Digital Holografy
Virtual Labs and Remote Experiments
The remote-controlled laboratory developed at the Institut für Technische Optik (ITO) University of Stuttgart allows performing remote experiments by using a digital holographic microscope. The user can select samples (e.g. cells or microsystems) of various sizes and complexity, calculate the hologram and get a 3D representation of the object wave front.
A Nd-YAG Laser is coupled into a fiber, which guides the beam into a coupler that subsequently divides the input laser beam into a reference arm and object arm. The object arm fiber can be switched for different illumination modes, i.e., transmission mode or reflection mode, depending on the properties of the object to be investigated. The object is imaged through a microscopic objective and a CCD camera is used to record the hologram. The microscopic sample is mounted on an electrically-driven 3D positioner, allowing the user to shift the field of view at sub-micron precision. The hologram is transferred to the computer for subsequent processing, including numeric reconstruction of phase and intensity and the calculation of phase difference compared to previous holograms.
Holographic Microscope
The control is provided by remote desktop system (VNC), connecting through a proxy using an encrypted channel (SSH tunnel), adding standard authentication through the modular authentication system PAM and encryption for security, based on existing software such as Java-Portlets running on the BW-eLabs Portal server and Python modules on the proxy server. The connection to the data base and publication backend eSciDoc is work in progress and will allow automatic storage and access to experimental results, including identification through a unique, persistent digital identifier (DOI). eSciDoc is connected to the OPUS document server at the University of Stuttgart for publication. Sets of actual experimental data can be accessed and referenced through OPUS, using the DOI identifiers. In addition to the generic access using VNC, a 3D virtual environment (Wonderland) is being implemented. This frontend is intended to provide intuitive access to the hardware, as well as support collaboration between users by providing communication channels.
The data and control flow of the remote experiment.
Frontpanel of the LabView VI used for the control of the experiment.
Contact: Dr. Giancarlo Pedrini [E-Mail], Margarita Riedel [E-Mail],
Institut für Technische Optik (ITO) [Link]
Literature: Marc Wilke, Igor Alekseenko, Guohai Situ, Konica Sarker, Margarita Riedel, Giancarlo Pedrini and Wolfgang Osten, "Remote laboratory for Digital Holographic Metrology", Proc. SPIE 8082, 80820D (2011); doi:10.1117/12.892073
[Link]
Poster: "Remote laboratory for Digital Holographic Metrology" [Link]
Video: "Remote laboratory for Digital Holography" [Link]