3D-Laser vibrometers

A 3D laser vibrometer captures vibrations in all three spatial directions. To achieve this, three laser beams measure the same point from different angles, enabling complete acquisition of both in-plane and out-of-plane motion.

This principle is used in both 3D scanning vibrometers and 3D single-point systems.

Three-axis vibration acquisition: Three laser beams measure the same point from different angles – the system automatically transforms the data into Cartesian coordinates (x, y, z).
In-plane and out-of-plane separation: Clean separation of the vibration components within the material plane and perpendicular to the surface.
Frequency range and measurement range: DC to 50 MHz with vibration velocities up to 50 m/s.
FEM validation: Import of 3D models (NASTRAN, STL, OBJ) and direct measurement on FEM nodes using the SMART Lab software.

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full body vibration measurement of a car in wind tunnel

3d vibration measurement with 3d-single-point vibrometer

A 3D laser vibrometer captures vibrations in all three spatial directions at a single measurement point. To achieve this, three laser beams measure the same point from different angles. The measured vibration components – initially recorded in the respective beam directions as u, v, and w components – are then transformed into a Cartesian coordinate system (x, y, z).

There are two basic types of 3D laser vibrometers: The 3D single-point vibrometer measures the three-dimensional vibration at a fixed measurement point. The 3D scanning vibrometer additionally captures many points automatically in sequence and provides complete 3D mode shapes across an entire measurement surface.

Important terms:

In-plane vibration: Motion within the material plane (tangential to the surface)
Out-of-plane vibration: Motion perpendicular to the surface (normal motion)
3D displacement: The complete vibration vector with components in the x, y, and z directions

A laser Doppler vibrometer always measures vibrations along the direction of the laser beam. A single laser therefore captures exactly one vibration component – this is referred to as a 1D laser vibrometer.

This one-dimensional measurement is sufficient when only the out-of-plane motion is relevant – meaning the vibration perpendicular to the surface. A typical example is vibroacoustics on thin metal sheets: sound radiation in such structures is primarily caused by the normal motion of the surface.

If the laser beam hits a flat surface at an exact 90° angle, the measured component corresponds entirely to the out-of-plane motion. However, if the laser beam deviates from this angle, the measurement signal contains both in-plane and out-of-plane motion components. A clean separation of these directions is not possible with a single laser.

single-point measurement with laser doppler vibrometer

A 3D laser vibrometer solves this problem: three laser beams measure the same point from different angles. The vibration components recorded in this way are initially present in the beam directions of the three vibrometers (u, v, w components) and are then transformed into a Cartesian coordinate system (x, y, z). Only with this complete 3D information is an exact separation of in-plane and out-of-plane vibrations possible.

3D measurement at a glance

3 laser beams measure the same point
Recorded components: u, v, w (beam directions)
Transformation into Cartesian coordinates: x, y, z
Result: complete 3D vibration vector

The transformation is performed automatically by the SMART Lab software. The user receives the measurement data directly in x, y, and z coordinates – with no manual conversion required.

3D laser Doppler vibrometers are available in two configurations: as a single-point system for measuring at a fixed point, or as a scanning system for automatically capturing entire surfaces.

A 3D single-point vibrometer measures the three-dimensional vibration at a fixed measurement point. The point remains stationary – there is no spatial scanning of the surface. The system provides the Cartesian coordinates (x, y, z) directly at the digital and analog outputs of the device, enabling in-plane/out-of-plane separation at exactly this point.

Note/Limitation:

Since only a single point is captured, the 3D single-point vibrometer provides local information – creating a mode shape across a surface is not possible.

A 3D scanning vibrometer measures three-dimensional vibrations across many points automatically in sequence. It provides complete 3D mode shapes and enables in-plane/out-of-plane separation across the entire measurement surface.

The system is suitable for modal analyses (EMA/OMA), overall structural assessments, as well as complex geometries and large components. By importing 3D models and measuring directly on FEM nodes (e.g., NASTRAN), the 3D scanning vibrometer can be integrated into the validation process.

