WO2016057089A1 - Compensation résistant aux interférences dans des dispositifs d'éclairage comprenant des diodes électroluminescentes - Google Patents

Compensation résistant aux interférences dans des dispositifs d'éclairage comprenant des diodes électroluminescentes Download PDF

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Publication number
WO2016057089A1
WO2016057089A1 PCT/US2015/035081 US2015035081W WO2016057089A1 WO 2016057089 A1 WO2016057089 A1 WO 2016057089A1 US 2015035081 W US2015035081 W US 2015035081W WO 2016057089 A1 WO2016057089 A1 WO 2016057089A1
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WO
WIPO (PCT)
Prior art keywords
measurement
photocurrent
detection
intervals
illumination
Prior art date
Application number
PCT/US2015/035081
Other languages
English (en)
Inventor
Horace C. Ho
Rebecca Frank
Original Assignee
Ketra, Inc.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from US14/510,243 external-priority patent/US9247605B1/en
Priority claimed from US14/510,212 external-priority patent/US9155155B1/en
Priority claimed from US14/510,266 external-priority patent/US9345097B1/en
Priority claimed from US14/510,283 external-priority patent/US9332598B1/en
Application filed by Ketra, Inc. filed Critical Ketra, Inc.
Publication of WO2016057089A1 publication Critical patent/WO2016057089A1/fr

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Classifications

    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
    • H05B45/20—Controlling the colour of the light
    • H05B45/22—Controlling the colour of the light using optical feedback
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
    • H05B45/10—Controlling the intensity of the light
    • H05B45/12—Controlling the intensity of the light using optical feedback
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B47/00—Circuit arrangements for operating light sources in general, i.e. where the type of light source is not relevant
    • H05B47/10—Controlling the light source
    • H05B47/105—Controlling the light source in response to determined parameters
    • H05B47/11—Controlling the light source in response to determined parameters by determining the brightness or colour temperature of ambient light
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
    • H05B45/10—Controlling the intensity of the light
    • H05B45/18—Controlling the intensity of the light using temperature feedback
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
    • H05B45/50—Circuit arrangements for operating light-emitting diodes [LED] responsive to malfunctions or undesirable behaviour of LEDs; responsive to LED life; Protective circuits
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
    • Y02B20/00—Energy efficient lighting technologies, e.g. halogen lamps or gas discharge lamps
    • Y02B20/40—Control techniques providing energy savings, e.g. smart controller or presence detection

