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PICOSCAN Laser-Scanning Vibrometer

The PICOSCAN Vibrometer addresses the need for R&D and QC instrumentation that keeps pace with the ever increasing complexity of micromechanical systems. SmarAct’s vibrometer is developed for megapixel imaging of vibrational modes of microscopic structures. This is achieved by raster-scanning a tightly focussed laser beam of a Michelson interferometer over the sample to measure the vibrations for each pixel of the microscopic image. The PICOSCAN Vibrometer is equipped with a piezo-based sample shaker and a digital lock-in amplifier to measure amplitude and phase of the vibrations from which bending modes of up to 2.5 MHz can be reconstructed.
The use of SmarAct’s linear piezo motors allows the imaging of structures with a size of up to 20 mm. A unique feature of the
PICOSCAN Vibrometer is that the interferometer laser beam is used simultaneously to record a confocal reflection image of the sample with a lateral resolution of 5 µm. This microscopic image is thus intrinsically aligned with the vibration measurements and an additional microscope imaging system is not required. The controller and UHV-compatible scanner are kept very compact which does not only save desk space but also allows for the integration into confined environments.

System components

  • PICOSCAN Vibrometer: contains an interferometer, function generator and lock-in amplifer (33 cm x 28 cm x 7.5 cm)
  • PICOSCAN Motion Controller: performs the closed loop operation of the XYZ positioners and contains a power amplifer for the shaker stage (33 cm x 28 cm x 7.5 cm)
  • XYZ scanner (10 cm x 5.5 cm x 7.5 cm) to raster-scan the focussing laser head over the sample
  • Granite plate (20 cm x 15 cm x 4 cm) with 2.5 cm diameter post for mounting the scanner
  • Shaker stage with holder

 

Vibration measurements
Working principle: Michelson interferometer, single mode fibre coupled
Measurements laser: 1550 nm DFB laser diode, stabilized (NIST traceable), Laser class 1 (150 µW)
Minimum laser spot diamter: 10 µm
Vertical resolution: 10 pm (more details)
Optical microscope
Working principle: Confocal laser scanning microscope
Measurements laser: see above
Lateral resolution: 5 µm
Maximal image size: 20 mm x 20 mm
Maximal number of pixels: 1000 x 1000
Acquisition time: approx. 1 min for 128 px x 128 px

Example measurements

measurement data
Vibrational mode of a circular titanium membrane at 533 kHz

measurement data

Torsional motion of a triangular silicon nitride cantilever at 277 kHz

Function generator
Frequency range: 1 Hz - 2.5 MHz
Maximal power: 10 W
Shaker stage (custom actuators supported)
Frequency range: 1 Hz - 1 MHz
Dimensions: d x h: 12.5 mm x 6 mm
Digital lock-in amplifier
Frequency range: 250 Hz - 2.5 MHz
Time constant: Adjustable from 1 µs to 0.5 ms
Dynamic reserve: >100 dB
Scanning motion systems
Working principle: 3 axes linear piezo drive, closed loop
Resolution: 1 nm
Repeatability: 30 nm
Maximal travel: 20 mm (others on request)