New Apple patent application describes pressure sensitive touchscreen technology

A new patent application from Apple describes a method of adding pressure sensitivity to a touchscreen using a combination of capacitive touch, infrared light and other sensing technologies. The patent was first reported by AppleInsider. The patent application, Frustrated Total Internal Reflection and Capacitive Sensing, was published by the U.S. Patent and Trademark Office on Thursday. The method uses frustrated total internal reflection (FTIR), which is used in biometrics to capture fingerprints, along with other touch sensor technologies to detect how hard a user is pressing on a screen. In one example, Apple uses FTIR along with IR transmitters that are embedded beneath a device’s bezel. Other embodiments describe methods of FTIR measurement using OLED layers, ultrasonic or other acoustic signals. Detecting force and touch using FTIR and capacitive location. FTIR determines applied force by the user’s finger within infrared transmit lines on a touch device. A pattern of such lines determine optical coupling with the touch device. Capacitive sensing can determine (A) where the finger actually touches, so the touch device more accurately infers applied force; (B) whether finger touches shadow each other; (C) as a baseline for applied force; or (D) whether attenuated reflection is due to a current optical coupling, or is due to an earlier optical coupling, such as a smudge on the cover glass. If there is attenuated reflection without actual touching, the touch device can reset a baseline for applied force for the area in which that smudge remains. Infrared transmitters and receivers are positioned where they are not visible to a user, such as below a frame or mask for the cover glass. It’s not clear how Apple will use this technology in existing devices, but the technology could pave the way for novel interactions beyond the simple tap and hold to manipulate onscreen elements on a smartphone or tablet device. Continue reading →

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