Waveguide-Based Interferometric Multi-Point/Distributed Force and Touch Sensors

A self-mixing interference sensing system, comprising:

• an input surface;
• an optical waveguide positioned beneath the input surface and defining a set of distinct sensing locations on the input surface;
• a light source configured to emit light into the optical waveguide;
• and
• processing electronics operably coupled with the light source, wherein:
• an input applied to a sensing location of the set of distinct sensing locations causes a portion of the emitted light to reflect back toward the light source through the optical waveguide;
• the portion of the emitted light that is reflected back toward the light source enters the light source, self-mixes with light generated by the light source, and changes an operational parameter of the light source;
• and
• the processing electronics apply a spectrum analysis to the operational parameter to identify the sensing location of the set of distinct sensing locations near the input.

An electronic device, comprising:

• an input surface comprising a reflective coating;
• a laser light source configured to emit a laser light;
• an optical waveguide configured to receive the emitted laser light and direct portions of the emitted laser light toward respective multiple sensing locations on the input surface;
• and
• processing electronics operably coupled with the laser light source, wherein:
• an input applied to a sensing location of the multiple sensing locations causes a portion of the laser light directed toward the sensing location to re-enter the optical waveguide and reflect toward the laser light source;
• and
• a self-mixing of light occurs within a lasing cavity of the laser light source when the portion of the laser light is received within the laser light source;
• and
• the processing electronics analyzes an operational parameter of the laser light source that is affected by the self-mixing to identify the sensing location of the multiple sensing locations corresponding to the input.

A method for detecting an input applied to a surface of an electronic device, the method comprising:

• emitting laser light generated in a lasing cavity into an optical waveguide having a plurality of out-couplers defining a respective plurality of sensing locations on an input surface;
• receiving a reflected portion of the emitted laser light into the lasing cavity;
• self-mixing the reflected portion of the emitted laser light with the laser light generated in the lasing cavity;
• analyzing a change in an operational parameter of the lasing cavity to identify a sensing location of the plurality of sensing locations at which an input is applied to the surface.