US-20260126531-A1 - POLARIZATION-BASED CROSSTALK MITIGATION IN OPTICAL RANGING SENSORS

US20260126531A1US 20260126531 A1US20260126531 A1US 20260126531A1US-20260126531-A1

Abstract

An example optical ranging sensor, a method for determining a proximity of a target at an optical ranging sensor, and a mobile electronic device comprising an optical ranging sensor are provided. The example optical ranging sensor includes an optical transmitter, an optical receiver, and a controller. The optical transmitter configured to generate a first signal having a first polarization state and a second signal having a second polarization state. The optical receiver configured to generate a first feedback signal resulting from one or more reflections of the first signal, and a second feedback signal resulting from one or more reflections of the second signal. The controller configured to generate a target feedback signal based on a comparison of the first feedback signal and the second feedback signal and determine a proximity of a target based on the target feedback signal.

Inventors

Stuart MCLEOD
James Peter Drummond DOWNING

Assignees

STMICROELECTRONICS INTERNATIONAL N.V.

Dates

Publication Date: 20260507
Application Date: 20241105

Claims (20)

1 . An optical ranging sensor comprising: an optical transmitter configured to generate a first signal having a first polarization state and a second signal having a second polarization state; an optical receiver configured to generate: a first feedback signal resulting from one or more reflections of the first signal; and a second feedback signal resulting from one or more reflections of the second signal; and a controller configured to: generate a target feedback signal based on a comparison of the first feedback signal and the second feedback signal; and determine a proximity of a target based on the target feedback signal.
2 . The optical ranging sensor of claim 1 , wherein the target feedback signal corresponds to a portion of the first signal reflected off the target.
3 . The optical ranging sensor of claim 2 , wherein to generate the target feedback signal, the controller is further configured to: generate a first histogram corresponding to the first feedback signal; generate a second histogram corresponding to the second feedback signal; and generate the target feedback signal based on a comparison of the first histogram and the second histogram.
4 . The optical ranging sensor of claim 1 , wherein to generate the target feedback signal, the controller is further configured to: determine a crosstalk difference signal by performing a difference between the first feedback signal and the second feedback signal; and apply a crosstalk function to determine a total crosstalk signal, wherein the crosstalk function relates the crosstalk difference to the total crosstalk signal.
5 . The optical ranging sensor of claim 4 , wherein the crosstalk function is determined during a calibration period.
6 . The optical ranging sensor of claim 1 , wherein the proximity of the target is based on a time-of-flight associated with the target feedback signal.
7 . The optical ranging sensor of claim 1 , wherein the first polarization state is orthogonal to the second polarization state.
8 . The optical ranging sensor of claim 1 , wherein the optical transmitter is configured to alternate between generating the first signal having the first polarization state and the second signal having the second polarization state.
9 . The optical ranging sensor of claim 8 , wherein the optical transmitter alternates between generating the first signal having the first polarization state and the second signal having the second polarization state after each integration period.
10 . The optical ranging sensor of claim 9 , wherein the optical transmitter is a vertical-cavity surface-emitting laser.
11 . The optical ranging sensor of claim 10 , wherein the vertical-cavity surface-emitting laser is configured to generate the first signal having the first polarization state and the second signal having the second polarization state based on a polarization control signal transmitted by the controller.
12 . A method for determining a proximity of a target at an optical ranging sensor, the method comprising: causing an optical transmitter to transmit a first signal having a first polarization state; receiving from an optical receiver a first feedback signal resulting from one or more reflections of the first signal; causing the optical transmitter to transmit a second signal having a second polarization state; receiving from the optical receiver a second feedback signal resulting from one or more reflections of the second signal; generating a target feedback signal based on a comparison of the first feedback signal and the second feedback signal; and determining the proximity of the target based on the target feedback signal.
13 . The method of claim 12 , wherein the target feedback signal corresponds to a portion of the first signal reflected off the target.
14 . The method of claim 13 , wherein generating the target feedback signal further comprises: generating a first histogram corresponding to the first feedback signal; generating a second histogram corresponding to the second feedback signal; and generating the target feedback signal based on a comparison of the first histogram and the second histogram.
15 . The method of claim 12 , wherein generating the target feedback signal further comprises: determining a crosstalk difference signal by performing a difference between the first feedback signal and the second feedback signal; and applying a crosstalk function to determine a total crosstalk signal, wherein the crosstalk function relates the crosstalk difference to the total crosstalk signal.
16 . The method of claim 12 , wherein determining the proximity of the target further comprises: determining a time-of-flight associated with the target feedback signal.
17 . The method of claim 12 , wherein the first polarization state is orthogonal to the second polarization state.
18 . The method of claim 12 , further comprising: causing the optical transmitter to alternate between generating the first signal having the first polarization state and the second signal having the second polarization state.
19 . The method of claim 18 , wherein the optical transmitter alternates between generating the first signal having the first polarization state and the second signal having the second polarization state after each integration period.
20 . A mobile electronic device comprising: a housing; a display screen attached to the housing, the display screen comprising: a first side configured to emit transmitted light via a plurality of display pixels into an external environment; and an optical ranging sensor disposed within the housing, opposite the first side of the display screen, the optical ranging sensor comprising: an optical transmitter configured to generate a first signal having a first polarization state and a second signal having a second polarization state; an optical receiver configured to receive: a first feedback signal resulting from one or more reflections of the first signal; and a second feedback signal resulting from one or more reflections of the second signal; and a controller configured to: generate a target feedback signal based on a comparison of the first feedback signal and the second feedback signal; and determine a proximity of a target based on the target feedback signal.

