Patent Publication Number: US-11657637-B2

Title: Image-based occupancy detector

Description:
RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 16/108,975, filed Aug. 22, 2018, now U.S. Pat. No. 11,195,002, the disclosure of which is hereby incorporated herein by reference in its entirety. 
    
    
     FIELD OF THE DISCLOSURE 
     The present disclosure relates to methods and systems for detecting occupancy using images. In particular, the present disclosure relates to methods and systems for detecting occupancy that increase the efficiency and accuracy of occupancy detection via an image sensor. 
     BACKGROUND 
     Modern lighting fixtures often include additional features above and beyond their ability to provide light. For example, many lighting fixtures now include communications circuitry for sending and receiving commands to and from other devices, control circuitry for setting the light output thereof, and sensor circuitry for measuring one or more environmental parameters. Recently, lighting fixtures have begun to incorporate image sensors. Image sensors in lighting fixtures are generally expected to detect occupancy (i.e., the presence of a person) in the area within the field of view of the image sensor. While there are several well-known methods for determining occupancy using an image sensor, these methods are complex and computationally expensive. As a result, lighting fixtures utilizing an image sensor to detect occupancy must include relatively powerful processing circuitry, which consumes additional power and drives up the cost of the lighting fixture. Accordingly, there is a need for systems and methods for detecting occupancy using an image sensor with reduced complexity and computational expense. 
     SUMMARY 
     In one embodiment, an image sensor includes an active pixel array including a number of pixels and image sensor control circuitry configured to perform a read operation only on a subset of the pixels of the active pixel array such that pixels not in the subset remain inactive. By reading out only the subset of pixels in the active pixel array and keeping the remaining pixels inactive, the temperature of the active pixel array may be reduced compared to a conventional read out process, thereby reducing thermal noise in the resulting pixel data. 
     In one embodiment, a method for detecting occupancy from an image sensor includes obtaining pixel data from the image sensor and analyzing the pixel data to determine if a person has entered the field of view of the image sensor. Notably, the pixel data includes pixel values only for a subset of pixels in an active pixel array of the image sensor. By obtaining and analyzing pixel data only for a subset of pixels, the computational expense of determining if a person has entered the field of view of the image sensor may be significantly reduced. 
     Those skilled in the art will appreciate the scope of the present disclosure and realize additional aspects thereof after reading the following detailed description of the preferred embodiments in association with the accompanying drawing figures. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING FIGURES 
       The accompanying drawing figures incorporated in and forming a part of this specification illustrate several aspects of the disclosure, and together with the description serve to explain the principles of the disclosure. 
         FIG.  1    illustrates an image sensor according to one embodiment of the present disclosure. 
         FIG.  2    illustrates a pixel of an active pixel array according to one embodiment of the present disclosure. 
         FIG.  3    is a flow diagram illustrating a method for detecting occupancy using an image sensor according to one embodiment of the present disclosure. 
         FIG.  4    illustrates a read out pattern for an active pixel array according to one embodiment of the present disclosure. 
         FIG.  5    is a flow diagram illustrating a method for detecting occupancy using an image sensor according to one embodiment of the present disclosure. 
         FIGS.  6 A through  6 C  illustrate read out patterns for an active pixel array according to various embodiments of the present disclosure. 
         FIG.  7    illustrates an intelligent lighting fixture according to one embodiment of the present disclosure. 
         FIG.  8    illustrates an intelligent lighting network according to one embodiment of the present disclosure. 
         FIG.  9    is a perspective view of a troffer-based lighting fixture according to one embodiment of the disclosure. 
         FIG.  10    is a cross-section of the lighting fixture of  FIG.  1   . 
         FIG.  11    is a cross-section of the lighting fixture of  FIG.  1    illustrating how light emanates from the LEDs of the lighting fixture and is reflected out through lenses of the lighting fixture. 
         FIG.  12    illustrates a driver module, an LED array, and an intelligent lighting module (ILM) within the lighting fixture of  FIG.  1   . 
         FIG.  13    is a lighting and network environment according one embodiment. 
         FIG.  14    is a floor plan for an exemplary office environment according to one embodiment. 
         FIGS.  15 A and  15 B  illustrate fields of view for two different lighting environments. 
         FIG.  16    is a flow diagram illustrating operation of a lighting fixture according to one embodiment. 
         FIG.  17    is a flow diagram illustrating occupant detection, classification, tracking, and handoff for a given lighting fixture according to one embodiment. 
         FIGS.  18 A through  18 F  illustrate movement of occupants through an exemplary field of view. 
         FIG.  19 A  illustrates fields of view prior to a mapping operation. 
         FIG.  19 B  illustrates fields of view after a mapping operation. 
         FIG.  20    illustrates a driver module provided in an electronics housing and a communications module in an associated housing coupled to the exterior of the electronics housing. 
         FIG.  21    is a block diagram of an ILM according to one embodiment of the disclosure. 
         FIG.  22    is a top isometric view of an ILM according to a first embodiment of the disclosure. 
         FIG.  23    illustrates an image module installed in a housing of a lighting fixture according to one embodiment of the disclosure. 
         FIG.  24    illustrates an image sensor according to one embodiment of the disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     The embodiments set forth below represent the necessary information to enable those skilled in the art to practice the embodiments and illustrate the best mode of practicing the embodiments. Upon reading the following description in light of the accompanying drawing figures, those skilled in the art will understand the concepts of the disclosure and will recognize applications of these concepts not particularly addressed herein. It should be understood that these concepts and applications fall within the scope of the disclosure and the accompanying claims. 
     It will be understood that, although the terms first, second, etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first element could be termed a second element, and, similarly, a second element could be termed a first element, without departing from the scope of the present disclosure. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. 
     It will be understood that when an element such as a layer, region, or substrate is referred to as being “on” or extending “onto” another element, it can be directly on or extend directly onto the other element or intervening elements may also be present. In contrast, when an element is referred to as being “directly on” or extending “directly onto” another element, there are no intervening elements present. Likewise, it will be understood that when an element such as a layer, region, or substrate is referred to as being “over” or extending “over” another element, it can be directly over or extend directly over the other element or intervening elements may also be present. In contrast, when an element is referred to as being “directly over” or extending “directly over” another element, there are no intervening elements present. It will also be understood that when an element is referred to as being “connected” or “coupled” to another element, it can be directly connected or coupled to the other element or intervening elements may be present. In contrast, when an element is referred to as being “directly connected” or “directly coupled” to another element, there are no intervening elements present. 
     Relative terms such as “below” or “above” or “upper” or “lower” or “horizontal” or “vertical” may be used herein to describe a relationship of one element, layer, or region to another element, layer, or region as illustrated in the Figures. It will be understood that these terms and those discussed above are intended to encompass different orientations of the device in addition to the orientation depicted in the Figures. 
     The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. As used herein, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises,” “comprising,” “includes,” and/or “including” when used herein specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. 
     Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. It will be further understood that terms used herein should be interpreted as having a meaning that is consistent with their meaning in the context of this specification and the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein. 
       FIG.  1    shows an image sensor  10  according to one embodiment of the present disclosure. The image sensor  10  includes an active pixel array  12 , image sensor control circuitry  14 , a pixel selection circuitry  16 , sampling circuitry  18 , analog-to-digital converter circuitry  20 , an output register  22 , and an output  24 . The image sensor control circuitry  14  is coupled to each one of the pixel selection circuitry  16 , the sampling circuitry  18 , the analog-to-digital converter circuitry  20 , and the output register  22 . The pixel selection circuitry  16  is coupled to the active pixel array  12 . The sampling circuitry  18  is coupled between the active pixel array  12  and the analog-to-digital converter circuitry  20 . The analog-to-digital converter circuitry  20  is coupled to the output register  22 , which is in turn coupled to the output  24 . 
     In operation, the image sensor control circuitry  14  provides control signals to each one of the pixel selection circuitry  16 , the sampling circuitry  18 , the analog-to-digital circuitry  20 , and the output register  22  to facilitate capturing an image frame and providing a digitized version thereof at the output  24  of the image sensor  10 . The pixel selection circuitry  16  selects one or more pixels in the active pixel array  12  to be reset and/or read out. In a conventional rolling shutter read process, the pixel selection circuitry  16  serially selects rows of pixels in the active pixel array  12  to be reset and subsequently read out one after the other. Selected pixels provide analog signals proportional to an amount of light detected thereby to the sampling circuitry  18 . The analog-to-digital converter circuitry  20  digitizes the analog signals from the sampling circuitry  18  into pixel data and provides the pixel data to the output register  22 , where it can be retrieved via the output  24 . 
