Interference-resistant compensation for illumination devices using multiple series of measurement intervals

Abstract

A method and illumination device are provided for interference-resistant compensation in light emitting diode (LED) illumination devices. In one embodiment, the method includes bringing to a level insufficient to produce illumination the respective drive current of all except one of multiple emission LED elements for the duration of a first measurement interval and a later-occurring second measurement interval. The first and second measurement intervals are within respective first and second series of measurement intervals interspersed with periods of illumination, and the first and second series of measurement intervals are separated by respective first and second offsets from a timing reference. An embodiment of an illumination device includes multiple emission LED elements, one or more photodetectors, and a lamp control circuit, where the lamp control circuit is adapted to perform steps of the method.

What is claimed is: 
     
       1. A method for controlling an illumination device comprising multiple emission light emitting diode (LED) elements, the method comprising:
 operating one or more of the multiple emission LED elements to produce illumination substantially continuously by supplying a respective drive current at an operative drive current level to each of the one or more of the multiple emission LED elements;   bringing the respective drive current of all except one of the emission LED elements within the illumination device to a non-operative drive current level, which is insufficient to produce illumination, for the duration of a first measurement interval, wherein the first measurement interval is one of a first series of measurement intervals interspersed with periods of said illumination; and   bringing the respective drive current of all except one of the emission LED elements to a non-operative drive current level, which is insufficient to produce illumination, for the duration of a second measurement interval subsequent to the first measurement interval, wherein the second measurement interval is one of a second series of measurement intervals interspersed with periods of said illumination, and wherein the first series of measurement intervals and second series of measurement intervals are separated by respective first and second offsets from a timing reference.   
     
     
       2. The method of  claim 1 , further comprising, at a time subsequent to the end of the first measurement interval, discontinuing use of the first series of measurement intervals. 
     
     
       3. The method of  claim 1 , further comprising:
 during each of said first measurement interval and said second measurement interval, applying a drive current at an operative drive current level, which is sufficient to produce illumination, to the one of the emission LED elements; and   monitoring a measurement photocurrent induced in a measurement photodetector during said applying a drive current.   
     
     
       4. The method of  claim 3 , further comprising determining whether a result of said monitoring a measurement photocurrent during the first measurement interval is outside of an expected range. 
     
     
       5. The method of  claim 4 , wherein said bringing the respective drive current of all except one of the emission LED elements to a non-operative drive current level which is insufficient to produce illumination, for the duration of a second measurement interval is in response to a determination that the result of said monitoring a measurement photocurrent is outside of the expected range. 
     
     
       6. The method of  claim 4 , further comprising, in response to a determination that the result of said monitoring a measurement photocurrent during the first measurement interval is outside of the expected range:
 repeating, during an additional one of the first series of measurement intervals, said applying a drive current at an operative drive current level, which is sufficient to produce illumination, to the one of the emission LED elements and said monitoring a measurement photocurrent induced in the measurement photodetector; and   determining whether a predetermined number of out-of-range measurements using the first series of measurement intervals has occurred.   
     
     
       7. The method of  claim 6 , wherein said bringing the respective drive current of all except one of the emission LED elements to a non-operative drive current level, which is insufficient to produce illumination, for the duration of a second measurement interval is in response to a determination that the predetermined number of out-of-range measurements using the first series of measurement intervals has occurred. 
     
     
       8. The method of  claim 4 , further comprising, for each of the first and second measurement intervals:
 bringing the drive current applied to the one of the emission LED elements to a non-operative drive current level, which is insufficient to produce illumination, for a portion of the measurement interval, such that the respective drive currents of all of the emission LED elements within the illumination device are at a non-operative drive current level for the portion of the measurement interval;   monitoring a background photocurrent induced in the measurement photodetector during the portion of the measurement interval; and   subtracting the background photocurrent from the measurement photocurrent.   
     
     
       9. The method of  claim 8 , wherein the result of said monitoring a measurement photocurrent during the first measurement interval comprises a result of said subtracting the background photocurrent from the measurement photocurrent for the first measurement interval. 
     
     
       10. The method of  claim 4 , wherein said determining that a result of said monitoring a measurement photocurrent during the first measurement interval is outside of an expected range comprises comparing the result to a previously stored result. 
     
