Abstract:
A lighting system which includes a light source to emit illuminating light and sense reflected light from an environment. The light source may be included in an array to be selectively enabled and disabled by the controller. The array may include a plurality of light sources, each of which may be sensitive to a wavelength respective to each light source, thus providing the array sensitivity to one or more wavelength. Each of the plurality of light sources in the array may be selectively operable between a sensing operation and an emitting operation. The sensing operation may be defined by the light source sensing the environmental light, and the emitting operation being defined by the light source emitting the illuminating light. The controller may selectively operate the light source between the passive operation and the active operation.

Description:
RELATED APPLICATIONS 
     This application is related to and claims the benefit under 35 U.S.C. §119(e) of U.S. Provisional Patent Application Ser. No. 61/643,634 titled Motion Detection System and Associated Methods filed May 7, 2012, the content of which is incorporated in its entirety herein. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to the field of lighting systems and, more specifically, to lighting systems that can emit and sense light within a wavelength range, and associated methods. 
     BACKGROUND OF THE INVENTION 
     This background information is provided to reveal information believed by the applicant to be of possible relevance to the present invention. No admission is necessarily intended, nor should be construed, that any of the preceding information constitutes prior art against the present invention. 
     Lighting systems have been used to illuminate spaces since the invention of fire. Over the years, technology has brought us the incandescent light, which produces light by heating a metal filament, causing it to radiate heat. Although the incandescent light is capable of illuminating an area, it does so with little efficiency. 
     Lighting systems that include a conversion material may conveniently allow the conversion of a source light emitted from a light source into light of a different wavelength range. Often, such a conversion may be performed by using a luminescent, fluorescent, or phosphorescent material. The wavelength conversion materials may sometimes be included in the bulk of another material, applied to a lens or optic, or otherwise located in line with the light emitted from light source. In some instances the conversion material may be applied to the light source itself. A number of disclosed inventions exist that describe lighting devices that utilize a conversion material applied to an LED to convert light with a source wavelength range into light with a converted wavelength range. 
     Sensors may additionally be included in lighting systems to control operation upon the sensed compliance with a desired event. As an example, sensors may detect the presence of movement in a space to control illumination. However, including sensors may increase the number of parts and complexity required to build the lighting system, thereby increasing its manufacturing cost. 
     There exists a need for a wavelength lighting system that can emit an illuminating light and sense an object within a field of view of the wavelength lighting system by altering its operational state between various portions of the duty cycle. 
     SUMMARY OF THE INVENTION 
     With the foregoing in mind, embodiments of the present invention are related to a wavelength sensing lighting system that can emit illuminating light and sense environmental light during portions of the duty cycle. Additionally, according to an embodiment of the present invention, the lighting system may advantageously analyze the sensed environmental light to determine the presence or absence of an object within the field of view of the wavelength sensing lighting system. 
     The present invention may provide a lighting system which, in one embodiment, may include a light source to emit illuminating light and sense environmental light from an environment and a wavelength conversion material between the light source and the environment to absorb at least part of a source light and emit a converted light. The source light may be received and absorbed by the wavelength conversion material, and the converted light may be emitted by the wavelength conversion material. 
     The light source may be included in an array to be selectively enabled and disabled by the controller. The array may include a plurality of light sources. A plurality of light sources may be included within an array, each of which may be sensitive to a wavelength respective to each light source, thus providing the array sensitivity to one or more wavelength. The plurality of light sources may be selectively operable substantially simultaneously, as well as individually. The plurality of light sources may selectively emit the illuminating light in a plurality of directions and may selectively receive the environmental light from the plurality of directions. 
     Each of the plurality of light sources in the array may be selectively operable between a sensing operation and an emitting operation. The sensing operation may be defined by the light source sensing the environmental light, and the emitting operation being defined by the light source emitting the illuminating light. The controller may selectively operate the light source between the passive operation and the active operation. 
