Abstract: An improved system for magnetic position tracking of a device includes a magnetic transmitter, a magnetic sensor, a computing system and a polarity inverter. The magnetic transmitter includes at least one transmitter coil that outputs a transmitted magnetic field having a time derivative component. The magnetic sensor includes at least one sensor coil that has coil terminals having a polarity, and the sensor coil is responsive to the time derivative component of the transmitted magnetic field and outputs a sensor signal. The computing system computes position and angular orientation data of a device based on the sensor signal and the polarity inverter is configured to connect to the coil terminals and to cause the polarity of the coil terminals to be reversed according to a switching signal.

Abstract: An improved system for magnetic position tracking of a device includes a magnetic transmitter, a magnetic sensor, a computing system and a polarity inverter. The magnetic transmitter includes at least one transmitter coil that outputs a transmitted magnetic field having a time derivative component. The magnetic sensor includes at least one sensor coil that has coil terminals having a polarity, and the sensor coil is responsive to the time derivative component of the transmitted magnetic field and outputs a sensor signal. The computing system computes position and angular orientation data of a device based on the sensor signal and the polarity inverter is configured to connect to the coil terminals and to cause the polarity of the coil terminals to be reversed according to a switching signal.

Abstract: An electromagnetic needle tracking system includes a needle assembly, a calibration system and a computing system. The needle assembly includes a needle stylet and a sensor assembly. The sensor assembly includes a sensor that measures position and angular orientation data when placed within an electromagnetic field. The calibration system measures the sensor's position and angular orientation for a known needle tip position and angular orientation within a calibration fixture and calculates a position offset and an angular orientation offset of the sensor relative to the needle tip position and angular orientation. The computing system computes position and angular orientation data of the needle tip by adding the sensor position offset and angular orientation offset to the measured position and angular orientation data, respectively.

Abstract: A device for measuring the position (location and orientation) in the six degrees of freedom of a receiving antenna with respect to a transmitting antenna utilizing transmitter charge quantization. The transmitting component consists of a transmitting antenna of known location. The transmitting antenna is driven by a pulsed excitation. The receiving antenna measures the transmitted magnetic field. A computer then provides the correct position and orientation output.

Abstract: A transmitter consists of a plurality of magnetic transmitters, each of which is substantially planar and made of a spiral shaped conductor. The result is a transmitter having a substantially uniform cross-sectional current density along the radial direction of the spiral from the center to the periphery. Near the plane of a given spiral, magnetic vectors produced by such a conductor arrangement have improved angular characteristics as compared to prior art systems. This results in a larger region with useful vector crossing angles and operation of the system is enhanced as compared to prior art techniques. The transmitters produce magnetic fields which have a monotonically increasing intensity as one approaches the center of the transmitter spiral from any given direction. This feature simplifies and increases the accuracy of sensor position determination.

Abstract: A transmitter assembly includes a sandwich made up of a three axis transmitter, driven by a transmitter driver, mounted on a permeable attenuator with a spacer interposed between the transmitter and the attenuator. The attenuator is mounted on top of a conductive plate. A compensation coil is provided and driven by a compensation coil driver that energizes the compensation coil to optimize compensation for magnetic field edge effects. A number of individual compensation coils may be arranged about the periphery of the conductive plate or permeable attenuator. The individual compensation coils in the modification may be activated in tandem or individually to compensate for non-uniform magnetic edge fields caused by he non-symmetrical configuration of, for example, three transmitter coils or, for example, a square permeable attenuator rather than a circular permeable attenuator.

Abstract: A method of measuring position and orientation of an object in a space in six-degrees of freedom includes a three axis transmitter transmitting a magnetic field to be received by a three axis receiver. The transmitter transmits a pulsed DC transmit waveform. The waveform is preferably a symmetrical square wave with distinct non-overlapping axes and signal processing is accomplished such that the integrator is reset at the start of the rising edge transient period, the coil output signal is integrated throughout the rising edge transient and steady state periods, and the integration result is measured at the end of the steady state period, for each axis. The result is dramatically enhanced signal to noise ratio. The timing of measurements is chosen to reduce eddy current distortion while providing improved compensation for drift of the sensor with respect to the Earth's stationary magnetic field.

