PROXIMITY SENSOR, PARTICULARLY FOR MOBILE DEVICES LIKE SMARTPHONES, TABLETS OR THE LIKE

Abstract

Embodiments relate to a proximity sensor, particularly for mobile devices like smartphones, tablets or the like. The proximity detector includes a first emitter-detector pair with a first light emitter and a first photodetector, wherein the first light emitter and the first photodetector are separated by a first distance, and a second emitter-detector pair with a second light emitter and a second photodetector, wherein the second light emitter and the second photodetector are separated by a second distance, wherein the first distance is different from the second distance. Embodiments further relate to a method for detecting the proximity of a target to a proximity sensor.

Claims

1. A proximity sensor, particularly for mobile devices like smartphones, tablets or the like, comprising: a first emitter-detector pair with a first light emitter and a first photodetector, wherein the first light emitter and the first photodetector are separated by a first distance, and a second emitter-detector pair with a second light emitter and a second photodetector, wherein the second light emitter and the second photodetector are separated by a second distance, wherein the first distance is different from the second distance.

2. The proximity sensor according to claim 1, wherein the difference between the first distance and the second distance is defined by a factor of at least 1.25.

3. The proximity sensor according to claim 1, wherein the first emitter-detector pair and the second emitter-detector pair share a common light emitter or a common photodetector.

4. The proximity sensor according to claim 1, wherein the first emitter-detector pair and the second emitter-detector pair are arranged on a common substrate.

5. The proximity sensor according to claim 1, further comprising at least one angle limiter for the first light emitter and/or second light emitter.

6. The proximity sensor according to claim 1, further comprising at least one view limiter for the first photodetector and/or second photodetector.

7. The proximity sensor according to claim 1, wherein the first emitter-detector pair and the second emitter-detector pair are arranged collinearly.

8. The proximity sensor according to claim 1, further comprising an angular extent detector for detecting the target angular extent, wherein the angular extent detector is preferably a photodetector with at least two different fields of view.

9. The proximity sensor according to claim 1, wherein the proximity sensor comprises or is connected to or operably connectable to an integrated circuit, wherein the integrated circuit comprises one or more of the followings units: a driver unit for the first light emitter and/or second light emitter, an analog-to-digital converter, a reducer for producing an output signal or value which increases with the signal of the emitter-detector pair having the greater distance and which decreases with the signal of the emitter-detector pair having the smaller distance, a comparator comparing the output of the reducer with a threshold.

10. A method for detecting the proximity of a target to a proximity sensor comprising the steps of: sending and receiving a first light signal by a first emitter-detector pair of the proximity sensor with a first light emitter and a first photodetector, wherein the first light emitter and the first photodetector are separated by a first distance, sending and receiving a second light signal by a second emitter-detector pair of the proximity sensor with a second light emitter and a second photodetector, wherein the second light emitter and the second photodetector are separated by a second distance, and wherein the first distance is different from the second distance, subtracting the signal of the emitter-detector pair having the smaller distance from the signal of the emitter-detector pair having the greater distance.

11. A method according to claim 10, further comprising the step of scaling the signal of the emitter-detector pair having the smaller distance before the step of subtracting.

12. A method according to claim 10, wherein the first light signal and the second light signal is send by the same light emitter or received by the same photodetector.

13. A method according to claim 10, comprising the step of directing the first light signal and/or second light signal and/or the step of adjusting the viewing angle of the first photodetector and/or second photodetector.

14. A method according to claim 10, comprising the step of detecting the target angular extent, preferably by a photodetector with at least two different fields of view.

15. A method for detecting the proximity of a target to a proximity sensor using the proximity sensor according to claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0045] In the following, the invention will be further explained with respect to the embodiments shown in the figures. It shows:

[0046] FIG. 1 illustrates a schematic top view of a first embodiment of a proximity sensor according to the invention.

[0047] FIG. 2 illustrates a schematic side view of a second embodiment of a proximity sensor according to the invention.

[0048] FIG. 3 illustrates a schematic side view of a third embodiment of a proximity sensor according to the invention.

[0049] FIG. 4 illustrates a schematic side view of a fourth embodiment of a proximity sensor according to the invention.

