Computer graphics processing and selective visual display system – Display peripheral interface input device – Stylus
Reexamination Certificate
1998-01-20
2001-02-06
Mengistu, Amare (Department: 2778)
Computer graphics processing and selective visual display system
Display peripheral interface input device
Stylus
C345S173000, C345S177000, C178S019070, C178S018040, C178S019020
Reexamination Certificate
active
06184873
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to the field of electronic input systems. More particularly, the invention relates to a system for determining the position of an electronic pointing device.
BACKGROUND OF THE INVENTION
Digitizing pen and tablet systems are used for a variety of electronic applications. These systems typically include a tablet, a position indicating pen, and associated electronics for determining the interaction between the tablet and the position indicating pen. A digital data signal is typically derived to represent the relative position of the position indicating pen and the tablet.
The calculated location of current prior art pens, in relation to an electronic tablet, have a systematic user error of approximately ±10 pixels. This error is determined solely by the angle at which the pen is inclined towards the tablet, and the distance from the tip of the pen to the center of a transmitting element.
M. Phillips, T. Philbin, and B. Blesser,
Coordinate Determining Device Using Spatial Filters,
U.S. Pat. No. 4,963,703 (Oct. 16, 1990) disclose a digitizing tablet, in which “two sets of circuitous conductive lines form grids each connected at one end to a surrounding conductive loop. All outputs are measured from the conductive loop as a multiplexor sequentially grounds the grids one at a time. The outputs are fed through linear spatial filters which are used to produce intermediate signals which are in turn combined to arrive at raw position signals for a position indicating coil located over the work surface. Separate sets of linear spatial filters may be used to produce two raw position signals differently responsive to tilt which can then be combined to arrive at a true position insensitive to tilt”. Phillips et al. also disclose a stylus having a single conductive coil, which is used as a position indicating implement over a work surface.
The disclosed prior art systems and methodologies thus provide basic pen and tablet positioning systems for determining the spatial relationship between a pen and a tablet, but fail to provide an accurate means for determining the position of the tip of the pen, independent of the angular displacement of the pen in relation to the tablet. J. Romein,
Acoustic Writing Combination Comprising a Stylus With An Associated Writing Tablet,
U.S. Pat. No. 4,246,439 (Jan. 20, 1981) discloses an acoustic writing stylus provided with two ultrasonic sound sources that are situated at different distances from a stylus tip and that are operated to alternately produce ultrasonic signals, thereby providing a scheme for more accurately determining the position of the stylus tip. However, because this system requires that alternate ultrasonic bursts at the same frequency produced by each of the ultrasonic sound sources be received to measure the respective distances of each of the sound sources from a receiver (microphone) there is a likelihood that angular movement of the stylus between bursts can alter the measured distance and produce an inaccurate determination of stylus tip position. The development of a more accurate, improved pen positioning system would constitute a major technological advance.
SUMMARY OF THE INVENTION
An improved pen positioning system is provided, in which a pen, having multiple output elements, is adapted to determine the location of the pointing tip of the pen accurately, in relation to an electronic tablet. The output elements, preferably ultrasonic transmitters having distinct frequencies, are located a fixed distance from each other, and are also related in space to the pointing tip of the pen. The geometric relationship between the output elements and the pointing tip of the pen allows the location of the pointing tip to be determined, independent of the angle which the pen is inclined against the surface of the writing tablet. A detection system is used to receive the output signals from the output elements, isolate the output signals from each other, and process them independently to determine the location of the output elements and of the pointing tip of the pen.
Alternative embodiments include an additional output element on a pressure sensitive shell of the pen, which allows the pen to accurately provide pressure sensitive output signal information.
REFERENCES:
patent: 4246439 (1981-01-01), Romein
patent: 4506354 (1985-03-01), Hansen
patent: 4577057 (1986-03-01), Blesser
patent: 4902858 (1990-02-01), Yamanami et al.
patent: 4963703 (1990-10-01), Phillips et al.
patent: 5500492 (1996-03-01), Kobayashi et al.
patent: 5557301 (1996-09-01), D'Aviau De Piolant
patent: 5717168 (1998-02-01), DeBuisser et al.
patent: 772149A1 (1997-05-01), None
patent: WO94/11844 (1994-05-01), None
Harel Jacob
Holtzman Rafi
Ward Daniel R.
Wood Robert P.
Electronics For Imaging, Inc.
Glenn Michael A.
Mengistu Amare
Nguyen Jimmy H.
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