Abstract: A wavefront sensor employs a novel DC shearing interferometer which produces four interferograms which are 90.degree. phase shifted with respect to each other. The incoming wavefront is replicated into two beams, a portion of each being reflected off of a beamsplitter and the remaining portion being transmitted therethrough, at first and second portions of the beamsplitter. After leaving the beamsplitter the transmitted and reflected beams are reflected back 180.degree. by a pair of retroreflectors, and directed at third and fourth portions of the beamsplitter. The retroreflectors are adjusted to produce four shearing interferograms and a quarter wave plate is positioned in the path of one of the beams to cause the four interferograms to have a 90.degree. phase shifted relationship with respect to each other.

Abstract: Apparatus and method for encoding and decoding a signal which is divided into a plurality of signal lines, each of which is a successive line of pixel signal values taken from a two-dimensional informational field. The apparatus for encoding includes the following elements: means for deriving a neighborhood value representing the pixel signal values taken from the two-dimensional field in the neighborhood of a pixel signal value to be encoded, which neighborhood value is based, at least in part, on a pixel signal value in another signal line than that in which the pixel signal value to be encoded is located: means for deriving the difference between the neighborhood value and the pixel signal value to be encoded; and means for outputting the difference as the encoded representation of the pixel signal value to be encoded.

Abstract: A text line bounding system for non-mechanically adjusting for skewed text in scanned text. The data from scanned page texts are divided into vertical swaths and all pixels at respective vertical levels within each swath are set black if any one pixel within the swath at the level is black. Intersections and terminations are found and the datum for each line is established after removing extraneous data. The skew angle of the text is then established, following which the text lines are statistically bounded. The actual text data is then rotated according to the orientation established for conventional processing.

Abstract: A long period buried optical grating is fabricated by polishing a number of single crystal silicon wafers to identical thicknesses and flat figure, applying a light reflective metallic coating to the wafers, thereafter bonding the wafers together in a stack, and thereafter lapping the resulting stack of bonded layers at an acute angle with respect to the major planar surfaces of the wafers to form the buried grating, such grating having optically flat reflective sawtoothed elements. The grating period may be readily controlled by changing the acute angle and/or the thickness of the silicon wafers.

Abstract: The invention relates to a magnetically switchable magneto optic composite comprising an epitaxial film supported on a non-magnetic garnet substrate. The film is a bismuth-containing film which is in compression, contains a combination of cations providing a net negative magneto-strictive coefficient, has a positive value anisotropy field, a low collapse field and high figure of merit. The film is easily switchable utilizing z-y coincident drive lines and the composite can readily be formed into a chip comprising an array of switchable optically active pixels. Also disclosed are light valves, optical printers, microwave signal processors and magneto-optic light deflectors comprising the described magneto-optic light composites.

Abstract: A first apertured shutter rotates almost a full revolution in a first direction, and a second apertured rotary shutter rotates almost a full revolution in an opposite direction before the apertures of both blades are present at the optical axis to effect exposure, thereby to reduce dynamic disturbances owing to the reduced blade accelerations required.

Abstract: An acousto-optic device is shown which permits the use of a temperature sensitive solid state laser. The laser is mounted in a heat sink that displaces the laser as a function of temperature in a direction which cancels the drift of the laser's blur spot due to the laser's increased wavelength as a function of temperature.

Abstract: An array of electromechanical actuators are positioned beneath a movable mirror and have movable contacts which are affixed to the upper surface of a resistive mat having a single voltage gradient applied across the mat to control the tilting of the mirror. The adjustability of the contact points of each actuator enables the use of actuators which have a substantially varying sensitivity with respect to the application of particular voltages.

Abstract: Circuitry for converting interlaced video data to non-interlaced video data at 30 frames per second, real time video rate, where rows of successive lines of video data applied to a single frame memory are provided having data control means including readin and readout means for initially sequentially loading each row of memory with lines of interlaced video data of the first frame sequentially applied to the memory and thereafter reading out successive memory rows of the first frame from memory, while replacing each line readout by whatever line of the second frame is applied to memory in real time just after readout, until all lines of data of the second frame are inserted into memory.

