Proximity sensor

• US 8,928,893 B2
• Filed: 09/23/2011
• Issued: 01/06/2015
• Est. Priority Date: 11/30/2010
• Status: Active Grant

• Current Assignee: STMicroelectronics Grenoble 2 SAS (STMicroelectronics NV), Stmicroelectronics (Research & Development) Limited (STMicroelectronics NV)
• Original Assignee: STMicroelectronics Grenoble 2 SAS (STMicroelectronics NV), Stmicroelectronics (Research & Development) Limited (STMicroelectronics NV)
• Inventors: Findlay, Ewan, Campbell, Colin, Ramsey, Gemma, Saugier, Eric
• Primary Examiner(s): Chowdhury, Tarifur
• Assistant Examiner(s): Gray, Sunghee Y
• Application Number:
  US13/242,708
• Publication Number:
  US 20120133956A1
• Time in Patent Office: 1,201 Days
• Field of Search: 356/614, 250/551, 250/214.AL, 398/130, 398/128, 398/15
• US Class Current: 356/614
• CPC Class Codes: H01L 25/167 comprising optoelectronic devices, e.g. LED, photodiodes
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/0002 Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00
• CPC Class Codes: H01L 31/125 Composite devices with photosensitive elements and electroluminescent elements within one single body
• CPC Class Codes: H01L 31/173 formed in, or on, a common substrate
• CPC Class Codes: H03K 17/941 using an optical detector H03K17/968 takes precedence
• CPC Class Codes: H03K 2017/9455 constructional details
• CPC Class Codes: H03K 2217/94108 making use of reflection

Abstract

The internal propagation of radiation between a radiation source and radiation detector mounted within a sensor package is prevented by the use of an optical isolator. The optical isolator is formed by the combination of a baffle mounted between the source and detector and a groove formed in an upper surface of the sensor package between the source and detector. A bottom of the groove is positioned adjacent to an upper edge of the baffle.

Claims

1. A proximity sensor comprising:

a sensor package comprising a lens module;

a radiation source and a radiation detector housed within the sensor package, the lens module of the sensor package being positioned over the source and the detector; and

an optical isolator adapted to substantially prevent internal propagation of radiation between the source and the detector within the sensor package,

the optical isolator comprising;

a baffle positioned within the sensor package between the source and the detector, said baffle comprising opposed side surfaces and an upper edge extending between the opposed side surfaces; and

a groove formed in an upper surface of the lens module, a bottom-most part of the groove being positioned adjacent to said upper edge of the baffle.

2. The proximity sensor of claim 1 wherein the bottom of the groove is positioned at or above and vertically aligned with the upper edge of the baffle.

3. The proximity sensor of claim 1 wherein the baffle is opaque to radiation emitted by the source.

4. The proximity sensor of claim 1 further comprising a substantially planar attachment pad housed within the sensor package.

5. The proximity sensor of claim 4 wherein the source and the detector are mounted on the attachment pad.

6. The proximity sensor of claim 4 wherein the baffle is mounted or formed on the attachment pad.

7. The proximity sensor of claim 1 wherein the lens module comprises a recess for receiving a portion of the baffle.

8. The proximity sensor of claim 7 further comprising a substantially planar attachment pad housed within the sensor package, wherein the baffle extends from the attachment pad into the lens module recess.

9. The proximity sensor of claim 1 wherein said groove comprises a plurality of separated grooves formed in the upper surface of the lens module, and wherein the bottom of at least one of the plurality of separated grooves is coplanar with the upper edge of the baffle.

10. The proximity sensor of claim 1 wherein the lens module comprises first and second lenses.

11. The proximity sensor of claim 1 wherein the lens module is formed as a single part.

12. The proximity sensor of claim 1 wherein one or more selected portions of the lens module are covered by a material opaque to radiation emitted by the radiation source.

13. The proximity sensor of claim 1 further comprising a substantially planar attachment pad housed within the sensor package, wherein the sensor package further comprises a lens module mount formed around a perimeter of the attachment pad and extending between the attachment pad and the lens module.

