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
  • 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
  • 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
• • 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
  • H05B47/115—Controlling the light source in response to determined parameters by determining the presence or movement of objects or living beings
  • H05B47/125—Controlling the light source in response to determined parameters by determining the presence or movement of objects or living beings by using cameras
• • 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

• the present invention relates to method of self-calibrating a lighting device, and a lighting device arranged to perform the method.
• Lighting systems are becoming increasingly intelligent to respond to a growing demand for personalization, efficiency and simplicity.
• lighting devices have been developed to address these demands.
• the lighting device called LumiMotion includes a camera and a processing unit to detect the presence of a person close to the lighting device, and temporarily turn on the lighting device or increase its light output. When it is not trigged the lighting device is dimmed or fully turned off.
• a so called tuneable white lighting device which enhances the look of illuminated products.
• the lighting device is arranged to determine appropriate settings by analyzing the colors of the illuminated products by means of image processing using an embedded camera and a processing unit. The appropriate settings are automatically chosen by the lighting device.
• lighting devices having sensing capabilities as described above are designed to adapt their light output depending on the scene and situation they are observing.
• a calibration step is typically required. Relevant information to be acquired during the calibration can be for instance; spatial footprint of the light, amount and type of light provided in different parts of the scene, ambient illumination, scene layout and appearance, etc.
• different calibration strategies can be designed, but they are typically based on capturing one image of the scene with the light output of the lighting device turned off, and one image with the light output set to a predetermined value.
• there is a problem of changes in the scene during the calibration e.g.
• the object is achieved by a method according to the present invention as defined in claim 1 , and by a lighting device according to the present invention as defined in claim 12.
• a method of self-calibrating a lighting device comprising:
• the advantage of this method is that the lighting device does not begin the calibration until there is no significant disturbance in the area which is used for the calibration. Disturbances such as other lighting devices performing a calibration are detected and avoided. This behavior is truly autonomous as well, and thereby there is no need for a common central controller in case of several lighting devices affecting each other.
• the set of relevant changes includes detecting any movement of an object.
• the monitoring time is divided in time portions, which are separated in time. Thereby, flexibility is introduced in the monitoring operation.
• said monitoring comprising capturing images of the calibration area and comparing the images with each other.
• said detecting any change is preceded by one of:
• determining the monitoring time by picking a next monitoring time of a predetermined sequence of monitoring times.
• Any one of these alternatives provides for a high likelihood that the calibration of two or more lighting devices affecting each other, and being simultaneously turned on, will be separated in time.
• time is divided into frames and the monitoring time is predetermined and encompasses at least one frame, and is moved ahead at least one frame for each repetition of said detecting any relevant change.
• the method comprises performing an initialization at power up of the lighting device before said monitoring. This initialization gives room for different initial actions.
• the initialization comprises waiting a waiting period during which the light output of the lighting device is off. For instance, if the lighting device is the only one that has impact on the calibration area, or if there are several lighting devices, which are simultaneously turned on, then this embodiment enables for example determination of ambient light.
• said initialization comprising setting a predetermined light output level and estimating an exposure time for images to be taken by the lighting device.
• said initialization comprising capturing an image while keeping the light output off.
• said calibrating the light settings comprises:
• a lighting device comprising:
• At least one tuneable light source arranged to provide several different light output settings
• control unit is arranged to monitor, by means of the optical sensor, a calibration area, which encompasses at least a part of an area being illuminable by the lighting device, and to calibrate the light output settings of the lighting device;
• control unit when monitoring the calibration area, is arranged to repeat:
• any relevant change out of a set of relevant changes comprising at least a light intensity change, in the calibration area during a monitoring time, while keeping the light output of the lighting device constant;
