Low Cost Laser Vibrometer

What is the Laser Vibrometer?

  • Recording substrate-transmitted vibratory signal in animals has been difficult and hindered by the lack of reliable measuring devices. In the past, various equipment has been used to record substrate-transmitted vibratory signals, such as bamboo membrane and microphone, microphone, and gramophone pickup. Such devices are hard to operate, prone to noise and tend to distort measurements because of their mass.
  • A Laser Vibrometer is a device that utilizes a laser beam to make non-contact vibration measurements of a surface. The laser beam is directed at the surface of interest (e.g. plant leaf, social insect nest, surface where an insect stands, etc) and the vibration amplitude and frequency are extracted from the modulation of the laser beam due to the motion of the surface.
  • In our Laser Vibrometer a red laser pointer beam gets reflected by a retro-reflective foil, the reflected light generates an interference speckle patterns on surfaces around the laser beam. At ~1m from the reflector, the speckles are spaced 1- 3 mm. If the reflector is vibrated, the speckle pattern moves “fiercely”. The concomitant modulation of the illuminance of a photodiode is used to detect the movements of the speckles and hence the vibration generated by animal.
  • The Laser Vibrometer enables a precise measurement and characterization of substrate-transmitted vibratory signals.
  • In contrast to the Laser Doppler Vibrometer, our Laser Vibrometer is far less expensive because it does not utilize expensive optics to detect the reflected laser beam, rather our Laser Vibrometer uses inexpensive retro-reflective foil to send back the laser beam to the device where it is detected by a photodiode.

Field of application:
Vibratory signal plays an important part in communication in almost all species; Laser Vibrometry can be used to measure such vibration in great detail. For example many insects communicate using substrate born signals. Some insect sounds are quite loud, such as the singing of the cicada, while others are ultrasonic and can’t be heard. Some insects are so small that their songs are transmitted mainly through plant tissues rather than air. Researchers can use the Laser Vibrometer to record this unheard acoustic communication signal.Characterization of such signals will enable better understanding of the ecology and evolution of a given species. In some circumstances, once an acoustic signal has been characterized it can be used for management of unwanted organisms, e.g. disruption of communication.

Recording vibrational sound from gyne Vespula germanica using the low cost Laser Vibrometer

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