The patent describes a method of decoupling a keyboard’s mechanical feel from its electrical functionality using proximity sensors

Detailed in a patent published by the U.S. Patent and
Trademark Office earlier this month, an Apple invention describes a method of
decoupling a keyboard’s mechanical feel from its electrical functionality by
using proximity sensors. The patent, titled “Depressible keys with decoupled
electrical and mechanical functionality,” shows a computer keyboard that
replaces common contemporary keyboards, which rely on electromechanical
actuators to transmit key press signals to a central processing unit.

Apple_Proximity_Sensor_Keyboard

The components in modern keyboards typically incorporate
multiple structures under a single keycap, such as a key travel mechanism,
tactile feedback structure, and electrical contacts or electrodes. Due to
tight space constraints in modern keyboards, especially laptop versions, the
tactile feedback component is often nested within the key travel mechanism
below the electrical traces. The parts sandwich inhibits independent component
modification, as a manufacturer must rework the entire system to achieve
different keyboard experiences. 

Users, on the other hand, have varying tastes when
it comes to tactile feedback, as some prefer a slow, silent key press, while
others prefer the clacking sounds with long throws.

To cater to individual user preferences, Apple
proposed a method for decoupling the mechanical and tactile functionality of a
key from its electrical functionality. To be more specific, the document
replaces the electrical contacts and traces with non-contact proximity sensors,
while travel mechanism and feedback structures remain intact.

In most of its embodiments, Apple’s key design features a light emitter
aimed at the reflective bottom surface of a keycap. An accompanying light
detector, or central detector connected to a light guide, is used to generate
an electrical signal in response to the received light. When processed by a
keyboard controller, the signals can estimate force, velocity, and distance
metrics to accurately determine when a key is pressed. By applying
pre-determined thresholds to incoming signals, the invention can in some cases
detect errant key presses and support force-sensitive input applications. 

Other embodiments include dynamic threshold adjustments on a per-key and
per-application basis, which allows users to set one input level for word
processing and another for gaming. The
invention also includes contingencies for installing structures formed
from materials capable of elastic deformation, such as an electroactive polymer
or shape-memory metal. In some embodiments, users can adjust the feel of such
components on the fly.

Though it’s unclear whether Apple will implement its customizable
keyboard in a future Mac product, the company is expected to announce new Mac
hardware at an upcoming event this month. 

Source: Apple
Insider