Definitions

  • This invention relates to illumination devices and, more particularly, to illumination devices comprising a plurality of light emitting diode (LED) elements and to interference- resistant methods for monitoring and adjusting the illumination devices during operation.
  • LED light emitting diode
  • LEDs light emitting diodes
  • LEDs provide a number of advantages over traditional light sources such as incandescent and fluorescent light bulbs, including low power consumption, long lifetime, lack of hazardous materials, and additional specific advantages for different applications.
  • LEDs provide the opportunity to adjust the color (e.g., from white, to blue, to green, etc.) or the color temperature (e.g., from "warm white” to "cool white”) to produce different lighting effects.
  • LEDs are rapidly replacing the Cold Cathode Fluorescent Lamps (CCFL)
  • OLEDs organic LEDs
  • LED devices may combine different colors of LEDs within the same package to produce a multi-colored LED emitter module, or lamp.
  • An example of a multi-colored LED device is one in which two or more different colors of LEDs are combined to produce white or near- white light.
  • white light lamps there are many different types of white light lamps on the market, some of which combine red, green and blue (RGB) LEDs, red, green, blue and yellow (RGBY) LEDs, white and red (WR) LEDs, RGBW LEDs, etc.
  • these lamps may be configured to generate white light or near- white light within a wide gamut of color points or color temperatures ranging from "warm white” (e.g., roughly 2600K-3700K), to "neutral white” (e.g., 3700K-5000K) to "cool white” (e.g., 5000K-8300K).
  • warm white e.g., roughly 2600K-3700K
  • neutral white e.g., 3700K-5000K
  • cool white e.g., 5000K-8300K
  • LEDs have many advantages over conventional light sources, a disadvantage of LEDs is that their output characteristics tend to vary over temperature, process and time. For example, it is generally known that the luminous flux, or the perceived power of light emitted by an LED, is directly proportional to the drive current supplied thereto. In many cases, the luminous flux of an LED is controlled by increasing/decreasing the drive current supplied to the LED to correspondingly increase/decrease the luminous flux. However, the luminous flux generated by an LED for a given drive current does not remain constant over temperature and time, and gradually decreases with increasing temperature and as the LED ages over time.
  • the luminous flux tends to vary from batch to batch, and even from one LED to another in the same batch, due to process variations.
  • LED manufacturers try to compensate for process variations by sorting or binning the LEDs based on factory measured characteristics, such as chromaticity (or color), luminous flux and forward voltage.
  • binning alone cannot compensate for changes in LED output characteristics due to aging and temperature fluctuations during use of the LED device.
  • such adjustment may involve compensation measurements of one or more LED elements within a lamp. Interference from a nearby lamp can cause errors in such measurements for a given lamp, potentially resulting in incorrect compensation for the lamp. It would therefore be desirable to develop interference-resistant compensation methods for LED illumination devices, and illumination devices incorporating such methods.
  • Various methods are provided herein for controlling an illumination device or a lamp comprising multiple emission light emitting diodes (LED) elements.
  • the methods disclosed herein may be used for avoiding interference-related errors when compensating individual LEDs in an illumination device for variations in quantities, such as drive current and temperature.
  • Improved illumination devices are also provided herein with control circuits adapted to perform steps of the methods described herein.
  • the disclosed illumination devices may, in certain embodiments, include one or more emitter modules, which may also be called “lamps.”
  • An “emitter module” may be generally described as having a plurality of LED elements and one or more photodetectors combined into a package.
  • LED element refers to either a single LED or a chain of serially connected LEDs supplied with the same drive current.
  • emission LED element is an LED element configured for light emission, as opposed to, for example, an LED configured as a light detector or
  • the method may allow a sequence of measurements performed by one lamp to overlap with a sequence of measurements performed by another lamp, while avoiding errors in the measurements and resulting LED adjustments.
  • An embodiment of such a method includes operating one or more of the emission LED elements within a lamp at a respective substantially continuous drive current sufficient to produce illumination, while bringing all of the LED elements to a level insufficient to produce illumination for the duration of multiple detection intervals interspersed with periods of illumination by the lamp.
  • Such an embodiment may further include monitoring a detection photocurrent induced in a detection interval photodetector within the lamp during at least a portion of each of the multiple detection intervals.
  • the method includes detecting, for at least one of the multiple detection intervals, that the monitored detection photocurrent varies substantially with time. Such an embodiment may further include initiating a sequence of measurements subsequent to detecting that the monitored photocurrent varies substantially with time, where the sequence includes multiple measurements taken during multiple corresponding measurement intervals.
  • the measurement intervals are interspersed between periods of illumination in a manner similar to the detection intervals.
  • the sequence includes one or more sensitive measurements in which photocurrent is detected and one or more non-sensitive measurements in which photocurrent is not detected.
  • the sensitive measurements in the sequence may be performed during measurement intervals during which external illumination sufficient to induce a detection photocurrent that varies substantially with time is not incident upon the lamp.
  • at least one non-sensitive measurement in the sequence is performed during a measurement interval during which external illumination sufficient to induce a detection photocurrent that varies substantially with time is incident upon the lamp.
  • Initiating a sequence of measurements may in some embodiments include bringing the respective drive current of each of the LED elements within the lamp to a level insufficient to produce illumination for the duration of each measurement interval in which a non-sensitive measurement is performed. Initiating the sequence of measurements may in some embodiments further include bringing the respective drive current of each of the LED elements within the lamp, except for a single LED element subject to a photocurrent measurement, to a level insufficient to produce illumination for the duration of each measurement interval in which a sensitive measurement is performed.
  • the monitored detection photocurrent varies substantially with time in response to external illumination incident upon the lamp
  • the external illumination sufficient to induce such a variation of detection photocurrent is produced by a measurement within an additional sequence of measurements performed by an additional lamp
  • the additional sequence of measurements includes one or more interfering measurements producing illumination sufficient to induce within the lamp a detection photocurrent that varies substantially with time and one or more non-interfering measurements not producing illumination sufficient to induce within the lamp a detection photocurrent that varies substantially with time.
  • initiating a sequence of measurements may include performing a first measurement in the sequence during an initial measurement interval, and the method may further include selecting the initial measurement interval such that the sensitive measurements in the sequence are performed during measurement intervals in which external illumination sufficient to induce a detection photocurrent that varies substantially with time is not incident upon the lamp.
  • selecting the initial measurement interval includes determining an order of interfering and non-interfering measurements in the additional sequence of measurements and predicting which upcoming measurement intervals will contain interfering measurements from among the additional sequence of measurements.
  • determining an order of interfering and non-interfering measurements further includes taking into account a number of detection intervals in which the monitored detection photocurrent has varied substantially with time during a current detection sequence.
  • determining an order of interfering and non-interfering measurements further includes taking into account a number of consecutive detection intervals in which the monitored detection photocurrent has not varied substantially with time since the most recent detection interval in which the monitored detection photocurrent did vary substantially with time. Taking into account a number of consecutive detection intervals in which the monitored detection photocurrent has not varied substantially with time may in some embodiments include referencing a contiguous free interval counter stored within the lamp.
  • determining an order of interfering and non-interfering measurements may further include repeating monitoring of the detection photocurrent induced in a detection interval photodetector within the lamp during at least a portion of an additional detection interval.
  • the determining of the order may further include taking into account any changes in the numbers of detection intervals in which the monitored detection photocurrent has or has not varied substantially with time and in the number of consecutive detection intervals in which the monitored detection photocurrent has not varied substantially with time.
  • the sequence of measurements typically initiated by the lamp has a default measurement order. In such an embodiment, the method may further include altering an order of measurements in the sequence from the default measurement order to a revised measurement order prior to initiating the sequence of measurements.
  • an illumination device including a lamp is contemplated herein.
  • the lamp includes multiple LED elements, one or more photodetectors, a storage medium adapted for storing a data structure of configuration information, and a lamp control circuit operably coupled to the multiple emission LED elements, the one or more photodetectors, and the storage medium.
  • the configuration information includes ordering of sensitive and non-sensitive measurements within a sequence of compensation measurements that the lamp is configured to perform and ordering of interfering and non-interfering measurements within an additional sequence of measurements that an additional lamp is configured to perform.
  • the control circuit may be adapted to initiate the sequence of compensation measurements.
  • the sensitive measurements include measurements in which photocurrent is detected and interfering measurements include measurements producing illumination.
  • the lamp control circuit is further adapted to, prior to initiating the sequence of compensation measurements, operate one or more of the multiple emission LED elements at a respective substantially continuous drive current to produce illumination, bring to a level insufficient to produce illumination the respective drive current of each of the emission LED elements for the duration of each of multiple detection intervals interspersed with periods of said illumination, monitor a detection photocurrent induced in a detection interval
  • the storage medium may further include a collision counter, a free interval counter, and a contiguous free interval counter.
  • the collision counter is configured to store a number of detection intervals in which the monitored detection photocurrent has varied substantially with time during a current detection sequence.
  • the free interval counter is configured to store a number of detection intervals in which the monitored detection
  • the contiguous free interval counter is configured to store a number of consecutive detection intervals in which the monitored detection photocurrent has not varied substantially with time since the most recent detection interval in which the monitored detection photocurrent did vary substantially with time.
  • the lamp includes multiple emission LED elements, one or more photodetectors, and a lamp control circuit operably coupled to the multiple emission LED elements and the one or more photodetectors.
  • the lamp control circuit is adapted to operate one or more of the multiple emission LED elements at a respective substantially continuous drive current to produce illumination, bring to a level insufficient to produce illumination the respective drive current of each of the emission LED elements for the duration of each of multiple detection intervals interspersed with periods of said illumination, monitor a detection photocurrent induced in a detection interval photodetector during at least a portion of each of the multiple detection intervals, determine whether the monitored detection current varies substantially with time, and in the event that the monitored detection current does vary substantially with time for at least one of the multiple detection intervals, initiate a sequence of measurements.
  • the sequence of measurements includes multiple measurements taken during multiple corresponding
  • the sequence includes one or more sensitive measurements in which photocurrent is detected and one or more non- sensitive measurements in which photocurrent is not detected.
  • the sensitive measurements in the sequence may be performed during measurement intervals during which external illumination sufficient to induce a detection photocurrent that varies substantially with time is not incident upon the lamp.
  • At least one of the non-sensitive measurements in the sequence may be performed during a measurement interval during which external illumination sufficient to induce a detection photocurrent that varies substantially with time is incident upon the lamp.
  • the lamp control circuit is further adapted to perform a first measurement in the sequence during an initial measurement interval, and to select the initial measurement interval such that the sensitive measurements in the sequence are performed during measurement intervals in which external illumination sufficient to induce a detection photocurrent that varies substantially with time is not incident upon the lamp.
  • the external illumination sufficient to induce a detection photocurrent that varies substantially with time is produced by a measurement within an additional sequence of measurements performed by an additional lamp.
  • the additional sequence may include one or more interfering measurements producing illumination sufficient to induce within the lamp a detection photocurrent that varies
  • the lamp control circuit in such an embodiment may be further adapted to select the initial measurement interval such that the sensitive measurements in the sequence are performed during measurement intervals in which interfering measurements are not performed by the additional device.
  • the lamp control circuit is further adapted to determine an order of interfering and non-interfering measurements in the additional sequence of measurements and predict which upcoming measurement intervals will contain interfering measurements from the additional sequence of measurements.
  • the lamp may further include a storage medium operably coupled to the lamp control circuit and configured to store a data structure containing configuration information.
  • the configuration information may in an embodiment include ordering of interfering and non- interfering measurements within the additional sequence of measurements that the additional lamp is configured to perform.
  • the lamp control circuit may be further adapted to reference the configuration information.
  • a method includes operating one or more of the emission LED elements within a lamp at a respective substantially continuous drive current sufficient to produce illumination, while bringing all of the LED elements to a level insufficient to produce illumination for the duration of each of multiple detection intervals interspersed with periods of illumination by the lamp.
  • Such an embodiment may further include monitoring a detection photocurrent induced in a detection interval photodetector within the lamp during at least a portion of each of the multiple detection intervals.
  • the method includes bringing to a level insufficient to produce illumination the respective drive current of all except a first one of the emission LED elements within the lamp for the duration of a first measurement interval occurring subsequent to the multiple detection intervals.
  • the method may further include applying a first drive current sufficient to produce illumination to the first one of the emission LED elements during the first measurement interval, and monitoring a measurement photocurrent induced in a first measurement photodetector within the lamp while the first drive current is applied.
  • the multiple detection intervals and the first measurement interval are within a first periodic series of intervals separated by a first offset from a periodic timing reference.
  • the multiple detection intervals are within a first periodic series of intervals separated by a first offset from a periodic timing reference and the first measurement interval is within a second periodic series of intervals separated by a second offset from the periodic timing reference.
  • the method includes bringing to a level insufficient to produce illumination the respective drive current of all except a second one of the emission LED elements within the lamp for the duration of a second measurement interval occurring subsequent to the multiple detection intervals.
  • the method may further include applying a second drive current sufficient to produce illumination to the second one of the emission LED elements during the second measurement interval, and monitoring a measurement photocurrent induced in a second measurement photodetector within the lamp while the second drive current is applied.
  • the second measurement photodetector is the same photodetector as the first measurement photodetector.
  • the method further includes determining, for at least one of the multiple detection intervals, that a magnitude of the monitored detection photocurrent does not vary substantially with time during the portion of the detection interval that the photocurrent is monitored.
  • a determination that the magnitude of the detection photocurrent monitored in a detection interval does not vary substantially with time indicates in some embodiments that the detection interval is a free detection interval.
  • the method may further include determining that a predetermined number of free detection intervals has occurred, and applying the first drive current during the first measurement interval may be in response to a determination that the predetermined number of free detection intervals has occurred.
  • the method further includes determining, for at least one of the multiple detection intervals, that a magnitude of the monitored detection photocurrent does vary substantially with time during the portion of the detection interval that the photocurrent is monitored.
  • the method may further include, in response to the determination that the magnitude of the monitored detection photocurrent varies substantially with time, repeating the detection sequence that includes bringing to a level insufficient to produce illumination the respective drive current of each of the emission LED elements for the duration of each of multiple detection intervals and monitoring the photocurrent induced in the detection interval photodetector during at least a portion of each of the multiple detection intervals.
  • the method may also include waiting for a delay time before repeating the detection sequence.
  • the delay time may in some embodiments be a randomized delay time.
  • the multiple detection intervals are within a series of periodic intervals, and the method further includes shifting a phase of the series of periodic intervals relative to a timing reference before repeating the detection sequence.
  • the method may also include determining that a predetermined number of collisions has occurred, where a collision includes a determination that a magnitude of the monitored detection photocurrent varies substantially with time. Shifting the phase of the series of periodic intervals may in some embodiments be done in response to a determination that the predetermined number of collisions has occurred.
  • an illumination device including a lamp
  • the lamp includes multiple emission LED elements, one or more photodetectors, and a lamp control circuit operably coupled to the multiple emission LED elements and the one or more photodetectors.
  • the lamp control circuit is adapted to operate one or more of the multiple emission LED elements at a respective substantially continuous drive current to produce illumination, bring to a level insufficient to produce illumination the respective drive current of each of the emission LED elements for the duration of each of multiple detection intervals interspersed with periods of said illumination and monitor a detection photocurrent induced in a detection interval photodetector during at least a portion of each of the multiple detection intervals.
  • the lamp control circuit is further adapted to bring to a level insufficient to produce illumination the respective drive current of all except a first one of the emission LED elements for the duration of a first measurement interval occurring subsequent to the multiple detection intervals, apply a first drive current sufficient to produce illumination to the first one of the emission LED elements during the first measurement interval, and monitor a measurement photocurrent induced in a first measurement photodetector while the first drive current is applied.
  • the detection interval photodetector and the first measurement photodetector comprise the same photodetector.
  • the first measurement photodetector comprises an LED configured for detection.
  • the lamp control circuit is further adapted to determine whether a magnitude of the monitored detection photocurrent varies substantially with time. A determination that the magnitude of the detection photocurrent monitored in a detection interval does not vary substantially with time indicates in some embodiments that the detection interval is a free detection interval.
  • the lamp control circuit may be further adapted to determine whether a predetermined number of free detection intervals has occurred, and to apply the first drive current during the first measurement interval is in response to a determination that the predetermined number of free detection intervals has occurred.
  • the lamp control circuit is further adapted to, in response to a determination that the magnitude of the monitored detection photocurrent varies substantially with time, repeat a detection sequence of the lamp by again bringing to a level insufficient to produce illumination the respective drive current of each of the emission LED elements for the duration of each of multiple detection intervals, and again monitoring he detection photocurrent induced in the detection interval photodetector during at least a portion of each of the multiple detection intervals.
  • the illumination device further includes a delay generator operably coupled to the lamp control circuit and adapted to generate a delay time.
  • the delay generator is adapted to generate a randomized delay time.
  • the lamp control circuit is adapted to wait for a delay time prior to repeating the detection sequence of the lamp.
  • the illumination device includes a timing reference generator operatively coupled to the lamp control circuit and adapted to generate a periodic timing reference.
  • the lamp control circuit may be further adapted to generate the multiple detection intervals within a series of periodic intervals synchronized to the timing reference and to shift a phase of the series of periodic intervals relative to the timing reference prior to repeating the detection sequence of the lamp.
  • the lamp control circuit is further adapted to determine whether a predetermined number of collisions has occurred, where a collision comprises a determination that the magnitude of the monitored detection photocurrent varies substantially with time.
  • the lamp control circuit may further be adapted to shift the phase of the series of periodic intervals in response to a determination that the predetermined number of collisions has occurred.
  • a method includes operating one or more of the multiple emission LED elements at a respective substantially continuous drive current sufficient to produce illumination, bringing to a level insufficient to produce illumination the respective drive current of all except one of the emission LED elements within the illumination device for the duration of a first measurement interval, and bringing to a level insufficient to produce illumination the respective drive current of all except one of the emission LED elements for the duration of a second measurement interval subsequent to the first measurement interval.
  • the first measurement interval is one of a first series of measurement intervals interspersed with periods of operating the emission LED elements to produce illumination
  • the second measurement interval is one of a second series of measurement intervals interspersed with periods of operating the emission LED elements to produce illumination.
  • the first series of measurement intervals and second series of measurement intervals are separated by respective first and second offsets from a timing reference.