       FIG.  2    shows details of a pixel  26  in the active pixel array  12  according to one embodiment of the present disclosure. The pixel  26  includes a light detecting element  28  and support circuitry  30 . The light detecting element  28  may be a photodiode, photogate, or the like. The support circuitry  30  generally includes one or more switching devices such as transistors that reset and facilitate read out of the pixel  26 . One or more select signals provided to a select signal input  32  (from the pixel selection circuitry  16 ) initiate reset and read out the pixel  26 . During a read operation, analog signals indicative of the amount of light detected by the pixel  26  are provided to a column bus output  34 , which is coupled to the sampling circuitry  18 . 
     For purposes of discussion herein, the pixel  26  generally operates in one of three states: idle, reset, and read out. In an idle state, photons that collide with the light detecting element  28  dislodge electrons that accumulate in a potential well of the light detecting element  28 . The number of electrons that accumulate in the potential well of the light detecting element  28  is proportional to the number of photons that contact the light detecting element  28 . In the idle state, the components of the support circuitry  30  remain off. Accordingly, the pixel  26  consumes minimal if any power and dissipates little if any heat in the idle state. The idle state is also referred to as an inactive state herein. During a reset operation, one or more reset switching components (e.g., transistors) in the support circuitry  30  flush out the electrons accumulated in the potential well of the light detecting element  28 . Some power is consumed by the one or more reset switching components and thus some heat is generated by the pixel  26  during the reset operation. During a read operation, one or more read out switching elements in the support circuitry are turned on to process and transfer the charge stored in the potential well of the light detecting element  28  (e.g., as a voltage or current) to the column bus output  34 . Some power is consumed by the one or more read out switching components and thus some heat is generated by the pixel  26  during the read operation. 
     Conventionally, all of the pixels in the active pixel array  12  are read out to provide a single image frame from the image sensor  10 . Generally, this is done as part of a rolling shutter readout, wherein every pixel in a row of pixels is reset, allowed to remain in an idle state for some amount of time (i.e., the integration time), then read out. This process repeats for each row of pixels until all of the pixels in the active pixel array  12  have been reset and subsequently read out. As the number of rows in an active pixel array  12  increases, the time to capture and read out a single image frame also increases. This may limit the number of image frames that can be captured in a given period of time, known as the frame rate of the image sensor. A limited frame rate may be problematic in some applications. Additionally, the resulting digitized image frame including pixel data for all of the pixels in the active pixel array  12  may be quite large. This may result in increased transfer time of the digitized image frame between the image sensor  10  and external processing circuitry (not shown), as such a transfer is often performed serially. Further, this may result in increased analysis time of the digitized image frame by said external processing circuitry, for example, to detect occupancy in the image frame or a set of image frames. Finally, as discussed above, every reset and read out of a pixel in the active pixel array  12  consumes power and dissipates heat. Over time, continually resetting and reading out every pixel in the active pixel array  12  may raise the temperature of the active pixel array  12 . As the temperature of the active pixel array  12  increases, the signal to noise ratio of each one of the pixels therein decreases due to thermal noise. This may make it difficult to analyze the resulting image frame or set of image frames, for example, to detect occupancy. 
     The inventors of the present disclosure discovered that it is highly inefficient and unnecessary to analyze the entirety of an image frame or set of image frames to detect a transition from an unoccupied state to an occupied state. This is because persons entering the field of view of an image sensor necessarily must first pass through one or more areas within the field of view before being present in other parts of the field of view. For example, for an image sensor in the middle of a room, a person must necessarily pass through an outer edge of the field of view before being present in the center of the field of view. As another example, for an image sensor located in a hallway where the field of view includes the entirety of the area between the two enclosing walls of the hallway, a person must necessarily pass through either the top or the bottom of the field of view before being present in the center of the field of view. As yet another example, for an image sensor with a field of view including the only door to a room and it is known that the room is empty (e.g., due to the absence of occupancy for a given period of time), a person must necessarily pass through the area of the field of view near the door before being present in any other part of the field of view. 
     Accordingly,  FIG.  3    is a flow diagram illustrating a method for detecting occupancy using an image sensor according to one embodiment of the present disclosure. The method starts by obtaining pixel data for a subset of pixels in an active pixel array of an image sensor such that the pixels not in the subset remain inactive (step  300 ). As discussed herein, when a pixel is inactive or idle, the supporting circuitry therein is off and thus the pixel is consuming minimal if any power and producing minimal if any heat. Accordingly, obtaining the pixel data from the subset of pixels in the active pixel array involves reading out only the subset of pixels while allowing the remaining pixels to remain inactive. Next, the pixel data is analyzed to determine if a person has entered the field of view of the image sensor (step  302 ). Details regarding analyzing the pixel data to determine occupancy therefrom can be found in  FIGS.  16 - 19 B  below and U.S. patent application Ser. No. 15/191,753, now U.S. Pat. No. 10,306,738; Ser. No. 15/887,096, now U.S. Pat. No. 11,229,107; and Ser. No. 15/681,941, now U.S. Pat. No. 10,165,650, the contents of which are hereby incorporated by reference in their entirety. It is then determined if a person has entered the field of view (step  304 ). If a person has entered the field of view, additional pixel data may optionally be obtained (step  306 ), where the additional pixel data contains pixel data for a larger portion of pixels in the active pixel array than the subset of pixels. For example, the additional pixel data may contain pixel data for all of the pixels in the active pixel array. Finally, the additional pixel data may be analyzed to determine if an area within the field of view of the image sensor is occupied (step  308 ). Step  308  may be used as a verification of step  302 , or may be used to verify the continuing occupancy of the area within the field of view of the image sensor. Once again, details regarding analyzing the pixel data to determine occupancy therefrom can be found in the above-mentioned patent applications. 
     By obtaining pixel data for only the subset of pixels in the active pixel array such that the pixels not in the subset remain inactive, the temperature of the active pixel array can be kept much lower than if all of the pixels in the active pixel array were read out. This results in significant improvements in the signal to noise ratio of the pixels within the subset due to a reduction in thermal noise. Such improvements may be significantly evident in environments that are hot and dark, since signal to noise ratios in these environments tend to be highly unfavorable. Further, analyzing the pixel data to determine if a person has entered the field of view of the image sensor is far less computationally expensive due to the reduction in the total amount of pixel data to analyze. Optionally obtaining and analyzing the additional pixel data may improve the reliability of detecting occupancy in this manner. 
     By choosing the subset of pixels in the active pixel array wisely, the efficacy of detection of a person entering the field of view of the image sensor can be very high. Notably, the subset of pixels may be chosen such that all of the pixels within the subset reside in a single contiguous area or such that the pixels within the subset are located in separate, discrete areas. In embodiments in which the pixels within the subset reside in a single contiguous area, such a contiguous area may be defined by a polygon containing any number of sides, and at least five sides (i.e., a non-rectangular shape) in some embodiments. 
     In one embodiment, the subset of pixels is chosen such that they reside along an outer border of the active pixel array as illustrated in  FIG.  4   . Specifically,  FIG.  4    illustrates an exemplary readout pattern  36  for an active pixel array in which only the pixels along the outer edges of the active pixel array (illustrated by a group of shaded pixels) are read out, while the remaining pixels along the interior of the active pixel array remain inactive or idle. A person entering the field of view of an image sensor will necessarily first pass through an outer edge of the field of view before arriving in any other portion thereof. Accordingly, by analyzing pixel data from only the pixels in an area along the outer edges of the active pixel array, one can easily detect persons entering the field of view of the camera using only a subset of the pixels therein. 