[0050] FIG. 5 illustrates a schematic side view of a fifth embodiment of a proximity sensor according to the invention.

[0051] FIG. 6 illustrates a schematic side view of a sixth embodiment of a proximity sensor according to the invention.

[0052] FIG. 7 illustrates use of the proximity sensor of FIG. 3 in a mobile device.

DETAILED DESCRIPTION

[0053] FIG. 1 shows a schematic top view of a first embodiment of a proximity sensor 1, particularly for mobile devices like smartphones, tablets or the like. The proximity sensor comprises a first emitter-detector pair 2, surrounded by a dashed line in FIG. 1. The first emitter-detector pair 2 comprises a first light emitter 3 and a first photodetector 4. The first light emitter 3 and the first photodetector 4 are separated by a first distance 5, indicated in FIG. 1 by a double arrow line.

[0054] The proximity sensor 1 further comprises a second emitter-detector pair 6, surrounded by a dotted line in FIG. 1. The second emitter-detector pair 6 comprises a second light emitter 7 and a second photodetector 8. According to the embodiment shown in FIG. 1 the first emitter-detector pair 2 and the second emitter-detector pair 6 share a common photodetector 4, 8, i.e. the first photodetector 4 is built integrally with the second photodetector 8 by the common photodetector 4, 8. The second light emitter 7 and the second photodetector 8 are separated by a second distance 9, indicated in FIG. 1 also by a double arrow line.

[0055] According to the invention the first distance 5 is different from the second distance 9. Preferably the difference between the first distance 5 and the second distance 9 is defined by a factor of at least 1.25. Pursuant to the embodiment shown in FIG. 1 the difference between the first distance 5 and the second distance 9 is defined by a factor of about 1.5., i.e. the second distance 9 is about 50% longer than the first distance 5.

[0056] The first light emitter 3 and the second light emitter 7 emit light in the infrared spectrum and the common photodetector 4, 8 is adapted to receive light in the infrared spectrum.

[0057] The first emitter-detector pair 2 and the second emitter-detector pair 6 are arranged on a common substrate 10. Preferably the first emitter-detector pair 2 and the second emitter-detector pair 6 are arranged colinearly on the common substrate 10.

[0058] The proximity sensor 1 is used to detect the proximity of a target 20 to the proximity sensor 1. If the proximity sensor 1 detects the proximity of the target 20, the display and/or touch sensor of the mobile device containing the proximity sensor 1 can be switched off. This is particularly useful in case a user holds the mobile device to his head during a phone call, so that for example no touch signals are generated during the call due to the proximity of the mobile device to the head of the user.

[0059] FIG. 2 shows a schematic side view of a second embodiment of a proximity sensor 1 according to the invention. The proximity sensor 1 of FIG. 2 comprises a first emitter-detector pair 2 with a first light emitter 3 and a first photodetector 4 and a second emitter-detector pair 6 with a second light emitter 7 and a second photodetector 8. Like in the embodiment of FIG. 1 the first photodetector 4 and the second photodetector 8 are built integrally by a common photodetector 4, 8.

[0060] The first light emitter 3 is arranged at a first distance 5 from the common photodetector 4, 8 and the second light emitter 7 is arranged at a second distance 9 from the common photodetector 4, 8 as indicated by the two double arrow lines in FIG. 2. The difference between the first distance 5 and the second distance is about 1.5, like in the first embodiment of FIG. 1.

[0061] The first and second light emitter 3, 7 and the common photodetector 4, 8 preferably operate in the infrared light spectrum.

[0062] The first emitter-detector pair 2 and the second emitter-detector pair 6 are arranged colinearly on a common substrate 10, as shown in FIG. 2.

[0063] The proximity sensor 1 of the second embodiment shown in FIG. 2 further comprises an angle limiter 11 for the first light emitter 3 and an angle limiter 11 for the second light emitter 3. The angle limiter 11 limits the direction of the light emitted by the first light emitter 3 respectively of the light emitted from the second light emitter 7. The light emitters 11 of FIG. 2 comprise a barrier between both light emitters 3, 7 and further define an aperture for each light emitter 3, 7, wherein the aperture is located above the respective light emitter 3, 7. Alternatively or additionally the angle limiter 11 could comprise a lens or a collimated source, i.e. collimated light emitter 3, 7.