  • the method further includes discontinuing use of the first series of measurement intervals at a time subsequent to the end of the first measurement interval.
  • the method may further include applying a drive current sufficient to produce illumination to one of the emission LED elements during each of the first and second
  • the method also includes determining that a result of monitoring the measurement photocurrent during the first measurement interval is outside of an expected range. In an embodiment, this determining includes comparing the result to a previously stored result. In another embodiment, bringing to a level insufficient to produce illumination the respective drive current of all except one of the emission LED elements for the duration of the second measurement interval is in response to the determination that the result of monitoring the measurement photocurrent during the first measurement interval is outside of the expected range.
  • the method also includes, in response to the determination that the result of monitoring the 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, applying the drive current sufficient to produce illumination to the one of the emission LED elements and said monitoring the measurement photocurrent induced in the measurement photodetector.
  • the method may further include determining whether a predetermined number of out-of-range measurements using the first series of measurement intervals has occurred. In such an embodiment, bringing to a level insufficient to produce illumination the respective drive current of all except one of the emission LED elements for the duration of a second measurement interval may be in response to a determination that the predetermined number of out-of-range measurements using the first series of measurement intervals has occurred.
  • the method includes, for each of the first and second measurement intervals, bringing the drive current applied to the one of the emission LED elements to a level 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
  • the method may further include monitoring a background photocurrent induced in the measurement photodetector during the portion of the measurement interval with the drive currents of all of the emission LED elements at a level insufficient to produce illumination, and subtracting the background photocurrent from the measurement photocurrent.
  • the result of monitoring a measurement photocurrent during the first measurement interval includes a result of subtracting the background photocurrent from the measurement photocurrent for the first measurement interval.
  • an illumination device in addition to the method embodiments described above, is contemplated herein.
  • the device includes multiple emission LED elements, one or more photodetectors, and a control circuit operably coupled to the multiple emission LED elements and the one or more photodetectors.
  • the control circuit is adapted to operate one or more of the multiple emission LED elements at a respective substantially continuous drive current to produce illumination, bring to a level insufficient to produce illumination the respective drive current of all except one of the emission LED elements within the illumination device for the duration of a first measurement interval, and bring to a level insufficient to produce illumination the respective drive currents of all except one of the emission LED elements for the duration of a second measurement interval subsequent to the first measurement interval.
  • the first measurement interval is one of a first series of measurement intervals interspersed with periods of operating the emission LED elements to produce illumination
  • the second measurement interval is one of a second series of measurement intervals interspersed with periods of operating the emission LED elements to produce illumination.
  • the first series of measurement intervals and second series of measurement intervals are separated by respective first and second offsets from a timing reference.
  • the illumination device also includes a timing reference generator operatively coupled to the control circuit and adapted to generate a periodic timing reference.
  • the control circuit may be 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.
  • the control circuit is adapted to discontinue use of the first series of measurement intervals at a time subsequent to the end of the first measurement interval.
  • the illumination device also includes an LED driver and receiver circuit operably coupled to the multiple emission LED elements, the one or more photodetectors, and the control circuit.
  • the control circuit is adapted to use the LED driver and receiver circuit to adjust the respective drive currents of the emission LED elements.
  • the control circuit is adapted to use the LED driver and receiver circuit to, during each of said first measurement interval and said second measurement interval, bring to a level insufficient to produce illumination the respective drive currents of all except one of the emission LED elements, apply a drive current sufficient to produce
  • 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.
  • the control circuit may also be adapted to bring to a level insufficient to produce illumination the respective drive currents of all except one of the emission LED elements for the duration of the second measurement interval in response to a determination that the result is outside of the expected range.
  • the illumination device also includes a storage medium operably coupled to the control circuit, and 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.
  • 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.
  • the control circuit is further adapted to, for each of the first and second measurement intervals, bring the drive current applied to the one of the emission LED elements to a level 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 level insufficient to produce illumination for the portion of the measurement interval.
  • the control circuit may further be adapted to 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.
  • 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.
  • a method includes operating one or more of the multiple emission LED elements in each of the multiple emitter modules at a respective substantially continuous drive current sufficient to produce illumination. The method further includes bringing to a level insufficient to produce illumination the respective drive current of all except one of the emission LED elements within a first emitter module of the multiple emitter modules, for the duration of a first measurement interval within a first series of measurement intervals interspersed with periods of illumination. In addition, an embodiment of the method includes bringing to a level insufficient to produce illumination the respective drive current of all except one of the emission LED elements within a second emitter module of the multiple emitter modules, for the duration of a measurement interval within a second series of measurement intervals interspersed with periods of said operating.
  • the first series of measurement intervals and second series of measurement intervals are separated by a respective first offset and second offset from a timing reference.
  • the timing reference comprises a periodic timing signal.
  • the timing reference is derived from an AC mains signal.
  • the multiple emitter modules consist of one or more sets of three emitter modules, and 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.
  • the method may further include, for either of the first or second emitter modules, applying to the one of the emission LED elements a drive current sufficient to produce illumination during the measurement interval within the respective first or second series of measurement intervals, and monitoring a respective first or second measurement photocurrent induced in a respective first or second measurement photodetector within the emitter module while the drive current is applied.
  • the method includes, for either of the first or second emitter modules, bringing the drive current applied to the one of the emission LED elements to a level 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 level insufficient to produce illumination for the portion of the respective measurement interval.
  • the method may further include, for either of the first or second emitter modules and during the portion of the respective measurement interval, monitoring a respective first or second background photocurrent induced in the respective first or second measurement photodetector.
  • the method may further include, for either of the first or second emitter modules, subtracting the respective first or second background photocurrent from the respective first or second measurement photocurrent.
  • the result of this subtraction, for either of the first or second emitter modules is stored as a respective first or second corrected photocurrent.
  • storing a result of the subtraction is in response to a determination that the result is within an expected range.
  • an illumination device in addition to the method embodiments described above, is contemplated herein.
  • the device includes multiple emitter modules, where each emitter module includes multiple emission LED elements and one or more photodetectors.
  • the device further includes a control circuit operably coupled to the multiple emitter modules.
  • the control circuit is adapted to operate one or more of the multiple emission LED elements within each of the multiple emitter modules at a respective substantially continuous drive current to produce illumination.
  • the control circuit is further adapted to bring to a level insufficient to produce illumination the respective drive current of all except one of the emission LED elements within a first emitter module of the multiple emitter modules, for the duration of a measurement interval within a first series of measurement intervals interspersed with periods of illumination.
  • the control circuit is further adapted in such an embodiment to bring to a level insufficient to produce illumination the respective drive currents of all except one of the emission LED elements within a second emitter module of the multiple emitter modules, for the duration of a measurement interval within a second series of measurement intervals interspersed with periods of illumination.
  • the first series of measurement intervals and second series of measurement intervals are separated by a respective first offset and second offset from a timing reference.
  • the illumination device also includes a timing reference generator operatively coupled to the control circuit and adapted to generate the timing reference.
  • the timing reference comprises a periodic timing signal and the timing reference generator comprises a phase-locked loop.
  • the illumination device further includes multiple driver circuits operably coupled to respective emitter modules of the multiple emitter modules and to the control circuit, and 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.
  • control circuit is further adapted to, for each of the first and second emitter modules, apply to the one of the emission LED elements a drive current sufficient to produce illumination during the measurement interval within the respective first or second series of measurement intervals, and monitor a respective first or second measurement photocurrent induced in a respective first or second measurement photodetector within the emitter module during the time the drive current sufficient to produce illumination is applied.
  • control circuit is further adapted to, for each of the first and second emitter modules, bring the drive current applied to the one of the emission LED elements to a level 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 level insufficient to produce illumination for the portion of the respective measurement interval.
  • the control circuit may be further adapted to monitor a respective first or second background photocurrent induced in the respective first or second measurement photodetector during the portion of the respective measurement interval.
  • control circuit is further adapted to, for each of the first and second emitter modules, subtract the respective first or second background photocurrent from the respective first or second measurement photocurrent.
  • the illumination device also includes a plurality of storage locations accessible by the control circuit, and 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.
  • the control circuit is further adapted to determine whether the result of the subtraction is within an expected range and store the result in response to a determination that the result is within an expected range.
  • the control circuit includes a respective module control circuit for each emitter module within the illumination device.
  • control circuit also includes 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.
  • the multiple emitter modules consist of one or more sets of three emitter modules, and 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.
  • Fig. 1 is a graph of the 1931 CIE chromaticity diagram illustrating the gamut of human color perception and the gamut achievable by an illumination device comprising a plurality of multiple color LEDs (e.g., red, green and blue);
  • Fig. 2 is a graph illustrating the non-linear relationship between relative luminous flux and junction temperature for white, blue and green LEDs
  • Fig. 3 is a graph illustrating the substantially more non-linear relationship between relative luminous flux and junction temperature for red, red-orange and yellow (amber) LEDs;
  • Fig. 4 is a graph illustrating the non-linear relationship between relative luminous flux and drive current for red and red-orange LEDs
  • Fig. 5 is a graph illustrating the substantially more non-linear relationship between relative luminous flux and drive current for white, blue and green LEDs
  • Fig. 6 is an exemplary timing diagram for an illumination device comprising four emission LEDs, illustrating intervals during which emitter forward voltage measurements are obtained from each emission LED, one LED at a time;
  • Fig. 7 is a graphical representation depicting how one or more interpolation
  • technique(s) may be used in a compensation method to determine the drive current needed to produce a desired luminous flux for a given LED using previously-obtained calibration values stored within the illumination device;
  • Fig. 8 is an exemplary timing diagram for an illumination device comprising four emission LEDs and one or more photodetectors, illustrating intervals during which
  • Fig. 9 is a graphical representation depicting how one or more interpolation
  • technique(s) may be used in a compensation method to determine the expected photocurrent value for a given LED using the present forward voltage, the present drive current and previously-obtained calibration values stored within the illumination device;
  • Fig. 10 is an exemplary timing diagram illustrating an embodiment for which the measurement intervals of Fig. 6 or Fig. 8 are within compensation periods occurring relatively infrequently, and for which illumination drive currents are increased during a compensation period to avoid flicker;
  • Fig.11 A is a graph illustrating subtraction of ambient light detected when the measured LED element is turned off
  • Fig. 1 IB is a graph illustrating error that can result from ambient subtraction when a nearby lamp is performing compensation measurements
  • Fig. 12 is an exemplary timing diagram illustrating overlap of compensation measurements by neighboring lamps
  • Fig. 13A is an exemplary timing diagram illustrating a series of detection intervals followed by a series of measurement intervals
  • Fig. 13B is a timing diagram illustrating a series of detection intervals interspersed with intervals for taking non-sensitive measurements, followed by a series of intervals for taking sensitive measurements;
  • Fig. 14 is an exemplary timing diagram illustrating overlapping but non-interfering measurement sequences by neighboring lamps;
  • Fig. 15 is an exemplary timing diagram illustrating a timing reference synchronized to the AC mains, and first and second sets of measurement intervals separated from the timing reference by first and second offset times;
  • Fig. 16A is a flow chart illustrating an exemplary method disclosed for controlling a lamp to perform compensation measurements
  • Fig. 16B is a flow chart illustrating an exemplary method for controlling a lamp to initiate compensation measurements
  • Fig. 16C is a flow chart illustrating another exemplary method for controlling a lamp to initiate compensation measurements
  • Fig. 17 is a chart illustrating exemplary configuration information that may be stored within an illumination device and used in embodiments of methods described herein;
  • Fig. 18A is a photograph of an exemplary multi-lamp illumination device
  • Fig. 18B is a computer generated image showing a top view of an exemplary emitter module, or lamp, that may be included within the exemplary illumination device of Fig. 18 A;
  • Fig. 19A is a photograph of an exemplary illumination device
  • Fig. 19B is a computer generated image showing a top view of an exemplary emitter module, or lamp, that may be included within the exemplary illumination device of Fig. 19A;
  • Fig. 20 is an exemplary block diagram of circuit components that may be included within an embodiment of an illumination device disclosed herein;
  • Fig. 21 is an exemplary block diagram of an embodiment of an LED driver and receiver circuit that may be included within the illumination device of Fig. 20;
  • Fig. 22 is an exemplary block diagram of circuit components that may be included within an embodiment of a multi-lamp illumination device disclosed herein;
  • Fig. 23 is an exemplary block diagram of an embodiment of interface and emitter circuitry that may be included within the illumination device of Fig. 22.
  • An LED generally comprises a chip of semiconducting material doped with impurities to create a p-n junction. As in other diodes, current flows easily from the p-side, or anode, to the n-side, or cathode, but not in the reverse direction.
  • the wavelength of the light emitted by the LED depends on the band gap energy of the materials forming the p-n junction of the LED.
  • Red and yellow LEDs are commonly composed of materials (e.g., AlInGaP) having a relatively low band gap energy, and thus produce longer wavelengths of light. For example, most red and yellow LEDs have a peak wavelength in the range of approximately 610-650 nm and approximately 580-600 nm, respectively.
  • green and blue LEDs are commonly composed of materials (e.g., GaN or InGaN) having a larger band gap energy, and thus, produce shorter wavelengths of light. For example, most green and blue LEDs have a peak wavelength in the range of approximately 515-550 nm and approximately 450-490 nm, respectively.
  • a "white” LED may be formed by covering or coating, e.g., a violet or blue LED having a peak emission wavelength of about 400-490nm with a phosphor (e.g., YAG), which down-converts the photons emitted by the blue LED to a lower energy level, or a longer peak emission wavelength, such as about 525nm to about 600nm.
  • a phosphor e.g., YAG
  • YAG e.g., YAG
  • such an LED may be configured to produce substantially white light having a correlated color temperature (CCT) of about 3000K.
  • CCT correlated color temperature
  • differently colored LEDs may be combined to produce white or near-white light within a wide gamut of color points or CCTs ranging from "warm white” (e.g., roughly 2600K-3000K), to "neutral white” (e.g., 3000K-4000K) to "cool white” (e.g., 4000K-8300K).
  • white light illumination devices include, but are not limited to, those that combine red, green and blue (RGB) LEDs, red, green, blue and yellow (RGBY) LEDs, white and red (WR) LEDs, and RGBW LEDs.
  • the illumination devices disclosed herein may in certain embodiments include one or more emitter modules, which may also be called lamps.
  • An emitter module has a plurality of LED elements and one or more photodetectors combined into a package.
  • an LED element may be either a single LED or a chain of serially connected LEDs supplied with the same drive current.
  • An LED element configured for its junction(s) to have sufficient forward bias for light emission may be referred to herein as an "emission LED element.”
  • An LED may also be configured as a photodetector, typically by applying zero bias or reverse bias to the LED junction and collecting photocurrent induced by incident light.
  • multiple LEDs configured as photodetectors may be connected in parallel so that their photocurrents can be combined.
  • the present invention is particularly well suited to multicolored illumination devices in which two or more different colors of LEDs are combined to produce blended white or near- white light, since the output characteristics of differently colored LEDs vary differently over drive current, temperature and time.
  • the present invention is also particularly well suited to illumination devices (i.e., tunable illumination devices) that enable the target dimming level and/or the target chromaticity setting to be changed by adjusting the drive currents supplied to one or more of the LEDs, since changes in drive current inherently affect the lumen output, color and temperature of the illumination device.
  • These tunable illumination devices should all produce the same color and color rendering index (CRI) when set to a particular dimming level and chromaticity setting (or color set point) on a standardized chromaticity diagram.
  • a chromaticity diagram maps the gamut of colors the human eye can perceive in terms of chromaticity coordinates and spectral wavelengths.
  • An example of a chromaticity diagram is shown in Fig. 1.
  • the spectral wavelengths of all saturated colors are distributed around the edge of an outlined space (called the "gamut" of human vision), which encompasses all of the hues perceived by the human eye.
  • the curved edge of the gamut is called the spectral locus and corresponds to monochromatic light, with each point representing a pure hue of a single wavelength.
  • the straight edge on the lower part of the gamut is called the line of purples.
  • Wavelength in nanometers (nm) of the corresponding monochromatic light is indicated along the curved edge of the gamut in Fig. 1.
  • the dominant wavelength, as perceived by the eye, of a point within the gamut may be found using a line including the point and a reference point for the illumination source, such as point C of Fig. 1 corresponding to the CIE-C reference.
  • the dominant wavelength under the reference illumination is read at the intersection of the line with the curved edge of the gamut.
  • a red (R) LED with a dominant wavelength of about 640 nm may have a chromaticity coordinate of (0.68, 0.28)
  • a green (G) LED with a dominant wavelength of about 525 nm may have a chromaticity coordinate of (0.17, 0.72)
  • a blue (B) LED with a dominant wavelength of 465 nm may have a chromaticity coordinate of (0.16, 0.11).
  • This dominant wavelength perceived by the eye does not necessarily correspond to the peak wavelength, or wavelength of highest intensity, emitted from an LED.
  • an illumination device is typically configured to produce a range of white or near-white color temperatures arranged along the blackbody curve (e.g., about 2500K to 5000K)
  • some illumination devices may be configured to produce any color within the color gamut, such as triangular color gamut 18 of Fig. 1, formed by the individual LEDs (e.g., RGB).
  • the chromaticity coordinates of the combined light e.g., (0.437, 0.404) for 3000K white light, define the target chromaticity or color set point at which the device is intended to operate.
  • the target chromaticity or color set point may be changed by altering the ratio of drive currents supplied to the individual LEDs.
  • the target chromaticity of the illumination device may be changed by adjusting the drive current levels (in current dimming) or duty cycle (in PWM dimming) supplied to one or more of the emission LEDs.
  • an illumination device comprising RGB LEDs may be configured to produce "warmer” white light by increasing the drive current supplied to the red LEDs and decreasing the drive currents supplied to the blue and/or green LEDs. Since adjusting the drive currents also affects the lumen output and temperature of the illumination device, the target chromaticity must be carefully calibrated and controlled to ensure that the actual chromaticity equals the target value.
  • Figs. 2-3 illustrate how the relative luminous flux of an individual LED changes over junction temperature for different colors of LEDs.
  • the luminous flux output from all LEDs generally decreases with increasing temperature.
  • the relationship between luminous flux and junction temperature is relatively linear (see Fig. 2), while for other colors (e.g., red, orange and especially yellow) the relationship is significantly non-linear (see, Fig. 3).
  • the chromaticity of an LED also changes with temperature, due to shifts in the dominant wavelength (for both phosphor converted and non-phosphor converted LEDs) and changes in the phosphor efficiency (for phosphor converted LEDs).
  • the peak emission wavelength of green LEDs tends to decrease with increasing temperature, while the peak emission wavelength of red and blue LEDs tends to increase with increasing temperature. While the change in chromaticity is relatively linear with temperature for most colors, red and yellow LEDs tend to exhibit a more significant non-linear change.
  • Figs. 4 and 5 illustrate the relationship between luminous flux and drive current for different colors of LEDs (e.g., red, red-orange, white, blue and green LEDs).
  • the luminous flux increases with larger drive currents, and decreases with smaller drive currents.
  • the change in luminous flux with drive current is non- linear for all colors of LEDs, and this non-linear relationship is substantially more pronounced for certain colors of LEDs (e.g., blue and green LEDs) than others.