     In some embodiments, it may be desirable to choose the subset of pixels such that it resides around or near one or more ingress and/or egress points within the field of view of the image sensor. Accordingly,  FIG.  5    is a flow diagram illustrating a method for detecting occupancy using an image sensor according to an additional embodiment of the present disclosure. The method starts by determining a portion of a field of view of an image sensor that is near an ingress and/or egress point (step  500 ). The ingress and/or egress point may be a door, a hallway, or the like. In general, the ingress and/or egress point is one that a person must travel through in order to gain access to the remaining portion of the field of view. Next, a subset of pixels in an active pixel array that detect light in the area near the ingress and/or egress point is determined (step  502 ). This may involve a simple mapping of an area of the field of view to corresponding pixels in the active pixel array that detect light within this area. Next, pixel data is obtained from the subset of pixels in the active pixel array such that the pixels not in the subset remain inactive (step  504 ). As discussed herein, when a pixel is inactive, the supporting circuitry therein is off and thus the pixel is consuming minimal if any power and producing minimal if any heat. Accordingly, obtaining the pixel data from the subset of pixels in the active pixel array involves reading out only the subset of pixels while allowing the remaining pixels to remain inactive. The pixel data is then analyzed to determine if a person has entered the field of view of the image sensor (step  506 ). Once again, details regarding analyzing the pixel data to determine occupancy therefrom can be found in the above-mentioned patent applications. If a person has entered the field of view, additional pixel data may optionally be obtained (step  508 ), where the additional pixel data contains pixel data for a larger portion of pixels in the active pixel array than in the subset of pixels. For example, the additional pixel data may contain pixel data for all of the pixels in the active pixel array. Finally, the additional pixel data may be analyzed to determine if an area within the field of view of the image sensor is occupied (step  510 ). Step  510  may be used as a verification of step  506 , or may be used to verify the continuing occupancy of the area within the field of view of the image sensor. Once again, details regarding analyzing the pixel data to determine occupancy therefrom can be found in the above-mentioned patent applications. 
       FIGS.  6 A and  6 B  illustrate exemplary readout patterns  36  for an active pixel array according to various embodiments of the present disclosure. With respect to  FIG.  6 A , only those pixels in the lower left corner of the active pixel array (illustrated by a group of shaded pixels) are read out, while the remaining pixels are inactive or idle. Such a pattern may be effective, for example, when there is only one ingress and/or egress point to the field of view of the image sensor (e.g., a door leading to a room in which the image sensor is located) and it is in the lower left corner thereof. Notably, the subset of pixels forms a polygon including six sides. As discussed above, the subset of pixels may be chosen to occupy an arbitrary area defined by a polygon having any number of sides. 
     With respect to  FIG.  6 B , only those pixels along a lower left edge, lower bottom edge, and lower right edge of the active pixel array (forming a “U” shape) are read out, while the remaining pixels are inactive or idle. Such a pattern may be effective, for example, when it is known that person must pass through the lower outside edges of the image frame before being present in any other portion of the field of view. 
     With respect to  FIG.  6 C , the subset of pixels includes a first region of interest  38 A in the lower left corner of the active pixel array and a second region of interest  38 B on the right side of the active pixel array. Notably, the first region of interest  38 A and the second region of interest  38 B are not contiguous. While not shown, the first region of interest  38 A and the second region of interest  38 B may also be polygons having any number of sides. Further, while only the first region of interest  38 A and the second region of interest  38 B are shown, the subset of pixels may include any number of separate regions of interest that are either discrete or semi-contiguous without departing from the principles of the present disclosure. The pattern shown in  FIG.  6 C  may be effective, for example, when a person must pass through the lower left side of the field of view or the right side of the field of view before being present in any other portion of the field of view. 
     Conventional image sensors are not able to read out pixels in an active pixel array in an arbitrary pattern. The image sensor  10  discussed herein may include modifications thereto such that the pixel selection circuitry  16  is capable of selecting pixels in an arbitrary fashion in order to read out only a subset of the pixels in the active pixel array  12  such that the subset includes polygons having any number of sides and/or noncontiguous regions of interest. 
     The image sensor  10  may further be configured to read out the pixels in the subset of pixels in a continuous fashion such that there are no pauses for pixels that are not being read out. This may require the image sensor control circuitry  14  to compute and implement specialized timing for the various parts of the image sensor  10  specific to the subset of pixels such that the pixel data can be properly sampled. Accordingly, the image sensor control circuitry  14  may be configured to alter the timing of pixel selection by the pixel selection circuitry  16  in order to provide a proper read out of the subset of pixels. Further, the image sensor control circuitry  14  may be configured to change operating parameters of the sampling circuitry  18  and the analog-to-digital converter circuitry in order to properly digitize the pixel data from the subset of pixels. Continuously reading out the subset of pixels without pausing for those pixels that are not being read out may significantly lower read times and thus allow for increases in frame rate above and beyond that which is achievable by a conventional image sensor. 
     Finally, the image sensor control circuitry  14  may be configured to change operating parameters of the output register  22  such that the pixel data for the subset of pixels is properly arranged and thus communicated to external circuitry for analysis. In particular, the image sensor  10  may be configured to capture, store, and facilitate transfer of the pixel data for the subset of pixels as a sparse data structure that does not include reserved spots (i.e., blank spaces) for pixels that are not in the subset of pixels. This may allow for a much smaller data structure to be provided via the output  24 , improving transmit times when provided to another device. 
     The image sensor  10  discussed herein may be incorporated into an intelligent lighting fixture  40  as shown in  FIG.  7   . The intelligent lighting fixture  40  includes the image sensor  10 , driver circuitry  42 , communications circuitry  44 , and a solid-state light source  46 . The driver circuitry  42  is coupled to the image sensor  10 , the communications circuitry  44 , and the solid-state light source  46 . The driver circuitry  42  may use the communications circuitry  44  to communicate with other devices such as other lighting fixtures within a distributed lighting network. Further, the driver circuitry  42  may control one or more light output parameters (e.g., brightness, color temperature, color rendering index, and the like) of the solid-state light source by providing one or more driver signals thereto. Finally, the driver circuitry  42  may obtain and analyze pixel data from the image sensor  10  according to the methods discussed above with respect to  FIG.  3    and  FIG.  5    to determine and react to occupancy. By using pixel data for only a subset of pixels in the active pixel array  12  of the image sensor  10 , the processing resources of the driver circuitry  42  may be significantly conserved. This may in turn lead to reduced power consumption of the intelligent lighting fixture  40 , reduced cost due to the reduced processing requirements of the driver circuitry  42 , and improved longevity of the driver circuitry  42 . 
     The intelligent lighting fixture  40  may be one of many intelligent lighting fixtures  40  in an intelligent lighting network  48 , as shown in  FIG.  8   . The intelligent lighting fixtures  40  may communicate with one another in order to provide certain functionality such as responding to occupancy events. Each one of the intelligent lighting fixtures  40  may be configured to detect occupancy using the image sensor  10  as discussed above. However, each one of the intelligent lighting fixtures  40  may be configured with a different read out pattern for the active pixel array  12  of the image sensor  10 , such that the subset of pixels used to determine occupancy is different for different ones of the intelligent lighting fixtures  40 . 
     In one embodiment, the intelligent lighting fixtures  40  may be configured to save processing resources by only requiring certain ones of the lighting fixtures  40  to detect occupancy when a space is unoccupied. In particular, those intelligent lighting fixtures  40  where a field of view of the image sensor  10  thereof includes an ingress and/or egress point to a space in which the intelligent lighting fixtures  40  are located may be tasked with detecting occupancy when the space is currently unoccupied, while the remaining intelligent lighting fixtures  40  are not required to do so. Those intelligent lighting fixtures  40  where a field of view of the image sensor  10  thereof does not include an ingress and/or egress point to the space do not need to detect occupancy when the space is currently unoccupied, because a person cannot enter the space without first passing through an ingress and/or egress point thereto. When occupancy is detected by one of the intelligent lighting fixtures  40  tasked with detecting occupancy, the remaining intelligent lighting fixtures  40  may begin to detect occupancy as well in order to verify occupancy or more accurately or precisely determine occupancy. 
     Of those intelligent lighting fixtures  40  that are tasked with detecting occupancy in the intelligent lighting network  48  when the space is currently unoccupied, they may utilize the methods discussed above wherein only a subset of pixels in the active pixel array  12  of the image sensor  10  are used for doing so. The read out patterns for each one of the intelligent lighting fixtures  40  may be configured to accurately detect occupancy with minimal processing overhead as discussed above. The read out patterns may be determined by persons familiar with the space and programmed into the intelligent lighting fixtures  40 , or may be determined by the intelligent lighting fixtures  40  themselves or a device in the intelligent lighting network  48  with access to sensor data from the intelligent lighting fixtures  40 , for example, using learning algorithms. 
     An overview of another exemplary lighting fixture incorporating the concepts described above is provided. While the concepts of the present disclosure may be employed in any type of lighting system, the immediately following description describes these concepts in a troffer-type lighting fixture, such as the intelligent lighting fixture  40  illustrated in  FIGS.  9 - 11   . 
