US 5,117,071 AGranted

Stylus sensing system

AssigneeInternational Business Machines Corporation

InventorsEvon C. Greanias, Frank L. Stein, Robert Donaldson, Michael Gray

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Abstract

An improved finger touch and stylus detection system for use on the surface of a display device is disclosed. An overlay having horizontal and vertical transparent conductors is coupled to the other elements of the system through a bus having a minimum number of bus wires. A control processor issues command signals which selectively couples the transparent conductors to a capacitive measuring device and a radiative measuring device to determine finger and stylus position respectively. The improvements to the system include a radiative stylus having a spherical antenna which receives the overlay signal independent of the angle at which it is held. Further, a contact detecting mode has been added to eliminate spurious stylus positions measured between strokes, when the stylus is proximate to but not in contact with the overlay.

Claims16

Dependent claims

An improved finger touch and stylus detection system having a transparent overlay with a transparent array of horizontal and vertical conductors, the horizontal conductors being spaced from the vertical conductors by an insulating material, a control processor, a capacitive measurement means to detect finger input, a radiative source for stylus detection, a switchable path to couple selected conductors to the capacitive measurement means and the radiative source in response to appropriate commands from the control processor and a stylus wherein:

the control processor is connected to the capacitance measuring means to receive measured capacitance values of the conductors when the switchable path has connected a first pattern of conductors to the capacitance measurement means to detect the location of a finger touch with respect to the overlay;
the control processor is connected to a radiative source measurement means to receive measured radiative signal values of the conductors when the switchable path has connected a second pattern of conductors to the radiative source to detect the vertical and horizontal location of the stylus with respect to the overlay;
the control processor is connected to the radiative source measurement means when the switchable path has connected a third pattern of conductors to the radiative source to detect the height of the stylus with respect to the overlay;
and,
whereby, finger touch location, stylus horizontal and vertical location and stylus height with respect to the overlay can be determined.

2 more elements

An improved method for finger touch and stylus detection in a transparent overlay having a transparent array of horizontal and vertical conductors, the horizontal conductors being spaced from the vertical conductors by an insulating material, a control processor, a capacitive measurement means to detect finger input, a radiative source for stylus detection and a means for selecting and coupling conductors to the capacitive measurement means and the radiative source and a stylus to receive signals radiated by the overlay comprising the steps of:

determining whether a sense mode exclusion threshold has been exceeded by a radiative signal value received by the stylus;
locating a general position of the stylus with respect to the overlay, by selecting a horizontal and a vertical conductor pair from which the stylus receives the highest strength signals, if said sense mode has been exceeded;
determining whether the stylus is within a predetermined height above the overlay;
accurately tracking a precise position of the stylus, if the general position of the stylus has been located, and if the stylus is determined to be within the predetermined height above the overlay;
repeating the tracking step as long as the stylus is within the predetermined height above the overlay;
locating a general position of a finger touch, if said sense mode exclusion threshold has not been exceeded;
and,
locating a more precise position of the finger touch, if the general position of the finger touch as been located.

5 more elements

Dependencies are inferred from the claim text.

Facts

Application: 07/608,062Filed 31 Oct 1990
Granted: 26 May 1992
Term ends: Not estimatedThe source records don’t support an estimate.

Classification6 codes

G06F 3/03545
With detection of two-dimensional [2D] relative movements between the device, or an operating part thereof, and a plane or surface, e.g. 2D…
G06F 3/0441
By capacitive means: using active external devices, e.g. active pens, for receiving changes in electrical potential transmitted by the digitiser,…
G06F 3/046
Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means: by electromagnetic means
G06F 2203/04101
Indexing scheme relating to G06F3/041 - G06F3/045: 2.5D-digitiser, i.e. digitiser detecting the X/Y position of the input means, finger or stylus,…