  • the chromaticity of the illumination also changes when drive currents are increased to combat temperature and/or aging effects, since larger drive currents inherently result in higher LED junction temperatures (see, Figs. 2-3). While the change in chromaticity with drive current/temperature is relatively linear for all colors of LEDs, the rate of change is different for different LED colors and even from part to part.
  • U.S. Application Nos. 13/970,990 and 14/314,530 co-pending with the present application and commonly owned and/or subject to assignment with the present application, describe methods of compensation for variation in quantities including temperature and drive current, and illumination devices employing such methods.
  • Approaches described in these applications to compensating for variations in luminous flux from LEDs, such as the effects illustrated by Figs. 2-5, in some embodiments include the use of calibration tables created for the LEDs within an illumination device. Such calibration tables store results of calibration measurements previously made using the LEDs.
  • a calibration table stores values of photocurrent induced on a photodetector within the illumination device when a drive current is applied to each LED within the device separately.
  • Such a calibration table may in some embodiments store photocurrent values obtained when applying multiple different drive current levels to an LED. In some embodiments in which photocurrent values are obtained when applying different drive current levels, forward voltage measurements are obtained for each LED after each drive current is applied. Such forward voltage measurements can be used as an indication of junction temperature in the LED.
  • the calibration table may in further embodiments store photocurrent values obtained at different values of ambient temperature. Other types of data and variations of the above-described data may also be included in a calibration table, as described in more detail in co-pending applications 13/970,990 and
  • Fig. 6 is an exemplary timing diagram illustrating substantially continuous operation of one or more of the LED elements to produce illumination.
  • substantially continuously means that an operative drive current (denoted generically as II in Fig.
  • drive current II represents a combination of different drive currents applied as appropriate to respective different LED elements within the illumination device, to produce the desired illumination.
  • the intervals are utilized for obtaining forward voltage measurements from each of four emission LED elements (Vfe), one LED element at a time, by supplying a relatively small drive current to each LED and measuring the forward voltage developed there-across.
  • the intervals may also be used for other types of measurements, as shown in Figs. 8-9 and discussed in more detail below.
  • all LED elements within the illumination device remain off throughout some of the intervals to allow detection to determine whether
  • the illumination device includes at least four emission LED elements.
  • the device includes exactly four emission LED elements, and the forward voltage across each element is measured, one at a time during successive respective measurement intervals. Unless specified otherwise, a measurement performed "during" an interval as used herein is performed within the interval, but not necessarily for the entirety of the interval.
  • the four emission LED elements may be of different colors to form a multi-color lamp.
  • the multicolor lamp may be configured to produce white light, as described above.
  • one or more of the LED elements are driven with respective DC drive currents to produce illumination. In an embodiment, all of the LED elements in the lamp are driven during illumination periods 620.
  • intervals 610 are part of a periodic series having a specific offset (which may be zero) from a periodic timing reference.
  • the plot in Fig. 7 of luminous flux vs. LED drive current illustrates an exemplary technique of using calibration values to determine the drive current (Ix) needed to achieve a desired luminous flux (Lx) from an emission LED element at its present operating temperature (reflected in the present value of Vfe, Vfe_present, for the LED element measured during one of intervals 610 of Fig. 6).
  • Data points 710 denoted by filled circles, represent luminous flux values from a calibration table, obtained during calibration of the LED element using three different drive currents (10%, 30% and 100% of the maximum drive current, in the embodiment of Fig. 7) and two different ambient temperatures TO and Tl .
  • Each of data points 710 may be associated with a respective forward voltage value Vfe in the calibration table, obtained just before or just after the respective luminous flux measurement at the respective drive current and ambient temperature value. Comparison of these forward voltages in the calibration table for a given LED element to a forward voltage measured during operation can allow the present temperature T_present to be estimated.
  • interpolation between the calibration values 710 is used to predict luminous flux values 720, denoted by unfilled triangles,
  • an interpolation or curve-fitting using predicted values 720 is used to generate a relationship, plotted as curve 730, for luminous flux vs. drive current at the present operating temperature.
  • the drive current Ix needed to produce the desired luminous flux Lx can then be obtained from the generated relationship.
  • the specific interpolation techniques used may depend on the characteristics of the LED element being compensated, along with considerations such as memory and processing capability. The approach illustrated in Figs. 6 and 7 is employed in embodiments of methods for maintaining a target luminous flux from an LED element in spite of changes in the LED element's temperature.
  • FIG. 8 Another example of a compensation method is illustrated by Figs. 8 and 9.
  • the timing diagram of Fig. 8 is similar to that of Fig. 6, with operative drive current II supplied to one or more of the emission LED elements within an illumination device almost continuously, with the exception of intervals during which all of the emission LED elements, except for the emission LED under test, are momentarily turned off for short durations of time 810.
  • the first four of intervals 810 are used for measuring a photocurrent (Iph) induced on a photodetector within the illumination device, in response to illumination that is produced by each emission LED element, one LED element at a time.
  • the emission LED under test is driven with an operative drive current level.
  • photocurrent measurements allow detection of changes in the luminous flux produced by an LED element at a given drive current, as may occur in LEDs over time.
  • FIG. 9 The plot in Fig. 9 of photocurrent induced on a detector as a function of LED drive current illustrates an exemplary technique of using calibration values to determine the expected photocurrent (Iph exp) induced by a particular drive current (Ix) applied to an emission LED element at the present detector temperature (reflected in the present value of the forward voltage measured across the detector, Vfd_present, during one of intervals 810 of Fig. 8).
  • Data points 910 denoted by filled circles, represent photocurrent values from a calibration table, obtained during calibration of an LED element using three different drive currents (10%, 30% and 100% of the maximum drive current, in the embodiment of Fig. 9) and two different ambient temperatures (corresponding to VfdO and Vfdl measured at ambient temperatures TO and Tl).
  • interpolation between the calibration values is used to predict expected photocurrent values 920, denoted by unfilled triangles, corresponding to the calibration drive currents at the current detector temperature (Vfd_present).
  • an interpolation or curve-fitting using predicted values 920 is used to generate a relationship, plotted as curve 930, for expected photocurrent vs. drive current at the present detector temperature.
  • the expected photocurrent induced on the detector by an LED operated at the present value of drive current (for example, a drive current obtained using the method illustrated in Figs. 6 and 7) can then be obtained from the generated relationship. This expected value can then be compared to the corresponding presently measured photocurrent obtained during one of intervals 810 shown in Fig. 8.
  • a difference between the measured and expected values indicates a change in the light intensity generated by the LED element over time.
  • Such an "aging" effect may be compensated for by adjusting the drive current applied to the LED element, as described in co-pending application no. 14/314,530.
  • Figs. 6-9 illustrate two examples of compensation methods.
  • other compensation methods may be used instead of or in combination with these methods.
  • variations in additional quantities such as x and y chromaticity values, can be compensated for.
  • adjustment to compensate for one quantity may cause a variation in another, such that compensation methods are iterated until stable desired settings are achieved.
  • photocurrent measurements may include measurements using each of multiple photodetectors, where each photodetector is configured for sensitivity to a different spectral range.
  • a series of intervals such as intervals 610 of Fig. 6 may extend for the entire time that an illumination device is operating.
  • a sequence of compensation measurements may be repeated continuously, one measurement per interval, while the illumination device is operating.
  • compensation using intervals such as intervals 610 of Fig. 6 is performed only at certain times during operation of an illumination device. For example, compensation may be performed when a significant change in ambient temperature has been detected, or when there has been a change in settings for the illumination device.
  • Timing diagrams illustrating performance of compensation at selected times are shown in Fig. 10.
  • the upper diagram of Fig. 10 illustrates periods 1010 of continuous illumination produced by application of an operative drive current designated II to one or more LED elements.
  • drive current II represents a combination of different drive currents applied to respective different LED elements within the illumination device, to produce the desired illumination.
  • illumination periods 1010 are occasionally interrupted by compensation periods 1020, during which measurements are taken as part of a compensation method.
  • initiation of a compensation period 1020 is in response to a determination that there has been a change in some quantity such as ambient temperature or illumination settings for the device.
  • compensation periods may be repeated until a changing quantity has stabilized.
  • compensation periods 1020 may be initiated at previously specified times or for a fixed number of times, including one time.
  • the lower diagram of Fig. 10 is an expanded timing diagram of an exemplary compensation period 1020.
  • Intervals 1022 are similar to intervals 610 of Fig. 6 or intervals 810 of Fig. 8. Within intervals 1022, all emission LED elements are turned off except for a single LED element that may be turned on as part of a particular measurement. Between intervals 1022, one or more of the LED elements within the lamp are supplied with an operative drive current during illumination periods 1024. In the embodiment of Fig. 10, the drive current applied during illumination periods 1024 is "boosted" to an increased level designated generically as 12.
  • drive current level 12 represents a combination of different drive currents applied to respective different LED elements, each at a higher level than is applied to the LED element in connection with drive current level II during illumination periods 1010.
  • use of a boosted drive current during compensation periods may counteract a "flicker" effect that can result from the interruptions in illumination occurring during a compensation period such as period 1020.
  • compensation methods for an LED illumination device such as an emitter module rely upon measurements of photocurrent induced in a photodetector when a drive current is applied to an LED element.
  • subtraction of ambient-induced photocurrent is employed to mitigate the effects of interference. An embodiment for which interference-related illumination can be effectively subtracted is illustrated in Fig. 11 A.
  • Fig. 11A plots luminous flux vs. time during an interval 1102 similar to, for example, interval 1022 of Fig. 10.
  • a first portion 1104 of the interval is a measurement portion of the interval during which a particular emission LED element may be turned on (while all other emission LED elements in the illumination device are turned off).
  • Second portion 1106 in this embodiment is a portion of the interval used for ambient detection, during which all emission LED elements within the illumination device are turned off.
  • portions 1 104 and 1 106 each have a duration of approximately one-half of interval 1 102, the portions could have different relative durations in other embodiments.
  • Waveform 1 1 10 represents the luminous flux resulting from turning on an LED element during interval portion 1 104 for a measurement, then turning the LED element off during interval portion 1 106.
  • Waveform 1 1 12 denoted with a dashed line, represents the luminous flux resulting from ambient light that is constant in intensity for at least the duration of interval 1 102.
  • Fig. 1 1A plots photocurrent induced in a photodetector in response to the luminous flux plotted in the upper diagram.
  • the photodetector has equal sensitivity to the LED illumination represented by waveform 1 1 10 and the ambient illumination represented by waveform 1 1 12.
  • Waveform 1 1 14, denoted with a solid line represents the total photocurrent induced by the LED and ambient illumination, or the sum of the photocurrent induced by each type of illumination.
  • Waveform 1 16 denoted by a dashed line, represents the difference between the total photocurrent at any time and an ambient current value IA, where IA is the total current measured at a point during portion 1 106 of interval 1 102.
  • IA corresponds to the total photocurrent at time TA.
  • IA can be obtained by averaging multiple measurements taken during interval portion 1 106, or by using other signal processing techniques known to one of ordinary skill in the art in view of this disclosure.
  • total photocurrent I T is obtained by one or more measurements of photocurrent in the detector during interval portion 1 104, accompanied by averaging and/or other signal processing as understood by one of ordinary skill in the art in view of this disclosure.
  • Subtraction of ambient photocurrent IA from total photocurrent ⁇ results in corrected photocurrent Ic attributable to the LED illumination corresponding to waveform 1 1 10.
  • the detector used to measure induced ambient photocurrent IA is the same detector used to measure total photocurrent ⁇ during interval portion 1 104 when the target LED element is driven at an operative current level. In this way, the ambient photocurrent induced during measurement of the tested LED element may be most accurately accounted for by the ambient photocurrent detected during interval portion 1 106 when the tested LED element is off.
  • a separate detector may be used for ambient light detection, alternatively or in addition to a detector used for ambient detection during photocurrent measurements. A separate detector for ambient light measurement may be particularly useful, for example, in embodiments for which target settings of the illumination device are adjusted depending on ambient light conditions.
  • Fig. 9 illustrates determination of an expected photocurrent value by interpolation from stored calibration values.
  • the expected value is compared to the photocurrent measured for the corresponding LED element— for example, Iphl of Fig. 8. If the measured photocurrent includes photocurrent induced by illumination other than that from the LED element, such as total current ⁇ of Fig. 11A, comparison to the expected photocurrent determined as shown in Fig. 9 will provide an inaccurate indication of how illumination from the LED element has changed. The resulting scaling and adjustment of drive current to the LED element may therefore move the LED element away from its target settings rather than helping to maintain them. Comparison of the expected photocurrent to corrected photocurrent Ic in the embodiment of Fig. 11A, however, should provide an accurate indication of how the illumination from the LED element may have changed.
  • FIG. 1 IB A situation in which the subtraction technique illustrated in Fig. 11 A is not effective in mitigating interference is illustrated by Fig. 1 IB.
  • the upper diagram of Fig. 1 IB is a plot of luminous flux during the same interval 1102 having first and second portions 1104 and 1106, respectively, as that shown in the upper diagram of Fig. 11A.
  • the upper diagram also includes waveform 1110 as also shown in Fig. 11A, representing luminous flux from an LED element turned on during interval portion 1104.
  • the upper diagram of Fig. 1 IB includes waveform 1120 representing an additional illumination source that is on during interval portion 1104 and off during interval portion 1106.
  • waveform 1120 represents illumination from an additional LED element within a separate illumination device or emitter module than that of the LED element represented by waveform 1110.
  • Fig. 1 IB plots photocurrent induced in a photodetector in response to the luminous flux plotted in the upper diagram, assuming equal sensitivity of the photodetector to the LED illumination represented by waveforms 1110 and 1120.
  • waveform 1122 in Fig. 1 IB represents the total photocurrent induced by the illumination sources corresponding to waveforms 1 10 and 1 120.
  • the difference between the total photocurrent and current IA measured at a point during portion 1 106 of interval 1 102 is also represented by waveform 1 122, because IA is zero in Fig. 1 IB.
  • Ic is equal to IT in the embodiment of Fig. 1 IB because IA is zero. Therefore, Ic in Fig. 1 IB does not represent the photocurrent induced solely by illumination from the LED element corresponding to waveform 1 1 10. Use of the photocurrent from Fig. 1 IB in a compensation method such as that illustrated in Figs. 8 and 9 would lead to serious errors since a photocurrent not corresponding to a given LED element would be used for determining the adjustment to the drive current of that LED element.
  • Fig. 1 IB an extreme case is illustrated of an interfering light source that is turned on and off at exactly the same times as the LED element being compensated. It is noted that any interference source not having constant intensity over interval 1 102 can produce an error in measured photocurrent, even if the interference source does not turn on and off at exactly the same times as the target LED element. If the "ambient" photocurrent measured during interval portion 1 106 is not equal to the interference-generated portion of the photocurrent measured during interval portion 1 104, ambient subtraction will not be effective in extracting the photocurrent corresponding to the LED element being compensated.
  • An embodiment including a non-constant interference source as shown in Fig. 1 IB may of course include constant ambient illumination as well, in the manner shown in Fig. 1 1 A. In such an embodiment, the photocurrent associated with the constant illumination could be subtracted out, while the non-constant interfering illumination would lead to compensation errors.
  • Non-constant illumination refers to illumination having a substantial variation with time during a measurement interval, or during a portion of a measurement interval in which detection of background or ambient illumination is being performed.
  • a substantial variation is a variation that would result in a significant error for a photocurrent measurement conducted during the same interval.
  • the size of the variation that would result in a significant error depends on the relative magnitudes of photocurrents induced by a measured LED element and by the external illumination in the photodetector used for the photocurrent measurement.
  • Fig. 12 A further illustration of how the kind of interference shown in Fig. 1 IB can arise is given by Fig. 12.
  • Two timing diagrams are shown in Fig. 12.
  • the upper diagram, designated Lamp A is associated with a first emitter module including multiple LED elements and a photodetector.
  • the lower diagram, designated Lamp B corresponds to a second emitter module.
  • the two lamps may in some embodiments be part of a single larger illumination device. In other embodiments, the two lamps may be in separate illumination devices that are installed in proximity to one another, or even facing one another.
  • Each timing diagram corresponds to a portion of a compensation period such as period 1020 of Fig. 10, in which periods of
  • illumination 1202 are interrupted by intervals including intervals 1210, 1220, 1230 and 1240, during which the emission LED elements within the lamp are turned off and a measurement associated with a particular LED element and/or detector may be taken.
  • drive currents applied to LED elements during the illumination periods may be "boosted" as shown in Fig. 10, to a higher level as compared to the level during longer illumination periods not interrupted by measurements, such as periods 1010 of Fig. 10.
  • interval 1210 of Fig. 12 a forward voltage measurement (denoted as VAA) is taken of an emission LED element 1 within Lamp A. No measurements are taken for Lamp B during interval 1210; instead, drive currents are applied to one or more of the emission LED elements of Lamp B to produce the desired illumination. In other words, interval 1210 is an interval for Lamp A but not for Lamp B. Whether illumination from Lamp B interferes with the forward voltage measurement taken for Lamp A depends on the relative magnitudes of the bias- induced current in the LED element being measured and the photocurrent induced in the LED element by the external illumination.
  • the magnitude of the photocurrent induced may depend on multiple factors, such as the relative locations of Lamp B and Lamp A, the relative wavelengths of the driven LED element in Lamp B and Lamp A, and the carrier recombination lifetimes under measurement conditions for the measured LED element in Lamp A.
  • the induced photocurrent from external radiation is on the order of a microampere or less, while the forward bias induced current in the measured element is on the order of a milliampere.
  • illumination by Lamp B in interval 1210 of Fig. 12 would not have a significant effect on the forward voltage measurement taken by Lamp A.
  • the forward voltage measurement in such an embodiment may be considered to not be sensitive to illumination from the other illumination device.
  • one of the lamps is performing a photocurrent measurement on an LED element, while the other lamp is performing a forward voltage measurement.
  • a forward voltage measurement Vf2A of emission LED element 2 of Lamp A is performed, while a photocurrent measurement I p 2B measures the photocurrent induced in a detector of Lamp B by operation of emission LED element 2 of Lamp B.
  • forward voltage measurements of emission LED elements are taken using non-operative levels of drive current, meaning drive current levels insufficient to produce significant illumination from the LED. In such an embodiment, the forward voltage measurement taken using one lamp would not be expected to interfere with the photocurrent measurement taken using the other lamp.
  • detection is performed during one or more intervals before a photocurrent measurement is performed during one of the intervals.
  • the detection during one or more intervals is performed before any measurement associated with compensation of an illumination device is performed.
  • Photocurrent measurements, or in some embodiments any measurements, are initiated after detection has been performed for enough intervals to indicate that interference from compensation measurements of another lamp is unlikely.
  • a photocurrent measurement or in some embodiments any measurements, are initiated after detection has been performed for enough intervals to indicate that interference from compensation measurements of another lamp is unlikely.
  • photodetector is used to determine whether outside illumination is present that is not constant throughout the measurement interval.
  • the number of intervals used for detection depends on the particular sequences of measurements used by the illumination device performing the method and by any potentially interfering devices. As noted above in the discussion of Fig. 12, some types of measurement used for compensation of LED elements in an illumination device are more likely to interfere with other illumination devices than other types of measurement.
  • the specific measurements most likely to cause interference include measurements of photocurrent induced in a detector by an illuminated LED element. In such an embodiment, those are the measurements most likely to produce a non-constant illumination that could interfere with a photocurrent measurement by a different illumination device.
  • the measurements that are most likely to result in interference are also the measurements most likely to be detected by a different illumination device employing detection intervals before starting its own photocurrent measurements. The number of intervals used for detection may depend on how many total measurements are expected to be performed in a compensation measurement sequence, as well as how many of those measurements are expected to be of the kind most likely to cause interference.
  • an emitter module including 4 LED elements and at least one photodetector.
