Torbjørn Skauli

• Retselis, Anastasios-Faidon; Knutsen, Elise Wright; Holdcroft, Sam; Viet, Shayla; Wahlén, Rebecka & Virdis, Mario [Vis alle 19 forfattere av denne artikkelen] (2026). CENSSAT-1: A space weather mission and an educational platform. I Detrell, Gisela; Alarcia, Ramón María García; Messina, Vincenzo & Kinnaird, Alexander (Red.), Proceedings of the 5th Symposium on Space Educational Activities (SSEA). Technical University of Munich. s. 852–857. doi: 10.14459/2026MD1857465. Fulltekst i vitenarkiv Vis sammendrag

  The Symposium on Space Educational Activities (SSEA), organised by the European Space Agency’s Education Office, provides a forum for university students, professionals working in education, and other professionals in industry or agencies to present and discuss their experiences organising, running and/or participating in Educational Activities related to Space. After successful past events in Padova (2015), Budapest (2018), Leicester (2019), and Barcelona (2022), the 5th SSEA was held in April 2026 (the 8th, 9th, and 10th) in the TUM Aerospace Campus in Willy-Messerschmitt-Strasse 5, Taufkirchen, Germany. The local organisation team was led by the Technical University of Munich (TUM), involving Professors, PostDocs, PhD Candidates, and Master’s and Bachelor’s students, in close collaboration with the Bavarian aerospace ecosystem partners.

• Selnesaunet, Gard Momrak & Skauli, Torbjørn (2025). Measuring the pixel sampling point spread function and effective fill factor of thermal cameras using tomographic reconstruction. Optical Engineering: The Journal of SPIE. ISSN 0091-3286. 64(12). doi: 10.1117/1.OE.64.12.123104. Fulltekst i vitenarkiv Vis sammendrag

  Spatial resolution in thermal imaging systems is commonly characterized by metrics such as pixel count, instantaneous field of view, or modulation transfer function. However, these traditional approaches are normally given as one-dimensional resolution estimates and overlook variations in intrapixel responsivity. We present a tomographic method for measuring the full two-dimensional pixel sampling point spread function in thermal cameras, enabling assessment of both spatial resolution and intrapixel response uniformity, including fill factor effects. By scanning a sub-pixel infrared line source across a pixel at multiple angles and applying filtered back-projection, the 2D spatial response of each pixel can be reconstructed. This method has been demonstrated on an uncooled micro-bolometer camera for the long-wave infrared band and a cooled camera for the mid-wave infrared band. The results reveal anisotropic resolution and intrapixel nonuniformities not captured by conventional techniques. Effective fill factor (EFF) values are found to differ significantly between the two cameras (0.963 versus 0.996), highlighting performance differences in scenes with subpixel contrasts or thermal hotspots. It is shown that the worst-case magnitude of the resulting image artifacts can be larger than the specified noise-equivalent temperature difference (NETD) by an order of magnitude or more. It is argued that the EFF may be an informative addition to camera specifications.

• Skauli, Torbjørn (2025). Quantifying imaging imperfections resulting from nonideal fill factor and similar pixel-scale responsivity nonuniformities. Optics Express. 33(15), s. 32140–32154. doi: 10.1364/OE.558153. Fulltekst i vitenarkiv Vis sammendrag

  Image sensors can exhibit variations in the responsivity to light across the area of individual pixels. If the responsivity is uniform apart from a region with zero sensitivity, the situation is well described by the conventional concept of a fill factor, which gives the fraction of sensitive area in the pixel. In many practical cases, such responsivity variations are gradual, due to effects such as photon scattering or photoelectron diffusion between neighboring pixels. When characterizing the spatial responsivity of a complete camera, optical blur will tend to smear out pixel-scale variations. This paper generalizes the concept of a fill factor to cover such gradual sensitivity variations within a pixel, for an image sensor as well as for a complete camera. The core idea is that the effective fill factor (EFF) is the fill factor of a box-shaped pixel response that would produce the same maximum error in estimated reflectance as the actual camera response, when viewing a reflective scene. The resulting EFF is derived from the pixel sampling point spread function and sampling interval. It has a simple relation to an upper bound on the error in reflectance estimated from a reflected-light image. The EFF also has a simple relation to the average error in the total signal from a point source. It is noted that the spatial variation causing these image artifacts is specifically the variation of signal loss across the pixel. The EFF can supplement specification of many camera types, including thermal cameras as well as color and multispectral cameras based on filter arrays.

• Perry, David; Conran, David & Skauli, Torbjørn (2025). Selection of robust metrics for the position and width of hyperspectral response functions via a simulation approach. Applied Optics. ISSN 1559-128X. 64(2), s. 304–316. doi: 10.1364/AO.544074. Fulltekst i vitenarkiv
• Lofstad-Lie, Victoria; Aarseth, Bjørn Lupton; Roosloot, Nathan Abel; Marstein, Erik Stensrud & Skauli, Torbjørn (2024). Modeling Cost-Effectiveness of Photovoltaic Module Replacement Based on Quantitative Assessment of Defect Power Loss. Solar. 4(4), s. 728–743. doi: 10.3390/solar4040034. Fulltekst i vitenarkiv Vis sammendrag

  The degradation of solar photovoltaic (PV) modules over time, which are aggravated by defects, significantly affects the performance of utility-scale PV parks. This study presents a quantitative assessment of the power loss from module defects and evaluates the cost-effectiveness of replacing defective modules at various stages of degradation. A module test site was established in Norway with six different defects, and continuous thermographic monitoring, combined with light IV measurements and electroluminescence (EL) imaging, provides partial support for further calculations on the long-term effects of the defects. The cumulative module energy loss is calculated over a 25-year park lifespan under both Norwegian and Chilean environmental conditions, with the latter representing higher solar irradiation levels. The energy gain from replacing the defective modules at various stages of degradation is compared to the costs of replacement, both for infant-life failures and mid-life failures. It is likely not beneficial to replace minor infant-life defects of 1% power loss in low-irradiation regions like Norway. For Chilean conditions, it can be cost-effective, but primarily if the module is replaced around mid park life, which gives a larger yield when replaced with a new module. For more severe defects of 10% loss, the replacement gain is above the replacement cost for high-irradiation locations, and replacing the 33% power loss defect is cost-effective for both locations, even when discovered late in the park lifetime. It is primarily beneficial to replace mid-life defects in high-irradiation locations.