• the lighting device provides advantages corresponding to those of the method.
• Fig. 1 is a block diagram of a lighting device according to an embodiment of the present invention.
• Fig. 2 is a flow chart of a method of self-calibrating the lighting device of Fig. 1, according to an embodiment of the present invention
• Fig. 3 illustrates illumination areas of an arrangement of several lighting devices according to Fig. 1;
• Fig. 4 is a time schedule illustrating an example of a self-calibration process with the lighting devices of Fig. 3.
• a lighting device 100 for performing the present method, it comprises a light source 102, an optical sensor 104, and a control unit 106, as shown in Fig. 1.
• the optical sensor comprises a camera 108.
• the control unit 106 is connected with the light source 102 and the optical sensor 104.
• the method comprises the operations of monitoring a calibration area, which encompasses at least a part of an area being illuminable by the lighting device; and calibrating the light output settings of the lighting device.
• the calibration area corresponds with the illumination area of the lighting device 100, i.e. the area that is illuminated by the lighting device 100.
• Fig. 3 illustrates the illumination areas 302, 304, 306, 308 of four different, but similar, lighting devices.
• the calibration area that is the area of the surroundings of the lighting device that is to be used as a basis for self-calibrating the lighting device 100, can differ from the illumination area 302, 304, 306, 308, and can be both larger and smaller, but it covers at least a part of the illumination area.
• the calibration area corresponds with the illumination area
• the calibration area 302, 304, 306, 308 of each one of the four lighting devices LI, L2, L3, L4 is influenced by light coming from at least one of the other lighting devices.
• all four lighting devices 100 are powered by the same main switch 110, which is common in most environments where this kind of intelligent lighting is used, such as shops and outdoor environments, e.g. along roads and in parking lots, where at least a segment of the area are powered by the same main switch.
• all lighting devices L1-L4 can be powered at the same time.
• the operation of monitoring comprises repeating:
• any relevant change out of a set of relevant changes comprising at least a light intensity change, in the calibration area during a monitoring time, while keeping the light output of the lighting device constant, see box 202 in Fig. 2;
• the monitoring time starts when the lighting devices are powered, and the lighting devices all have different monitoring times tl, t2, t3, and t4.
• One way is to determine, at powering, a random time within a time interval of an appropriate length. For instance, the monitoring time can range from a fraction of a second to a few seconds.
• Another way to determine the monitoring time is to determine the monitoring time by picking a next monitoring time of a predetermined sequence of monitoring times.
• the lighting device performs a calibration operation, in box 206. However, only if there has been no significant change in the calibration area during the monitoring operation, as determined in box 204. This is explained by means of the exemplifying time schedule of Fig. 4 as follows.
• the first lighting device LI has the shortest monitoring time tl . It is assumed that no significant change has occurred during tl . Then the first lighting device LI starts the calibration operation at the end of tl by turning its light off, or in this embodiment keeping its light off, as it has been turned off during the monitoring time, and capturing a first image with the camera 108 of its optical sensor 104. Then the first lighting device LI sets its light output to a predetermined value and captures a second image.
• the second lighting device L2 During the monitoring time t2, where tl ⁇ t2 ⁇ (tl+T), of the second lighting device L2, it detects at least one change of the light output of the first lighting device LI, which influence a part of the calibration area 302 of the second lighting device L2.
• the control unit of the second lighting device L2 determines the amount of change of at least one of the changes to be significant, i.e. it is not below the limit. Therefore, the method returns to the operation of setting the monitoring time. A new monitoring time t5 is determined, and the monitoring is resumed.
• the fourth lighting device L4 has not detected any change during its monitoring time t4, where t4>t2.
• the third lighting device L3 has the longest monitoring time t3 of all of the lighting devices, in this example, and the calibration area 306 of the third lighting device L3 is influenced by the light output of both the second and the fourth lighting device L2, L4.
• the third lighting device L3 detects a significant change of the light intensity of its calibration area 306 due to at least one change of the light output of the fourth lighting device L4, and returns to determine a new monitoring time t6 and start monitoring again.
• Next event in time is the time out of the second monitoring time t5 of the second lighting device L2.