     Some embodiments of the invention may provide a lighting system for detecting movement. The lighting system may include a first set of light emitting diodes (LEDs), a second set of LEDs, a voltage sensor coupled to an LED of the second set of LEDs defining a coupled LED, and a controller functionally coupled to each of the first and second sets of LEDs. The controller may be configured to continuously operate the first set of LEDs to emit light within a field of view of the first and second sets of LEDs. Furthermore, the controller may be configured to operate the second set of LEDs in alternating active and passive states. Additionally, the controller may be configured to operate the second set of LEDs to emit light in the active state. Yet further, the controller may be configured to operate the second set of LEDs to not emit light in the passive state and maintain a baseline voltage. The voltage sensor may be configured to monitor the voltage of the coupled light emitting element during the passive state. Additionally, the coupled light emitting element may be configured to vary the voltage there across upon incidence of light reflected by a target. A change of voltage from the baseline voltage in the coupled light emitting element during the passive state may indicate the detection of a target within the field of view of the first and second sets of LEDs. 
     A method of the present invention may include detecting an object within the field of view of a lighting system comprising a first set of lighting element, a second set of lighting elements, a controller functionally coupled to each of the first and second sets of LEDs, and a voltage sensor coupled to at least one of the second set of LEDs, wherein the light emitting element that the voltage meter is coupled to is configured to vary its voltage, when in a non-emitting state, proportionally to light that is incident thereupon. The method may include operating the first set of LEDs to continuously emit light, operating the second set of LEDs to alternate between an active state and a passive state. And determining a voltage across the coupled light emitting element. The second set of LEDs may be emitting during the active state, and the controller may operate the second set of LEDs to not emit light in the passive state and maintain a baseline voltage. A change of voltage from the baseline voltage in the coupled light emitting element during the passive state may indicate the detection of a target within the field of view of the first and second sets of LEDs. 
     The controller may be operatively connected to a voltage sensor to sense an open circuit voltage across the light emitting diode sensing the environmental light. The controller may analyze information received from the voltage sensor to determine characteristics about the background light. The controller may maintain a running baseline for the background light being received by the LED. Furthermore, the controller may detect a change in the information received from the voltage sensor that may indicate the presence of an object within the field of view of the lighting system. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side view of a lighting system according to an embodiment of the present invention. 
         FIG. 2  is a flow chart of the operation of the lighting system of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which preferred embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Those of ordinary skill in the art realize that the following descriptions of the embodiments of the present invention are illustrative and are not intended to be limiting in any way. Other embodiments of the present invention will readily suggest themselves to such skilled persons having the benefit of this disclosure. Like numbers refer to like elements throughout. 
     Although the following detailed description contains many specifics for the purposes of illustration, anyone of ordinary skill in the art will appreciate that many variations and alterations to the following details are within the scope of the invention. Accordingly, the following embodiments of the invention are set forth without any loss of generality to, and without imposing limitations upon, the claimed invention. 
     In this detailed description of the present invention, a person skilled in the art should note that directional terms, such as “above,” “below,” “upper,” “lower,” and other like terms are used for the convenience of the reader in reference to the drawings. Also, a person skilled in the art should notice this description may contain other terminology to convey position, orientation, and direction without departing from the principles of the present invention. 
     An embodiment of the invention, as shown and described by the various figures and accompanying text, provides a wavelength sensing lighting system substantially as disclosed in U.S. patent application Ser. No. 13/269,222, entitled Wavelength Sensing Light Emitting Semiconductor and Associated Methods, filed Oct. 7, 2011, which is herein incorporated by reference in its entirety. 
     According to one embodiment of the invention illustrated in  FIG. 1 , a lighting system  10  is provided. The lighting system  10  may include an array of light emitting elements, such as light emitting semiconductors. More specifically, the light emitting elements may be light emitting diodes  100  (LEDs). The array of LEDs may be configured according to any shape or configuration desired. In the present embodiment, the array of light emitting elements includes a series of one-foot sections  102 ,  104  of LEDs. The number and arrangement of sections of LEDs may be configured to accommodate the space and desired outcomes of a given implementation. In the present embodiment, the sections  102 ,  104  of LEDs are arranged end-on-end. 
     Each section of LEDs may include any number of LEDs. In the present embodiment, each section of LEDs includes 5 LEDs. Furthermore, each section of LEDs may include two sets of LEDs. A first set of LEDs  106  may be LEDs that are continuously driven by a controller. Continuously driven LEDs are those whose sole function are to provide light and do not sense environmental light. In the present embodiment, the first set of LEDs  106  includes 18 LEDs. 
