Interference-resistant compensation for illumination devices having multiple emitter modules

Abstract

A method and light emitting diode (LED) illumination device comprising multiple emitter modules are provided. In one embodiment, the method includes bringing to a level insufficient to produce illumination the respective drive currents of all except one of multiple emission LED elements within respective first and second emitter modules for the duration of a measurement interval within respective first and second series of measurement intervals. The measurement intervals are 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 emitter modules, where each emitter module includes multiple emission LED elements and one or more photodetectors. The illumination device further includes a lamp control circuit adapted to perform steps of the method.

What is claimed is: 
     
       1. A method for controller an illumination device comprising multiple emitter modules, wherein each emitter module comprises multiple emissions light emitting diode (LED) elements and one or more photodetectors, the method comprising:
 operating one or more of the multiple emission LED elements in each of the multiple emitter modules 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 currents of all except one of the emission LED elements within a first emitter module of the multiple emitter modules to a non-operable drive current level, which is insufficient to produce illumination, for the duration of a measurement interval within a first series of measurement intervals interspersed with periods of said illumination; and   bringing the respective drive currents of all except one of the emission LED elements within a second emitter module of the multiple emitter modules to a non-operative drive current level, which is insufficient to produce illumination, for the duration of a measurement interval within a second series of measurement intervals interspersed with periods of said illumination, wherein the first series of measurement intervals and the second series of measurement intervals are separated by a respective first offset and second offset from a timing reference.   
     
     
       2. The method of  claim 1 , for either of the first and second emitter modules, further comprising:
 during the measurement interval within the respective first or second series of measurement intervals, applying an operative drive current level, which is sufficient to produce illumination, to the one of the emission LED elements; and   during said applying an operative drive current level to the one of the emission LED elements, monitoring a respective first or second measurement photocurrent induced in the one or more photodetectors included within the emitter module.   
     
     
       3. The method of  claim 2 , for either of the first or second emitter modules, further comprising 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 respective measurement interval, such that the respective drive currents of all of the emission LED elements, within the respective emitter module are at a non-operative drive current level for the portion of the respective measurement interval. 
     
     
       4. The method of  claim 3 , for either of the first or second emitter modules and during the portion of the respective measurement intervals, further comprising monitoring a respective first or second background photocurrent induced in the one or more photodetectors included within the emitter module. 
     
     
       5. The method of  claim 4 , for either of the first or second emitter modules, further comprising subtracting the respective first or second background photocurrent from the respective first or second measurement photocurrent. 
     
     
       6. The method of  claim 5 , for either of the first or second emitter modules, further comprising storing a result of said subtracting as a respective first or second corrected photocurrent. 
     
     
       7. The method of  claim 6 , wherein said storing a result of said subtracting is in response to a determination that the result is within an expected range. 
     
     
       8. The method of  claim 1 , wherein the timing reference comprises a periodic timing signal. 
     
     
       9. The method of  claim 8 , wherein the timing reference is derived from an AC mains signal. 
     
     
       10. The method of  claim 1 , wherein the multiple emitter modules consist of one or more sets of three emitter modules, and wherein each emitter module within a set uses a respective series of measurement intervals having a different offset from the timing reference than that used by the other emitter modules within the set. 
     
     
       11. An illumination device, comprising:
 multiple emitter modules, wherein each emitter module comprises multiple emission light emitting diode (LED) elements and one or more photodetectors; and   a control circuit operably coupled to the multiple emitter modules, wherein the control circuit is adapted to:
 operative one or more of the multiple emission LED elements within each of the multiple emitter modules 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 a first emitter module of the multiple emitter modules to a non-operative drive current level, which is insufficient to produce illumination, for the duration of a measurement interval within a first series of measurement intervals interspersed with periods of said illumination; and   being the respective drive currents of all except one of the emission LED elements within a second emitter module of the multiple emitter modules to a non-operative drive current level, which is insufficient to produce illumination for the duration of a measurement interval within a second series of measurement intervals interspersed with periods of said illumination, wherein the first series of measurement intervals and the second series of measurement intervals are separated by a respective first offset and second offset 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 the timing reference. 
     
     
       13. The illumination device of  claim 12 , wherein the timing reference comprises a periodic timing signal and the timing reference generator comprises a phase-locked loop. 
     
