HeNe laser vibrometers (Helium Neon)

Helium-neon laser vibrometers (HeNe) operate with visible red laser light at a wavelength of 632.8 nm. They enable precise vibration measurements through liquids and achieve particularly small spot sizes for microstructure applications.

Measurement through liquids: The wavelength of 632.8 nm is barely absorbed by water – ideal for measurements through water, biological fluids, or transparent media.
Smallest spot sizes: HeNe lasers achieve spot sizes in the range of 3 µm – optimal for vibration measurements on microstructures.
Low thermal load on components: The low laser power below 1 mW minimizes heat absorption at the measurement object – advantageous for sensitive MEMS and thermally sensitive structures.

He-Ne Laser vibrometer measuring throught water

An HeNe laser vibrometer is a non-contact measurement device for capturing vibrations. The measurement principle is based on the Doppler effect: the laser beam is directed at a vibrating surface, and the frequency shift of the reflected light is proportional to the vibration velocity of the surface.

HeNe stands for helium-neon and refers to a gas laser that produces light in the visible red spectral range. Optomet HeNe laser vibrometers operate at a wavelength of 632.8 nm – visible to the human eye and with physical properties that offer advantages for specific measurement tasks.

The shorter wavelength enables particularly small spot sizes in the range of 3 µm – optimal for measurements on microstructures. Additionally, light at 632.8 nm is barely absorbed by water, which enables measurements through liquids. The low laser power below 1 mW minimizes the thermal load on sensitive components.

Technical key data:

Parameter	Value
Measurement laser wavelength	632.8 nm (visible, red)
Pilot laser	Not required (measurement laser is visible)
Measurement laser class	Class 2, < 1 mW

SWIR or HeNe?

SWIR (1550 nm) is the standard choice for most applications – offering a significantly higher signal-to-noise ratio, excellent performance on dark surfaces and fiber-reinforced composites, and extended measurement distances.

→ Optomet SMART Series

HeNe (632.8 nm) is suitable for measurements through water or other liquids, as SWIR radiation is strongly absorbed in these media.

→ Optomet Vector Series (HeNe)

The physical properties of HeNe lasers – low absorption in water, small spot size, low laser power – make them suitable for specific measurement tasks.

Measurements through water and liquids

SWIR radiation at 1550 nm is strongly absorbed by water. HeNe lasers at 632.8 nm penetrate aqueous media with low attenuation.

This enables vibration measurements on objects that are submerged in water or measured through liquids – for example in medical technology, biology, or underwater acoustics.

MEMS and microstructures

For measurements on MEMS structures (Micro-Electro-Mechanical Systems) such as cantilevers, resonators, or micromirrors, a small spot size is essential.

HeNe lasers achieve spot sizes in the range of 3 µm. The low laser power reduces thermal load – even slight heating can cause deformation in sensitive microstructures.

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

"For more than two decades, Optomet has stood for precise vibration measurement. Our laser 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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Comparison: HeNe vs. SWIR laser vibrometers

Both laser technologies have their justification – the choice depends on the application. The following table compares the key differences.

	HeNe (632.8 nm)	SWIR (1550 nm)
Wavelength	632.8 nm (visible, red)	1550 nm (invisible)
Laser class	Class 2, < 1 mW	Class 1, < 10 mW
Protective eyewear required	No	No
Signal-to-noise ratio	Lower due to limited laser power	Higher due to greater power budget
Backscattering behavior	Good on metallic and reflective surfaces	Better on dark, matte, and fiber-reinforced surfaces
Surface preparation	Depending on the surface, retro-reflective tape or spray required	Generally not required
Measurement through liquids	Yes – low absorption at 632.8 nm	No – strong absorption at 1550 nm
Measurement on hot surfaces	Limited – thermal emission can interfere	Yes – insensitive to thermal radiation
Long measurement distances	Limited	Yes – up to over 300 m (e.g. bridges, rotors, facades)
Frequency bandwidth	DC – 25 MHz	DC – 50 MHz (SMART Series)
Max. vibration velocity	Up to 10 m/s	Up to 50 m/s (SMART Series)
Laser source lifetime	Limited – HeNe tube ages (approx. 10,000 h)	Long – no regular replacement required
Spot size (with identical optics)	Smaller due to shorter wavelength (factor 2 to 2.5)	Larger due to longer wavelength
Optomet products	Vector Series, HeNe scanning vibrometers	SMART Series, Nova Series, Fiber Series

Optomet offers HeNe laser vibrometers for applications requiring a visible laser beam or a particularly small spot diameter. These products are part of the CLASSIC Series.

