Abstract: A method and apparatus for identifying tissue structures in advance of a mechanical medical instrument during a medical procedure. A mechanical tissue penetrating medical instrument (22) has a distal end for penetrating tissue in a penetrating direction. An optical wavefront analysis system (32-50) provides light to illuminate tissue ahead of the medical instrument and receives light returned by tissue ahead of the medical instrument. An optical fiber (30) is coupled at a proximal end to the wavefront analysis system and attached at a distal end to the medical instrument proximate the distal end of the medical instrument. The distal end of the fiber has an illumination pattern directed substantially in the penetrating direction for illuminating the tissue ahead of the medical instrument and receiving light returned therefrom. The wavefront analysis system provides information about the distance from the distal end of the medical instrument to tissue features ahead of the medical instrument.

Abstract: A single-axis illumination system for a multiple-axis imaging system, particularly an array microscope. A single-axis illumination system is used to trans-illuminate an object viewed with an array of imaging elements having multiple respective axes. The numerical apertures of the imaging elements are preferably matched to the numerical aperture of the illumination system. For Kohler illumination, the light source is placed effectively at the front focal plane of the illumination system. For critical illumination, the light source is effectively imaged onto the object plane of the imaging system. For dark field illumination, an annular light source is effectively provided. For phase contrast microscopy, an annular phase mask is placed effectively at the back focal plane of the objective lens of the imaging system and a corresponding annular amplitude mask is provided effectively at the light source.

Abstract: In the process of converting an interferogram phase map to a surface profile, in the absence of tilt, a histogram of occurrences of phase values is created from phase data. Useful data are identified in bins with contents that exceed a threshold value. Where useful data wrap around the end of the histogram, a selected amount of phase shift is added to the phase data to move them all within the ends of the histogram. Where tilt is present, the phase data are differentiated to produce slope data and a histogram of occurrences of slope values is created. A best-fit amount of tilt is determined from the slope histogram by selecting the bin at the average between two points on the histogram curve that are a predetermined percentage of the maximum height of the curve. Thereafter, the best-fit tilt is subtracted from the original phase data to eliminate tilt.

Abstract: A method and apparatus for producing a temperature stable frequency at reduced cost. Advantage is taken of an existing, relatively temperature insensitive, low frequency and low cost watch crystal and an existing, high frequency, low cost, but relatively temperature sensitive system clock. A calibration module coupled to the watch crystal and clock calibrates the watch crystal to a reference frequency at a reference temperature and calibrates the clock to the watch crystal at an operating temperature, to relate the clock frequency to the reference frequency at any operating temperature and thereby provide a high precision, relatively temperature insensitive time or frequency base at low cost.

Abstract: An integrated digital processing device and method for examining the operation thereof. An integrated multiple digital processing device has externally-accessible tag connections which provide signals representative of what circuit has access to external memory used by the processing device. The processing device includes a plurality of digital processor circuits, a DRAM refresh logic circuit, externally-accessible connections for receiving memory access signals from an external processor, and an arbitration circuit for determining which of the digital processor circuits, refresh logic circuit or external processor may have access to the external memory. The signals on the tag connections are provided by the arbitration circuit, and indicate which of the aforementioned circuits has access to the external memory at any moment.

Abstract: A method and apparatus for producing self-diagnostic information from a circuit board. A circuit board is provided with an on-board processor, an on-board ROM containing diagnostic test software, a frequency generator adapted to produce an electrical signal having a predetermined frequency when an unacceptable response is determined, wherein the predetermined frequency corresponds substantially to the event within the diagnostic test sequence of a particular test for which an unacceptable response is determined. The signal is presented at an output terminal of the circuit board. The status of the circuit board is determined by measuring the frequency of the signal at the output terminal and comparing that frequency to an index of corresponding defects.

