Abstract: A method and apparatus is disclosed for installing a data gathering system in a checkout counter such that it extends slightly above the surface of the counter. The data gathering system defines an entry side and an exit side. Products to be processed by the system are passed from the counter to the system over the entry side of the system, processed and then passed from the system to the counter over the exit side of the system. The counter adjacent the entry side of the system is elevated such that products processed by the system pass along a downwardly stepped path from the elevated portion of the counter down to the system and then from the system down to the counter on the other side of the system. Preferably, counter elevation is performed by a tapered trim strip which is secured across the counter adjacent the entry side of the data processing system.

Abstract: An improved liquid flow check valve using a ball and seat wherein the seat is made of sintered ceramic. The improved valve will operate in an environment of acetonitrile and water without sticking shut, thereby providing more stable liquid flow rates in liquid chromatography systems.

Abstract: The operating speed of a brushless DC motor is maintained at a desired speed by controlling the voltage level of power supplied to the motor. The motor includes a rotor carrying permanent magnets, cooperating electromagnets contained in a stationary armature and Hall effect devices for sensing the operating speed and position of the rotor. Circuitry connected to the Hall effect devices generates angular sector signals corresponding to activation periods or periods during which power is applied to the electromagnets to operate the motor. A processor connected to one of the Hall effect devices monitors the operating speed of the motor and generates an error signal representative of the difference between the operating speed of the motor and a desired reference speed. A power supply is controlled by the processor to generate power having a voltage level corresponding to the error signal.

Abstract: A Q-switch for a laser having a resonant cavity including an output coupler, a gain medium and a retro-reflecting mirror is mounted in the resonant cavity between the gain medium and the retro-reflecting mirror. The Q-switch comprises a polarizer and a phase retarding element (such as a Pockels cell) which includes a birefringent substrate for inducing a controllable phase retardation in the cavity mode in response to an applied electric field. A tiltable mount supports the phase retarding element so that the lasing axis lies essentially in a plane of the crystallographic axis 45.degree. from the direction of polarization, and lies at an adjustable angle relative to the crystallographic axis. A control circuit supplies an applied electric field within the substrate having a first magnitude in a first state and a second magnitude in a seocnd state. In the first state, the phase retarding element induces 90.degree. rotation in a round trip for the cavity mode.

Abstract: A laser beam three dimensional position measurement system includes a laser transmitter mounted at a stationary reference position at a work site and a receiver mounted on a mobile machine at the site. The transmitter produces a laser reference plane by sweeping a laser beam about the transmitter. The receiver includes two spaced apart laser beam detectors for measuring the horizontal angle of the incoming beam with respect to the face of the receiver at two spaced apart locations on the face of the receiver. The horizontal angles are used to determine the range of the receiver from the transmitter. The transmitter includes an azimuth device for providing signals to the receiver indicative of the azimuth angle at which the receiver is positioned with respect to a reference axis that extends from the transmitter. The receiver includes a decoder signal receiving device for receiving the angle signals from the transmitter in order to determine its azimuth angle.

Abstract: There is disclosed herein an apparatus and method for performing liquid chromatography analysis with a stable baseline. The apparatus utilizes positive displacement means on each of two flow paths and a control system to regulate the flow such that the flow in both flow paths is identical. Only one flow path has sample injected therein. Each flow path is passed through a separate liquid chromatography column and a common detector at the output end of each column. Since one flow path contains solvent only and the other flow path contains both solvent and sample, any changes in the characteristics of the output streams of the liquid chromatography columns caused by changes in the solvent composition itself have a common mode. Therefore, only the difference signal is output from the detector which indicates changes in the characteristics of the output stream of the sample flow path caused solely by the presence of the sample components.

Abstract: In an optical system having an optical element (such as a diffraction grating) mounted on a shaft which is to be affixed to the shaft of a driver such as a galvanometer, a collet assembly is used to couple the two shafts together so as to maintain the two shafts coaxially relative to each other.

Abstract: A DC control voltage being supplied to a pulse-width modulator in a switched resistor regulator control feedback loop is modified by addition of an AC offset voltage dither signal; the sum of the DC and AC voltages suffices to "turn on" the pulse-width modulator in some, but not all, of the periods of the output pulse train of the pulse-width modulator. The output pulse train controls the switch in a switched resistor regulator to turn on for a minimum period of time in some, but not all, of the periods of switching the resistor into and out of electrical connection. Thus the switched resistor regulator obtains an average duty cycle which is substantially less than the duty cycle which could be obtained with the minimum pulse width. In an alternate embodiment, a switched resistor regulator is controlled by a plurality of switches (e.g.

Abstract: Apparatus operable in accordance with the method of the present invention for measuring the angle of incidence of a light beam or plane relative to level comprises a photodetector array for sensing the light and a level mirror preferably comprising a pool of mercury. Optics are provided for transmitting the light to the photodetector array in alignment with the angle of incidence of the light (aligned light) and also after the light has been reflected from the mercury pool (reflected light). A shutter is provided for separating aligned light from reflected light such that distinct signals representative of the two are generated by the photodetector array. The distinct signals are processed by up-counting and down-counting a counter circuit to determine the average centers of light spots representative of the aligned light and the reflected light and the distance between those average centers which is representative of the deviation of the light beam or plane from level.