• Virdis, Mario; Knutsen, Elise Wright; Kohfeldt, Anja; Jebali, Ramsey Al; Teodoro, Luis Filipe Alves & Skauli, Torbjørn [Vis alle 12 forfattere av denne artikkelen] (2024). University of Oslo CENSSAT-1 mission concept. Proceedings of the International Astronautical Congress. ISSN 0074-1795. Fulltekst i vitenarkiv
• Selnesaunet, Gard Momrak; Henriksen, Marie Bøe & Skauli, Torbjørn (2024). Performance comparison of COTS-based hyperspectral imagers using detailed point spread function measurements. Journal of Applied Remote Sensing. 18(4). doi: 10.1117/1.JRS.18.047503. Fulltekst i vitenarkiv Vis sammendrag

  Hyperspectral imaging is a rapidly growing field that utilizes a diverse range of camera designs. It has been demonstrated that hyperspectral cameras can be constructed from commercial off-the-shelf (COTS) components, offering the potential for low-cost and widespread use. However, these COTS-based systems may face performance limitations due to optics not being optimized for hyperspectral purposes. Characterizing and comparing the performance of hyperspectral cameras is complex, a challenge recognized by the ongoing development of the IEEE P4001 standard. Specifically, the spatial coregistration among different spectral bands is crucial for the quality and integrity of the recorded spectra in each pixel. The proper evaluation of coregistration and resolution necessitates the measurement of the point spread function for each band. We use measurements of the full 2D sampling point spread function (SPSF) to compare the performance of two hyperspectral imagers (HSIs) built from COTS components: the engineering model of the hyperspectral camera onboard the Hyperspectral Cubesat for Ocean Observation-1 cubesat and an extremely compact HSI developed for drone flights. In addition, the line spread functions across and along the track, keystone distortion, and coregistration errors are derived from the SPSFs. A simplified measurement scheme is also tried and found to provide fair accuracy for the tested cameras. The results highlight the importance of measuring the spatial SPSF for characterizing and comparing different hyperspectral cameras. Results also show that good spectral integrity can be achieved through spatial binning, which of course requires a tradeoff against spatial resolution. Nonetheless, it is evident that such low-cost systems can offer useful capabilities.

• Lofstad-Lie, Victoria; Marstein, Erik Stensrud; Simonsen, Aleksander & Skauli, Torbjørn (2022). Cost-Effective Flight Strategy for Aerial Thermography Inspection of Photovoltaic Power Plants. IEEE Journal of Photovoltaics. ISSN 2156-3381. 12(6). doi: 10.1109/JPHOTOV.2022.3202072. Fulltekst i vitenarkiv Vis sammendrag

  Thermography from unmanned aerial vehicles (UAV) is widely used for module condition surveys and defect detection in solar (photovoltaic) power plants. This article presents an optimized defect inspection procedure in which a two-stage autonomous flight strategy is adopted to reduce the operation time, and thereby the cost. The first stage is a fast high-altitude flight for rapid coverage of the entire plant. The resolution on the modules is then somewhat degraded, but adequate for detection of possible defect locations. In the second stage, an optimized flight path is calculated to revisit and image only the detected locations from a lower altitude, where the resolution is sufficient for the classification of defects. This concept is studied through simulations of different plant geometries and defect densities. The simulations are supported by actual data, including a plant-scale survey. The proposed strategy is shown to have the potential for significant savings in operation time, on the order of 60% in the experimental case with 2% module defects. Commonly reported defect densities of 0.5% to 1% will give even larger savings. The inspection strategy is shown to be especially beneficial for plant geometries representative of high latitudes.

• Skauli, Torbjørn (2022). A Performance Characteristic for Net Light Collection in Hyperspectral and Conventional Cameras: A*. IEEE Transactions on Geoscience and Remote Sensing. ISSN 0196-2892. doi: 10.1109/TGRS.2022.3228071. Fulltekst i vitenarkiv Vis sammendrag

  The signal-to-noise ratio of modern cameras under normal operating conditions tends to be limited by “photon noise” originating from the random arrival of photons. For best signal-to-noise ratio, it is desirable to collect as much light as possible, and to avoid losses internally in the camera. There is currently no widely accepted metric for the resulting net light collection, which depends on many aspects of camera design. The IEEE Standards Association P4001 group is developing a standard for hyperspectral imaging, including ways to fully specify camera performance in an efficient way. Motivated by P4001 requirements, this work proposes to specify the net light collection in a single quantity, denoted A∗ , essentially defined as the product of nominal geometrical étendue, optics transmission, and detector quantum efficiency. It is shown how A∗ can be physically interpreted as the detector pixel area of an equivalent lossless camera whose exit pupil subtends 1sr. This article discusses how this quantity can be used as a figure of merit applying to hyperspectral cameras as well as to conventional multispectral and broadband cameras and other sensing systems employing imaging optics.

• Haavardsholm, Trym Vegard; Opsahl, Thomas Olsvik; Skauli, Torbjørn & Stahl, Annette (2022). Compact multimodal multispectral sensor system for tactical reconnaissance. Proceedings of SPIE, the International Society for Optical Engineering. ISSN 0277-786X. doi: 10.1117/12.2632701. Fulltekst i vitenarkiv Vis sammendrag

  Multispectral imaging is an attractive sensing modality for small unmanned aerial vehicles (UAVs) in numerous military and civilian applications such as reconnaissance, target detection, and precision agriculture. Cameras based on patterned filters in the focal plane, such as conventional colour cameras, represent the most compact architecture for spectral imaging, but image reconstruction becomes challenging at higher band counts. We consider a camera configuration where six bandpass filters are arranged in a periodically repeating pattern in the focal plane. In addition, a large unfiltered region permits conventional monochromatic video imaging that can be used for situational awareness (SA), including estimating the camera motion and the 3D structure of the ground surface. By platform movement, the filters are scanned over the scene, capturing an irregular pattern of spectral samples of the ground surface. Through estimation of the camera trajectory and 3D scene structure, it is still possible to assemble a spectral image by fusing all measurements in software. The repeated sampling of bands enables spectral consistency testing, which can improve spectral integrity significantly. The result is a truly multimodal camera sensor system able to produce a range of image products. Here, we investigate its application in tactical reconnaissance by pushing towards on-board real-time spectral reconstruction based on visual odometry (VO) and full 3D reconstruction of the scene. The results are compared with offline processing based on estimates from visual simultaneous localisation and mapping (VSLAM) and indicate that the multimodal sensing concept has a clear potential for use in tactical reconnaissance scenarios.

• Lofstad-Lie, Victoria; Marstein, Erik Stensrud; Simonsen, Aleksander & Skauli, Torbjørn (2021). Cost-effective flight strategy for aerial thermography inspection of photovoltaic power plants. I Angus, Rockett (Red.), 2021 IEEE 48th Photovoltaic Specialists Conference (PVSC). IEEE (Institute of Electrical and Electronics Engineers). ISSN 9781665419222. s. 0023–0025. doi: 10.1109/PVSC43889.2021.9518710. Fulltekst i vitenarkiv Vis sammendrag

  Thermography from an unmanned aerial vehicle (UAV) offers efficient fault inspection in solar parks. This paper presents an optimized fault detection procedure, including a two-stage autonomous flight strategy. The first stage images the entire park quickly at low resolution, flying fast at high altitude to detect possible faults. In the second stage, the detections are imaged at higher resolution, by flying an optimized path at lower altitude, for fault classification. Based on actual data, including a park-scale survey, this strategy is shown to have potential for significant savings in operation time, on the order of 70% or more, at realistic fault densities.

• Skauli, Torbjørn (2021). Characterizing the dynamic range of a hyperspectral camera. Proceedings of SPIE, the International Society for Optical Engineering. ISSN 0277-786X. doi: 10.1117/12.2588305. Fulltekst i vitenarkiv Vis sammendrag

  The dynamic range of a hyperspectral camera can have a strong impact on the quality and integrity of the collected spectra. For the image sensor chip alone, the dynamic range is the ratio between the saturation level and the noise floor, set by full well capacity and readout noise respectively. In a complete hyperspectral camera, the raw signal level varies with the wavelength-dependent detector quantum efficiency, optics transmission, and illumination, as well as with the optical bandwidth. In practice, different parts of the spectrum will tend to have the highest or lowest signal level, and will most easily reach the saturation level or noise floor, respectively. It is shown that to define a dynamic range for a hyperspectral camera in the reflective spectral domain, the wavelength dependence of the camera light collection efficiency must be taken into account. A more application-oriented dynamic range can be defined by additionally assuming a shape of the illumination spectrum representative of a particular application.

