Patent Publication Number: US-2022217829-A1

Title: Electrical field of view control for a passive light sensor

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a Continuation-in-Part of U.S. patent application Ser. No. 16/857,690 entitled “ELECTRICALLY CONTROLLING THE FIELD OF VIEW OF A PASSIVE INFRARED SENSOR,” filed Apr. 24, 2020, the contents of which are incorporated herein in their entirety and for all purposes. 
    
    
     BACKGROUND 
     PIR (Passive Infra-Red) Sensors are ubiquitous and are one of the most fundamental building blocks for motion detection. They are widely used in the field of home/office automation and security, for example. PIR Motion Sensors appear in numerous products such as discrete motion sensing modules for security/intrusion detection, light fixtures, porch light systems, smart lights, and vending machines, among other things. All PIR Motion Sensors have a detection area called a Field of View (FoV), typically expressed as a circular diameter at product level or in angular degrees at raw sensor level. Design engineers typically develop their motion sensing products with a specific target FoV in mind. For example, the FoV of a motion sensor in a porch light is expected to be much larger than the FoV of a discrete indoor motion sensor module. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Aspects of the present disclosure are illustrated by way of example and are not limited by the accompanying figures with like references indicating like elements. In general, the use of a reference numeral should be regarded as referring to the depicted subject matter according to one or more embodiments, whereas discussion of a specific instance of an illustrated element will append a letter designation thereto (e.g., discussion of a pyroelectric sensing element  410 , generally, as opposed to discussion of particular instances of pyroelectric sensing elements  410   a ,  410   b ,  410   c ,  410   d ). 
         FIG. 1A  is a schematic illustrating a side view of an example field of view of a motion sensing device according to one or more embodiments of the present disclosure. 
         FIG. 1B  is a schematic illustrating a top view of an example field of view of a motion sensing device according to one or more embodiments of the present disclosure. 
         FIG. 2A  and  FIG. 2B  are schematics illustrating an example motion sensing device configured with a relatively wide and narrow fields of view, respectively, as viewed from the side, according to one or more embodiments of the present disclosure. 
         FIG. 2C  is a schematic illustrating lens-lets of a domed lens, according to one or more embodiments of the present disclosure. 
         FIG. 2D  is a schematic illustrating lens-lets of a flat lens, according to one or more embodiments of the present disclosure. 
         FIG. 3  is a flow diagram illustrating an example method implemented in a motion sensing device according to one or more embodiments of the present disclosure. 
         FIG. 4  is an isometric drawing of an example motion sensing device according to one or more embodiments of the present disclosure. 
         FIG. 5  is a schematic illustrating an example motion sensing device according to one or more embodiments of the present disclosure. 
         FIG. 6  is a graph illustrating an example of output signaling generated based on a differential voltage, according to one or more embodiments of the present disclosure. 
         FIG. 7  is a schematic illustrating an example of zones within a field of view associated with respective pyroelectric sensing elements of a PIR sensor, according to one or more embodiments of the present disclosure. 
         FIG. 8A  and  FIG. 8B  are schematics illustrating examples of pyroelectric sensing elements receiving infrared radiation via a central lens-let and an off-axis lens-let, respectively, of a substantially flat lens as viewed from the side in cross-section, according to one or more embodiments of the present disclosure. 
         FIG. 9A  and  FIG. 9B  are schematics illustrating examples of pyroelectric sensing elements receiving infrared radiation via a central lens-let and an off-axis lens-let, respectively, of a domed lens as viewed from the side in cross-section, according to one or more embodiments of the present disclosure. 
         FIG. 10A  and  FIG. 10B  are side and bottom views, respectively, of an example ridged lens, according to one or more embodiments of the present disclosure. 
         FIG. 11A ,  FIG. 11B , and  FIG. 11C  are top views of example lenses having respective peripheral shapes, according to embodiments of the present disclosure. 
         FIG. 12A  and  FIG. 12B  are schematics illustrating side views of example lenses that have been colored and which reflect light of particular wavelengths, according to embodiments of the present disclosure. 
         FIG. 13A  and  FIG. 13B  are schematics illustrating top views of lenses that visually blend in with an adjacent surface, according to embodiments of the present disclosure. 
         FIG. 14A  and  FIG. 14B  are schematics illustrating example PIR sensors, according to embodiments of the present disclosure. 
         FIG. 15  is a table illustrating a mapping field of view sizes to sensitivity settings, according to one or more embodiments of the present disclosure. 
         FIG. 16  is a flow diagram illustrating a method of controlling detection sensitivity implemented by a motion sensing device, according to one or more embodiments of the present disclosure. 
         FIG. 17  is a schematic block diagram illustrating electrical components of an example motion sensing device, according to one or more embodiments of the present disclosure. 
         FIG. 18  is a schematic block diagram of an example motion sensing device that includes an analog passive infrared sensor, according to one or more embodiments of the present disclosure. 