[0064] The proximity sensor 1 of the second embodiment shown in FIG. 2 further comprises a view limiter 12 for the common photodetector 4, 8. The view limiter 12 limits the direction from which the photodetector 4, 8 can receive light signals 21. The view limiter 12 shown in FIG. 2 comprises a barrier around the common photodetector 4, 8 and defining an aperture above the common photodetector 4, 8. Alternatively or additionally the view limiter 12 could comprise a lens or a collimated detector, i.e. collimated photodetector 4, 8.

[0065] FIG. 3 shows a third embodiment of a proximity sensor 1 in a schematic side view. The proximity sensor 1 of FIG. 3 comprises a first emitter-detector pair 2 with a first light emitter 3 and a first photodetector 4. The first light emitter is separated from the first photodetector 4 by a first distance 5. The proximity sensor 1 further comprises a second emitter-detector pair 6 with a second light emitter 7 and a second photodetector 8, wherein the first photodetector 4 and the second photodetector 8 are built integrally by a common photodetector 4, 8. The second light emitter 7 is separated from the second photodetector 8 by a second distance 9. The difference between the second distance 9 and the first distance 5 is defined by a factor of about 2,0.

[0066] As described with respect to the second embodiment of FIG. 2 the third embodiment of FIG. 3 also comprises angle limiter 11 for the first light emitter 3 and the second light emitter 7 and a view limiter 12 for the photodetector 4, 8.

[0067] The third embodiment of FIG. 3 differs from the second embodiment of FIG. 2 in that the first light emitter 3 and the second light emitter 7 are arranged on different sides of the common photodetector 4, 8, whereas in the second embodiment of FIG. 2 the first light emitter 3 and the second light emitter 7 are arranged on the same side of the common photodetector 4, 8. In both embodiment the first emitter-detector pair 2 and the second emitter-detector pair 6 are arrange colinearly on a common substrate 10.

[0068] In FIG. 4 a fourth embodiment of a proximity sensor 1 according to the invention is shown in a schematic side view. The proximity sensor 1 comprises a first emitter-detector pair 2 comprising a first light emitter 3 and a first photodetector 4, separated by a first distance 5 and a second emitter-detector pair 6 comprising a second light emitter 7 and a second photodetector 8, separated by a second distance 9. In this embodiment the first light emitter 3 is built integrally with the second light emitter 7 by a common light emitter 3, 7. The first photodetector 4 and the second photodetector 8 are arranged on opposite sides of the common light emitter 3, 7. However, it also possible that the first photodetector 4 and the second photodetector 8 are arranged on the same side of the common light emitter 3, 7.

[0069] The first emitter-detector pair 2 and the second emitter-detector pair 6 are arranged colinearly on a common substrate 10 and the difference between the second distance 9 and the first distance 5 is about 2.0.

[0070] According to the fourth embodiment of FIG. 4 the proximity sensor 1 comprises a view limiter 12 for the first photodetector 4 and the second photodetector 8 and an angle limiter for the common light emitter 3, 7.

[0071] FIG. 5 shows a schematic side view of a fifth embodiment of a proximity sensor 1 according to the invention. The proximity sensor of FIG. 5 corresponds to the proximity sensor 1 of FIG. 2 and further comprises an angular extent detector 13 for detecting the target angular extent of a target 20 in the proximity of the proximity sensor 1. The angular extent detector 13 is integrated into the common photodetector 4, 8 and has two different field of views 14. As the target 20 get closer to the proximity sensor 1 the target angular extent increases. At the beginning the target is only within one field of view 14 but as the target 20 gets closer to the proximity sensor 1 the target angular extent increases and at one point the target 20 is within both fields of view 20. The angular extent detector 13 solves the problem of the so-called zero distance problem. The zero distance problem relates to the fact that the emitter-detector pair 2 ,6 having the greater distance 5, 9 does not create a signal in case the target is very close to the proximity sensor 1. If the angular extent detector 13 detects a very close target 20 a proximity event can be created irrespective of the signal of the emitter-detector pair 2, 6 having the greater distance 5, 9. The proximity sensor 1 can comprise a compensator (not shown) which monitors the signals of angular extent detector 13 and compensates the zero distance effect by generating a proximity signal as explained above.