• Skauli, Torbjørn (2020). Specifying radiometric performance of hyperspectral and conventional cameras: A minimal set of independent characteristics. Proceedings of SPIE, the International Society for Optical Engineering. ISSN 0277-786X. doi: 10.1117/12.2559670. Fulltekst i vitenarkiv Vis sammendrag

  The radiometric performance of cameras is customarily characterized and specified in terms of component properties such as F-number and readout noise. This paper considers the camera as an integrated unit and derives characteristics suitable for specifying noise, throughput and saturation as determined from the overall input-to-output performance. A conventional model of signal and noise is reformulated into a simpler "equivalent camera" model with the same radiometric performance, constrained to have a lossless lens with detector-side pupil subtending 1 steradian, and a detector with a peak quantum efficiency (QE) of 1. The small parameter set of this model can then be determined with the camera treated as a "black box", relevant for verification of camera specifications. The net light collection of the real camera is expressed by the detector area of the equivalent camera, denoted A* , as well as the wavelength dependence of its QE, denoted η* (λ). The noise floor due to readout noise can be expressed for a particular camera as a noise equivalent spectral radiance (NESR). For comparison of cameras with different bandwidths, it is shown that a comparative figure of merit, which is also independent of integration time, is the "noise equivalent radiance dose" (NERD). For a hyperspectral camera, the model parameters can be determined with a simple broadband source, while cameras with broad spectral response require measurements with tunable monochromatic light. The treatment also applies to spectrometers. Reference is made to D*, a well-established figure of merit for detectors, and it is argued that A*,η* (λ) and NERD are analogous figures of merit for camera properties.

• Haavardsholm, Trym Vegard; Skauli, Torbjørn & Stahl, Annette (2020). Multimodal Multispectral Imaging System for Small UAVs. IEEE Robotics and Automation Letters. ISSN 2377-3766. 5(2). doi: 10.1109/LRA.2020.2967301. Fulltekst i vitenarkiv Vis sammendrag

  Multispectral imaging is an attractive sensing modality for small unmanned aerial vehicles (UAVs) in numerous applications. The most compact spectral camera architecture is based on spectral filters in the focal plane. Vehicle movement can be used to scan the scene using multiple bandpass filters arranged perpendicular to the flight direction. With known camera trajectory and scene structure, it is possible to assemble a spectral image in software. In this letter, we demonstrate the feasibility of a novel concept for low-cost wide area multispectral imaging with integrated spectral consistency testing. Six bandpass filters are arranged in a periodically repeating pattern. Since different bands are recorded at different times and in different viewing directions, there is a risk of obtaining spectral artifacts in the image. We exploit the repeated sampling of bands to enable spectral consistency testing, which leads to significantly improved spectral integrity. In addition, an unfiltered region permits conventional 2D video imaging that can be used for image-based navigation and 3D reconstruction. The proposed multimodal imaging system was tested on a UAV in a realistic experiment. The results demonstrate that spectral reconstruction and consistency testing can be performed by image processing alone, based on visual simultaneous localization and mapping (VSLAM).

• Skauli, Torbjørn & Torkildsen, Hans Erling (2019). Simplified measurement of point spread functions of hyperspectral cameras for assessment of spatial coregistration. Proceedings of SPIE, the International Society for Optical Engineering. ISSN 0277-786X. doi: 10.1117/12.2520219. Fulltekst i vitenarkiv Vis sammendrag

  In multi- and hyperspectral imaging, spatial coregistration of the point spread functions (PSFs) of all bands within each pixel is critical for the integrity of measured spectra. There is a need to define a standardized method for characterizing coregistration error. We propose a method that estimates PSFs from the product of line spread functions (LSFs) recorded in two orthogonal directions. Coregistration is then evaluated according to the PSF difference metric [T. Skauli, Opt. Expr. vol. 20, p. 918 (2012)]. Experimental results on two pushbroom hyperspectral cameras show good correspondence with measurements based on the full PSF, provided that LSF scan directions are aligned with axes of symmetry in the optics. Even a maximally unfavourable choice of scan directions gives meaningful estimates of coregistration error. The proposed method may have potential as a standard for coregistration characterization

• Torkildsen, Hans Erling & Skauli, Torbjørn (2018). Measurement of point spread function for characterization of coregistration and resolution: Comparison of two commercial hyperspectral cameras. Proceedings of SPIE, the International Society for Optical Engineering. ISSN 0277-786X. doi: 10.1117/12.2305503. Fulltekst i vitenarkiv Vis sammendrag

  For spectral cameras, the spatial resolution and coregistration of bands are important performance characteristics. The paper discusses how these can be quantified in a way that is relevant for the spectroscopic processing step which is at the beginning of most spectral image analysis methods. It is argued that the most appropriate measure of resolution may be the ensquared energy of the mean point spread function (PSF) within the specified pixel field of view. For spatial coregistration, it is argued that a previously proposed coregistration metric is well suited, by characterizing the full shape and position differences between PSFs of different bands. A relatively simple method for imaging the PSF is demonstrated, based on tomographic reconstruction from line spread functions measured in different directions. The method is used to characterize two presumably comparable commercial hyperspectral cameras, a SpecIm PFD dating from 2012 and a HySpex VNIR-1600 dating from 2016. The measurements reveal significant differences, but it is pointed out that the present measurements by themselves do not constitute a proper comparison of the camera types. The main point made in the paper is that full characterization of the PSF in all bands is possible with moderate experimental effort, and provides clarifying measurements of actual camera performance.

• Arisholm, Gunnar; Skauli, Torbjørn & Landrø, Stig Endre (2018). Combined range ambiguity resolution and noise reduction in lidar signal processing. Optical Engineering: The Journal of SPIE. ISSN 0091-3286. doi: 10.1117/1.OE.57.7.073103. Fulltekst i vitenarkiv Vis sammendrag

  When the interval between transmitted pulses is shorter than the time of flight, it is not straightforward for a lidar to determine the distance uniquely. We present a method that uses varying pulse intervals, constructs a set of tentative point positions for each received pulse, and exploits the clustering of such tentative points to determine the correct distance with high probability. The clustering of true points also helps suppress noise pulses, even in a regime where the number of noise pulses is far greater than the number of true return pulses. It is then possible to use a detection threshold close to the noise level.