     In general, troffer-type lighting fixtures, such as the intelligent lighting fixture  40 , are designed to mount in, on, or from a ceiling. In most applications, the troffer-type lighting fixtures are mounted into a drop ceiling (not shown) of a commercial, educational, or governmental facility. As illustrated in  FIGS.  9 - 11   , the intelligent lighting fixture  40  includes a square or rectangular outer frame  50 . In the central portion of the intelligent lighting fixture  40  are two rectangular lenses  52 , which are generally transparent, translucent, or opaque. Reflectors  54  extend from the outer frame  50  to the outer edges of the lenses  52 . The lenses  52  effectively extend between the innermost portions of the reflectors  54  to a central mounting member  56 , which may double as a heatsink and functions in this embodiment to join the two inside edges of the lenses  52 . As described in detail further below, an intelligent lighting module (ILM)  58  may be mounted in, on, or to the central mounting member  56  or any other suitable portion of the intelligent lighting fixture  40 . The ILM  58  provides intelligence for the intelligent lighting fixture  40 , houses or is otherwise coupled to one or more sensors SX, and facilitates wired and/or wireless communications with other intelligent lighting fixtures  40  or other remote entities. 
     In essence, the ILM  58  is a control and communications module for the intelligent lighting fixture  40 . The communications with other intelligent lighting fixtures  40  and other entities may relate to sharing state information and sensor information, as well as providing instructions or other information that aids in the control of the intelligent lighting fixtures  40  or other entities during normal operation or commissioning. While three sensors S 1 -S 3  are illustrated, the lighting fixture may have any number of the same or different sensors SX. The sensors SX may include one or more image, occupancy (i.e. passive infrared (PIR) sensor), acoustic, ambient light, temperature, humidity, pressure, vibration, carbon monoxide, carbon dioxide, air quality, smoke, power, or like sensors Further details are provided below. 
     Turning now to  FIGS.  10  and  11    in particular, the back side of the central mounting member  56  provides a mounting structure for a solid-state light source, such as an LED array  60 , which includes one or more rows of individual LEDs mounted on an appropriate substrate. The LEDs are oriented to primarily emit light upwards toward a concave cover  62 . The volume bounded by the cover  62 , the lenses  52 , and the back of the central mounting member  56  provides a mixing chamber  64 . As such, light will emanate upwards from the LEDs of the LED array  60  toward the cover  62  and will be reflected downward through the respective lenses  52 , as illustrated in  FIG.  11   . Notably, not all light rays emitted from the LEDs will reflect directly off of the bottom of the cover  62  and back through a particular lens  52  with a single reflection. Many of the light rays will bounce around within the mixing chamber  64  and effectively mix with other light rays, such that a desirably uniform light is emitted through the respective lenses  52 . 
     Those skilled in the art will recognize that the type of lenses  52 , the type of LEDs, the shape of the cover  62 , and any coating on the bottom side of the cover  62 , among many other variables, will affect the quantity and quality of light emitted by the intelligent lighting fixture  40 . As will be discussed in greater detail below, the LED array  60  may include LEDs of different colors, wherein the light emitted from the various LEDs mixes together to form a white light having a desired characteristic, such as spectral content (color or color temperature), color rendering index (CRI), output level, and the like based on the design parameters for the particular embodiment, environmental conditions, or the like. 
     If the central mounting member  56  functions as a heatsink, fins (not shown) may extend from the central mounting member  56  in any direction. If the fins extend from the bottom of the central mounting member  56 , the fins may be visible from the bottom of the intelligent lighting fixture  40 . Placing the LEDs of the LED array  60  in thermal contact along the upper side of the central mounting member  56  allows any heat generated by the LEDs to be effectively transferred to the bottom side of the central mounting member  56  for dissipation within the room in which the intelligent lighting fixture  40  is mounted. 
     As illustrated in  FIG.  12   , a driver module  66  is coupled to the LED array  60  and the ILM  58  through appropriate cabling  68  and is mounted to a driver mount  70  of the intelligent lighting fixture  40 . The driver module  66  is used to drive the LED array  60  to provide a desired light output level in response to instructions from the ILM  58 . In normal operation, The ILM  58  uses its internal logic to determine an on/off state and an output level for the LED array  60  based on information received directly or indirectly from one or more sensors S 1 -S 3 , other intelligent lighting fixtures  40 , and/or remote entities, such as such as control nodes  74 , processing nodes  76 , system controllers  72 , wall controllers (not shown), and the like. The ILM  58  may also send information bearing on the state of the intelligent lighting fixture  40 , sensor information, control information, requests for information, and the like to one or more of the other intelligent lighting fixtures  40  and/or remote entities. While described as an integrated module, the functionality of the ILM  58  may be incorporated into the driver module  66  or other electronics of the intelligent lighting fixture  40 . 
     The system controller  72  represents any type of remote control entity that is configured to control at least one system other than the lighting network in which the intelligent lighting fixtures  40  reside. For example, the system controller  72  may be a controller for one or more of a heating, ventilation air conditioning (HVAC) system, a security system, a fire protection system, an irrigation system, a manufacturing system, evacuation systems, occupancy monitoring or control systems, and the like. As discussed in detail below, the concepts provided herein allow the lighting network not only to determine whether various spaces are occupied, but also to determine the number of occupants in a space when the space is occupied. With modern HVAC systems that include variable speed refrigerant flows and fan speeds, HVAC control is no longer simply turning on or the HVAC system. The rate or level of heating, cooling, and/or ventilation is variable. With the concepts provided herein, HVAC control may take into consideration not only room temperature, but also the number of occupants in the room, which is referred to herein as an occupancy level. 
     The lighting network is able to report the occupancy level for each space such that the HVAC control can dynamically adjust the level of heating, air conditioning, and/or ventilation for each space based on temperature as well as changing occupancy levels. A space with more people may benefit from higher levels of heating, air conditioning, and/or ventilation, and vice versa. In addition to or in lieu of controlling the heating, air conditioning, and/or ventilation levels based on the occupancy level, other HVAC settings may be dynamically controlled or adjusted based on occupancy levels. For example, the HVAC set points, set backs, and/or dead bands (hysteresis ranges about a set point or set back) may be dynamically changed on a room-by-room basis or globally for an entire environment that includes those rooms. As indicated above, HVAC control based on actual occupancy levels as opposed to general occupancy is on one example of control. 
     The intelligent lighting fixtures  40  may be configured to communicate directly with the system controllers  72  or provide the occupancy information to an intermediate device, such as the processing node  76  or control node  74 , which will process the occupancy information collected from a group of intelligent lighting fixtures  40  and provide appropriate occupancy related instructions or information to the system controllers  72 . The processing nodes  76  are generally part of the lighting network and may be used to facilitate configuring the various intelligent lighting fixtures  40  in the lighting network during commissioning; group control of the intelligent lighting fixtures  40 , if such control is not distributed amongst the intelligent lighting fixtures  40 ; communications with remote entities, and the like. The control nodes  74  are dedicated lighting control devices that are used to configure or control the intelligent lighting fixtures  40  individually or as a group. 
     Turning now to  FIG.  13   , an exemplary lighting network is illustrated. The lighting network includes multiple intelligent lighting fixtures  40 , each of which includes a first sensor S 1 , which is an image sensor  10 , and a second sensor S 2 , which is a PIR-based occupancy sensor. The first and second sensors S 1  and S 2  may take other forms, as those skilled in art will appreciate. The particular combination of an image sensor  10  for the first sensor S 1  and a PIR-based occupancy sensor for the second sensor S 2  is for illustrative purposes only. 
     As illustrated, a first group of the intelligent lighting fixtures  40  are configured to communicate with one another as well as other entities using wireless communications and form part of or are coupled to a lighting network N 1 . A second group of the intelligent lighting fixtures  40  are configured to communicate with one another as well as other entities using wired communications, such as Ethernet-based communications, and also form part of or are coupled to the lighting network N 1 . The lighting network N 1  may be coupled to a traditional local area network (LAN) N 2 , which supports traditional networking within an organization. The LAN N 2  is further coupled to a cloud network N 3 , such as the Internet or like network infrastructure that facilitates communications with remote entities, servers, services, and the like in traditional fashion. Communications with the various system controllers  72 , control nodes  74 , and processing nodes  76  may be supported by any one of the lighting network N 1 , LAN N 2 , and cloud network N 3 , depending on the location and functionality of the devices. Although not illustrated, the lighting network N 1  may include various routers, switches, gateways, standalone sensors, wall controllers for turning on and off as well as dimming all or groups of the intelligent lighting fixtures  40 , and the like. 
       FIG.  14    illustrates an exemplary office environment with numerous intelligent lighting fixtures  40  distributed in the ceiling of the office environment and used for general illumination. In this embodiment, assume that each of the intelligent lighting fixtures  40  includes at least one image sensor-based sensor S 1  and one PIR-based occupancy sensor S 2 . In this configuration, the image sensor-based sensor S 1  is used as a primary occupancy sensor of high resolution, while the PIR-based occupancy sensor S 2  is used as a secondary occupancy sensor of much lower resolution. 
