Apple was recently awarded a patent that would allow its touchscreen devices to detect how hard the user presses on the display. The patent, first noted by Apple Insider, uses a technology called frustrated total internal reflection, or FTIR, along with current capacitive touch sensors to determine force applied to the screen.
FTIR uses infrared lights to bounce light off the back of a touchscreen. If there is no interference, or frustration, then the infrared light will completely reflect off the surface of the touchscreen, similar to how the surface of a pool can act as a mirror when viewed at high enough angles. If there is interference from a finger on the touchscreen, then sensors will pick it up in order to determine where the touch input hit the display.
Apple’s patent takes advantage of both FTIR and the capacitive touch sensors it already uses to determine how hard the touchscreen was pressed by comparing the FTIR interference with the capacitive touch data.
Previously, Apple has tried to estimate force by using its mobile devices’ accelerometer. For example, Apple takes advantage of this in its GarageBand iOS app, which can determine how hard you tap a key on its virtual keyboard and adjust the volume accordingly.
As Apple Insider notes, this patent could be used to allow for more expressive touch input beyond the current “tap” and “hold.”