• Hovland, Harald & Skauli, Torbjørn (2018). Thermal infrared reference sources fabricated from low-cost components and materials. Proceedings of SPIE, the International Society for Optical Engineering. ISSN 0277-786X. doi: 10.1117/12.2306330. Fulltekst i vitenarkiv Vis sammendrag

  Mass markets, including mobile phones and automotive sensors, drive rapid developments of imaging technologiestoward high performance, low cost sensors, even for the thermal infrared. Good infrared calibration blackbody sourceshave remained relatively costly, however. Here we demonstrate how to make low-cost reference sources, makingquantitative infrared radiometry more accessible to a wider community. Our approach uses ordinary constructionmaterials combined with low cost microcontrollers, digital temperature sensors and foil heater elements from massmarket3D printers. Blackbodies are constructed from a foil heater of some chosen size and shape, attached to the back ofa similarly shaped aluminum plate coated with commercial black paint, which normally exhibits high emissivity. Theemissivity can be readily checked by using a thermal imager to view the reflection of a hot object. A digital temperaturesensor is attached to the back of the plate. Thermal isolation of the backside minimizes temperature gradients through theplate, ensuring correct readings of the front temperature. The isolation also serves to minimize convection gradients andkeeps power consumption low, which is useful for battery powered operation in the field. We demonstrate surfaceblackbodies (200×200 mm²) with surface homogeneities as low as 0.1°C at 100°C. Homogeneous heating and lowthermal mass provides for fast settling time and setup/pack-down time. The approach is scalable to larger sizes by tiling,enabling portable and foldable square-meter-size or larger devices.

• Torkildsen, Hans Erling & Skauli, Torbjørn (2018). Full characterization of spatial coregistration errors and spatial resolution in spectral imagers. Optics Letters. ISSN 0146-9592. doi: 10.1364/OL.43.003814. Fulltekst i vitenarkiv Vis sammendrag

  For multi- and hyperspectral imagers, the integrity of the spectral information depends critically on the spatial coregistration between bands. There is at present no commonly accepted way to fully specify coregistration performance. This Letter shows how a relatively simple measurement technique can be used to form sharp images of the point spread function (PSF) in all bands, yielding information about spatial coregistration, as well as spatial resolution. A previously proposed metric is applied to characterize coregistration in terms of PSF similarity between bands. Resolution is characterized by ensquared energy. Two commercial hyperspectral cameras with nominally similar specifications are compared, and turn out to have large differences in their actual performance. The results, and the relative simplicity of the measurement, suggest that the method is suitable as a standardized performance test.

• Skauli, Torbjørn (2017). Feasibility of a standard for full specification of spectral imager performance. Proceedings of SPIE, the International Society for Optical Engineering. ISSN 0277-786X. doi: 10.1117/12.2262785. Fulltekst i vitenarkiv Vis sammendrag

  The current state of the art of specifying spectral imagers falls short of what is needed. Commercial datasheets do not adequately reflect the performance of hyperspectral imagers offered as standard products. In particular, imperfections such as coregistration error, noise performance and stray light are rarely well specified. A standardized way to specify spectral imagers would benefit both developers and users of such instruments. The paper reviews the many different characteristics that are needed to describe various aspects of imager performance, and discusses possible ways to form figures of merit relevant to application performance. In particular, the product of quantum efficiency, optics transmission and nominal throughput (étendue) is shown to be a good figure of merit for radiometric performance. A list of about 30 characteristics is suggested as a standard for a complete specification of spectral imagers. For some characteristics, notably coregistration, it is necessary to establish a standardized measurement methodology.

• Torkildsen, Hans Erling; Haavardsholm, Trym Vegard; Opsahl, Thomas Olsvik; Datta, Urmila; Skaugen, Atle & Skauli, Torbjørn (2016). Compact multispectral multi-camera imaging system for small UAVs. Proceedings of SPIE, the International Society for Optical Engineering. ISSN 0277-786X. doi: 10.1117/12.2224495. Fulltekst i vitenarkiv Vis sammendrag

  Cameras with filters in the focal plane provide the most compact solution for multispectral imaging. A small UAV can carry multiple such cameras, providing large area coverage rate at high spatial resolution. We investigate a camera concept where a patterned bandpass filter with six bands provides multiple interspersed recordings of all bands, enabling consistency checks for improved spectral integrity. A compact sensor payload has been built with multiple cameras and a data acquisition computer. Recorded imagery demonstrates the potential for large area coverage with good spectral integrity. © (2016) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.

• Skauli, Torbjørn; Torkildsen, Hans Erling; Nicolas, Stephane; Opsahl, Thomas Olsvik; Haavardsholm, Trym Vegard & Kåsen, Ingebjørg [Vis alle 7 forfattere av denne artikkelen] (2014). Compact camera for multispectral and conventional imaging based on patterned filters. Applied Optics. ISSN 1559-128X. doi: 10.1364/AO.53.000C64. Fulltekst i vitenarkiv Vis sammendrag

  A multispectral camera concept is presented. The concept is based on using a patterned filter in the focal plane, combined with scanning of the field of view. The filter layout has stripes of different bandpass filters extending orthogonally to the scan direction. The pattern of filter stripes is such that all bands are sampled multiple times, while minimizing the total duration of the sampling of a given scene point. As a consequence, the filter needs only a small part of the area of an image sensor. The remaining area can be used for conventional 2D imaging. A demonstrator camera has been built with six bands in the visible and near infrared, as well as a panchromatic 2D imaging capability. Image recording and reconstruction is demonstrated, but the quality of image reconstruction is expected to be a main challenge for systems based on this concept. An important advantage is that the camera can potentially be made very compact, and also low cost. It is shown that under assumptions that are not unreasonable, the proposed camera concept can be much smaller than a conventional imaging spectrometer. In principle, it can be smaller in volume by a factor on the order of several hundred while collecting the same amount of light per multispectral band. This makes the proposed camera concept very interesting for small airborne platforms and other applications requiring compact spectral imagers.

• Rousset-Rouviere, Laurent; Coudrain, Christophe; Fabre, Sophie; Poutier, Laurent; Løke, Trond & Fridman, Andrei [Vis alle 10 forfattere av denne artikkelen] (2014). SYSIPHE system: A state of the art airborne hyperspectral imaging system. Initial results from the first airborne campaign. Proceedings of SPIE, the International Society for Optical Engineering. ISSN 0277-786X. doi: 10.1117/12.2066643. Fulltekst i vitenarkiv Vis sammendrag

  SYSIPHE is an airborne hyperspectral imaging system, result of a cooperation between France (Onera and DGA) and Norway (NEO and FFI). It is a unique system by its spatial sampling -0.5m with a 500m swath at a ground height of 2000m- combined with its wide spectral coverage -from 0.4μm to 11.5μm in the atmospheric transmission bands. Its infrared component, named SIELETERS, consists in two high étendue imaging static Fourier transform spectrometers, one for the midwave infrared and one for the longwave infrared. These two imaging spectrometers are closely similar in design, since both are made of a Michelson interferometer, a refractive imaging system, and a large IRFPA (1016x440 pixels). Moreover, both are cryogenically cooled and mounted on their own stabilization platform which allows the line of sight to be controlled and recorded. These data are useful to reconstruct and to georeference the spectral image from the raw interferometric images. The visible and shortwave infrared component, named Hyspex ODIN-1024, consists of two spectrographs for VNIR and SWIR based on transmissive gratings. These share a common fore-optics and a common slit, to ensure perfect registration between the VNIR and the SWIR images. The spectral resolution varies from 5nm in the visible to 6nm in the shortwave infrared. In addition, the STAD, the post processing and archiving system, is developed to provide spectral reflectance and temperature products (SRT products) from calibrated georeferenced and inter-band registered spectral images at the sensor level acquired and pre-processed by SIELETERS and Hyspex ODIN-1024 systems.

