Detailed characterization of a mosaic based hyperspectral snapshot imager

Hahn, Robin; Hämmerling, Freya-Elin; Haist, Tobias; Fleischle, David; Schwanke, Oliver; Hauler, Otto; Rebner, Karsten; Brecht, Marc

doi:10.1117/1.oe.59.12.125102

Cited by 12 publications

(10 citation statements)

References 13 publications

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“…Because of this, there ha ve been limited focus on snapshot mosaic HS imaging technologies. Although snapshot mosaic HS imagers do not suffer from severe geometrical distortions, as keystone and smile in push-broom HS imagers, they do present challenges in their optical characterization (Hahn et al, 2020) and radiometric calibration (Guo et al, 2019).…”

Section: Introductionmentioning

confidence: 99%

Calibrating a snapshot mosaic hyperspectral imaging system suitable for static and aerial applications

Zempila¹,

Hamilton²,

Mortimer³

2023

Hyperspectral Imaging and Applications II

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Radiometric calibration of all optical sensors is a key component to achieve high accuracy data, which is traceable to international standards and repeatable through time. This study introduces a hyperspectra l imaging (HSI) system that RAL Space has developed and presents a thorough analysis of the radiometric reflectance calibration chain required for both static and aerial applications, where the HSI system is mounted on a n Unoccupied Aerial System (UAS). RAL Space HSI system comprises two commercially available Ximea snapshot mosaic imagers, one sensitive in the visible (VIS) and the other in the near infrared (NIR) spectral ranges, that are coupled with a dedicated PC and customized LabVIEW code for the capture, process and storage of the raw hyperspectral information (hypercubes). Both imagers are optically characterized for their electrical gain and offset, the vignetting and stray light effects, while the spectral response of each band has also been determined. The corrected digital numbers (DN) are then translated into reflectance values with the use of reflectance standards. For the aerial surveys, an additional step has been developed into the calibration chain that corrects for any changes in ambient illumination during flight with the use of ground based upward-looking measured spectra.Future work will include any correction needed due to temperature dependencies of the calibration chain steps.

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Section: Introductionmentioning

confidence: 99%

Calibrating a snapshot mosaic hyperspectral imaging system suitable for static and aerial applications

Zempila¹,

Hamilton²,

Mortimer³

2023

Hyperspectral Imaging and Applications II

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“…The latter uses an MSFA to acquire spectral information in a single 2D image sensor exposure, similar to RGB cameras. However, MSFA cameras employ larger Color Filter Arrays (CFAs), such as 3 × 3, 4 × 4, or 5 × 5 [27].…”

Section: Introductionmentioning

confidence: 99%

MSFA-Frequency-Aware Transformer for Hyperspectral Images Demosaicing

Zeng¹,

Feng²,

Shaoguang³

et al. 2023

Preprint

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Hyperspectral imaging systems that use multispectral filter arrays (MSFA) capture only one spectral component in each pixel. Hyperspectral demosaicing is used to recover the non-measured components. While deep learning methods have shown promise in this area, they still suffer from several challenges, including limited modeling of non-local dependencies, lack of consideration of the periodic MSFA pattern that could be linked to periodic artifacts, and difficulty in recovering high-frequency details. To address these challenges, this paper proposes a novel demosaicing framework, the MSFA-frequency-aware Transformer network (FDM-Net). FDM-Net integrates a novel MSFA-frequency-aware multi-head self-attention mechanism (MaFormer) and a filter-based Fourier zero-padding method to reconstruct high pass components with greater difficulty and low pass components with relative ease, separately. The advantage of Maformer is that it can leverage the MSFA information and non-local dependencies present in the data. Additionally, we introduce a joint spatial and frequency loss to transfer MSFA information and enhance training on frequency components that are hard to recover. Our experimental results demonstrate that FDM-Net outperforms state-of-the-art methods with 6dB PSNR, and reconstructs high-fidelity details successfully.

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“…Snapshot cameras can rely on a microlens-array optics or on a fixed-filter mosaic deposited on the image sensor. 8,9 In these types of solutions, the pixel resolution of the image sensor is traded off for the spectral resolution. Spatial scanners record spectral data for one point or one line of points at once, but require movement of either the object or the imager to produce a hyperspectral image with spatial information.…”

Section: Introductionmentioning

confidence: 99%

Passive real-time hyperspectral imager based on Fabry-Pérot interferometer filter technology

Kokka,

Holmlund,

Salonen

et al. 2023

Electro-Optical and Infrared Systems: Technology and Applications XX

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This paper presents the system design of a real-time hyperspectral imager based on tunable Fabry-Pérot interferometer (FPI) filter technology. This passive hyperspectral instrument is able to capture spectral data at a rate corresponding to video-like image feed. The instrument is designed to be suitable for handheld operation as well as for missions carried out using uncrewed aerial vehicles.The frame rate of individual spectral channels of an FPI-based camera, and subsequently the acquisition speed of hyperspectral data, depends on the actuation speed of the FPI filter, exposure time of the sensor, data transfer rate, and all delays between the consecutive operations. In order to minimize the delays when switching between the spectral channels, the large FPI of this instrument is enclosed in a low-pressure housing to reduce air resistance, which would otherwise slow down the mechanical movement of the filter. As various applications require different sets of wavelengths and a variable number of spectral channels to be recorded, the imager enables selecting the desired wavelengths programmatically from within the complete spectral range of the instrument. FPI-based hyperspectral cameras produce a full two-dimensional image for each spectral channel. The spatial information contained in the images may be used to compensate for any desired or undesired movement of the imager. The spatial information available for individual channels can also be used for data analysis, and it enables employing conventional machine vision algorithms for example to detect and track the objects of interest.

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Detailed characterization of a mosaic based hyperspectral snapshot imager

Cited by 12 publications

References 13 publications

Calibrating a snapshot mosaic hyperspectral imaging system suitable for static and aerial applications

Calibrating a snapshot mosaic hyperspectral imaging system suitable for static and aerial applications

MSFA-Frequency-Aware Transformer for Hyperspectral Images Demosaicing

Passive real-time hyperspectral imager based on Fabry-Pérot interferometer filter technology

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