     
       11. An illumination device, comprising:
 multiple emission light emitting diode (LED) elements;   one or more photodetectors; and   a control circuit operably coupled to the multiple emission LED elements and the one or more photodetectors, wherein the control circuit is adapted to:
 operate one or more of the multiple emission LED elements to produce illumination substantially continuously by supplying a respective drive current at an operative drive current level to each of the one or more of the multiple emission LED elements; 
 bring the respective drive currents of all except one of the emission LED elements within the illumination device to a non-operative drive current level, which is insufficient to produce illumination for the duration of a first measurement interval, wherein the first measurement interval is one of a first series of measurement intervals interspersed with periods of said illumination; and 
   bring the respective drive currents of all except one of the emission LED elements to a non-operative drive current level, which is insufficient to produce illumination, for the duration of a second measurement interval subsequent to the first measurement interval, wherein the second measurement interval is one of a second series of measurement intervals interspersed with periods of said illumination, and wherein the first series of measurement intervals and second series of measurement intervals are separated by respective first and second offsets from a timing reference.   
     
     
       12. The illumination device of  claim 11 , further comprising a timing reference generator operatively coupled to the control circuit and adapted to generate a periodic timing reference, and wherein the control circuit is further adapted to:
 generate the first series of measurement intervals synchronized to the timing reference with a first offset from the timing reference; and   generate the second series of measurement intervals synchronized to the timing reference with a second offset from the timing reference.   
     
     
       13. The illumination device of  claim 11 , wherein the control circuit is further adapted to discontinue use of the first series of measurement intervals at a time subsequent to the end of the first measurement interval. 
     
     
       14. The illumination device of  claim 11 , further comprising an LED driver and receiver circuit operably coupled to the multiple emission LED elements, the one or more photodetectors, and the control circuit, and wherein the control circuit is adapted to use the LED driver and receiver circuit to adjust the respective drive currents of the emission LED elements. 
     
     
       15. The illumination device of  claim 14 , wherein, during each of said first measurement interval and said second measurement interval, the control circuit is further adapted to use the LED driver and receiver circuit to:
 bring the respective drive currents of all except one of the emission LED elements to a non-operative drive current level, which is insufficient to produce illumination;   apply a drive current to an operative drive current level, which is sufficient to produce illumination, to the one of the emission LED elements; and   monitor a measurement photocurrent induced in the measurement photodetector during said applying a drive current.   
     
     
       16. The illumination device of  claim 15 , wherein the control circuit is further adapted to determine whether a result of monitoring the measurement photocurrent during the first measurement interval is outside of an expected range. 
     
     
       17. The illumination device of  claim 16 , further comprising a storage medium operably coupled to the control circuit, and wherein the control circuit is adapted to compare the result of monitoring the measurement photocurrent during the first measurement interval with a result previously stored in the storage medium. 
     
     
       18. The illumination device of  claim 16 , wherein the control circuit is further adapted to bring the respective drive currents of all except one of the emission LED elements to a non-operative drive current level, which is insufficient to produce illumination, for the duration of the second measurement interval in response to a determination that the result is outside of the expected range. 
     
     
       19. The illumination device of  claim 16 , wherein the control circuit is further adapted to determine whether a predetermined number of out-of-range measurements using the first series of measurement intervals has occurred. 
     
     
       20. The illumination device of  claim 16 , wherein, for each of the first and second measurement intervals, the control circuit is further adapted to:
 bring the drive current applied to the one of the emission LED elements to a non-operative drive current level, which is insufficient to produce illumination, for a portion of the measurement interval, such that the respective drive currents of all of the emission LED elements within the illumination device are at a non-operative drive current level for the portion of the measurement interval;   monitor a background photocurrent induced in the measurement photodetector during the portion of the measurement interval; and   subtract the background photocurrent from the measurement photocurrent.   
     
     
       21. The illumination device of  claim 20 , wherein the control circuit is further adapted to determine whether a result of subtracting the background photocurrent from the measurement photocurrent during the first measurement interval is outside of an expected range. 
     