     A second set of LEDs  108  may be LEDs that have a switched operation. In switched operation, each LED of the second set of LEDs  108  is switched between an active and a passive operating mode. In the active operating mode, each of the LEDs emits light substantially as the LEDs of the first set of LEDs  106 . In the passive operating mode, the LEDs are turned off, which is to say the voltage being applied to them is reduced below an operational threshold, thus de-illuminating the LED. The length of each operating mode and the frequency with which the operating mode is switched may vary. For example, and not by way of limiting, the LEDs of the second set of LEDs  108  may be in the active operating mode for 98% of a duty cycle, in the passive mode for 2% of the duty cycle, and the duty cycle may be repeated at a rate of 25 cycles per seconds. Duty cycles of greater or lesser length, and differing lengths of passive and active operating modes are contemplated and within the scope of the invention. 
     A controller  110  (or microcontroller) may be functionally coupled to each LED of each section of LEDs. Specifically, the controller  110  may be functionally coupled to each of the first and second sets of LEDs. The controller  110  may control the operation of the second set of LEDs, switching the constituent LEDs between active and passive operating modes. More specifically, a plurality of the LEDs in each array may be switched between an on position and an off position under control of the microcontroller. When in the off position, the LED may be electronically connected to an analog to digital converter which is used to sense the voltage across the momentarily inactive LED. This voltage is dependent on the incident light on the LED, and it increases in a non-linear fashion as the magnitude of the incident light increases. 
     Accordingly, the lighting system may further include at least one voltage sensor  112 . Each LED of the second set of LEDs may have a voltage sensor  112  functionally coupled thereto, such that the voltage sensor  112  may detect changes in voltage across the coupled LED. There may optionally be one voltage sensor functionally coupled with all the LEDs of the second set of LEDs, or each LED of the second set of LEDs may have a dedicated voltage sensor coupled thereto. Furthermore, each voltage sensor  112  may be functionally coupled with the controller  110  of each section of LEDs. 
     As data is collected (in real time in some embodiments), the microcontroller maintains a running baseline of the background light being received by the LED. This may be done to be able to compensate for variations in the light received by the sensing LEDs during the course of the observation period. Although movement in front of the sensing LEDs may cause reflections that may affect the light sensed by the sensing LEDs and thus the voltage developed across the LEDs, other factors can also have an effect on the voltage. These factors may, for example, include temperature changes in the environment and light intensity changes due to external factors such as day/night conditions or cloudy/sunny cycles. 
     The instantaneous voltage measured across a sensing LED may be compared to the baseline, and if a predetermined threshold between the voltages is exceeded, a determination may be made that an object or person has moved within the field of view of the LED array. A counter may be increased every time a new movement is detected. To prevent multiple and incorrect counts from objects whose reflections generate a voltage across the sensing LEDs that is close to the threshold voltage, a hysteresis section may be included in the algorithm. For example, a 1% change in voltage across an LED diode (compared to the baseline voltage) could be construed as occurring as a result of movement. The algorithm will continue to consider the reflection to be present until the voltage drops below 0.5% of the baseline voltage. 
     The signal detection algorithm may produce a series of ones and zeros, corresponding to instances when reflections beyond the threshold are detected or not respectively. The length of each sequence of ‘ones’ can be used to measure the duration of the event that resulted in the voltage across the LED exceeding the threshold. Thus, the algorithm can determine if a person walked in front of the LED array without stopping, or is a person stopped for a certain time. 
     The results of the analysis may be displayed in real time, and include a count of the number of events (i.e. the number of people walking in front of the array), and a histogram that can show how long each person stayed in front of the array. For example, in one possible embodiment, the histogram can separate events into four categories:
         1. Less than 1 second   2. Between 1 and 3 seconds   3. Between 3 and 6 seconds   4. More than 6 seconds       

     Turning now to  FIG. 2 , as each LED of the second set of LEDs is switched into the passive operating mode, the voltage sensor may measure the voltage across the LED, as indicated at block  200 . Because external sources of voltage have been removed from the LED, any measured voltage will be a function of background light that is incident upon the LED. More specifically, there is directly proportional relationship between the background light incident upon the LED and the voltage measured by the voltage sensor across the LED. 
     The controller may analyze measurements received from the voltage sensor. As indicated above, one method of analyzing the measurements received from the voltage sensor includes determining a running baseline voltage. The running baseline voltage may indicate a baseline background light that is incident upon the LED. By determining a baseline voltage, the controller may be able to identify when there is a sudden change in the measured voltage, indicating a corresponding change in the background light. Additionally, because the baseline voltage is a running baseline voltage, gradual changes to the background light, such as, for instance, transitions between day and night, or cloud coverage. 