     
       14. The illumination device of  claim 11 , further comprising multiple driver circuits operably coupled to respective emitter modules of the multiple emitter modules and to the control circuit, and wherein the control circuit is configured to adjust a drive current of an LED element within an emitter module by providing a drive current setting to a respective driver circuit for the emitter module. 
     
     
       15. The illumination device of  claim 11 , wherein, for each of the first and second emitter modules, the control circuit is further adapted to:
 during the measurement interval within the respective first or second series of measurement intervals, apply an operative drive current level, which is sufficient to produce illumination, to the one of the emission LED elements; and   during said applying the operative drive current level to the one of the emission LED elements, monitor a respective first or second measurement photocurrent induced in the one or more photodetectors included within the emitter module.   
     
     
       16. The illumination device of  claim 15 , wherein, for each of the first and second emitter modules, 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 respective measurement interval, such that the respective drive currents of all of the emission LED elements within the respective emitter module are at a non-operative drive current level for the portion of the respective measurement interval; and   during the portion of the respective measurement interval, monitor a respective first or second background photocurrent induced in the one or more photodetectors included within the emitter module.   
     
     
       17. The illumination device of  claim 16 , wherein, for each of the first and second emitter modules, the control circuit is further adapted to subtract the respective first or second background photocurrent from the respective first or second measurement photocurrent. 
     
     
       18. The illumination device of  claim 17 , further comprising a plurality of storage locations accessible by the control circuit, and wherein the control circuit is further adapted to store a result of subtracting the first or second background photocurrent from the first or second measurement photocurrent in one or more of the storage locations as a first or second corrected photocurrent. 
     
     
       19. The illumination device of  claim 18 , wherein the control circuit is further adapted to determine whether the result is within an expected range and store the result in response to a determination that the result is within an expected range. 
     
     
       20. The illumination device of  claim 11 , wherein the multiple emitter modules, and wherein the control circuit is further adapted to use, for each emitter module within a set, a respective measurement interval having a different offset from the timing reference than that of the other emitter modules within the set. 
     
     
       21. The illumination device of  claim 11 , wherein the control circuit comprises a respective module control circuit for each emitter module within the illumination device. 
     
     
       22. The illumination device of  claim 21 , wherein the control circuit further comprises a device control circuit adapted to provide to each of the module control circuits a respective offset from the timing reference for the respective series of measurement intervals used by the respective emitter module. 
     
     
       23. A method of determining a drive current to achieve a target luminous flux from each of a plurality of light emitting diode (LED) elements, the method comprising:
 providing an operative current to the plurality of LED elements for each of a plurality of sequential illumination intervals, each of the plurality of sequential illumination intervals spaced apart by respective ones of a plurality of measurement intervals;   providing, over a first portion of a measurement interval, an operative current to a respective LED element of the plurality of LED elements 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;   detecting a first photocurrent induced in at least one photodetector by an illumination emitted by the respective LED element contemporaneous with maintaining the operative current to the respective LED element;   providing, over a second portion of a measurement interval, a non-operative current to the respective LED element such that the respective LED element does not emit light;   detecting a second photocurrent induced in at least one photodetector by an ambient illumination contemporaneous with maintaining the non-operative current to the respective LED element; and   determining the drive current to achieve the target luminous flux from the respective LED element based on the first photocurrent and the second photocurrent.    
     
     
       24. The method of  claim 23 , wherein determining the drive current to achieve the target luminous flux from the respective LED element based on the first photocurrent and the second photocurrent further comprises:
 subtracting the second photocurrent from the first photocurrent to determine the drive current to achieve the target luminous flux from the respective LED element.    
     
     
       25. The method of  claim 23 , further comprising:
 determining a plurality of drive currents to achieve a respective plurality of target luminous flux outputs from the respective LED element by detecting a plurality of first photocurrents at each respective one of a plurality of operative currents and detecting a plurality of second photocurrents at each respective one of a plurality of non-operative currents.    
     
     
       26. The method of  claim 25 , wherein the plurality of operative currents includes: a 10% operative current, a 30% operative current, and a 100% operative current.  
     
