Adaptive optics (AO) systems take sampled measurements of the wave-front phase. Because in the general case the spatial-frequency content of the phase aberration is not band limited, aliasing will occur. This aliasing will cause increased residual error and increased scattered light in the point-spread function (PSF). The spatially filtered wave-front sensor (SFWFS) mitigates this phenomenon by...

This paper evaluates the role of various stages in the human visual system in the detection of spatial patterns. Contrast sensitivity measurements were made for interference fringe stimuli in three directions in color space with a psychophysical technique that avoided blurring by the eye's optics including chromatic aberration. These measurements were compared with the performance of an ideal o...

Registry versus clinical trial The main goal of pregnancy registries includes the rapid identification of signals of increased teratogenic risk as quickly as possible, which is especially important for newly available anti epileptic drugs (AEDs) [1–3]. When the association between an increased risk and an AED is found in a registry, the cause can be further explored in a case–control study or a...

Functional magnetic resonance imaging (fMRI) is a non-invasive and powerful imaging tool for detecting brain activities. The majority of fMRI studies are performed with single-shot echo-planar imaging (EPI) due to its high temporal resolution. Recent studies have demonstrated that, by increasing the spatial-resolution of fMRI, previously unidentified neuronal networks can be measured. However, ...

Contrast sensitivity for orientation discrimination is limited to spatial frequencies below 50-60 cycles per degree by neural spatial integration, and we find that contrast sensitivity, measured using an orientation-discrimination criterion, declines sharply with increasing spatial frequencies in that range. Yet interference fringe patterns pulsed at constant mean luminance can be detected at s...

The satellite mission GRACE (Gravity Recovery and Climate Experiment) provides monthly solutions of the global gravity field of the Earth. Temporal variations in gravity reflect mass redistributions over the Earth. Those mass movements are caused by physical phenomena such as ice sheet dynamics, accumulation of hydrological masses over land, the dynamics in the solid Earth and the dynamics in t...

The discrete sampling of a wave-front using a Shack-Hartmann sensor limits the maximum spatial frequency we can measure and impacts sensitivity to frequencies at the high end of the correction band due to aliasing. Here we present Wiener filters for wave-front reconstruction in the spatial-frequency domain, ideally suited for systems with a high number of degrees of freedom. We develop a theore...

Visual display systems such as the out-the-window or head-down displays of a simulator present a visual scene that is sampled in both the spatial domain (by the display resolution) and the time domain (by the display refresh rate). For a given human visual temporal sensitivity, spatial-frequency content of the scene, and speed of the image motion, spatiotemporal aliasing can occur when the imag...

Given an occlusion graph for a group of objects that contains no binary cycles, and a set of antialiased images with transparency for each of the (isolated) objects, image compositing operators can be used to produce a correct, antialiased image of the objects with hidden surfaces eliminated. We show how an appropriate image compositing expression is derived given the occlusion graph, and how t...

We find the explicit forms of the anti–de Sitter plane, anti–de Sitter spherical, and pp waves that solve both the linearized and exact field equations of the most general higher derivative gravity theory in three dimensions. As a subclass, we work out the six-derivative theory and the critical version of it where the masses of the two spin-2 excitations vanish and the spin-0 excitations decouple.