Frequently Asked Questions about Laser Doppler Vibrometer
Question number FAQ-1345
Advantages of using Laser Doppler Vibrometer
- Non-contact measurement does not impose any load on the object being measured.
- The laser beam spot can be narrowed to a few micrometers, resulting in high spatial resolution and enabling multi-point measurement of minute objects.
- Since the standard output is "velocity," it can be easily converted to acceleration and displacement using first-order calculus.
| ■ | When a detector, such as an accelerometer, comes into contact with an object, "contact resonance" caused by the influence of the contact surface becomes a problem. This occurs because the rigidity of the mounting area, including the contact surface, and the mass of the accelerometer form a vibrating system. This is a phenomenon where a "spring" is created between the object and the detector, causing resonance. The frequency at which contact resonance occurs varies depending on the mounting method. As a guideline for mounting accelerometers, the frequency is around 20 kHz with the best screw fastening method, and around 10 kHz with adhesive or thin double-sided tape. This is the main reason why accelerometers cannot be used for vibration measurement above 20 kHz. |
| ■ | Non-contact vibration measurement using Laser Doppler Vibrometer allows for vibration measurement without any impact on the vibration itself. Because the beam spot can be narrowed to a few micrometers, vibration measurement is possible even in small, narrow areas. The measurement frequency range is wide, from 3 MHz (LV-1710) in the normal configuration to up to 20 MHz with options, and a system configuration that simultaneously detects vibrations in three axes is also possible. |
| ■ | When using Laser Doppler Vibrometer to measure (vibrate) a moving object, "velocity" (m/s) is extremely advantageous. When measuring minute vibrations of an object using "displacement" in an environment affected by background noise, the displacement of the background noise is large, obscuring the displacement of the object and making waveform observation difficult. To eliminate this effect, a high-performance vibration isolation table is required. On the other hand, when observing using velocity output, the velocity value of low-frequency background noise is smaller than the vibration velocity of the object, making it easier to observe the vibration waveform of the object. The faster an object vibrates, such as an ultrasonic transducer, the less susceptible it is to background noise when observed using velocity output. |
Last updated: 2004-04-19