Laser Doppler Vibrometer vs Laser Vibrometer – Types, Features, and Applications

A laser vibrometer is a precision instrument that measures vibration without physical contact using a laser beam. The most widely used type is the laser Doppler vibrometer (LDV), which applies the Doppler effect to detect vibration parameters accurately. This guide explains the working principle, classification, and advantages of LDVs, and compares them with laser triangulation vibrometers.

What is a Laser Doppler Vibrometer?

A laser Doppler vibrometer works on the principle of laser interferometry. When a coherent laser beam is aimed at a vibrating object, its frequency or phase changes due to the Doppler effect. By combining the reflected beam with a reference beam, a photodetector captures frequency and phase shifts, which are then demodulated to obtain precise vibration data.

Classification of Laser Doppler Vibrometers

1. Single-Point Fixed LDV

• Measures vibration at one fixed point.

• Suitable for high-temperature, long-distance, or ultrasonic environments.

• Compact, cost-effective, and popular in academic research.

2. Single-Point Handheld LDV

• Portable and fast for one or more non-synchronized points.

• Ideal for industrial inspections and quick calibrations.

3. Two-Point or Multi-Point Synchronous LDV

• Measures multiple points simultaneously with high synchronization.

• Used for displacement difference detection, ODS, and OMA analysis.

4. Three-Dimensional Fixed LDV

• Captures X, Y, Z axis vibrations at the same point.

• Suitable for 3D modal testing.

5. Scanning LDV

• Measures many points sequentially.

• Used in steady-state vibration analysis where real-time results are not essential.

6. Fiber-Optic LDV

• Works in confined or hazardous environments.

• Small probe size enables measurement in areas inaccessible to direct laser beams.

Laser Triangulation Vibrometer

Besides LDVs, the laser triangulation vibrometer is also widely used. It calculates displacement based on the triangulation method, tracking the movement of a reflected laser spot.

Types:

• Direct Incidence – High precision, low error.

• Oblique Incidence – Higher resolution but smaller range.

Comparison: Laser Doppler Vibrometer vs Laser Triangulation Vibrometer

Choosing the Right Laser Vibrometer

• For high-precision, long-range, and wide-bandwidth measurements, choose a laser Doppler vibrometer.

• For budget-friendly, low-frequency applications, a laser triangulation vibrometer may suffice.

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