Abstract: By applying a spatial frequency dependent phase compensation in an optical heterodyning system, a variable rf delay line can be synthesized. The system is able to generate continuously variable phased microwave signals over a prescribed frequency band. A primary application of these variable delay lines is in the area of phased array antenna systems. Because the phototonic delay line synthesizes true time delay, it can be used as part of wide bandwidth system to achieve 100% fractional bandwidth without beam squint. The system lends itself to an optically integrated implementation using a 2-D deformable mirror device to achieve very high packing density which is very useful for an adaptive transversal filter.

Abstract: Optical systems are disclosed which are capable of generating and rapidly changing time delays of electrical signals for true time delay beam formation and beam steering. The systems utilize an interferometer configuration. A first optical modulator and a Fourier transform lens define a Fourier transform plane in a first leg of the interferometer. In a second leg of the interferometer, a second optical modulator provides beam steering to a prism stack, which produces a set of plane reference waves having a range of orientations required to generate a desired range of time delays. Preferably the optical modulators are acousto optic Bragg cells. Alternatively, a holographic optic element could be used in place of the prism stack.

Abstract: An optical apparatus for aligning a reticle and a wafer together in connection with reduction projection onto the wafer of an image of a circuit pattern formed on the reticle. Two light beams having slightly different frequencies are concurrently applied to alignment gratings on the reticle and alignment gratings on the wafer through the windows on the reticle and a reduction projection lens. Heterodyne signals of interference rays resulting from diffraction by the alignment gratings on the reticle of the light applied to the alignment gratings are caught by a first optical sensor. Heterodyne signals of interference rays resulting from diffraction by the alignment gratings on the wafer of the light applied to the alignment gratings are caught by a second optical sensor. The difference in phase of the heterodyne signals detected by the respective optical sensors is detected by a phase meter, and the position of the wafer relative to the reticle is adjusted so that the phase difference is reduced to zero.

Abstract: A light beam frequency comb generator uses an acousto-optic modulator to generate a plurality of light beams with frequencies which are uniformly separated and possess common noise and drift characteristics. A well collimated monochromatic input light beam is passed through this modulator to produce a set of both frequency shifted and unshifted optical beams. An optical system directs one or more frequency shifted beams along a path which is parallel to the path of the input light beam such that the frequency shifted beams are made incident on the modulator proximate to but separated from the point of incidence of the input light beam. After the beam is thus returned to and passed through the modulator repeatedly, a plurality of mutually parallel beams are generated which are frequency-shifted different numbers of times and possess common noise and drift characteristics.

Abstract: An acousto-optical classifier for classifying wide bandwidth signals such as high resolution radar returns of ships or very short pulse length signals of radar emitters. This is accomplished by generating the Fourier transform power spectrum with an acousto-optic cell oriented in the Bragg configuration and a low power coherent light source such as a laser. The power spectrum is detected to provide inputs to a digital classifier.

Abstract: An acousto-optical modulation device comprises a plurality of acousto-optic modulators arranged in series with each other, to receive a zero-order light from a previous stage of the modulators. A zero-order light emerging from the last stage is used as a modulated light of an incident light. The coefficient of extinction for the zero-order light is raised by this structure, and the acousto-optic modulation device presents a high diffraction efficiency and a high value of the coefficient of extinction at the same time.

Abstract: The invention is a method for obtaining fringe visibility in hybrid-optical interferometric processors. Encoded data defining an image is utilized to provide both a timing input signal and a method of modulating a light source in synchronization with the modulation of an optical-acoustical element. The modulated light is then detected in a receptor array and converted into signals suitable for driving a readable, visual-imaging device or other devices for image analysis.