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http://hdl.handle.net/20.500.12386/24950
Title: | Programmable CGH on photochromic material using DMD | Authors: | Alata, Romain PARIANI, Giorgio Zamkotsian, Frederic Lanzoni, Patrick BIANCO, ANDREA Bertarelli, Chiara |
Issue Date: | 2016 | Volume: | Advances in Optical and Mechanical Technologies for Telescopes and Instrumentation II | Editors: | Navarro, Ramón; Burge, James H. | Series: | PROCEEDINGS OF SPIE | Number: | 9912 | First Page: | 991234 | Abstract: | Computer Generated Holograms (CGHs) are useful for wavefront shaping and complex optics testing, including aspherical and free-form optics. Today, CGHs are recorded directly with a laser or intermediates masks but allows only recording binary CGHs; binary CGHs are efficient but can reconstruct only pixilated images. We propose to use a Digital Micro-mirror Device (DMD) for writing binary CGHs as well as grayscale CGHs, able to reconstruct fulfilled images. DMD is actually studied at LAM, for generating programmable slit masks in multi-object spectrographs. It is composed of 2048x1080 individually controllable micro-mirrors, with a pitch of 13.68 μm. This is a real-time reconfigurable mask, perfect for recording CGHs. A first setup has been developed for hologram recording, where the DMD is enlightened with a collimated beam and illuminates a photosensible plate through an Offner relay, with a magnification of 1:1. Our set up resolution is 2-3 μm, leading to a CGH resolution equal to the DMD micro mirror size. In order to write and erase CGHs during test procedure or on request, we use a photochromic plate called PUR-GD71-50-ST developed at Politecnico di Milano. It is opaque at rest, and becomes transparent when it is illuminated with visible light, between 500 and 700 nm; then it can be erased by a UV flash. We choose to code the CGHs in equally spaced levels, so called stepped CGH. We recorded up to 1000x1000 pixels CGHs with a contrast greater than 50, knowing that the material is able to reach an ultimate contrast of 1000. A second bench has also been developed, dedicated to the reconstruction of the recorded images with a 632.8nm He-Ne laser beam. Very faithful reconstructions have been obtained. Thanks to our recording and reconstruction set-ups, we have been able to successfully record binary and stepped CGHs, and reconstruct them with a high fidelity, revealing the potential of this method for generating programmable/rewritable stepped CGHs on photochromic materials. | Conference Name: | Advances in Optical and Mechanical Technologies for Telescopes and Instrumentation II | Conference Place: | Edinburgh, UK | Conference Date: | 26 June-1 July, 2016 | URI: | http://hdl.handle.net/20.500.12386/24950 | URL: | https://www.spiedigitallibrary.org/conference-proceedings-of-spie/9912/1/Programmable-CGH-on-photochromic-material-using-DMD/10.1117/12.2234406.full?SSO=1 | ISSN: | 0277-786X | ISBN: | 9781510602038 9781510602045 |
DOI: | 10.1117/12.2234406 | Bibcode ADS: | 2016SPIE.9912E..34A | Fulltext: | open |
Appears in Collections: | 3.01 Contributi in Atti di convegno |
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File | Description | Size | Format | |
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SPIE991234.pdf | PDF editoriale | 1.23 MB | Adobe PDF | View/Open |
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