Absolute or relative out‑of‑plane motion.

2. Velocity
Derived from phase rate of change.

3. Mode shapes
Spatial vibration patterns across the surface.

4. Resonance frequencies
Natural frequencies of the structure.

5. Damping characteristics
Energy loss per cycle.

6. Defects and anomalies
Changes in stiffness or mass distribution.

Advantages of Full Field Vibrometry

1. Real‑time mode shapes

Instant visualization without scanning.

2. High spatial resolution

Limited only by camera pixel count.

Ultra-high‑frequency capability

Suitable for MEMS and micro‑devices.

4. Non‑contact and non‑destructive

No mass loading or mechanical interference.

5. Robust to environmental motion

No need for perfect isolation.

6. Fast measurement cycles

Ideal for production, QA, and iterative R&D.

Applications

Aerospace and Composites

Delamination detection
Impact damage assessment
Quality control of composite panels
Modal analysis of lightweight structures

Mechanical Components

Resonance identification
Structural optimization
Fatigue analysis
Noise and vibration troubleshooting

MEMS and Microstructures

Mode shape visualization
Packaging effects
High‑frequency behavior
Device characterization

R&D and Material Science

Experimental modal analysis
Validation of simulation models
Material property studies

Non-Destructive Testing

Delamination detection
Impact damage assessment
Quality control of composite panels
Modal analysis of lightweight structures

Typical Workflow - Deterministic and Repeatable

1. Mount the object
2. Illuminate with laser
3. Adjust focus and reference beam
4. Apply excitation
5. Acquire interferometric images
6. Extract phase and compute vibration data
7. Visualize mode shapes
8. Export results

Example Use cases

Composite Panel with Impact Damage

Full‑field vibrometry reveals local stiffness changes as distortions in mode shapes.

MEMS Resonator

High‑frequency mode shapes captured in real time for design validation.

Automotive Component

Identification of unwanted resonances contributing to noise or vibration.

Why Full Field Vibrometry Matters

As structures become lighter, more complex, and more integrated, traditional point‑based measurement methods struggle to keep up. Full‑field vibrometry provides the spatial and temporal resolution needed to understand modern materials and devices.

It is rapidly becoming a preferred method for composite inspection, MEMS characterization, lightweight structural analysis and high‑frequency vibration research.