• Torkildsen, Hans Erling; Hovland, Harald; Opsahl, Thomas Olsvik; Haavardsholm, Trym Vegard; Nicolas, Stephane & Skauli, Torbjørn (2014). Characterization of a compact 6-band multifunctional camera based on patterned spectral filters in the focal plane. Proceedings of SPIE, the International Society for Optical Engineering. ISSN 0277-786X. doi: 10.1117/12.2054477. Fulltekst i vitenarkiv Vis sammendrag

  In some applications of multi- or hyperspectral imaging, it is important to have a compact sensor. The most compact spectral imaging sensors are based on spectral filtering in the focal plane. For hyperspectral imaging, it has been proposed to use a "linearly variable" bandpass filter in the focal plane, combined with scanning of the field of view. As the image of a given object in the scene moves across the field of view, it is observed through parts of the filter with varying center wavelength, and a complete spectrum can be assembled. However if the radiance received from the object varies with viewing angle, or with time, then the reconstructed spectrum will be distorted. We describe a camera design where this hyperspectral functionality is traded for multispectral imaging with better spectral integrity. Spectral distortion is minimized by using a patterned filter with 6 bands arranged close together, so that a scene object is seen by each spectral band in rapid succession and with minimal change in viewing angle. The set of 6 bands is repeated 4 times so that the spectral data can be checked for internal consistency. Still the total extent of the filter in the scan direction is small. Therefore the remainder of the image sensor can be used for conventional imaging with potential for using motion tracking and 3D reconstruction to support the spectral imaging function. We show detailed characterization of the point spread function of the camera, demonstrating the importance of such characterization as a basis for image reconstruction. A simplified image reconstruction based on feature-based image coregistration is shown to yield reasonable results. Elimination of spectral artifacts due to scene motion is demonstrated.

• Yu, Xiaofang; Skauli, Torbjørn; Skauli, Bjørn; Sandhu, Sunil; Catrysse, Peter B. & Fan, Shanhui (2013). Wireless power transfer in the presence of metallic plates: Experimental results. AIP Advances. doi: 10.1063/1.4809665. Fulltekst i vitenarkiv Vis sammendrag

  We demonstrate efficient wireless power transfer between two high Q resonators, especially in a complex electromagnetic environment. In the close proximity of metallic plates, the transfer efficiency stays roughly the same as the free space efficiency with proper designs. The experimental data fits well with a coupled theory model. Resonance frequency matching, alignment of the magnetic field, and impedance matching are shown to be the most important factors for efficient wireless power transfer.

• Skauli, Torbjørn (2013). Information capacity as a figure of merit for spectral imagers: the trade-off between resolution and coregistration. Applied Optics. ISSN 0003-6935. doi: 10.1364/AO.52.000C58. Fulltekst i vitenarkiv Vis sammendrag

  The performance of spectral imagers is customarily described by several characteristics including resolution, noise, and coregistration. These must be traded off against each other in a practical imager design. This paper proposes a way to use the information capacity, in an information-theoretic sense, as a figure of merit for spectral imagers. In particular, it is shown how a metric [Opt. Express 20, 918 (2012)] can be used to incorporate coregistration performance in a definition of total noise, which in turn can be used in the definition of information capacity. As an example, it is shown how the information capacity can be used to optimize the pixel size in a simple case that can be treated analytically. Generally, the information capacity is attractive as a fundamental, application-independent figure of merit for spectral imager optimization and benchmarking.© 2013 Optical Society of America

• Catrysse, Peter B. & Skauli, Torbjørn (2013). Pixel scaling in infrared focal plane arrays. Applied Optics. ISSN 0003-6935. doi: 10.1364/AO.52.000C72. Fulltekst i vitenarkiv Vis sammendrag

  We discuss effects that arise in pixels of IR focal plane arrays (FPAs) when pixel size scales down to approach the wavelength of the incident radiation. To study these effects, we perform first-principles electromagnetic simulations of pixel structures based on a mercury–cadmium–telluride photoconductor for use in FPAs. Specifically, we calculate the pixel quantum efficiency and crosstalk as pixel size scales from 16 μm, which is in the range of current detectors, down to 0.75 μm, corresponding to subwavelength detectors. Our numerical results indicate the possibility of wavelength-size (∼4  μm ) and even subwavelength-size (∼1  μm ) pixels for IR FPAs. In addition, we explore opportunities that emerge for controlling light with subwavelength structures inside FPA pixels. As an illustration, we find that the low-pass filtering effect of a metal film aperture can exemplify the impact and the possible role that wavelength-scale optics plays in very small pixels.© 2013 Optical Society of America

• Yu, Zongfu; Sergeant, Nicholas P.; Skauli, Torbjørn; Zhang, Gang; Wang, Hailiang & Fan, Shanhui (2013). Enhancing far-field thermal emission with thermal extraction. Nature Communications. doi: 10.1038/ncomms2765. Fulltekst i vitenarkiv Vis sammendrag

  The control of thermal radiation is of great current importance for applications such as energy conversions and radiative cooling. Here we show theoretically that the thermal emission of a finite-size blackbody emitter can be enhanced in a thermal extraction scheme, where one places the emitter in optical contact with an extraction device consisting of a transparent object, as long as both the emitter and the extraction device have an internal density of state higher than vacuum, and the extraction device has an area larger than the emitter and moreover has a geometry that enables light extraction. As an experimental demonstration of the thermal extraction scheme, we observe a four-fold enhancement of the far-field thermal emission of a carbon-black emitter having an emissivity of 0.85.

• Skauli, Torbjørn (2012). An upper-bound metric for characterizing spectral and spatial coregistration errors in spectral imaging. Optics Express. doi: 10.1364/OE.20.000918. Fulltekst i vitenarkiv Vis sammendrag

  Coregistration errors in multi- and hyperspectral imaging sensors arise when the spatial sensitivity pattern differs between bands or when the spectral response varies across the field of view, potentially leading to large errors in the recorded image data. In imaging spectrometers, spectral and spatial offset errors are customarily specified as “smile” and “keystone” distortions. However these characteristics do not account for errors resulting from variations in point spread function shape or spectral bandwidth. This paper proposes improved metrics for coregistration error both in the spatial and spectral dimensions. The metrics are essentially the integrated difference between point spread functions. It is shown that these metrics correspond to an upper bound on the error in image data. The metrics enable estimation of actual data errors for a given image, and can be used as part of the merit function in optical design optimization, as well as for benchmarking of spectral image sensors.