     
       27. The method of  claim 23 :
 wherein providing, over the first portion of a measurement 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   wherein providing, over the second portion of a measurement 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 a respective plurality of sequential portions of measurement intervals.  
     
     
       29. The method of  claim 23 :
 wherein providing, over the first portion of a measurement interval, the operative current to the respective LED element further comprises providing, over a first portion of a first measurement interval, the operative current to the respective LED element; and   wherein providing, over the second portion of a measurement interval, the non-operative current to the respective LED element further comprises providing, over a second portion of the first measurement interval, the non-operative current to the respective LED element.    
     
     
       30. The method of  claim 23 , further comprising determining the drive current to achieve a target luminous flux output from the respective LED element by detecting the first photocurrent and detecting the second photocurrent responsive to a detected change in one or more ambient conditions.  
     
     
       31. The method of  claim 30 , wherein determining the drive current to achieve a target luminous flux output from the respective LED element by detecting the first photocurrent and detecting the second photocurrent responsive to a detected change in one or more ambient conditions comprises:
 determining the drive current to achieve the target luminous flux output from the respective LED element by detecting the first photocurrent and detecting the second photocurrent responsive to a detected change in ambient temperature.    
     
     
       32. The method of  claim 23 , 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.    
     
     
       33. The method of  claim 32 , wherein detecting the second photocurrent induced in the at least one photodetector by the ambient illumination further comprises:
 detecting the second photocurrent induced in a second photodetector by the ambient illumination, the second photodetector different than the first photodetector.    
     
     
       34. The method of  claim 32 , wherein detecting the second photocurrent induced in the at least one photodetector by the ambient illumination further comprises:
 detecting the second photocurrent induced in the first photodetector by the ambient illumination.    
     
     
       35. The method of  claim 23 , further comprising:
 storing data representative of the drive current for the respective LED element in memory circuitry communicatively coupled to controller circuitry.    
     
     
       36. A lighting controller to determine a drive current to achieve a target luminous flux from an LED element, comprising:
 light-emitting diode (LED) lighting control circuitry configured 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 respective ones of a plurality of measurement intervals; 
 provide, over a first portion of a measurement interval, an operative current to a respective LED element of the plurality of LED elements 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 an illumination emitted by the respective LED element contemporaneous with maintaining the operative current to the respective LED element; 
 provide, over a second portion of a measurement 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 contemporaneous with maintaining the non-operative current to the respective LED element; and 
 determine the drive current to achieve the target luminous flux from the respective LED element based on the first photocurrent and the second photocurrent.  
   
     
     
       37. The controller of  claim 36 , wherein to determine the drive current to achieve the target luminous flux from the respective LED element based on the first photocurrent and the second photocurrent, the LED lighting control circuitry is further configured to:
 subtract the second photocurrent from the first photocurrent to determine the drive current to achieve the target luminous flux from the respective LED element.    
     
     
       38. The controller of  claim 36 , the LED lighting control circuitry configured to further:
 detect a plurality of first photocurrents at each respective one of a plurality of operative currents;   detect a plurality of second photocurrents at each respective one of a plurality of non-operative currents; and   determine a plurality of drive currents to achieve a plurality of target luminous flux outputs from the respective LED element by subtracting respective ones of the plurality of second photocurrents from respective ones of the plurality of first photocurrents.    
     
     
       39. The controller of  claim 38 :
 wherein, to detect the plurality of first photocurrents at each respective one of the plurality of operative currents, the LED lighting control circuitry configured to:
 detect respective ones of the plurality of first photocurrents at each of: a 10% operative current; a 30% operative current; and a 100% operative current; and 
   wherein, to detect the plurality of second photocurrents at each respective one of the plurality of operative currents, the LED lighting control circuitry configured to:
 detect respective ones of the plurality of second photocurrents corresponding to each of: the 10% operative current; the 30% operative current; and the 100% operative current.  
   
     
     
       40. The controller of  claim 36 :
 wherein to provide, over the first portion of a measurement interval, the operative current to the respective LED element, the LED lighting control circuitry configured to:
 provide, over at least a portion of a first measurement interval, the operative current to the respective LED element; and 
   wherein to provide, over the second portion of a measurement interval, the non-operative current to the respective LED element, the LED lighting control circuitry to:
 provide, over at least a portion of a second measurement interval, the non-operative current to the respective LED element.  
   