• the first lighting device LI was still calibrating and changed its light output significantly. Consequently, the second lighting device L2 resumes monitoring during a third time period t7.
• the second monitoring time t6 of the third lighting device L3 ends, and it starts a third monitoring time t8, since a change of the light output of the fourth lighting device L4 was detected during its calibration.
• the third monitoring time t8 of the third lighting device L3 ends, and it starts calibrating its light output.
• This calibration causes a change that is detected as a significant change by the third lighting device L3, which causes a fourth monitoring time t9 to be generated by the third lighting device L3.
• the third lighting device L3 calibrates its light output as well.
• the calibration operation is finished with setting an optimized light output value of the lighting device, in box 208.
• the calibration operation typically involves capturing a first image with the light output turned off, and capturing a second image with a
• the predetermined light output which can be a maximum light output level or some other appropriate level.
• the final setting is typically dependent on inter alia the ambient illumination. It should be noted that in the example above, when the second lighting device L2 performs the calibration, the final optimal light output setting of the first lighting device LI contributes to the ambient illumination. Similarly, when the third lighting device L3 is self-calibrating the ambient illumination includes contributions from both the second and the fourth lighting devices L2, L4.
• the monitoring operation in this embodiment, involves sequentially capturing images during the monitoring time, and consecutively comparing a captured image with the previous image to detect any significant change. In addition to, or instead of, detecting a change of illuminance several other parameters are possible to monitor.
• time is divided into frames, and the monitoring time encompasses at least one frame, and is moved ahead at least one frame for each repetition of detecting any relevant change.
• the detection of changes is performed every N>1 frames.
• a moving window of a number of frames k can be used, such that the control unit 106 continuously determines whether a significant change has occurred during the last k frames. If the answer is no, then the calibration operation is performed.
• the limit between an insignificant change and a significant change can be adaptive. For example, the limit can be raised each time a significant change is detected, such that larger and larger changes are allowed with time passing. Other kinds of adaption are basing the limit on historic data, on image statistics, on user's input, on the time of the day the calibration is performed, etc.
• an initialization is performed at power up of the lighting device before said monitoring, in box 200.
• the lighting devices L1-L4 has an initial period available for different kind of preparations before the monitoring starts.
• the initialization can be used for e.g. waiting a period during which the light output of the lighting device is off, which waiting period can be randomly determined. Additionally, during such a waiting period without light output, an image of the ambient illumination can be captured.
• Such an image is useful at the end of the calibration in order to discriminate not only between the own contribution to the illuminance and ambient illuminance, which may include a contribution from nearby lighting devices, but also to discriminate between the contribution of the basic ambient illuminance and contribution of other lighting devices.
• This information is valuable to infer the lighting system layout, to estimate and monitor ambient illumination that slowly changes over time, and in general to improve all vision based algorithms. As regards improving vision based algorithms, for instance the control unit will be able to discard changes caused by other lighting devices which modify their light output level.
• Yet another alternative employment of the initialization operation is to set the lighting device, and thus all lighting devices to a predetermined light output level, e.g. a maximum light output, for some duration, and estimate an appropriate exposure time for the camera 108 in order for the camera 108 to be able to capture images without clipping.
• the waiting time can be relatively long since some lighting devices has a long starting time before they emit at full brightness.
• Such lighting devices naturally have impact on other times as well, such as the calibration time, since they are generally slow in making large changes of light output.
• the user can be offered an opportunity to set the times or the character of the times.

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

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• 2013
  • 2013-09-25 US US14/433,060 patent/US9320113B2/en active Active
  • 2013-09-25 EP EP13814609.7A patent/EP2904879B1/en active Active
  • 2013-09-25 WO PCT/IB2013/058844 patent/WO2014053954A1/en not_active Ceased
  • 2013-09-25 CN CN201380052130.3A patent/CN104823524B/zh active Active
  • 2013-09-25 RU RU2015116895A patent/RU2642849C2/ru active
  • 2013-09-25 JP JP2015535135A patent/JP6243432B2/ja active Active

Patent Citations (6)

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