Abstract: A bearing for allowing the movement of a movable mirror in a Michelson interferometer includes a stationary hollow glass cylinder and a movable assembly which includes the movable mirror and at least one graphite member, the graphite member being slidably disposed within the bore of the glass cylinder. Preferably, there is an anti-rotation system for the movable assembly which includes a post coupled with the movable assembly, a magnet mounted on one end of the post and a stationary guide rail positioned substantially parallel to the axis of rotation of the movable assembly and at a predetermined radial distance from the movable assembly.

Abstract: An interferometer that may be used in an infrared spectrometer has a housing with a fixed mirror, a perpendicular moving mirror, and a beamsplitter diagonally between them. A moving bearing is mounted to a stationary bearing for translation back and forth along a longitudinal axis, and the moving mirror is mounted to a support member which itself is mounted to the moving bearing to allow pivoting of the mirror support member about a pivot point. A permanent magnet is mounted to the support member and extends along the longitudinal axis, with one of the poles of the magnet formed at the free end of the magnet along the longitudinal axis. A main magnet coil mounted to the housing has an inner bore which extends around the free end of the permanent magnet such that current supplied to the main coil attracts or repels the magnet to drive the moving bearing and the moving mirror in translation back and forth along the longitudinal axis.

Abstract: A data acquisition system includes an analog to digital converter, a computer processor and a waveform memory in which is stored digital data from the A to D converter corresponding to an input signal. The processor provides a trigger responsive to a characteristic of a frequency component or components of the input signal to cause the memory to save the waveform data in the memory. The frequency characteristic may be determined, for example, by carrying out a synchronized recursive discrete Fourier transform which is updated for the selected frequency component or components with each new sample from the A to D converter.

Abstract: A probe for use in attentuated total reflectance measurements in spectroscopy, such as Fourier transform infrared spectroscopy, is formed of an optical waveguide element having input and output sections and a loop between the two sections. The loop has a small radius of curvature and is exposed so that it can be contacted with a sample to obtain attenuated total reflectance measurements. The input and output sections may be retained in the bore of a thin walled tube with the loop forming a tip which extends from one end of the tube. The input and output sections of the optical waveguide element may be connected by couplers to a spectrometer to receive the output beam from and provide a return beam to the spectrometer. The tightly curved surfaces of the optical waveguide element at the loop result in multiple internal reflections as the beam of radiation traverses the loop.

Abstract: A data acquisition system such as a digital oscilloscope includes a central processing unit which controls the waveform memory, analog to digital converter, trigger generator, and display to automatically adjust the acquisition parameters to optimal values for a particular repetitive waveform received by the data acquisition system. The system initially optimizes the acquisition parameters for determining the length of the input waveform and then determines the input waveform length. Parameters are then determined for best frequency analysis of the input waveform, and the waveform is then frequency analyzed to determine its spectral content.

Abstract: An analysis system accepts physiological sensor signals, including electroencephalogram (EEG) and other signals commonly sensed in sleep analysis, stores the raw data for later retrieval, extracts features from the digitized signal data which are of a type apt to be significant in classifying and detecting physiological functions (such as the state of sleep) and matches the extracted features to patterns which indicate the type of feature that has been extracted. The matched features are then utilized to classify for each epoch (limited period of time) the state of the physiological function (such as the stage of sleep) for that epoch. The results of the classification analysis are displayed on a CRT screen to the operator on a real time basis and in time correlation with representations of detected features from the various physiological signals.

Abstract: An infrared source for use in an infrared spectrometer includes an insulator core having a containment cavity, an outlet port in communication with the containment cavity, and an electrically heated infrared element mounted in the containment cavity with a portion thereof facing the outlet port and with the walls of the containment cavity closely spaced to the infrared element. The insulator core is formed of a ceramic fiber material which has excellent resistance to heat and very low thermal conductivity so that very little heat from the infrared element escapes from the insulator core except as infrared radiation through the outlet port. The insulator core is preferably mounted within a central cavity of a metal housing, and may be sealed off from the ambient atmosphere by an infrared transmissive window sealed to an outlet opening in the housing.

