PATENT DOCUMENT

Publication Number: US-8507863-B2
Application Number: US-201213350651-A
Country: US
Kind Code: B2

Title: Reflective proximity sensor with improved smudge resistance and reduced crosstalk

Abstract:
An electronic device includes a protective layer above a proximity sensor having a radiation emitter and a radiation detector. A groove, which may be wedge shaped, is formed in the bottom surface of the protective layer. A radiation barrier, which may be reflective or absorptive material, is placed in the groove in the bottom surface of the protective layer. A light blocking coating may be applied to the bottom surface and the groove of the protective layer to prevent the passage of visible radiation and permit the passage of infrared radiation. A radiation shield may be positioned between the emitter and the detector directly below the radiation barrier. Alignment features may be formed on the mating surfaces of the radiation barrier and radiation shield to align the protective layer with respect to the radiation shield and proximity sensor.

Claims:
What is claimed is: 
     
       1. An electronic device comprising:
 a proximity sensor having a radiation emitter and a radiation detector; 
 a protective layer positioned above the proximity sensor, the protective layer having a top surface and a bottom surface adjacent the proximity sensor; 
 a groove formed in the bottom surface of the protective layer; and 
 a radiation barrier in the groove in the bottom surface of the protective layer. 
 
     
     
       2. The device of  claim 1  wherein the groove formed in the bottom surface of the protective layer is wedge shaped. 
     
     
       3. The device of  claim 1  wherein the radiation barrier in the groove in the bottom surface of the protective layer is a reflective material. 
     
     
       4. The device of  claim 1  wherein the radiation barrier in the groove in the bottom surface of the protective layer is an absorptive material. 
     
     
       5. The device of  claim 1  wherein the radiation emitter and the radiation detector are both directed toward the top surface of the protective layer. 
     
     
       6. The device of  claim 1  further comprising a light blocking coating applied to the bottom surface of the protective layer to prevent the passage of visible radiation and permit the passage of infrared radiation. 
     
     
       7. The device of  claim 6  wherein the light blocking coating is further applied to the groove between the protective layer and the radiation barrier in the groove. 
     
     
       8. The device of  claim 1  further comprising a radiation shield positioned between the emitter and the detector of the proximity sensor and directly below the radiation barrier, and having a top surface adjacent to the bottom surface of the protective layer. 
     
     
       9. The device of  claim 8  wherein:
 the radiation barrier has a top surface adjacent to the protective layer and a bottom surface in which a first alignment feature is formed; and 
 the radiation shield has a second alignment feature formed in the top surface, the second alignment feature engaging the first alignment feature in the bottom surface of the radiation barrier to align the protective layer with respect to the radiation shield. 
 
     
     
       10. The device of  claim 8  wherein the radiation barrier is aligned with respect to the proximity sensor and the second alignment feature engaging the first alignment feature in the bottom surface of the radiation barrier further aligns the protective layer with respect to the proximity sensor. 
     
     
       11. A method of improving smudge resistance and reducing crosstalk in a reflective proximity sensor, the method comprising:
 positioning a protective layer above a proximity sensor having a radiation emitter and a radiation detector directed toward the protective layer, the protective layer having a top surface and a bottom surface adjacent the proximity sensor; 
 forming a groove in the bottom surface of the protective layer; and 
 placing a radiation barrier in the groove in the bottom surface of the protective layer. 
 
     
     
       12. The method of  claim 11  wherein the radiation barrier is a reflective material. 
     
     
       13. The method of  claim 11  wherein the radiation barrier is an absorptive material. 
     
     
       14. The method of  claim 11  further comprising applying a light blocking coating to the bottom surface of the protective layer to prevent the passage of visible radiation and permit the passage of infrared radiation. 
     
     
       15. The method of  claim 14  further comprising applying the light blocking coating to the groove between the protective layer and the radiation barrier in the groove. 
     
     
       16. The method of  claim 11  further comprising positioning a radiation shield between the emitter and the detector of the proximity sensor and directly below the radiation barrier, with a top surface of the radiation shield adjacent to the bottom surface of the protective layer. 
     
     
       17. The method of  claim 16  further comprising:
 forming a first alignment feature in a bottom surface of the radiation barrier; 
 forming a second alignment feature in the top surface of the radiation shield; and 
 aligning the protective layer with respect to the radiation shield by engaging the first alignment feature with the second alignment feature. 
 
     
     
       18. The method of  claim 17  further comprising aligning the protective layer with respect to the proximity sensor by engaging the first alignment feature with the second alignment feature. 
     