Description

TECHNOLOGICAL FIELD Embodiments of the present disclosure relate generally to optical ranging sensors, and more particularly, to mitigating inconsistencies due to crosstalk at an optical ranging sensor. BACKGROUND Optical ranging sensors may include an optical transmitter and an optical receiver. During operation, the optical ranging sensor transmits light toward a target object through one or more optically transmissive components, such as a coverglass. The transmitted light reflects off the target object and is received by the light receiver on the optical ranging sensor. The received light is used to extract useful information like the distance of the target object, the motion of the target object, the speed of the target object, surface properties of the target object, and so on. Light received at the optical receiver from unwanted sources, such as crosstalk light reflecting off a coverglass, may adversely affect the accuracy of an optical ranging sensor. Applicant has identified many technical challenges and difficulties associated with mitigating crosstalk at an optical ranging sensor. Through applied effort, ingenuity, and innovation, Applicant has solved problems related to crosstalk at an optical ranging sensor by developing solutions embodied in the present disclosure, which are described in detail below. BRIEF SUMMARY Various embodiments are directed to an example optical ranging sensor, a method for determining a proximity of a target at an optical ranging sensor, and a mobile electronic device comprising an optical ranging sensor. An example optical ranging sensor is provided. The example optical ranging sensor includes an optical transmitter, an optical receiver, and a controller. The optical transmitter configured to generate a first signal having a first polarization state and a second signal having a second polarization state. The optical receiver configured to generate a first feedback signal resulting from one or more reflections of the first signal, and a second feedback signal resulting from one or more reflections of the second signal. The controller configured to generate a target feedback signal based on a comparison of the first feedback signal and the second feedback signal; and determine a proximity of a target based on the target feedback signal. In some embodiments, the target feedback signal corresponds to a portion of the first signal reflected off the target. In some embodiments, to generate the target feedback signal, the controller is further configured to: generate a first histogram corresponding to the first feedback signal; generate a second histogram corresponding to the second feedback signal; and generate the target feedback signal based on a comparison of the first histogram and the second histogram. In some embodiments, to generate the target feedback signal, the controller is further configured to: determine a crosstalk difference signal by performing a difference between the first feedback signal and the second feedback signal; and apply a crosstalk function to determine a total crosstalk signal, wherein the crosstalk function relates the crosstalk difference to the total crosstalk signal. In some embodiments, the crosstalk function is determined during a calibration period. In some embodiments, the proximity of the target is based on a time-of-flight associated with the target feedback signal. In some embodiments, the first polarization state is orthogonal to the second polarization state. In some embodiments, the optical transmitter is configured to alternate between generating the first signal having the first polarization state and the second signal having the second polarization state. In some embodiments, the optical transmitter alternates between generating the first signal having the first polarization state and the second signal having the second polarization state after each integration period. In some embodiments, the optical transmitter is a vertical-cavity surface-emitting laser. In some embodiments, the vertical-cavity surface-emitting laser is configured to generate the first signal having the first polarization state and the second signal having the second polarization state based on a polarization control signal transmitted by the controller. An example method for determining a proximity of a target at an optical ranging sensor is further provided. The example method comprising: causing an optical transmitter to transmit a first signal having a first polarization state; receiving from an optical receiver a first feedback signal resulting from one or more reflections of the first signal; causing the optical transmitter to transmit a second signal having a second polarization state; receiving from the optical receiver a second feedback signal resulting from one or more reflections of the second signal; generating a target feedback signal based on a comparison of the first feedback signal and the second feedback signal; and determining the proximity