Optical Interferometry Proximity Sensor with Temperature Variation Compensation

Patent metadata

Field	Value
Publication number	US-2020200522-A1
Application number	US-201816230967-A
Country	US
Kind code	A1
Filing date	Dec 21, 2018
Priority date	Dec 21, 2018
Publication date	Jun 25, 2020
Grant date	—

Abstract

An optical proximity sensor includes a first vertical cavity surface-emitting laser configured for self-mixing interferometry to determine distance to and/or velocity of an object. The optical proximity sensor also includes a second vertical cavity surface-emitting laser configured for self-mixing interferometry to determine whether any variation in a fixed distance has occurred. The optical proximity sensor leverages output from the second vertical cavity surface-emitting laser to calibrate output from the second vertical cavity surface-emitting laser to eliminate and/or mitigate environmental effects, such as temperature changes.

First claim

What is claimed is:

1 . An optical proximity sensor comprising:
an enclosure defining an aperture; a primary VCSEL within the enclosure and oriented to emit a first beam of light through the aperture; an auxiliary VCSEL within the enclosure and oriented to emit a second beam of light toward an internal surface of the enclosure; and a power controller configured to:
monitor a power output of the primary VCSEL light source and the auxiliary VCSEL light source;
determine a distance to an object based, at least in part, on the power output of the primary VCSEL; and
modify the determined distance to the object based, at least in part, on the power output of the auxiliary VCSEL.

2 . The optical proximity sensor of claim 1 , wherein the power controller is configured to monitor the power output of the primary VCSEL for self-mixing interference effects.

3 . The optical proximity sensor of claim 1 , wherein the power controller is configured to drive each of the first VCSEL light source and the auxiliary VCSEL light source.

4 . The optical proximity sensor of claim 1 , wherein the power controller is configured to drive each of the first VCSEL light source and the auxiliary VCSEL light source with a triangular current waveform.

5 . The optical proximity sensor of claim 1 , wherein the power controller is configured to determine a velocity of the object based, at least in part, on the power output of the primary VCSEL.

6 . The optical proximity sensor of claim 1 , wherein the auxiliary VCSEL is disposed adjacent to the primary VCSEL such that the primary VCSEL and the auxiliary VCSEL experience substantially the same thermal environment.

7 . The optical proximity sensor of claim 1 , further comprising a transparent optical adapter disposed within the aperture.

8 . The optical proximity sensor of claim 7 , wherein the optical adapter comprises a lens.

9 . The optical proximity sensor of claim 7 , wherein the enclosure is formed from an opaque material.

10 . An optical proximity sensor comprising:
a primary light source oriented to emit a first coherent beam of light in a first direction; a first photodiode optically coupled to the primary light source; an auxiliary light source adjacent to the primary light source and oriented to emit a second coherent beam of light in a second direction toward a reflective surface separated from the auxiliary light source by a fixed distance; a second photodiode optically coupled to the auxiliary light source; and a power controller configured to:
monitor a power output of the first photodiode and the second photodiode;
determine a property of an object reflecting the first beam of light based, at least in part, on power output of the first photodiode; and
modify the determined property based, at least in part, on power output of the second photodiode.

11 . The optical proximity sensor of claim 10 , wherein the property is one of distance, velocity, or acceleration.

12 . The optical proximity sensor of claim 10 , wherein the reflective surface is formed from at least one of a metal material or a multilayer dielectric stack.

13 . The optical proximity sensor of claim 10 , wherein the object is an interior surface of a housing of an electronic device.

14 . A method of determining distance between an object and an electronic device, the method comprising:
emitting, from a first light source in an optical proximity sensor, a first coherent beam of light toward the object; emitting, from a second light source in the optical proximity sensor, a second coherent beam of light toward a surface that is interior to the electronic device; monitoring power output of the first light source and the second light source for self-mixing interference effects; determining a first distance measurement to the object based on self-mixing interference effects of the first light source; determining a second distance measurement to the surface based on self-mixing interference effects of the second light source; and modifying the first distance measurement based on the second distance measurement.

15 . The method of claim 14 , wherein a distance separating the second light source from the surface is a fixed distance.

16 . The method of claim 15 , further comprising modifying the first distance based on the second distance measurement and the fixed distance measurement.

17 . The method of claim 14 , wherein each of the first light source and the second light source is a VCSEL light source.

18 . The method of claim 14 , further comprising driving the first light source and the second light source with a triangular current waveform.

19 . The method of claim 14 , further comprising:
determining a velocity of the object based on self-mixing interference effects of the first light source; and modifying the velocity based, at least in part, on the second distance measurement.

20 . The method of claim 14 , wherein monitoring power output of the first light source and the second light source for self-mixing interference effects comprises monitoring power output by a first photodiode optically coupled to the first light source and monitoring power output by a second photodiode optically coupled to the second light source.

Assignees

• Apple Inc

Inventors

• Huang Mengshu
• Dudley James J

Classifications

• G01S17/58

  Velocity or trajectory determination systems; Sense-of-movement determination systems · CPC title

• G01S17/32

  using transmission of continuous waves, whether amplitude-, frequency-, or phase-modulated, or unmodulated · CPC title

• G01S7/497

  Means for monitoring or calibrating · CPC title

• H01S5/02257

  using windows, e.g. specially adapted for back-reflecting light to a detector inside the housing · CPC title

• H01S5/02253

  using lenses · CPC title