How Large Interactive Whiteboards Track Fingers Across Multiple Sensors
A method for stitching together data from multiple overlapping touch sensors so a single large surface acts as one seamless input area.
Original patent title: “Pointer tracking across multiple overlapping coordinate input sub-regions defining a generally contiguous input region”
A method for stitching together data from multiple overlapping touch sensors so a single large surface acts as one seamless input area. Granted to Smart Technologies ULC in 2008 with 62 claims and 84 forward citations.
Key facts
Coverage
What does this patent actually cover?
This patent describes a way to make very large touchscreens by tiling smaller sensor units together. Each sensor unit uses cameras to triangulate where a finger or pen is touching its specific area. When a finger moves into the overlap zone between two sensors, both units track the pointer simultaneously. The system then uses a weighted averaging formula to combine these two sets of data into one smooth, accurate coordinate, preventing the pointer from jumping or stuttering as it crosses the seam.
The gap
What does this patent NOT cover?
- Does not cover non-overlapping sensor arrays where the software simply switches control from one sensor to the next.
- Does not cover touchscreens that use capacitive or resistive grids instead of camera-based triangulation.
- Does not cover systems that lack a mathematical averaging or blending logic for the overlapping data.
These exclusions are unique to PatentBrief — derived from the actual claim language, not patent-office boilerplate.
What made this novel
Instead of choosing one sensor's data over the other at the boundary, the system treats the overlap as a transition zone where the influence of each sensor is weighted based on the pointer's position, ensuring a fluid, continuous movement.
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
SMART Board interactive whiteboards
Large-format digital signage with touch overlays
Multi-projector interactive wall systems
Why it matters
The bigger picture
Before this technology, building a touch-sensitive wall was difficult because the seams between sensors caused dead zones or erratic pointer behavior. This patent provided a mathematical framework for 'seamless' interaction, which became essential for the development of large-format interactive whiteboards used in classrooms and corporate boardrooms.
Filed
January 2, 2004
Granted
April 8, 2008
Market context
Who's building on this
Companies in this space
SMART Technologies, the original assigneeassigneeThe entity that owns the patent — usually the inventor's employer or a company.Read more →, remains a primary player in this space. Other manufacturers of large-format interactive displays, such as Promethean and various industrial display integrators, utilize similar multi-sensor tiling techniques to achieve large-scale touch functionality.
Market impact
This patent helped standardize the design of large-scale interactive displays by solving the technical challenge of 'seaming' multiple sensors. It enabled the transition from small, single-sensor tablets to massive, wall-sized interactive surfaces that behave as a single, unified input device.
Claim 1 — Plain English
What this patent covers
This patent describes a way to make very large touchscreens by tiling smaller sensor units together. Each sensor unit uses cameras to triangulate where a finger or pen is touching its specific area. When a finger moves into the overlap zone between two sensors, both units track the pointer simultaneously. The system then uses a weighted averaging formula to combine these two sets of data into one smooth, accurate coordinate, preventing the pointer from jumping or stuttering as it crosses the seam.
The clever bit
Instead of choosing one sensor's data over the other at the boundary, the system treats the overlap as a transition zone where the influence of each sensor is weighted based on the pointer's position, ensuring a fluid, continuous movement.
What it does not cover
- Does not cover non-overlapping sensor arrays where the software simply switches control from one sensor to the next.
- Does not cover touchscreens that use capacitive or resistive grids instead of camera-based triangulation.
- Does not cover systems that lack a mathematical averaging or blending logic for the overlapping data.
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
39/40
Highly cited
Claim breadth
20/20
Very broad protection
Recency
5/20
Granted 10–20 years ago
Assignee scale
0/20
Independent or smaller assigneeassigneeThe entity that owns the patent — usually the inventor's employer or a company.Read more →
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
$86K – $276K
Midpoint $173K · 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
62 claims as filed with the patent office.
Concepts involved
Citations
Patent lineage
Cite this patent
Holmgren, D. E., Hill, D. B., & Su, S. Y. T. (2008). How Large Interactive Whiteboards Track Fingers Across Multiple Sensors (U.S. Patent No. 7,355,593). U.S. Patent and Trademark Office. https://patentbrief.org/patent/us/7355593/xbox-360-controller
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 Large Interactive Whiteboards Track Fingers Across Multiple Sensors cover?
A method for stitching together data from multiple overlapping touch sensors so a single large surface acts as one seamless input area.
Who owns patent US 7355593?
Smart Technologies ULC owns this patent, granted in 2008.
When does this patent expire?
This patent is expected to expire on April 8, 2028, when the invention enters the public domain.
What is patent US 7355593 cited by?
This patent has been cited by 84 later patents that build on its ideas.
What problem does this patent solve?
Before this technology, building a touch-sensitive wall was difficult because the seams between sensors caused dead zones or erratic pointer behavior. This patent provided a mathematical framework for 'seamless' interaction, which became essential for the development of large-format interactive whiteboards used in classrooms and corporate boardrooms.
What does this patent NOT cover?
Does not cover non-overlapping sensor arrays where the software simply switches control from one sensor to the next.
Patent monitoring