     
       19. An apparatus for improving smudge resistance and reducing crosstalk in a reflective proximity sensor, the apparatus comprising:
 a protective layer positioned above a proximity sensor having a radiation emitter and a radiation detector directed toward the protective layer, the protective layer having a top surface and a bottom surface adjacent the proximity sensor; and 
 first means for blocking radiation placed in a groove in the bottom surface of the protective layer directly above the means for blocking radiation positioned between the emitter and the detector of the proximity sensor. 
 
     
     
       20. The apparatus of  claim 19  further comprising means for preventing the passage of visible radiation and permitting the passage of infrared radiation applied to the bottom surface of the protective layer. 
     
     
       21. The apparatus of  claim 20  further comprising the means for preventing the passage of visible radiation and permitting the passage of infrared radiation applied to the groove between the protective layer and the first means for blocking radiation. 
     
     
       22. The apparatus of  claim 19  further comprising second means for blocking radiation positioned between the emitter and the detector of the proximity sensor, directly below the first means for blocking radiation, and adjacent to the bottom surface of the protective layer. 
     
     
       23. The apparatus of  claim 22  further comprising means for aligning the protective layer with respect to the means for blocking radiation positioned between the emitter and the detector of the proximity sensor. 
     
     
       24. The apparatus of  claim 19  further comprising means for aligning the protective layer with respect to the proximity sensor.

Description:
BACKGROUND 
     1. Field 
     Embodiments of the invention relate to the field of proximity sensors; and more specifically, to proximity sensor arrangements having a protective layer above the sensor to improve resistance to smudges on the protective layer and to reduce crosstalk between the emitter and detector due to the protective layer. 
     2. Background 
     Proximity sensors are used to sense hover events in a wide variety of devices including laptop computers, tablet computers, and smart phones. Hover events are no touch, close proximity positioning of parts of the user&#39;s body or other objects (e.g., a stylus held by the user), near or on an external surface of the device. It will be appreciated that “no touch” indicates that the sensor is not touched and that the external surface of the device may or may not be touched. 
     Typically such proximity sensors are designed to detect an external object that is located outside the near field detection capability of a touch sensor (e.g., those used in a typical touch screen display such as found in an iPhone™ device by Apple Inc.). In one instance, the proximity sensor includes an infrared emitter and a counterpart infrared detector that are controlled and sampled by proximity sensor circuitry integrated in the housing of the mobile device. Emitted infrared radiation may be scattered and/or directed toward the detector by the external object. Infrared radiation is detected and analyzed to infer that an external object is (or is not) close to the exterior surface. Because the detector receives emitted radiation that is reflected by the external object, such sensors may be referred to as reflective proximity sensors. 
     In the case of handheld mobile communications devices, the sensor may be located near an acoustic aperture for an earpiece speaker (receiver) of a mobile communications handset. This arrangement is used to determine when the handset is being held close to the user&#39;s ear, as opposed to away from the ear. When the proximity sensor indicates that the external object, in this case, the user&#39;s ear or head, is sufficiently close, then a predetermined action is taken, including, for example, turning off or disabling a touch screen display that is on the same external face of the housing as the acoustic aperture. This, of course, is designed to avoid unintended touch events caused by the user&#39;s cheek, while the handset is held close to the user&#39;s ear during a call. 
     The external surface of the device typically provides a protective layer above the proximity sensor and its associated electronics. The protective layer is made of materials that allow electromagnetic radiation of the wavelengths detected by the detector to pass through the protective layer. However, the protective layer itself will scatter and/or direct emitted infrared radiation toward the detector and interfere with detection of an external object. Smudges and dirt on the exterior surface can aggravate this interference. 
     It would be desirable to provide an exterior surface that provides a protective layer over a reflective proximity sensor in a way that reduces the effect of reflections and scattering from the protective layer and provides improved smudge resistance and reduced crosstalk between the emitter and the detector in the absence of an external object. 
     SUMMARY 
     An electronic device includes a protective layer above a proximity sensor having a radiation emitter and a radiation detector. A radiation shield is positioned between the emitter and the detector and extends to the bottom surface of the protective layer. A groove, which may be wedge shaped, is formed in the bottom surface of the protective layer directly above the top surface of the radiation shield. A radiation barrier, which may be reflective or absorptive material, is placed in the groove in the bottom surface of the protective layer. A light blocking coating may be applied to the bottom surface and the groove of the protective layer to prevent the passage of visible radiation and permit the passage of infrared radiation. Alignment features may be formed on the mating surfaces of the radiation barrier and radiation shield to align the protective layer with respect to the radiation shield and proximity sensor. A radiation absorber, which is a separate piece and of a separate material than the shield, may be positioned to provide a radiation seal between the top surface of the radiation shield and the bottom surface of the radiation barrier. 
     The structure of the radiation shield and the radiation barrier may help prevent stray radiation from the emitter that may have been internally reflected within the protective layer, from impinging on the detector. This internally reflected stray radiation (which is attenuated by the absorber) may be caused by original radiation from the emitter that has been internally reflected from oily build-up and residue, also referred to here as smudge, that has formed on the exterior surface of the protective layer due to normal use of the device. As a result, a more accurate proximity sensor may be obtained. 
     The above summary does not include an exhaustive list of all aspects of the present invention. It is contemplated that the invention includes all systems and methods that can be practiced from all suitable combinations of the various aspects summarized above, as well as those disclosed in the Detailed Description below and particularly pointed out in the claims filed with the application. Such combinations have particular advantages not specifically recited in the above summary. Other features and advantages of the present invention will be apparent from the accompanying drawings and from the detailed description that follows below. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The embodiments of the invention are illustrated by way of example and not by way of limitation in the figures of the accompanying drawings in which like references indicate similar elements. It should be noted that references to “an” or “one” embodiment of the invention in this disclosure are not necessarily to the same embodiment, and they mean at least one. 
         FIG. 1  is a cross-section view of a portion of an electronic device that embodies the invention. 
         FIG. 2  is a cross-section view of a portion of a second electronic device that embodies the invention. 
         FIG. 3  is a cross-section view of a portion of a third electronic device that embodies the invention. 
         FIG. 4  is a cross-section view of a portion of a fourth electronic device that embodies the invention. 
         FIG. 5  is a cross-section view of a portion of a fifth electronic device that embodies the invention. 
         FIG. 6  is a cross-section view of a portion of a sixth electronic device that embodies the invention. 
     
