PROXIMITY SENSORS AND METHODS FOR SENSING PROXIMITY

• US 20090121889A1
• Filed: 04/10/2008
• Published: 05/14/2009
• Est. Priority Date: 11/14/2007
• Status: Active Grant

• Current Assignee: Intersil Americas LLC (Renesas Electronics Corporation)
• Original Assignee: Intersil Americas LLC (Renesas Electronics Corporation)
• Inventors: Benzel, Phillip J., Steciw, Oleg, Ng, Wendy, Lin, Xijian, Li, Zhong
• Granted Patent: US 7,907,061 B2
• Time in Patent Office: Days
• US Class Current: 340/686.600
• CPC Class Codes: G06F 1/3203 Power management, i.e. event-based initiation of a power-saving mode
• CPC Class Codes: G06F 1/3231 Monitoring the presence, absence or movement of users
• CPC Class Codes: Y02D 10/00 Energy efficient computing, e.g. low power processors, power management or thermal management

Abstract

In an embodiment, a proximity sensor includes a driver, a photo-diode (PD) and an analog-to-digital converter (ADC). The proximity sensor can also include a controller to control the driver. The driver selectively drives a light source, e.g., an infrared (IR) light emitting diode (LED). The PD, which produces a current signal indicative of the intensity of light detected by the PD, is capable of detecting both ambient light and light produced by the light source that is reflected off an object. The ADC receives one or more portion of the current signal produced by the PD. The ADC produces one or more digital output that can be used to estimate the proximity of an object to the PD in a manner that compensates for ambient light detected by the PD and transient changes to the detected ambient light.

Claims

1. A method for use in monitoring the proximity of an object, comprising:

(a) controlling a light source;

(b) during one or more time period, detecting an intensity of both ambient light and light produced by the light source that is reflected off the object;

(c) during one or more further time period while the light source is not producing light, detecting the intensity of the ambient light; and

(d) producing, based on the intensities detected at steps (b) and (c), an output indicative of the intensity of the detected light produced by the light source that is reflected off the object, and that compensates for the ambient light including transient changes thereto;

wherein the output can be used to estimate the proximity of the object.

2. The method of claim 1, wherein:

step (b) comprises detecting the intensity of both ambient light and light produced by the light source that is reflected off the object during a first plurality of time periods; and

step (c) comprise detecting the intensity of the ambient light during a second plurality of time periods;

at least some of the first plurality of time periods of step (b) are interspersed with at least some of the second plurality of time periods of step (c).

3. The method of claim 1, wherein step (d) comprises producing the output by subtracting one or more value indicative of the intensity detected at step (c) from one or more value indicative of the intensity detected at step (b).

4. The method of claim 3, wherein the subtracting can be a weighted subtracting.

6. The method of claim 1, wherein step (d) includes using a dual-input single output analog to digital converter (ADC) to produce the output that can be used to estimate the proximity of the object.

7. The method of claim 1, wherein:

step (a) includes, during the one or more time period, producing infrared (IR) light;

step (b) includes, during the one or more time period, detecting the intensity of both ambient light and the produced IR light that is reflected off the object; and

step (c) includes, during the one or more further period, detecting the intensity of the ambient light.

8. The method of claim 1, further comprising:

(e) comparing the output produced at step (d) to one or more threshold to estimate the proximity of the object.

9. The method of claim 1, wherein:

step (a) comprises selectively driving an infrared light emitting diode (IR LED); and

step (b) comprises detecting light at a photo-diode (PD);

wherein during the one or more time period of step (b), the intensity of the light detected by the PD is indicative of both ambient light and IR light produced by an IR LED that is reflected off the object; and

wherein during the one or more further time period of step (c), the intensity of the light detected by the PD is indicative of the intensity of the ambient light.

5. The method of 1, wherein step (d) includes:

increasing a count value of an up-down counter or an accumulator based on the intensity detected at step (b); and

decreasing a count value of the up-down counter or the accumulator based on the intensity detected at step (c);

wherein the output produced at step (d) is an output of the up-down counter or the accumulator.

10. A proximity sensor, comprising:

a driver to selectively drive a light source;

a photo-diode (PD) that produces a current signal indicative of the intensity of light detected by the PD, the PD capable of detecting ambient light and detecting light produced by the light source that is reflected off an object; and

an analog-to-digital converter (ADC) that receives one or more portion of the current signal produced by the PD;

wherein the ADC produces one or more digital output that can be used to estimate the proximity of an object to the PD in a manner that compensates for the ambient light detected by the PD and transient changes to the detected ambient light.

11. The proximity sensor of claim 10, wherein:

when the driver is driving the light source, the ADC produces one or more first digital value indicative of both the intensity of ambient light detected by the PD, and an intensity of the light produced by the light source that is reflected off an object and detected by the PD; and

when the driver is not driving the light source, the ADC produces one or more second digital value indicative of the intensity of the ambient light detected by the PD.

