Estimating any correspondence between two widely-separate views for arbitrarily-selected point, as a contribution to improving image recognition

Eden izmed možnih načinov spremljanja aktivnosti na gradbišču je zajemanje slik z več kamerami, kateremu sledi razpoznavanje posameznih gradbenih elementov in ugotavljanje izgotovljenosti objekta na osnovi 4D modela. Takšen pristop zahteva vzpostavitev korespondence med slikami, zajetimi iz različnih pogledov (kamer). Osnovni problem je torej vzpostavitev korespondence za poljubno izbrano točko, ki se lahko nahaja kjerkoli na sliki (tudi na področjih slike z zelo podobno barvo ali teksturo). V doktorski disertaciji smo razvili novo robustno metodo ASIFT-SH za vzpostavitev korespondence za poljubno izbrano točko pri velikih odmikih dveh kamer, ki je mešanica metod ASIFT, segmentacije in lokalne homografije. Ta metoda sestoji iz štirih korakov: i.) določitve začetnih korespondenčnih točk na slikah obeh pogledov z metodo ASIFT, ii.) združevanja korespondenčnih točk iz prvega koraka v ustrezne podmnožice na osnovi segmentiranih regij, iii.) izračuna lokalnih homografij za posamezno podmnožico korespondenčnih točk, ki pripadajo posamezni segmentirani regiji in iv.) izračuna korespondenčne točke z uporabo ustrezne lokalne homografije. Metoda ASIFT-SH v primerjavi z metodo, ki določi korespondenčne točke na osnovi iskanja v okolici epipremice (metoda EPI), zagotavlja bistveno boljše rezultate, še posebej na področjih slike s podobno intenziteto slikovnih elementov. Povprečna napaka korespondenčnih točk, izračunanih z našo metodo, je nekaj slikovnih elementov, medtem ko je odstopanje korespondenčnih točk, vzpostavljenih z metodo EPI, nekaj sto slikovnih elementov. Kritičen korak metode ASIFT-SH predstavlja segmentacija. Metoda namreč predpostavlja, da segmentirane regije ustrezajo kriteriju koplanarnosti (tj. vse točke v segmentirani regiji ležijo v isti ravnini). V splošnem tega ni mogoče zagotoviti. V naš algoritem smo zato vpeljali še korak adaptivnega prilagajanja, s katerim lahko preoblikujemo segmentirane regije tako, da bolje izpolnjujejo zahtevani kriterij. Vpeljani korak temelji na 3D rekonstrukciji začetnih korespondenčnih točk in iskanju čim manjšega števila ravnin v prostoru, katerim te točke pripadajo. Točke, ki pripadajo posamezni ravnini, predstavljajo novo nastale podmnožice začetnih korespondenčnih točk. Rezultati meritev so pokazali, da vpeljava dodatnega koraka, ki omogoča adaptivno prilagajanje segmentiranih regij na osnovi 3D rekonstrukcije, tj. adaptivna različica metode ASIFT-SH, zagotavlja povečanje natančnosti izračunanih korespondenčnih točk. Uspešnost adaptivnega prilagajanja segmentiranih regij je neposredno odvisna od 3D rekonstrukcije, na katero pa močno vplivajo notranji in zunanji parametri kamere. Ker so kamere na gradbišču izpostavljene različnim okoljskim dejavnikom, ki vplivajo tudi na parametre kamere, smo v naši raziskavi preučili tudi vpliv temperaturnih sprememb na geometrijske lastnosti kamere. Vpliv temperature smo ugotavljali tako za eno kamero, kot tudi za sistem kalibriranih kamer, pri čemer vpliva na elektroniko kamere nismo proučevali. Najprej smo dopolnili analitični model kamere s členom, ki modelira vpliv temperaturnih sprememb na delovanje posamezne kamere. Takšen modificirani analitični model kamere omogoča kvantitativno oceno vpliva temperaturnih sprememb na delovanje kamere. Sprememba temperature neposredno vpliva tudi na natančnost sistema kalibriranih kamer. Oceno takšnega odstopanja smo določili eksperimentalno, saj analitična določitev napake ni mogoča. Na koncu smo definirali skupno odstopanje (napako) kalibriranih kamer, kjer smo upoštevali tako odstopanje zaradi numerične napake kalibracijske metode in postopka 3D rekonstrukcije, kot tudi odstopanje, ki je posledica vpliva temperaturnih sprememb. Rezultati raziskave so pokazali, da se vpliv temperature zmanjšuje z večanjem razdalje med kamero in opazovanim objektom. V predvidenih delovnih pogojih na gradbišču, se vpliv temperaturnih sprememb na sliki odraža za manj kot en slikovni element.One possible method of monitoring activities on the building site is based on capturing images using multiple cameras, followed by the recognition of individual building components, and then identifying an object\u27s status based on a 4D model. Such an approach requires the establishment of some correspondence between those images captured from different viewpoints (cameras). The basic problem is, therefore, the establishment of any correspondence at an arbitrarily selected point, which could be located anywhere on the image (also on image areas with uniform colour or texture). This doctoral dissertation develops a new robust ASIFT-SH method for establishing any correspondence between arbitrarily-selected points within two widely-baselined cameras, which is a combination of the ASIFT method, segmentation, and local homography. This method consists of four steps: i) determining the initial corresponding points within the images of both views by using the ASIFT method, ii.) grouping of initial corresponding points from the first step into subsets, based on segmented regions iii.) calculation of local homographies for a particular subset of corresponding points, and iv.) determining any correspondence between arbitrary points from a particular camera\u27s viewpoint, by using a suitable local homography. The ASIFT-SH method, when compared to that of searching the area surrounding an epipolar line (EPI method), provides more accurate results, especially on surfaces with similar pixel intensities. The average error in our method comes within the order of a few pixels, whilst for the EPI method it is within the order of a few hundred pixels. The critical step of the ASIFT-SH method concerns segmentation. The segmentation presupposes that the segmented regions correspond to the coplanarity criteria (i.e., all points in the segmented region are located within the same plane). In general, this cannot be ensured. Therefore, we have introduced into our algorithm a step for adaptive adjustment, within which segmented regions are remodelled so that they better meet the required criterion. This introduced step is based on 3D reconstruction of the initial corresponding points, and a search for the minimal number of planes within the 3D space, to which these points belong. Those points that belong to a particular plane, represent a newly-created subset of the initial corresponding points. The results point out that the introduction of additional step enables an adaptive adjustment of segmented regions based on the 3D reconstruction, i.e. an adaptive version of the ASIFT-SH method, thus assuring more accurate calculation of the corresponding points. The success of adaptively adjusting segmented regions directly depends on the 3D reconstruction, which is, however, strongly affected by intrinsic and extrinsic camera parameters. Since cameras at a building site are exposed those different environmental factors which also affect the cameras\u27 parameters, therefore, in our study we investigated any influence of temperature variations on the geometric properties of the camera. Temperature influence on the geometrical properties of both a single camera and a calibrated camera system was estimated, whereas the influence on camera electronics was ignored. Firstly, the analytical camera model was supplemented with a term, which models the influence of temperature variations over a single camera\u27s operation. A modified analytical camera model enabled quantitative assessment regarding the influence of temperature variations on a camera\u27s operation. Temperature variations also directly influence the accuracies of calibrated cameras. The inability to analytically-determine the calibration method error magnitude, led us to experimentally-estimate any errors regarding calibrated cameras. Finally, the total errors regarding calibrated cameras were derived at by combining the numerical errors of the calibration method and 3D reconstruction with those errors originating from temperature variations. The results show that the influence of temperature vari

