Computer graphics processing and selective visual display system – Display peripheral interface input device
Reexamination Certificate
1998-09-18
2001-04-24
Chow, Dennis-Doon (Department: 2775)
Computer graphics processing and selective visual display system
Display peripheral interface input device
C345S174000, C178S019010, C178S019030, C178S019070, C084S733000, C084S735000, C702S095000
Reexamination Certificate
active
06222522
ABSTRACT:
The present invention relates generally to man-machine interfaces and particularly to methods and systems for sensing the motion of a stylus, pointer, drum stick or baton over a surface.
BACKGROUND OF THE INVENTION
The present invention is a motion and position sensor that can be used as an electronic drum, much like an electronic keyboard is used with a musical synthesizer. The present invention can also be used for inputting one-dimensional, two-dimensional or three-dimensional data points into a computer or any other system.
The present invention uses a capacitive two-dimensional tablet as a position digitizer. Examples of other positional digitizers and capacitive two dimensional tablets are described in U.S. Pat. Nos. 4,705,919 (Dhawan), U.S. Pat. No. 3,999,012 (Dym), U.S. Pat. No. 4,087,625 (Dym et al.), and U.S. Pat. No. 4,659,874 (Landmeier). An earlier patent by the present inventor concerning a capacitive, two-dimensional tablet and position digitizer is U.S. Pat. No. 4,980,519 (Mathews), which is hereby incorporated by reference in its entirety as background information.
Objects of the present invention include providing improved uniformity in the accuracy over the X-Y-Z space in which a positioning member is moved, providing an antenna that allows for a position to be efficiently determined based on measured capacitances, and providing an antenna (i.e., capacitive tablet) that is readily fabricated on a two sided printed circuit board.
Another object of the present invention is to accurately detect the X, Y position of one or more batons or styluses, without regard to the strength of the signal emitted by the batons or styluses.
SUMMARY OF THE INVENTION
In summary, the present invention is a radio signal actuated electronic position sensor which operates in conjunction with one or more batons. Each baton has a transmitter that transmits a distinct radio frequency signal at a position in space. The position sensor determines the current position of each baton transmitter in terms of X, Y, and Z coordinates.
To determine the position of each baton transmitter, the position sensor includes a tablet having a flat support member at a predefined position, with at least two pairs of electrodes coupled to the flat support member. Each of the electrodes is a separate antenna. A first pair of the electrodes is shaped so that the amount of capacitive coupling between each baton transmitter and the first pair of electrodes corresponds to the position of the baton transmitter with respect to the X axis. A second pair of the electrodes is shaped so that the amount of capacitive coupling between each baton transmitter and the second pair of electrodes corresponds to the position of the baton transmitter with respect to the Y axis.
In one pair of antenna electrodes, each of the electrodes is comprised of a plurality of wedge shaped regions. The width of each of the regions of one electrode decreases linearly in the X direction and the width of each region of the second electrode increases linearly in the X direction. The width of each of the regions of an electrode in this pair is the same for any given Y position. Thus as a positioning member moves across the surface of the sensor in the Y direction, the width of each of the regions of an electrode in this pair is the same. At X positions other than the X-dimension midpoint of the sensor, the width of the second electrode regions is different from the width of the first electrode regions.
The second pair of antenna electrodes are comprised of narrow rectangular electrode regions. The widths of these electrode regions are constant in the X direction. The widths of the electrode regions of a first antenna in the pair increase linearly with increasing Y, and the widths of electrode regions of the second antenna in the pair decrease linearly with increasing Y. In a preferred embodiment, the regions forming the first pair of antenna electrodes are interleaved with the regions forming the second pair of antenna electrodes.
Capacitance is a linear function of the area of an electrode. The ratio of the areas of the antenna electrodes of the first pair of electrodes depends linearly on the X position of a baton transmitter, and is independent of the Y position. The ratio of the local areas of the second pair of antenna electrodes depends linearly on the Y position of the baton transmitter, and is independent of the X position. Thus by measuring the capacitance values between the baton and the four antennae, the X, Y position of the baton can be computed with uniform accuracy anywhere in the X-Y plane.
The position sensor also has a CPU which receives signals from the electrodes, and uses those signals to compute the X, Y and Z coordinates of each baton. The Z position of the baton transmitter is inversely proportional to the total capacitive coupling between the baton and either pair of electrodes.
REFERENCES:
patent: 4087625 (1978-05-01), Dym et al.
patent: 4659874 (1987-04-01), LAndmeier
patent: 4831566 (1989-05-01), Matthews et al.
patent: 4980519 (1990-12-01), Mathews
Mathews Max V.
Oberheim Thomas E.
Awad Amr
Chow Dennis-Doon
Interval Research Corporation
Pennie & Edmonds LLP
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