     As illustrated in  FIGS.  15 A and  15 B , the (image sensor based) first sensor S 1  for each intelligent lighting fixture  40  has an associated field of view (FOV). The field of view (FOV) corresponds to an area from which the first sensor S 1  of the intelligent lighting fixture  40  can capture image information. An image is broadly defined herein to include image related information that is captured by the image sensor S 1 . The image related information includes, but is not limited to, information that corresponds to all or part of a still image, all or part of one or more video frames, characteristics (i.e. color, wavelength, brightness, contrast, size, shape, etc.) of any aspect of all or part of a still image or one or more video frames, or any combination thereof. The fields of view (FOVs) for the first sensors S 1  of the respective intelligent lighting fixtures  40  may be fixed or variable depending on the design of the first sensors S 1  and/or the associated intelligent lighting fixtures  40 . In either case, the fields of view (FOVs) may either substantially align with one another, such that there is little or no overlap, as provided in  FIG.  15 A , or substantially overlap with one another, as provided in  FIG.  15 B . Details are provided further below on how these different configurations affect the tracking of occupants throughout a given environment. 
     Turning now to  FIG.  16   , a flow diagram is provided to illustrate both the general operation of each intelligent lighting fixture  40  as well as tracking of occupants within a given environment. Each intelligent lighting fixture  40  will control its light output for general illumination based on information or instructions provided by other entities and/or sensors (step  1600 ). For example, light output may be controlled, such as being turned on, turned off, or dimmed to a desired level, based on information received from one or any combination of an associated wall controller, control node, system controller, processing node, other lighting fixture, and the like. 
     In addition to providing light for general illumination, each intelligent lighting fixture  40  is configured to determine the number of occupants in the associated field of view (step  1602 ) and provide occupancy information, based on the number of occupants in the associated field of view, to a remote entity, such as the system controller, control node, processing node, and the like (step  1604 ). In essence, the occupancy information for a given intelligent lighting fixture  40  generally corresponds to the number of occupants within the lighting fixture&#39;s field of view. Based on the occupancy information for the intelligent lighting fixture  40  in a given area, the number of occupants for the given area may be calculated by summing the number of occupants that are in the fields of view for each of the lighting fixtures in the given area. In certain embodiments, steps are taken to avoid redundantly counting an occupant that resides in multiple fields of view at the same time. Details are provided further below. 
     As indicated above, controlling the light output (step  1600 ), determining the number of occupants in an associated field of view (step  1602 ), and providing occupancy information to a remote entity (step  1604 ), are provided on a fixture-by-fixture basis. Each intelligent lighting fixture  40  uses the associated image sensor  10  to track occupants on a per occupant basis. As such, one or more occupants may be tracked by a given intelligent lighting fixture  40  at any given time. In one embodiment, the intelligent lighting fixture  40  will use its sensors to detect motion caused by a moving object in the associated field of view (step  1606 ) and classify the object as either an occupant or non-occupant (step  1608 ). An occupant is considered as a person (human), while a non-occupant is generally considered an object, or anything other than a person. If an object is classified as an occupant, the occupant is tracked while the occupant remains in the associated field of view (step  1610 ). 
     When the occupant moves or is predicted to move outside of the associated field of view, the intelligent lighting fixture  40  will coordinate with neighboring intelligent lighting fixtures  40  to facilitate a handoff of the occupant tracking to the neighboring intelligent lighting fixture  40  that provides a field of view to which the occupant has moved or is predicted to move (step  1612 ). The detection, classification, tracking, and handoff steps  1606 - 1612  may provide information that is helpful when both controlling the light output (step  1600 ) as well as determining the number of occupants in the field of view of a given intelligent lighting fixture  40  (step  1602 ). In essence, as occupants are detected in or leave the associated field of view, the intelligent lighting fixture  40  will dynamically update and report on the total number of occupants in its associated field accordingly. Again, occupants within the associated field of view of a particular intelligent lighting fixture  40  may be tracked on an individual basis, where the intelligent lighting fixture  40  may track multiple occupants at any given time. 
       FIG.  17    is a flow diagram illustrating how individual occupants are detected and tracked within a given lighting fixture&#39;s field of view using the image sensor  10  and/or a passive infrared (PIR)-based occupancy sensor. The image sensor  10  is used for high-resolution detection, classification and tracking of occupants within a field of view for the associated intelligent lighting fixture  40 . The PIR-based occupancy sensor is used for low-resolution occupancy detection. As such, various other types of sensors, such as acoustic, thermal, image, and the like may be employed for a sensor. It is assumed that control electronics and associated software of the intelligent lighting fixture  40  use information gathered from the image sensor  10  and/or additional sensors, and perhaps neighboring intelligent lighting fixtures  40 , to provide the following functionality. Those skilled in the art will recognize that such functionality may be integrated within or distributed among various hardware and/or software components of one or more intelligent lighting fixtures  40  and associated devices. 
     The process starts when the intelligent lighting fixture  40  analyzes information provided by one or both of the image sensor  10  and the PIR-based occupancy sensor to monitor for motion caused by the movement of an object within the lighting fixture&#39;s field of view or general vicinity (step  1700 ). If motion is not detected (step  1702 ), the intelligent lighting fixture  40  will continue to monitor for motion (step  1700 ). If motion is detected (step  1702 ), the intelligent lighting fixture  40  will analyze information provided by the image sensor  10  in an effort to determine if the object is an occupant who has previously been detected and is currently being tracked (step  1704 ). Motion detection employs the use of one or more sensors. As an example for an image sensor  10 , the intelligent lighting fixture  40  will analyze captured image information to detect motion. For a PIR-based occupancy sensor, the intelligent lighting fixture  40  will receive an output indicative of motion within the sensor&#39;s field of view. The intelligent lighting fixture  40  may process the information from various sensors to detect or otherwise identify motion. 
     If the object is not an occupant who is currently being tracked, the intelligent lighting fixture  40  will analyze the information provided by the image sensor  10  to classify the object as either an occupant or a non-occupant, where an occupant is a person and a non-occupant is an inanimate object (step  1706 ). Those skilled in the art will recognize various schemes to classify an object. Examples include histogram of oriented gradients (HOG) schemes, which use machine learning to classify object appearance and shape. Incorporation of Principal Components Analysis (PCA) into the HOG schemes provide for particularly robust and reproducible classification of occupants and groups of occupants. HOG-based classification is viewed as sufficiently robust, yet not overly computationally burdensome for a lighting application. If even greater accuracy is required, the use of sparse convergent neural networks (SCNN) may be employed; however, the use of SCNN may require more microprocessor memory and/or speed than HOG-based schemes. The SCNN scheme seeks to reduce the complexity of established neural network schemes, thereby reducing response time and computation resources even in visually complex environments. 
     If the object is a non-occupant (step  1708 ), the intelligent lighting fixture  40  will continue to monitor for motion (step  1700 ). If the object is an occupant (step  1708 ), the intelligent lighting fixture  40  will analyze the information provided by the image sensor  10  to track the occupant within the field of view associated with the image sensor  10  (step  1710 ). The function of tracking may range from simply determining that the occupant is within the field of view to determining one or more of a precise location within the field of view, a direction of travel, and a velocity of travel, wherein the direction and velocity of travel may be represented with an appropriate vector that is associated with a direction and magnitude, which corresponds to velocity. 
     The intelligent lighting fixture  40  may also analyze the information received from the image sensor  10  to identify one or more physical characteristics associated with the occupant, such as shape, size, colors, patterns, and the like. These characteristics are helpful for re-identifying an occupant when tracking is lost within the lighting fixture&#39;s field of view, recognizing that the occupant is a single occupant when the occupant resides in an area where the fields of view from adjacent intelligent lighting fixtures  40  overlap, and handing off tracking of an occupant from one intelligent lighting fixture  40  to another when the occupant moves from one lighting fixture&#39;s field of view and to another. 
     The tracking function may employ various tracking schemes, including Kalman filtering, which provides a streamlined and effective technique for persistently tracking objects. 