Comparison: 3D Scanning vs. 3D Single-Point Vibrometer

	3D Scanning Vibrometer	3D Single-Point Vibrometer
Measurement principle	Automatically scans a surface with many measurement points – captures complete 3D mode shapes.	Measures the three-dimensional vibration at a fixed, stationary measurement point.
Measurement points	Many points automatically in sequence – no manual repositioning required.	One point – additional measurement points require repositioning of the fiber head.
In-plane / Out-of-plane separation	Across the entire measurement surface.	At the single measurement point.
Typical applications	Modal analysis (EMA/OMA), FEM validation, complex geometries and large components.	Local vibration analysis, hard-to-access measurement locations.
Optomet product	SMART 3D-Scan	SMART 3D-Fiber

For flat structures and pure out-of-plane analysis, a 1D laser vibrometer may be sufficient. However, once complex geometries, in-plane vibrations, or FEM model validation come into focus, only three-dimensional measurement provides the complete picture.

Visualizing in-plane and out-of-plane modes:

A brake disc vibrates both perpendicular to the surface (out-of-plane) and within the plane of the disc (in-plane). A 1D laser vibrometer captures only the out-of-plane motion. Only a 3D laser vibrometer makes both mode types visible and reveals their corresponding resonance frequencies.

Complex geometries and freeform surfaces:

For a flat plate, a 1D measurement may be sufficient in some cases. However, as soon as the structure includes curvatures, undercuts, or freeform surfaces – such as turbine blades, hollow bodies, or deep-drawn components – 3D information is required to fully capture the vibration behavior.

Accurate in-plane/out-of-plane separation:

A clean separation of in-plane and out-of-plane vibrations is only possible when the full 3D vibration vector is known. With 1D measurements, an oblique laser incidence produces a mixed signal – the direction components cannot be separated.

FEM validation:

In FE simulations (e.g., NASTRAN, ANSYS, Abaqus), a complete 3D displacement vector is calculated at each node. For correct validation, measurement data and simulation must exist in the same coordinate system. For complex structures, a 3D laser vibrometer is required for this purpose.

Strain and stress calculation:

A 3D laser vibrometer captures the complete displacement vectors in all three spatial directions. These data enable the calculation of strains and the stresses derived from them – an alternative to strain gauges (SGs). Structural deformations occur not only perpendicular to the surface but also within the material plane.

Optomet offers two 3D laser vibrometers from the SMART Series: the SMART 3D-Scan for full-field acquisition of mode shapes, and the SMART 3D-Fiber for three-dimensional single-point measurement.

SMART 3D-Scan

The system is modular in design: An existing SMART Scan+ can be upgraded at any time to a full 3D scanning system. SMART Lab supports the entire workflow – from camera matching of the three devices with the 3D model, to automatic laser calibration, all the way to live visualization of the measurement data during the scan.

Key features:

Three synchronized SMART Scan+ vibrometers
Up to 512 × 512 measurement points
Automatic transformation into x, y, z coordinates
Import of 3D models (STL, OBJ, PLY, NASTRAN)
Measurement directly on FEM nodes

More about SMART 3D-Scan | Data sheet SMART 3D-Scan (PDF)

SMART 3D-Fiber

The SMART 3D-Fiber is a 3D single-point vibrometer with a compact fiber head. Three laser beams measure the same point and provide the Cartesian coordinates (x, y, z) directly at the digital and analog output. The compact 3D fiber head is particularly suitable for hard-to-reach measurement locations – for example in gearboxes, engine compartments, or components with tight installation spaces.

The integrated webcam shows in the camera image whether all three lasers hit the same point on the surface. The system can be operated either via the SMART Lab software or directly through an external DAQ system.

Key features:

Compact 3D fiber head (107 × 100 × 102 mm)
Working distance: 83 mm; additional fiber heads with working distances from 25 mm to 100 m are available.
Direct output of x, y, z coordinates at the analog/digital output
Integrated webcam for aligning the three lasers to the measurement point
Suitable for hard-to-reach measurement locations

More about SMART 3D-Fiber | Data sheet SMART 3D-Fiber (PDF)

3D laser vibrometers are used wherever one-dimensional measurements are not sufficient – whether due to complex geometries, relevant in-plane vibrations, or the requirement for complete FEM validation.

Turbine blades and blisks

Turbine blades and blisks (blade integrated disks) feature complex geometries with curvature and twist.

Vibrations occur in all three spatial directions and cannot be fully captured with a 1D vibrometer. A 3D scanning vibrometer provides complete mode shapes and enables direct comparison with FEM simulations.

Complex geometries and freeform surfaces

Hollow bodies, deep-drawn components, plastic housings, or complex panels are often difficult to analyze using one-dimensional measurements alone.

The surface normal varies across the structure, meaning a 1D laser captures different mixtures of in-plane and out-of-plane motion at different points. A 3D laser vibrometer delivers the complete vibration vector at every measurement point – independent of the local surface orientation.