Abstract: There is disclosed herein an apparatus and method for performing liquid chromatography analysis with a stable baseline. The apparatus utilizes positive displacement means on each of two flow paths and a control system to regulate the flow such that the flow in both flow paths is identical. Only one flow path has sample injected therein. Each flow path is passed through a separate liquid chromatography column and a common detector at the output end of each column. Since flow path contains solvent only and the flow path contains both solvent and sample, any changes in the characteristics of the output streams of the liquid chromatography columns caused by changes in the solvent composition itself have a common mode. Therefore, only the difference signal is output from the detector which indicates changes in the characteristics of the output stream of the sample flow path caused solely by the presence of the sample components.

Abstract: A computer program for controlling an ink-jet printer-plotter having a conventional multi-jet ink-jet cartridge operates so that when the printer-plotter is in plot mode, the jets are used in sequence, instead of conventionally always using the same jet. A different jet is used each time a new graph is started. This method lengthens the life of the cartridge by reducing stress on any one of the jets.

Abstract: A system for detecting position of a light beam propagating along a beam path utilizes a single variable gain preamplifier in a time shared mode for each of the outputs of a four quadrant position sensors. A detector mounted in the beam path and having a reference point, generates a plurality of signals indicating deviation from the reference in plural directions. A multiplexer is connected to the detector, and combines the plural signals into a time multiplexed output. A variable gain preamplifier normalizes the signals in the time multiplexed output to generate the normalized output. The normalized output is then supplied to a logic circuit for processing the normalized output to generate a position signal indicating the position of the light beam.

Abstract: A tunable solid state laser having a titanium:sapphire grain medium and a birefringent filter mounted within a resonant cavity is provided. The resonant cavity is longitudinally pumped. The cavity is enclosed in a casing which has a small window admitting the pump beam into the resonant cavity, and a small window with an anti-reflection coating allowing the laser output to exit the casing. The casing is maintained at a positive pressure of nitrogen gas during operation of the laser to purge the resonant cavity of air and water vapor.

Abstract: A wire, comprising a shape memory alloy, is shaped to define a perimeter of an aperture having an adjustable size. The wire is responsive to current flow through the wire to vary the length of the wire, and thereby the length of the perimeter of the aperture. A controllable power supply is coupled to the wire, for supplying a controllable current through the wire to adjust its length, and thereby to adjust the size of the aperture. The aperture is suited for controlling transverse modes in a laser by controlling diffraction losses in the laser resonant cavity. Also, the shape memory alloy aperture is suitable for mounting within a sealed cavity laser.

Abstract: A device for detecting and displaying the relative position of a generally horizontal reference plane of light, even when partial shading of the device occurs, produces a linear response that is independent of spot size and energy distribution. The device includes a photodetector means having first and second interdigitated photodetector elements positioned adjacent each other on the device. The first and second interdigitated photodetector elements provide first and second detection signals, respectively. A circuit means, responsive to the photodetector means, determines the relative levels of the first and second detection signals such that the position of the reference plane of light with respect to the detector device is determined. A display means, responsive to the circuit means, provides an indication of the position of the reference plane of light with respect to the detector device.

Abstract: An ion laser is constructed with means for generating a magnetic confinement field operating in the cathode transition region of the laser. The magnetic confinement field is preferably generated by first and second magnetic windings, each axially aligned with the laser volume, but disposed so as to generate first and second magnetic fields which are of opposite polarity. The first and second magnetic fields of opposite polarity combine to create a region of zero axial magnetic field, which in a preferred embodiment is located substantially within the cathode transition region of the laser. In an alternate embodiment, the first and second magnetic fields are of the same polarity, and therefore generate a region of minimized axial magnetic field, preferably located substantially within the cathode transition region of the laser.

Abstract: An orthogonal light plane generator is associated with a primary light plane generator to convert a portion of a first light plane projected by the primary light plane generator into a second light plane substantially orthogonal to the first light plane. The orthogonal light plane generator comprises a diverter which defines three or more reflecting surfaces for receiving a portion of the first light plane and redirecting that portion as the second light plane. The three or more reflective surfaces are oriented relative to one another such that tilting of the orthogonal light plane generator is compensated to maintain the orthogonality between the two light planes. Tilting about one axis results in offset of the second light plane and tilting about a second axis orthogonal to the first results in a shifting of the sector within which the second light plane is projected, but tilting about either axis does not affect the orthogonality between the planes.

Abstract: A prism beam expander in which the incoming beam is essentially achromatically expanded by 100-500 times in one dimension with transmission through the prism beam expander exceeding 40%. In addition, the input beam is nearly collinear with the output beam. The prism beam expander includes 6 prisms in a preferred system, at least 2 of the apexes of which are oriented on the first side of the optical path while at least 2 of the apexes of the remaining prisms are oriented on the second side of the optical path. The achromatic, high-magnification collinear prism beam expander is used in a tunable laser achieving very narrow linewidths.