Patent Publication Number: US-8115398-B2

Title: System and method for performing an illumination copy and paste operation in a lighting system

Description:
This application is a national stage application under 35 U.S.C. §371 of International Application No. PCT/IB2007/053543 filed on Sep. 3, 2007, and published in the English language on Mar. 20, 2008 as International Publication No. WO/2008/032236, which claims priority to European Application No. 06120533.2, filed on Sep. 12, 2006, incorporated herein by reference. 
     The invention relates to copying light conditions from one location and pasting into or providing similar light conditions to another location in a lighting system. 
     The adjustment of parameters such as the illumination intensity and color in modem lighting systems is often difficult and tedious due to the plurality of light sources. Therefore, specific technical methods may be used to adjust the lighting parameters, for example computer programs processing signals from sensors measuring certain light attributes, such as the intensity and color of an illumination generated by the light sources, and generating signals for controlling the light sources in order to obtain certain lighting conditions. Often it is desired in a lighting system to obtain a certain illumination in one location also in another location. This requires to “copy” the illumination from the one location and to “paste” it into the other location. 
     EP 1 619 934 A1 discloses a color duplication method and an apparatus applying a color sensor that measures a target color. A color matching mechanism controls a color projection mechanism to change the color of the object to match the target color. Thus, the color of an object may be adjusted in that it matches a target color. 
     It is an object of the present invention to provide an improved system and method for performing an illumination copy and paste operation. In order to achieve the object defined above, the invention provides a system for performing an illumination copy and paste operation in a lighting system comprising
         a first light source adapted to provide a first light for illuminating a first location,   a second light source adapted to provide a second light for illuminating a second location,   a light detector comprising   a first sensor configured to receive the first light directly from the first light source and measure first light attributes of the first light and   a second sensor configured to receive the first light influenced by reflections from surfaces and measure second light attributes of the first light,   a memory configured to store a database including a specification of the second light source,   processing means adapted to process perceivable light attributes at the first location from the first light attributes and the second light attributes, and in conjunction with the specification of the second light source to control the second light source to provide the second light having light attributes at the second location that substantially match the perceivable light attributes at the first location, whereby the illumination at the first location may be copied and pasted to the second location.       

     In order to achieve the object defined above, the invention also provides a method for performing an illumination copy and paste operation in a lighting system comprising the steps of
         providing a first light for illuminating a first location,   providing a second light for illuminating a second location,   receiving the first light directly from the first light source and measuring first light attributes of the first light and   receiving the first light influenced by reflections from surfaces and measuring second light attributes of the first light,   storing a database including a specification of the second light source,   processing perceivable light attributes at the first location from the first light attributes and the second light attributes, and in conjunction with the specification of the second light source controlling the second light source to provide the second light having light attributes at the second location that substantially match the perceivable light attributes at the first location.       

     An illumination copy and paste system and a corresponding method are described in the European patent application EP06113411.0 of the applicant filed on May 3, 2006. In this application, the copy and paste operation is based on a light-wave identification of the direct light from light sources without taking into account any reflections influencing the perceivable light conditions at the copy, i.e. the first location. In contrast to his, the characteristic features according to the present invention provide the advantage that reflections are considered when an illumination is copied from the first location and pasted to the second location. This may result in a high accuracy of the illumination copy and paste operation with regard to the perceived light (color). According to the present invention, the reflections of light from surfaces are detected with a second sensor in addition to a first sensor for measuring the light directly coming from a light source. The second sensor is configured such that it only receives the first light influenced by reflections from surfaces, while the first sensor receives light directly from the light source. 
     According to an embodiment of the invention, the processing means may be further adapted
         to calculate the surface color reflection spectrum from the first light attributes and the second light attributes,   to compute an adjustment color spectrum from the calculated surface color reflection spectrum and the first and second light attributes, and   to control the second light source based on the computed adjustment color spectrum.       

     The advantage of the measurement of the first and second light conditions is that it enables the determination of the reflection spectrum at the first or copy location. This further allows to calculate an adjustment color spectrum for the second light source, and the second or paste location. The purpose of this adjustment color spectrum is to adapt the illumination at the second or paste location such that it essentially matches the illumination at the first or copy location. The adjustment color spectrum allows to take the reflections on the copy location into account when the illumination is pasted into the second or paste location. 
     According to a further embodiment of the invention, the processing means may be further adapted
         to calculate the surface color reflection spectrum from the first light attributes and the second light attributes by subtracting the color spectrum measured with the second sensor from the color spectrum measured with the first sensor.       

