Apple Inc.
Surface Confined Self-Mixing Interferometry Through Frustrated Total Internal Reflection for an Electronic Device

Abstract:

A self-mixing interference sensor may be positioned within an electronic device and may be configured to detect a gesture on a user input surface of the electronic device. A beam of electromagnetic radiation may be emitted from the self-mixing interference sensor toward the user input surface. When an object with a suitable refractive index is not in contact with the user input surface, the beam of electromagnetic radiation may reflect away from the self-mixing interference sensor. When an object with a suitable refractive index is in contact with the user input surface, the beam of electromagnetic radiation may reflect back into the self-mixing interference sensor and may undergo a self-mixing process. A property of the object in contact with the surface of the user input device may be detected by measuring a change in an optical property of the beam of electromagnetic radiation.