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Measurement principle and arrangement for the determination of spectral channel-specific angle dependencies for multispectral resolving filter-on-chip CMOS cameras

: Dittrich, P.-G.; Bichra, M.; Pfützenreuter, C.; Rosenberger, M.; Notni, G.

Fulltext ()

Rosenberger, M. ; Society of Photo-Optical Instrumentation Engineers -SPIE-, Bellingham/Wash.:
Photonics and Education in Measurement Science 2019 : 17-19 September 2019, Jena, Germany
Bellingham, WA: SPIE, 2019 (Proceedings of SPIE 11144)
ISBN: 978-1-5106-2981-3
ISBN: 978-1-5106-2982-0
Paper 111440S, 11 pp.
Conference "Photonics and Education in Measurement Science" <2019, Jena>
Conference Paper, Electronic Publication
Fraunhofer IOF ()

Filter-On-Chip CMOS sensor equipped cameras are a convenient, reliable and affordable approach for the parallel acquisition of spatial and spectral information. The combination of pixel-arranged spectral filter matrices on CMOS sensors increases their integration density and system complexity by several times compared to standard RGB cameras. Due to their system design, these cameras have an increased spectral crosstalk and specific dependencies from the angle of radiation. The paper will show how to develop and set up a measurement arrangement for the characterization of the channel specific spectral sensitivities under different angles of radiation. These characterizations are necessary to develop a more robust model for the camera pixel-value correction to ensure the comparability and reproducibility of the measured values. Therefore, a measurement setup to investigate the influence of the angle of incident radiation on filter-on-chip CMOS sensors was developed. After initial investigations with a setup in which the camera was simply rotated and investigations with a lens and changed f-number confirmed that the angle influence results in a measurable difference in the sensor response, a new measurement arrangement was developed to investigate this behavior more precisely. The developed measurement arrangement allows multispectral resolving image sensors to be radiated with collimated light at reproducible angles of incidence and with adjustable wavelengths. By comparing the measured values with illuminances measured using a calibrated photodiode in the same setup and with the same parameters, it is possible to evaluate the angle dependence based on quantum efficiency curves according to the EMVA 1288 standard. The investigations carried out, the developed principles and the realized semi-automatic measurement arrangement will be shown and explained to characterize the capabilities of multispectral resolving filter-on-chip CMOS sensor equipped cameras for applications in industry and biomedicine.