  • the photodetector(s) may be dedicated photodetectors or may in some embodiments be emission LEDs configured at certain times as photodetectors.
  • such an emitter module may use a sequence of 12 measurements for compensation.
  • 4 of the compensation measurements could be forward voltage measurements for each of the 4 LED elements.
  • Another 4 measurements could be photocurrent measurements for each of the 4 LED elements using one dedicated photodetector.
  • Another 2 measurements could be photocurrent measurements for two of the LED elements using an additional photodetector.
  • the remaining 2 measurements could be forward voltages across each of two detectors.
  • 6 of the 12 compensation measurements are photocurrent measurements.
  • any interfering illumination devices will also be configured to use a sequence of 12 compensation
  • measurements 6 of which are photocurrent measurements. If the particular sequence of measurements that an interfering device may be configured to use is not known, one approach would be to detect for 12 measurement intervals before starting compensation measurements. If no non-constant illumination is detected during any of the 12 intervals, it is likely that no nearby illumination device is performing compensation measurements. In another embodiment, if it is expected that 6 of the compensation measurements performed by an interfering device are photocurrent measurements, detection could be performed for 7 intervals before starting compensation measurements if no non-constant illumination is detected. If another device were performing compensation measurements including six photocurrent measurements, one of the 6 photocurrent measurements would be expected to occur within a sequence of 7 intervals. In still another embodiment, if the 6 photocurrent measurements were expected to be uniformly spaced within the 12-measurement sequence (in this case, every other measurement of the 12
  • the various photocurrent measurements included in the compensation measurement sequence are not equally detectable. Some of the photocurrent measurements may be easier to detect, and more likely to cause interference, than others. This may particularly be the case in embodiments with emitter modules containing emission LED elements emitting different colors of light. Certain combinations of LED element and detector may result in significantly higher photocurrent signals. Measurements using these emitter/detector combinations may be referred to as "beacon" measurements.
  • the magnitude of the photocurrent signal for a particular measurement depends on factors including the luminous flux emitted by the LED element, the sensitivity of the detector, and how well the emitter and detector are matched in terms of spectral response. As an example, one measurement for a multi-color emission module that may result in a relatively high photocurrent signal is measurement of a green emission LED element using a detector configured to detect red light (in an embodiment, the detector is a red LED configured as a detector).
  • the number of detection intervals used before starting compensation measurements may be chosen such that one of these higher- photocurrent signals would be expected to occur if a nearby device is performing compensation measurements. If the sequence of the measurements is not known, for example, 11 intervals without detection of a non-constant illumination would be needed to be certain that one of the 2 "beacon" measurements should have occurred if interfering measurements are in progress.
  • Fig. 13 A detection intervals 1310 are used to determine whether measurements taken by another lamp can be detected. If no other measurements are detected, compensation measurements are initiated during subsequent intervals denoted in Fig. 13A as measurement intervals 1320.
  • the necessary number of detection intervals 1310 in which no interfering measurement is detected depends on factors such as the number, nature and sequencing of compensation measurements, as discussed further above. The specific
  • Non-sensitive measurements as used herein are measurements not affected significantly by external illumination. In an embodiment, non-sensitive
  • measurements include forward voltage measurements across an LED element or a photodetector. As discussed further above in connection with Fig. 12, such forward voltage measurements are expected to be non-sensitive if the forward-bias induced current in the measured LED element is large compared to the photocurrent induced by the external illumination.
  • a timing sequence such as that of Fig. 13B may allow non-sensitive measurements to be taken earlier, while it is still being determined whether measurements sensitive to interfering illumination (denoted as sensitive measurements 1324) can be taken without interference.
  • detection for interfering measurements may be performed during the same interval as one of non-sensitive measurements 1322, as long as the detector used for detecting interference is not involved in the non-sensitive measurement.
  • the non-sensitive measurement is a forward voltage measurement
  • the forward voltage measurement would need to be performed at a non-illuminating level of drive current to avoid error in performing detection at the same time.
  • the expected measurement sequence of any interfering devices would need to include enough consecutive higher-intensity measurements that a measurement sequence performed by a nearby device would be detected during one of the intervals when detection is performed.
  • higher-intensity measurements performed by an interfering device would need to be grouped so that at least two of the high-intensity measurements are performed in consecutive intervals. In this way, if the interfering device is performing measurements and one high-intensity
  • Figs. 13A and 13B illustrate examples of an approach in which some number of detection intervals is used to obtain an indication that no nearby device is performing interfering measurements. When no interfering measurement is observed after a sufficient number of detection intervals, compensation measurements are initiated during subsequent intervals. If, on the other hand, a non-constant illumination is detected during a detection interval, this is an indication that a nearby device is performing interfering
  • Detection of a constant illumination during the interval is not associated with an interfering measurement in such an embodiment, because the effects of a constant external illumination on a photocurrent measurement can be removed by ambient subtraction such as that illustrated in Fig. 11 A. In some embodiments, detection can be performed by taking
  • a non-zero result of the subtraction in such an embodiment indicates a non-constant illumination during the interval.
  • detection of a non-constant illumination during a detection interval causes an illumination device to discontinue the detection sequence and return to driving the emission LED elements in the device to provide continuous illumination.
  • the illumination device may be returned to a continuous illumination state uninterrupted by detection intervals or measurement intervals, similar to illumination periods 1010 of Fig. 10 above.
  • a sequence of alternating illumination periods and intervals with the emission LED elements turned to non-operative levels may be continued after the detection sequence is discontinued, but without measurement taking place during the intervals.
  • any intervals present after the detection sequence is suspended would not be used for detection or measurement until such time that a detection sequence is restarted.
  • the measurement control circuit of the illumination device waits, in one embodiment, for some delay time before restarting the detection sequence.
  • the delay time is a randomized delay time. After waiting for the delay time, the measurement control circuit may in one embodiment start again at the beginning of the detection sequence that was aborted upon detection of the non-continuous illumination.
  • the detection sequence may be picked up at a point after the beginning of the sequence.
  • the detection sequence is started again at the point in the sequence when the non-continuous illumination was previously detected.
  • Such an embodiment may be suitable, for example, in a sequence such as that of Fig. 13B in which some non-sensitive measurements are performed successfully in an earlier detection sequence before it is aborted.
  • the pair of timing diagrams in Fig. 14 is for two emitter modules, designated Lamp A and Lamp B, similar to those described in the discussion of Fig. 12 above.
  • Each lamp is operating in a compensation mode such as that within a compensation period 1020 of Fig. 10, in which periods of illumination 1402 are interrupted by intervals including intervals 1410, 1420, 1430, 1440 and 1450.
  • the emission LED elements within the lamp are turned off (or to a non-illuminating level) and detection may be performed or a measurement associated with a particular LED element and/or detector may be taken.
  • intervals 1410 and 1420 are detection intervals for Lamp A. These intervals are measurement intervals for Lamp B, however.
  • Lamp B is carrying out a sequence of 8 measurements in which a forward voltage for each of four emission LED elements is followed by a measurement of photocurrent induced in a detector when a drive current is applied to that LED element.
  • the lower timing diagram in Fig. 14 therefore shows the entire sequence of measurements carried out by Lamp B.
  • this measurement sequence is repeated continuously using subsequent intervals.
  • the lamp returns to a continuous illumination mode such as an illumination period 1010 of Fig. 10, and the measurement sequence is repeated if a change in operating conditions is detected or at certain preset times.
  • Lamp B carries out a forward voltage measurement VA B of a first emission LED element. Even in an embodiment for which Lamps A and B are in close proximity and/or facing one another, Lamp A does not detect any significant non-constant illumination from the measurement by Lamp B as long as the drive current for the measurement VfiB is at a level too low to result in illumination. During interval 1420, however, Lamp A does, in this embodiment, detect a non-constant illumination associated with the measurement by Lamp B of photocurrent I p iB induced in a detector when the first LED element is illuminated. In the embodiment of Fig.
  • the sequence of measurements employed by potentially interfering lamps, including Lamp B, is known to the control circuit of Lamp A, and Lamp A employs the same sequence for its own compensation measurements.
  • the control circuit of Lamp A determines that an interfering lamp made a photocurrent measurement during that interval. Because the measurement sequence is known to alternate photocurrent measurements with non-illuminating forward voltage measurements, the control circuit of Lamp A can predict that the interfering lamp will make a forward voltage measurement during the next interval, interval 1430. Because the measurement sequence begins with a forward voltage measurement, the control circuit of Lamp A waits for one additional interval and begins the measurement sequence for Lamp A at interval 1440. In this way, the photocurrent measurements by Lamp B line up in the same intervals as the non-sensitive, and non-interfering, forward voltage measurements by Lamp A.
  • both Lamps A and B can keep repeating the
  • the control circuit of Lamp A can determine an interval for starting a non-interfering measurement sequence after detection of just one interfering measurement. In embodiments using different measurement sequences, the control circuit may need to detect multiple interfering
  • Fig. 14 depends on access by the control circuit of an illumination device to the measurement sequence used by potential interfering devices.
  • the control circuit may have such information is an installation in which the lamps in close proximity to one another are all made by the same manufacturer and use the same control sequence.
  • a control circuit has information on measurement sequences of potential interfering lamps because the lamps in close proximity to one another are manufactured to a common standard that specifies the measurement sequence.
  • information regarding the measurement sequences of various other lamps may in some embodiments be available to the control circuit of an illumination device.
  • An illumination device may in certain embodiments include a data structure storing configuration information including compensation measurement sequences for various potentially interfering lamp models.
  • the control circuit may need to detect multiple interfering measurements before determining which measurement sequence is being used by another device and whether overlapping measurement sequences are possible without interference.
  • measurement errors may occur despite use of the above-described detection techniques. For example, a prediction that a lamp may safely begin making measurements based on the expected measurement sequence of a single interfering lamp may be in error if multiple nearby lamps are making measurements. As another example, measurement errors can occur if two or more lamps are performing detection during the same intervals and, each detecting no other measurements, both begin measurements at the same time. [0127] In an embodiment, measurement errors are detected by checking to see whether a measured value is within an expected range. In a further embodiment, the expected range is based on the most recently stored value of the measured quantity. In such an embodiment, the expected range accounts for the magnitude of expected variations in the measured quantity caused by factors such as LED aging or temperature change of an LED element.
  • a measured value is outside of the expected range if it varies by more than about 5 percent from the most recently stored value of the measured quantity. In another embodiment, a measured value is outside of the expected range if it varies by more than about 3 percent from the most recently stored value. In yet another embodiment, a measured value is outside of the expected range if it varies by more than about 2 percent from the most recently stored value. Other thresholds for considering a measurement out-of-range may be used, depending on factors such as the volatility of the particular quantity being measured and the degree of accuracy required for compensation and control of the illumination device. If the measured value is outside of the expected range, the measured value is discarded rather than stored.
  • the measurement sequence continues after an out-of range measurement is detected, with in-range measurements stored while out-of-range measurements are discarded.
  • an out-of-range measurement causes the measurement sequence to be suspended.
  • the control circuit of the illumination device may wait for a delay time and then attempt the measurement sequence again. The new attempt may start at the beginning of the sequence, or alternatively may start with the measurement that was out of range.
  • the control circuit may wait for a delay time and then begin a detection sequence before attempting measurements again.
  • Checking for whether a measurement is in range is in some embodiments combined with methods described above for detection during some number of intervals before performing compensation measurements.
  • measurements are performed without any detection intervals beforehand, with the measured values checked for being out of an expected range.
  • measurements are initially performed without detection beforehand, but if an out-of-range value is obtained, a detection method as described above is employed before resuming measurements.
  • checking for whether a measurement is in range is performed only for interference-sensitive measurements such as photocurrent measurements. In other embodiments, all measured values are checked for being within an expected range.
  • timing reference signal 1520 is generated from an AC reference signal 1510.
  • timing reference signal 1520 is generated from AC signal 1510 using a phase locked loop (PLL) circuit.
  • PLL phase locked loop
  • reference signal 1520 has a frequency of six times that of AC signal 1510.
  • AC signal 1510 is the AC mains signal, typically having a frequency of 50Hz or 60Hz.
  • reference signal 1520 has a frequency of 360 Hz in the embodiment of Fig. 15.
  • Waveform 1530 illustrates the drive current variation with time for an illumination device, such as an emitter module, using a first set of intervals for compensation measurements.
  • "on" current I on represents a combination of one or more different drive currents applied as appropriate to respective different LED elements within the illumination device, to produce the desired illumination.
  • the drive currents are reduced to a level I 0ff at which none of the LED elements are operating, or illuminated, except for a single LED element that may be subject to measurement during the interval.
  • Each of the intervals has a duration 1532 and is separated from a rising edge of timing reference 1520 by a first offset 1536.
  • Waveform 1540 illustrates the drive current variation with time for an illumination device using a second set of intervals for compensation measurements.
  • Waveform 1540 is similar to waveform 1530, except that the periodic intervals in waveform 1540 are separated from a rising edge of timing reference 1520 by a second offset 1546.
  • one emitter module is configured to perform compensation measurements using a first set of measurement intervals such as those of waveform 1530, and another emitter module is configured to perform its compensation measurements using a second set of measurement intervals such as those of waveform 1540, measurements by the two emitter modules will not interfere with one another because the two sets of measurement intervals are displaced in time.
  • lamps or emitter modules that are to be placed in close proximity are assigned to different sets of measurement intervals.
  • Such an embodiment may be particularly suitable for illumination fixtures containing multiple lamps or emitter modules.
  • an emitter module may initially use one set of measurement intervals and later switch to another set of measurement intervals if interference from nearby devices is encountered.
  • This type of embodiment may be suitable in the case of an individual emitter module, since the configuration of lamps that it may be operated in proximity to is typically not known.
  • timing reference signal 1520 has a period of approximately 2.8 milliseconds.
  • the measurement intervals of waveforms 1530 and 1540 have a duration of approximately 550 microseconds while the first offset is approximately 800 microseconds and the second offset approximately 2 milliseconds. It should be noted that the measurement intervals may have any duration sufficient to perform any compensation measurement needed. In an embodiment, the measurement interval should be long enough to allow a period of measuring the desired quantity and a period for ambient measurement.
  • measurement intervals be as short as possible in order to reduce effects such as "flicker” caused by turning the LED elements on and off.
  • the measurement interval duration is approximately 100 microseconds. The number of different sets of measurement intervals that may be used depends on the period of the timing reference signal and the duration of the measurement interval.
  • the number of intervals in a measurement sequence is set to be an integral multiple of N.
  • N the number of intervals in the measurement sequence in this embodiment would be set to a multiple of 6, even if some intervals were left empty in order to do so. In this way, repetition of the measurement sequence would cause repetitions of any individual measurement to occur at the same point in the phase of the AC signal.
  • the number of intervals in the measurement sequence is instead set to a number that is not an integral multiple of N. In such an embodiment repetition of the measurement sequence would cause repetitions of any individual measurement to occur at different points in the phase of the AC signal.
  • values obtained from repetitions of an individual measurement are averaged. In such an embodiment, use of a number of
  • measurements that is not an integral multiple of N may provide a more accurate measurement when results from repetitions of a measurement taken at different AC phase points are averaged.
  • Figs. 16A through 16C Flowcharts of exemplary methods of performing interference-resistant compensation measurements using the approaches described above are shown in Figs. 16A through 16C.
  • the flowchart of Fig. 16A is for a method in which no detection is performed before beginning a sequence of measurements.
  • photocurrent measurements include subtraction of ambient photocurrent, and the method includes determining whether photocurrent values are within an expected range.
  • the starting point for the method is operation of one or more emission LED elements within an illumination device or emitter module at respective drive currents to produce the desired illumination (step 1602). This illumination is continued until the control circuit of the illumination device determines that it is time to take compensation measurements (decision 1604).
  • compensation measurements are performed at specific times.
  • the measurements may be performed when a change is detected in operating conditions, such as temperature of the illumination device or a change in drive current supplied to one or more of the emission LEDs to alter the lumen output or color point setting of the illumination device.
  • a change is detected in operating conditions, such as temperature of the illumination device or a change in drive current supplied to one or more of the emission LEDs to alter the lumen output or color point setting of the illumination device.
  • compensation measurement intervals may be created throughout the time the illumination fixture is operating, and compensation measurement sequences may be continually repeated using those intervals.
  • a measurement counter is initialized to keep track of which measurements in a measurement sequence have been performed (step 1606). All of the emission LED elements are then turned off (to non-operative or non-illuminating levels) at the start of the next measurement interval (step 1608).
  • the measurement interval is one of a set of intervals such as those discussed in connection with Figs. 6, 8 and 10-15 above. If the measurement to be performed is not a photocurrent measurement, the measurement is performed during the interval and the result of the measurement is stored (decision 1610, step 1612, step 1614).
  • a non-photocurrent measurement may include, for example, a forward voltage measurement across an emission LED or a photodetector. Methods of performing forward voltage measurements are described further in the co-pending applications referenced herein. After the result is stored, the measurement counter is incremented and the emission LED elements are turned back on to produce illumination (steps 1616, 1618).
  • the emission LED element to be tested is turned on using the desired drive current during a first part of the measurement interval (decision 1610 and step 1622). In one embodiment, the emission LED element is turned on for half of the measurement interval. In other embodiments, the emission LED element is turned on for a different fraction of the measurement interval.
  • the photocurrent on a detector within the illumination device or emitter module is measured during the part of the measurement interval when the tested LED element is turned on (step 1624).
  • the detector used in the measurement may be referred to herein as a measurement photodetector and the photocurrent detected by the measurement may be referred to as a measurement photocurrent.
  • the tested LED element is turned off (while the other emission LED elements remain turned off) (step 1626).
  • the ambient or background photocurrent induced in the detector is measured during this second part of the measurement interval (step 1628).
  • the photocurrent values may be obtained using averaging and/or other signal processing techniques known to those of ordinary skill in the art in view of this disclosure.
  • the first part of the measurement interval during which the LED element is turned on is at the beginning of the interval, as illustrated by portion 1104 of Fig. 11. In other embodiments, the first part is at the end of the interval, and the ambient measurement in the second part of the interval is done before the measurement of photocurrent from the driven LED element.
  • the ambient photocurrent is subtracted from the photocurrent induced by the driven emission LED element to obtain a corrected photocurrent (step 1630). In an embodiment, this subtraction is done in hardware.
  • the corrected photocurrent is then checked to see whether it is within an expected range (decision 1632). In an embodiment, the expected range is based on a target value of the photocurrent, or on the most recent reliable measured value. The expected range is in some embodiments set to be larger than the expected variation of the photocurrent caused by temperature variation or LED aging. If the corrected photocurrent is within the expected range, it is stored (step 1614) and the measurement counter is incremented (step 1616).
  • Fig. 16A if the corrected photocurrent is out of the expected range, storage of the corrected value is skipped (N branch of decision 1632). Incrementing of the measurement counter and continuing on with the next measurement in the sequence (steps 1616 and 1618, decision 1620) are performed in the same way whether the photocurrent measurement is stored or discarded. In this embodiment, a measurement for which the result is not stored can be attempted again when its turn comes up in the next measurement sequence. In an alternate embodiment to that of Fig. 16A, the measurement sequence is suspended when an out-of-range measurement is discovered. In such an embodiment, the measurement sequence may be re- attempted after a delay time or after changing to a different set of measurement intervals. Some of these options are illustrated in the method of Fig. 16B discussed below.