• Hernandez-Palacios, Julio; Randeberg, Lise Lyngsnes; Haug, Ingvild; Baarstad, I.; Løke, T. & Skauli, Torbjørn (2011). Low-light hyperspectral imager for characterization of biological samples based on an sCMOS image sensor. I Raghavachari, Ramesh & Liang, Rongguang (Red.), Design and Quality for Biomedical Technologies IV. SPIE - The International Society for Optics and Photonics. ISSN 9780819484284. s. 78910V-1–78910V-10. doi: 10.1117/12.875770. Fulltekst i vitenarkiv
• Skauli, Torbjørn (2011). Quantifying coregistration errors in spectral imaging. Proceedings of SPIE, the International Society for Optical Engineering. ISSN 0277-786X. 8158. doi: 10.1117/12.894699. Fulltekst i vitenarkiv
• Skauli, Torbjørn (2011). Sensor noise informed representation of hyperspectral data, with benefits for image storage and processing. Optics Express. doi: 10.1364/OE.19.013031. Fulltekst i vitenarkiv Vis sammendrag

  Many types of hyperspectral image processing can benefit from knowledge of noise levels in the data, which can be derived from sensor physics. Surprisingly, such information is rarely provided or exploited. Usually, the image data are represented as radiance values, but this representation can lead to suboptimal results, for example in spectral difference metrics. Also, radiance data do not provide an appropriate baseline for calculation of image compression ratios. This paper defines two alternative representations of hyperspectral image data, aiming to make sensor noise accessible to image processing. A "corrected raw data" representation is proportional to the photoelectron count and can be processed like radiance data, while also offering simpler estimation of noise and somewhat more compact storage. A variance-stabilized representation is obtained by square-root transformation of the photodetector signal to make the noise signal-independent and constant across all bands while also reducing data volume by almost a factor 2. Then the data size is comparable to the fundamental information capacity of the sensor, giving a more appropriate measure of uncompressed data size. It is noted that the variance-stabilized representation has parallels in other fields of imaging. The alternative data representations provide an opportunity to reformulate hyperspectral processing algorithms to take actual sensor noise into account. (C) 2011 Optical Society of America

• Hernandez-Palacios, Julio; Randeberg, Lise Lyngsnes; Baarstad, Ivar; Løke, Trond & Skauli, Torbjørn (2010). Hyperspectral low-light camera for imaging of biological samples. I Luo,, Bin (Red.), Hyperspectral Image and Signal Processing: Evolution in Remote Sensing (WHISPERS), 2010 2nd Workshop on. IEEE Press. ISSN 9781424489060. s. 1–4. doi: 10.1109/WHISPERS.2010.5594943. Fulltekst i vitenarkiv
• Skauli, Torbjørn; Haavardsholm, Trym Vegard; Kåsen, Ingebjørg; Arisholm, Gunnar; Kavara, Amela & Opsahl, Thomas Olsvik [Vis alle 7 forfattere av denne artikkelen] (2010). An airborne real-time hyperspectral target detection system. Proceedings of SPIE, the International Society for Optical Engineering. ISSN 0277-786X. 7695. doi: 10.1117/12.850443. Fulltekst i vitenarkiv Vis sammendrag

  An airborne system for hyperspectral target detection is described. The main sensor is a HySpex pushbroom hyperspectral imager for the visible and near-infrared spectral range with 1600 pixels across track, supplemented by a panchromatic line imager. An optional third sensor can be added, either a SWIR hyperspectral camera or a thermal camera. In real time, the system performs radiometric calibration and georeferencing of the images, followed by image processing for target detection and visualization. The current version of the system implements only spectral anomaly detection, based on normal mixture models. Image processing runs on a PC with a multicore Intel processor and an Nvidia graphics processing unit (GPU). The processing runs in a software framework optimized for large sustained data rates. The platform is a Cessna 172 aircraft based close to FFI, modified with a camera port in the floor.

• Skauli, Torbjørn (2009). Sensor-informed representation of hyperspectral images. Proceedings of SPIE, the International Society for Optical Engineering. ISSN 0277-786X. 7334. doi: 10.1117/12.819491. Fulltekst i vitenarkiv Vis sammendrag

  Hyperspectral images are customarily stored and transferred as radiance values. Image analysis may benefit from additional sensor-related information such as signal-dependent noise levels. This paper discusses representations of hyperspectral image data in forms which are intermediate between raw data and radiance data. The intermediate-form data can be processed directly, or they can be readily converted into radiance values and estimates of signal-dependent noise. The metadata needed for this data transformation constitutes an informative first-order description of the sensor, as an added benefit for the data user. One of the proposed data formats has already been adopted in commercial hyperspectral sensors. The proposed representations can be stored in a more compact data format than radiance values without loss of information, under reasonable assumptions about the sensor properties. In particular, it will be shown that a square-root transformation of the data leads to a representation which approaches the information-theoretic lower limit for storing light samples. The use of noise estimates derived from sensor physics is likely to be useful in hyperspectral image processing and image compression.

• Tarabalka, Yulija; Haavardsholm, Trym Vegard; Kåsen, Ingebjørg & Skauli, Torbjørn (2009). Real-time anomaly detection in hyperspectral images using multivariate normal mixture models and GPU processing. Journal of Real-Time Image Processing. ISSN 1861-8200. doi: 10.1007/s11554-008-0105-x. Fulltekst i vitenarkiv Vis sammendrag

  Hyperspectral imaging, which records a detailed spectrum of light arriving in each pixel, has many potential uses in remote sensing as well as other application areas. Practical applications will typically require real-time processing of large data volumes recorded by a hyperspectral imager. This paper investigates the use of graphics processing units (GPU) for such real-time processing. In particular, the paper studies a hyperspectral anomaly detection algorithm based on normal mixture modelling of the background spectral distribution, a computationally demanding task relevant to military target detection and numerous other applications. The algorithm parts are analysed with respect to complexity and potential for parallellization. The computationally dominating parts are implemented on an Nvidia GeForce 8800 GPU using the Compute Unified Device Architecture programming interface. GPU computing performance is compared to a multicore central processing unit implementation. Overall, the GPU implementation runs significantly faster, particularly for highly data-parallelizable and arithmetically intensive algorithm parts. For the parts related to covariance computation, the speed gain is less pronounced, probably due to a smaller ratio of arithmetic to memory access. Detection results on an actual data set demonstrate that the total speedup provided by the GPU is sufficient to enable real-time anomaly detection with normal mixture models even for an airborne hyperspectral imager with high spatial and spectral resolution.

• Haakenaasen, Randi; Selvig, Espen; Hadzialic, S; Skauli, Torbjørn; Hansen, Vidar & Tibballs, J.E. [Vis alle 12 forfattere av denne artikkelen] (2008). Nanowires in the CdHgTe material system. Journal of Electronic Materials. ISSN 0361-5235. 37(9), s. 1311–1317. Fulltekst i vitenarkiv Vis sammendrag

  HgTe nanowires have been grown by molecular beam epitaxy (MBE). They are nucleated at Au particles on Si or GaAs substrates and subsequently self-organize and grow laterally on the surface into 20-50 nm wide, 0.5-1 mu m long twisted, but single-crystal, wires. Further growth gives longer, wider, and straighter polycrystalline wires. When unimpeded by Au particles on the surface, the wires become straight and consist of segments of cubic < 111 > HgTe and hexagonal < 001 > Te parallel to the wire. Te nanowires and Au nanowires have also occasionally been formed. All attempts to grow CdHgTe on Si substrates with or without Au particles have resulted in polycrystalline layers. The phase diagrams and diffusion coefficients imply that CdHgTe or HgTe nanowires will not grow by the vapor-liquid-solid technique at the low MBE growth temperatures. SiO2 functions as a mask for selective growth of HgTe, but not for CdHgTe.

• Selvig, Espen; Tonheim, Celin Russøy; Lorentzen, Torgeir; Kongshaug, Kjell Ove; Skauli, Torbjørn & Haakenaasen, Randi (2008). Defects in HgTe and CdHgTe grown by molecular beam epitaxy. Journal of Electronic Materials. ISSN 0361-5235. 37(9), s. 1444–1452. doi: 10.1007/s11664-008-0447-y. Fulltekst i vitenarkiv Vis sammendrag

  The defect morphology in HgTe and CdHgTe was studied in (211)B-oriented layers grown in a 20 degrees C temperature range around the optimal growth temperature. The density of defects varies strongly with the growth temperature. In HgTe, the shape of the microvoid defects is very sensitive to the growth temperature and can be used to determine the deviation from the optimal growth temperature. Using thermodynamical modeling, the optimal growth temperature for CdHgTe can then be calculated. We describe a mechanism for the formation of microvoids and needles which involves preferential surface diffusion of Te combined with an impurity or defect on the substrate. Microvoids on (111)B-oriented partially twinned HgTe layers were also studied. The microvoids in the twinned parts of the layer were found to be rotated 180 deg relative to the untwinned parts of the layer.

