Unexpected vibrations are often symptomatic of serious technical problems in aircraft engines, power transformers, and other machinery whose failure may cause significant property damage and harm to the public. SRI has developed prototype cameras that display dynamic images showing intensity, duration, and location of the vibrations (both time series and frequency spectra). The novel camcorder-like devices contain sensors that can pinpoint acoustic vibrations and show potential trouble spots within the image. They allow the sound to be “seen.”
SRI’s vibration-imaging concept is based on the way vibrating surfaces modulate reflected light. This modulation is a small fraction of the total reflection (as low as parts per million). The vibration imaging system uses specialized optical sensor arrays to provide the required sensitivity for detection. The light intensity data from each pixel are processed to display vibration information that is spatially distributed across the imaged surface, thus detecting and localizing areas with excess or unusual vibration frequencies or phase.
The device uses standard optical lenses and has been shown to be suitable for visualizing distribution of vibration over surfaces. Spatial resolution ranges from microns to meters. The vibration imaging system also has the unique ability to record images of transient or propagating perturbations across a surface.