     When motion is detected and the object detected is a previously tracked occupant (step  1704 ), the intelligent lighting fixture  40  may skip the steps of classifying the object (steps  1706  and  1708 ), since the object is already known as an occupant, and move directly to tracking the occupant (step  1710 ). As indicated above, this situation may occur when an occupant has not left the field of view for the intelligent lighting fixture  40 , but tracking is lost for some reason. As the occupant moves within the field of view, the intelligent lighting fixture  40  will detect motion associated with the occupant moving (step  1702 ), analyze information provided by the image sensor  10 , and recognize that the object is a previously tracked occupant based on the analysis of the information provided by the image sensor  10  (step  1704 ). 
     While tracking an occupant, the intelligent lighting fixture  40  may be configured to detect when tracking is lost for the occupant (step  1712 ) as well as detect or predict that the occupant is leaving the field of view (step  1714 ) for the intelligent lighting fixture  40 . Assuming tracking for the occupant is not lost (step  1712 ) in that the occupant has not left or is not leaving the field of view for the intelligent lighting fixture  40 , tracking will continue (step  1710 ). If tracking for the occupant is lost (step  1712 ), the intelligent lighting fixture  40  may be configured to check information from a second sensor, which in this embodiment is PIR-based occupancy sensor, and determine whether or not occupancy is being detected via the second sensor (step  1716 ). If the information from the second sensor indicates that occupancy is still being detected (step  1718 ), the intelligent lighting fixture  40  will continue trying to track the occupant (step  1710 ). 
     If the information from the second sensor indicates that occupancy is not detected (step  1718 ), the intelligent lighting fixture  40  will communicate with adjacent intelligent lighting fixtures  40  that provide neighboring fields of view to that provided by the intelligent lighting fixture  40  (step  1720 ). The interaction between neighboring lighting fixtures may take many forms. For example, the intelligent lighting fixture  40  may ask its neighbors if any occupants have recently appeared in their fields of view from the field of view of the intelligent lighting fixture  40 . The intelligent lighting fixture  40  may also provide its neighbors with recent information bearing on one or more of recent location, direction, velocity, and physical characteristics of the lost occupant and the neighbors will compare the information provided by the intelligent lighting fixture  40  with any occupants currently being tracked by the neighbors. 
     If a determination is made that the lost occupant is not in the neighbor&#39;s field of view (step  1722 ), the intelligent lighting fixture  40  reverts back to monitoring for motion (step  1700 ). At this point, the intelligent lighting fixture  40  is able to recognize the lost occupant if the occupant is once again detected in the lighting fixture&#39;s field of view. Notably, the intelligent lighting fixture  40  is always monitoring the field of view for new objects that could be occupants when the process repeats. 
     If a determination is made that the lost occupant is in the neighbor&#39;s field of view (step  1722 ), the intelligent lighting fixture  40  will provide any handoff information necessary for handing off tracking of the lost occupant to the neighbor that has picked up the occupant in its field of view (step  1724 ) and then facilitate handoff of the occupant to the neighbor (step  1726 ). The handoff information may include a combination of location, direction, velocity, and physical characteristics of the lost occupant. This list is not inclusive, and those skilled in the art will recognize other pertinent information that may be helpful in various embodiments. Kalman filtering or the like may be used to facilitate handoffs. 
     Returning to step  1714 , another trigger for handing off tracking of an occupant to the neighbor is when the intelligent lighting fixture  40  is actively tracking the occupant (step  1710 ) and predicts, or determines, that the occupant is leaving the lighting fixture&#39;s field of view (step  1714 ). If the intelligent lighting fixture  40  can identify the neighbor toward which the occupant is moving, the intelligent lighting fixture  40  will prepare the handoff information for the occupant (step  1724 ) and communicate with the neighbor to share the handoff information and facilitate the handoff (step  1726 ). If the intelligent lighting fixture  40  cannot identify the neighbor toward which the occupant is moving, the intelligent lighting fixture  40  will prepare the handoff information for the occupant and communicate with other intelligent lighting fixtures  40  in the lighting network N 1  to look for an occupant entering their fields of view. A neighbor receiving the occupant may acknowledge receipt of the occupant and increase its occupancy count to account for the new occupant in its field of view. The intelligent lighting fixture  40  will reduce its occupancy count to account for having an occupant leave its field of view. 
     Step  1728  indicates that a handoff of an occupant from a neighbor may enter the process at the tracking phase (step  1710 ); however, other embodiments may bring in an occupant that is being handed off from a neighbor at any other point in the process. 
       FIGS.  18 A through  18 F  illustrate imagery of a single field of view (FOV) derived from an image sensor  10  at six points in time (t 1 -t 6 ). In this example, two occupants, person P 1  and person P 2 , as well as one non-occupant object N, are present at one time or another in the field of view. Throughout the progression, person P 1  enters the field of view from the left, progresses from left to right through the field of view, and exits the field of view on the right. Using information collected from the image sensor  10 , the intelligent lighting fixture  40  employs a first process to detect and determine that the person P 1  is an occupant for occupancy purposes as well as track person P 1  as she enters, progresses through, and exits the field of view. 
     Using the same information collected from the image sensor  10 , the intelligent lighting fixture  40  employs a second process to detect the movement of the non-occupant object N, once the non-occupant object N begins moving at time t 3  ( FIG.  18 C ). Based on the collected information, the intelligent lighting fixture  40  will be able to determine that the non-occupant object N is not an occupant for occupancy purposes. Using information collected from the image sensor  10 , the intelligent lighting fixture  40  employs a third process to detect and determine that the person P 2  is an occupant for occupancy purposes as well as track person P 2  as he enters and diagonally progresses through the field of view. 
     The intelligent lighting fixture  40  will update its occupancy count accordingly as persons P 1  and P 2  enter and leave the field of view (FOV). The presence or movement of the non-occupant object N will not affect the occupancy count. The intelligent lighting fixture  40  will report the occupancy information periodically or as it changes to a remote entity, such as a system controller, control node, processing node, or the like, which may take appropriate action based on the occupancy information or a change in the occupancy information. 
     When there are overlapping fields of view provided by the various intelligent lighting fixtures  40 , logic trees may be developed to recognize and act on movement of occupants through the borders (periphery) of the various fields of view with neighboring intelligent lighting fixtures  40  being notified of imminent occupant arrival based on their position relative to the reporting intelligent lighting fixture  40 . In one embodiment, handoff logic is developed to effectively handle the case where an occupant resides in an overlapping portion of two fields of view by incorporating probabilistic weighting to define which intelligent lighting fixture  40  “owns,” and thus should account for, the occupant. 
     When determining overall occupancy for a particular space, identifying the intelligent lighting fixtures  40  that are within the space as well as the relative location of the intelligent lighting fixtures  40  in space is very helpful in maintaining accurate occupancy accounts for the space.  FIG.  19 A  illustrates an office environment that has a conference room, two offices, and a cubicle area having four cubicles. Each dashed square represents the field of view of an overhead intelligent lighting fixture  40 . As illustrated, many of the fields of view of the lighting fixtures can overlap with one another. 
     As graphically presented in  FIG.  19 A , the rooms in which the intelligent lighting fixtures  40  are located as well as the relationships, or relative locations, of intelligent lighting fixtures  40  within the office environment are clearly depicted. However, when the intelligent lighting fixtures  40  are installed, neither the intelligent lighting fixtures  40  nor any remote entities that may control or receive information from them are able to discern location or relationship information without automated or manual mapping of some form.  FIG.  19 B  graphically represents the fact that when initially installed, intelligent lighting fixtures  40  are essentially randomly located and oriented. During a commissioning process, a user may employ a remote entity, such as a control node  74 , to access the fields of view for the various intelligent lighting fixtures  40  and map them according to their orientation and location throughout the office environment. The user may also assign the intelligent lighting fixtures  40  to occupancy groups, based on the particular space in which the intelligent lighting fixtures  40  reside. For example, the conference room occupancy group will have six intelligent lighting fixtures  40 , the occupancy group for each of the offices will include two intelligent lighting fixtures  40 , and the occupancy group for the cubicle area will include six intelligent lighting fixtures  40 . 
     Depending on the capabilities of the system, the user may be able to precisely map and orient intelligent lighting fixtures  40 , such that each intelligent lighting fixture  40  may be provided with sufficient information to identify the other intelligent lighting fixtures  40  that are within the particular occupancy group of the intelligent lighting fixture  40 , those neighboring intelligent lighting fixtures  40  that are immediately adjacent the intelligent lighting fixture  40 , the role of the position of the neighboring intelligent lighting fixtures  40  relative to the intelligent lighting fixture  40 , and the like. As such, each intelligent lighting fixture  40  may be provided with information identifying the occupancy group within which it resides, the neighboring intelligent lighting fixtures  40  that are immediately adjacent other intelligent lighting fixtures  40 , and a relative location of the neighboring intelligent lighting fixtures  40 . This information is particularly helpful for the tracking and handoff functions, which were described above. 
