Proximity sensor including reference detector for stray radiation detection

Patent metadata

Field	Value
Publication number	US-9535157-B2
Application number	US-201414493553-A
Country	US
Kind code	B2
Filing date	Sep 23, 2014
Priority date	Sep 24, 2013
Publication date	Jan 3, 2017
Grant date	Jan 3, 2017

Abstract

A proximity sensor includes a radiation source configured to emit a primary radiation beam and a primary detector configured to pick up a reflected primary radiation beam. The radiation source is further configured to emit stray radiation. The sensor further includes a reference detector arranged to receive the stray radiation. The stray radiation may, for example, be emitted from either a side of the radiation source or a bottom of the radiation source.

First claim

What is claimed is:

1. A proximity sensor, comprising:
a substrate;
a radiation source mounted on the substrate and configured to emit a primary radiation beam;
a primary detector mounted on the substrate and configured to detect a reflection of said primary radiation beam off an object spaced apart from the proximity sensor by a distance;
a reference detector mounted on the substrate, co-located with the radiation source and configured to detect back emission stray radiation emitted from the radiation source; and
a time-digital converter coupled to the primary detector and reference detector, the time-digital converter configured to determine the distance as a function of an elapsed time between detection of the back emission stray radiation and detection of the reflection of the primary radiation beam off the object.

2. The proximity sensor of claim 1 , wherein the radiation source comprises a vertical cavity surface emitting laser (VCSEL) comprising a first mirror and a second mirror provided at respective upper and lower sides of an active layer and wherein the back emission stray radiation is emitted from the VCSEL.

3. The proximity sensor of claim 2 , wherein the second mirror is designed to have a lower than 100% reflectivity in order to encourage back emission stray radiation.

4. The proximity sensor of claim 1 , wherein a conductive material is provided to affix the radiation source to the substrate which carries the reference detector, said conductive material being formed to provide an electrical coupling between the radiation source and a bond pad which is carried on the substrate.

5. The proximity sensor of claim 1 , wherein the radiation source also comprises an at least partially transparent substrate.

6. The proximity sensor of claim 1 , wherein a transparent glue is provided to affix the radiation source to the substrate.

7. The proximity sensor of claim 1 , wherein the radiation source is provided with a first electrode at an upper surface, and a second electrode at a lower surface, said second electrode being formed from an optically transparent material.

8. The proximity sensor of claim 1 , wherein the radiation source is provided with a first electrode at an upper surface, and a second electrode at a lower surface, said second electrode being shaped to have a transparent portion configured to pass back emission stray radiation.

9. The proximity sensor of claim 8 , wherein said second electrode has an annular or grid shape.

10. The proximity sensor of claim 1 , wherein the radiation source comprises a light emitting diode (LED).

11. An apparatus, comprising:
a radiation source mounted on a substrate and configured to emit a primary radiation beam at an object spaced apart from the apparatus by a distance, the radiation source comprising:
a first mirror and a second mirror provided at respective upper and lower sides of an active layer;
wherein reflectivity of said first and second mirrors permits back emission of radiation towards the substrate;

a primary detector mounted on the substrate and configured to detect a reflection of the primary radiation beam off an object spaced apart from the apparatus;
a reference detector mounted on said substrate and configured to detect said back emission of radiation; and
a time-digital converter coupled to the primary detector and reference detector, the time-digital converter configured to determine the distance as a function of an elapsed time between detection of the back emission of radiation and detection of the reflection of the primary radiation beam off the object.

12. The apparatus of claim 11 , wherein the radiation source comprises a vertical cavity surface emitting laser (VCSEL).

13. The apparatus of claim 11 , wherein the second mirror is designed to have a reflectivity of less than 100%.

14. The apparatus of claim 13 , wherein a reflectivity of the first mirror is less than the reflectivity of the second mirror.

15. The apparatus of claim 11 , further comprising an at least partially transparent substrate upon which said first mirror, active layer and second mirror are provided.

16. The apparatus of claim 11 , further comprising an electrode beneath a structure comprising said first mirror, active layer and second mirror.

17. The apparatus of claim 16 , wherein the electrode is formed of a material that is both transparent and electrically conductive.

18. The apparatus of claim 16 , wherein the electrode is shaped to include an aperture or a transparent portion.

19. The apparatus of claim 11 , further comprising a light emitting diode (LED).

Assignees

• Stmicroelectronics (Research & Development) Ltd
• Stmicroelectronics (Grenoble 2) Sas
• St Microelectronics Crolles 2 Sas

Inventors

• Caley Adam
• Parodi-Keravec Pierre-Jean
• Le Briz Olivier
• Lhostis Sandrine

Classifications

• H10W72/884

  Die-attach connectors and bond wires · CPC title

• H10W90/754

  between a chip and a stacked insulating package substrate, interposer or RDL · CPC title

• G01S7/4811 Primary

  common to transmitter and receiver · CPC title

• G01S7/497

  Means for monitoring or calibrating · CPC title

• G01S17/04

  Systems determining the presence of a target · CPC title