         FIG. 19  is a circuit diagram of an embodiment of a motion sensing device in which sensitivity control may be provided by additional components included in a digital potentiometer in communication with a conditioning circuit, according to one or more embodiments of the present disclosure. 
         FIG. 20  is a circuit diagram of an embodiment of a motion sensing device in which sensitivity control may be provided by additional components included in a conditioning circuit, according to one or more embodiments of the present disclosure. 
         FIG. 21  is a circuit diagram of an embodiment of a motion sensing device in which a converter may be configured to set a threshold for the comparator based on a signal received from a controller, according to one or more embodiments of the present disclosure. 
         FIG. 22  is a circuit diagram of an embodiment of a motion sensing device in which a fixed voltage chip is fixed to a reference voltage generator that may set a threshold for a comparator, according to one or more embodiments of the present disclosure. 
         FIG. 23  is a flow chart illustrating an example method of controlling a field of view of a motion sensing device, according to one or more embodiments of the present disclosure. 
         FIG. 24  is a flow chart illustrating an example method of manufacturing a motion sensing device, according to one or more embodiments of the present 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. 
     To design a motion sensing system having an FoV targeted for a specific application, an appropriate lens may be selected. However, once such a system is developed, it is difficult for that FoV to be changed. To enable provide motion sensing solutions for a wide variety of applications, engineers traditionally have developed a separate product stock-keeping unit (SKU) having a different optical and mechanical design that caters to each distinct application. In other cases, engineers apply aftermarket mechanical components to reduce the effective FoV of the motion sensing system, such as a blinder or tape. Embodiments of the present disclosure recognize that dynamic FoV control would be advantageous, particularly if such can be provided by a device without having to change aspects of the optical and mechanical design. 
     Particular embodiment of the present disclosure enable dynamic FoV control by electrically controlling the sensitivity of PIR motion sensors, e.g., without the need of expensive optical or mechanical changes. Such embodiments are generally compatible with a wide variety of PIR sensors. In some embodiments, digital PIR sensors can generally be controlled in the manner that will be described herein such that the FoV may be electrically adjusted. For the motion sensing applications, pyroelectric PIR sensors are the prominent type and digital topology has gained more popularity in recent past. In some embodiments, an analog PIR sensor can generally be controlled in a manner described herein such that the FoV may be electrically adjusted. 
     A Field of View (i.e., FoV) is a space within which a device or sensor is responsive to electromagnetic radiation. The particular spectrum of electromagnetic radiation to which a particular device or sensor responds may depend on its design. Although many of the examples below will focus on PIR sensors that respond to electromagnetic radiation in the infrared spectrum, it should be understood that other embodiments additionally or alternatively include sensors that respond to electromagnetic radiation in other parts of the electromagnetic spectrum (e.g., the visible light spectrum, the ultraviolet spectrum). 
       FIG. 1A  illustrates a side view of an FoV  150  of an example motion sensing device  100 . In this example, the FoV  150  widens in a cone as it extends away from the motion sensing device  100 , such that a diameter  125  of the FoV  150  increases at increasing distances. In this example, the motion sensing device  100  is oriented to cast its FoV  150  toward an opposing target surface  120 . The distance  135  between the motion sensing device  100  and the target surface  120  may be referred to as a mounting distance of the motion sensing device  100 . According to other embodiments the motion sensing device may be mounted to cast a FoV that extends indefinitely. For example, the motion sensing device may be mounted on an outdoor wall facing an open area. 
     The motion sensing device  100  is mounted to an adjacent surface  130 . In this example, the adjacent surface  130  is the ceiling of a room. As will be discussed in further detail below, in other embodiments, the adjacent surface  130  may be that of a light fixture or other device (not shown in  FIG. 1A ). 
     The distance  135  of the motion sensing device  100  from its corresponding target surface  120  (i.e., in this example, the floor) may be described as its mounting height. That said, in other examples, the motion sensing device  100  may be mounted at other angles (e.g., laterally) and oriented to cast its FoV  150  over other surfaces (e.g., an opposing wall). 
     The size of a device&#39;s FoV  150  is traditionally discussed in one of two ways; i.e., as having an angular FoV of some number of degrees θ, or as having a linear FoV of some diameter  125  at a given distance  135 .  FIG. 1A  shows the angle θ and diameter  125  of a FoV  150  at a given mounting distance from a target surface  120 . 
       FIG. 1B  illustrates a top view of the FoV  150  relative where the motion sensing device  100  is positioned. As viewed from the top, the peripheral end  160  of the FoV  150  surrounding an area of the target surface  120  covered by the FoV  150  can be seen. This area is referred to herein as the coverage area of the FoV  150  over the target surface  120 . Presuming a target surface  120  that is normal to the central axis of the FoV  150 , if the angular FoV is known, then the linear FoV (i.e., diameter  125 ) corresponding to the coverage area at a given mounting distance can be determined by Equation 1 below: 
       linear FoV=2×mounting distance×tan(Angular FoV/2)  (Eq. 1)
 
