3 September 2015 Analysis and compensation of moiré effects in fiber-coupled image sensors
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Abstract
Imaging fiber bundles can relay a curved image surface to a conventional at focal plane, effectively providing the curved image sensor needed for some high performance lenses. If the fiber bundle period or image sensor pitch are very different, the system resolution is determined by the oversampled fiber or sensor feature. But crosstalk imposes an approximately 2µm minimum waveguide pitch, and light collection and fabrication constraints impose a lower limit of 1-2µm for the sensor pitch. Maximizing image information leads to some degree of aliasing, which appears in the form of moiré pattern on the raw image sensed. For example, a 30 Mpixel 120° field of view imager using a 1.75µm Bayer filtered CMOS focal plane with 2.5µm pitch fiber bundle yielded images with visible moiré. Here we present a study of moiré effects in fiber-coupled image sensors, including a method for quantitative analysis of moiré, and experimental characterization of the sensors with 1.1µm pixel pitch, the highest spatial resolution in commercially available focal plane arrays. We investigate the effect of exposure time of the sensor, angle of incidence of collimated light, and imaging lens F/# on the raw moiré pattern strength. This study provides guidelines for optimization and operation of high resolution fiber-coupled imagers.
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Salman Karbasi, Salman Karbasi, Nojan Motamedi, Nojan Motamedi, Ashkan Arianpour, Ashkan Arianpour, William M. Mellete, William M. Mellete, Joseph E. Ford, Joseph E. Ford, } "Analysis and compensation of moiré effects in fiber-coupled image sensors", Proc. SPIE 9579, Novel Optical Systems Design and Optimization XVIII, 957910 (3 September 2015); doi: 10.1117/12.2188925; https://doi.org/10.1117/12.2188925
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