The Vector Series is Optomet's product line for HeNe-based single-point laser vibrometry. With the comparatively short wavelength (632.8 nm), the laser beam can be focused to a very small spot diameter. The Vector Series enables non-contact vibration measurements on objects from microscopic to macroscopic sizes.

Learn more about the Vector Series

Product	Description
Vector Standard	Single-point vibrometer with visible HeNe laser for measurements through liquids and on reflective surfaces
Vector Micro-Optics	Specialized system for measurements on the smallest objects with a laser spot of approx. 3 µm and integrated 4K camera
HeNe scanning vibrometer	Scanning system with HeNe laser for full-field vibration analysis on small objects and printed circuit boards

In this section, you will find answers to frequently asked questions about HeNe laser vibrometers – including application areas, eye safety, wavelength, service life, and comparison with SWIR systems.

When should an HeNe laser vibrometer be used?

HeNe laser vibrometers are the right choice for two main applications:

Measurements through liquids: At 632.8 nm, absorption in water is low. SWIR radiation (1550 nm) is strongly absorbed.
Measurements on microstructures: The shorter wavelength enables a smaller laser spot – ideal for electronic components, MEMS, or printed circuit boards.

Is an HeNe laser vibrometer eye-safe?

Yes. Optomet HeNe laser vibrometers operate with an output power below 1 mW and are classified as laser class 2. Protective eyewear is not required during normal operation. The natural blink reflex protects the eye during brief exposure.

How small is the laser spot of an HeNe vibrometer?

Due to the shorter wavelength, the spot diameter of HeNe systems is smaller by a factor of 2 to 2.5 compared to SWIR systems with identical optics. Example: approx. 30 µm for HeNe versus 89 µm for SWIR (at 500 mm distance with 100 mm optics). With the Vector Micro-Optics, spot sizes of approx. 3 µm are possible.

How long does an HeNe laser tube last?

HeNe laser tubes have a typical service life of approx. 10,000 operating hours. After this time, the laser power decreases and the tube must be replaced. SWIR laser diodes, on the other hand, typically operate for the entire device lifetime without replacement.

What frequency bandwidth and velocity do HeNe vibrometers achieve?

The Vector Series achieves a frequency bandwidth of DC to 25 MHz and vibration velocities up to 10 m/s. For comparison: SWIR systems of the SMART Series achieve DC to 50 MHz and up to 50 m/s.

What limitations does an HeNe laser have?

HeNe laser vibrometers are not suitable for all applications. The most important limitations:

Dark or matte surfaces: HeNe systems deliver a weaker signal than SWIR systems. Surface preparation with retro-reflective tape or spray is often required.
Hot surfaces: Thermal emission in the visible range can interfere with the measurement signal.
Long measurement distances: Due to the lower laser power (< 1 mW), HeNe systems are less suitable for long-range measurements.

Which Optomet products use an HeNe laser?

The Vector Series and the HeNe scanning vibrometer. The Vector Series includes the Vector Standard for general applications and the Vector Micro-Optics for measurements on the smallest structures with a laser spot of approx. 3 µm.

HeNe or SWIR – which technology is better?

Neither is fundamentally better – the choice depends on the application:

HeNe (632.8 nm): Measurements through water, microstructures, small spot diameter
SWIR (1550 nm): Dark/matte surfaces, hot objects, long measurement distances, higher signal-to-noise ratio

For most industrial applications, SWIR is the standard choice. HeNe is the specialized alternative for specific requirements.

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.