     Each voltage measurement taken during each passive operating mode of an LED may be compared to the running baseline voltage by the controller. When an object moves into the field of view of the lighting fixture, background light will reflect off the object. The reflection of the background light will cause a change in the background light that is incident upon the LED. The change in background light incident upon the LED will cause a corresponding change in the voltage measured across that LED. The controller may analyze the change in voltage to determine whether an object has been detected. 
     Determination of whether an object has entered the field of view of an LED may be based upon a change in the voltage across the LED during a passive operating mode above a certain threshold, as indicated at block  210 . For example, and not by means of limiting, a voltage increase of 0.5% of the running baseline voltage may be interpreted as indicating the presence of an object within the field of view of the LED. If the controller determines there has not been a change exceeding the threshold voltage change, the controller may wait for the next passive operating mode, according to block  220 , before the next voltage measurement may be taken, according to block  200 . 
     The controller may maintain a running count of the number of objects detected within the field of view of the LEDs of each section of LEDs. Each time an object has been detected within the field of view of at least one of the LEDs functionally coupled to the controller, the controller may increase the count, according to block  230 . 
     To prevent multiple and incorrect detections of objects within the field of view that is at or near the threshold voltage, the controller may include a hysteresis function. For example, during a first passive operating mode, a 1.0% increase in voltage may be detected across an LED, where the threshold voltage increase is 0.5%. The controller will increase the count by one, as the measured voltage change exceeds the threshold. The controller may then wait for the next passive operating mode, according to block  240 , before measuring the voltage, according to block  250 . At the next passive operating mode, a 1.0% change in voltage may again be detected. Most likely, this is not an indication of a second object moving into the field of view, but is instead the same object remaining in the field of view. Therefore, the controller should not increase the count, according with block  260 . 
     The controller may determine the length of time an object remains in the field of view of the section of LEDs. As described hereinabove, an object remaining in the field of view of an LED will cause a continuous change in the voltage measured across the LED during its passive operating mode. So long as the change in voltage does not fall below the hysteresis threshold, the controller will determine that the object previously detected remains within the field of view. For each sequential cycle that the controller indicates the presence of the same object, the controller may determine the length of time an object remained within the field of view of the LED, according to block  270 . This determination may be used to characterize the movement of the detected object, i.e. did the object move continuously through the field of view, or did it come to a rest. 
     The controller may wait for the next passive operating mode, according to block  240 , to determine whether the object still remains within the field of view. Accordingly, the hysteresis function will require that the measured voltage must be measured at no more than a hysteresis threshold of a 0.5% change of the baseline voltage must be measured before a second object may be determined to be detected. It is contemplated and included within the scope of the invention that different values for the threshold voltage change and hysteresis threshold voltage change may be employed. 
     If, at block  260 , it is determined that the measured voltage does not exceed the hysteresis voltage, the controller may wait for the next passive operating mode according to block  220 . 
     The controller may be in communication with a computing device external the array. For example, the controller may be in communication with a personal computer or a server. Either the controller or the computing device may categorize the objects detected according to the length of time each object remained within the field of view. For example, in one possible embodiment, the objects may be grouped into those that remained in the field of view for less than one second, between one and three seconds, between three and six second, and more than six second. Furthermore, the results of the analysis may be displayed in real time on the computing device. The results displayed may include, without limitation, the count of objects, and a histogram of the duration of each object. 
     Some of the illustrative aspects of the present invention may be advantageous in solving the problems herein described and other problems not discussed which are discoverable by a skilled artisan. 
     While the above description contains much specificity, these should not be construed as limitations on the scope of any embodiment, but as exemplifications of the presented embodiments thereof. Many other ramifications and variations are possible within the teachings of the various embodiments. While the invention has been described with reference to exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best or only mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims. Also, in the drawings and the description, there have been disclosed exemplary embodiments of the invention and, although specific terms may have been employed, they are unless otherwise stated used in a generic and descriptive sense only and not for purposes of limitation, the scope of the invention therefore not being so limited. Moreover, the use of the terms first, second, etc. do not denote any order or importance, but rather the terms first, second, etc. are used to distinguish one element from another. Furthermore, the use of the terms a, an, etc. do not denote a limitation of quantity, but rather denote the presence of at least one of the referenced item. 
     Thus the scope of the invention should be determined by the appended claims and their legal equivalents, and not by the examples given.