     
     
       41. The controller of  claim 40 , wherein the first measurement interval and the second measurement interval include a respective plurality of sequential portions of measurement intervals.  
     
     
       42. The controller of  claim 36 , the LED lighting control circuitry configured to further:
 determine the drive current to achieve the target luminous flux output from the respective LED element by detecting the first photocurrent and detecting the second photocurrent responsive to a detected change in one or more ambient conditions.    
     
     
       43. The controller of  claim 42 , the LED lighting control circuitry configured to:
 determine the drive current to achieve the target luminous flux output from the respective LED element by detecting the first photocurrent and detecting the second photocurrent responsive to a detected change in ambient temperature.    
     
     
       44. The controller of  claim 36 , wherein to detect the first photocurrent induced in the at least one photodetector by the illumination emitted by the respective LED element, the LED lighting control circuitry configured to:
 detect the first photocurrent induced in a first photodetector by the illumination emitted by the respective LED element.    
     
     
       45. The controller of  claim 44 , wherein to detect the second photocurrent induced in the at least one photodetector by the ambient illumination, the LED lighting control circuitry configured to:
 detect the second photocurrent induced in a second photodetector by the ambient illumination, the second photodetector different than the first photodetector.    
     
     
       46. The controller of  claim 44 , wherein to detect the second photocurrent induced in the at least one photodetector by the ambient illumination, the LED lighting control circuitry configured to:
 detect the second photocurrent induced in the first photodetector by the ambient illumination level.    
     
     
       47. The controller of  claim 36 , the LED lighting control circuitry configured to further:
 store data representative of the drive current for the respective LED element in memory circuitry communicatively coupled to the LED lighting control circuitry.    
     
     
       48. A non-transitory, machine-readable, storage device that includes instructions that, when executed by light-emitting diode (LED) lighting control circuitry, cause the LED lighting control circuitry to:
 provide an operative current to a plurality of light emitting diode (LED) elements for each of a plurality of sequential illumination intervals, each of the plurality of sequential illumination intervals spaced apart by respective ones of a plurality of measurement intervals; and   provide, over a first portion of a measurement interval, an operative current to a respective LED element of the plurality of LED elements 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 an illumination emitted by the respective LED element contemporaneous with maintaining the operative current to the respective LED element;   provide, over a second portion of a measurement 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 contemporaneous with maintaining the non-operative current to the respective LED element; and   determine a drive current to achieve a target luminous flux from the respective LED element based on the first photocurrent and the second photocurrent.    
     
     
       49. The non-transitory, machine-readable, storage device of  claim 48 , wherein the instructions that cause the LED lighting control circuitry to determine the drive current to achieve the target luminous flux from the respective LED element based on the first photocurrent and the second photocurrent, further cause the LED lighting control circuitry to:
 subtract the second photocurrent from the first photocurrent to determine the drive current to achieve the target luminous flux from the respective LED element.    
     
     
       50. The non-transitory, machine-readable, storage device of  claim 48 , wherein the instructions further cause the LED lighting control circuitry to:
 detect a plurality of first photocurrents at each respective one of a plurality of operative currents;   detect a plurality of second photocurrents at each respective one of a plurality of non-operative currents; and   determine a plurality of drive currents to achieve a plurality of target luminous flux outputs from the respective LED element by subtracting respective ones of the plurality of second photocurrents from respective ones of the plurality of first photocurrents.    
     
     
       51. The non-transitory, machine-readable, storage device of  claim 50 , wherein the instructions that cause the LED lighting control circuitry to detect the plurality of first photocurrents at each respective one of the plurality of operative currents, further cause the LED lighting control circuitry to:
 detect respective ones of the plurality of first photocurrents at each of: a 10% operative current; a 30% operative current; and a 100% operative current; and   wherein the instructions that cause the LED lighting control circuitry to detect the plurality of second photocurrents at each respective one of the plurality of non-operative currents, further cause the LED lighting control circuitry to:   detect respective ones of the plurality of second photocurrents corresponding to each of: the 10% operative current; the 30% operative current; and the 100% operative current.    
     
