IPC분류정보
국가/구분 |
United States(US) Patent
등록
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국제특허분류(IPC7판) |
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출원번호 |
US-0202867
(2002-07-26)
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발명자
/ 주소 |
- Casebolt, Mark W.
- Rensberger, Gary
- Bathiche, Steven N.
- Albulet, Mihai
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출원인 / 주소 |
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대리인 / 주소 |
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인용정보 |
피인용 횟수 :
11 인용 특허 :
78 |
초록
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Capacitive proximity sensing is carried out by detecting a relative change in the capacitance of a “scoop” capacitor formed by a conductor and a surrounding ground plane. Charge is transferred between the “scoop” capacitor and a relatively large “bucket” capacitor, and a voltage of the bucket capaci
Capacitive proximity sensing is carried out by detecting a relative change in the capacitance of a “scoop” capacitor formed by a conductor and a surrounding ground plane. Charge is transferred between the “scoop” capacitor and a relatively large “bucket” capacitor, and a voltage of the bucket capacitor is applied to an input threshold switch. A state transition (e.g., from low to high, or high to low) of the input threshold switch is detected and a value (TouchVal) indicative of a number of cycles of charge transfer required to reach the state transition is determined. The presence or absence of an object or body portion in close proximity to or contact with a device can be determined by comparing TouchVal with a predetermined threshold value (TouchOff). In order to lessen the time required for detection, and/or improve the sensitivity thereof, the bucket capacitor may initially be charged to a repeatable non-zero reference level closer to the charge level that will cause a state transition. TouchOff can be adjusted to take into account environmentally induced (non-touch related) changes in the capacitance of the scoop capacitor. Power management may be provided in a user operated data input device utilizing the inventive proximity sensing.
대표청구항
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1. A capacitive sensing system for sensing the presence of an object or body portion in contact with or close proximity to another object, comprising:a first conductor capacitively coupled to a ground to thereby form a scoop capacitor having a capacitance which varies in relation to the proximity of
1. A capacitive sensing system for sensing the presence of an object or body portion in contact with or close proximity to another object, comprising:a first conductor capacitively coupled to a ground to thereby form a scoop capacitor having a capacitance which varies in relation to the proximity of said object or body portion to said conductor; a pair of second and third conductors forming a bucket capacitor having a capacitance which is larger than a maximum capacitance of said scoop capacitor; an input threshold switch; charge setting means for setting a charge of said bucket capacitor at a repeatable non-zero reference level; switching means for selectively: connecting at least one of said scoop capacitor and bucket capacitor to a voltage source to charge said at least one capacitor, connecting said charge setting means to said bucket capacitor to set the charge of the bucket capacitor to said repeatable non-zero reference level, varying the charge of said bucket capacitor from the reference level set by said charge setting means, in relation to a relative size of said scoop capacitor, and applying a voltage of said bucket capacitor to said input threshold switch; detector means for detecting an input state of said input threshold switch; determining means for determining a value (TouchVal) relating to a number of cycles of said varying of the bucket capacitor charge, corresponding to a detection of a transition of said input threshold switch by said detector means; and signal generating means for generating, based upon TouchVal, a signal indicative of an ON state wherein said object or body portion is in contact with or close proximity to said another object, and an OFF state wherein said object or body portion is not in contact with or close proximity to said another object. 2. A capacitive sensing system according to claim 1, wherein the at least one capacitor comprises said scoop capacitor, and said varying of the charge of said bucket capacitor comprises transferring charge from said scoop capacitor to said bucket capacitor.3. A capacitive sensing system according to claim 1, wherein the at least one capacitor comprises said bucket capacitor and said varying of the charge of said bucket capacitor comprises transferring charge from said bucket capacitor to said scoop capacitor.4. A capacitive sensing system according to claim 1, wherein the at least one capacitor comprises said scoop capacitor and said bucket capacitor connected in series, and said varying of the charge of said bucket capacitor comprises charging said bucket capacitor with said voltage