Abstract: Efficient cancellation of AC power line interference from a signal received by electronic instruments, such as biomedical monitors, is obtained by efficiently estimating the magnitude and phase of the noise signal from the contaminated input signal in a digital signal processor. Each interfering noise component of known frequency is represented as a sinusoid composed of cosine and sine components having estimated amplitude parameters. These amplitude parameters are recalculated at discrete points in time in the digital signal processor to carry out substantially a Fourier integration on the input signal at the known frequency f.sub.0 of the interfering signal, with the integration being updated to the last sample. The integration can be carried out to allow the estimates to adapt to time varying amplitudes and/or phases of the interfering signals. Cancellation of the estimated noise sinusoid from the input signal results in an output signal substantially uncontaminated by the noise.

Abstract: A mirror alignment and damping device (10) maintains orthogonality between the fixed mirror and the moving mirror in an interferometric spectrometer. The device (10) includes electromagnetic motion imparting units (32, 34, 36, and 38) which have electromagnetic coils (40) and threadedly adjustable pole pieces (44). The electromagnetic motion imparting units (32, 24, 26, and 38) are preferably arranged along perpendicular axes along a base (12) in order to enable independent orthogonal tilting of the mirror (26). Each voice coil consists of a wound wire coil (40) immersed in an annular magnetic field created by permanent magnets (42) which are mounted on a mirror support (44).

Abstract: Signals from plural electrodes placed at known positions on the head of an individual are digitized and processed in a computer processor which includes a bank of spatial filters. The filters are designed to meet a linearly constrained minimum variance criterion so that they each substantially pass signal energy from a location within the brain known with respect to the electrodes while rejecting signal energy from other locations within the brain. The outputs of the filters can be used to estimate the signal power at each of the locations in the brain, or the dipole moment at each location, and this information can be displayed on a display device to provide a map of source activity within the brain. The spatial filters do not require prior knowledge of the number of sources, and the number of discrete sources can be identified as well as the location, power, and dipole moment of the sources.

Abstract: A spectrometer for Raman spectrometry has a radiation source which provides a beam of radiation directed onto a sample, sample collection optics which directs the radiation from the sample as an input beam into an interferometer, the output beam of the interferometer being focused onto a detector, and filters interposed in the input and output beams of the interferometer. The filters are preferably holographic notch filters. Optical subtraction occurring in the interferometer as a result of the filters provides enhanced attenuation of the Rayleigh line of the reflected radiation while substantially passing the Raman lines, with the two filters achieving attenuation of the Rayleigh line equivalent to that obtained by several comparable filters stacked together.

Abstract: An interferometer mirror such as may be used in an FTIR spectrometer is mounted to a mirror alignment device which allows alignment of the mirror during operation of the interferometer. The alignment device includes a base, a mirror support to which the mirror is mounted, and means for mounting the mirror support to the base to allow resilient pivoting of the mirror about an initial position around two orthogonal axes when force is applied to the mirror support. Two drive coils of square configuration are mounted around the periphery of the mirror support. Each drive coil has lower coil sections along two opposite quadrants and higher coil sections, with the two drive coils being mounted to the mirror supports so that the lower sections of each are in adjacent quadrants. A magnetic field, such as that provided by permanent magnets, is applied to the lower sections of each coil while the upper sections of each coil are outside the magnetic field.

Abstract: An infrared detector assembly for infrared spectrometers includes a circuit board on which electronic components and an infrared detector and cooler unit are mounted. The detector unit includes a thermal electric cooler which cools the detector and transfers heat to a flange of the detector unit. A front side heat sink is mounted to the flange to dissipate heat to the air on the front side of the circuit board. Heat is also transferred from the flange of the heat detector unit by a heat conductive post or posts through openings in the circuit board to a heat sink mounted to the back side of the circuit board. The back side heat sink can include an adjustment plate to which the circuit board is detachably mounted and which is itself mounted on an assembly which allows lateral adjustment of the position of the circuit board and the detector thereon.

Abstract: An oscilloscope provides adjustable control of the reference voltage level to the trigger comparator to calibrate the trigger for both gain and offset. An internal computer in the oscilloscope provides a digital input value to a gain digital-to-analog converter (DAC) the analog output of which is provided to the reference input of a level DAC. The level DAC also receives digital input from the control computer and provides its analog output to the reference input of the trigger channel comparator. The digital data value provided to the gain DAC determines the relative gain of the output signal from the level DAC.