Abstract: A visually graded display of digitally compressed waveforms for a digital storage oscilloscope. A histogram is formed by sampling or otherwise resolving a data set of values corresponding to an independent variable to produce a quantized set of values over a selected compression interval of the independent variable. The compression interval represents equal quanta of the independent variable and has associated therewith a set of histogram bins, each containing a number, wherein the number contained within each bin represents a weighted number of hits associated with vectors connecting selected pairs of such dependent variable values, wherein each vector is associated uniquely with one pair. The numbers are weighted for each vector according to drawing techniques, the drawing techniques alone or in combination allowing choices for signal display ranging between retaining maximal signal information, for emulating the display of an analog oscilloscope, or retaining less signal information.

Abstract: A high speed analog signal sampling system. The system comprises a timing chain having a plurality of delay elements arranged in series and a sample rate multiplier having a delay lock control system responsive to the outputs of first, second and third parallel delay elements in the sample rate multiplier to control the delay of the second parallel delay element so that its strobe signal output occurs one-half the time between the strobe signal outputs of the first parallel delay element and the third parallel delay element. The first, second and third parallel delay elements are the first three parallel delay elements of the timing chain, and a control signal of the delay lock control system is used to adjust and control the amount of delay introduced by every other parallel delay element after the second parallel delay element.

Abstract: A medical knot tying instrument having a first member including proximal and distal ends, a gripping mechanism for releasably gripping a first length of suture proximate the distal end of the first member and a holding mechanism for releasably holding a second length of suture proximate the location where the gripping mechanism grips the first length of suture but separated therefrom a predetermined distance toward the first member's proximal end. Gripping one length of suture using the gripping mechanism and holding a second length of suture using the holding mechanism, the instrument is rotated in one angular direction so that the second length of suture forms a loop around the instrument whereupon the second length is grasped using a separate grasping instrument.

Abstract: A transistor amplifier having a main amplifier exhibiting a substantially doubled f.sub.T characteristic and having error cancellation circuitry, wherein the standing current of the error cancellation circuitry is reused in powering the main amplifier. The main amplifier comprises an outer differential pair of transistors and an inner differential pair of transistors, each differential pair having an inverting side and a non-inverting side. The collectors of the transistors of the non-inverting side of the differential pairs are connected, respectively, at a first current summing node. The collectors of the transistors of the inverting side of the differential pairs are connected, respectively, at a second current summing node. The f.sub.

Abstract: An optical time domain reflectometry method and apparatus that employs Hadamard transforms to increase the signal-to-noise ratio. A sequence of N pulses of light corresponding to a Hadamard derived code are launched down a fiber optic cable for each of N such codes. Selected combinations of pulses of reflected light are transformed by a Hadamard derived matrix to a set of equations that are solved simultaneously to determine the power reflected from each of N points. Where a Hadamard code is used the average mean square error is reduced by a factor of 1/N. Where a simplex code is employed the average mean square error is reduced by a factor of 4N/(1+N).sup.2. In addition, N measurements of the power reflected at each point are computed and averaged.

Abstract: A digital data generation system including a programmable dominance RS flip-flop has a random access memory that stores a user selected sequence of test data. A pattern formatting logic circuit receives the test data and produces, for each data period, a coarsely timed candidate pulse for identifying the leading edge of an output data pulse and a coarsely timed candidate pulse for identifying the trailing edge of the output data pulse. A precision delay circuit finely tunes the timing of the candidate pulses. The finely tuned pulses are applied to an RS flip-flop circuit which can be programmed for set or reset dominance, thereby preventing an indeterminate state when a logic "1" is applied to both the set and the reset input. In the system, the flip-flop is programmed so that the most recent of the lead pulse or the trail pulse prevails.

Abstract: Easily removable and donnable pants. The pants employ a releasable seam along the outside of each leg and a plurality of separate hook and loop fastener segments distributed along the seam for closing the seam. The lowest fastener, at the bottom of the pant leg, offers less resistance than those above it. The highest fastener, at the waist of the pants, offers more resistance than those below it. The lowest and highest fasteners comprise tabs, to permit adjustment of the waist and ankles of the pants to the size of the wearer, while those in between preferably are wave shaped. Preferably, the waist and ankle are provided with elastic material to make those portions of the pants adjustable and snug.

