Abstract: An apparatus for establishing a desired position of a tool, including a means for moving the tool along a particular axis, a laser for providing a beam of coherent light along an axis which intersects the axes of tool movement and which is located so that the tool can block at least a portion of the beam, a detector of beam blockage, and a controller for tool movement which can respond to signals from the detector.

Abstract: A detection device is disclosed for determining particle size from particle effected light scattering in a sensing region receiving the particles in a gas carrier, such as air, and a laser beam to illuminate the sensing region. Background light from molecular scattering is reduced to a level that enables light scattered by particles having a size of at least as low as about 0.1 micron to be sensed in a high background of molecular scattering such as, for example, where molecular scattering can exceed the 0.1 micron particle's scattering by one hundred times. High molecular scattering is generated whenever the gas volume being viewed is large as is required for high flow rates, high molecular density (high pressures), or large gas molecules.

Abstract: A method and apparatus are provided wherein a moving light source is passed over a surface whose shape is to be determined, in two orthogonal paths and is fixed at a plurality of positions along each path such that the light source illuminates the surface at a different slope for each position. A binary image camera photographs the surface for each of the fixed positions and the point at which each of a plurality of points on the surface is first illuminated and last illuminated, as well as the points that last shadowed or last failed to shadow any given point, are recorded. Constraint equations develop the effect a given point has on its last and failing shadowers and the effect each last and failing shadower has on the given point. Upper and lower bounds of these points are iteratively re-calculated according to the constraint equations until none of the points exhibit any more change in their upper and lower bounds.

Abstract: The duration of a very short semiconductor laser pulse, such as that ranging from a fraction to hundreds to picoseconds, can be measured utilizing the internally generated second harmonic emission of the laser. A laser diode is driven so that light emitted therefrom can pass through a beam splitter and be reflected by the beam-splitter into a photomultiplier and into a detector, respectively. Signals received therefrom relate to the conversion efficiency of the second harmonic emission generated by the picosecond pulses and of either continuous wave emission or pulse emission whose durations can be accurately measured by photodetectors. Apparatus includes a photodiode for measuring the fundamental laser power, a photomultiplier for measuring the second harmonic power, and appropriate filters. Ammeters coupled to the photodiode and photomultiplier measure the appropriate current. The ratio of the current can be determined by a ratio circuit or a computer.

Abstract: A device for characterizing the formation of a sheet material is described. The device comprises a basis weight sensor for measuring the basis weight of the sheet material as the material moves through the sensor and signal processing circuitry which receives a signal from the basis weight sensor indicative of the measured basis weight. The basis weight sensor includes a light source for directing a beam of light at the moving sheet and a light detector which detects the beam after it passes through the sheet. This detector produces a signal indicative of the intensity of the detected beam and transmits the signal to the signal processing circuitry. To calibrate the signal processing circuitry, a rotatable opaque wheel having a plurality of slots is positioned in the path of the light beam. The rotating wheel alternately blocks the light beam and allows the beam to pass through the slots to the detector.

Abstract: FM laser spectroscopy apparatus includes a single modulator for modulating a laser beam with first and second modulation signals (.omega..sub.1, .omega..sub.2). The two modulation signals are generated by mixing a signal from a first oscillator (.omega..sub.1 +.omega..sub.2)/2 and a signal from a second oscillator (.omega..sub.1 -.omega..sub.2)/2 and producing the two modulation signals (.omega..sub.1, .omega..sub.2). The modulator produces three groups of sidebands on the laser beam at the laser frequency plus and minus the two modulation frequencies and at plus and minus the difference between the two modulation signal frequencies. The apparatus provides practical high frequency FM spectroscopy as required for the observation of pressure broadened spectral features.

Abstract: An electrooptical system in which workpieces are illuminated from a generally uniform source of light and are line scanned for light intensity deviations characteristic of defects. Pulse trains from photoelectric detectors of a line array have pulse magnitudes which are a function of the light on discrete areas of the workpiece. Pulses having magnitude deviations from adaptively established signal levels are considered events characteristic of the defects. At the beginning of each scan the initial signals are rejected and the pulse train video signal is validated only after the video signal passed by a low pass filter exceeds a threshold. Thereafter data for the event signals of the scan are stored. In order to facilitate storage and processing of data, those event signals which occur for contiguous pulses are identified as event strings, and when an event string achieves greater than a threshold number of events, the stored data is compressed.

Abstract: The measurement of weak absorption lines is facilitated by the use of a long transmission path length, which is difficult to obtain in compact or portable instruments. In the present invention, light is made to travel through a limited volume of gas thousands of times. The light is placed on a closed optical path on which it circulates through the gas sample. After a desired number of passes through the gas sample, the light is removed from the closed optical path. Introduction of the light to the closed optical path and removal therefrom is accomplished through the use of a polarizing beamsplitter and a pockels cell located on the closed path. Light is put onto the closed path by the polarizing beamsplitter which imparts a specific polarization. During the first circuit the pockels cell alters the polarization by 90 degrees thereby preventing the light from escaping back out through the polarizing beamsplitter.

Abstract: A simple inexpensive gloss measurement device which makes use of the measment of a maximum angle of view of a clear reflection to obtain a measurement of gloss, consists of an instrument of L-shaped configuration with one or more small images (e.g., hollow squares) on the lower portion of the shorter arm and a graduated scale along edges of the longer arm. The device is placed on a coated surface to be measured, with the images close to the surface of the coating. The highest angle of view at which reflection of the images on the coating can be clearly recognized is noted on the graduated scale as a measure of the gloss of the coating.