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Fabrication of volume holograms using sol-gel technology and its application to 3D profile measurementKuo, Che-Yu 20 July 2012 (has links)
A series of sol-gel based photopolymerizable silica glass for holographic storage have been synthesized via a facile chemical design in an effort to overcome the cracking problem incurred during the irradiation stage. The holographic composite material includes a low molecular weight polydimethylsiloxane (PDMS) with end-capped hydroxyl groups, an epoxide-containing coupling agent, a photopolymerizable acrylate monomer, and the sol-gel-derived silica matrix. Inclusion of PDMS provides improved compression stress and strain and toughness over the original unmodified samples, without deterioration on the diffraction efficiency (£b). A plateau value of £b ~ 40 % can be found under a beam power of 5.02 mW. Correlation between the molecular weight of acrylate polymer and £b of the holographic composite material is described and the discrepancies analyzed. The premature saturation of polymerization in the holographic system is attributed to the retarded free radical polymerization within the silica matrix. Minor variation of £b with photoinitiator concentration is observed, indicating that only moderate molecular weight is required for a reasonably high £b. The crack-free mechanism is based on the chemical and physical interactions within the material system.
We also investigated the pore size and volume effect for optical properties, especially in studies of diffraction efficiency. With mixing rubber additives, the pore characteristics change via measurement of BET technique. The results indicated that moderate pore size made high diffraction efficiency for porous matrix and some characterizations also were presented.
On the other hand, the optical application of this recording medium was described via 3D projected fringes profilometry (PFP) measurement. We recorded coded pattern on medium by employing fiber devices as light source. Using endoscope as image-derived tool, we get double-projected fringe images on tiny object. By PFP technique, a performed retrieved image can be achieved.
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