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17 - Plenoptic Cameras
- from Part III - Systems and Applications
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- By Andreas Tünnermann, Friedrich Schiller University Jena, Germany, Sylvia Gebhardt, Fraunhofer Institute for Ceramic Technologies and Systems, Dresden, Germany, Henning Fouckhardt, University of Kaiserslautern
- Edited by Hans Zappe, Albert-Ludwigs-Universität Freiburg, Germany, Claudia Duppé, Albert-Ludwigs-Universität Freiburg, Germany
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- Book:
- Tunable Micro-optics
- Published online:
- 05 December 2015
- Print publication:
- 17 December 2015, pp 417-438
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- Chapter
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Summary
Plenoptic cameras are hybrid imaging systems combining a microlens array with a larger objective lens. In this chapter, we examine the optical limits of these systems and describe techniques to expand them. Before we do so, we start with providing an overview of the history, terminology and capabilities of plenoptic cameras.
History of Light Field Capturing
Plenoptic imaging was invented multiple times during the history of photography, each time changing its name and physical form. Initially, it was called integral photography. The first system was realised with photographic film by the Franco-Luxembourgian scientist and inventor Gabriel Lippmann at the Sorbonne (Lippmann 1908). An integral camera is equipped with multiple lenses arranged side by side in a square grid. Each lens creates a unique image on the film. Each image is slightly different from that of its neighbour. Like in stereoscopy, this difference is caused by the relative displacement of the lenses, an effect known as parallax.
In Lippmann's time, the production and alignment of the lenses was a manual and error-prone process. Imaging quality and light sensitivity were poor. Hence, Lippmann and his assistants could only build lab prototypes. Because no computing technology to process the images was available, the developed film was used as a projection slide, with another array of lenses as the imaging optics. Projection superimposed the individual images optically to form an integral image, which gives the process its name. Rather than being projected on a screen, the image is viewed directly. In the integral image, the observer could perceive depth in the recorded scene through stereoscopy and motion parallax. Throughout the twentieth century, Lippmann's idea was re-discovered every few decades (Ives 1930, Dudnikov 1970), advancing theory and manufacturing technology each time. The current renaissance started in the 1990s and was made possible by contributions from different fields of science and engineering, each with its unique terminology.
Now, light field is the commonly accepted term for the light quantities recorded from a scene. It is an abstraction of the electromagnetic field that describes both intensity and directional distribution of light for every three-dimensional (3D) point in space, but discards polarisation and phase. The term was popularised in computer graphics by Levoy & Hanrahan (1996). Light fields were first applied as a more robust starting point to the problem of view interpolation in image based rendering (Shum & Kang 2000).
High Aspect Ratio Microstructures in LiNbO3 Produced by Ion Beam Enhanced Etching
- Frank Schrempel, Thomas Gischkat, Holger Hartung, Ernst Bernhard Kley, Werner Wesch, Andreas Tünnermann
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- Journal:
- MRS Online Proceedings Library Archive / Volume 908 / 2005
- Published online by Cambridge University Press:
- 26 February 2011, 0908-OO16-01
- Print publication:
- 2005
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- Article
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This work presents data on damage evolution, volume expansion and etching behavior of LiNbO3 irradiated with Ar+-ions as a function of irradiation and etching conditions. Single crystals of x- and z-cut LiNbO3 were irradiated at room temperature and 15 K using Ar-ions with energies between 60 and 600 keV and ion fluences between 5 × 1012 and 1 × 1015 cm-2. The damage formation investigated with RBS channeling analysis depends on the crystal cut as well as on the irradiation temperature. Irradiation of z-cut material at 300 K causes complete amorphization at 0.4 dpa (displacements per target atom). In contrast 0.27 dpa are sufficient to amorphize the x-cut LiNbO3. Irradiation at 15 K reduces the number of displacements per atom necessary for amorphization to 0.18 dpa. To study the etching behavior ∼500 nm thick amorphous layers were generated via multiple irradiations with Ar+-ions. Etching was performed in HF-solution of different concentration and at different temperatures. The influence of the irradiation and etching conditions on damage formation and etching of LiNbO3 is discussed. In conclusion, negligible etching of the perfect crystal, high etching rates and high contrast of Ion Beam Enhanced Etching (IBEE) allow the realization of high aspect ratio microstructures in LiNbO3.