source, as regulated by said scoop capacitor.5. A capacitive sensing system according to claim 1, further comprising comparing means for comparing TouchVal, or a number derived from TouchVal, with a predetermined threshold value (TouchOff), or a number derived from TouchOff; and wherein said signal generating means generates said ON and OFF state indicating signals based upon an output of said comparing means.6. A capacitive sensing system according to claim 1, wherein said object is a computer peripheral device, and said first conductor is mounted on said computer peripheral device.7. A capacitive sensing system according to claim 6, wherein said computer peripheral device is an external computer peripheral device linkable to a separate host computer, said peripheral device incorporating therein a power supply.8. A capacitive sensing system according to claim 7, wherein said external computer peripheral device is linkable to a host computer without a hard-wired connection.9. A capacitive sensing system according to claim 8, wherein said external computer peripheral device is a cursor control device comprising an optical tracking engine.10. A capacitive sensing system according to claim 9, wherein said cursor control device is a computer mouse configured to track on a planar surface upon which the mouse rests.11. A capacitive sensing system according to claim 1, wherein TouchVal for a control cycle n is a moving average value.12. A capacitive sensing system according to claim 5, further comprising threshold count determining means for dynamically adjusting the value of TouchOff in accordance with a relative decrease in the capacitance of said scoop capacitor occurring during said OFF state.13. A capacitive sensing system according to claim 12, further comprising means for deriving a value (TouchAvg) from TouchVal, said comparing means comparing TouchAvg with TouchOff during said ON state.14. A capacitive sensing system according to claim 13, wherein TouchAvg is initially set to equal TouchVal upon a transition from the OFF state to the ON state, and the value of TouchAvg is incremented upon TouchVal exceeding TouchAvg for a predetermined interval.15. A capacitive sensing system according to claim 12, wherein said decrease in the capacitance of said scoop capacitor is determined from the occurrence of an increase in TouchVal during said OFF state.16. A capacitive sensing system according to claim 15, wherein said decrease in the capacitance of said scoop capacitor is determined from TouchVal remaining above TouchOff for a predetermined interval.17. A capacitive sensing system according to claim 5, further comprising means for deriving a value (TouchAvg) from TouchVal, said comparing means comparing TouchAvg with TouchOff during said ON state.18. A capacitive sensing system according to claim 5, wherein said signal generating means transitions from said OFF state to said ON state upon TouchVal decreasing below TouchOff by a predetermined amount.19. A capacitive sensing system according to claim 5, said system decrementing Touch Off upon TouchVal remaining below TouchOff for a predetermined interval.20. A capacitive sensing system according to claim 1, wherein said input threshold switch comprises a CMOS transistor.21. A capacitive sensing system according to claim 2, said first conductor of said scoop capacitor being commonly connected, together with a first one of said pair of conductors of said bucket capacitor, to a first terminal, the second of said pair of conductors of the bucket capacitor being connected to a second terminal, said first one of said pair of conductors of said bucket capacitor further being connected to a third terminal wherein:said switching means cyclically: (a) clamps the first, second and third terminals to ground, to discharge the bucket capacitor; (b) sets the first terminal to high impedance and drives the third terminal to thereby set said reference level charge of said bucket capacitor; (c) sets the second and third terminals to be high impedance inputs and drives the first terminal, to charge the scoop capacitor without charging the bucket capacitor; and (d) sets the first terminal to be a high impedance input and drives the second terminal, to transfer charge from the scoop capacitor to the bucket capacitor; said input threshold switch is connected to one of said first terminal and said second terminal to receive a voltage therefrom when said one terminal is set to be said high impedance input; and said detector means samples, in relation to the cycling of said switching means, a state of said input threshold switch. 