Method of detecting an object with a proximity sensor

• US 9,689,657 B2
• Filed: 08/03/2011
• Issued: 06/27/2017
• Est. Priority Date: 08/04/2010
• Status: Active Grant

• Current Assignee: Stmicroelectronics Rousset SAS (STMicroelectronics NV)
• Original Assignee: Stmicroelectronics Rousset SAS (STMicroelectronics NV)
• Inventors: Troise, Cyril, Teissier, Maxime
• Primary Examiner(s): Park, Hyun
• Assistant Examiner(s): Casey, Liam R
• Application Number:
  US13/197,619
• Publication Number:
  US 20120035883A1
• Time in Patent Office: 2,155 Days
• Field of Search: 327517
• CPC Class Codes: G01B 7/003 for measuring position, not involving coordinate determination coordinate measuring G01B7/004
• CPC Class Codes: G01B 7/14 for measuring distance or clearance between spaced objects or spaced apertures G01B7/30 takes precedence
• CPC Class Codes: G01V 3/088 operating with electric fields G01V3/082 takes precedence
• CPC Class Codes: H03K 17/945 Proximity switches H03K17/96 takes precedence
• CPC Class Codes: H03K 17/955 using a capacitive detector
• CPC Class Codes: H03K 2217/960705 Safety of capacitive touch and proximity switches, e.g. increasing reliability, fail-safe

Abstract

The disclosure relates to a method of detecting an object using a detection signal supplied by a proximity sensor. The method comprises the steps of generating a reference signal by filtering the value of the detection signal, defining a first detection threshold, and going from an object non-detecting state to an object detecting state when the value of the detection signal becomes greater than the first detection threshold. When the value of the detection signal becomes greater than the first detection threshold, the value of the reference signal is readjusted in a manner such that the value of the detection signal again becomes less than or respectively greater than, the first detection threshold.

Claims

1. A method, comprising:

detecting an object using a detection signal supplied by a proximity sensor, the detection signal having a value that changes as a function of the proximity of the object to the proximity sensor, the detecting including;

generating a reference signal by filtering the detection signal;

defining a first detection threshold relative to the reference signal;

going from an object non-detecting state to an object detecting state in response to detecting the detection signal crossing the first detection threshold in a first direction; and

in response to detecting the detection signal crossing the first detection threshold in the first direction, readjusting a value of the reference signal based on the detection signal and setting the first detection threshold based on the readjusted value of the reference signal such that the detection signal again crosses the first detection threshold in a second direction opposite to the first direction.

2. A method according to claim 1, comprising, while in the object detecting state:

detecting that the detection signal again crosses the first detection threshold in the first direction; and

again readjusting the value of the reference signal, in a manner such that the detection signal again crosses the first detection threshold in the second direction, in response to detecting that the detection signal again crosses the first detection threshold in the first direction.

3. A method according to claim 1, comprising:

defining a second detection threshold relative to the reference signal,

going from the object detecting state to the object non-detecting state in response to detecting that the detection signal crosses the second detection threshold in the second direction, and

in response to detecting that the detection signal crosses the second detection threshold in the second direction, readjusting the value of the reference signal in a manner such that the detection signal crosses the second detection threshold in the first direction.

4. A method according to claim 3, comprising, while in the object detecting state:

detecting that the detection signal again crosses the second detection threshold in the second direction; and

again readjusting the value of the reference signal, in a manner such that the detection signal again crosses the second detection threshold in the first direction, in response to detecting that the detection signal again crosses the second detection threshold in the second direction, without modifying the non-detecting state.

5. A method according to claim 3, wherein defining the second detection threshold includes adding or subtracting an offset to the value of the reference signal.

6. A method according to claim 1, wherein defining the first detection threshold includes adding or subtracting an offset value to the value of the reference signal.

7. A method according to claim 1, wherein readjusting the value of the reference signal is done in a manner such that the value of the detection signal is substantially equal to the value of the reference signal with a maximum deviation less than a difference between the value of the readjusted reference signal and the detection threshold, the crossing of which causes the readjusting of the reference signal.

8. A method according to claim 1, wherein the readjusting of the value of the reference signal is done from values of the detection signal after an instant where the value of the detection signal crosses the first detection threshold in the first direction.

