Louis Sica

INTERFEROMETRIC OBSERVATION OF ABSORPTION INDUCED INDEX CHANGE ASSOCIATED WITH THERMAL BLOOMING

The induced index changes associated with thermal blooming have been observed in iodine‐doped CCl4 by means of a Mach‐Zehnder interferometer. The interference fringe shape next to the window and the temporal growth of the peak fringe displacement at various positions in the cell have been analyzed. Both the conductive and convective stages of thermal blooming are observed.

Bell's inequalities: I: An explanation for their experimental violation

Derivations of two Bells inequalities are given in a form appropriate to the interpretation of experimental data for explicit determination of all the correlations. They are arithmetic identities independent of statistical reasoning and thus cannot be violated by data that meets the conditions for their validity. Two experimentally performable procedures are described to meet these conditions. Once such data are acquired, it follows that the measured correlations cannot all equal a negative cosine of angular differences. The relation between this finding and the predictions of quantum mechanics is discussed in a companion paper.

Local instances of good seeing

Abstract One of the major causes of image degradation in imaging through an inhomogeneous medium with small aperture optics, or through an uneven boundary layer, is a local tilt term in the expression for the incoming wavefront. This manifests itself as a local or space variant distortion of the image. When a temporal sequence of such images is examined, there is wandering of the image both locally and as a whole. In this paper we describe a time selection technique which has been employed to correct for the image wandering using multiple frame image sequences. The average of many short exposures, the equivalent of one long exposure, is computed in a first pass through the images. Then in a second pass, the local image regions which are shifted too far from the long term average are deleted, while the centroids of those remaining are reregistered with respect to the equivalent long exposure. Such a two pass technique is mathematically analyzed and demonstrated experimentally with a sequence of images of an underwater bar.

Interferometric observations of kinetic cooling

By using a three‐beam interferometer, the time constant associated with kinetic cooling has been measured as a function of water vapor concentration in atmospheres of N2 with fixed CO2 concentrations in the 400‐ to 800‐ppm range. Measurements have also been made in similar atmospheres with the addition of 10% O2. Least‐squares fits to the data are consistent with theoretical predictions when extrapolated to zero water vapor concentration. When water vapor is important, however, the experimentally observed relaxation times are considerably shorter than the predicted times.

Bell's inequalities. II : Logical loophole in their interpretation

Assumed data streams from a delayed choice gedanken experiment must satisfy a Bells identity independently of locality assumptions. The violation of Bells inequality by assumed correlations of identical form among these data streams implies that they cannot all result from statistically equivalent variables of a homogeneous process. This is consistent with both the requirements of arithmetic and distinctions between commuting and noncommuting observables in quantum mechanics. Neglect of these distinctions implies a logical loophole in the conventional interpretation of Bells inequalities.

Correlations for a new Bell’s inequality experiment

Proofs of Bell’s theorem and the data analysis used to show its violation have commonly assumed a spatially stationary underlying process. However, it has been shown recently that the appropriate Bell’s inequality holds identically for cross correlations of three or four lists of ±l’s, independently of statistical assumptions. When data consistent with its derivation are analyzed without imposition of the stationarity assumption, the resulting correlations satisfy the Bell inequality.

Estimator and signal-to-noise ratio for an integrative synthetic aperture imaging technique

An imaging system is described which uses the following concepts: laser illumination of objects, nonredundant apertures, and phase closure. A sparse transmitter array is envisioned, each aperture of which emits at a different laser frequency such that any pair of beams gives rise to a unique beat signal. The light reflected by an object thus irradiated is sensed by a spatially integrating detector array. An estimator is given for the Fourier components of the object at spatial frequencies corresponding to the unique temporal beats sensed by the receiver array. The standard deviation of the estimator is computed taking both shot noise and laser speckle into account. It is found that the signal-to-noise ratio for both kinds of noise increases with the square root of the area of the detector array. This allows the signal-to-noise ratio of the system to be increased independent of the resolution.

Use of a sharpness criterion in correcting images degraded by random distortion

A sharpness criterion for space-variant imaging through a random medium was recently proposed. It uses ensemble-averaged images to provide the information ordinarily given by space invariance. This criterion is used to construct an algorithm for the correction of randomly distorted one-dimensional images degraded by Gaussian-distributed stretching functions of variable correlation length. It is shown theoretically and demonstrated in the simulation that knowledge of the shape of the distortion-induced transfer function allows the width of the function to be determined from the processing procedure. In the simulation, distortion-degraded sinusoids with an average visibility of 2% before processing yield a resultant sinusoid with a visibility of 80–90% after processing. Under equivalent conditions, corrections of block objects may be carried out with 100% accuracy. It should be possible to use a similar procedure to improve real imagery degraded by atmospheric turbulence.

Three Beam Interferometer for the Observation of Kinetic Cooling in Air

A three beam interferometer, which has recently been used to measure the time constant associated with kinetic cooling, is described in detail. Design features necessitated by operation of the device over a 5-m path are discussed, as well as system response to vibrational noise and drift, and means used for their monitoring and control. The effective working length resolution of the system, dL/L, was 1 part in 2.6 x 10(9) with a He-Ne laser source operating at 0.63 microm.

Bell's inequality violation due to misidentification of spatially non-stationary random processes

Abstract Correlations for the Bell gedankenexperiment are constructed using probabilities given by quantum mechanics, and non-local information. They satisfy Bells inequality and exhibit spatial non-stationarity in angle. Correlations for three successive local spin measurements on one particle are computed as well. These correlations also exhibit non-stationarity, and satisfy the Bell inequality. In both cases, the mistaken assumption that the underlying process is wide-sense-stationary in angle results in violation of Bells inequality. These results directly challenge the wide-spread belief that violation of Bells inequality is a decisive test for non-locality.