22. A capacitive sensing system according to claim 21, wherein said first one of said pair of conductors of said bucket capacitor is connected to said third terminal through an impedance element.23. A capacitive sensing system according to claim 22, wherein said impedance element comprises a resistor.24. A capacitive sensing system according to claim 3, said first conductor of said scoop capacitor being commonly connected, together with a first one of said pair of conductors of said bucket capacitor, to a first terminal, the second of said pair of conductors of the bucket capacitor being connected to a second terminal, said first one of said pair of conductors of said bucket capacitor further being connected to a third terminal, wherein:said switching means cyclically: (a) drives the first terminal high, drives the second terminal low and sets the third terminal to high impedance, to charge the bucket capacitor; (b) sets the first terminal to high impedance and drives the third terminal low to thereby drop the charge of said bucket capacitor to said reference charge level; (c) sets the second and third terminals to be high impedance inputs and drives the first terminal low, to discharge the scoop capacitor without discharging the bucket capacitor, and (d) sets the first terminal to be a high impedance input and drives the second terminal to transfer charge from the bucket capacitor to the scoop capacitor; said input threshold switch is connected to one of said first terminal and said second terminal to receive a voltage therefrom when said one terminal is set to be said high impedance input; and said detector means samples, in relation to the cycling of said switching means, a state of said input threshold switch. 25. A capacitive sensing system according to claim 24, wherein said first one of said pair of conductors of said bucket capacitor is connected to said third terminal through an impedance element.26. A capacitive sensing system according to claim 25, wherein said impedance element comprises a resistor.27. A capacitive sensing system according to claim 4, said first conductor of said scoop capacitor being commonly connected, together with a first one of said pair of conductors of said bucket capacitor, to a first terminal, the second of said pair of conductors of the bucket capacitor being connected to a second terminal, said first one of said pair of conductors of said bucket capacitor further being connected to a third terminal, wherein:said switching means cyclically: (a) drives the first, second and third terminals low, to discharge the bucket capacitor and scoop capacitor; (b) sets the second terminal to high impedance and drives the third terminal high to thereby set said reference level charge of said bucket capacitor; (c) sets the first terminal to be a high impedance input and drives the second terminal high, to place the bucket capacitor and scoop capacitor in series, and (d) sets the second terminal to be a high impedance input and drives the first terminal low, to discharge the scoop capacitor without discharging the bucket capacitor; said input threshold switch is connected to one of said first terminal and said second terminal to receive a voltage therefrom when said one terminal is set to be said high impedance input; and said detector means samples, in relation to the cycling of said switching means, a state of said input threshold switch. 28. A capacitive sensing system according to claim 27, wherein said first one of said pair of conductors of said bucket capacitor is connected to said third terminal through an impedance element.29. A capacitive sensing system according to claim 28, wherein said impedance element comprises a resistor.30. A capacitive sensing system according to claim 1, wherein said input threshold switch, said switching means, said detector means, said determining means and said signal generating means are provided within a control integrated circuit (IC) having three pins, said first conductor of said scoop capacitor being commonly connected, together with a first one of said pair of conductors of said bucket capacitor, to a first one of said pair of pins, the second of said pair of conductors of the bucket capacitor being connected to a second of said three pins, the second of said pair of conductors of the bucket capacitor further being connected to a third of said pins.31. A capacitive sensing system according to claim 30, wherein:said switching means cyclically: (a) clamps the first, second and third pins to ground, to discharge the bucket capacitor; (b) sets the first terminal to high impedance and drives the third terminal to thereby set a charge of said bucket capacitor at a repeatable non-zero reference level; (c) sets the second and third pins to be high impedance inputs and drives the first pin to charge the scoop capacitor without charging the bucket capacitor; and (d) sets the first pin to be a high impedance input and drives the second pin, to transfer charge of the scoop capacitor to the bucket capacitor; said input threshold switch is connected to one of said first pin and said second pin to receive a voltage therefrom when said one pin is set to be said high impedance input; and said detector means samples, in relation to the cycling of said switching means, a state of said input threshold switch. 