page_title: Digital holographic microscopy
section_title: MEMS
hierarchical_section_title: Digital holographic microscopy / Applications / MEMS
caption_attribution_description: English: Ultrasonic transducer vibrating at 8MHZ measured by Digital Holographic Microscopy. Courtesy of IPMS Dresden
context_page_description: Digital holographic microscopy is digital holography applied to microscopy. Digital holographic microscopy distinguishes itself from other microscopy methods by not recording the projected image of the object. Instead, the light wave front information originating from the object is digitally recorded as a hologram, from which a computer calculates the object image by using a numerical reconstruction algorithm. The image forming lens in traditional microscopy is thus replaced by a computer algorithm.
  Other closely related microscopy methods to digital holographic microscopy are interferometric microscopy, optical coherence tomography and diffraction phase microscopy. Common to all methods is the use of a reference wave front to obtain amplitude and phase information. The information is recorded on a digital image sensor or by a photodetector from which an image of the object is created by a computer. In traditional microscopy, which do not use a reference wave front, only intensity information is recorded and essential information about the object is lost.
  Holography was invented by Dennis Gabor to improve electron microscopy.
context_section_description: Use in conjunction with a stroboscopic electronic unit to synchronize the laser pulse for sample illumination and the camera acquisition with the MEMS excitation, DHM® provides time sequences of 3D topography along the excitation phase of the microsystems.
  Analysis of this time sequence of 3D topographies acquired at a fixed frequency provides vibration map and enable decomposition of the movement in term of in- and out-of-plane.
  Sweeping of the excitation frequency provides structural resonances as well as amplitude and phase Bode analysis.
  Measurement have demonstrated on many type of MEMS such as comb drive actuators, micro-mirrors, accelerometers, gyroscopes, micro pumps, microphones, ultrasonic transducers, cantilevers, and surface acoustic waves among others.
caption: Ultrasonic Transducers measured at 8 MHz in stroboscopic mode