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We present an approach to recover scenes deteriorated by reflections off a semireflecting medium (e.g., a glass window). The method, based on imaging through a polarizer at two or more orientations, separates the reflected and transmitted scenes and determines which is which. We analyze the polarization effects, taking into account internal reflections within the medium. The scene reconstruction requires the estimation of the orientation (inclination and tilt angles) of the transparent (invisible) surface. The inclination angle is estimated by seeking the value that leads to the minimal mutual information of the estimated scenes. The limitations and the consequences of noise and angle error are discussed, including a fundamental ambiguity in the determination of the plane of incidence. Experimental results demonstrate the success of angle estimation and consequent scene separation and labeling.

Conventional architectures for the implementation of Boolean logic are based on a network of bistable elements assembled to realize cascades of simple Boolean logic gates. Since each such gate has two input signals and only one output signal, such architectures are fundamentally dissipative in information and energy. Their serial nature also induces a latency in the processing time. In this paper we present a new, principally non-dissipative digital logic architecture which mitigates the above impediments. Unlike traditional computing architectures, the proposed architecture involves a distributed and parallel input scheme where logical functions are evaluated at the speed of light. The system is based on digital logic vectors rather than the Boolean scalars of electronic logic. The architecture employs a novel conception of cascading which utilizes the strengths of both optics and electronics while avoiding their weaknesses. It is inherently non-dissipative, respects the linear nature of interactions in pure optics, and harnesses the control advantages of electrons without reducing the speed advantages of optics. This new logic paradigm was specially developed with optical implementation in mind. However, it is suitable for other implementations as well, including conventional electronic devices.

Propagation invariance is extended in the paraxial regime, leading to a generalized self-imaging effect. These wave fields are characterized by a finite number of transverse self-images that appear, in general, at different orientations and scales. They possess finite energy and thus can be accurately generated. Necessary and sufficient conditions are derived, and they are appropriately represented in the Gauss-Laguerre modal plane. Relations with the following phenomena are investigated: classical self-imaging, rotating beams, eigenFourier functions, and the recently introduced generalized propagation-invariant wave fields. In the paraxial regime they are all included within the generalized self-imaging effect that is presented. In this context we show an important relation between paraxial Bessel beams and Gauss-Laguerre beams. © 2000 Optical Society of America [S0740-3232(00)