    
    
     DETAILED DESCRIPTION 
     Several embodiments of the invention with reference to the appended drawings are now explained. Whenever the shapes, relative positions and other aspects of the parts described in the embodiments are not clearly defined, the scope of the invention is not limited only to the parts shown, which are meant merely for the purpose of illustration. Also, while numerous details are set forth, it is understood that some embodiments of the invention may be practiced without these details. In other instances, well known circuits, structures, and techniques have not been shown in detail so as not to obscure the understanding of this description. 
       FIG. 1  is a cross-section view of a portion of an electronic device that embodies the invention. The device includes a proximity sensor having a radiation emitter  100  and a radiation detector  102 . The radiation emitter  100  and the radiation detector  102  may be mounted to a printed circuit board  128  or similar substrate and connected thereby to sensor circuitry  126  that controls the emitter and detector and determines the presence or absence of an external object based on the signals received. 
     A protective layer  104  is positioned above the proximity sensor. The protective layer has a top surface  106  and a bottom surface  108  adjacent the proximity sensor. The radiation emitter  100  and the radiation detector  102  are both directed toward the top surface  106  of the protective layer  104 . A radiation shield  110  may be positioned between the emitter  100  and the detector  102  of the proximity sensor. A top surface  112  of the radiation shield  110  may be adjacent to the bottom surface  108  of the protective layer  104 . 
     The proximity sensor includes the radiation emitter  100 , which emits the radiation, such as infrared (IR) radiation or a laser light, and the counterpart detector  102 , which is designed to detect impinging radiation. The emitter  100  and the detector  102  have their sensitive surfaces aimed at the protective layer  104 , either directly or indirectly (e.g., through a prism or mirror arrangement). Both the emitter  100  and the detector  102  are controlled and/or sensed electrically by proximity sensor circuitry  126 . This combination of the emitter, detector and proximity sensor circuitry may be a conventional, microelectronic infrared or laser proximity sensor unit, e.g. an IR or laser light emitting diode (LED)-based unit with a built-in light collector (lens), analog to digital conversion circuitry, and a digital communication interface to a processor (not shown). The detector may be part of a shared microelectronic device that can also be used to detect in other radiation bands, e.g. visible light. The data processor may be running proximity software that analyzes readings or samples from the proximity sensor circuitry  126 , based on what has been emitted and what has been detected (as scattered or reflected radiation from the external object). The proximity software may then make a determination as to whether the external object is close, far, or in between. 
     A groove  114  formed in the bottom surface  108  of the protective layer  104  between the emitter  100  and the detector  102 . A radiation barrier  116  is placed in the groove  114  in the bottom surface  108  of the protective layer  104 . The radiation barrier  116  is located between the radiation emitter  100  and the radiation detector  102  such that the barrier blocks a substantial portion of the optical path for internal reflections in the protective layer  104 . The dashed lines in the figure suggest an optical path for internal reflections in the protective layer  104  that is blocked by the radiation barrier  116 . The groove  114  may be wedge shaped as in the embodiment illustrated. The groove may be other shapes such as semi-circular, rectangular, trapezoidal, or other shapes that provide on opening in the bottom surface of the protective layer to receive a radiation barrier. The radiation barrier  116  may be a reflective material or an absorptive material with respect to the electromagnetic radiation produced by the radiation emitter  100 . In one embodiment, the radiation barrier  116  is an absorptive material that has the following characteristics in an infrared band 700 nm to 1,100 nm: transmittance less than five percent (5%), and reflectance less than ten percent (10%). 
     A light blocking coating  118  may be applied to the bottom surface  108  of the protective layer  104  to prevent the passage of visible radiation and permit the passage of infrared radiation when the radiation emitter  100  emits infrared radiation. The light blocking coating  118  may also be applied to the groove  114  between the protective layer  104  and the radiation barrier  116  in the groove. The light blocking coating  118  may provide an aesthetic appearance for the protective layer  104 . 