  • one or more of the emission LED elements are again operated to produce the desired illumination (step 1618).
  • the drive currents applied to the respective LED elements to obtain desired illumination may be adjusted, as described further in the co-pending applications referenced herein.
  • the sequence of measurements is continued, with any photocurrent measurements either stored or discarded, until the end of the sequence (decision 1620).
  • a new measurement sequence may be started as determined by the control circuit (decision 1604).
  • measurement sequences may be repeated continually in some embodiments, or performed only at certain times or under certain conditions. In one embodiment, a measurement sequence is repeated if an out-of-range measurement is detected in the previous sequence.
  • FIG. 16B An exemplary flowchart for a method of detecting during a series of intervals prior to starting compensation measurements is shown in Fig. 16B.
  • the method begins with operation of one or more emission LED elements to produce the desired illumination (step 1602). This illumination is continued until the control circuit of the illumination device determines that it is time to take compensation measurements (decision 1604). After it is determined that compensation measurements are to be taken, the control circuit initializes a counter for "collisions," or determinations that another device is making a measurement during an interval. Counters are also initialized for free intervals, or intervals in which no measurement by another device is detected, and for contiguous free intervals since the last collision (step 1634).
  • All of the emission LED elements are turned “off, or to non-operative levels, at the start of the next interval (step 1636), which in the embodiment of Fig. 16B is used as a detection interval similar to intervals 1310 in Fig. 13.
  • the photocurrent induced in a detector within the illumination device is monitored during the detection interval (step 1638).
  • the detector used during a detection interval may be referred to herein as a “detection interval photodetector,” and the photocurrent induced during the detection interval as “detection photocurrent.”
  • the detection interval photodetector and measurement photodetector used during compensation measurements are the same
  • the detection interval photodetector and measurement photodetectors are different detectors. In some embodiments, different
  • any of the detectors referenced herein may be either a dedicated photodetector or an LED element temporarily configured as a photodetector.
  • a "free" interval is recorded by incrementing the free interval counter and contiguous free interval counter (step 1658).
  • the emission LED elements are turned back on to resume illumination at the end of the interval (step 1656).
  • a number of contiguous free intervals has been designated as an indicator that no other device is likely to be taking measurements using the same set of intervals. Considerations for determining a suitable number of free contiguous intervals are described above in the discussion of Figs. 12 and 13. When the designated number of contiguous free intervals has been reached, compensation measurements are started in the next interval (decision 1660 and step 1662). Measurements may then proceed in any suitable manner, including a manner similar to that illustrated in Fig. 16A.
  • the collision counter is incremented and the contiguous free interval counter is reset (decision 1640 and steps 1644 and 1646).
  • the emission LED elements are turned back on as usual to resume illumination at the end of the interval (step 1642).
  • the control circuit waits for a delay time before attempting detection again (decision 1648, steps 1650 and 1636).
  • the delay time is a randomized delay time.
  • the delay time is determined using the collision counter, such that after each successive collision the delay time is progressively longer. For example, in one embodiment the delay time is randomized within a specific range, and that range is set to progressively higher values after each successive collision. In a further embodiment, the delay time increases after each successive collision at an exponential rate.
  • detection of non-constant illumination refers to detection of illumination having an intensity that varies substantially with time during the detection interval, or during a portion of the detection interval in which detection is performed.
  • illumination intensity varies substantially with time if the variation would be large enough to induce a significant error in a photocurrent measurement conducted during the same interval.
  • a substantial variation in intensity is defined in terms of the intensity of illumination produced by a photocurrent measurement within the illumination device performing a method such as that of Fig. 16B.
  • a substantial variation in intensity is defined in terms of the intensity of illumination produced by the LED element within the illumination device producing the lowest illumination intensity during photocurrent measurements performed as part of a compensation measurement sequence.
  • a substantial variation in intensity with time may be defined in one embodiment as a variation large enough that the change in intensity during the interval is greater than about 5% of the intensity produced by the LED element within the illumination device having the lowest illumination intensity during photocurrent measurements.
  • a substantial variation is a variation large enough that the change in intensity during the interval is greater than about 3% of the intensity produced by the LED element within the illumination device having the lowest illumination intensity during photocurrent measurements.
  • a substantial variation is a variation large enough that the change in intensity during the interval is greater than about 2% of the intensity produced by the LED element within the illumination device having the lowest illumination intensity during photocurrent
  • thresholds for detecting interference may be used, depending on factors such as the degree of accuracy required for compensation and control of the illumination device.
  • a maximum number of collisions may be reached (decision 1648).
  • the control circuit changes to a different series of measurement intervals, separated from a timing reference by a different offset time (step 1652).
  • Such sets of intervals are described above in connection with waveforms 1530 and 1540 in Fig. 15.
  • the detection sequence is restarted by resetting all counters after a change to a new set of intervals (step 1634).
  • a change to a new series of intervals such as that of Fig. 16B may be particularly suitable in the case of an illumination device including a single lamp or emission module.
  • each lamp may be assigned to a specific interval series in order to avoid interference between them, such that changing of the interval series could in some cases increase the likelihood of interference.
  • the detection interval only a portion of the detection interval is monitored, based on knowledge of when during the interval a change in illumination intensity caused by an interfering measurement is expected to take place.
  • the expected intensity variation may be associated with a transition between driving an LED element for a photocurrent measurement and having the LED element turned off for an ambient photocurrent measurement, as shown in Fig. 11 A.
  • the monitoring can be done over a range including that transition time.
  • FIG. 16C An alternative method of detecting prior to starting compensation measurements is illustrated by the flowchart of Fig. 16C.
  • the method of Fig. 16C is similar in some respects to that of Fig. 16B, but in Fig. 16C there does not always have to be a certain number of contiguous free intervals detected before compensation measurements can start.
  • the method of Fig. 16C allows a measurement sequence to be started if it can be overlapped with an ongoing measurement sequence of another device in such a way that the measurements do not interfere with (i.e. cause measurement errors for) one another.
  • Fig. 16C the context of the method is the same as for Figs. 16A and 16B in that one or more LED elements are operated to produce the desired illumination until the control circuit of the illumination device determines that it is time to take compensation measurements (see steps 1602 and 1604 of Figs. 16A and 16B).
  • Monitoring for non-constant illumination is performed in the same manner as for Fig. 16B, and in the event that a designated number of contiguous free intervals is reached, a measurement sequence is started in the same way as in the method of Fig. 16B (steps 1638-1662, going down right side of flowchart).
  • the method of Fig. 16C differs from that of Fig. 16B in the event that a collision is detected, however.
  • the control circuit in the embodiment of Fig. 16C determines whether the measurement sequence causing the detected collision is known (decision 1664). If the interfering measurement sequence is known, the control circuit determines whether it can initiate compensation measurements that overlap with those of the other device in a manner that avoids interference (step 1670).
  • configuration information 1700 includes measurement sequences for three different illumination devices, designated Brand A, Brand B, and Brand C. In an embodiment, the three illumination devices are made by different manufacturers.
  • Configuration information 1702 is for the Brand A device, while information 1704 and 1706 is for the Brand B and Brand C devices, respectively.
  • Controlled device information 1710 indicates that the controlled device (the one that configuration information 1700 is stored in) is a Brand A device in this embodiment.
  • Sequence information 1708 includes the sequence of compensation measurements performed for each device.
  • sequence information 1708 includes the specific measurement performed in each interval of the sequence, as well as whether the measurement is Sensitive or Non-sensitive (to external illumination) and whether the
  • photocurrent measurements are Interfering or Non-interfering.
  • photocurrent measurements are all considered to be both sensitive and interfering, since photocurrent measurements both detect illumination (and are therefore sensitive to external illumination) and create illumination from the tested LED element (and therefore can interfere with another photocurrent
  • forward voltage measurements whether across an emission LED element (e.g. Vn) or a detector (e.g. ⁇ 1 ⁇ 2 ⁇ ), are considered to be non-sensitive and non- interfering. That a forward voltage measurement is non-interfering is believed to be a suitable assumption when the forward voltage measurements are performed with low drive current levels so that the measured devices do not produce illumination. In other embodiments with higher drive current levels, a forward voltage measurement may be an interfering measurement (though probably still not a sensitive measurement). As discussed further above with reference to Figs. 12 and 13, a forward voltage measurement can be considered non-sensitive if the forward bias induced current in the measured LED element is large with respect to any photocurrent induced by external illumination. In the embodiment of Fig.
  • the measurement sequence for each device includes two empty intervals to bring the length of the sequence to 12 intervals. Such empty intervals are non-sensitive and non-interfering.
  • the 12 interval length of the measurement sequences in Fig. 17 is merely exemplary. Any number of intervals may be used to form a measurement sequence, and a set of measurement sequences included in configuration information such as configuration information 1700 may include sequences having different lengths (i.e., including different numbers of measurement intervals). [0151]
  • actual measurement sequences for all three devices are known. In other embodiments, specific measurement sequences for devices made by other manufacturers may not be known.
  • decision block 1664 determines whether the order of interfering and non-interfering measurements within the interfering measurement sequence is known, rather than whether the actual measurements within the sequence are known.
  • the remaining information in configuration data 1700 characterizes the measurement sequence for each device in ways that may be helpful in determining whether an overlapping measurement sequence can be formed.
  • an overlapping but not interfering measurement sequence can be conducted as long as any sensitive measurements in one sequence of measurements performed by one device are not performed in the same interval as an interfering measurement in another sequence of measurements performed by a nearby device. Because in the embodiment of Fig. 17 sensitive measurements and interfering measurements are the same, much of the configuration information is described in terms of sensitive measurements, but is also applicable to interfering measurements.
  • the rule for conducting overlapping but not interfering measurements can be restated as making sure that a sensitive measurement in one sequence is not performed in the same interval as a sensitive measurement in the other sequence.
  • number of sensitive measurements 1712 indicates the number of sensitive measurements within each sequence.
  • the number of non-sensitive measurements 1714 is accordingly eight for each of the devices.
  • a high fraction of sensitive (or interfering) measurements in a measurement sequence can make it less likely that an overlapping measurement sequence can be performed. For example, if in an alternate embodiment the measurement sequence for the Brand A device had 7 out of 12 interfering measurements rather than 4 out of 12, it would be very difficult to overlap measurement sequences for two Brand A devices in close proximity to one another without having a sensitive measurement by one device performed in the same interval as a sensitive (and interfering) measurement by the other device.
  • Same-sequence non-interfering offset 1716 refers to a number of intervals by which a device performing a measurement sequence needs to offset (i.e., delay) its sequence with respect to another device performing the same sequence. For example, if a Brand A device detected a photocurrent measurement performed by an interfering device and it was known that the interfering device was also a Brand A device, it would be known from Brand A configuration information 1702 that the next measurement, if any, by the interfering device would be a non- interfering (non-photocurrent) measurement. The detecting device could not start its
  • interval range 1718 Another quantity included in configuration information 1700 is interval range 1718 including all sensitive measurements.
  • the Brand A sequence has a range 1718 of 7 intervals, from interval 2 to interval 8, in which all of the sensitive measurements are performed.
  • the Brand B sequence has a range 1718 of 6 intervals, from interval 3 to interval 8.
  • For the brand C device all of the sensitive measurements are performed within a range 1718 of 4 intervals.
  • interval range 1720 Also included in configuration information 1700 is interval range 1720 of the most contiguous non-sensitive measurements within a measurement sequence. Interval range 1720 is 5 for the sequence of Brand A, from interval 9 to interval 1 (assuming that the measurement sequence is continually repeated). For the measurement sequence of Brand B, interval range 1720 is 6 intervals, from interval 9 to interval 2.
  • interval range 1720 is eight intervals, from interval 5 to interval 12.
  • Interval ranges 1718 and 1720 may be useful in determining whether different measurement sequences, such as those used by different device manufacturers, may be overlapped without interference.
  • the measurement sequences of the three devices of configuration information 1700 are too different to allow non- interfering overlap of two different device sequences using a simple one- or two-interval shift. In some cases, however, a larger shift can align a contiguous range of non-sensitive
  • the measurement sequence of Brand A in Fig. 17 can overlap with the sequence of Brand C if the Brand A sequence is shifted so that interval 2 of the Brand A sequence is aligned with interval 5 or 6 of the Brand C sequence. In this way, all of the sensitive measurements in the Brand A sequence are performed in intervals with non-sensitive measurements by the Brand C device.
  • the measurement sequence of a Brand A device cannot overlap with that of a Brand B device, because there is no contiguous range of non-sensitive measurements in the Brand B sequence large enough to accommodate the range of intervals in the Brand A sequence including sensitive measurements.
  • configuration information such as that of Fig. 17 may be used by the control circuit of an illumination device in determining (for decision 1664) whether a measurement sequence associated with a detected measurement is known.
  • a single detection of an interfering measurement by another device would not in itself be enough to determine whether which of the known measurement sequences is being used by the interfering device. If the interfering measurement sequence is not known, the control circuit initiates a detection process during the next interval to get further information (N branch of decision 1664 and step 1636).
  • N branch of decision 1664 and step 1636 In the embodiment of Fig.
  • control circuit is able to determine a measurement sequence used by the interfering device by monitoring the collision, free interval, and contiguous free interval counters during successive intervals. For example, a sequence of a detected
  • photocurrent measurement i.e., a collision
  • non-sensitive measurement which increments the free interval and contiguous free interval counters
  • another sensitive measurement which increments the collision counter and clears the contiguous free interval counter
  • the control circuit determines whether an overlapping, but non-interfering, measurement sequence by the controlled device is possible (decision 1670). In an embodiment, configuration information such as that of Fig. 17 is used to determine whether such an overlapping measurement configuration is possible. In addition to the considerations discussed above in connection with Fig. 17, the control circuit may in an embodiment consider whether the measurement sequence of the controlled device should be changed. For example, in an embodiment for which an interfering device uses a different measurement sequence than the controlled device, an overlapping measurement sequence may become easier or possible if the controlled device changes its measurement sequence to be more compatible with that of the interfering device.
  • Changing of a device's measurement sequence may in some embodiments make prediction of a device's behavior by other devices more difficult.
  • temporary adjustment of a device's measurement sequence may be a useful option for avoiding interference.
  • the measurement sequence is revised if necessary to achieve the non-interfering overlap (decision 1670 and step 1672).
  • the measurement sequence is started in the next interval if appropriate, or delayed for a suitable number of intervals if needed to achieve a non-interfering measurement sequence (decision 1674 and step 1662).
  • the control circuit changes to a different set of intervals and begins the detection sequence again (decision 1670, steps 1668 and 1634).
  • another approach such as a delay time is used instead of changing to a different set of intervals. Variations of the method of Fig. 16C will be recognized by one of ordinary skill in the art in view of this disclosure.
  • configuration information for compensation measurement sequences of illumination devices may be more complex than that shown in Fig. 17. Additional measurements may be taken in some embodiments, such as additional forward voltage measurements using alternate detectors. In some embodiments of illumination devices storing configuration information for other illumination devices, measurement sequences are not necessarily the same length for each device. In embodiments for which non-sensitive measurements are not necessarily non-interfering measurements, configuration information such as that of Fig. 17 may include quantities defined separately for sensitive measurements and interfering measurements. Analysis in such an embodiment may be more complex than that described for Fig. 17.
  • the improved methods described herein for controlling an illumination device may be used within substantially any LED illumination device having a plurality of emission LED elements and one or more photodetectors. As described in more detail below, the improved methods described herein may be implemented within an LED illumination device in the form of hardware, software or a combination of both.
  • Illumination devices which benefit from the improved methods described herein, may have substantially any form factor including, but not limited to, parabolic lamps (e.g., PAR 20, 30 or 38), linear lamps, flood lights and mini-reflectors.
  • the illumination devices may be installed in a ceiling or wall of a building, and may be connected to an AC mains or some other AC power source.
  • the improved methods described herein may be used within other types of illumination devices powered by other power sources (e.g., batteries or solar energy).
  • Exemplary embodiments of an improved illumination device are described with reference to Figs. 18-21, which show different types of LED illumination devices, each having one or more emitter modules. Although examples are provided herein, the present invention is not limited to any particular type of LED illumination device or emitter module design. A skilled artisan would understand how the method steps described herein may be applied to other types of LED illumination devices having substantially different emitter module designs.
  • Fig. 18A is a photograph of a linear lamp 1810 comprising a plurality of emitter modules (not shown in Fig. 18A), which are spaced apart from one another and arranged generally in a line.
  • each emitter module included within linear lamp 1810 includes a plurality of emission LEDs and at least one dedicated photodetector, all of which are mounted onto a common substrate and encapsulated within a primary optics structure.
  • the primary optics structure may be formed from a variety of different materials and may have substantially any shape and/or dimensions necessary to shape the light emitted by the emission LEDs in a desirable manner. Although the primary optics structure is described below as a dome, one skilled in the art would understand how the primary optics structure may have substantially any other shape or configuration, which encapsulates the emission LEDs and the at least one photodetector.
  • emitter module 1820 includes four differently colored emission LEDs 1830, which are arranged in a square array and placed as close as possible together in the center of a primary optics structure (e.g., a dome) 1840, so as to approximate a centrally located point source.
  • the emission LEDs 1830 may each be configured for producing illumination at a different peak emission wavelength.
  • the emission LEDs 1830 may include RGBW LEDs or RGBY LEDs.
  • a dedicated photodetector 1850 is included within the dome 1840 and arranged somewhere around the periphery of the emission LED array.
  • the dedicated photodetector 1850 may be any device (such as a silicon photodiode or an LED) that produces current indicative of incident light.
  • Figs. 19A and 19B illustrate a substantially different type of illumination device and emitter module design.
  • Fig. 19A depicts an illumination device 1910 having a parabolic form factor (e.g., a PAR 38) and a single emitter module (not shown in Fig. 19A).
  • the emitter modules included in such devices typically include a plurality of differently colored chains of LEDs (LED elements), where each chain includes two or more LEDs of the same color.
  • Fig. 19B illustrates an exemplary emitter module 1920 that may be included within the PAR lamp 1910 shown in Fig. 19A.
  • emitter module 1920 includes an array of emission LEDs 1930 and a plurality of dedicated photodetectors 1950, all of which are mounted on a common substrate and encapsulated within a primary optics structure (e.g., a dome) 1940.
  • the array of emission LEDs 1930 may include a number of differently colored chains of LEDS, wherein each chain is configured for producing illumination at a different peak emission wavelength.
  • the array of emission LEDs 1930 may include a chain of four red LEDs, a chain of four green LEDs, a chain of four blue LEDs, and a chain of four white or yellow LEDs. Each chain of LEDs is coupled in series and driven with the same drive current.
  • the individual LEDs in each chain may be scattered about the array, and arranged so that no color appears twice in any row, column or diagonal, to improve color mixing within the emitter module 1920.
  • the dedicated photodetectors 1950 are included within the dome 1940 and arranged around the periphery of the array.
  • the dedicated photodetectors 1950 may be placed close to, and in the middle of, each edge of the array and may be connected in parallel to a receiver of the illumination device. By connecting the dedicated photodetectors 1950 in parallel with the receiver, the photocurrents induced on each photodetector may be summed to minimize the spatial variation between the similarly colored LEDs, which may be scattered about the array.
  • the dedicated photodetectors 1950 may be any devices that produce current indicative of incident light (such as a silicon photodiode or an LED). In one embodiment, however, the dedicated photodetectors 1950 are preferably LEDs with peak emission wavelengths in the range of 500nm to 700nm.