Abstract: A modular optical system for a Fourier transform infrared spectrometer which has a baseplate assembly with a baseplate having a top surface and two mirrors mounted to focus at a point above the baseplate. At least two pins extend upwardly from the baseplate top surface and are fixed with respect to the foci of the mirrors. An accessory module has a flat bottomed positioning plate with portions defining pin holes to coincide with the pins of the face plate. A sample holding accessory platform extends from the positioning plate and is fixed with respect to the pin holes so that when the pin holes of the positioning plate are positioned over the pins of the baseplate and the positioning plate bottom surface is engaged with the locator pads on the baseplate, the sample is located at the foci of the mirrors.

Abstract: A twin-arm interferometer spectrometer having a tiltable reflector assembly, which includes a pair of mutually facing parallel reflective elements, varies the path length of both interferometer arms simultaneously to achieve high resolution in a small, low maintenance design. Collimated electromagnetic radiation is split by a beamsplitter into first and second arm beams. Both arm beams impinge on the tiltable reflector assembly, to retroreflectors, and back to the beamsplitter wherein they recombine to form an exit beam. The exit beam is directed to a sample and then to a suitable detector. Modulation of the exit beam is produced by tilting the reflector assembly about an axis parallel to the reflective elements in the reflector assembly. This tilting causes a simultaneous variation in the path length of both interferometer arms, and thereby yields a large total path difference with a relatively small movement.

Abstract: The velocity of a moving mirror in a Fourier-transform infrared spectrometer is controlled by a circuit which utilizes a preset counter to generate pulses with a preset duration which are initiated at the zero-crossings of the signal from a detector of a laser light beam passed through the interferometer. This pulse signal is averaged and summed with a bias voltage and integrated and amplified to produce a drive current which is supplied to a drive coil which drives the moving mirror. When the mirror is moving too slowly, such that the preset duration pulses become a smaller fraction of the total time between zero crossings, the integrator provides an increased driving current and hence an increase in the speed of the mirror. If the mirror is moving too rapdily, the preset duration of the counter pulses will become a larger fraction of the time between zero crossings with a resultant reduction in the driving current and hence the velocity of the moving mirror.

Abstract: In order to correct for misregistration of solder pads in multilayer board (MLB) panels and determine drill target locations through vertical stacks of the solder pads, a fixture is prepared with fixture holes arranged in a pattern that corresponds with the locations of fiducial pads that are located on the MLB panel. The fixture has tooling pins that engage with tooling holes in the MLB panel to hold the MLB panel in an absolute position relative to the fixture. An x-ray inspection system views the superimposed image of a selected fixture hole and a corresponding fiducial pad that is visible within the boundary of the fixture hole. A software routine is then used to compute the offset between the fixture hole and the fiducial pad. The process is then repeated for the remaining sample of fixture holes and fiducial pads. The results are then fitted and then sent to a drilling machine to determine a position for the drilled holes in the MLB panel that compensates for the misregistration of the solder pads.

Abstract: An electromagnetic coil is wound on a circular mold and potted with a potting compound in order to eliminate the bobbin which is used with prior art electromagnetic coils. The potting technique can be advantageously applied to coils wound on any shape mold and to coils wound with wire of any cross-sectional shape. In the preferred embodiment the "bobbinless" coil is wound on a cylindrical mold and uses wire which has been partially flattened to improve the density of the coil. The flattened wire is preferably made by flattening ordinary wire copper to an aspect ratio of about 1.5. In an alternate embodiment, the bobbinless coil is wound with ordinary circular wire. In the preferred embodiment, the bobbinless coil forms part of a linear motor for use in driving the movable mirror in an interferometer spectrometer. In this application the coil provides a strong flux density and a strong force, yet occupies a relatively small volume.

Abstract: In a system for displaying multichannel EEG data, data values received from a matrix of EEG electrodes are stored in a random access memory. Digital values to be displayed are interpolated from the input values by addressing selected ones of the inputs from memory, multiplying those inputs by predetermined coefficients taken from a coefficient memory and summing the products. Each element of the display can be determined in that way within one frame time of the display apparatus. The data can be interpolated in real time for a flicker free display at a rate of over 25 frames per second. By displaying separate values associated with each display element as a distinct color, the dimensionality of the display can be increased. The numeric matrix which underlies the expanded topographic display can be stored digitally and further utilized in further operations and displays.