     The mapping process may be automated to varying degrees. In a highly automated embodiment, a processing node or the like will collect image information from the various intelligent lighting fixtures  40 , analyze the content and/or characteristics of the image information, and create a map of the intelligent lighting fixtures  40  as described above and graphically represented in  FIG.  19 A . During such a process, the image analysis may identify objects, patterns, colors, light intensities, lighting gradients, and the like in an effort to piece the fields of view into a cohesive map. In this particular example, portions of the perimeter of the fields of view that are likely to include helpful alignment cues, such as walls, bisected objects, and the like, and are highlighted in bold. These portions of the perimeter the fields of view include walls, objects that span fields of view, and the like. 
     The mapping process may be supplemented or replaced by other location determining techniques. For example, a lightcasting technique may be employed, where the various intelligent lighting fixtures  40  take turns providing a pulsed light output while the other intelligent lighting fixtures  40  use appropriate sensors to look for pulsed light. Those intelligent lighting fixtures  40  that are able to detect each other&#39;s pulsed light output are assigned to a particular group. For additional information regarding lightcasting and grouping of lighting fixtures, reference is made to U.S. Pat. Nos. 8,975,827 and 9,706,617, which are incorporated by reference in their entireties. Intelligent lighting fixtures  40  may also employ triangulation or distance determining techniques using radio frequency, acoustic, light, or like signals to provide or aid the mapping process. Reference is made to U.S. patent application Ser. No. 14/928,592, filed Oct. 30, 2015, now U.S. Pat. No. 9,769,900; Ser. No. 15/192,035, filed Jun. 24, 2016, now U.S. Pat. No. 10,251,245; Ser. No. 15/191,753, filed Jun. 24, 2016, now U.S. Pat. No. 10,306,738; and Ser. No. 15/334,853, filed Oct. 26, 2016, now U.S. Pat. No. 9,888,546, which disclose various grouping and mapping techniques and are incorporated herein by reference in their entireties. 
       FIG.  20    provides an exemplary schematic of the driver module  66 , the LED array  60 , and the ILM  58 . In the illustrated embodiment, the LED array  60  may include a mixture of LEDs of different colors. While those skilled in the art will recognize various color combinations, the following example employs red LEDs  78  that emit reddish light at a first wavelength, blue shifted yellow (BSY) LEDs  80  that emit yellowish/greenish light at a second wavelength, and BSY LEDs  82  that emit yellowish/greenish light at a third wavelength, which is different than the second wavelength. The LED array  60  may be divided into multiple strings of series connected LEDs. In essence, LED string LS 1 , which includes a number of red LEDs  78 , forms a first group of LEDs. LED string LS 2 , which includes BSY LEDs  80 , forms a second group of LEDs. LED string LS 3 , which includes BSY LEDs  82 , forms a third group of LEDs. 
     In general, the driver module  66  controls the drive currents i 1 , i 2 , and i 3 , which are used to drive the respective LED strings LS 1 , LS 2 , and LS 3 . The ratio of drive currents i 1 , i 2 , and i 3  that are provided through respective LED strings LS 1 , LS 2 , and LS 3  may be adjusted to effectively control the relative intensities of the reddish light emitted from the red LEDs  78  of LED string LS 1 , the yellowish/greenish light emitted from the BSY LEDs  80  of LED string LS 2 , and the yellowish/greenish light emitted from the BSY LEDs  82  of LED string LS 3 . The resultant light from each LED string LS 1 , LS 2 , and LS 3  mixes to generate an overall light output that has a desired color, correlated color temperature (CCT), and intensity, the latter of which may also be referred to a dimming level. As noted, the overall light output may be white light that falls on or within a desired proximity of the Black Body Locus (BBL) and has a desired CCT. 
     The number of LED strings LSx may vary from one to many, and different combinations of LED colors may be used in the different strings. Each LED string LSx may have LEDs of the same color, variations of the same color, or substantially different colors. In the illustrated embodiment, each LED string LS 1 , LS 2 , and LS 3  is configured such that all of the LEDs  78 ,  80 ,  82  that are in the string are all essentially identical in color. However, the LEDs  78 ,  80 ,  82  in each string may vary substantially in color or may be completely different colors in certain embodiments. In another embodiment, three LED strings LSx with red, green, and blue LEDs may be used, wherein each LED string LSx is dedicated to a single color. In yet another embodiment, at least two LED strings LSx may be used, wherein the same or different colored BSY or blue shifted green (BSG) LEDs are used in one of the LED strings LSx and red LEDs are used in the other of the LED strings LSx. A single string embodiment is also envisioned, where currents may be individually adjusted for the LEDs of the different colors using bypass circuits, or the like. 
     The driver module  66  depicted in  FIG.  20    includes AC-DC conversion circuitry  84 , control circuitry  86 , an ILM communication interface (I/F)  88 , a driver connector  90 , and a number of current sources, such as the illustrated DC-DC converters  92 . The AC-DC conversion circuitry  84  is configured to receive an AC power signal (AC IN), rectify the AC power signal, correct the power factor of the AC power signal, and provide a DC power signal (PWR). The DC power signal may be used to directly or indirectly power the control circuitry  86  and any other circuitry provided in the driver module  66 , including the DC-DC converters  92  and the ILM communication interface (I/F)  88 . The DC power signal may also be provided to the driver connector  90  to power the ILM  58 . Cabling  68  may extend from the driver connector  90  to an ILM connector  94 , which may be mounted to or in the central mounting member  56  ( FIGS.  9 - 12   ) or other portion of the intelligent lighting fixture  40 . In one embodiment, the ILM connector  94  is configured to releasably engage the ILM  58 . When the cabling  68  is connected and the ILM  58  is engaged with the ILM connector  94 , the ILM  58  can receive the DC power signal as well as communicate bidirectionally with the control circuitry  86  of the driver module  66  via the ILM communication interface  88  using proprietary or standard communication protocols. 
     To control the light output of the LED array  60 , the ILM  58  will determine a desired light output level based on one or more of the factors described above and send an instruction to the driver module  66 . The driver module  66  will receive the instruction, determine the desired light output level from the instruction, and drive the LED array  60  in a manner to provide the light output level. The driver module  66  may acknowledge receipt of the instruction and/or provide sufficient feedback to the ILM  58  that the LED array  60  is being driven according to the instruction. From an off state, the ILM  58  may instruct the driver module  66  to turn on and drive the LED array  60  to provide a particular light output level in response to determining that the intelligent lighting fixture  40  should turn on. From an on state, the ILM  58  may instruct the driver module  66  to stop driving the LED array  60  in response to determining that the intelligent lighting fixture  40  should turn off. 
     In response to an instruction by the ILM  58  to output light at a particular light output level, the three respective DC-DC converters  92  of the driver module  66  provide drive currents i 1 , i 2 , and i 3  for the three LED strings LS 1 , LS 2 , and LS 3  in response to control signals CS 1 , CS 2 , and CS 3 . The control signals CS 1 , CS 2 , and CS 3  may be pulse width modulated (PWM) signals that effectively turn the respective DC-DC converters  92  on during a logic high state and off during a logic low state of each period of the PWM signal. As a result, the drive currents i 1 , i 2 , and i 3  for the three LED strings LS 1 , LS 2 , and LS 3  may also be PWM signals. The intensity of light emitted from each of the three LED strings LS 1 , LS 2 , and LS 3  will vary based on the duty cycle of the respective PWM signals. The control circuitry  86  will adjust the duty cycle of the drive currents i 1 , i 2 , and i 3  provided to each of the LED strings LS 1 , LS 2 , and LS 3  to effectively adjust the intensity of the resultant light emitted from the LED strings LS 1 , LS 2 , and LS 3  while maintaining the desired CCT based on instructions from the ILM  58 . 
     In an alternative embodiment, the drive currents i 1 , i 2 , and i 3  for the three LED strings LS 1 , LS 2 , and LS 3  may be variable DC currents instead of PWM signals. In certain instances, a dimming device, such as a wall controller, may control the AC power signal and provide a separate a 0-10 volt DC signal or the like to the driver module  66 . The AC-DC conversion circuitry  84  or other electronics may be configured to detect the relative amount of dimming associated with the AC power signal or 0-10 volt DC signal and provide a corresponding dimming signal (DIMMING SIGNAL) to the control circuitry  86  of the driver module  66 . The control circuitry  86  may pass information based on the dimming signal to the ILM  58  via the ILM communication interface  88 . The ILM  58  can take the dimming information into consideration when providing instructions to the driver module  66 . 