32. A capacitive sensing system according to claim 30, wherein:said switching means cyclically: (a) drives the first pin high, drives the second pin low, and sets the third terminal to high impedance, to charge the bucket capacitor; (b) sets the first pin to high impedance and drives the third pin low, to thereby drop the charge of said bucket capacitor to said reference level; (c) sets the second and third pins to be high impedance inputs and drives the first pin low, to discharge the scoop capacitor without discharging the bucket capacitor; and (d) sets said first pin to be a high impedance input and drives the second pin, to transfer charge from the bucket capacitor to the scoop capacitor; said input threshold switch is connected to one of said first pin and said second pin to receive a voltage therefrom when said one pin is set to be said high impedance input; and said detector means samples, in relation to the cycling of said switching means, a state of said input threshold switch. 33. A capacitive sensing system according to claim 30, wherein:said switching means cyclically: (a) drives the first, second and third pins low, to discharge the bucket capacitor and scoop capacitor; (b) sets the second pin to high impedance and drives the third pin high to thereby set a charge of said bucket capacitor at a repeatable non-zero reference level; (c) sets the first pin to be a high impedance input and drives the second pin high, to place the bucket capacitor and scoop capacitor in series; and (d) sets said second pin to be a high impedance input and drives the first pin low, to discharge the scoop capacitor without discharging the bucket capacitor; said input threshold switch is connected to one of said first pin and said second pin to receive a voltage therefrom when said one pin is set to be said high impedance input; and said detector means samples, in relation to the cycling of said switching means, a state of said input threshold switch. 34. A method for sensing the presence of an object or body portion in contact with or close proximity to another object, comprising:providing a first conductor capacitively coupled to a ground to thereby form a scoop capacitor having a capacitance which varies in relation to the proximity of said object or body portion to said conductor; a pair of second and third conductors forming a bucket capacitor having a capacitance which is larger than a maximum capacitance of said scoop capacitor; and an input threshold switch; performing switching to selectively: connect at least one of said scoop capacitor and said bucket capacitor to a voltage source to charge said at least one capacitor, set a charge of said bucket capacitor at a repeatable non-zero reference level, vary the charge of said bucket capacitor from said reference level in relation to a relative size of said scoop capacitor, and apply a voltage of said bucket capacitor to said input threshold switch; detecting an input state of said input threshold switch; determining a value (TouchVal) relating to a number of cycles of said varying of the bucket capacitor charge, corresponding to a detection of a transition of said input threshold switch; and generating, based upon TouchVal, a signal indicative of an ON state wherein said object or body portion is in contact with or close proximity to said another object, and an OFF state wherein said object or body portion is not in contact with or close proximity to said object. 35. A method for sensing according to claim 34, wherein the at least one capacitor comprises said scoop capacitor and said varying of the charge of said bucket capacitor comprises transferring charge from said scoop capacitor to said bucket capacitor.36. A method for sensing according to claim 34, wherein the at least one capacitor comprises said bucket capacitor, and said varying of the charge of said bucket capacitor comprises transferring charge from said bucket capacitor to said scoop capacitor.37. A method for sensing according to claim 34, wherein the at least one capacitor comprises said scoop capacitor and said bucket capacitor connected in series, and said varying of the charge of said bucket capacitor comprises charging said bucket capacitor with said voltage source, as regulated by said scoop capacitor.38. A method for sensing according to claim 34, further comprising comparing TouchVal, or a number derived from TouchVal, with a predetermined threshold value (TouchOff), or a number derived from TouchOff; and wherein said signal generating generates said ON and OFF state indicating signals based upon an output of said comparing.39. A method for sensing according to claim 34, wherein TouchVal for a control cycle n is a moving average value.40. A method for sensing according to claim 38, further comprising dynamically adjusting the value of TouchOff in accordance with a relative decrease in the capacitance of said scoop capacitor occurring during said OFF state.41. A method for sensing according to claim 40, further comprising deriving a value (TouchAvg) from TouchVal, wherein said comparing compares TouchAvg with TouchOff during said ON state.42. A method for sensing according to claim 41, wherein TouchAvg is initially set to equal TouchVal upon a transition from the OFF state to the ON state, and the value of TouchAvg is incremented upon TouchVal exceeding TouchAvg for a predetermined interval.43. A