Abstract: A linear array of photoemitters and photodiodes are positioned on opposite sides of currency paper for denomination and verification determination under transmitted light. The photoemitters are arranged for projecting an image of the indicia printed on the security thread embedded within the currency paper. The photodiodes receive the image and connect with a processor circuit which determines the presence or absence of the security feature, reads the denomination indicia and correspondingly provides indication thereof. The processor contains stored information identifying currency denomination and a comparison is made at the time of verification to also determine the denomination of the proffered currency.

Abstract: A linear array of photodiode and phototransistor pairs are positioned on opposite sides of currency paper for denomination determination under reflected light and for verification determination under transmitted light. The focus of one of the photodiodes in each pair is precisely adjusted for the top surface of the currency paper. The focus of the other photodiode in each pair is slightly out of focus at the top surface. A phase diversity algorithm integrates the successive images from both photodiodes to form a clear image. A processor determines the presence or absence of the security feature and correspondingly provides visual or audible indication thereof. The processor contains stored information identifying currency denomination and a comparison is made at the time of verification to also determine the denomination of the proffered currency.

Abstract: Achromatic volume holograms are attained for broad band phase conjugation and image reconstruction having bandwidths of 250 nanometers. The holograms are generated by means of a diffraction grating having a predetermined angle of tilt. Achromaticity is achieved by tilting the holographic recording medium at the same predetermined angle.

Abstract: Adaptive optics with controllable delay in a matrix of regions focuses the image of an object upon a detector array in an image plane that provides a signal set representative of the radiant energy incident upon a matrix of locations in the image plane. An image signal processor processes this signal set to provide a wavefront error signal representative of the estimated wavefront phase distortion of the radiant energy incident upon the detector array. A control system responds to this wavefront error signal to effect alteration of the phase delay introduced by the adaptive optics to reduce the phase distortion of radiant energy incident upon the detector array.