12. The proximity sensor of claim 11, wherein:

a difference between the first and second digital values is indicative of the intensity of the light produced by the light source that is reflected off the object and detected by the PD; and

the difference between the first and second digital values can be used to estimate the proximity of the object relative to the PD.

13. The proximity sensor of claim 10, wherein:

the ADC comprises a dual input single output ADC;

a first input of the ADC receives one or more portion of the current signal, produced by the PD, indicative of both the intensity of ambient light detected by the PD, and the intensity of the light produced by the light source that is reflected off an object and detected by the PD; and

a second input of the ADC receives one or more further portion of the current signal, produced by the PD, indicative of the intensity of the ambient light detected by the PD.

14. The proximity sensor of claim 13, wherein the dual input single output ADC includes:

a pair of integrators;

a pair of comparators; and

a 1-bit digital to analog converter (DAC) that produces three outputs including a first reference current that is provided to one of the integrators, a second reference current that is provided to the other one of the integrators, and a reference voltage that is provided to the comparators.

15. The proximity sensor of claim 13, wherein the dual input single output ADC includes up-down counter that selectively counts up or down, to thereby produce at the single output a digital value indicative of the intensity of the light produced by the light source that is reflected off the object and detected by the PD.

16. The proximity sensor of claim 10, further comprising:

a further ADC that receives one or more further portion of the current signal produced by the PD;

switches; and

a controller to control the driver and the switches;

wherein the controller controls the switches to direct portions of the current signal produced by the PD to either the ADC or the further ADC;

wherein the ADC produces one or more first digital value indicative of both an intensity of the ambient light detected by the PD, and an intensity of the light produced by the light source that is reflected off an object and detected by the PD; and

wherein the further ADC produces one or more second digital value indicative of the intensity of the ambient light detected by the PD.

17. The proximity sensor of claim 16, wherein:

a difference between the first and second digital values is indicative of the intensity of the light produced by the light source that is reflected off the object and detected by the PD; and

the difference between the first and second digital values can be used to estimate the proximity of the object relative to the PD.

18. The proximity sensor of claim 10, further comprising:

a controller to control the driver.

19. The proximity sensor of claim 18, wherein the proximity sensor comprises a monolithic chip that includes the driver, the controller, the PD and the ADC.

20. The proximity sensor of claim 19, wherein the monolithic chip includes:

a first terminal configured to be connected to a terminal of a light emitting diode or laser diode, so that the driver can selectively drive the light emitting diode or laser diode.

21. The proximity sensor of claim 20, wherein the monolithic chip further includes:

an output terminal configured to output an interleaved stream of first and second digital data values, wherein a difference between the first and second digital values can be used to estimate the proximity of the object relative to the PD.

22. The proximity sensor of claim 20, wherein the monolithic chip further includes:

an output terminal configured to output one or more digital data value that can be used to estimate the proximity of the object relative to the PD.

23. The proximity sensor of claim 20, wherein the monolithic chip further includes:

a first output terminal configured to output one or more first digital data value indicative of both the intensity of ambient light detected by the PD, and an intensity of the light produced by the light source that is reflected off an object and detected by the PD; and

a second output terminal configured to output one or more second digital data value indicative of the intensity of the ambient light detected by the PD;

wherein a difference between the first and second digital values is indicative of the intensity of the light produced by the light source that is reflected off the object and detected by the PD; and

wherein the difference between the first and second digital values can be used to estimate the proximity of the object relative to the PD.

24. A proximity sensor, comprising:

a driver to selectively drive a light source;

a photo-diode (PD) that produces a current signal indicative of an intensity of light detected by the PD;

an analog-to-digital converter (ADC) that includes a first input, a second input and an output;

a controller to control the driver and to control switches that direct portions of the current signal produced by the PD to either the first input or the second input of the ADC;

wherein the ADC includes up-down counter that selectively counts up or down, based on the portions of the current signal provided to the first and second inputs, to thereby produce a count value that is indicative of light produced by the light source that is reflected off an object and detected by the PD; and

wherein the count value, which is provided at the output of the ADC, can be used to estimate the proximity of an object to the PD.

25. A system, comprising:

a driver to selectively drive a light source;

a photo-diode (PD) that produces a current signal indicative of the intensity of light detected by the PD, the PD capable of detecting ambient light and detecting light produced by the light source that is reflected off an object; and

an analog-to-digital converter (ADC) that receives one or more portion of the current signal produced by the PD;

wherein the ADC produces one or more digital output indicative of the proximity of an object to the PD in a manner that compensates for the ambient light detected by the PD and transient changes to the detected ambient light;

a comparator or processor that receives the one or more digital output and enables or disables a subsystem based on the one or more digital signal indicative of the proximity of the object to the PD.