How a Multi-Touch Screen Detects Multiple Fingers and Palms
This patent describes the underlying electronic circuits and methods for a multi-touch surface that can track multiple fingers and palms simultaneously, even before they fully touch the screen.
Original patent title: “Method and apparatus for integrating manual input”
This patent describes the underlying electronic circuits and methods for a multi-touch surface that can track multiple fingers and palms simultaneously, even before they fully touch the screen. Granted to University of Delaware in 2001 with 140 claims and 2,641 forward citations.
Key facts
Coverage
What does this patent actually cover?
This patent details how a multi-touch surface detects multiple finger and palm contacts. It uses an array of individual sensing devices (ClaimclaimA numbered sentence at the end of a patent that legally defines what the inventor owns. The most important section.Read more → 7), each sensitive to changes in its own electrical field (self-capacitance) as a hand or finger gets close (Claim 1). Each sensing device includes two electrical switches, a sensing electrode, a power supply, and circuitry to measure the electrical changes (Claim 1). Control circuitry sequentially activates each sensor, converting the electrical signals into digital data that represents the position and shape of multiple touches (Claim 7). For example, this system could track both a user's thumb and index finger as they pinch or zoom on a screen, even recognizing the difference between a fingertip and a palm.
The gap
What does this patent NOT cover?
- Does not cover touchscreens that only detect a single point of contact at a time.
- Does not cover resistive touchscreens, which work by two conductive layers pressing together.
- Does not cover optical touch systems that use cameras or light beams to detect touch.
- Does not cover touch devices that rely solely on surface acoustic wave (SAW) technology.
- Does not cover systems that lack the specific sensing device architecture described in ClaimclaimA numbered sentence at the end of a patent that legally defines what the inventor owns. The most important section.Read more → 1, including the series-connected switching means and integrating capacitor.
These exclusions are unique to PatentBrief — derived from the actual claim language, not patent-office boilerplate.
What made this novel
The clever bit is placing a small, dedicated sensing circuit (transduction circuit) directly under each individual electrode in a large array (ClaimclaimA numbered sentence at the end of a patent that legally defines what the inventor owns. The most important section.Read more → 1, AbstractabstractA short summary at the front of the patent describing the invention. Not legally binding.Read more →). This distributed approach maximizes the signal quality and reduces the complex wiring that would otherwise be needed for large multi-touch surfaces, making it practical to build such devices economically.
Schematic visualization of the patent's claim structure. Hand-drawn diagrams in progress for each landmark patent.
Where you've seen this
Real-world examples
Early multi-touch trackpads (e.g., FingerWorks iGesture Pad)
Modern smartphone touchscreens
Tablet touchscreens
Multi-touch laptop trackpads
Interactive public displays
Why it matters
The bigger picture
This patent is foundational for modern multi-touch technology, which became a standard feature in smartphones and tablets. It describes the core sensing technology that allows devices to understand complex gestures involving multiple fingers, transforming how people interact with computers. The University of Delaware, through its spin-off FingerWorks, demonstrated early multi-touch devices before Apple acquired the company and its technology.
Filed
January 25, 1999
Granted
November 27, 2001
Market context
Who's building on this
Companies in this space
Apple extensively built upon this technology after acquiring FingerWorks, integrating multi-touch into the iPhone, iPad, and Mac trackpads. Other major smartphone and tablet manufacturers like Samsung, Google, and Microsoft also develop and utilize multi-touch interfaces, though their specific implementations may differ from the precise claimsclaimsThe numbered statements at the end of a patent that legally define what the inventor owns.Read more → of this patent.
Market impact
This patent, and the technology it describes, laid crucial groundwork for the widespread adoption of multi-touch interfaces. It enabled the development of intuitive gesture-based interactions that defined the smartphone era, making devices like the iPhone possible. This fundamentally shifted the user experience for personal computing and created a massive market for multi-touch enabled devices.
Claim 1 — Plain English
What this patent covers
This patent details how a multi-touch surface detects multiple finger and palm contacts. It uses an array of individual sensing devices (Claim 7), each sensitive to changes in its own electrical field (self-capacitance) as a hand or finger gets close (Claim 1). Each sensing device includes two electrical switches, a sensing electrode, a power supply, and circuitry to measure the electrical changes (Claim 1). Control circuitry sequentially activates each sensor, converting the electrical signals into digital data that represents the position and shape of multiple touches (Claim 7). For example, this system could track both a user's thumb and index finger as they pinch or zoom on a screen, even recognizing the difference between a fingertip and a palm.
The clever bit
The clever bit is placing a small, dedicated sensing circuit (transduction circuit) directly under each individual electrode in a large array (Claim 1, Abstract). This distributed approach maximizes the signal quality and reduces the complex wiring that would otherwise be needed for large multi-touch surfaces, making it practical to build such devices economically.
What it does not cover
- Does not cover touchscreens that only detect a single point of contact at a time.
- Does not cover resistive touchscreens, which work by two conductive layers pressing together.
- Does not cover optical touch systems that use cameras or light beams to detect touch.
- Does not cover touch devices that rely solely on surface acoustic wave (SAW) technology.
- Does not cover systems that lack the specific sensing device architecture described in Claim 1, including the series-connected switching means and integrating capacitor.
Patent timeline
Application submitted to the patent office
Application published, typically 18 months after filing
Patent officially issued
PatentBrief Score
Impact Score
High impact
Citation count
40/40
Highly cited
Claim breadth
20/20
Very broad protection
Recency
0/20
Older than 20 years
Assignee scale
20/20
Major company or institution
PatentBrief Impact Score — based on citation count, claim breadth, recency, and assignee scale. Not a legal assessment.
Heuristic Value Estimate
What this patent might be worth
$144K – $461K
Midpoint $288K · expired or expiring · industry ×1.6
Heuristic only — blends forward/backward citation counts, claim scope, time remaining, litigation history, and CPC-derived industry baseline. Real valuations need a professional appraisal.
The original legal language
Original claims
140 claims as filed with the patent office.
Concepts involved
Citations
Patent lineage
Cite this patent
Westerman, W., & Elias, J. G. (2001). How a Multi-Touch Screen Detects Multiple Fingers and Palms (U.S. Patent No. 6,323,846). U.S. Patent and Trademark Office. https://patentbrief.org/patent/us/6323846/aqua-user-interface
Auto-generated from the patent record. Double-check author order and the issue date against the official USPTO document before submitting.
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Common Questions
Frequently Asked Questions
What does How a Multi-Touch Screen Detects Multiple Fingers and Palms cover?
This patent describes the underlying electronic circuits and methods for a multi-touch surface that can track multiple fingers and palms simultaneously, even before they fully touch the screen.
Who owns patent US 6323846?
University of Delaware owns this patent, granted in 2001.
When does this patent expire?
This patent has expired and is now in the public domain — anyone can use the invention freely.
What is patent US 6323846 cited by?
This patent has been cited by 2641 later patents that build on its ideas.
What problem does this patent solve?
This patent is foundational for modern multi-touch technology, which became a standard feature in smartphones and tablets. It describes the core sensing technology that allows devices to understand complex gestures involving multiple fingers, transforming how people interact with computers. The University of Delaware, through its spin-off FingerWorks, demonstrated early multi-touch devices before Apple acquired the company and its technology.
What does this patent NOT cover?
Does not cover touchscreens that only detect a single point of contact at a time.
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