     
       22. A method of determining a target operative current to achieve a target luminous flux from an LED element, the method comprising:
 providing an operative current to a plurality of LED elements for each of a plurality of sequential illumination intervals, each of the plurality of sequential illumination intervals spaced apart by an intervening measurement interval;   for a respective LED element included in the plurality of LED elements:
 providing, over a first temporal interval, an operative current to the respective LED element contemporaneous with providing a non-operative current to a remaining plurality of LED elements such that the remaining plurality of LED elements do not emit light; 
 detecting a first photocurrent induced in at least one photodetector by the illumination emitted by the respective LED element contemporaneous with maintaining the operative current to the respective LED element; 
 providing, over a second temporal interval, a non-operative current to the respective LED element such that the LED element does not emit light; 
 detecting a second photocurrent induced in at least one photodetector by an ambient illumination level contemporaneous with maintaining the non-operative current to the respective LED element; 
 determining a target operative current to achieve a desired luminous flux using the respective LED by subtracting the second photocurrent from the first photocurrent; and 
 determining whether the target operative current falls within a defined target operating current range. 
   
     
     
       23. The method of claim 22 further comprising:
 storing the determined target operative current in a communicatively coupled memory circuitry responsive to the determination that the target operative current falls within the defined target operating current range.   
     
     
       24. The method of claim 23 further comprising:
 determining an updated defined target operating current range using the determined target operative current; and   storing the updated defined target operating current range as the defined target operating current range in the communicatively coupled memory circuitry.   
     
     
       25. The method of claim 22 further comprising:
 discarding the determined target operative current responsive to the determination that the target operative current fails to fall within the defined target operating current range.   
     
     
       26. The method of claim 22, wherein providing, over the first temporal interval, the operative current to the respective LED element and providing, over the second temporal interval, the non-operative current to the respective LED element further comprises:
 providing, over a first portion of a measurement interval, the operative current to the respective LED element and providing, over a second portion of the measurement interval, the non-operative current to the respective LED.   
     
     
       27. The method of claim 22:
 wherein providing, over the first temporal interval, the operative current to the respective LED element further comprises providing, over at least a portion of a first measurement interval, the operative current to the respective LED element; and   providing, over the second temporal interval, the non-operative current to the respective LED element further comprises providing, over at least a portion of a second measurement interval, the non-operative current to the respective LED element.   
     
     
       28. The method of claim 27, wherein the first measurement interval and the second measurement interval include sequential measurement intervals. 
     
     
       29. The method of claim 22, further comprising determining a plurality of operative currents to achieve a respective plurality of target luminous flux outputs for the respective LED by repeating the detection of the first photocurrent and the second photocurrent at each of a plurality of operative currents. 
     
     
       30. The method of claim 29, wherein repeating the detection of the first photocurrent and the second photocurrent at each of a plurality of operative currents further comprises:
 repeating the detection of the first photocurrent and the second photocurrent at each of a plurality of operative currents that include: a 10% operative current a 70% operative current and a 100% operative current.   
     
     
       31. The method of claim 29, wherein repeating the detection of the first photocurrent and the second photocurrent at each of the plurality of operative currents further comprises:
 detecting the first photocurrent and detecting the second photocurrent at each respective one of the plurality of operative currents over a corresponding plurality of sequential measurement intervals.   
     
     
       32. The method of claim 29, wherein repeating the detection of the first photocurrent and the second photocurrent at each of the plurality of operative currents further comprises:
 detecting the first photocurrent and detecting the second photocurrent at each respective one of the plurality of operative currents over a single measurement interval.   
     
     
       33. The method of claim 22, further comprising:
 determining the target operative current to achieve the target luminous flux output for the respective LED by repeating the detection of the first photocurrent and the second photocurrent responsive to a detected change in one or more ambient conditions.   
     
     
       34. The method of claim 33, wherein determining the target operative current to achieve the target luminous flux output for the respective LED responsive to the detected change in one or more ambient conditions further comprises:
 determining the target operative current to achieve the target luminous flux output for the respective LED by repeating the measurement of the first photocurrent and the second photocurrent responsive to a detected change in an ambient temperature or a detected change in an ambient illumination level.   
     
