This paper proposes a novel video stabilization method based on FREAK. That method combines the advantages of the fast speed of binary features and the high efficiency and robustness to parallax of 2D feature trajectories, which avoids inheriting the limitation to parallax from other 2D methods. In order to make the smoothed camera paths as flat as shot by a smoothly moving platform, we take full consideration of 2-degree gradients of the trajectories. This is done by adding a 2-degree regularization to the bundled paths optimization equations. Moreover, a spectral technique is employed to improve the accuracy of original feature matching results. Experiments demonstrate the competitive performance of our proposed method.
Ghost interference with entangled photon pairs are studied theoretically. The pump beam in parametric down-conversion is treated as the Gaussian profile, while for the function describing phase matching in the longitudinal direction, both a Gaussian and a sinc function are considered. The numerical results show that the transverse size of the pump beam and transverse coherence width of the parametric fluorescence strongly influence the interference pattern. With the increase of the pump transverse size and the decrease of transverse coherence width, the interference pattern becomes more and more prominent. When the transverse coherence width is small to 0.01 mm category, the Gaussian and sinc models give the same results.
The effect of pump focusing on the performance of ghost imaging is studied experimentally on an entangled source. Theoretical results show that the correlation properties of the entangled photon source are destroyed when the conversion crystal is pumped by a focused laser beam. The experiment is performed on a compact entangled source produced by type-II non-collinear degenerate SPDC, and the results demonstrate that the “walk off” effects almost have no effect on the image, while the pump focusing greatly degrades the visibility of the image. However, a sharp image could be reproduced in the configuration first proposed in Ref. [8] for the case with pump focusing.
The independent control of the upper and lower cutoff frequencies of the guided modes in coupled-cavity wavguides (CCWs) is investigated numerically. The CCWs are formed in a two-dimensional photonic crystal (2D PhC) consisting of a square array of dielectric rods in the air. The dielectric constant and radius of the rods in the perfect PhC is 11.56 and 0.18α, respectively, in which α is lattice constant. By using the plane wave expansion method (PWEM), the impact of two influencing factors on cutoff frequencies in CCWs is calculated systematically. Efficient methods have been demonstrated for tuning one cutoff frequency while keeping the other unchanged. The indepent control ranges of the upper and lower cutoff can be up to 67.85% and 68.57% of photonic band gap (PBG), respectively. The results can be applied to the design of PhC-based optical devices such as band filters and optical switches.
We present a novel numerical model for an ytterbium-doped fiber ring laser. A comprehensive numerical model based on an iterative solution of propagation rate equations is used to analyze the impact of various laser variables. The dependence of laser output power on pump power, ytterbium-doped fiber (YDF) length, and emission wavelength has been investigated, with the aim to optimize laser parameters with respect to emission wavelength and output power. Close to emission wavelength, the optical signal-to-noise ratio is higher than 65 dB. We also investigate that the initial oscillation is damped oscillation, and the laser output become steady-state output one millisecond later.
This paper presents a theoretical and numerical analysis of polarization properties used as Doppler velocimetry in Vertical-Cavity Surface-Emitting lasers. A good match is found between numerical results and reported experiment results. We show that condition of generating square waves is the VCSELs must operated inside the bistable region and frequency difference between two linear polarization modes is equal to several certain values. We can select proper VCSELs which frequency difference between two linear polarization modes is multiple of ±3G to obtain asymmetric waveform of self-mixing signal.
A new, compact laser Doppler velocimetry is proposed, which is composed of a single-mode vertical-cavity surface-emitting laser modulated by a dynamical triangular current and a collimating lens. It can indicate the direction of velocity without ambiguity in the wide dynamic range of 5.2mm/s to 479.9mm/s when the sampling time is 0.1 second in the measurement. The accuracy of velocity measurement is better than 3.1% in the whole velocity range. What's more, this LDV works very well on different diffusing surfaces, even on a black glossy photographic paper.
Multimode interference optical pulse power splitters for 1.053μm wavelength have been designed in this paper. The guided mode propagation analysis method is used to analyze the working principle of MMI power splitter. We designed the power splitters base on the analysis. Then finite difference beam propagation method (FDBPM) was used to analyze the splitting performance of the devices. At last, we analyzed the temporal performance of the device (such as pulse broaden) working for optical pulse input with the Finite Difference Time Domain (FDTD) method. The dispersion properties for ultra short 1.053μm optical pulses input were analyzed.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.