Brake systems

In the analysis of brake discs on brake test rigs, in-plane modes play a key role – for example in the investigation of brake squeal.

These tangential vibrations within the disc plane are not visible with a 1D scanning vibrometer. Only 3D measurement reveals these modes and enables a complete characterization of the vibration behavior.

Complex geometries and freeform surfaces (lightweight structures)

Lightweight structures made of fibre-reinforced composites or sandwich constructions often show complex vibration behavior with pronounced in-plane components.

Complete 3D vibration information is required for characterization and validation of these components – especially when the measurement data must be aligned with FEM models.

A 3D scanning measurement with the SMART 3D-Scan follows a structured workflow – from geometry acquisition to automatic calibration and finally to visualization of the results. The SMART Lab software guides the user through the entire process.

Step 1: Import the 3D geometry

In the first step, the 3D geometry of the test object is loaded into SMART Lab. The software supports common formats such as STL, OBJ, and PLY, as well as FEM models from NASTRAN. Alternatively, the geometry can be captured directly via the camera image.

3D-Modell in Vibrometer Software zum Abgleich per Kamera

Step 2: Camera matching

During camera matching, the three scanning vibrometers are aligned with the 3D model. This creates a digital twin: the orientation and position of each device in space, relative to the test object, are precisely known.

Kalibrierung des Lasers für die Schwingungsmessung per Software

Step 3: Laser calibration

In the next step, the three laser beams are calibrated. SMART Lab performs this process fully automatically. The calibration quality can be checked at any time – including mathematical error calculation.

Erstellung von Messpunkten in der Software für Schwingungsmessung

Step 4: Define measurement points

The measurement points are created directly on the 3D model or in the camera image. For FEM validation, the points can be automatically placed on the nodes of the simulation model – ensuring that measurement and simulation lie in the same coordinate system.

Messaufbau mit 3 Scanning Vibrometern zur 3D-Schwingungsanalyse

Step 5: Automatic scan

The system scans all defined measurement points automatically and in sequence. The measurement is phase-accurate, ensuring that the vibrations of all points are correctly aligned in time. During the scan, SMART Lab displays the measurement data live – allowing analysis to begin while the measurement is still in progress.

Schwingungsanalyse in Smart Lab Software

Step 6: Transformation and visualization

The measured vibration components (u, v, w) are automatically transformed into Cartesian coordinates (x, y, z). SMART Lab visualizes the results as FRFs, mode shapes, or time-domain signals – in both the time and frequency domain.

The 3D single-point measurement with the SMART 3D-Fiber is set up in just a few steps. The system provides the 3D vibration data either via the SMART Lab software or directly through the analog and digital outputs.

Step 1: Establish connection

The SMART 3D-Fiber is connected to the PC via Ethernet. Alternatively, the system can be connected directly to an external DAQ system – the x, y, and z coordinates are available both at the digital output and at the analog outputs.

Step 2: Align the fiber head

The 3D fiber head is aligned with the test object. The integrated webcam shows in the camera image whether all three laser beams hit the same point on the surface. This ensures that the measurement captures the complete 3D vibration vector at exactly one point.

Step 3: Excite the test object

The test object is excited to vibrate – for example using the integrated signal generator of the SMART 3D-Fiber or via an external excitation source.

Step 4: Start measurement and analyze

After starting the measurement, the 3D vibration data is available in real time. Analysis is carried out in the SMART Lab software or directly in the connected DAQ system.

Portrait of Tobias Schröder, Head of Sales & Marketing at Optomet

"For more than two decades, Optomet has stood for precise vibration measurement. Our 3D laser scanning vibrometers deliver reliable data – from laboratory analysis to industrial quality control."

Tobias Schröder (M.Sc. Mechanical Engineering)
Head of Sales & Marketing

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Advantages over conventional sensors

	Conventional contact sensors	3D laser vibrometer
Measurement directions	Triaxial sensors are required for 3D acquisition – they are larger, heavier, and influence the vibration behavior more strongly	Captures all three spatial directions (x, y, z) simultaneously at every measurement point
In-plane / Out-of-plane	Clean separation only possible with complex sensor arrangements	Exact separation of in-plane and out-of-plane vibrations at every measurement point
Complex geometries	Limited applicability for curved or freeform surfaces	Complete 3D acquisition even for complex structures such as turbine blades or hollow bodies
FEM validation	Complex assignment of sensor positions to FEM nodes	Direct measurement on FEM nodes; measurement data and simulation in the same coordinate system
Strain and stress calculation	Requires additional strain gauges with demanding installation	Calculation possible from complete 3D displacement vectors – without additional sensors
Influence on natural frequencies	Additional mass influences vibration behavior	Non-contact measurement without mass loading
Measurable frequency range	Typically limited to a few kHz to several tens of kHz	Up to 50 MHz (SMART Series)

Answers to common questions about the measurement principle, areas of application, and system configuration of 3D laser vibrometers.

