How Stylus Ring Electrodes Detect Pen Tilt and Orientation
Apple's patent for a stylus design that uses specific ring-shaped sensors to accurately measure the angle and tilt of a pen against a touchscreen.
Original patent title: “Active stylus ring electrode”
Apple's patent for a stylus design that uses specific ring-shaped sensors to accurately measure the angle and tilt of a pen against a touchscreen. Granted to Apple Inc in 2018 with 29 claims and 3 forward citations.
Key facts
Coverage
What does this patent actually cover?
This patent describes a specialized electrode configuration for an active stylus, consisting of a ring electrode, a ground ring, and a ground plate arranged on a non-conductive base. By precisely tuning the physical dimensions and spacing of these conductive elements, the stylus can shape its electric field to improve capacitive coupling with a touch-sensitive surface. This allows the device to calculate the orientation and tilt of the stylus relative to the screen. For example, when a user tilts their stylus to shade a digital drawing, the varying signal strength across these ring segments informs the tablet about the exact angle of the pen.
The gap
What does this patent NOT cover?
- Does not cover styluses that rely solely on a single tip electrode for touch detection.
- Does not cover touchscreens that use optical or infrared sensors to track pen position.
- Does not cover passive styluses that lack internal drive circuitry and active electrodes.
- Does not cover methods of tilt detection that use internal accelerometers or gyroscopes.
These exclusions are unique to PatentBrief — derived from the actual claim language, not patent-office boilerplate.
What made this novel
The invention uses a specific geometric arrangement of 'crown-shaped' projections and sub-rings with varying lengths to intentionally distort the electric field, allowing the stylus to 'see' its own tilt angle through capacitive feedback.
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
Apple Pencil (various generations)
iPad Pro digital art workflows
Professional digital illustration software
Why it matters
The bigger picture
As digital art and note-taking on tablets have become mainstream, the demand for high-fidelity input has grown. This technology allows professional-grade styluses to mimic the behavior of real pencils and brushes, which change their stroke width and texture based on the angle at which they are held. It is a core component in the evolution of the Apple Pencil ecosystem.
Filed
September 8, 2015
Granted
July 17, 2018
Market context
Who's building on this
Companies in this space
Apple remains the primary entity building on this specific electrode architecture for their proprietary stylus line. Other major manufacturers of active pens, such as Wacom and Microsoft, utilize their own distinct capacitive sensing methods to achieve similar tilt-detection results.
Market impact
This patent helped solidify the technical requirements for 'pro-level' stylus performance in the tablet market. By enabling precise tilt sensing, it helped bridge the gap between traditional analog media and digital input, making tablets viable tools for professional illustrators and designers.
Claim 1 — Plain English
What this patent covers
This patent describes a specialized electrode configuration for an active stylus, consisting of a ring electrode, a ground ring, and a ground plate arranged on a non-conductive base. By precisely tuning the physical dimensions and spacing of these conductive elements, the stylus can shape its electric field to improve capacitive coupling with a touch-sensitive surface. This allows the device to calculate the orientation and tilt of the stylus relative to the screen. For example, when a user tilts their stylus to shade a digital drawing, the varying signal strength across these ring segments informs the tablet about the exact angle of the pen.
The clever bit
The invention uses a specific geometric arrangement of 'crown-shaped' projections and sub-rings with varying lengths to intentionally distort the electric field, allowing the stylus to 'see' its own tilt angle through capacitive feedback.
What it does not cover
- Does not cover styluses that rely solely on a single tip electrode for touch detection.
- Does not cover touchscreens that use optical or infrared sensors to track pen position.
- Does not cover passive styluses that lack internal drive circuitry and active electrodes.
- Does not cover methods of tilt detection that use internal accelerometers or gyroscopes.
Patent timeline
Application submitted to the patent office
Application published, typically 18 months after filing
Patent officially issued
PatentBrief Score
Impact Score
Strong
Citation count
12/40
Early citations
Claim breadth
19/20
Very broad protection
Recency
10/20
Granted 5–10 years ago
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
$78K – $250K
Midpoint $156K · 9.2 yr remaining · 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
29 claims as filed with the patent office.
Concepts involved
Citations
Patent lineage
Cite this patent
MAHALATI, R. N., Armendariz, K. C., Tan, L., MARSHALL, B. R., Bhandari, P., Zimmerman, A. N., & Brooks, R. P. (2018). How Stylus Ring Electrodes Detect Pen Tilt and Orientation (U.S. Patent No. 10,025,401). U.S. Patent and Trademark Office. https://patentbrief.org/patent/us/10025401/apple-watch-digital-crown
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 Stylus Ring Electrodes Detect Pen Tilt and Orientation cover?
Apple's patent for a stylus design that uses specific ring-shaped sensors to accurately measure the angle and tilt of a pen against a touchscreen.
Who owns patent US 10025401?
Apple Inc owns this patent, granted in 2018.
When does this patent expire?
This patent is expected to expire on July 17, 2038, when the invention enters the public domain.
What is patent US 10025401 cited by?
This patent has been cited by 3 later patents that build on its ideas.
What problem does this patent solve?
As digital art and note-taking on tablets have become mainstream, the demand for high-fidelity input has grown. This technology allows professional-grade styluses to mimic the behavior of real pencils and brushes, which change their stroke width and texture based on the angle at which they are held. It is a core component in the evolution of the Apple Pencil ecosystem.
What does this patent NOT cover?
Does not cover styluses that rely solely on a single tip electrode for touch detection.
Same assignee
More from Apple Inc
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