Geometrical instruments – Indicator of direction of force traversing natural media – Magnetic field responsive
Reexamination Certificate
1999-11-30
2001-09-11
Bennett, G. Bradley (Department: 2859)
Geometrical instruments
Indicator of direction of force traversing natural media
Magnetic field responsive
C033S0010PT
Reexamination Certificate
active
06286220
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to a device for determining directional information relative to an external magnetic field. More particularly, this invention pertains to a light-reflective device for determining directional information relative to an external magnetic field.
There are no known light-reflective devices available that can be used to determine directional information relative to an external magnetic field. While there are some existing patents relating to light-transmission devices operable for determining directional information relative to an external magnetic field, none of these patents address the problems solved by the present invention. In addition, none of these patents discloses the concept of using a light-reflective device to determine directional information.
U.S. Pat. No. 4,414,754, issued to Lapeyre on Nov. 15, 1983 and entitled “High Resolution Compass Card Position Decoder,” discloses a light-transmission device for determining directional information relative to an external magnetic field. The '754 device includes a disk having a light-transmission pattern, a light source on one side of the disk, and an array of light detectors on the other side of the disk. The '754 device does not disclose the use of a disk having a light-reflective pattern.
Another patent, U.S. Pat. No. 5,448,835, issued to Lewis on Sep. 12, 1995 and entitled “Compass device,” discloses a light transmission device for determining directional information relative to an external magnetic field. The '835 device includes a light source, a variable-width, slotted compass card for transmitting light, a magnet, and two light detecting devices. The '835 device also does not disclose the use of light-reflective disk. The size of the magnet used in the '835 device is limited by the light-transmission compass card. Smaller magnets limit the torque available to rotate the compass card, reduce the response time of the device, and adversely affect the balance of the device. The '835 device is also sensitive to the intensity of light striking the compass card. Variations in the intensity of light passing through the compass card may generate errors in the directional information.
What is needed, then, is a device that is insensitive to variations in the intensity of light striking the compass card and includes a larger, more balanced magnet.
SUMMARY OF THE INVENTION
The present invention accomplishes these and other objectives with a light-reflective device for determining positional information relative to an external magnetic field including a housing, reflective compass assembly, light generating and detecting assembly, a processor, and a display.
One object of the present invention is to provide a light-reflective device that is insensitive to the intensity of light striking a compass card.
Another object is to provide a light-reflective device including a balanced disk magnet.
Still another object is to provide a light-reflective device including a magnet having a length equal to the diameter of a compass card.
Another object is to provide a light-reflective device including a reflective pattern representative of directional information relative to an external magnetic field.
A further object of the present invention is to provide a light-reflective device including a contact image sensor module as the light generating and detecting assembly.
Still another object is to provide a compass card having a reflective pattern including a non-reflective spiral line and a non-reflective circle.
Yet another object is to provide such a reflective pattern having a non-reflective spiral line, a first non-reflective circle, and a second non-reflective circle.
The above and other objects, features, and advantages of the present invention should become even more readily apparent to those skilled in the art upon a reading of the following detailed description in conjunction with the drawings wherein there is shown and described illustrated embodiments of the invention.
REFERENCES:
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patent: 4027398 (1977-06-01), Fowler et al.
patent: 4341023 (1982-07-01), Marcus et al.
patent: 4414754 (1983-11-01), Lapeyre
patent: 4640016 (1987-02-01), Tanner et al.
patent: 4922620 (1990-05-01), Terragni
patent: 5042157 (1991-08-01), Garrett et al.
patent: 5301434 (1994-04-01), Imaizumi
patent: 5448835 (1995-09-01), Lewis
patent: 5469630 (1995-11-01), Lewis
patent: 5749150 (1998-05-01), McDermott
patent: 5752322 (1998-05-01), Lewis
patent: 6145209 (2000-11-01), Chang
patent: 6212783 (2001-04-01), Ott et al.
Harrison Robert
Patel Manu C.
Bennett G. Bradley
Directional Robotics, Inc.
Garvin, Jr. John C.
Hilton Harold W.
Waddey & Patterson PC
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