Sourceless orientation sensor

• US 5,526,022 A
• Filed: 01/06/1993
• Issued: 06/11/1996
• Est. Priority Date: 01/06/1993
• Status: Expired due to Fees

• Current Assignee: Bankruptcy Estate O Ono-Sendai Corporation, Interactive Imaging Systems, Inc.
• Original Assignee: Virtual RS Corp.
• Inventors: Donahue, Michael J., Drumm, Donald E., Pesce, Mark D., de Groot, Marc, Perry, Michael A.
• Primary Examiner(s): Weldon, Ulysses
• Application Number:
  US08/000,992
• Time in Patent Office: 1,252 Days
• Field of Search: 345/156-162, 358/87, 200/61.52, 340/440, 324/253
• US Class Current: 345/156
• CPC Class Codes: G01C 2009/066 optical
• CPC Class Codes: G01C 9/20 the indication being based on the inclination of the surface of a liquid relative to its container
• CPC Class Codes: G06F 3/011 Arrangements for interaction with the human body, e.g. for user immersion in virtual reality blind teaching G09B21/00
• CPC Class Codes: G06F 3/0312 for tracking the rotation of a spherical or circular member, e.g. optical rotary encoders used in mice or trackballs using a tracking ball or in mouse scroll wheels tracking relative movement in co-operation with a regularly or irregularly patterned surface, e.g. as in optical mice G06F3/0317; constructional details of scroll or thumb-wheels G06F3/0362; optical rotary encoders G01D5/3473
• CPC Class Codes: G06F 3/0346 with detection of the device orientation or free movement in a 3D space, e.g. 3D mice, 6-DOF [six degrees of freedom] pointers using gyroscopes, accelerometers or tilt-sensors

Abstract

A sourceless orientation sensor having an azimuthal sensor which determines the azimuthal orientation relative to a planetary magnetic field, and a tilt sensor which determines the direction and magnitude of the displacement from vertical using the planetary gravitational field. The tilt sensor includes a transparent gas and a transparent viscous fluid in a spherical shell, a light emitting diode (LED) mounted at the top of the shell, and four photodetectors mounted at the bottom of the shell. As the tilt sensor is rotated the path of the light cone emanating from the LED and refracting at the gas/fluid interface is altered, thereby altering the intensity of light incident on the photodetectors. The magnitude of the light incident on the photodetectors is processed to provide the tilt angles. A thin transparent disk floats at the gas/fluid interface to damp surface waves caused by reorientation of the device. A time sequence of orientations of the sensor may be interpreted to provided a gesture sensing device.

Claims

1. An orientation sensor comprising:

a frame defining a frame axis;

Velcro strap means for attaching said frame to the head of a user, said strap means having a foam insert

tilt sensing means, maintained in a fixed orientation with respect to said frame, for measuring the orientation of said frame with respect to the Earth'"'"'s gravitational field and providing a tilt signal that is related to the angle of tilt of the sensor to detect rotation of said frame axis from vertical;

magnetic sensing means, attached to a printed circuit board maintained in a fixed orientation with respect to said frame, for measuring the orientation of said frame with respect to the Earth'"'"'s magnetic field and providing an azimuth signal related to the azimuthal angle of the magnetic sensing means to detect rotation of said frame about said frame axis by comparing the orientation of the magnetic sensing means to the local magnetic field generated by the Earth using the phase and relative strength of signals output from said magnetic sensing means and using a difference obtained from said comparing to determine an azimuthal angle wherein said magnetic sensing means includes an array of three flux gate magnetometers aligned along mutually perpendicular axes and electronics means for driving the magnetometers including a copper excitation coil surrounding said magnetometer and for detecting signals from the magnetometers, each said magnetometer including a saturable ferrous metal, torroid-shaped core having a diameter of about one inch, which saturates at a frequency of about 2 kHz with a peak-to-peak voltage of about 8 volts, said electronic means configured to drive each said saturable core to neat its magnetic saturation at a frequency such that said local magnetic field causes flux to leak from each said core and wherein said electronics means for detecting signals includes first and second coils at right angles to one another and at right angles to the plane of the torroid, configured to detect each said flux leak at a frequency twice said first frequency wherein as said magnetic sensing means is rotated signals from said first and second coils change;

said printed circuit board containing analog circuitry means for operating said tilt sensing means and said magnetic sensing means, an analog-to-digital converter means for transforming said tilt signals and said azimuth signals to digital form signals and digital circuitry for communication over a first wireless transmitter communications means to an interface means for translating said digital form signals into control signals which can be interpreted by a computer;

said interface means including a programmed microcontroller for receiving said digital form signals to provide a standard RS-232 output to said computer and configured to simulate the operation of a standard cursor control mouse device;

power circuit means for providing steady DC voltages of +5 volts, about +4 volts and about -4 volts, said power circuit means including circuit breakers;

timing circuit means for producing a first timing signal at 2 kHz and a second timing signal at 4 kHz, offset from said first timing signal by 1/4 wavelength, said second timing signal being provided to said detecting means;

drive circuit means for receiving said first clock signal and producing a voltage of 8 volts to drive said magnetic sensor;

said detecting means comprising first and second identical high gain selective frequency detectors

a high-gain uplifter means with a notch filter having a gain of about 400, for selecting a first limited frequency band;

a 4 kHz chopper means, receiving an output from said high-gain amplifier means, for excluding extraneous signals so that only the local magnetic field is detected;

an integrator means, receiving an output from said chopper means, for reducing the number of signal fluctuations and providing feedback to said high-gain amplifier means and an output signal with substantially linear proportionality to an external field

a sensory means having left and right liquid crystal display means for displaying different images to provide a stereoscopic visual system, mounted in goggles attached to the user'"'"'s head providing visual display to the user and earphone means providing stereo audio to the user, wherein said visual display and audio alter to emulate orientation of the user'"'"'s head in a virtual reality environment and means for controlling the speed and direction of scrolling of said display in response to the direction of the sensor.