What is the difference between a 1D and a 3D laser vibrometer?

A 1D laser vibrometer measures the vibration along the direction of the laser beam – meaning exactly one component. A 3D laser vibrometer uses three laser beams to measure all three spatial directions and provides the complete vibration vector in Cartesian coordinates (x, y, z).

When is a 3D laser vibrometer required?

A 3D laser vibrometer is required when in-plane vibrations are relevant, when complex geometries with curvatures or freeform surfaces need to be analyzed, or when FEM validation must be performed using complete 3D displacement vectors.

What do in-plane and out-of-plane mean?

Out-of-plane refers to vibration perpendicular to the surface (normal motion). In-plane refers to vibration within the material plane, i.e., tangential to the surface. Only a 3D laser vibrometer can cleanly separate these components.

How does the transformation into Cartesian coordinates work?

The three lasers initially measure in their respective beam directions (u, v, w). SMART Lab software automatically calculates the vibration components in a Cartesian coordinate system (x, y, z) – aligned with the test object or FEM model.

What is the difference between 3D scanning and 3D single-point?

A 3D single-point vibrometer (SMART 3D-Fiber) measures the three-dimensional vibration at a fixed measurement point. A 3D scanning vibrometer (SMART 3D-Scan) automatically moves across many points in sequence and provides complete 3D mode shapes across an entire surface.

Can an existing 1D system be upgraded to a 3D system?

Yes. The SMART Series is modular. An existing SMART Scan+ can be expanded at any time with two additional devices to form a complete SMART 3D-Scan.

Which 3D models can be imported?

SMART Lab supports common formats such as STL, OBJ, and PLY, as well as FEM models from NASTRAN. Measurement points can be placed directly onto FEM nodes.

How is calibration performed in a 3D scanning system?

Calibration of the three laser beams is fully automated in SMART Lab. The software checks calibration quality and displays mathematical error calculations.

What frequency range can be measured with a 3D laser vibrometer?

With the SMART Series, frequencies from DC to 50 MHz can be measured.

Is strain and stress calculation possible?

Yes. Strains and the stresses derived from them can be calculated from the complete 3D displacement vectors – providing an alternative to strain gauges.

Which laser class is used?

The SMART 3D vibrometers use eye-safe laser sources. The invisible SWIR measurement laser (1550 nm) is classified as laser class 1 (< 10 mW) and does not require safety goggles. The visible pilot laser used for alignment is laser class 2 (< 1 mW) and is also eye-safe.

Are the measurement points captured simultaneously or sequentially?

The three lasers of a 3D system measure the same point simultaneously from different angles. In a 3D scanning vibrometer, the individual measurement points are approached sequentially. Using a reference signal, the time-shifted measurements are combined phase-correctly.

How is the test object excited?

The excitation depends on the measurement task and can be performed using a modal hammer, shaker, piezo actuator, or through real operating conditions. The SMART Series includes an integrated signal generator that can be used as a defined excitation source.

Can a 3D laser vibrometer be integrated into automation environments?

Yes. The measurement data is available both digitally and analogly and can be integrated into existing test benches and measurement chains via open interfaces. External triggers enable synchronized measurement processes.

What working distance is possible?

SMART 3D-Scan: The system enables working distances from approx. 6.5 mm to 100 m – depending on the object size and setup.

SMART 3D-Fiber: The compact 3D fiber head has a fixed working distance of 83 mm. Alternatively, additional fiber heads with working distances from 25 mm to 100 m are available.

Laser Sources
Fundamentals of the laser types used in vibrometry – Helium-Neon, SWIR, and fiber-coupled systems.

Laser Doppler Vibrometry
Structure, operating principle, and application areas of Laser Doppler Vibrometry.

Vibration Measurement
Methods, measurement setup, and evaluation of vibration data in research and industry.

Doppler Effect
Physical principle of Laser Doppler Vibrometry – the basis for precise velocity measurement.

Signal Processing
Analysis of vibration data using FFT, frequency-domain evaluation, and real-time processing.

The complete technical specifications can be found on the respective product pages and in the data sheets.