     
       35. The method of claim 22, wherein detecting the first photocurrent induced in the at least one photodetector by the illumination emitted by the respective LED element further comprises:
 detecting the first photocurrent induced in a first photodetector by the illumination emitted by the respective LED element.   
     
     
       36. The method of claim 35, wherein detecting the second photocurrent induced in the at least one photodetector by the ambient illumination level further comprises:
 detecting the second photocurrent induced in a second photodetector by the ambient illumination level, the second photodetector different than the first photodetector.   
     
     
       37. The method of claim 22, wherein detecting the first photocurrent induced in the at least one photodetector by the illumination emitted by the respective LED element further comprises:
 detecting the first photocurrent induced in a first photodetector by the illumination emitted by the respective LED element.   
     
     
       38. The method of claim 37, wherein detecting the second photocurrent induced in the at least one photodetector by the ambient illumination level further comprises:
 detecting the second photocurrent induced in the first photodetector by the ambient illumination level.   
     
     
       39. A controller to determine a target operative current to achieve a target luminous flux from a light emitting diode (LED) element, comprising:
 memory circuitry; and   control circuitry communicatively coupled to the memory circuitry, the control circuitry to:
 provide an operative current to a plurality of LED elements for each of a plurality of sequential illumination intervals, each of the plurality of sequential illumination intervals spaced apart by an intervening measurement interval; 
 for a respective LED element included in the plurality of LED elements:
 provide, during a first temporal interval, an operative current to the respective LED element contemporaneous with providing a non-operative current to the remaining plurality of LED elements such that the remaining plurality of LED elements do not emit light; 
 detect a first photocurrent induced in at least one photodetector by the illumination emitted by the respective LED element contemporaneous with maintaining the operative current to the respective LED element; 
 provide, during a second temporal interval, a non-operative current to the respective LED element such that the respective LED element does not emit light; 
 detect a second photocurrent induced in at least one photodetector by an ambient illumination level contemporaneous with maintaining the non-operative current to the respective LED element; 
 determine a target operative current to achieve a desired luminous flux using the respective LED by subtracting the second photocurrent from the first photocurrent; and 
 determine whether the target operative current falls within a defined target operating current range. 
 
   
     
     
       40. The controller of claim 39, wherein the control circuitry to further:
 store the determined target operative current in the communicatively coupled memory circuitry responsive to the determination that the target operative current falls within the defined target operating current range.   
     
     
       41. The controller of claim 40, wherein the control circuitry to further:
 determine an updated defined target operating current range using the determined target operative current; and   store the updated defined target operating current range in the communicatively coupled memory circuitry as the defined target operating current range.   
     
     
       42. The controller of claim 39, the control circuitry to further:
 discard the determined target operative current responsive to the determination that the target operative current fails to fall within the defined target operating current range.   
     
     
       43. The controller of claim 39, wherein a single measurement interval includes both the first temporal interval and the second temporal interval. 
     
     
       44. The controller of claim 39, wherein a first measurement interval includes the first temporal interval and a second measurement interval includes the second temporal interval. 
     
     
       45. The controller of claim 44, wherein the first measurement interval and the second measurement interval include sequential measurement intervals. 
     
     
       46. The controller of claim 39, the control circuitry to further:
 determine a plurality of target operative currents to achieve a respective plurality of target luminous flux outputs for the respective LED by repeating the detection of the first photocurrent and the second photocurrent at each of a plurality of operative currents.   
     
     
       47. The controller of claim 46, wherein to determine a plurality of target operative currents to achieve a respective plurality of target luminous flux outputs for the respective LED at each of the plurality of operative currents, the control circuitry to further:
 determine a plurality of target operative currents to achieve a respective plurality of target luminous flux outputs for the respective LED at each of the plurality of operative currents that include: a 10% operative current a 70% operative current and a 100% operative current.   
     
     
       48. The controller of claim 46, wherein, to repeat the detection of the first photocurrent and the second photocurrent at each of the plurality of operative currents, the control circuitry to further:
 repeat the detection of the first photocurrent and the second photocurrent at each of the plurality of operative currents over a corresponding plurality of sequential measurement intervals.   
     