     Exemplary rays  120 ,  130  are shown as being emitted by the radiation emitter  100  to illustrate the operation of the radiation barrier  116  to reduce cross talk between the radiation emitter and the radiation detector  102 . The first ray  120  is shown striking an external object  124  and creating a reflected ray  122  that strikes the radiation detector  102 . 
     The similarly directed second ray  130  is shown striking the top surface  106  of the protective layer  104  and being reflected by the process of internal reflection because of the higher index of refraction for the protective layer than the surrounding air. As can be seen, the reflected ray  132  from the top surface  106  strike the radiation barrier  116  in the groove  114  and are prevented from reaching the radiation detector  102 . The dashed extension  134  of the second ray suggests how the ray would be reflected two more time and then strike the radiation detector  102 . 
     It will be appreciated that the illustrated rays are simplified for purposes of explanation and that both the first  120  and the second  130  rays will have transmitted portions that strike the external object  124  and reflected portions that strike the radiation barrier  116 . It will be further appreciated that there may be paths where radiation emitted by the radiation emitter  100  is reflected by the top surface  106  of the protective layer  104  and then strikes the radiation detector  102  despite the presence of the radiation barrier  116 . 
     It will be further appreciated that the geometry illustrated is not to scale or proportion and that the elements of the device can be laid out in a variety of relationships which can affect the amount of cross talk reduction provided. In a typical device the distance between the radiation emitter  100  and the radiation detector  102  is about one to five millimeters. The protective layer  104  may be a glass layer. The desirable that the groove  114  and the radiation barrier  116  be a substantial portion of the thickness of the protective layer  104  and the strength of the grooved protective layer may determine the depth of the groove and the radiation barrier. It may be desirable to use a material for the radiation barrier, such as an epoxy, that also has properties that reinforce the protective layer along the groove. 
       FIG. 2  is a cross-section view of a portion of a second electronic device that embodies the invention. In this embodiment the radiation barrier  216  has a top surface adjacent to the protective layer  104  and a bottom surface in which a first alignment feature  218  is formed. The radiation shield  210  has a second alignment feature  214  formed in the top surface  212 . The second alignment feature  214  engages the first alignment feature  218  in the bottom surface of the radiation barrier  216  to align the protective layer  104  with respect to the radiation shield  210 . In some embodiments the radiation barrier  210  is aligned with respect to the proximity sensor  100 ,  102  and the second alignment feature  214  engaging the first alignment feature  218  in the bottom surface of the radiation barrier  216  further aligns the protective layer  104  with respect to the proximity sensor. 
       FIG. 3  is a cross-section view of a portion of a third electronic device that embodies the invention. In this embodiment the radiation shield has a two part construction, with a top portion  320  being formed of a different material than the lower portion  310 . For example, the top portion  320  may be resilient while the lower portion  310  is rigid. The top portion  320  of the radiation shield may have greater infrared absorption characteristics than the lower portion  310 . which may need to achieve other purposes (such as strength and low cost) that might sacrifice its radiation absorption characteristics. The top portion  320  of the radiation shield may include a lower alignment feature  324  that engages a corresponding alignment feature on the lower portion and an upper alignment feature  322  that engages a corresponding alignment feature on the radiation barrier  216 . These alignment features  322 ,  324  align the protective layer  104  with respect to the radiation shield  310  and, in some embodiments, further with respect to the proximity sensor. 
       FIG. 4  is a cross-section view of a portion of a fourth electronic device that embodies the invention. In this embodiment the groove  414  in the protective layer  104  and the radiation barrier  416  that fills the groove have a rounded cross-section. The light blocking coating  418  is applied to the bottom surface of the protective layer  104  but is not applied to the groove  414  between the protective layer  404  and the radiation barrier  416  in the groove. 
