Filter width affects the transmittance of patterned all-dielectric Fabry-Perot filters
2021; 46 (23): 5926-5929
Thin-film all-dielectric Fabry-Perot filters can nowadays be patterned onto pixels of commercial imaging sensors used for spectral imaging. For these patterned filters, standard transfer-matrix thin-film calculations fail to predict their angular dependency. This Letter attributes the discrepancy to the finite filter size and is also, to my knowledge, the first study to analyze this for patterned all-dielectric Fabry-Perot filters. An angular spectrum approach that enables prediction without full knowledge of the filter design is introduced. In addition, the contribution of diffraction at normal incidence is characterized by a single dimensionless parameter. Knowing that patterned filter size matters and having a method to efficiently simulate its effect can guide ongoing miniaturization efforts and filter design.
View details for DOI 10.1364/OL.442737
View details for Web of Science ID 000722896900037
View details for PubMedID 34851925
Thin-film interference filters illuminated by tilted apertures
OPTICAL SOC AMER. 2020: A112–A122
Thin-film interference filters can be illuminated by a circular aperture at different angles. Each situation produces a different transmittance spectrum. We present an analytical model that, for small tilt angles, predicts the change in transmittance for an arbitrary position of the filter in three-dimensional space. The model is extended to take into account higher-order harmonics. We also derive a formula to predict the change in central wavelength, and we validate our results by comparison with thin-film transfer-matrix calculations. A key property of our approach is that the model can be combined with empirical data to predict the transmittance without knowing the filter design.
View details for DOI 10.1364/AO.59.00A112
View details for Web of Science ID 000526522300018
View details for PubMedID 32225362
- Exit pupil localization to correct spectral shift in thin-film Fabry-Perot spectral cameras OSA CONTINUUM 2019; 2 (7): 2217–26
Vignetted-aperture correction for spectral cameras with integrated thin-film Fabry-Perot filters
2019; 58 (7): 1789–99
Spectral cameras with integrated thin-film Fabry-Perot filters have become increasingly important in many applications. These applications often require the detection of spectral features at specific wavelengths or to quantify small variations in the spectrum. This can be challenging since thin-film filters are sensitive to the angle of incidence of the light. In prior work, we modeled and corrected for the distribution of incident angles for an ideal finite aperture. Many real lenses, however, experience vignetting. Therefore, in this paper, we generalize our model to the more common case of a vignetted aperture, which changes the distribution of incident angles. We propose a practical method to estimate the model parameters and correct undesired shifts in measured spectra. This is experimentally validated for a lens mounted on a visible-to-near-infrared spectral camera.
View details for DOI 10.1364/AO.58.001789
View details for Web of Science ID 000460120600033
View details for PubMedID 30874220
Finite aperture correction for spectral cameras with integrated thin-film Fabry-Perot filters
2018; 57 (26): 7539–49
Spectral cameras with integrated thin-film Fabry-Perot filters enable many different applications. Some applications require the detection of spectral features that are only visible at specific wavelengths, and some need to quantify small spectral differences that are undetectable with RGB color cameras. One factor that influences the central wavelength of thin-film filters is the angle of incidence. Therefore, when light is focused from an imaging lens onto the filter array, undesirable shifts in the measured spectra are observed. These shifts limit the use of the sensor in applications that require fast lenses or lenses with large chief ray angles. To increase flexibility and enable new applications, we derive an analytical model that explains and can correct the observed shifts in measured spectra. The model includes the size of the aperture and physical position of each filter on the sensor. We experimentally validate the model with two spectral cameras: one in the visible and near-infrared region and one in the short wave infrared region.
View details for DOI 10.1364/AO.57.007539
View details for Web of Science ID 000444085500015
View details for PubMedID 30461824
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