     Typically, reflecting surface may cause a shift in the color spectrum of the first light measured by the second sensor. The influence of a reflecting surface may be determined by the subtraction of the two color spectrum measured with both sensors. 
     According to a yet further embodiment of the invention, the system may further comprise a light detector comprising
         a first sensor configured to receive the second light directly from the second light source and measure first light attributes of the second light and   a second sensor configured to receive the second light influenced by reflections from surfaces and measure second light attributes of the second light,   wherein the processing means are further adapted to process perceivable light attributes at the second location from the first light attributes and the second light attributes of the second light, and in conjunction with the perceivable light attributes at the second location to adjust the second light source to provide the second light having light attributes at the second location that substantially match the perceivable light attributes at the first location.       

     In order to further improve the illumination copy and paste operation, the illumination at the second or paste location may detected with the light detector. The measurements of the light from the second light source at the second or paste location may then be used to adjust the second light in order to better match the perceivable light attributes at the first or copy location. 
     According to an embodiment of the invention, the adjustment of the second light source comprises iteratively repeating the following steps until the light attributes of the second light at the second location merely differ from the perceivable light attributes at the first location by a predefined minimum deviation:
         measuring the first and second light attributes of the second light with the second light detector at the second location,   transmitting the measured first and second light attributes to the processing means,   processing the received first and second light attributes of the second light and the first and second light attributes of the first light in order to determine a deviation,   if the deviation exceeds the predefined minimum deviation, adjusting the second light source in correspondence with the processed deviation.       

     According to a further embodiment of the invention, a light detector is provided which is adapted for a system according to the invention and which comprises
         a first sensor configured to receive the first light directly from the first light source and measure first light attributes of the first light and   a second sensor configured to receive the first light influenced by reflections from surfaces and measure second light attributes of the first light.       

     According to an embodiment of the invention, the first and second sensor are color sensitive sensors. 
     According to a further embodiment of the invention, the light detector may further comprise
         a decoder for decoding a code contained in the received first light and an internal memory for storing the code, and   a transmitter for transmitting the stored code to the processing means.       

     According to an embodiment of the invention, a lighting controller is provided which may be adapted for usage with a system according to the invention and which comprises
         the processing means, and   receiving means adapted for receiving a copy signal and a paste signal from the light detector.       

     According to a further embodiment of the invention, the lighting controller may be further adapted to communicate with the light detector via a wireless communication link. 
     According to a further embodiment of the invention, a computer program is provided, wherein the computer program may be enabled to carry out the method according to the invention when executed by a computer. The computer program allows to implement the invention for example in a Personal Computer (PC) which may be used for controlling a complex lighting system. 
     According to an embodiment of the invention, a record carrier such as a CD-ROM, DVD, memory card, floppy disk or similar storage medium may be provided for storing a computer program according to the invention. 
     These and other aspects of the invention will be apparent from and elucidated with reference to the embodiment(s) described hereinafter. 
     The invention will be described in more detail hereinafter with reference to exemplary embodiments. However, the invention is not limited to these exemplary embodiments. 
    
    
     
         FIG. 1  shows a lighting system configured for an illumination copy and paste operation of an illumination of a first table into an illumination of a second table by means of a light detector according to an embodiment of the invention; 
         FIG. 2  shows an embodiment of a light detector with two sensors according to the invention, adapted for usage with a lighting system shown in  FIG. 1 ; and 
         FIG. 3  shows the spectrum of lighting sources of a lighting system detected with the detector according to the invention and a computed adjustment of the spectrum for a copy and paste operation according to the invention. 
     
    
    