  • Photodetectors with such peak emission wavelengths will not produce photocurrent in response to infrared light, which reduces interference from ambient light.
  • methods as described herein may be used to minimize compensation errors caused by such ambient light. For example, effects of a constant ambient illumination on a photocurrent measurement may be removed by subtraction as discussed above.
  • methods as described herein may be used to avoid taking photocurrent measurements in the presence of such non-constant illumination.
  • the illumination devices shown in Figs. 18A and 19A and the emitter modules shown in Figs. 18B and 19B are provided merely as examples of illumination devices in which the interference-resistant compensation methods described herein may be used. Further description of these illumination devices and emitter modules may be found in U.S. Patent Application No. 14/097,339 and U.S. Provisional Patent Application No. 61/886,471, which are commonly assigned and incorporated herein by reference in their entirety. Still further description of additional emitter module embodiments may be found in co-pending U.S. Patent Application No. 14/314,530.
  • inventive concepts described herein are not limited to any particular type of LED illumination device, any particular number of emitter modules that may be included within an LED illumination device, or any particular number, color or arrangement of emission LEDs and photodetectors that may be included within an emitter module.
  • the methods described herein may contemplate only an LED illumination device including a plurality of emission LEDs and at least one photodetector.
  • a dedicated photodetector may not be required, if one or more of the emission LEDs is configured, at times, to provide such functionality.
  • Fig. 20 is one example of a block diagram of an illumination device 2000 configured to avoid interference-related errors when compensating for variations in parameters such as drive current, temperature, and LED characteristics.
  • the illumination device illustrated in Fig. 20 provides one example of the hardware and/or software that may be used to implement interference-resistant measurement methods such as those shown in Figs. 16A through 16C.
  • illumination device 2000 comprises a plurality of emission LED elements 2045 and one or more dedicated photodetectors 2050.
  • the emission LED elements 2045 comprise four chains of any number of LEDs. In typical embodiments, each chain may have 2 to 4 LEDs of the same color, which are coupled in series and configured to receive the same drive current.
  • the emission LED elements 2045 may include a chain of red LEDs, a chain of green LEDs, a chain of blue LEDs, and a chain of white or yellow LEDs.
  • the methods and devices described herein are not limited to any particular number of LED chains, any particular number of LEDs within the chains, or any particular color or combination of LED colors.
  • the methods and devices described herein are not limited to any particular type, number, color, combination or arrangement of photodetectors.
  • the one or more dedicated photodetectors 2050 may include a small red, orange or yellow LED.
  • the one or more dedicated photodetectors 128 may include one or more small red LEDs and one or more small green LEDs.
  • one or more of the dedicated photodetector(s) 2050 shown in Fig. 20 may be omitted if one or more of the emission LEDs 2045 is configured, at times, to function as a photodetector.
  • the plurality of emission LEDs 2045 and the (optional) dedicated photodetectors 2050 may be included within an emitter module, as discussed above.
  • an illumination device may include more than one emitter module, as discussed above.
  • illumination device 2000 includes various hardware and software components, which are configured for powering the illumination device and controlling the light output from the emitter module(s).
  • the illumination device is connected to AC mains 2005, and includes an AC/DC converter 2010 for converting AC mains power (e.g., 120V or 240V) to a DC voltage (V D C).
  • this DC voltage e.g., 15V
  • the LED driver and receiver circuit 2040 for producing the operative drive currents applied to the emission LEDs 2045 for producing illumination.
  • a DC/DC converter 2015 is included for converting the DC voltage V D C (e.g., 15V) to a lower voltage V L (e.g., 3.3V), which is used to power the low voltage circuitry included within the illumination device, such as PLL 2020, wireless interface 2025, and control circuit 2035.
  • PLL 2020 locks to the AC mains frequency (e.g., 50 or 60 HZ) and produces a high speed clock (CLK) signal and a synchronization signal (SYNC).
  • CLK high speed clock
  • SYNC synchronization signal
  • the CLK signal provides the timing for control circuit 2035 and LED driver and receiver circuit 2040.
  • the CLK signal frequency is in the tens of MHz range (e.g., 23MHz), and is precisely synchronized to the AC Mains frequency and phase.
  • the SYNC signal is used by the control circuit 2035 to create the timing of the intervals used for the detection and compensation measurements described above.
  • the SYNC signal frequency is equal to the AC Mains frequency (e.g., 50 or 60 HZ) and also has a precise phase alignment with the AC Mains.
  • the SYNC signal frequency is an integral multiple of the AC mains frequency.
  • timing reference signal 1520 of Fig. 15 is an example of the SYNC signal of Fig. 20.
  • a wireless interface 2025 may be included and used to calibrate the illumination device 2000 during manufacturing.
  • an external calibration tool (not shown in Fig. 20) may communicate calibration values (e.g., luminous flux, chromaticity and/or other optical measurement values) to an illumination device under test via the wireless interface 2025.
  • the calibration values received via the wireless interface 2025 may be stored in the table of calibration values within a storage medium 2030 of the control circuit 2035, for example.
  • the control circuit 2035 may use the calibration values to generate calibration coefficients, which are stored within the storage medium 2030 in addition to, or in lieu of, the received calibration values.
  • Wireless interface 2025 is not limited to receiving only calibration data, and may be used for communicating information and commands for many other purposes.
  • wireless interface 2025 could be used during normal operation to communicate commands, which may be used to control the illumination device 2000, or to obtain information about the illumination device 2000.
  • commands may be communicated to the illumination device 2000 via the wireless interface 2025 to turn the illumination device on/off, to control the dimming level and/or color set point of the illumination device, to initiate the calibration procedure, or to store calibration results in memory.
  • wireless interface 2025 may be used to obtain status information or fault condition codes associated with illumination device 2000.
  • wireless interface 2025 could operate according to ZigBee, WiFi, Bluetooth, or any other proprietary or standard wireless data communication protocol. In other embodiments, wireless interface 2025 could communicate using radio frequency (RF), infrared (IR) light or visible light. In alternative embodiments, a wired interface could be used, in place of the wireless interface 2025 shown, to communicate information, data and/or commands over the AC mains or a dedicated conductor or set of conductors.
  • RF radio frequency
  • IR infrared
  • a wired interface could be used, in place of the wireless interface 2025 shown, to communicate information, data and/or commands over the AC mains or a dedicated conductor or set of conductors.
  • the control circuit 2035 uses the timing signals received from PLL 2020 to calculate and produces values indicating the desired drive current to be used for each LED chain 2045. This information may be communicated from the control circuit 2035 to the LED driver and receiver circuit 2040 over a serial bus conforming to a standard, such as SPI or I 2 C, for example. In addition, the control circuit 2035 may provide a latching signal that instructs the LED driver and receiver circuit 2040 to simultaneously change the drive currents supplied to each of the LEDs 2045 to prevent brightness and color artifacts.
  • Control circuit 2035 may be configured for determining the respective drive currents needed to achieve a desired luminous flux and/or a desired chromaticity for the illumination device in accordance with one or more compensation methods as described above in connection with Figs. 6-9 and described further in the co-pending applications referenced herein.
  • Control circuit 2035 is further configured for operations described herein in connection with avoiding interference. Depending on the particular embodiment such operations include, for example, determining whether an interfering photocurrent measurement is made by another device during a detection interval or measurement interval, waiting for a delay time before continuing to monitor detection intervals, changing to a different series of intervals, determining whether detection has indicated that compensation measurements may be started without likely interference, or determining the measurement sequence used by an interfering device.
  • control circuit 2035 may determine the respective drive currents and perform the interference-related operations described herein by executing program instructions stored within the storage medium 2030.
  • the storage medium may be a non- volatile memory, and may be configured for storing the program instructions along with a table of calibration values used in the compensation methods and a data structure including configuration information such as that of Fig. 17.
  • the control circuit 2035 may include combinational logic for determining the desired drive currents or performing other operations, such that program instructions for determining drive currents are not stored on storage medium 2030.
  • operations of control circuit 2035 may be carried out using a combination of program instructions and combinational logic.
  • Storage medium 2030 includes a plurality of storage locations addressable by control circuit 2035 or a processor such as that associated with controller 2190 in Fig. 21 for storing software programs and data associated with the methods described herein.
  • storage medium 2030 and other memory or storage media described herein may be implemented using any combination of built-in volatile or non- volatile memory, including random-access memory (RAM) and read-only memory (ROM) and integrated or peripheral storage devices such as magnetic disks, optical disks, solid state drives or flash drives.
  • RAM random-access memory
  • ROM read-only memory
  • storage medium 2030 may be used to store one or more counters such as the collision counter, free interval counter, and contiguous free interval counters described in connection with Figs. 16B and 16C above.
  • the LED driver and receiver circuit 2040 may include a number (N) of driver blocks 2115 equal to the number of emission LED chains 2045 included within the illumination device.
  • LED driver and receiver circuit 2040 comprises four driver blocks 2115, each configured to produce illumination from a different one of the emission LED chains 2045.
  • the LED driver and receiver circuit 2040 also comprises the circuitry needed to measure ambient temperature (optional), the detector and/or emitter forward voltages, and the detector photocurrents, and to adjust the LED drive currents accordingly.
  • Each driver block 2115 receives data indicating a desired drive current from the control circuit 2035, along with a latching signal indicating when the driver block 2115 should change the drive current.
  • Fig. 21 is an exemplary block diagram of an LED driver and receiver circuit 2040, according to one embodiment of the invention.
  • the LED driver and receiver circuit 2040 includes four driver blocks 2115, each block including a buck converter 2120, a current source 2125, and an LC filter 2145 for generating the drive currents that are supplied to a connected emission LED element 2045(a) to produce illumination and obtain forward voltage (Vfe) measurements.
  • buck converter 2120 may produce a pulse width modulated (PWM) voltage output (Vdr) when the controller 2190 drives the "Out En" signal high.
  • PWM pulse width modulated
  • This voltage signal (Vdr) is filtered by the LC filter 2145 to produce a forward voltage on the anode of the connected LED chain 2045(a).
  • the cathode of the LED chain is connected to the current source 2125, which forces a fixed drive current equal to the value provided by the "Emitter Current” signal through the LED chain 2045(a) when the "Led On” signal is high.
  • the "Vc" signal from the current source 2125 provides feedback to the buck converter 2120 to output the proper duty cycle and minimize the voltage drop across the current source 2125.
  • each driver block 2115 includes a difference amplifier 2140 for measuring the forward voltage drop (Vfe) across the chain of emission LEDs 2045a.
  • the buck converter 2120 is turned off and the current source 2125 is configured for drawing a relatively small drive current (e.g., about 1mA) through the connected chain of emission LEDs 2045(a).
  • the voltage drop (Vfe) produced across the LED chain 2045(a) by that current is measured by the difference amplifier 2140.
  • the difference amplifier 2140 produces a signal that is equal to the forward voltage (Vfe) drop across the emission LED chain 2045(a) during forward voltage measurements.
  • the driver blocks 2115 may include additional circuitry for measuring the photocurrents (Iph_d2), which are induced across an emission LED, when the emission LED is configured for detecting incident light.
  • each driver block 2115 may include a transimpedance amplifier 2130, which generally functions to convert an input current to an output voltage proportional to a feedback resistance. As shown in Fig.
  • transimpedance amplifier 2130 the positive terminal of transimpedance amplifier 2130 is connected to the Vdr output of the buck converter 2120, while the negative terminal is connected to the cathode of the last LED in the LED chain 2045(a).
  • Transimpedance amplifier 2130 is enabled when the "LED On” signal is low. When the "LED On” signal is high, the output of transimpedance amplifier 2130 is tri-stated.
  • the buck converters 2120 connected to all other emission LEDs should be turned off to avoid visual artifacts produced by LED current transients.
  • the buck converter 2120 coupled to the emission LED under test should also be turned off to prevent switching noise within the buck converter from interfering with the photocurrent measurements.
  • the Vdr output of the buck converter 2120 coupled to the emission LED under test is held to a particular value (e.g., about 2-3.5 volts times the number of emission LEDs in the chain) by the capacitor within LC filter 2145.
  • the transimpedance amplifier 2130 When this voltage (Vdr) is supplied to the anode of emission LED under test and the positive terminal of the transimpedance amplifier 2130, the transimpedance amplifier produces an output voltage (relative to Vdr) that is supplied to the positive terminal of difference amplifier 2135.
  • Difference amplifier 2135 compares the output voltage of transimpedance amplifier 2130 to Vdr and generates a difference signal, which corresponds to the photocurrent (Iph_d2) induced across the LED chain 2045(a).
  • the LED driver and receiver circuit 2040 may include one or more receiver blocks 2150 for measuring the forward voltages (Vfd) and photocurrents (Iph dl or Iph_d2) induced across the one or more dedicated photodetectors 2050. Although only one receiver block 2150 is shown in Fig. 21, the LED driver and receiver circuit 2040 may generally include a number of receiver blocks 2150 equal to the number of dedicated photodetectors included within the emitter module.
  • receiver block 2150 comprises a voltage source 2155, which is coupled for supplying a DC voltage (Vdr) to the anode of the dedicated photodetector 2050 coupled to the receiver block, while the cathode of the photodetector 2050 is connected to current source 2160.
  • Vdr DC voltage
  • the controller 2190 supplies a "Detector On” signal to the current source 2160, which forces a fixed drive current (Idrv) equal to the value provided by the "Detector Current” signal through photodetector 2050.
  • current source 2160 When obtaining detector forward voltage (Vfd) measurements, current source 2160 is configured for drawing a relatively small amount of drive current (Idrv) through photodetector 2050.
  • the voltage drop (Vfd) produced across photodetector 2050 by that current is measured by difference amplifier 2175, which produces a signal equal to the forward voltage (Vfd) drop across photodetector 2050.
  • photodetector 2050 by the current source 2160 is generally a relatively small, non-operative drive current.
  • the non-operative drive current may be roughly 1mA.
  • smaller/larger drive currents may be used in embodiments that include fewer/greater numbers of photodetectors, or embodiments that do not connect the photodetectors in parallel.
  • receiver block 2150 also includes circuitry for measuring the photocurrents (Iph dl or Iph_d2) induced on photodetector 2050 by ambient light, as well as light emitted by the emission LEDs. As shown in Fig. 21, the positive terminal of
  • transimpedance amplifier 2165 is coupled to the Vdr output of voltage source 2155, while the negative terminal is connected to the cathode of photodetector 2050. When connected in this manner, the transimpedance amplifier 2165 produces an output voltage relative to Vdr (e.g., about 0-lV), which is supplied to the positive terminal of difference amplifier 2170. Difference amplifier 2170 compares the output voltage to Vdr and generates a difference signal, which corresponds to the photocurrent (Iph dl or Iph_d2) induced across photodetector 2050. Transimpedance amplifier 2165 is enabled when the "Detector On" signal is low. When the "Detector On” signal is high, the output of transimpedance amplifier 2165 is tri-stated.
  • Vdr e.g., about 0-lV
  • some embodiments of the invention may scatter the individual LEDs within each chain of LEDs 2045 about the array of LEDs, so that no two LEDs of the same color exist in any row, column or diagonal (see, e.g., Fig. 19B).
  • the photocurrents (Iph dl or Iph_d2) induced on each photodetector 2050 by the LEDs of a given color may be summed to minimize the spatial variation between the similarly colored LEDs, which are scattered about the array.
  • the LED driver and receiver circuit 2040 may also include a multiplexor (Mux) 2180, an analog to digital converter (ADC) 2185, a controller 2190, and an optional temperature sensor 2195.
  • multiplexor 2180 may be coupled for receiving the emitter forward voltage (Vfe) and the (optional) photocurrent (Iph_d2)
  • the ADC 2185 digitizes the emitter forward voltage (Vfe) and the optional photocurrent (Iph_d2) measurements output from the driver blocks 2115, and the detector forward voltage (Vfd) and detector photocurrent (Iph dl and/or Iph_d2) measurements output from the receiver block 2150, and provides the results to the controller 2190.
  • the controller 2190 determines when to take forward voltage and photocurrent measurements and produces the Out En, Emitter Current and Led On signals, which are supplied to the driver blocks 2115, and the Detector Current and Detector On signals, which are supplied to the receiver block 2150 as shown in Fig. 21.
  • the LED driver and receiver circuit 2040 may include an optional temperature sensor 2195 for taking ambient temperature (Ta) measurements.
  • multiplexor 2180 may also be coupled for multiplexing the ambient temperature (Ta) with the forward voltage and photocurrent measurements sent to the ADC 2185.
  • the temperature sensor 2195 may be a thermistor, and may be included on the driver circuit chip for measuring the ambient temperature surrounding the LEDs, or a temperature from the heat sink of the emitter module. If the optional temperature sensor 2195 is included, the output of the temperature sensor may be used in some embodiments to determine if a significant change in temperature is detected. In some embodiments detection of a significant change in temperature may cause compensation measurements to be initiated.
  • FIG. 20-21 One implementation of an improved illumination device 2000 has now been described in reference to Figs. 20-21. Further description of such an illumination device may be found in commonly assigned U.S. Application Serial Nos. 13/970,944; 13/970,964; 13/970,990; and 14/097,339. A skilled artisan would understand how the illumination device could be alternatively implemented within the scope of the methods and devices described herein.
  • FIG. 22 An exemplary block diagram of circuit components for an illumination device including multiple emitter modules is shown in Fig. 22.
  • the circuit components are housed on a power supply board 2202 and emitter board 2204 which are dimensioned to fit within the housing of a linear illumination device.
  • An external view of an embodiment of such a linear illumination device is shown in Fig. 18A.
  • Emitter board 2204 in the embodiment of Fig. 22 includes 6 emitter modules 2212 arranged in a linear row.
  • a representation of a top view of an exemplary embodiment of emitter module 2212 is shown in Fig. 18B.
  • power supply board 2202 comprises AC/DC converter 2206 and controller 2208.
  • AC/DC converter 2206 converters AC mains power to a DC voltage of typically 15-20V, which is then used to power controller 2208 and emitter board 2204. The DC voltage from AC/DC converter 2206 may be converted to lower voltages as well elsewhere within the illumination device.
  • Controller 2208 communicates with emitter board 2204 through a digital control bus, in this example. Controller 2208 could comprise a wireless, power line, or any other type of communication interface to enable the color of the linear illumination device to be adjusted.
  • controller 2208 also provides to each of interface circuits 2210 a timing signal and an offset from the timing signal at which measurement intervals and/or detection intervals for the associated emitter module are to occur.
  • adjacently positioned emitter modules within the illumination device are assigned different offsets from the timing reference, so that compensation measurements performed by adjacent emitter modules are performed using non-overlapping sets of intervals.
  • an illumination device including six emitter modules such as that illustrated in Fig. 22 uses three different offsets from a timing reference: a first offset for the first and fourth emitter modules (counting from one end of the device), a second offset for the second and fifth emitter modules, and a third offset for the third and sixth emitter modules.
  • a different number of offsets may be used, including the use of a different offset for each individual emitter module.
  • emitter board 2204 comprises six emitter modules 2212 and six interface circuits 2210.
  • Interface circuits 2210 communicate with controller 2208 over the digital control bus and produce the drive currents supplied to the LEDs within the emitter modules 2212.
  • Fig. 23 illustrates exemplary circuitry that may be included within interface circuitry 2210 and emitter modules 2212.
  • Interface circuitry 2210 comprises control logic 2302, LED drivers 2304, and receiver 2306.
  • Emitter module 2212 comprises emission LEDs 2308 and a detector 2310.
  • Control logic 2302 may comprise a microcontroller or special logic, and communicates with controller 2208 over the digital control bus.
  • Control logic 2302 also sets the drive current produced by LED drivers 2304 to adjust the color and/or intensity of the light produced by emission LEDs 2308, and manages receiver 2306 to monitor the light produced by each individual LED 2308 via detector 2310.
  • control logic 2302 may comprise memory for storing calibration information necessary for maintaining precise color, or alternatively, such information could be stored in controller 2208.
  • other information used in performing the methods described herein is in some embodiments stored in memory locations within control logic 2302, within controller 2208, or distributed between both of these circuits. Such other information may include configuration information such as that discussed in connection with Fig. 17 above.
  • the circuit components on power supply board 2202 are identical to the circuit components on power supply board 2202.
  • control circuit 2035 is implemented in a similar manner as the power supply and control circuitry shown in Fig. 20, including AC/DC converter 2010, DC/DC converter 2015, PLL 2020, wireless interface 2025, and control circuit 2035.
  • interface circuit 2210 is in some embodiments implemented in a manner similar to driver and receiver circuit 2040 shown in Figs. 20-21.
  • LEDs 2308 and detector 2310 are in some embodiments implemented using LED chains 2045 and detectors 2050 of Fig. 20, respectively.
  • Functions of control circuit 2035 in Fig. 20 may in some embodiments be distributed between control logic 2302 of Fig. 23 and controller 2208 of Fig. 22. In some embodiments, certain functions of control circuit 2035 may be duplicated in both controller 2208 and control logic 2302.
  • Controller 2208 may also be referred to as a device control circuit herein.
  • the device control circuit is configured to control the entire illumination device.
  • Control logic 2302 may also be referred to herein as a module control circuit for its respective emitter module 2212.
  • the module control circuit is configured to control functionality of its respective emitter module, including performance of compensation measurements and adjustment of illumination settings. Certain functions of the module control circuits may in some embodiments be performed by the device control circuit 2208.

