Optical Deformations Research Articles

Upgrade of NewSUBARU with Superconducting Magnets

There is an attractive possibility that the critical energy of synchrotron radiation of the NewSUBARU can be increased by introducing superconducting (SC) magnets in the storage ring. In this paper, the effect of 5 T SC magnets on lattice functions of the ring is discussed. There are two possibilities of introducing the SC magnets: one is by replacing the inverse bending magnet with a SC magnet and the other is by installing a SC wiggler. With the former, there is negligible effect on the beam optics and the expected vertical tune shift can be easily corrected by adjusting two quadrupole magnets in the short straight section. With the latter, there are no serious problems, but it is necessary that additional quadrupole magnets are placed at both ends of the wiggler in order to reduce the deformation of electron beam optics.

Analysis of thermal aberrations in a high average power single-stage Ti:sapphire regenerative chirped pulse amplifier: Simulation and experiment

We present a systematic investigation of thermal loading effects in single-stage high average power regenerative chirped pulse amplifiers based on Ti:sapphire. Using finite element analysis (FEA), we compute the temperature distributions, optical path deformations (OPDs), and corresponding thermal focal lengths for a variety of pumping conditions. We experimentally characterize thermal aberrations in a regenerative amplifier using a variety of techniques (interferometry, pump-probe thermal lens power, and M2 analysis). We find excellent agreement between the FEA modeling and experimental measurements of OPDs. Our methods allow us to predict the optimal pumping conditions for minimizing thermal aberrations for a variety of geometries and pumping conditions.

The Large Binocular Camera Image Simulator

ABSTRACTThe Large Binocular Camera Image Simulator (LBCImSim) is a package for generating artificial images in the typical FITS format. It operates on real or artificial images, simulating the expected performances of real instruments by including several observing conditions (filters, air mass, flat field, and exposure time) and creating images with the LBC instrumental artifacts (optical deformations, noise, and CCD architectures). This simulator can also be used to produce artificial images for other existing and future telescopes, since its structure is very flexible. The primary aim of LBCImSim is to support the development of a pipeline and data analysis procedure that is able to handle wide‐field imaging and the fast reduction of huge amounts of photometric data. The software consists of three stand‐alone programs written in C that use IRAF and run on Linux OS. In this paper, we first describe the software, its performance in several tests carried out prior to public release, and some examples for users. In particular, we compare the Hubble Deep Field–South (HDF‐S) as seen by FORS1 with a simulated image and found that the agreement is good. We then use this software to predict the expected performances of the LBC instrument by means of realistic simulations of deep‐field observations with the Large Binocular Telescope.

Simulating a Dual-Recycled Gravitational Wave Interferometer with Realistically Imperfect Optics

We simulate the performance of a gravitational wave interferometer in the Dual Recycling (DR) configuration, as will be used for systems like Advanced-LIGO. Our grid-based simulation program models complex interferometric detectors with realistic optical deformations (e.g., fine-scale mirror surface roughness). Broadband and Tuned DR are modeled here; the results are also applied qualitatively to Resonant Sideband Extraction (RSE). Several beneficial properties anticipated for DR detectors are investigated: signal response tuning and narrowbanding, power loss reduction, and the reclamation of lost power as useful light for signal detection. It is shown that these benefits would be limited by large scattering losses in large (multi-kilometer) systems. Furthermore, losses may be resonantly enhanced (particularly for RSE), if the interferometer's modal resonance conditions are not well chosen. We therefore make two principal recommendations for DR/RSE interferometers: the DR/RSE cavity must be modally nondegenerate; and fabricated mirror surfaces and coatings must be as smooth as is practically feasible.

The perception of surface orientation from multiple sources of optical information

An orientation matching task was used to evaluate observers' sensitivity to local surface orientation at designated probe points on randomly shaped 3-D objects that were optically defined by texture, lambertian shading, or specular highlights. These surfaces could be stationary or in motion, and they could be viewed either monocularly or stereoscopically, in all possible combinations. It was found that the deformations of shading and/or highlights (either over time or between the two eyes' views) produced levels of performance similar to those obtained for the optical deformations of textured surfaces. These findings suggest that the human visual system utilizes a much richer array of optical information to support its perception of shape than is typically appreciated.

Perception of rigid motion in depth from the optical deformations of shadows and occlusion boundaries.

Three experiments were designed to examine the abilities of observers to determine an object's 3-dimensional structure and motion from various types of optical deformations. Observers were required to discriminate whether pairs of moving ellipsoids were rotating rigidly about a single axis or nonrigidly about different axes that varied in slant. Discrimination thresholds were significantly influenced by whether the ellipsoids were intersecting or nonintersecting and whether they contained identifiable texture elements. Performance was unaffected by precession movements of the axis of rotation, by increasing the number of intersecting ellipsoids beyond 2, or by replacing the deforming silhouettes with the projected motions of cast shadows presented in isolation against a planar background. These findings indicate that observers can perceive structure from motion based on several different types of optical deformation, including the deformations of shadows and silhouettes that do not contain identifiable features on which most existing theoretical analyses are designed to operate.