[0072] The sixth embodiment of the invention shown in FIG. 6 differs from the embodiment of FIG. 5 in that the angular extent detector 13 comprises three different fields of view 14. According to the fifth embodiment of FIG. 5 the different fields of view 14 do not overlap, whereas according to the sixth embodiment of FIG. 6 the different fields of view 14 partially overlap.

[0073] FIG. 7 shows the use of the proximity sensor 1 in a mobile device. The proximity sensor 1 is mounted below a cover glass 24 of the mobile device. In FIG. 7 only the proximity sensor 1 and the cover glass 24 are shown. The details of the proximity sensor 1 have been explained above with respect to FIG. 3.

[0074] First, a light signal 21 is emitted by the light emitter 3 of the first emitter-detector pair 2 towards the cover glass 24 of the mobile device. A part of this emitted light signal 21 is scattered and/or reflected by the cover glass 24 towards the common photodetector 4, 8. This reflected light signal 22 is shown in FIG. 7 by a dotted line and represents the crosstalk. The crosstalk depends on the characteristics of the cover glass24, coating on the cover glass 24, the distance of the cover glass 24 to the proximity sensor 1, smudge on the cover glass 24, a possible bending of the cover glass 24 or substrate 10 of the proximity sensor 1 and so on. Thus, the crosstalk comprises static and dynamic parts.

[0075] A part of the emitted light signal 21 strikes the target 20 is and reflected back to the common photodetector 4, 8. This part of the light signal 23 is shown in FIG. 7 by a dashed line. The overall received light signal at the photodetector 4, 8 consists of the crosstalk light signal 22 and the target light signal 23.

[0076] To subtract the crosstalk from the received light signal a second light signal 21 is emitted from the second light emitter 7 of the second emitter-detector pair 6. Again, a part of this emitted light signal 21 is reflected and/or scattered by the cover glass 24 towards the photodetector 4, 8 as crosstalk (shown by dotted line 22 in FIG. 7). A part of the emitted light signal 21 strikes the target 20 and is reflected back towards the photodetector 4, 8, as shown by the dashed line 23 in FIG. 7.

[0077] It has been found out, that the received signal of the emitter-detector pair 6 having the smaller distance 9 between the light emitter 7 and the photodetector 4, 8 mainly consist of crosstalk signal 22. Thus, by subtracting the signal of this emitter-detector pair 6 from the signal of the other emitter-detector pair 2 the current crosstalk is eliminated.

[0078] To reflect the actual conditions of the proximity sensor 1 in the mobile device and the current dimension the signal of the emitter-detector pair 6 having the smaller distance 9 can be scaled before being subtracted from the signal of the emitter-detector pair 2 having the greater distance 5.

[0079] According to the embodiment of FIG. 7 the light signals of the first emitter-detector pair 2 and of the second emitter-detector pair 6 are received by a common photodetector 4, 8. Alternatively, two photodetectors 4, 8 and a common light emitter 3, 7 can be used or even two photodetectors 4, 8 and two light emitters 3, 7.

[0080] The sending of the light signal 21 by the first emitter-detector pair 2 and of the second emitter-detector pair 6 takes place successively, to avoid any crosstalk between the light signals 21 of the emitter-detector-pairs 2, 6.

[0081] Advantageously the subtracting is performed internally by the proximity sensor 1, for example by analog or digital math. This increases the efficiency of the proximity sensor 1 because no external microcontroller is involved, which at least adds some power consumption and cost.

[0082] The light signal 21 is preferably an infrared light signal 12 having a wavelength between about 800 nm to about 1 mm.

[0083] The light signals 21 emitted by the first emitter-detector pair 2 and of the second emitter-detector pair 6 is directed by an angle limiter 11 of the proximity sensor 1, to define an area that is monitored by the proximity sensor 1. Further, the crosstalk light signals 22 and target light signals 23 are directed by the view limiter 12 of the proximity sensor 1.