Apple Watch 3D force-sensing can turn Digital Crown into a joystick

The Apple Watch has many ways to interact with the compact wearable device, and one of those is the Digital Crown. A throwback to earlier watch designs that used a crown for setting the time and for winding up the mechanism, the Digital Crown can be pressed in and rotated to give more interaction options.

While it is relatively limited in terms of what it can be used for at present, Apple believes it could be upgraded in a few ways to make it even more useful.

In a patent granted by the U.S. Patent and Trademark Office on Tuesday called "Tri-axis force sensor," Apple envisions that the Digital Crown could be pressed or moved in different directions. This is on top of the existing functionality of the crown being pressed in like a button, and being able to rotate the controller.

In effect, this would turn the Digital Crown into a form of joystick, with lateral movements accompanying the existing rotation and pressing mechanics.

The filing has Apple suggesting the input device can check for force inputs along three axes relative to the electric device. Namely the Digital Crown in relation to the Apple Watch.

To accomplish this, Apple believes it can use force or displacement sensors within the component, to detect the direction and magnitude of input forces.

These sensors could be placed and positioned in different ways, depending on the implementation. For example, a version could involve force sensors under the surface of the crown that can detect the pressure of a press in, or could be displaced in multiple locations to detect lateral or oblique forces.

This first configuration uses a cap over a large stem, with the force sensor sandwiched between the stem and the cap. A second version takes a more traditional design of a crown that actually moves the stem.

In this second configuration, some of the force sensors are located deeper into the body, and are sensing movements of the opposite end of the stem. Some electrodes would still be used under the cap to detect rotation, but the bulk of sensing would be at the other end of the stem.

To aid in water resistance, the second configuration would employ o-rings in the middle for a close seal around the stem.

The patent lists its inventors as Colin M. Ely, Erik G. de Jong, and Steven P. Cardinali. It was originally filed on January 24, 2018.

Apple files many patent applications on a weekly basis, but while the existence of a patent indicates areas of interest for Apple's research and development efforts, they don't guarantee the idea will appear in a future product or service.

Apple has been considering other ways for users to interact with the digital crown, and joystick-like control has appeared previously. The December 2019 filing for a "Capacitive gap sensor ring for an electronic watch" suggested the monitoring of capacitive elements to determine physical positions of an internal element in relation to crown movements.

Another application from January 2020 proposed the use of an optical sensor and touch response, effectively becoming a touch sensor and eliminating the crown concept entirely. A third one month later in February 2020 offered touch and light-sensing capabilities while retaining the crown idea.

There has also been the suggestion a Digital Crown-like control could be included in "Apple Glass," Apple's long-rumored AR headset. A patent application found in March 2021 mentions the use of a similar dial for interactivity.