Application of optical flow method for imaging diagnostic in JET

Abstract

An optical flow method is applied to the study of several fusion plasma relevant issues, including plasma wall interactions. A multi-resolution coarse-to-fine procedure is used in order to cope with large displacements of objects between consecutive frames, characteristic of plasma images captured by JET fast visible camera. Occlusion modeling is also implemented. The method is able to provide good results for JET fast-visible camera images which can be affected by saturation, discontinuous movement, reshaping of image objects, low gray-level in-depth resolution. Significant experimental cases concerning pellet injection, plasma filaments and MARFEs are analysed. The method is able to provide the real velocity for objects moving close to structures.

A self-adaptive optical flow method for the moving object detection in the video sequences

“…So the interval is controlled within 5 frames in the following experiments. 5 shows the comparison of the proposed method (combining HS optical flow with block method and local mean algorithm) and LK optical flow algorithm [19,23]. The result of LK optical flow algorithm is shown in Fig.…”

“…Here, HS optical flow algorithm is presented to compute the original optical flow field. HS optical flow algorithm is proposed based on the following two basic assumptions: the first one is any observed object point intensity is constant over time (gray scale invariance constraint), the other is that the close points of image plane moving in a similar way (speed smoothness constraint) [18][19][20]. In this way, we can get the basic optical flow equation:…”

Experimental observations of naturally occurring dust using a high-speed vacuum ultraviolet imaging system in EAST

“…In order to analyze the basic characteristics of the ablative cloud ablation process, an optical flow method [16] is used to compute an approximation to the motion field of the dust ablation cloud from time-varying image intensity. Optical flow is defined as the apparent motion of individual pixels on the image plane.…”

“…Then, the dynamics of the ablation cloud can be investigated quantitatively. Details of the optical flow and grayscale centroid methods can be found in [16,17], respectively.…”

Determination of the pellet parameters by image processing methods

“…A recently developed optical flow (OF) method [6] was adapted in order to evaluate the ice extrusion velocity based on the image sequences provided by a CCD camera viewing the ice at the exit of the nozzles of the extrusion cryostat [7]. The method combines the advantages of local methods (robust under noise) and global techniques (which yield dense flow fields).…”