Landscapes

  • Circuit Arrangement For Electric Light Sources In General (AREA)

Abstract

Dans certains modes de réalisation, l'invention concerne des procédés et des dispositifs d'éclairage prévus pour une compensation résistant aux interférences dans des dispositifs d'éclairage ou des lampes comprenant des dispositifs à diodes électroluminescentes (LED). Spécifiquement, l'invention concerne des procédés permettant d'éviter les erreurs liées aux interférences lors de la compensation de LED individuelles dans un dispositif d'éclairage en ce qui concerne des variations de quantités, comme le courant d'actionnement et la température. Dans un mode de réalisation, un dispositif d'éclairage peut comprendre une lampe (ou module émetteur) comprenant des éléments LED à émissions multiples, un ou plusieurs photodétecteurs et un circuit de commande, lequel circuit de commande est adapté pour exécuter les étapes du procédé.
PCT/US2015/035081 2014-10-09 2015-06-10 Compensation résistant aux interférences dans des dispositifs d'éclairage comprenant des diodes électroluminescentes WO2016057089A1 (fr)

Applications Claiming Priority (8)

Application Number Priority Date Filing Date Title
US14/510,212 2014-10-09
US14/510,243 US9247605B1 (en) 2013-08-20 2014-10-09 Interference-resistant compensation for illumination devices
US14/510,283 2014-10-09
US14/510,266 2014-10-09
US14/510,212 US9155155B1 (en) 2013-08-20 2014-10-09 Overlapping measurement sequences for interference-resistant compensation in light emitting diode devices
US14/510,243 2014-10-09
US14/510,266 US9345097B1 (en) 2013-08-20 2014-10-09 Interference-resistant compensation for illumination devices using multiple series of measurement intervals
US14/510,283 US9332598B1 (en) 2013-08-20 2014-10-09 Interference-resistant compensation for illumination devices having multiple emitter modules

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WO2016057089A1 true WO2016057089A1 (fr) 2016-04-14

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CN110763241A (zh) * 2019-12-30 2020-02-07 湖南卫导信息科技有限公司 一种同步角度闪烁的导航干扰信号发射方法与系统
CN117312811A (zh) * 2023-12-01 2023-12-29 深圳市胜天光电技术有限公司 一种led灯珠的性能评估方法、系统及存储介质

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WO2007004108A1 (fr) * 2005-06-30 2007-01-11 Koninklijke Philips Electronics N.V. Procédé et système de contrôle de puissance d’un luminaire
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US20120056545A1 (en) * 2009-05-08 2012-03-08 Koninklijke Philips Electronics N.V. circuit for and a method of sensing a property of light

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EP1482770A1 (fr) * 2002-03-01 2004-12-01 Sharp Kabushiki Kaisha Dispositif emetteur lumiere et affichage utilisant ce dispositif et dispositif de lecture
WO2007004108A1 (fr) * 2005-06-30 2007-01-11 Koninklijke Philips Electronics N.V. Procédé et système de contrôle de puissance d’un luminaire
DE102007036978A1 (de) * 2007-08-06 2009-02-12 Tridonicatco Gmbh & Co. Kg Vorrichtung und Verfahren zur Steuerung der Lichtabgabe
US20120056545A1 (en) * 2009-05-08 2012-03-08 Koninklijke Philips Electronics N.V. circuit for and a method of sensing a property of light

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN110763241A (zh) * 2019-12-30 2020-02-07 湖南卫导信息科技有限公司 一种同步角度闪烁的导航干扰信号发射方法与系统
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CN117312811A (zh) * 2023-12-01 2023-12-29 深圳市胜天光电技术有限公司 一种led灯珠的性能评估方法、系统及存储介质
CN117312811B (zh) * 2023-12-01 2024-02-23 深圳市胜天光电技术有限公司 一种led灯珠的性能评估方法、系统及存储介质

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