Perception of rigid motion in depth from the optical deformations of shadows and occlusion boundaries.

Perception of rigid motion in depth from the optical deformations of shadows and occlusion boundaries.

Analytical Method for Image Characteristics of Annular Illumination with a Spatial Filter in Optical Projection Lithography

Annular illumination with a spatial filter, or SSBL (single-sideband optical lithography), has performance equivalent to phase shifting in optical column technology. This paper presents an analytical method for examining image deformation characteristics in optical projection systems including SSBL. We express image intensity as the sum of a symmetric and an antisymmetric component. Image deformation can be clearly observed by using the antisymmetric component. From the point of view of proximate interaction, we show that the real part of mutual intensity is useful in interpreting image deformations. Optical image deformations are unavoidable in the range of 0.2-0.3 µm at the KrF-line wavelength. We present a simplified correction method for mask data which reduces computational time.

Epileptic activity of the occipital lobe. Clinico-electroencephalographic contribution

Our analysis of the course of illness in 14 patients, whose common electroencephalographic characteristic was epileptogenic activity in the occipital area, showed very different clinical symptoms. The first group comprised patients who presented bilateral amaurosis. In four of these cases, the occipital hypersynchronous EEG activity was merely a secondary symptom of either ischaemic hypoxia or of a degenerative process in the occipital visual cortex and was not responsible for the genesis of the actual blindness. In two further cases of monosymptomatic temporary loss of vision, it was difficult to make a differential diagnosis between ictal blindness, respectively status epilepticus amauroticus occurring in a occipital lobe epilepsy and a migraine attack involving the basilar territory. The second group comprised five patients with paroxysmal visual hallucinations respectively illusions. Three of them suffered from hallucinations of the elementary type, respectively flickering fits in the hemianopic field, symptoms which are based on discharges in the visual cortex of the occipital lobe. In a case of one patient with complex visual hallucinations as well as in a further case with visual illusions, it was not possible to find out with certainty their place of origin. A study of these cases shows that the cortical or sub-cortical functional disturbance within the visual system causing the various optical deformations and visual hallucinations, form an inhomogeneous group with different etiology. In the only patient belonging to the third group, whose seizures were i.a. characterized through motor phenomena in the field of the ocular organs and the tonic lateral turning movement of the bulbi of the eyes and of the head, an occipital epileptic crisis with spread of discharges from the occipital pole to the frontomesial surface should be assumed. The occurrence of complex partial seizures, respectively generalized tonic-clonic attacks in two patients of the fourth group who have definite epileptogenic EEG-activity in the occipital area, can be explained by a propagation of paroxysmal activity to the temporal lobe or to the motor cortex. Because of the marked tendency to propagation of the hypersynchronous activity originating in the occipital lobe, many combinations of sensory and/or motor symptoms can occur within the frame-work of occipital epileptic seizures. On the basis of one scalp EEG finding, no final localizing conclusions may be drawn here.

Perception of structure from motion: Is projective correspondence of moving elements a necessary condition?

A fundamental assumption of almost all existing computational analyses of the perception of structure from motion is that moving elements on the retina projectively correspond to identifiable moving points in three-dimensional space. The present investigation was designed to determine the psychological validity of this assumption in several different contexts. The results demonstrate that the ability of human observers to perceive structure from motion is much more general than would be reasonable to expect on the basis of existing theory. Observers can experience a compelling kinetic depth effect even when the pattern of optical motion is contaminated by large amounts of visual noise (e.g., where the signal to noise ratio is less than 0.15). Moreover, the optical deformations of shading, texture, or self-occluding contours, which would be treated as noise by existing computational models, are analyzed by human observers as perceptually salient sources of information about an object's three-dimensional form. These results suggest that the modular analyses of visual information that currently dominate the literature will have to be modified if they are to account for the high level of generality exhibited by human observers.

Perception of structure from motion: is projective correspondence of moving elements a necessary condition?

A fundamental assumption of almost all existing computational analyses of the perception of structure from motion is that moving elements on the retina projectively correspond to identifiable moving points in three-dimensional space. The present investigation was designed to determine the psychological validity of this assumption in several different contexts. The results demonstrate that the ability of human observers to perceive structure from motion is much more general than would be reasonable to expect on the basis of existing theory. Observers can experience a compelling kinetic depth effect even when the pattern of optical motion is contaminated by large amounts of visual noise (e.g., where the signal to noise ratio is less than 0.15). Moreover, the optical deformations of shading, texture, or self-occluding contours, which would be treated as noise by existing computational models, are analyzed by human observers as perceptually salient sources of information about an object's three-dimensional form. These results suggest that the modular analyses of visual information that currently dominate the literature will have to be modified if they are to account for the high level of generality exhibited by human observers.

Fluctuation effects as a cause for the incommensurate phase formation

Abstract Considered the influence of fluctuation effects near the second order phase transition points on the possibilities of formation of the incommensurate superstructures. For the crystals with perovskite structure such a possibility holds near the ferroelectric phase transition point due to the certain coupling between accoustic and optical deformations. The mechanism, explaining formation of the incommensurate phase in quartz near the α ⇄ β transition point is proposed.