     The radiation barrier  416  has a bottom surface in which a first alignment feature  422  is formed. The radiation shield  410  has a second alignment feature  424  formed in the top surface. The second alignment feature  424  engages the first alignment feature  422  to align the protective layer  404  with respect to the radiation shield  410  and, in some embodiments, further with respect to the proximity sensor. As suggested by the figure, the alignment features  422 ,  424  may have rectangular cross-sections and they may not be tightly engaged. Further, there may be some space between the top of the radiation shield  410  and the bottom of the protective layer  404  and the radiation barrier  416 . The alignment features provide a labyrinth radiation seal and a tight mechanical seal is not required. 
     As shown in  FIG. 4 , some devices may include lenses  430 ,  432  between the protective layer  404  and one or both of the radiation emitter  100  and the radiation detector  102  to further improve the operational characteristics of the proximity sensor. 
       FIG. 5  is a cross-section view of a portion of a fifth electronic device that embodies the invention. In this embodiment no radiation shield is provided between a radiation barrier  516  that fills a groove in the protective layer  504  and a printed circuit board  528 . A light blocking coating  518  is applied to the bottom surface of the protective layer  504  as in previously described embodiments. A radiation emitter  500  and a radiation detector  502  are mounted in reflective cups  540 ,  542  that collimate the radiation. The radiation barrier  516  is located between the radiation emitter  500  and the radiation detector  502  such that the barrier blocks a substantial portion of the optical path for internal reflections in the protective layer  504 . 
       FIG. 6  is a cross-section view of a portion of a sixth electronic device that embodies the invention. In this embodiment a radiation barrier  616  that fills a groove in the protective layer  604  extends below the protective layer to provide a radiation shield that extends towards a printed circuit board  628 . A light blocking coating  618  is applied to the bottom surface of the protective layer  604  as in previously described embodiments. A radiation emitter  600  and a radiation detector  602  are mounted in reflective cups  640 ,  642  that collimate the radiation. Lenses  630 ,  632  are provided between the radiation emitter  600  and the protective layer  604  and also between the radiation detector  602  and the protective layer to further collimate the radiation. 
     While certain embodiments have been described and shown in the accompanying drawings, it is to be understood that such embodiments are merely illustrative of and not restrictive on the broad invention, and that the invention is not limited to the specific constructions and arrangements shown and described, since various other modifications may occur to those of ordinary skill in the art. For example, while the drawings depict different layers being in contact with each other (e.g., in  FIG. 1 , layer  118  is in contact with the bottom of layer  104 , and the radiation barrier  116  is in contact with the layer  118 ), this does not preclude an additional or intermediate layer between them so long as the purposes of the radiation barrier, including that of attenuating the stray internal reflections within the layer  104 , are not thwarted. Optical arrangements for the emitter shown in one embodiment may be combined with optical arrangements shown for the detector in another embodiment. The radiation barrier shown in one embodiment may be combined with a radiation shield in another embodiment or used without a radiation shield. The arrangement of radiation barriers and radiation shields shown in one embodiment may be used with optical arrangements of the emitter and detector shown in other embodiments. The description is thus to be regarded as illustrative instead of limiting.

Metadata:
Filing Date: 20120113
Publication Date: 20130813
Grant Date: 20130813
Priority Date: 20120113
Inventors: HOLENARSIPUR PRASHANTH
Assignee: APPLE INC
CPC Classifications: [{"code": "G06F1/1684", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F1/1684", "inventive": true, "first": true, "tree": "[]"}, {"code": "G01S17/04", "inventive": true, "first": true, "tree": "[]"}, {"code": "G06F1/182", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/041", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F2203/04101", "inventive": false, "first": false, "tree": "[]"}, {"code": "G01S17/04", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F1/182", "inventive": true, "first": false, "tree": "[]"}, {"code": "G01S7/4811", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F2203/04101", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F1/1694", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F1/1694", "inventive": true, "first": false, "tree": "[]"}, {"code": "G01S7/4811", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/0421", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 48779337