     In the following description (functional) similar and/or identical elements may be denoted with the same reference numerals. 
     In  FIG. 1 , a lighting system  10  comprises a ceiling  12  with equally spaced light sources, here LEDs, which can be controlled by a (lighting) controller  17  of the lighting system  10 . Only the light intensity is controlled per individual light source compromising a DC output plus modulation, for example CDMA coded signals  18  for identification purposes of the individual light sources at a receiver side D, for example by a light detector  20  placed on the surface  22  of a first table  24 , which is illuminated by first light sources  14  located above the table  24  in the ceiling  12 . 
     The light detector  20  serves to identify the received light from the first light sources  14  by decoding the CDMA coded signals  18  contained in the received light. Thus, the detector  20  comprises a CDMA decoder (not shown) for decoding the CDMA coded signals  18  contained in the light generated from the first light sources  14 . Decoding may be for example activated by pressing a copy button of the light detector  20 . The light detector  20  may internally store the decoded signals  18  for an illumination copy and paste operation. Alternatively, the detector  20  may transmit the decoded signals  18  as an illumination copy signal  27  to receiving means  19  contained in processing means  16  of the controller  17 . After receipt of the illumination copy signal  27 , the processing means  16  may store the decoded signals  18  received with the illumination copy signal  27  together with the driving parameters such as current and duty cycle of the light sources  14  in the database  28  for a latter paste operation. As mentioned above, the light detector  20  is particularly able to recognize which individual first light sources  14  are enabled by the light controller  17 . For the illumination copy operation, the CDMA coded signals  18  of all the first light sources  14  or LEDs incident on the surface  22  are measured by the light detector  20 , particularly together with their operation characteristics such as the duty cycle. 
     The paste operation is shown for the surface  23  of a second table  25 , which is illuminated by second light sources  15  located above the table  25  in the ceiling  12 . The paste operation may be performed with the light detector  20 . When the light detector  20  is located on the surface  22  of the first table, it detects the incident light from the first light sources  14  on the surface  22  by decoding the CDMA coded signals  18  and stores the identification of each individual first light source  14  transmitted with the CDMA coded signals  18 . Thus, the light detector  20  “knows” which of the first light sources  14  were activated by the controller  17  of the lighting system  10  when illuminating the first table  24 . In order to paste the illumination of the first table  24  to the second table  25 , the light detector  20  is located on the surface  23  of the second table  25  and may transmit an illumination paste signal  26  to the controller  17  of the lighting system  10 , for example upon activation of a paste button of the light detector  20 . The illumination paste signal  26  may contain the information about the illumination of the first table  24  which was detected by the light detector  20  when lying on the surface  22  of the first table  24  and stored internally in the light detector  20 . Alternatively, the illumination paste signal  26  may initiate the illumination copy and paste operation by the light controller  16 . 
     Upon receipt of illumination paste signal  26 , the processing means  16  of the light controller  17  load from a database  28  the operation characteristics of the first light sources  14  for creating the detected illumination of the first table  24 . Then, the controller  17  activates and adjusts second light sources  15  for creating an illumination of the second table  25  which substantially matches the illumination of the first table  24 . Particularly, the color of the second light sources  15  or LEDs and their parameters such as the duty cycle are adjusted so that the desired illumination of the first table  24  is obtained for the second table  25 . A detailed description of the copy and paste operation and the different embodiments of this operation can be found in the above mentioned European patent application EP06113411.0 of the applicant. 
     In the above described way, a user of the lighting system  10  can copy and paste the emitted light intensity by the first sources  14  on specific spots as a first order approximation without tuning for reflections effects from the surfaces such as the table surfaces  22  and  23 . However, the reflections of light from these surfaces influence the perceivable light attributes at the locations such as the perceivable colors. For example a colored surface of the table influences the color spectrum of light reflections from this surface since the colored surface reflects only a certain color spectrum and attenuates the remaining parts of the color spectrum. Therefore, a user perceives the entire illumination due to these reflections differently than the direct light from the light source. 
     In the following it is described how the perceived light color, seen by the viewer as affected by the nearby reflecting surfaces, may be copied and pasted according to the invention. Thus, the copy and paste operation as known from the European patent application EP06113411.0 may be improved. For this, in principle, a light detector is applied which can distinguish differences in the reflected colors. This light detector may be color sensitive.  FIG. 2  shows the light detector  20 , adapted to distinguish differences in the reflected colors, in detail. The detector  20  comprises a first sensor  50  “Sensor  1 ” which is capable of measuring (in the copy action) the amount of received light from every individual first light source  14 . A second sensor  52  “Sensor  2 ” measures the light from the first light sources  14 , influenced by the reflection from surface “Surface B”  22 . 
     Thus, the input of two sensors  50  and  52  is available for the copy and paste operation which allows to more distinctively adapt the illumination at the paste location as will be explained below in more detail. The first sensor  50  operates as a straightforward measurement device for light directly coming from the first light sources  14 . The second sensor  52  on the other hand can measure the perceived color changes in the illumination due to the surface “surface B”  22 . Thus, the second sensor  52  allows to detect or measure the influence of the surface  22  on the perceived color of the illumination. This makes it possible to correct the light settings of the second light sources  15  in the paste action according to the paste location. 
