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20 February 2017 System-level analysis and design for RGB-NIR CMOS camera
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Proceedings Volume 10110, Photonic Instrumentation Engineering IV; 101100B (2017)
Event: SPIE OPTO, 2017, San Francisco, California, United States
This paper presents system-level analysis of a sensor capable of simultaneously acquiring both standard absorption based RGB color channels (400-700nm, ~75nm FWHM), as well as an additional NIR channel (central wavelength: ~808 nm, FWHM: ~30nm collimated light). Parallel acquisition of RGB and NIR info on the same CMOS image sensor is enabled by monolithic pixel-level integration of both a NIR pass thin film filter and NIR blocking filters for the RGB channels. This overcomes the need for a standard camera-level NIR blocking filter to remove the NIR leakage present in standard RGB absorption filters from ~700-1000nm. Such a camera-level NIR blocking filter would inhibit the acquisition of the NIR channel on the same sensor. Thin film filters do not operate in isolation. Rather, their performance is influenced by the system context in which they operate. The spectral distribution of light arriving at the photo diode is shaped a.o. by the illumination spectral profile, optical component transmission characteristics and sensor quantum efficiency. For example, knowledge of a low quantum efficiency (QE) of the CMOS image sensor above 800nm may reduce the filter’s blocking requirements and simplify the filter structure. Similarly, knowledge of the incoming light angularity as set by the objective lens’ F/# and exit pupil location may be taken into account during the thin film’s optimization. This paper demonstrates how knowledge of the application context can facilitate filter design and relax design trade-offs and presents experimental results.
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Bert Geelen, Nick Spooren, Klaas Tack, Andy Lambrechts, and Murali Jayapala "System-level analysis and design for RGB-NIR CMOS camera", Proc. SPIE 10110, Photonic Instrumentation Engineering IV, 101100B (20 February 2017);

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