A novel dynamic optical low-pass filter

Branko Petljanski

doi:10.1117/12.838921

18 January 2010 A novel dynamic optical low-pass filter

Branko Petljanski

Proceedings Volume 7537, Digital Photography VI; 75370W (2010) https://doi.org/10.1117/12.838921
Event: IS&T/SPIE Electronic Imaging, 2010, San Jose, California, United States

Abstract

Most contemporary still and video cameras employ various optically birefringent materials as optical low-pass filters (OLPF) in order to minimize alias artifacts in the image. Due to the slope characteristics of these filters, camera designers are faced with the choice of either under correcting to maintain image resolution, allowing some aliasing, or eliminating aliases with a more aggressive design that will also compromise the image modulation transfer function (MTF). Furthermore, most OLPFs are designed as optical elements with a frequency response that does not change even if the frequency responses of other elements of the capturing systems are altered. In this paper, we demonstrate the use of a parallel optical window or, alternatively, a rigid mirror positioned between a lens and an imager as an OLPF. Controlled x- and y-axis rotations of the window and the mirror result in a manipulation of the point spread function (PSF) of the system and frequency content of imaged continuous scenes. We evaluate the system MTF when various window functions are used to shape PSF, such as rectangle, triangle, Blackman-Harris etc. We also present results of our experiments when the dynamic OLPF's support and shape are altered to accommodate the optical performance of lenses and imager characteristics.

Citation Download Citation

Branko Petljanski "A novel dynamic optical low-pass filter", Proc. SPIE 7537, Digital Photography VI, 75370W (18 January 2010); https://doi.org/10.1117/12.838921

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KEYWORDS

Modulation transfer functions

Optical filters

Imaging systems

Cameras

Linear filtering

Distance measurement

Filtering (signal processing)

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