     
       52. The non-transitory, machine-readable, storage device of  claim 50 :
 wherein the instructions that cause the LED lighting control circuitry to detect the plurality of first photocurrents at each respective one of the plurality of operative currents further cause the LED lighting control circuitry to:
 detect the plurality of first photocurrents at each respective one of the plurality of operative currents over a corresponding plurality of sequential measurement intervals; and 
   wherein the instructions that cause the LED lighting control circuitry to detect the plurality of second photocurrents at each respective one of the plurality of non-operative currents further cause the LED lighting control circuitry to:
 detect the plurality of second photocurrents at each respective one of the plurality of non-operative currents over the corresponding plurality of sequential measurement intervals.  
   
     
     
       53. The non-transitory, machine-readable, storage device of  claim 48 :
 wherein the instructions that cause the LED lighting control circuitry to provide, over the first portion of a measurement interval, the operative current to the respective LED element, further cause the LED lighting control circuitry to:
 provide, over a first portion of a first measurement interval, the operative current to the respective LED element; and 
   wherein the instructions that cause the LED lighting control circuitry to provide, over the second portion of a measurement interval, the non-operative current to the respective LED element, further cause the LED lighting control circuitry to:
 provide, over a second portion of the first measurement interval, the non-operative current to the respective LED element.  
   
     
     
       54. The non-transitory, machine-readable, storage device of  claim 48 , wherein the instructions cause the LED lighting control circuitry to further:
 determine the drive current to achieve the target luminous flux output from the respective LED element by detecting the first photocurrent and detecting the second photocurrent responsive to a detected change in one or more ambient conditions.    
     
     
       55. The non-transitory, machine-readable, storage device of  claim 54 , wherein the instructions that cause the LED lighting control circuitry to determine the drive current to achieve the target luminous flux output from the respective LED element responsive to a detected change in one or more ambient conditions, further cause the LED lighting control circuitry to:
 determine the drive current to achieve the target luminous flux output from the respective LED element responsive to a detected change in ambient temperature.    
     
     
       56. The non-transitory, machine-readable, storage device of  claim 48 , wherein the instructions that cause the LED lighting 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 LED lighting control circuitry to:
 detect the first photocurrent induced in a first photodetector by the illumination emitted by the respective LED element.    
     
     
       57. The non-transitory, machine-readable, storage device of  claim 56 , wherein the instructions that cause the LED lighting control circuitry to detect the second photocurrent induced in the at least one photodetector by the ambient illumination, further cause the LED lighting control circuitry to:
 detect the second photocurrent induced in a second photodetector by the ambient illumination, the second photodetector different than the first photodetector.    
     
     
       58. The non-transitory, machine-readable, storage device of  claim 56 , wherein the instructions that cause the LED lighting control circuitry to detect the second photocurrent induced in the at least one photodetector by the ambient illumination, further cause the LED lighting control circuitry to:
 detect the second photocurrent induced in the first photodetector by the ambient illumination.    
     
     
       59. The non-transitory, machine-readable, storage device of  claim 48 , wherein the instructions cause the LED lighting control circuitry to further:
 store data representative of the drive current for the respective LED element in memory circuitry communicatively coupled to controller circuitry.    
     
     
       60. The method of  claim 25 :
 wherein detecting the plurality of first photocurrents at each respective one of the plurality of operative currents further comprises:
 detecting the plurality of first photocurrents at each respective one of the plurality of operative currents over a corresponding plurality of sequential measurement intervals; and 
   wherein detecting the plurality of second photocurrents at each respective one of the plurality of non-operative currents further comprises:
 detecting the plurality of second photocurrents at each respective one of the plurality of non-operative currents over the corresponding plurality of sequential measurement intervals.  
   
     
     
       61. The method of  claim 23 , further comprising:
 detecting a plurality of first photocurrents at each respective one of a plurality of operative currents; and   determining a plurality of drive currents to achieve a plurality of target luminous flux outputs from the respective LED element by subtracting the second photocurrent from each of the plurality of first photocurrents.    
     
     
       62. The method of  claim 61 :
 wherein detecting a plurality of first photocurrents at each respective one of a plurality of operative currents comprises:
 detecting respective ones of the plurality of first photocurrents at each of: a 10% operative current; a 30% operative current; and a 100% operative current.  
   
