Search results for "Spektri"
showing 10 items of 61 documents
Spectrum and energy efficient solutions for OFDMA collaborative wireless networks
2013
Hyperspektrikuvantaminen fotometrisessä stereossa ja sen hyödyntäminen tietokonegrafiikassa
2017
Tässä tutkielmassa tutkitaan hyperspektrikuvien avulla toteutetun fotometrisen stereon vaikutuksia tietokonegrafiikassa. Tutkimuksessa hyperspektrikuvien ja fotometrisen stereon avulla luotiin malleja, joista edelleen renderöitiin kuvia. Hyperspektrikuvantamisen havaittiin parantavan renderöinnin kuvanlaatua hieman, mutta heikentävän sen suorituskykyä kymmenkertaisesti. Lisäksi tutkittiin mallien luomisen nopeuttamista rinnakkaislaskennan avulla. Tuloksena pintojen muotojen määrittäminen pintojen orientaatioiden avulla saatiin grafiikkasuorittimella yli 13-kertaisesti nopeammaksi. In this thesis the effects of photometric stereo implemented using hyperspectral images in computer graphics ar…
Miniature MOEMS hyperspectral imager with versatile analysis tools
2019
The Fabry-Perot interferometers (FPI) are essential components of many hyperspectral imagers (HSI). While the Piezo-FPI (PFPI) are still very relevant in low volume, high performance applications, the tunable MOEMS FPI (MFPI) technology enables volume-scalable manufacturing, thus having potential to be a major game changer with the advantages of low costs and miniaturization. However, before a FPI can be utilized, it must be integrated with matching optical assembly, driving electronics and imaging sensor. Most importantly, the whole HSI system must be calibrated to account for wide variety of unwanted physical and environmental effects, that significantly influence quality of hyperspectral…
A Do-It-Yourself Hyperspectral Imager Brought to Practice with Open-Source Python
2021
Commercial hyperspectral imagers (HSIs) are expensive and thus unobtainable for large audiences or research groups with low funding. In this study, we used an existing do-it-yourself push-broom HSI design for which we provide software to correct for spectral smile aberration without using an optical laboratory. The software also corrects an aberration which we call tilt. The tilt is specific for the particular imager design used, but correcting it may be beneficial for other similar devices. The tilt and spectral smile were reduced to zero in terms of used metrics. The software artifact is available as an open-source Github repository. We also present improved casing for the imager design, …
A method for anomaly detection in hyperspectral images, using deep convolutional autoencoders
2017
Menetelmä poikkeavuuksien havaitsemiseen hyperspektrikuvista käyttäen syviä konvolutiivisia autoenkoodereita. Poikkeavuuksien havaitseminen kuvista, erityisesti hyperspektraalisista kuvista, on hankalaa. Kun ongelmaan yhdistetään ennalta tuntematon data ja poikkeavuudet, muodostuu ongelma vielä laajemmaksi. Spektraalisten poikkeavuuksien havaitsemiseen on kehitetty useita eri menetelmiä, mutta spatiaalisten poikkeavuuksien havaitseminen on huomattavasti hankalempaa. Tässä työssä esitellään uudenkaltainen menetelmä sekä spatiaalisten että spektraalisten poikkeavuuksien samanaikaiseen havaitsemiseen. Menetelmä on suunniteltu erityisesti spektraaliselle datalle, mutta soveltuu myös perinteisil…
New applications of zoobenthos measurements for risk assessment of chemicals in aquatic ecosystems
2015
Artikkeliväitöskirja. Yhteenveto-osa ja viisi artikkelia. (Artikkelit eivät avoimesti saatavilla.) Article dissertation. An introduction and five articles (not available in this version). Benthic animals in aquatic ecosystems suffer from various anthropogenic pollutants. A challenge in risk assessment of chemicals in aquatic ecosystems (i.e. ecological risk assessment) has been to balance cost-efficiency and effectiveness in detecting early warning signals of chemicals. In this study, hyperspectral imaging and behavioural measurements were evaluated as novel applications for detecting chemical effects on benthic animals, and the reliability of the incidence of chironomid morphological defor…
Unmixing methods in novel applications of spectral imaging
2014
Hyperspektrisen kaukokartoitusdatan analysointialgoritmeja
2003
FPI Based Hyperspectral Imager for the Complex Surfaces : Calibration, Illumination and Applications
2022
Hyperspectral imaging (HSI) applications for biomedical imaging and dermatological applications have been recently under research interest. Medical HSI applications are non-invasive methods with high spatial and spectral resolution. HS imaging can be used to delineate malignant tumours, detect invasions, and classify lesion types. Typical challenges of these applications relate to complex skin surfaces, leaving some skin areas unreachable. In this study, we introduce a novel spectral imaging concept and conduct a clinical pre-test, the findings of which can be used to develop the concept towards a clinical application. The SICSURFIS spectral imager concept combines a piezo-actuated Fabry–Pé…