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Moving refractive optical low pass filter (ROLPF) for digital cameras

: Schöberl, M.; Ernst, J.; Schnurrer, W.; Fößel, S.; Kaup, A.


Imai, F.H. ; Society of Photo-Optical Instrumentation Engineers -SPIE-, Bellingham/Wash.; Society for Imaging Science and Technology -IS&T-:
Digital photography VII. 7th Annual Digital Photography Conference 2011 : 24 - 25 January 2011, San Francisco, California, United States; Part of IS&T/SPIE electronic imaging, science and technology
Bellingham, WA: SPIE, 2011 (Proceedings of SPIE 7876)
ISBN: 978-0-8194-8413-0
Paper 78760Z
Digital Photography Conference <7, 2011, San Francisco/Calif.>
Symposium on Electronic Imaging, Science and Technology (IS&T) <2011, San Francisco/Calif.>
Conference Paper
Fraunhofer IIS ()

As with any sampling process, image acquisition is subject to spatial domain aliasing. Many designs of optical filters have been proposed that reduce the amount of aliasing in image acquisition. Still, the most common systems are based on birefringent optical materials. Unfortunately, these filters are expensive and the actual filter response curve can only partially be influenced. We propose a new refractive optical low-pass filter (ROLPF) based on refraction at a structured glass plate. The transparent plate features a single surface with a defined structure. This leads to refraction and will lead to a modified light distribution on the sensor. The plate is placed in front of the sensor and is moved in the image sensor plane during an exposure. This causes an averaging process and results in a spatial domain filtering. The response curve of this setup can be controlled by designing the gradient of the surface. This filter will be easy to manufacture, it offers a true low-pass characteristic which can be specifically designed and the bandwidth can be adjusted at runtime by variation of the distance to the sensor.