# How Devices Detect Touch Using Heat Signatures > This patent describes a system that uses a thermal camera to detect when two objects, like a finger and a screen, touch by looking for a specific temperature change at their contact point. - **Patent:** US 20210117042 - **Original title:** Method and Device for Detecting a Touch Between a First Object and a Second Object - **Owner:** Apple - **Status:** Active - **Times cited:** 1 - **Field:** consumer_electronics, software, telecommunications, augmented_reality, human_computer_interaction ## What it does The patent describes a system that uses a thermal camera to detect when a "first object" (like a finger) touches a "second object" (like a display). The system first takes a thermal image of both objects and determines their individual temperatures. A touch is detected when the system finds pixels in the thermal image that show a "third temperature" exactly where the two objects meet (Claim 31). This "third temperature" is different from the individual object temperatures, indicating contact. For example, if a warm hand touches a cooler display, the system would identify a distinct warm spot on the display in the thermal image. The system then uses this detected touch and its position on the display to provide user input, such as interacting with an application (Claim 31). ## What it does NOT cover - Does not cover touch detection methods that do not rely on thermal imaging. - Does not cover systems that detect touch without identifying a distinct "third temperature" at the contact point (Claim 31). - Does not cover touch detection where the two objects have the same temperature, as the method relies on a temperature difference. - Does not cover touchscreens that use electrical capacitance, pressure sensors, or optical sensors to detect contact. - Does not cover systems that only detect the presence of an object without specifically identifying a touch based on a temperature change. ## The clever bit The novelty lies in using thermal imaging to specifically identify a touch event by detecting a distinct "third temperature" at the precise point of contact between two objects that have different initial temperatures. This goes beyond just seeing heat; it's about identifying the interaction through a localized temperature anomaly. ## Real-world examples 1. Future augmented reality (AR) displays 2. Interactive surfaces in industrial or medical settings 3. Devices requiring touch input while wearing gloves 4. Advanced human-computer interfaces for specialized tasks ## Why it matters This technology could enable new ways for users to interact with devices, especially in environments where traditional touchscreens might be difficult to use, like with gloves or through certain materials. It could also provide more precise or nuanced input by detecting the specific area of contact and even aspects like which part of a user's hand is touching, as suggested by Claim 40. ## Frequently asked questions ### What does How Devices Detect Touch Using Heat Signatures cover? This patent describes a system that uses a thermal camera to detect when two objects, like a finger and a screen, touch by looking for a specific temperature change at their contact point. ### Who owns patent US 20210117042? This patent is owned by Apple. ### When does this patent expire? This patent is expected to expire on December 23, 2040, when the invention enters the public domain. ### What is patent US 20210117042 cited by? This patent has been cited by 1 later patents that build on its ideas. ### What problem does this patent solve? This technology could enable new ways for users to interact with devices, especially in environments where traditional touchscreens might be difficult to use, like with gloves or through certain materials. It could also provide more precise or nuanced input by detecting the specific area of contact and even aspects like which part of a user's hand is touching, as suggested by Claim 40. ### What does this patent NOT cover? Does not cover touch detection methods that do not rely on thermal imaging. **Full plain-English explainer:** https://patentbrief.org/patent/us/20210117042/method-and-device-for-detecting-a-touch-between-a-first-object-and-a-second-obje **Original patent:** https://patents.google.com/patent/US20210117042 --- _Source: PatentBrief — https://patentbrief.org. Patent facts are from public records; the plain-English explanation is PatentBrief's._ ## Related patents Semantically similar inventions in the PatentBrief corpus: - [Using Different Light Colors to Detect Touches on Screens](https://patentbrief.org/patent/us/20110234542/methods-and-systems-utilizing-multiple-wavelengths-for-position-detection) — This 2011 patent describes a system that uses two different colors of light to accurately detect where an object, like a finger, touches a screen or surface. - [How a Multi-Touch Screen Detects Multiple Fingers and Palms](https://patentbrief.org/patent/us/6323846/aqua-user-interface) — 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. - [How Phones Sense Your Finger Hovering Without Touching the Screen](https://patentbrief.org/patent/us/7653883/multi-touch-trackpad-gestures) — This patent describes a system for electronic devices, like phones, to detect a finger hovering just above the screen, display a specific interactive element below it, and then let you control that element with gestures without ever making contact. - [Adjusting Touchscreen Sensitivity Based on Device Tilt Angle](https://patentbrief.org/patent/us/20160291760/contact-discrimination-using-a-tilt-angle-of-a-touch-sensitive-surface) — This patent describes how a computing device can decide if a touch on its screen is intentional or accidental by changing its sensitivity settings based on how much the device is tilted. - [How Touchscreens Ignore Accidental Hovering or Palm Touches](https://patentbrief.org/patent/us/10031618/identifying-hover-andor-palm-input-and-rejecting-spurious-input-for-a-touch-pane) — This Qualcomm patent describes how a touchscreen controller can tell the difference between an intentional finger touch and accidental input from a hovering finger or a palm, then ignore the unwanted input.