Megapixel Scanning Laser Vibrometer from SmarAct
Vibrations play a decisive role in the performance of mechanical structures. This also includes the field of microelectromechanical systems (MEMS).
In this way, undesired excitations from internal resonance frequencies can lead to material fatigue and failure on the one hand, but on the other hand they can also be used to optimize the overall system, e. g. to improve the response behavior of a miniature microphone. Precise knowledge of vibration is therefore essential in order to incorporate it into the design as a functional component. Due to the low mass and size of MEMS, the mounting of sensors is not suitable for this purpose, a contactless measuring method is required.
For this reason, SmarAct GmbH developed the Picoscan, a high-resolution laser scanning vibrometer, which has been available on the market since January 2018.
During the measurement, a focused laser beam of a Michelson interferometer is scanned over the sample surface to detect oscillations with a maximum frequency of 5 MHz and a minimum amplitude in the picometer range. The movement of the optics is realized by our proven linear positioners with an accuracy of 1 nm. Since the pixels are measured sequentially, it is necessary to synchronize the measurement data. A lock-in amplifier and function generator are integrated in the Picoscan for this purpose. By means of an excitation signal, the sample to be measured is set into vibration via a piezo based holder. In combination with the lock-in gain, amplitude and phase at each pixel can be unambiguously determined at any time. Furthermore, an enormous data reduction is possible. Instead of storing a complete FFT spectrum per measurement point, only amplitude and phase have to be recorded. This is the key to capturing megapixel images. In existing solutions, vibrations are recorded for only a few hundred predefined points per image. This leads to a low resolution during the reconstruction of the vibration modes and there is a possibility that vibrations at certain parts of the sample have not been detected.
The Picoscan Vibrometer is characterized by a number of other unique advantages.
In addition to its compact dimensions and UHV compatibility, the Picoscan offers the possibility to operate vibrometry and confocal laser microscopy with only one lens at the same time. An additional camera for imaging samples is therefore unnecessary and the correlation of both datasets is always guaranteed. The combination of a high-resolution lens with linear positioners offers an additional lateral resolution of 5 μm with an image size of 20 mm x 20 mm (larger on request).
Despite its performance, the Picoscan Vibrometer will be by far the most compact scanning vibrometer on the market. The ability to create megapixel images of vibration modes will help designers, manufacturers and researchers visualize MEMS in unprecedented detail.
Do contact SmarAct here if you require more information.