• Selvig, Espen; Tonheim, Celin Russøy; Kongshaug, Kjell Ove; Skauli, Torbjørn; Hemmen, H & Lorentzen, Torgeir [Vis alle 7 forfattere av denne artikkelen] (2008). Defects in CdHgTe grown by molecular beam epitaxy on, (211)B-oriented CdZnTe substrates. Journal of Vacuum Science & Technology B. ISSN 1071-1023. 26(2), s. 525–533. doi: 10.1116/1.2868782. Fulltekst i vitenarkiv
• Laux, E; Genet, C; Skauli, Torbjørn & Ebbesen, T.W. (2008). Plasmonic photon sorters for spectral and polarimetric imaging. Nature Photonics. ISSN 1749-4885. 2(3), s. 161–164. doi: 10.1038/nphoton.2008.1. Fulltekst i vitenarkiv
• Kåsen, Ingebjørg; Rødningsby, Anders; Haavardsholm, Trym Vegard & Skauli, Torbjørn (2008). Band selection for hyperspectral target-detection based on a multinormal mixture anomaly detection algorithm. Proceedings of SPIE, the International Society for Optical Engineering. ISSN 0277-786X. 6966. doi: 10.1117/12.777758. Fulltekst i vitenarkiv
• Selvig, Espen; Tonheim, Celin Russøy; Kongshaug, Kjell Ove; Skauli, Torbjørn; Lorentzen, Torgeir & Haakenaasen, Randi (2007). Defects in HgTe grown by molecular beam epitaxy on (211)B-oriented CdZnTe substrates. Journal of Vacuum Science & Technology B. ISSN 1071-1023. 25(6), s. 1776–1784. doi: 10.1116/1.2787876. Fulltekst i vitenarkiv
• Selvig, Espen; Hadzialic, S; Skauli, Torbjørn; Steen, Harald; Hansen, Vidar & Trosdahl-Iversen, L [Vis alle 9 forfattere av denne artikkelen] (2006). Growth of HgTe nanowires. Physica scripta. Topical Issues. ISSN 0281-1847. 126, s. 115–120. Fulltekst i vitenarkiv
• Haakenaasen, Randi; Steen, Helge; Selvig, Espen; Rheenen, Arthur Dirk Van; Trosdahl-Iversen, Laila & Hall, D. [Vis alle 10 forfattere av denne artikkelen] (2006). Imaging photovoltaic infrared CdHgTe detectors. Physica Scripta. ISSN 0031-8949. T126, s. 31–36. doi: 10.1088/0031-8949/2006/T126/007. Fulltekst i vitenarkiv

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• Holdcroft, Sam; Bocci, Alessio; Scholtz, Laura-Kristin; Retselis, Anastasios-Faidon; Knutsen, Elise Wright & Jebali, Ramsey Al [Vis alle 20 forfattere av denne artikkelen] (2025). CENSSAT-1 mission concept: a CubeSat for space weather monitoring. doi: 10.5281/ZENODO.17036544. Fulltekst i vitenarkiv Vis sammendrag

  This paper presents an introduction to the CENSSAT-1 mission, an 8U CubeSat, which aims to study space situational awareness. It will investigate the effects of space weather on Earth from a 500 km orbit, using a camera, multi-purpose particle detector, and a Langmuir probe. It will additionally monitor space debris using a radar instrument, and conduct experiments on optimal control and drag based manoeuvring. CENSSAT-1 is aiming for launch in 2027.

• Skauli, Torbjørn; Gilchrist, John & Durell, Christopher (2022). Specification of hyperspectral camera performance: status of the IEEE P4001 standard development. Fulltekst i vitenarkiv
• Gilchrist, John; Skauli, Torbjørn & Durell, Christopher (2022). Developing the IEEE P4001 standard for characterisation and calibration of hyperspectral imaging devices. Fulltekst i vitenarkiv
• Haavardsholm, Trym Vegard; Opsahl, Thomas Olsvik; Skauli, Torbjørn & Stahl, Annette (2022). Compact multimodal multispectral sensor system for tactical reconnaissance. Fulltekst i vitenarkiv
• Ientilucci, Emmett; conran, david; Soffer, Raymond; Perry, David; Skauli, Torbjørn & Gilchrist, John [Vis alle 7 forfattere av denne artikkelen] (2022). Development of test methods for hyperspectral cameras characterization in the P4001 standards development. Fulltekst i vitenarkiv
• Gilchrist, John; Skauli, Torbjørn & Durell, Christopher (2022). Developing the IEEE P4001 Standard for Characterization and Calibration of Hyperspectral Imaging Devices. Fulltekst i vitenarkiv
• Skauli, Torbjørn (2022). Kameraer som ser det usynlige. Fulltekst i vitenarkiv
• Gilchrist, John; Arlen, Robert; Skauli, Torbjørn; Durell, Christopher & Weatherbee, Oliver (2022). Choice of terminology in the P4001 standard for hyperspectral imaging. Fulltekst i vitenarkiv
• Makowski, Jan; Eckstein, Barbara; Durell, Christopher; Gilchrist, John & Skauli, Torbjørn (2022). Metadata definitions for a set of notional use cases in the IEEE P4001 standard for hyperspectral imaging. Fulltekst i vitenarkiv
• Skauli, Torbjørn (2021). Characterizing the dynamic range of a hyperspectral camera. Fulltekst i vitenarkiv
• Gilchrist, John; Durell, Christopher & Skauli, Torbjørn (2021). IEEE P4001: progress update towards an international standard for push-broom hyper-spectral imagers. Fulltekst i vitenarkiv
• Lofstad-Lie, Victoria Emilie; Marstein, Erik Stensrud; Simonsen, Aleksander & Skauli, Torbjørn (2021). Cost-Effective Flight Strategy for Aerial Thermography Inspection of Photovoltaic Power Plants. Fulltekst i vitenarkiv
• Skauli, Torbjørn; Gilchrist, John & Durell, Christopher (2021). Status of the IEEE P4001 Working Group for Standardization in Hyperspectral Imaging. Fulltekst i vitenarkiv
• Skauli, Torbjørn (2021). Vi snakker om Plancks strålingslov: klima, energi, kvanter og kameraer som kan se i mørke. Fulltekst i vitenarkiv
• Skauli, Torbjørn (2020). How Good Is Your Spectral Sensor? Figures of Merit for Coregistration and Radiometric Quality for Spectral Imagers and Spectrometers. Fulltekst i vitenarkiv
• Skauli, Torbjørn (2019). Standardization in hyperspectral imaging: The IEEE P4001 working group, and some examples of ongoing work. Fulltekst i vitenarkiv
• Skauli, Torbjørn (2019). The Morse Machine. RadCom. ISSN 1367-1499. 95(6), s. 42–42. Fulltekst i vitenarkiv
• Skauli, Torbjørn (2019). Simplified measurement of point spread functions for assessment of spatial coregistration. Fulltekst i vitenarkiv
• Skauli, Torbjørn (2018). Hyperspectral imaging. Fulltekst i vitenarkiv
• Torkildsen, Hans Erling; Haavardsholm, Trym Vegard; Opsahl, Thomas Olsvik; Datta, Urmila; Skaugen, Atle & Skauli, Torbjørn (2018). Compact multispectral multi-camera imaging system for small UAVs. Fulltekst i vitenarkiv
• Skauli, Torbjørn; Skaar, Sindre Løining & Torkildsen, Hans Erling (2018). Effect of spatial coregistration error on the dimensionality of hyperspectral image data. Fulltekst i vitenarkiv
• Hovland, Harald & Skauli, Torbjørn (2018). Thermal infrared reference sources fabricated from low-cost components and materials. Fulltekst i vitenarkiv
• Skauli, Torbjørn (2017). Feasibility of a standard for full specification of spectral imager performance. Fulltekst i vitenarkiv Vis sammendrag