9. A method according to claim 1, wherein the value of the detection signal is an amplitude, a frequency, a phase, a duration, or a number.

10. A method according to claim 1, wherein going from the object detecting state to the object non-detecting state, or vice-versa, comprises modifying a value of a state signal or a state register.

11. A method according to claim 1, wherein the object is a part of the human body.

12. A method according to claim 1, wherein the proximity sensor is a capacitive proximity sensor that supplies the detection signal.

13. A non-transitory computer readable medium, comprising program code configured to cause one or more processors to implement a method that includes:

detecting an object using a detection signal supplied by a proximity sensor, the detection signal having a value that changes as a function of the proximity of the object to the proximity sensor, the detecting including;

generating a reference signal by filtering the detection signal;

defining a first detection threshold relative to the reference signal;

going from an object non-detecting state to an object detecting state in response to detecting the detection signal crossing the first detection threshold in a first direction; and

in response to detecting the detection signal crossing the first detection threshold in the first direction, readjusting a value of the reference signal based on the detection signal and setting the first detection threshold based on the readjusted value of the reference signal such that the detection signal again crosses the first detection threshold in a second direction opposite to the first direction.

14. A non-transitory computer readable medium according to claim 13, wherein the method comprises, while in the object detecting state:

detecting that the detection signal again crosses the first detection threshold in the first direction; and

again readjusting the value of the reference signal in a manner such that the detection signal again crosses the first detection threshold in the second direction in response to detecting that the detection signal again crosses the first detection threshold in the first direction.

15. A non-transitory computer readable medium according to claim 13, wherein the method comprises:

defining a second detection threshold relative to the reference signal,

going from the object detecting state to the object non-detecting state in response to detecting that the detection signal crosses the second detection threshold in the second direction, and

in response to detecting that the detection signal crosses the second detection threshold in the second direction, readjusting the value of the reference signal in a manner such that the detection signal crosses the second detection threshold in the first direction.

16. A non-transitory computer readable medium according to claim 15, wherein the method comprises, while in the object detecting state:

detecting that the detection signal again crosses the second detection threshold in the second direction; and

again readjusting the value of the reference signal in a manner such that the detection signal again crosses the second detection threshold in the first direction in response to detecting that the detection signal again crosses the second detection threshold in the second direction, without modifying the non-detecting state.

17. A proximity detector comprising:

a proximity sensor configured to supply a detection signal having a value that changes based on a proximity of an object to the sensor; and

a processing unit configured to receive the detection signal, wherein the processing unit is configured to;

generate a reference signal by filtering the detection signal;

define a first detection threshold relative to the reference signal;

go from an object non-detecting state to an object detecting state in response to detecting the detection signal crossing the first detection threshold in a first direction; and

in response to detecting the detection signal crossing the first detection threshold in the first direction, readjust a value of the reference signal based on the detection signal and set the first detection threshold based on the readjusted value of the reference signal such that the detection signal again crosses the first detection threshold in a second direction opposite to the first direction.

18. The proximity detector according to claim 17, wherein the proximity sensor includes a sensitive portion and a sensor controller configured to read and control the sensitive portion.

19. A portable device, comprising:

a first element that can be activated and deactivated; and

a first proximity detector configured to activate or deactivate the first element when an object is detected in proximity of the device, the first proximity detector including;

a proximity sensor configured to supply a detection signal having a value that changes based on a proximity of an object to the sensor; and

a processing unit configured to receive the detection signal, wherein the processing unit is configured to;

generate a reference signal by filtering the detection signal;

define a first detection threshold relative to the reference signal;

go from an object non-detecting state to an object detecting state in response to detecting the detection signal crossing the first detection threshold in a first direction; and

in response to detecting the detection signal crossing the first detection threshold in the first direction, readjust a value of the reference signal based on the detection signal and set the first detection threshold based on the readjusted value of the reference signal such that the detection signal again crosses the first detection threshold in a second direction opposite to the first direction.

20. The portable device according to claim 19, wherein the proximity sensor includes a sensitive portion and a sensor controller configured to read and control the sensitive portion.

21. The portable device according to claim 19, comprising:

a second element that can be activated and deactivated; and

a second proximity detector configured to activate or deactivate the second element when the object contacts the device.