     
       49. The controller of claim 46, wherein, to repeat the detection of the first photocurrent and the second photocurrent at each of the plurality of operative currents, the control circuitry to further:
 repeat the detection of the first photocurrent and the second photocurrent at each of the plurality of operative currents over a single measurement interval.   
     
     
       50. The controller of claim 39, the control circuitry to further:
 determine the target operative current to achieve a target luminous flux output for the respective LED by repeating the detection of the first photocurrent and the second photocurrent responsive to a detected change in one or more ambient conditions.   
     
     
       51. The controller of claim 50 wherein, to determine the target operative current to achieve the target luminous flux output for the respective LED responsive to the detected change in one or more ambient conditions, the control circuitry to further:
 determine the target operative current to achieve the target luminous flux output for the respective LED by repeating the measurement of the first photocurrent and the second photocurrent responsive to a detected change in an ambient temperature or a detected change in an ambient illumination level.   
     
     
       52. The controller of claim 39 wherein, to detect the first photocurrent induced in the at least one photodetector by the illumination emitted by the respective LED element, the control circuitry to further:
 detect the first photocurrent induced in a first photodetector by the illumination emitted by the respective LED element.   
     
     
       53. The controller of claim 52 wherein, to detect the second photocurrent induced in the at least one photodetector by the ambient illumination level, the control circuitry to further:
 detect the second photocurrent induced in a second photodetector by the level of ambient illumination, the second photodetector different than the first photodetector.   
     
     
       54. The controller of claim 39 wherein, to detect the first photocurrent induced in the at least one photodetector by the illumination emitted by the respective LED element, the control circuitry to:
 detect the first photocurrent induced in a first photodetector by the illumination emitted by the respective LED element.   
     
     
       55. The controller of claim 54 wherein, to detect the second photocurrent induced in the at least one photodetector by the ambient illumination level, the control circuitry to:
 detect the second photocurrent induced in the first photodetector by the ambient illumination level.   
     
     
       56. A non-transitory, machine-readable, storage device that includes instructions that, when executed by control circuitry in a luminaire, cause the control circuitry to:
 provide an operative current to a plurality of LED elements for each of a plurality of sequential illumination intervals, each of the plurality of sequential illumination intervals spaced apart by an intervening measurement interval;   for a respective LED element included in the plurality of LED elements:
 provide, during a first temporal interval, an operative current to the respective LED element contemporaneous with providing a non-operative current to the remaining plurality of LED elements such that the remaining plurality of LED elements do not emit light; 
 detect a first photocurrent induced in at least one photodetector by the illumination emitted by the respective LED element contemporaneous with maintaining the operative current to the respective LED element; 
 provide, during a second temporal interval, a non-operative current to the respective LED element such that the respective LED element does not emit light; 
 detect a second photocurrent induced in at least one photodetector by an ambient illumination level contemporaneous with maintaining the non-operative current to the respective LED element; 
 determine a target operative current to achieve a desired luminous flux using the respective LED by subtracting the second photocurrent from the first photocurrent; and 
 determine whether the target operative current falls within a defined target operating current range. 
   
     
     
       57. The non-transitory, machine-readable, storage device of claim 56, wherein the instructions further cause the control circuitry to:
 store the determined target operative current in a communicatively coupled memory circuitry responsive to the determination that the target operative current falls within the defined target operating current range.   
     
     
       58. The non-transitory, machine-readable, storage device of claim 57, wherein the instructions further cause the control circuitry to:
 determine an updated defined target operating current range using the determined target operative current; and   store the updated defined target operating current range in the communicatively coupled memory circuitry as the defined target operating current range.   
     
     
       59. The non-transitory, machine-readable, storage device of claim 56, wherein the instructions further cause the control circuitry to:
 discard the determined target operative current responsive to the determination that the target operative current fails to fall within the defined target operating current range.   
     
     
       60. The non-transitory, machine-readable, storage device of claim 56, wherein the instructions that cause the control circuitry to detect the first photocurrent during the first temporal interval and detect the second photocurrent during the second temporal interval further cause the control circuitry to:
 detect the first photocurrent during a first portion of a measurement interval and detect the second photocurrent during a second portion of the measurement interval.   
     