  The current state of the art of specifying spectral imagers falls short of what is needed. Commercial datasheets do not adequately reflect the performance of hyperspectral imagers offered as standard products. In particular, imperfections such as coregistration error, noise performance and stray light are rarely well specified. A standardized way to specify spectral imagers would benefit both developers and users of such instruments. The paper reviews the many different characteristics that are needed to describe various aspects of imager performance, and discusses possible ways to form figures of merit relevant to application performance. In particular, the product of quantum efficiency, optics transmission and nominal throughput (étendue) is shown to be a good figure of merit for radiometric performance. A list of about 30 characteristics is suggested as a standard for a complete specification of spectral imagers. For some characteristics, notably coregistration, it is necessary to establish a standardized measurement methodology.

• Skauli, Torbjørn (2017). Toward Standardization of Performance Characteristics for Spectral Imagers: How to Specify a Hyperspectral Camera? Fulltekst i vitenarkiv
• Rousset-Rouviere, Laurent; Coudrain, Christophe; Fabre, Sophie; Poutier, Laurent; Løke, Trond & Fridman, Andrei [Vis alle 10 forfattere av denne artikkelen] (2014). SYSIPHE system: a state of the art airborne hyperspectral imaging system: initial results from the first airborne campaign. Fulltekst i vitenarkiv
• Imai, Francisco Hideki; Berg, Dale C. Linne Von; Skauli, Torbjørn; Tominaga, Shoji & Zalevsky, Zeev (2014). Imaging systems and applications: Introduction to the feature. Applied Optics. ISSN 0003-6935. s. ISA1–ISA2. doi: 10.1364/AO.53.00ISA1. Fulltekst i vitenarkiv
• Skauli, Torbjørn & Farrell, Joyce (2013). A collection of hyperspectral images for imaging systems research. Fulltekst i vitenarkiv
• Skauli, Torbjørn; Torkildsen, Hans Erling; Kåsen, Ingebjørg; Nicolas, Stephane; Haavardsholm, Trym Vegard & Opsahl, Thomas Olsvik (2013). Multispectral and conventional imaging combined in a compact camera by using patterned filters in the focal plane. Fulltekst i vitenarkiv
• Skauli, Torbjørn (2013). How good are your spectral images? Noise, coregistration and information rate in spectral imaging. Fulltekst i vitenarkiv
• Skauli, Torbjørn (2012). Optimizing the information rate from spectral imagers in the design tradeoff between resolution and coregistration. Fulltekst i vitenarkiv
• Haavardsholm, Trym Vegard; Kavara, Amela; Kåsen, Ingebjørg & Skauli, Torbjørn (2012). Improving anomaly detection with Multinormal Mixture Models in shadow. Fulltekst i vitenarkiv
• Rousset-Rouviere, Laurent; Coudrain, Christophe; Fabre, Sophie; Baarstad, Ivar; Fridman, Andrei & Løke, Trond [Vis alle 8 forfattere av denne artikkelen] (2011). SYSIPHE, an airborne hyperspectral imaging system for the VNIR-SWIR-MWIR-LWIR region. Fulltekst i vitenarkiv
• Skauli, Torbjørn; Haavardsholm, Trym Vegard; Kåsen, Ingebjørg; Opsahl, Thomas Olsvik; Kavara, Amela & Skaugen, Atle (2011). Hyperspectral imaging technology and systems, exemplified by airborne real-time target detection. Fulltekst i vitenarkiv
• Denstedt, Martin Anders F.; Haavardsholm, Trym Vegard; Skauli, Torbjørn & Randeberg, Lise Lyngsnes (2011). A hyperspectral imaging system for real-time analysis of skin – capabilities and prospects. Fulltekst i vitenarkiv
• Haavardsholm, Trym Vegard; Arisholm, Gunnar; Kavara, Amela & Skauli, Torbjørn (2010). Architecture of the real-time target detection processing in an airborne hyperspectral demonstrator system. Fulltekst i vitenarkiv Vis sammendrag

  An airborne demonstrator for real-time hyperspectral target detection has been developed at FFI. The real-time image processing is challenging, not only due to the computational complexity of the algorithms, but also due to the sustained high data rate. A software framework has been designed in C++ to handle large data flows in a nonlinear pipeline architecture. The cross-platform framework enables full exploitation of multicore processors and graphics processing units (GPU), and even distribution among multiple computers. Object oriented design enables flexible reconfiguration of the pipeline. Tests demonstrate sustained real-time performance of complex anomaly detection processing.

• Hernandez-Palacios, Julio; Randeberg, Lise Lyngsnes; Baarstad, Ivar; Løke, Trond & Skauli, Torbjørn (2010). Hyperspectral low-light camera for imaging of biological samples. Fulltekst i vitenarkiv
• Randeberg, Lise Lyngsnes; Haavardsholm, Trym Vegard; Arisholm, Gunnar; Kavara, Amela; Løke, Trond & Skauli, Torbjørn (2010). Rapid hyperspectral characterization of skin. Fulltekst i vitenarkiv
• Hernandez-Palacios, Julio; Randeberg, Lise Lyngsnes; Baarstad, Ivar; Løke, Trond & Skauli, Torbjørn (2010). Hyperspectral low-light camera for macroscopic imaging of biological samples. Fulltekst i vitenarkiv
• Hernandez-Palacios, Julio; Randeberg, Lise Lyngsnes; Baarstad, Ivar; Løke, Trond & Skauli, Torbjørn (2010). Hyperspectral low-light camera for macroscopic imaging of biological samples. Fulltekst i vitenarkiv
• Hernandez-Palacios, Julio; Randeberg, Lise Lyngsnes; Baarstad, Ivar; Løke, Trond & Skauli, Torbjørn (2010). Hyperspectral low-light camera for imaging of biological samples. Fulltekst i vitenarkiv
• Hernandez-Palacios, Julio; Randeberg, Lise Lyngsnes; Baarstad, Ivar; Løke, Trond & Skauli, Torbjørn (2010). Hyperspectral low-light camera for imaging of biological samples. Fulltekst i vitenarkiv
• Hovland, Harald; Hamran, Svein-Erik & Skauli, Torbjørn (2015). Tomographic scanning imager. Akademika forlag. Fulltekst i vitenarkiv

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