14. The proximity sensor of claim 13 wherein at least part of the lens module mount is opaque to radiation emitted by the radiation source.

15. The proximity sensor of claim 1 wherein the groove of the optical isolator has a V-shape configured to reflect radiation towards the lens module mount.

16. The proximity sensor of claim 1 wherein the radiation source is mounted at the bottom of a well comprising an aperture.

17. The proximity sensor of claim 16 further comprising a substantially planar attachment pad housed within the sensor package, wherein the well is formed on the attachment pad.

18. The proximity sensor of claim 16 wherein the lens module comprises a lens positioned over the aperture for collimating radiation emitted by the radiation source through the aperture.

19. The proximity sensor of claim 18 wherein the lens module further comprises a second lens positioned over the radiation detector.

20. The proximity sensor of claim 1 wherein the radiation detector comprises a pixel array.

21. The proximity sensor of claim 20 wherein the pixel array comprises a plurality of single photon avalanche detectors.

22. The proximity sensor of claim 1 further comprising common circuitry housed within the sensor package for controlling the source and the detector.

23. The proximity sensor of claim 1 wherein the optical isolator substantially prevents the propagation of radiation between the source and the detector by total internal reflection within the sensor package.

24. A method of manufacturing a proximity sensor comprising:

(a) housing a radiation source and a radiation detector within a sensor package;

(b) fitting or forming a lens module over the source and the detector; and

(c) forming an optical isolator adapted to substantially prevent the internal propagation of radiation between the radiation source and the radiation detector within the sensor package, wherein forming comprises;

mounting or forming a baffle between the source and the detector, said baffle comprising opposed side surfaces and an upper edge extending between the opposed side surfaces, and forming one or more grooves in an upper surface of the lens module, the bottom-most part of at least one of the one or more grooves being adjacent said upper edge of the baffle.

25. The method of claim 24 wherein housing comprises bonding the source and the detector to a substantially planar attachment pad housed within the package.

26. The method of claim 25 wherein forming comprises bonding or forming the baffle on the attachment pad.

27. The method of claim 25 further comprising forming a well on the attachment pad before step (a) and wherein (a) housing the radiation source comprises mounting the radiation source at the bottom of the well.

28. The method of claim 24 comprising forming the lens module by encapsulating the source and the detector in a material which is transparent to radiation emitted by the source.

29. The method of claim 28 wherein the encapsulant material comprises silicone or epoxy.

30. The method of claim 24 wherein the source is a bare die light emitting diode.

31. The method of claim 24 wherein the lens module is formed as a single part.

32. The method of claim 24 wherein the lens module comprises a first lens positioned over the radiation source and a second lens positioned over the radiation detector.

33. The method of claim 24 further comprising covering selected portions of the lens module with material opaque to radiation emitted by the radiation source.

34. A mobile communications device comprising:

a proximity sensor comprising;

a sensor package comprising a lens module;

a radiation source and a radiation detector housed within the sensor package, the lens module of the sensor package being positioned over the source and the detector; and

an optical isolator adapted to substantially prevent the internal propagation of radiation between the source and the detector within the sensor package, the optical isolator comprising;

a baffle comprising opposed side surfaces and an upper edge extending between the opposed side surfaces; and

a groove formed in the upper surface of the lens module, the bottom-most part of the groove being adjacent said upper edge of the baffle.

35. A method of proximity detection comprising:

(a) providing a source and a detector within a single sensor package, the sensor package comprising a lens module positioned over the source and the detector;

(b) emitting radiation from the source;

(c) substantially preventing the internal propagation of radiation between the source and the detector within the sensor package using an optical isolator comprising;

a baffle including opposed side surfaces and an upper edge extending between the opposed side surfaces; and

a groove formed in the upper surface of the lens module, the bottom-most part of the groove being adjacent said upper edge of the baffle;

(d) illuminating an object outside the sensor package with a portion of the emitted radiation;

(e) detecting a portion of the emitted radiation reflected by the object; and

(f) processing the detected radiation to determine the proximity of the object to the sensor package.