     In the copy location “Surface C”  23 , the light detector  20  has two functions. The first function is to measure the unperturbed copy colors coming from the second light sources  15 . However, since the reflection color on the new surface “Surface C”  23  is different, this will enforce the settings of the second light sources  15  illuminating this surface  23  to take into account these color changes so that the resulting observable color is the same on both surfaces  22  and  23 . In other words, the light settings can be corrected by the processing means  16  in order to have a perceived light color correction on the paste location on “surface B”  23  which is closer (from a perception point of view) to the perceived color from the copy location on “Surface A”  22 . Therefore, the second function of the light detector  20  is to initiate the correction of the light settings of the second light sources  15  by the processing means  16  until they create an illumination at the paste location at surface  23  which closely matches the illumination at the copy location on surface  22 . In order to achieve a closely matching illumination at the paste location on surface  23 , the operation of the color matching procedure according to this invention may comprise more number of matching iterations than a simple copy-paste operation which does not take reflective effects into account. 
     The light detector  20  as shown in  FIG. 2  is capable of measuring the amount of light coming from two directions with as minimum as possible light disturbance. Therefore it is equipped with two in the visible-light spectrum sensitive sensors  50  and  52 . In order to make the light disturbance as small as possible, the sensors  50  and  52  are very small and attached to a homogenous visible light transparent supporting device  54  (e.g. Perspex). There is another reason for using very small sensors: small sensors have a low internal capacitance, thus being able to be sensitive for fast changing signals (e.g. CDMA signals), which can be modulated on the emitted light. 
       FIG. 3  shows by means of color spectrum the process of copying and pasting with the light detector  20 . Three light sources  1  to  3  have different spectral patterns  60 ,  62 , and  64  in the optical domain. Sensor  50  (Sensor  1 ) of the light detector  20  detects a combination spectrum  66  of these three light sources  1  to  3 . Both sensors  50  and  52  of the light detector  20  are light sensitive light sensors in order to detect the received light power per CDMA encoded source. The light output from a light source can be adjusted by for example pulse width modulation. It should be noted that enough power is used for the light sources to be able to detect what source is touching what surface. The other sensor  52  (Sensor  2 ) detects the same but reflected spectrum  68  of the light sources  1  to  3 . The light spectrum detected by sensor  52  is influenced by the color and structure of the surface  22  of the first table  24 . From the combination spectrum  66  and the reflection spectrum  68 , a surface color spectrum  72  may be calculated. A smooth color reflection frequency spectrum behavior  70  of the object (in this case the table  24 ) is assumed as shown with the dotted line in the calculated surface color reflection spectrum  72 . Only in the parts of the spectrum in which light sources are active it is possible to determine the color of the surface  22 . 
     For doing the paste-action on the second table  25 , the same amplitude spectrum graphs are created by correspondingly adjusting the light sources illuminating the paste location. If sensors  50  and  52  are used which have a flat frequency response, the signal-levels of the output signals of these sensors are averaged over frequency. Now a “computed adjustment” graph  74  may be calculated from the calculated surface color reflection spectrum  74  in order to closely match the reflection spectrum  68  from the copy location also at the paste location or destination. This computed adjustment graph  74  may then be used to adjust the destination light sources for a perception color copy/paste action. Although there may be imperfections because of the averaging over the spectrum shape per source, this method may be capable of adjusting the light-color on the destination surface relatively close from a human perception point of view to the perceived color on the copy surface. It should be noted that the whole process may be performed without the influence of other light sources which are not part of this complete lighting system like the sun or other light sources. In other words, only “coded” light created by light sources of the lighting system applying for example CDMA may be taken into account. However, also light from the environment may be taken into account, for example by using color sensitive sensors. By taking into account environmental light, it is also possible to compensate other light sources such as the sun or lamps not being part of the lighting system. This may be performed by switching the light sources of the lighting system off and to detect the color spectrum of the environmental light which may then be used for compensation in that the light sources of the lighting system at the paste location are controlled in correspondence with the detected color spectrum of the environmental light and the desired compensation. For example, the lighting system may comprise a kind of “environmental light influence” compensation functionality which may be enabled or disabled by a user in order to compensate the environmental lighting influences at the paste location to the perceivable color. 
     The invention is particularly suitable for applications in the field of the illumination control in a complex lighting system. 
     The invention has the main advantage that makes it more comfortable for a user to adjust an illumination created by a lighting system at a certain location by copying the desired illumination from one location and paste the copied illumination to another location at which the illumination is desired. Furthermore, the invention makes it possible to obtain an illumination at the paste location which more closely matches the illumination at the copy location than with a simply copy and paste operation which does not take into account any reflections. 
     At least some of the functionality of the invention such as the color matching procedure may be performed by hard- or software. In case of an implementation in software, a single or multiple standard microprocessors or microcontrollers may be used to process a single or multiple algorithms implementing the invention. 
     It should be noted that the word “comprise” does not exclude other elements or steps, and that the word “a” or “an” does not exclude a plurality. Furthermore, any reference signs in the claims shall not be construed as limiting the scope of the invention.