Graphic tablet and method
First Claim
1. A method for determining the position of an instrument on a surface having a plurality of grid conductors oriented in X and Y directions, all X conductors interconnected by resistors, said plurality of X conductors having a pair of terminals, a first X terminal connected to a first X conductor and a second X terminal connected to a last X conductor, all Y conductors interconnected by resistors, said plurality of Y conductors having a pair of terminals, a first Y terminal connected to a first Y conductor and a second Y terminal connected to a last Y conductor, said method comprising the steps:
- a. generating an electrical signal;
b. transmitting said signal from said instrument into said surface to cause respective signals to appear at each of said terminals;
c. forming a ratio of signal levels detected at the X conductor terminals;
d. generating a digital signal proportional to said ratio to thereby indicate the X position of said instrument;
e. forming a ratio of signal levels at the Y conductor terminals; and
f. generating a digital signal proportional to said ratio to thereby indicate the Y position of said instrument.
4 Assignments
0 Petitions
Accused Products
Abstract
A writing tablet is disclosed incorporating a plurality of conductors imbedded beneath the surface thereof in orthogonal relationship with respect to each other. The conductors form a grid for receiving radiated electric signals generated remote from the tablet and supplied to a pen acting as a radiating antenna. The radiated signals generate signals of varying amplitude in the respective grid conductors; the grid conductors in each of the X and Y directions are interconnected by resistors; terminals are provided at the outside conductors in the X and Y directions. The terminals are sequentially connected to a detector which in turn provides input signals to a dual slope integrator for ratioing the amplitude of the signal appearing at selected terminals. The output of the integrator is a timed wave form having a time value proportional to the position of the pen on the tablet surface.
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Citations
12 Claims
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1. A method for determining the position of an instrument on a surface having a plurality of grid conductors oriented in X and Y directions, all X conductors interconnected by resistors, said plurality of X conductors having a pair of terminals, a first X terminal connected to a first X conductor and a second X terminal connected to a last X conductor, all Y conductors interconnected by resistors, said plurality of Y conductors having a pair of terminals, a first Y terminal connected to a first Y conductor and a second Y terminal connected to a last Y conductor, said method comprising the steps:
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a. generating an electrical signal; b. transmitting said signal from said instrument into said surface to cause respective signals to appear at each of said terminals; c. forming a ratio of signal levels detected at the X conductor terminals; d. generating a digital signal proportional to said ratio to thereby indicate the X position of said instrument; e. forming a ratio of signal levels at the Y conductor terminals; and f. generating a digital signal proportional to said ratio to thereby indicate the Y position of said instrument. - View Dependent Claims (2, 3)
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4. Apparatus for determining the position of an instrument on a surface comprising:
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a. a plurality of grid conductors oriented in X and Y directions, all X conductors interconnected by resistors, said plurality of X conductors having a pair of terminals, a first X terminal connected to a first X conductor and a second X terminal connected to a last X conductor, all Y conductors interconnected by resistors, said plurality of Y conductors having a pair of terminals, a first Y terminal connected to a first Y conductor and a second terminal connected to a last Y conductor; b. a signal generator for generating an electrical signal; c. an instrument connected to said signal generator for transmitting said electrical signal through said surface into said grid to cause signals to appear at each of said terminals; d. a detector for sequential connection to each of said terminals; e. switch means for sequentially connecting said detector to said terminals; f. means for ratioing the level of the signals at the X terminals and for ratioing the level of the signals at the Y terminals; g. means responsive to the ratio of signal levels at the X terminals for generating a digital signal proportional to the instrument position in the X direction; h. means responsive to the ratio of signal levels at the Y terminals for generating a digital signal proportional to the instrument position in the Y direction. - View Dependent Claims (5, 6, 7, 8)
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9. A pen, for use in a graphic tablet system having a tablet with grid conductors therein to receive electric signals transmitted from the pen, comprising:
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a. a housing having a cylindrical bore therein; b. an ink cartridge mounted in said bore, for limited axial movement therein, having a point extending out of said housing for contacting a writing surface; c. an insulating sleeve mounted in said bore between said housing and said cartridge; d. a plunger mounted in said bore for limited axial movement therein and positioned for continuous contact with an end of said cartridge remote from said point; e. a stationary electrical contact within said bore positioned to be contacted by said plunger; f. spring biasing means urging said plunger into contact with said cartridge to urge the cartridge point to extend out of said housing and to simultaneously urge said plunger to contact said stationary electrical contact; g. a first conductor connected to said plunger and a second conductor connected to said stationary contact; whereby an AC electrical signal on said first conductor may be continuously transmitted through said plunger, cartridge, and to said point for radiation to said tablet when the contact between said plunger and stationary electrical contact is open or closed, and whereby a DC signal on said first conductor may be transmitted to said second conductor only when said plunger and stationary electrical contact are in contact, said DC circuit being opened by breaking said contact by urging said point toward said housing by contacting a writing surface. - View Dependent Claims (10)
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11. A pen system for use in a graphic tablet system having a tablet with grid conductors therein to receive AC electrical signals transmitted from the pen, said system including:
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a. a pen for radiating an electrical signal provided thereto; b. means for generating an AC electrical signal to be radiated to said graphic tablet; c. means for generating a DC signal d. a pen driver connected to said signal generating means having a tuned circuit for increasing the amplitude of the AC signal to be applied to the pen for radiation to the tablet surface; e. a pair of normally closed contacts mounted within said pen; f. a first conductor connecting said AC and said DC signals to one of said contacts; g. a pen cartridge mounted within said pen and connected to said one of said contacts for continuously transmitting said AC signal to said tablet; h. a second conductor connected to the other of said contacts for receiving said DC signal from said first conductor only when said contacts are closed. - View Dependent Claims (12)
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Specification