Abstract: A process and apparatus is disclosed for growing a crystal ribbon (42) of a substance of theoretically infinite length from a melt (32) of the substance. A pair of fixedly positioned edge defining members (44) are partially submerged into the melt (32) so as to break the surface (34) of the melt (32) at a predetermined distance from one another. The edge defining members (44) are wettable by the melt and the predetermined distance substantially corresponds to the width of the crystal ribbon (42) to be grown. The crystal ribbon (42) is grown by contacting the surface (34) of the melt (32) with a seed ribbon (38) between the edge defining members (44) whereby a meniscus (48) of the melt (32) is established on the seed ribbon (38). The meniscus (48) is stabilized by the meniscus (50) of the melt (32) on the edge defining members (44). Pulling the seed crystal ribbon (38) away from the melt (32) results in continuous growth of the crystal ribbon (42).

Abstract: A method and apparatus for correcting doppler shifts in synthetic aperture radar data. More particularly, in an optical correlator (10) for synthetic aperture radar data having a means for directing a laser beam (22) at a signal film (12) having radar return pulse intensity information recorded thereon, a resultant laser beam (32) then passing through a range telescope (34), an azimuth telescope (38), and a Fourier transform filter (36) located between the range and azimuth telescopes, thereby forming an image for recordation on an image film (40), a compensation means for doppler shift in the radar return pulse intensity information includes a beam splitter (46) for reflecting the modulated laser beam, after having passed through the Fourier transform filter (36), to a detection screen (48) having two photodiodes (66 and 68) mounted thereon. The photodiodes are positioned on each side of the Gaussian distribution of the Fourier transform spectrum reflected by the beam splitter (46).

Abstract: A window comparator comprising two operational amplifiers, a first one with two feedback circuits, each feedback circuit having a diode connected to the amplifier output and poled for forward current conduction of opposite polarity, to provide an algebraic difference between an input signal and a selected set-point voltage such that one diode conducts and then switches off while the other is held off and then conducts when the sign of the algebraic difference switches. Differential input terminals of the second operational amplifier are connected to the separate feedback circuits of the first operational amplifier, one input terminal to the output of one diode, and the other to the output of the other diode.