     The control circuitry  86  may include a central processing unit (CPU)  96  and sufficient memory  98  to enable the control circuitry  86  to bidirectionally communicate with the ILM  58  through the ILM communication interface  88  using a defined protocol, such as the Digital Addressable Lighting Interface (DALI) or DALI 2 . The control circuitry  86  may receive data or instructions from the ILM  58  and take appropriate action to process the data and implement the received instructions. The instructions may range from controlling how the LED array  60  is driven to returning operational data of the driver module  66  to the ILM  58 . 
     Notably, when the term “control system” is used in the claims or generically in the specification, the term should be construed broadly to include the hardware and any additional software or firmware that is needed to provide the stated functionality. The term “control system” should not be construed as only software, as electronics are needed to implement control systems described herein. For example, a control system may, but does not necessarily, include the control circuitry  86 , the DC-DC converters  92 , the AC-DC conversion circuitry  84 , and the like. 
     With reference to  FIG.  21   , a block diagram of one embodiment of the ILM  58  is illustrated. The ILM  58  includes control circuitry  100  having an associated CPU  102  and memory  104 , which contains the requisite software instructions and data to facilitate operation as described herein. The control circuitry  100  may be associated with a driver communication interface  106 , which is to be coupled to the driver module  66 , directly or indirectly via the ILM connector  94 . The control circuitry  100  may be associated with a wired communication interface  108 , a wireless communication interface  110 , or both, to facilitate wired or wireless communications with other intelligent lighting fixtures  40 , and/or remote entities, such as wall controllers, mobile terminals, personal computers, and the like. The wireless communication interface  110  may include the requisite transceiver electronics to facilitate wireless communications with remote entities using any number of wireless communication protocols. The wired communication interface  108  may support universal serial bus (USB), Ethernet, or like interfaces using any number of wired communication protocols. 
     In one embodiment, the ILM  58  may receive power in the form of a DC signal from the driver module  66  via the ILM connector  94  and facilitate communications with the driver module  66  via the driver communication interface  106  and the ILM connector  94 . Communications with other intelligent lighting fixtures  40  and/or remote entities, such as wall controllers, mobile terminals, personal computers, and the like, are facilitated via the wired or wireless communication interfaces  108 ,  110 . 
     In an alternative embodiment, the ILM  58  will receive power in the form of a DC power signal via the wired communication interface  108 , which may be configured as a power over Ethernet (PoE) interface. The DC power signal received via the wired communication interface  108  is used to power the electronics of the ILM  58  and is passed to the driver module  66  via the ILM connector  94 . The driver module  66  will use the DC power signal to power the electronics of the driver module  66  and drive the LED array  60 . Communications with other intelligent lighting fixtures  40  and/or remote entities, such as wall controllers, mobile terminals, personal computers, and the like, are facilitated via the wired communication interface  108 . The ILM  58  will facilitate communications with the driver module  66  via the driver communication interface  106  and the ILM connector  94 . 
     As noted, the ILM  58  includes multiple integrated sensors S 1 -SN, which are directly or indirectly coupled to the control circuitry  100 . The sensors S 1 -SN may include one or more image, occupancy, ambient light, acoustic, temperature, humidity, pressure, vibration, carbon monoxide, carbon dioxide, air quality, smoke, power, or like sensors. The sensors S 1 -SN provide sensor data to the control circuitry  100 . Based on internal logic, the ILM  58  will determine how the driver module  66  should drive the LED array  60  based on the sensor data and any other data or instructions received from remote entities, such as other intelligent lighting fixtures  40 , wall controllers, mobile terminals, personal computers, and the like. Based on how the driver module  66  should drive the LED array  60 , the ILM  58  will generate and send appropriate instructions to the driver module  66  via the driver communication interface  106  and the ILM connector  94 . The driver module  66  will drive the LED array  60  based on the instructions received from the ILM  58 . These instructions may result in the driver module  66  turning off the LED array  60 , turning on the LED array  60  to a certain light output level, changing the light output level provided by the LED array  60 , changing the color or CCT of the light output, and the like. 
     In addition to controlling the driver module  66  to control the light output of the LED array  60 , the ILM  58  plays an important role in coordinating intelligence and sharing data among the intelligent lighting fixtures  40  and with other remote entities, such as the system controllers  72 , control nodes  74 , and processing nodes  76 . In addition to receiving data and instructions from other intelligent lighting fixtures  40  or remote control entities and using such information to control the driver module  66 , the ILM  58  may also provide instructions to other intelligent lighting fixtures  40  and remote control entities based on the sensor data from its integrated sensors S 1 -SN as well as the sensor data and instructions received from the other intelligent lighting fixtures  40  and remote control entities. 
     The ILM  58  may have a user interface  112  that provides information related to the state or operation of the ILM  58 , allows a user to manually provide information to the ILM  58 , or a combination thereof. As such, the user interface  112  may include an input mechanism, an output mechanism, or both. The input mechanism may include one or more of buttons, keys, keypads, touchscreens, microphones, or the like. The output mechanism may include one more LEDs, a display, or the like. For the purposes of this application, a button is defined to include a push button switch, all or part of a toggle switch, rotary dial, slider, or any other mechanical input mechanism. 
     An exemplary ILM  58  is illustrated in  FIG.  22   . The ILM  58  has a housing H in or on which sensors S 1 , S 2 , and S 3  and the electronics described above are mounted. In this particular but non-limiting embodiment, sensor S 1  is an image sensor  10 , sensor S 2  is an PIR-based occupancy sensor, and sensor S 3  is an acoustic sensor mounted behind three openings that are provided in the housing H. In this example, the housing H of the ILM  58  is configured to releasably engage a compatible cradle (not shown) or the like provided by the intelligent lighting fixture  40  in a snap-fit manner, such that the sensors S 1 -S 3  are exposed to the lighting environment when the ILM  58  is mounted to the intelligent lighting fixture  40 . 
     With reference to  FIG.  23   , one embodiment of the ILM  58  is illustrated where an image sensor  10  is mounted just inside the housing H of the ILM  58 . A lens  114  or opening is provided in the housing H such that the front surface of the lens  114  is flush with the front surface of the housing H. An active pixel array  12  of the image sensor  10  is aligned with the lens  114  such that the active pixel array  12  is exposed to a field of view through the lens  114 . 
     An exemplary CMOS-based image sensor  10  is shown in  FIG.  24   . While a CMOS-based image sensor  10  is illustrated, those skilled in the art will appreciate that other types of image sensors  10 , such as CCD-based sensors, may be employed. CMOS-based image sensors  10  are particularly useful in lighting applications because they have a broad spectral sensitivity that overlaps that of the human eye. 
     The image sensor  10  generally includes the active pixel array  12 , analog processing circuitry  116 , an analog-to-digital converter (ADC)  118 , digital processing circuitry  120 , and image sensor control circuitry  14 . In operation, the active pixel array  12  will receive an instruction to capture image information from the image sensor control circuitry  14 . In response, the active pixel array  12  will transform the light that is detected at each pixel into an analog signal and pass the analog signals for each pixel of the active pixel array  12  to the analog processing circuitry  116 . The analog processing circuitry  116  will filter and amplify the analog signals to create amplified signals, which are converted to digital signals by the ADC  118 . The digital signals are processed by the digital processing circuitry  120  to create image data. The image data is passed to the control circuitry  100  of the ILM  58  for analysis, storage, or delivery to another intelligent lighting fixture  40  or remote entity. 
     The image sensor control circuitry  14  will cause the active pixel array  12  to capture an image in response to receiving an instruction via a sensor control signal (SCS) from the ILM  58  or other remote entity. The image sensor control circuitry  14  controls the timing of the image processing provided by the analog processing circuitry  116 , ADC  118 , and digital processing circuitry  120 . The image sensor control circuitry  14  also sets the image sensor&#39;s processing parameters, such as the gain and nature of filtering provided by the analog processing circuitry  116  as well as the type of image processing provided by the digital processing circuitry  120 . These processing parameters may be dictated by information provided by the control circuitry  100  of the ILM  58 . For additional information regarding image capture, reference is made to U.S. patent application Ser. No. 14/623,314, filed Feb. 16, 2015, now U.S. Pat. No. 9,686,477, which is incorporated herein by reference in its entirety. 
     Those skilled in the art will recognize improvements and modifications to the preferred embodiments of the present disclosure. All such improvements and modifications are considered within the scope of the concepts disclosed herein and the claims that follow.