Abstract: A technique for reproducing an image in a set of grey scale steps is disclosed including: providing a plurality of superpixels for providing an output representative of an image; providing a set of threshold levels for each pixel in a superpixel, which set is different from each of the sets of threshold levels of the other pixels in that superpixel and different from the set of greyscale steps; identifying the position of a given pixel in a superpixel and designating a particular set of threshold levels corresponding to the position of that given pixel; comparing the output of the given pixel with its particular set of threshold levels; and indicating the greyscale step in the set of greyscale steps in response to the output of the given pixel equal to or in excess of at least one of the threshold levels in the set of threshold levels corresponding to that pixel position.

Abstract: A sensitive wavefront sensor combining attributes of both a Hartmann type of wavefront sensor and an AC shearing interferometer type of wavefront sensor. An incident wavefront, the slope of which is to be detected, is focussed to first and second focal points at which first and second diffraction gratings are positioned to shear and modulate the wavefront, which then diverges therefrom. The diffraction patterns of the first and second gratings are positioned substantially orthogonal to each other to shear the wavefront in two directions to produce two dimensional wavefront slope data for the AC shearing interferometer portion of the wavefront sensor. First and second dividing optical systems are positioned in the two diverging wavefronts to divide the sheared wavefront into an array of subapertures and also to focus the wavefront in each subaperture to a focal point.

Abstract: A device for detecting the centroid of a beam of electromagnetic energy is shown including means for focusing the beam into a blur spot upon a focal plane. Photodetectors located at the focal plane detect the centroid of the blur spot on either side of its nominal location. The intensity of the output from each photodetector is then measured and the difference and sum of these measurements obtained. By dividing the difference by the sum of the resultant signals, it is possible to produce an analog signal which represents the location of the blur spot centroid regardless of its amplitude. This arrangement has particular application in acousto-optic devices for measuring the frequency and direction of arrival of an incoming radio frequency wave.

Abstract: A system is shown which receives several radio frequency (RF) signals and applies these signals to a Bragg cell through which a beam of coherent light is passed and diffracted into several first order beamlets. The diffraction angle of the beamlets is a function of the frequency of the RF signals. The beamlets are amplified in an amplifier having a fast response time to match the response time of the system. Fiber optic bundles are provided at the input and output of the amplifier to guide the beamlets from a linear pattern into an areal pattern and to spread the beamlets for a more efficient use of the amplifier. The amplified beamlets are then formed into a linear pattern and applied to a photodetector to determine the frequency of the RF signals.

Abstract: A drum is mounted to rotate about its drum axis. A pair of elongated, complementary guides are proximate to and extend along the axial length of the drum. The guides are sized and spaced to allow a workpiece to span the guides and roll upon them. A driver is mounted alongside the guides for rolling the workpiece on them. These guides are positioned between the drive means and the drum. The workpiece is positionable between the driver and the guides to protrude beyond the guides and reach the drum.

Abstract: A keyboard spacer for inhibiting the depression of selected push buttons upon a keyboard is shown including a longitudinal trunk having a first resilient arm which engages a key stem of a keyboard switch between the switch and the push button. As the first resilient arm yields, a second latching arm snaps over the key stem for retaining the spacer in the position desired. The spacer, which inhibits the depression of the push button, may be easily removed if push button operation is desired.

Abstract: A method for reducing the radial temperature gradient of a radiant energy emitting heated body is described. The method comprises insulating such heated body with a refractory insulating material containing an efficient absorber of the radiant energy emitted by said heated body. Specifically, materials containing trivalent dysprosium are disclosed as suitable thermal insulation for use where the heated body is at a temperature in the 1800.degree. C.-2500.degree. C. range. Also described is a crystal growth chamber for pulling unicrystalline compositions from a melt utilizing the Czochralski technique. The chamber is characterized by the placement of a refractory insulating material containing an efficient absorber of near infrared radiation around a crucible which contains the melt. Dysprosium is specifically disclosed as an efficient absorber of the near infrared radiation which is emitted by melt and crucible at the elevated temperatures employed for boule formation utilizing the Czochralski technique.

Abstract: An acousto-optic deflector is shown which diffracts a beam of incident light from a zero order beam into a first order beam. Normally such diffraction deflects but 1% of the light energy within the incident beam. This deflection may be improved by successive, internal transits of the light beam across the acoustic energy wave within the deflector. Such internal transits are accomplished by forming the deflector into a cylinder and reflection coating the outer surface of that cylinder to form a mirror pair.

Abstract: An acousto-optic deflector or modulator is shown which diffracts a beam of incident light from a zero order beam into a first order beam. Normally such diffraction deflects but 1% of the light energy within the incident beam. This deflection may be improved by successive transits of the light beam across the acoustic energy wave within the deflector.