Fourier-based image sharpness sensor for adaptive optics correction

Adaptive optics reduces undesirable turbulence effects present during propagation and imaging through the atmosphere or another random medium. Within an adaptive optics system, wavefront sensing determines the incoming wavefront errors. Image sharpening is one method of wavefront sensing where the sharpness value is measured from the image intensity based on a given sharpness metric. The wavefront correction device is then perturbed until the sharpness value is maximized. The key to image sharpening is defining sharpness with a sharpness metric that reaches a maximum when wavefront error is zero. Present image sharpness metrics often use the image intensity. In contrast, this dissertation introduces four novel sharpness metrics based on the Fourier transform of the image. Since high spatial frequencies carry information about the image’s edges and fine details, taking the Fourier transform and maximizing the high spatial frequencies sharpens the image. Coherence of the illumination source and the sharpness metric choice determine which of the presented optical system configurations to use. Performances of the Fourier-based sharpness metrics are observed and compared by measuring the sharpness value while adding defocus to the system. If the sharpness value reaches a maximum with zero wavefront error then the sharpness metric is successful. This investigation continues by adding astigmatism, coma, and spherical aberration and measuring the sharpness value to see the affect of these higher order aberrations. The sharpness metrics are then implemented into a simple manual closed-loop correction system. This dissertation presents successful performance results of these novel Fourier-based sharpness metrics showing great promise for use in adaptive optics correction

Finite field-energy of a point charge in QED

We consider a simple nonlinear (quartic in the fields) gauge-invariant modification of classical electrodynamics, which possesses a regularizing ability sufficient to make the field energy of a point charge finite. The model is exactly solved in the class of static central-symmetric electric fields. Collation with quantum electrodynamics (QED) results in the total field energy about twice the electron mass. The proof of the finiteness of the field energy is extended to include any polynomial selfinteraction, thereby the one that stems from the truncated expansion of the Euler-Heisenberg local Lagrangian in QED in powers of the field strenth

Triangular and Y-shaped hadrons with static sources

The structure of hadrons consisting of three static color sources in fundamental (baryons) or adjoint (three-gluon glueballs) representations is studied. The static potentials of glueballs as well as gluon field distributions in glueballs and baryons are calculated in the framework of field correlator method.Comment: 7 pages, 5 figures, talk at the NPD-2002 Conference, December 2-6, ITEP, Moscow, reference adde

An Evolutionary Perspective on Pain Communication

Pain serves as a signal to elicit care from others. In turn, displaying pain might be attractive because of the benefits it might bring. Additionally, displaying pain is easy, because helpers distinguish poorly between genuine pain and faked pain. Hence, helpers face the problem of distinguishing true sufferers from free riders, while sufferers face the problem of communicating need convincingly. This article will propose solutions to these adaptive problems. Based on theoretical arguments and on empirical insights from lie detection research, it will be argued that the credibility of pain signals cannot be found in features of the signal itself, but in its context. Namely, pain is obviously credible when the context features unforgeable cues, such as an open wound or the enlarged abdomen of a pregnant woman, but also external cues such as the ice water in cold pressor tasks. In absence of such cues, pain can become credible through costly consequences, such as refraining from rewarding behaviors for a significant period. However, these adaptive mechanisms for communicating need may not be shaped for modern circumstances such as experimental settings and therapeutic encounters