method for sensing according to claim 42, wherein said decrease in the capacitance of said scoop capacitor is determined from the occurrence of an increase in TouchVal during said OFF state.44. A method for sensing according to claim 43, wherein said decrease in the capacitance of said scoop capacitor is determined from TouchVal remaining above TouchOff for a predetermined interval.45. A method for sensing according to claim 38, further comprising deriving a value (TouchAvg) from TouchVal, wherein said comparing compares TouchAvg with TouchOff during said ON state.46. A method for sensing according to claim 38, wherein in said signal generating, a transition from said OFF state to said ON state occurs upon TouchVal decreasing below TouchOff by a predetermined amount.47. A method according to claim 38, wherein TouchOff is decremented upon TouchVal remaining below TouchOff for a predetermined interval.48. A method for sensing according to claim 35, wherein:said first conductor of said scoop capacitor is commonly connected, together with a first one of said pair of conductors of said bucket capacitor, to a first terminal, the second of said pair of conductors of the bucket capacitor being connected to a second terminal, and said first one of said pair of conductors of said bucket capacitor is further connected to a third terminal; said switching cyclically: (a) clamps the first, second and third terminals to ground, to discharge the bucket capacitor; (b) sets the first terminal to high impedance and drives the third terminal to thereby set the charge of said bucket capacitor to said reference level; (c) sets the second and third terminals to be high impedance inputs and drives the first terminal to charge the scoop capacitor without charging the bucket capacitor, said input threshold switch being connected to one of said first terminal and said second terminal to receive a voltage therefrom when said one terminal is set to be said high impedance input; and (d) sets the first terminal to be a high impedance input and drives the second terminal, to transfer charge of the scoop capacitor to the bucket capacitor; and said detecting comprises sampling, in relation to the cycling through steps (a)-(d), a state of said input threshold switch. 49. A method for sensing according to claim 36, wherein:said first conductor of said scoop capacitor is commonly connected, together with a first one of said pair of conductors of said bucket capacitor, to a first terminal, the second of said pair of conductors of the bucket capacitor being connected to a second terminal, and said first one of said pair of conductors of said bucket capacitor is further connected to a third terminal; said switching cyclically: (a) drives the first terminal high, drives the second terminal low and sets the third terminal to high impedance, to charge the bucket capacitor; (b) sets the first terminal to high impedance and drives the third terminal low to thereby drop the charge of said bucket capacitor to said reference level; (c) sets the second and third terminals to be high impedance inputs and drives the first terminal low, to discharge the scoop capacitor without discharging the bucket capacitor; and (d) sets said first terminal to be a high impedance input and drives the second terminal, to transfer charge from the bucket capacitor to the scoop capacitor, said input threshold switch being connected to one of said first terminal and said second terminal to receive a voltage therefrom when said one terminal is set to be said high impedance input; and said detecting comprises sampling, in relation to the cycling through steps (a)-(d), a state of said input threshold switch. 50. A method for sensing according to claim 37, wherein:said first conductor of said scoop capacitor is commonly connected, together with a first one of said pair of conductors of said bucket capacitor, to a first terminal, the second of said pair of conductors of the bucket capacitor being connected to a second terminal, said first one of said pair of conductors of said bucket capacitor further being connected to a third terminal; said switching cyclically: (a) drives the first, second and third terminals low, to discharge the bucket capacitor and scoop capacitor; (b) sets the second terminal to high impedance and drives the third terminal high to thereby set said reference level charge of said bucket capacitor; (c) sets the first terminal to be a high impedance input and drives the second terminal high, to place the bucket capacitor and scoop capacitor in series; and (d) sets said second terminal to be a high impedance input and drives the first terminal low, to discharge the scoop capacitor without discharging the bucket capacitor, said input threshold switch being connected to one of said first terminal and said second terminal to receive a voltage therefrom when said one terminal is set to be said high impedance input; and said detecting comprises sampling, in relation to the cycling through steps (a)-(d), a state of said input threshold switch.
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