     
     
       63. The method of  claim 61 :
 wherein detecting the plurality of first photocurrents at each respective one of the plurality of operative currents comprises:
 detecting the plurality of first photocurrents at each respective one of the plurality of operative currents over a corresponding plurality of sequential measurement intervals.  
   
     
     
       64. The controller of  claim 38 :
 wherein, to detect the plurality of first photocurrents at each respective one of the plurality of operative currents, the LED lighting control circuitry configured to:
 detect the plurality of first photocurrents at each respective one of the plurality of operative currents over a corresponding plurality of sequential measurement intervals; and 
   wherein, to detect the plurality of second photocurrents at each respective one of the plurality of non-operative currents, the LED lighting control circuitry configured to:
 detect the plurality of second photocurrents at each respective one of the plurality of non-operative currents over the corresponding plurality of sequential measurement intervals.  
   
     
     
       65. The controller of  claim 36 :
 wherein to provide, over the first portion of a measurement interval, the operative current to the respective LED element, the LED lighting control circuitry configured to:
 provide, over at least a portion of a first measurement interval, the operative current to the respective LED element; and 
   wherein to provide, over the second portion of a measurement interval, the non-operative current to the respective LED element, the LED lighting control circuitry to:
 provide, over at least a portion of the first measurement interval, the non-operative current to the respective LED element.  
   
     
     
       66. The controller of  claim 36 , the LED lighting control circuitry configured to further:
 detect a plurality of first photocurrents at each respective one of a plurality of operative currents; and   determine a plurality of drive currents to achieve a plurality of target luminous flux outputs from the respective LED element by subtracting the second photocurrent from each of the plurality of first photocurrents.    
     
     
       67. The controller of  claim 66 :
 wherein, to detect the plurality of first photocurrents at each respective one of the plurality of operative currents, the LED lighting control circuitry configured to:
 detect respective ones of the plurality of first photocurrents at each of: a 10% operative current; a 30% operative current; and a 100% operative current.  
   
     
     
       68. The controller of  claim 66 :
 wherein, to detect the plurality of first photocurrents at each respective one of the plurality of operative currents, the LED lighting control circuitry configured to:
 detect the plurality of first photocurrents at each respective one of the plurality of operative currents over a corresponding plurality of sequential measurement intervals.  
   
     
     
       69. The non-transitory, machine-readable, storage device of  claim 48 :
 wherein the instructions that cause the LED lighting control circuitry to provide, over the first portion of a measurement interval, the operative current to the respective LED element, further cause the LED lighting control circuitry to:
 provide, over a first portion of a first measurement interval, the operative current to the respective LED element; and 
   wherein the instructions that cause the LED lighting control circuitry to provide, over the second portion of a measurement interval, the non-operative current to the respective LED element, further cause the LED lighting control circuitry to:
 provide, over a second portion of a second measurement interval, the non-operative current to the respective LED element.  
   
     
     
       70. The non-transitory, machine-readable, storage device of  claim 64 , wherein the first measurement interval and the second measurement interval include a respective plurality of sequential portions of measurement intervals.  
     
     
       71. The non-transitory, machine-readable, storage device of  claim 48 , wherein the instructions further cause the LED lighting control circuitry to:
 detect a plurality of first photocurrents at each respective one of a plurality of operative currents; and determine a plurality of drive currents to achieve a plurality of target luminous flux outputs from the respective LED element by subtracting the second photocurrent from each of the plurality of first photocurrents.    
     
     
       72. The non-transitory, machine-readable, storage device of  claim 71 , wherein the instructions that cause the LED lighting control circuitry to detect the plurality of first photocurrents at each respective one of the plurality of operative currents, further cause the LED lighting control circuitry to:
 detect respective ones of the plurality of first photocurrents at each of: a 10% operative current; a 30% operative current; and a 100% operative current.    
     
     
       73. The non-transitory, machine-readable, storage device of  claim 71 , wherein the instructions that cause the LED lighting control circuitry to detect the plurality of first photocurrents at each respective one of the plurality of operative currents, further cause the LED lighting control circuitry to:
 detect the plurality of first photocurrents at each respective one of the plurality of operative currents over a corresponding plurality of sequential measurement intervals.