Single photon avalanche diodes for rotational and translational input detection
An input component for an electronic device configured to detect rotational and/or translational movement of a surface. In an implementation, the input component includes a movable input member with a shaft with a pattern disposed on its surface. A light-emitting element is positioned to direct light towards this pattern, a portion of which is thereafter reflected back. An imaging system is situated to capture the reflected light. The imaging system includes an array of single-photon avalanche diodes (SPADs) operating in Geiger mode. This array is coupled with a counter circuit, which increments one or more values based on the SPAD array output. These values and corresponding SPAD locations within the array can be correlated to the spatial phase of the reflected light, which in turn can be converted to rotational or axial displacement of the movable input member.
1. An input component for a portable electronic device, the input component comprising:
a movable input member comprising a shaft;
a light emitting element oriented to emit light toward the shaft;
a pattern disposed on a surface of the shaft and configured to reflect the emitted light as reflected light;
an array of single-photon avalanche diodes (SPAD) configured to operate in Geiger mode; and
a counter circuit coupled to at least one SPAD of the array of SPADs, the counter circuit configured to increment a value in response to an output of the at least one SPAD, the value:
informing a determination of spatial phase of the reflected light; and
corresponding to a rotation of the shaft of the movable input member.
2. The input component of claim 1 , wherein:
the at least one SPAD is a member of a group of SPADs selected from the array of SPADs; and
the counter circuit is configured to iterate the value in response to each output of each member of the group of SPADs.
3. The input component of claim 2 , comprising a mask disposed over at least a portion of the group of SPADs.
4. The input component of claim 3 , wherein the mask partially overlaps the at least one SPAD.
5. The input component of claim 4 , wherein:
the at least one SPAD is a first SPAD; and
the mask entirely covers a second SPAD of the group of SPADs.
6. The input component of claim 5 , wherein:
the value is a first value; and
an imaging system is configured to use a second value output from the second SPAD as a calibration to modify the first value.
7. The input component of claim 3 , wherein the mask comprises a metal layer disposed over the SPAD array.
8. The input component of claim 3 , wherein the mask comprises a material opaque to the emitted light.
9. The input component of claim 1 , wherein the value corresponds to a translation of the shaft of the movable input member.
10. An input component for a portable electronic device, comprising:
a movable input member comprising a surface;
a pattern defined on the surface;
a light emitting element oriented to emit light toward the pattern such that the movable input member reflects the emitted light as reflected light; and
an imaging system oriented to receive the reflected light and comprising:
an array of single-photon avalanche diodes (SPAD) configured to operate in Geiger mode; and
a counter circuit coupled to at least one SPAD of the array of SPADs, the counter circuit configured to iterate a value in response to an output of the at least one SPAD, the value:
informing a determination of spatial phase of the reflected light; and
the spatial phase corresponding to a movement of the movable input member.
11. The input component of claim 10 , wherein the movement of the movable input member is a translation relative to a housing of the portable electronic device.
12. The input component of claim 10 , wherein movement of the movable input member is a rotation relative to a housing of the portable electronic device.
13. The input component of claim 10 , wherein movement of the movable input member is a tilt relative to a housing of the portable electronic device.
14. The input component of claim 10 , wherein movement of the movable input member comprises at least two of a rotation, a tilt, or a translation relative to a housing of the portable electronic device.
15. The input component of claim 10 , wherein the light emitting element emits infrared light.
16. An input component for a portable electronic device, the input component comprising:
a movable input member comprising a surface on which is defined a pattern;
a light emitting element oriented to emit light toward the pattern such that the pattern on the movable input member reflects the emitted light as reflected light;
an array of single-photon avalanche diodes (SPAD) biased to at least breakdown voltage; and
a circuit conductively coupled to the array of SPADs and configured to determine a spatial phase of the reflected light relative to the array of SPADs.
17. The input component of claim 16 , wherein the array of SPADs is two-dimensional.
18. The input component of claim 16 , wherein the array of SPADs extends along an axis of rotation of the movable input member.
19. The input component of claim 16 , comprising a mask layer disposed over the array of SPADs.
20. The input component of claim 19 , wherein the mask layer is formed from metal disposed over the array of SPADs.