ABSTRACT
Optical coordinate transformation (OCT) has attracted widespread attention in the field of orbital angular momentum (OAM) (de)multiplexing or manipulation, but the performance of OCT would suffer from its distortion. In this paper, we quantitatively analyze the distortion of OCT from the perspective of ray optics and explain its rationality to work under non-normal incident light. For the special case of log-polar coordinate transformation (LPCT), we use a raytracing assisted optimization scheme to improve its distortion, which is related to a Zernike polynomial based phase compensation. After raytracing optimization, the root mean square error (RMSE) of the focused rays is reduced to 1/5 of the original value and the physical optic simulation also shows great improvement. In the experiment, we use three phase masks which are realized by metasurfaces, the measured results show well consistency with the simulation. Results in this paper have great potential to improve the performance of OCT related applications.
ABSTRACT
BACKGROUND: Idiopathic rapid eye movement sleep behavior disorder is an early sign of neurodegenerative disease. This study aimed to quantitatively evaluate iron content in idiopathic rapid eye movement sleep behavior disorder patients using quantitative susceptibility mapping and to examine the potential of this technique to identify the prodromal stage of α-synucleinopathies. METHODS: Twenty-five idiopathic rapid eye movement sleep behavior disorder patients, 32 Parkinson's disease patients, and 50 healthy controls underwent quantitative susceptibility mapping. The mean magnetic susceptibility values within the bilateral substantia nigra, globus pallidus, red nucleus, head of the caudate nucleus, and putamen were calculated and compared among groups. The relationships between the values and the clinical features of idiopathic rapid eye movement sleep behavior disorder and Parkinson's disease were measured using correlation analysis. RESULTS: Idiopathic rapid eye movement sleep behavior disorder patients had elevated iron in the bilateral substantia nigra compared with healthy controls. Parkinson's disease patients had increased iron in the bilateral substantia nigra, globus pallidus, and left red nucleus compared with healthy controls and had elevated iron levels in the bilateral substantia nigra compared with idiopathic rapid eye movement sleep behavior disorder patients. Mean magnetic susceptibility values were positively correlated with disease duration in the left substantia nigra in idiopathic rapid eye movement sleep behavior disorder patients. CONCLUSIONS: Quantitative susceptibility mapping can detect increased iron in the substantia nigra in idiopathic rapid eye movement sleep behavior disorder, which becomes more significant as the disorder progresses. This technique has the potential to be an early objective neuroimaging marker for detecting α-synucleinopathies. © 2019 International Parkinson and Movement Disorder Society.
Subject(s)
Neurodegenerative Diseases , REM Sleep Behavior Disorder , Globus Pallidus , Humans , Iron , Substantia NigraABSTRACT
We study both analytically and numerically nonparaxial propagation dynamics of the Chirped Airy vortex (CAiV) beams in uniaxial crystal orthogonal to the optical axis. The propagation trajectory, the intensity, the radiation forces, the Poynting vector and the angular momentum (AM) of the CAiV beams are illustrated by numerical examples. The influences of the ratio of the extraordinary refractive index to the ordinary refractive index, the linear chirp factor and the quadratic chirp factor on the nonparaxial evolution of the CAiV beams are examined in detail. Results show that the linear chirp factor provides an intensity concentration, which is totally different with the influence of the quadratic chirp. Besides, the uniaxial crystals with different refractive index ratios can be used to control the intensity of optical lobes. Moreover, the value and the direction of the radiation forces depend on the propagation distance and the chirp factor. The chirp factor acting on the Poynting vector and the AM mainly occurs in the direction of vectors. The nonparaxial propagation characteristics of the CAiV beams provide a convenient method to the intensity modulation and the optical manipulation of micro particles.
