Abstract: In a method for detecting changes in a scene by detecting the differences between first and second images of the scene taken at different times the first and second images are registered and a distance value d representing the average displacement, in pixels, between the two images after registration is determined. A pixel in the first image (x.sub.0, y.sub.0) and a corresponding pixel (x.sub.1, y.sub.1) at the same location in the second image (x.sub.0 =x.sub.1 and y.sub.0 =y.sub.1) are defined. For each pixel (x.sub.0, y.sub.0) in the first image, a search through each of the pixels in a neighborhood of the second image, (x.sub.1 +.DELTA.x, y.sub.1 +.DELTA.y), where .DELTA.x=0, .+-.1, . . . , .+-.d and .DELTA.y=0, .+-.1, . . . , .+-.d is conducted to find the pixel that is closest in value to the value of pixel (x.sub.0, y.sub.0 ) by taking the absolute value of the difference between the value of the pixel at (x.sub.0, y.sub.0 ) and the value of each of the pixels, (x.sub.1 +.DELTA.x, y.sub.1 +.DELTA.

Abstract: Disclosed is fresnel lens apparatus for optically coupling a plurality of data channels between stationary and rotating systems. Each data channel of the apparatus includes an optical data transmitter, an optical data receiver and a fresnel lens optical element. The plurality of fresnel lens optical elements are preferably annular and arranged concentrically in a plane. Each fresnel lens optical element focuses the optical data from a transmitter to a respective receiver which is positioned off axis with respect to the central axis of the concentric optical elements.

Abstract: Disclosed is optical data signal apparatus for optically coupling a plurality of data channels between stationary and rotating systems. The optical data signal apparatus is useful in a rotary head scanner for coupling a plurality of data channels between a rotating head wheel, having a plurality of magnetic record/reproduce heads, and stationary signal processing circuitry. Each data channel of the apparatus includes an optical data signal transmitter, an optical data signal receiver and an optical coupling element for causing an optical data signal transmitted by the transmitter to be focused on the receiver. The plurality of optical coupling elements are preferably annular and arranged concentrically in a plane. Each optical coupling element focuses the optical data from a transmitter to a respective receiver which is positioned off axis with respect to the central axis of the concentric optical elements. Preferably the optical elements are holographic optical elements.

Abstract: An objective lens is affixed to a permanent magnet which in turn is affixed to an electret material having an inherent charge. A support structure for the permanent magnet is formed from an array of electromagnets which partially surround the permanent magnet. Current signals are controllably applied to the electromagnets to generate a magnetic support field for supporting the permanent magnet and its mounted objective lens. Sensors are provided for sensing the charge inherent in the electret material as a function of the position of the electret material from the sensors. The sensors provide position signals to a control device, such as a microprocessor, which control device provides current signals to the electromagnet array to position the permanent magnet and the associated objective lens at a desired position.

Abstract: A transducer head, held in a fixed position as a preformatted disk is rotated a full revolution, reads any sector address accessible to the head. The addresses read come from a plurality of track revolutions that depend on the magnitude of the eccentricity of the disk. A computer, programmed with a least squares algorithm, first coordinates (1) data corresponding to the angular position of the disk each time an address is read, with (2) data corresponding to the actual radius of each address.

Abstract: A tape cassette that includes a rotatable drum having a centrally disposed tape storage device and a surrounding circumferential wall with one or more openings therein through which tape passes from the storage device to and helically around the outer surface of the wall and then back inside the drum. A cooperating recorder/reader head is mounted outside the drum in alignment with the tape to record/read a slant track thereon as the drum rotates. The tape storage device may be indexable to to incrementally advance the tape along the wall surface, or the head may be indexable so as to incrementally move across the tape, each time the drum completes one revolution, to thereby record/read a succession of slant tracks as the drum rotates through successive revolutions. Such a cassette offers the combined advantages of a fast-access disk and a mass-storage tape.