Abstract: A device and method for protecting the end of a wooden utility pole set in the ground. A split cylindrical casing is provided which can be placed around the lower end of a wooden utility pole just before it is installed in the ground. The casing comprises an elongate, relatively thin cylindrical member having one closed end and being split into two sections connected together along the side thereof. The connection acts as a hinge. The edges of the casing where it is split are provided with a fastener, one part of the fastener being disposed along the edge of one part of the casing and another part of the fastener being disposed along the edge of the other part of the casing. When the cylindrical casing is closed, the edge of one part overlaps the edge of the other part so that the respective parts of the fasteners fit matingly together. Preferably, the fastener extends the entire length of the casing and entirely across the bottom end thereof. Preferably, the casing is made of high grade plastic.

Abstract: A method and circuit for triggering an electronic instrument only once during a period of an input signal having multiple triggering events during that period. A signal applied to an electronic instrument, such as an oscilloscope, is acquired. Qualified triggering events occurring on the acquired signal are identified. A selected one of the qualified triggering events during the period of the applied signal causes a trigger signal output to occur, while other qualified triggering events are ignored. In the preferred embodiment a triggering event is qualified by a first comparator that compares the input signal to a first reference level and produces a predetermined logic level output if the input signal bears a predetermined relationship to the reference level. When a qualified triggering event occurs, a buffer amplifier applies the predetermined logic level to charge a capacitor, which thereafter stores some energy from the input signal and applies it to a comparator for a predetermined period of time.

Abstract: A dual-ranked time-interval conversion circuit. Two time trap circuits are employed to convert the time interval between a logic level transition of a first signal and a logic level transition of a second signal to an analog or digital signal representative of that time interval. Each time trap circuit employs a delay line for receiving and propagating the first signal and a series of taps and respective storage elements along the delay line for detecting and storing the logic level of the delay line at each tap at the time of receipt of a second signal. A first time trap circuit is employed to measure the time interval in course quanta of time and a second time trap circuit is employed to measure in fine quanta of time the time difference between the actual first signal-to-second signal time interval and the coarse measurement of that interval.

Abstract: A pedal board for musical instruments. Pedal mounting, guide, and electrical switch mechanisms are provided in a pedal board for an electronic organ. Each pedal is mounted by a cylindrical pin attached to the back end of the pedal and to the base of the pedal board by an interference fit. A similar, guide pin is attached to the front end of the pedal by an interference fit. The guide pin fits loosely in an aperture which limits lateral movement of the pin and, thence, of the pedal itself. The lower end of the guide pin actuates an elastomeric electric switch when the pedal is pressed down. The elastomeric electric switch is mounted on a printed circuit board, and includes a chamber having a bell-shaped wall attached to a support strip by weakened edges and enclosed at the bottom by a diaphragm carrying a conductive element. The conductive element shorts contacts on the printed circuit board when the chamber is compressed by the guide pin. Pedal board tension and resiliency is provided by the mounting pin.

Abstract: A magnetometer and method for measuring magnetic field strength particularly adapted for use in an electronic flux gate compass. A core of magnetic material in the shape of a toroid is coupled to a drive coil and to two sense coils oriented along orthogonal axes. A current limited, current source coupled to the drive coil periodically saturates the core, drives the core out of saturation at an intermediate current level, and saturates the core again. Each sense coil is coupled to a sense circuit which measures the current in the sense coil induced by the periodically changing flux density in the coil resulting from an external magnetic field coupled to the sense coil, produces a dc feedback signal to cancel out the external magnetic field, and provides the dc signal as an output representative of the external magnetic field strength along the axis of the sense coil. The dc signal is produced by synchronously detecting the amplified ac current in the sense coil.

Abstract: A hybrid form digital filter. A digital filter is provided wherein the zeros of its transfer function are provided by a direct form digital filter portion and the poles of the transfer function are provided by a normal form digital filter portion. The hybrid filter provides truncation noise and stability characteristics like those of a normal form digital filter, but its filter coefficients may be calculated more rapidly than those for a normal form digital filter having the same transfer function, thereby enabling the coefficients to be calculated in real time for tuning the filter. While the preferred embodiment is a second order hybrid digital filter, the same principles are applicable to higher order digital filters as well.