     
       61. The non-transitory, machine-readable, storage device of claim 56, wherein the instructions that cause the control circuitry to detect the first photocurrent during the first temporal interval and detect the second photocurrent during the second temporal interval further cause the control circuitry to:
 detect the first photocurrent during a first measurement interval and detect the second photocurrent during a second measurement interval.   
     
     
       62. The non-transitory, machine-readable, storage device of claim 61, wherein the instructions that cause the control circuitry to detect the first photocurrent during a first measurement interval and to detect the second photocurrent during a second measurement interval further cause the control circuitry to:
 detect the first photocurrent during a first measurement interval and detect the second photocurrent during a second, sequential, measurement interval.   
     
     
       63. The non-transitory, machine-readable, storage device of claim 56, wherein the instructions further cause the control circuitry to:
 determine a plurality of target operative currents to achieve a respective plurality of desired luminous flux outputs for the respective LED by repeating the detection of the first photocurrent and the second photocurrent at each of a plurality of operative currents.   
     
     
       64. The non-transitory, machine-readable, storage device of claim 63, wherein the instructions that cause the control circuitry to determine a plurality of target operative currents by repeating the detection of the first photocurrent and the second photocurrent at each of a plurality of operative currents further cause the control circuitry to:
 determine the plurality of target operative currents by repeating the detection of the first photocurrent and the second photocurrent at each of a plurality of operative currents that include: a 10% operative current a 70% operative current and a 100% operative current.   
     
     
       65. The non-transitory, machine-readable, storage device of claim 63, wherein the instructions that cause the control circuitry to repeat the detection of the first photocurrent and the second photocurrent at each of the plurality of operative currents, further cause the control circuitry to:
 repeat the detection of the first photocurrent and the second photocurrent at each of the plurality of operating currents over a corresponding plurality of sequential measurement intervals.   
     
     
       66. The non-transitory, machine-readable, storage device of claim 63, wherein the instructions that cause the control circuitry to repeat the detection of the first photocurrent and the second photocurrent at each of the plurality of operative currents, further cause the control circuitry to:
 repeat the detection of the first photocurrent and the second photocurrent at each of the plurality of operative currents over a single measurement interval.   
     
     
       67. The non-transitory, machine-readable, storage device of claim 56, wherein the instructions further cause the control circuitry to:
 determine the target operative current to achieve the desired luminous flux output for the respective LED by repeating the detection of the first photocurrent and the second photocurrent responsive to a detected change in one or more ambient conditions.   
     
     
       68. The non-transitory, machine-readable, storage device of claim 67, wherein the instructions that cause the control circuitry to determine the target operative current to achieve the desired luminous flux output for the respective LED by repeating the measurement of the first photocurrent and the second photocurrent responsive to the detected change in one or more ambient conditions, further cause the control circuitry to:
 determine the target operative current to achieve the desired luminous flux output for the respective LED by repeating the measurement of the first photocurrent and the second photocurrent responsive to a detected change in an ambient temperature or a detected change in an ambient illumination level.   
     
     
       69. The non-transitory, machine-readable, storage device of claim 56, wherein the instructions that cause the control circuitry to detect the first photocurrent induced in the at least one photodetector by the illumination emitted by the respective LED element, further cause the control circuitry to:
 detect the first photocurrent induced in a first photodetector by the illumination emitted by the respective LED element.   
     
     
       70. The non-transitory, machine-readable, storage device of claim 69, wherein the instructions that cause the control circuitry to detect the second photocurrent induced in the at least one photodetector by the ambient illumination level, further cause the control circuitry to:
 detect the second photocurrent induced in a second photodetector by the level of ambient illumination, the second photodetector different than the first photodetector.   
     
     
       71. The non-transitory, machine-readable, storage device of claim 56, wherein the instructions that cause the control circuitry to detect the first photocurrent induced in the at least one photodetector by the illumination emitted by the respective LED element, further cause the control circuitry to:
 detect the first photocurrent induced in a first photodetector by the illumination emitted by the respective LED element.   
     
     
       72. The non-transitory, machine-readable, storage device of claim 71, wherein the instructions that cause the control circuitry to detect the second photocurrent induced in the at least one photodetector by the ambient illumination level, further cause the control circuitry to:
 detect the second photocurrent induced in the first photodetector by the ambient illumination level.