Abstract: A method of measuring position and orientation of an object in a space in six degrees of freedom includes a three axis transmitter transmitting a magnetic field to be received by a three axis receiver. The transmitter transmits a pulsed DC transmit waveform. The waveform is preferably a symmetrical square wave with distinct non-overlapping axes and signal processing is accomplished such that the integrator is reset at the start of the rising edge transient period, the coil output signal is integrated throughout the rising edge transient and steady state periods, and the integration result is measured at the end of the steady state period, for each axis. The result is dramatically enhanced signal to noise ratio. The timing of measurements is chosen to reduce eddy current distortion while providing improved compensation for drift of the sensor with respect to the Earth's stationary magnetic field.

Abstract: A transmitter consists of a plurality of magnetic transmitters, each of which is substantially planar and made of a spiral shaped conductor. The result is a transmitter having a substantially uniform cross-sectional current density along the radial direction of the spiral from the center to the periphery. Near the plane of a given spiral, magnetic vectors produced by such a conductor arrangement have improved angular characteristics as compared to prior art systems. This results in a larger region with useful vector crossing angles and operation of the system is enhanced as compared to prior art techniques. The transmitters produce magnetic fields which have a monotonically increasing intensity as one approaches the center of the transmitter spiral from any given direction. This feature simplifies and increases the accuracy of sensor position determination.

Abstract: A transmitter assembly includes a sandwich made up of a three axis transmitter, driven by a transmitter driver, mounted on a permeable attenuator with a spacer interposed between the transmitter and the attenuator. The attenuator is mounted on top of a conductive plate. About the periphery of the conductive plate or the permeable attenuator, a compensation coil is provided that is driven by a compensation coil driver. The compensation driver energizes the compensation coil in a way to optimize compensation for magnetic field edge effects. In a modification, a number of individual compensation coils may be arranged about the periphery of the conductive plate or permeable attenuator, with the configuration of the compensation coils being designed based upon the factors set forth above, namely, the number and configuration of the transmitter coils, the shape of the permeable attenuator, and the configuration of the conductive plate.

Abstract: A magnetic field position and orientation measurement system contains, confines and re-directs the magnetic field from one or more transmitters such that the fields are attenuated in areas outside of the operating volume in areas where metallic objects are commonly found. An attenuator made of a highly permeable material such as ferrite or mumetal may be placed on top of a conductive plate. The permeable attenuator may be as thin as 0.001 inches. on top of the permeable attenuator, a transmitter system is placed including at least three transmitters. In one embodiment, the transmitter consists of a PC board carrying the transmitter. The transmitter system, the permeable attenuator and the conductive plate, where used, may only be from ½ inch to ⅝ of an inch in thickness combined. The permeable attenuator may have a flat, planar configuration. Alternatively, it may be made to resemble, in cross-section, a cake pan having a flat central region with uplifted peripheral edges.

Abstract: A magnetic field position and orientation measurement system contains, confines and re-directs the magnetic field from one or more transmitters such that the fields are attenuated in areas outside of the operating volume in areas where metallic objects are commonly found. An attenuator made of a highly permeable material such as ferrite or mumetal may be placed on top of a conductive plate. The permeable attenuator may be as thin as 0.001 inches. On top of the permeable attenuator, a transmitter system is placed including at least three transmitters. In one embodiment, the transmitter consists of a PC board carrying the transmitter. The transmitter system, the permeable attenuator and the conductive plate, where used, may only be from 1/2 inch to 5/8 of an inch in thickness combined. The permeable attenuator may have a flat, planar configuration. Alternatively, it may be made to resemble, in cross-section, a cake pan having a flat central region with uplifted peripheral edges.

Abstract: A device is disclosed for measuring the position (location and orientation) in the six degrees of freedom of a receiving antenna with respect to a transmitting antenna utilizing multiple frequency AC magnetic signals. The transmitting component consists of two or more transmitting antenna of known location and orientation relative to one another. The transmitting antenna are driven simultaneously by an AC excitation, with each antenna occupying one or more unique positions in the frequency spectrum. The receiving antennas measure the transmitted AC magnetic field plus distortions caused by conductive metals. A computer then extracts the distortion component and removes it from the received signals providing the correct position and orientation output to a high degree of accuracy.