Noiseless amplification of optical images

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Abstract
We propose a scheme for amplification of faint optical images with coherent light which preserves the signal-to-noise ratio in the image. The scheme consists of a ring-cavity optical parametric amplifier as an active element and two imaging lenses. This system can amplify images either ‘‘point by point,’’ when a small region is amplified at a time, or by narrow rings, depending on its operation; in both cases it works as an image scanner. We have evaluated the inherent noise of this amplification scheme which has its physical origin in the phenomenon of spontaneous parametric radiation. This noise gives a lower ultimate limit for the intensity of the image that can be noiselessly amplified by our scheme. We have estimated spatial resolution of the scheme and formulated criteria for its noiseless operation.