Analytical Camera Model Supplemented with Influence of Temperature Variations

Abstract—A camera in the building site is exposed to different weather conditions. Differences between images of the same scene captured with the same camera arise also due to temperature variations. The influence of temperature changes on camera parameters were modelled and integrated into existing analytical camera model. Modified camera model enables quantitatively assessing the influence of temperature variations. Keywords—camera calibration, analytical model, intrinsic parameters, extrinsic parameters, temperature variations. I

Influence of Temperature Variations on Calibrated Cameras

Abstract—The camera parameters are changed due to temperature variations, which directly influence calibrated cameras accuracy. Robustness of calibration methods were measured and their accuracy was tested. An error ratio due to camera parameters change with respect to total error originated during calibration process was determined. It pointed out that influence of temperature variations decrease by increasing distance of observed objects from cameras. Keywords—camera calibration, perspective projection matrix, epipolar geometry, temperature variation. I

Nemoteče spremljanje delovanja srca z optičnim senzorjem v postelji

Demographic trends suggest that by 2050 approximately 11 % of the world population will be 80 or older. If a fast increase of chronic diseases is also considered, it becomes clear the present healthcare capacities won\u27t be enough. The elderly and people with limited abilities must be assisted in their home environment and, thus, reduce needs for hospitalization and institutionalization. Today\u27s computer and communication technologies provide different smart devices, which is a core of emerging intensification of homecare services, in particular remote and unobtrusive monitoring of human functional- health parameters.Demografski trendi kažejo, da bo do leta 2050 približno 11 % svetovnega prebivalstva starejših od 80 let. Če dodamo še hitro naraščajoči obseg kroničnih bolezni, postane jasno, da sedanje zdravstvene zmogljivosti obremenitev ne bodo zdržale. Starejšim in ljudem z omejenimi sposobnostmi bo treba pomagati, da bodo čim dlje ostali samostojni v svojem domačem okolju, in tako omejiti hospitalizacije ter nujnost oskrbe v zdravstvenih zavodih. Današnje računalniške in komunikacijske tehnologije ponujajo pametne naprave, ki bodo kmalu omogočile bistveno intenziviranje zdravstvenih storitev na domu, predvsem kot nemoteče nadziranje parametrov funkcionalnega zdravja na daljavo

Unobtrusive monitoring of human vital functions based on speckle interferometry with plastic optical fiber

In this paper, a speckle interferometer with a plastic optical fiber system is reported for unobtrusive monitoring of heartbeat and respiration. The sensor consists of a laser diode butt-coupled to the plastic optical fiber, whose exit face projects speckle patterns onto a linear optical sensor array, which leads to a simple and cost-effective construction. Speckle images are acquired in a sequence and transformed into a 1D signal by using a phase-shifting method. Band-pass filtering and Morlet-wavelet-based multiresolutional approaches were used to analyze signals for the detection of cardiac and respiratory activities, respectively. Ten young, healthy persons participated in system testing, by lying supine on a mattress with embedded plastic optical fiber. Experimental results show the proposed system and detection algorithms are highly efficient. Sensitivities of 99.4 0.6% and 95.3 3%, precisions of 98.8 1.5% and 97.9 2.3%, and mean delays between interferometric detections and corresponding referential signals of 116.6 55.5ms and 1299.2 437.3 ms were computed for heartbeat and respiration, respectively