Laser-based rotation sensor for a crown of an electronic watch

1. An electronic watch comprising:

a housing;

a crown assembly comprising:

a rotatable actuation member comprising:

a knob external to the housing and configured to receive a rotational input; and

a shaft assembly coupled to the knob and positioned at least partially within the housing, the shaft assembly defining a sensing surface configured to rotate in response to the rotational input; and

an optical sensing system configured to detect the rotational input using operations including,

directing light onto the sensing surface;

receiving reflected light from the sensing surface; and

producing a signal corresponding to a rotational motion of the sensing surface, the signal based at least in part on an interference between the light directed onto the sensing surface and the reflected light.

2. The electronic watch of claim 1 , wherein:

the electronic watch is configured to determine a speed and a direction of the rotational motion of the sensing surface based on the signal;

the electronic watch further comprises:

a display positioned at least partially within the housing and configured to display a graphical output;

a transparent cover coupled to the housing; and

a touch sensor positioned below the transparent cover and configured to detect touch inputs applied to the transparent cover; and

the electronic watch is configured to modify the graphical output in accordance with the speed and the direction of the rotational motion of the sensing surface.

3. The electronic watch of claim 1 , wherein a beam axis of the light directed onto the sensing surface is oblique to the sensing surface.

4. The electronic watch of claim 1 , wherein:

the light directed onto the sensing surface includes a laser beam;

the reflected light is a reflected portion of the laser beam; and

the optical sensing system comprises a laser module configured to emit the laser beam and receive the reflected portion of the laser beam.

5. The electronic watch of claim 4 , wherein:

the laser module is a vertical cavity surface emitting laser;

the vertical cavity surface emitting laser detects a difference in frequency between the emitted laser beam and the reflected portion of the laser beam; and

the signal is based at least in part on the difference in the frequency.

6. The electronic watch of claim 4 , wherein:

the laser beam is a first laser beam;

the laser module is a first laser module; and

the optical sensing system further comprises a second laser module configured to:

emit a second laser beam, the second laser beam being directed onto the sensing surface; and

receive a reflected portion of the second laser beam.

7. The electronic watch of claim 1 , wherein:

the shaft assembly comprises a disk member; and

the sensing surface is a planar surface of the disk member.

8. An electronic watch comprising:

a housing;

a crown assembly configured to receive a rotational input and defining a sensing surface at least partially within the housing and configured to rotate in response to the rotational input; and

an optical sensing system comprising a laser module configured to:

emit a beam of coherent light; and

receive a reflected portion of the beam, the reflected portion of the beam reflected from the sensing surface of the crown assembly;

wherein the optical sensing system is configured to produce a signal corresponding to a rotational motion of the sensing surface of the crown assembly, the signal based at least in part on a difference in frequency between the emitted beam and the reflected portion of the beam.

9. The electronic watch of claim 8 , wherein:

a rotational motion in a first direction corresponds to the reflected portion of the beam having a lower frequency than the emitted beam; and

a rotational motion in a second direction opposite the first direction corresponds to the reflected portion of the beam having a higher frequency than the emitted beam.

10. The electronic watch of claim 8 , wherein:

a rotational motion in a first direction and having a first rotational speed corresponds to the reflected portion of the beam having a first frequency; and

a rotational motion in the first direction and having a second rotational speed corresponds to the reflected portion of the beam having a second frequency that is different from the first frequency.

11. The electronic watch of claim 10 , wherein:

the first rotational speed is higher than the second rotational speed; and

the first frequency is higher than the second frequency.

12. The electronic watch of claim 11 , wherein:

the emitted beam has a third frequency; and

the first frequency and the second frequency are different than the third frequency.

13. The electronic watch of claim 8 , wherein:

the emitted beam is directed onto the sensing surface in a first direction along a path;

the reflected portion of the beam is reflected from the sensing surface in a second direction along the path, the second direction opposite to the first direction; and

an incident portion of the beam is not perpendicular to the sensing surface of the crown assembly.

14. The electronic watch of claim 13 , wherein:

the laser module is a vertical cavity surface emitting laser;

the reflected portion of the beam changes at least one of a frequency or an amplitude of light produced by the vertical cavity surface emitting laser; and

the change of the at least one of the frequency or the amplitude of the light produced by the vertical cavity surface emitting laser corresponds to the difference in frequency between the emitted beam and the reflected portion of the beam.

15. The electronic watch of claim 8 , wherein the difference in frequency between the emitted beam and the reflected portion of the beam is caused by a Doppler effect.

16. An electronic device comprising:

a housing;

a crown assembly configured to receive a rotational input and defining a sensing surface at least partially within the housing and configured to rotate in response to the rotational input; and

an optical sensing system comprising a laser module configured to:

emit a laser beam, the emitted laser beam directed along a path segment in a first direction onto the sensing surface; and

receive a reflected portion of the laser beam, the reflected portion reflected from the sensing surface and travelling along the path segment in a second direction opposite to the first direction;

wherein the optical sensing system is configured to produce a signal corresponding to a rotational motion of the sensing surface of the crown assembly, the signal based at least in part on an interaction between the emitted laser beam and the reflected portion of the laser beam.

17. The electronic device of claim 16 , wherein the path segment does not intersect a rotational axis of the crown assembly.

18. The electronic device of claim 16 , wherein the optical sensing system further comprises a beam-directing structure configured to aim the laser beam along the path segment.

19. The electronic device of claim 18 , wherein the beam-directing structure defines a reflecting surface configured to aim the laser beam along the path segment.

20. The electronic device of claim 18 , wherein:

the electronic device further comprises a collar attached to the housing and configured to retain the crown assembly to the housing;

the beam-directing structure is coupled to a mounting structure; and

the mounting structure is adhered to the collar, thereby fixing an orientation of the beam-directing structure relative to the crown assembly.