     Correspondingly, if the mounting distance and diameter  125  of the coverage area are known, the angular FoV  150  can be determined by Equation 2 below: 
       Angular FoV=2×tan −1 ((coverage diameter/2)/mounting distance)  (Eq. 2)
 
     As shown in  FIG. 2A  and  FIG. 2B , the motion sensing device  100  may comprise a PIR sensor  200  that may be electrically controlled to widen or narrow the FoV.  FIG. 2A  illustrates the motion sensing device  100  configured with a relatively high sensitivity such that the FoV  150  is relatively wide.  FIG. 2B  illustrates the motion sensing device  100  configured with a relatively low sensitivity such that the FoV  150  is relatively narrow. As will be explained in greater detail below, changing the FoV  150  may not only cause a coverage area to expand or contract, but may also cause more or less of a lens  210  of the motion sensing device  100  to be included in the FoV  150  about a primary sensing axis of the motion sensing device  100 . As shown in  FIG. 2A  and  FIG. 2B , the example motion sensing device  100  comprises a lens  210  and a sensor housing  230 . The lens  210  is retained by the sensor housing  230  and disposed over the PIR sensor  200 . The lens  210  comprises a plurality of lens-lets  220 , each of which is configured to direct light toward pyroelectric sensing elements (not shown in  FIG. 2A  and  FIG. 2B ) within the PIR sensor  200 . When the FoV  150  is relatively wide, as in  FIG. 2A , the FoV  150  around the primary sensing axis  450  is expanded. Correspondingly, more of the lens-lets  220  are included within the FoV  150 . When the FoV  150  is relatively narrow, as in  FIG. 2B , the FoV  150  around the primary sensing axis  450  is reduced. Correspondingly, fewer of the lens-lets  220  are included within the FoV  150 . 
     Different lens  210  designs in accordance with various embodiments may comprise different shapes. In some embodiments, the lens  210  is domed and has a round outer periphery  48 , e.g., as shown in  FIG. 2C . In other embodiments, the lens  210  is substantially flat, as shown in  FIG. 2D . Moreover, particular lens designs may be shaped to wide or narrow the FoV  150  of the motion sensing device  100 . For example, the lens  210  may be configured such that the motion sensing device  100  has a default FoV and/or so that adjustment through a wide range of possible FoVs are supported by electrical control over detection sensitivity of the PIR sensor  200 . Additionally or alternatively, the motion sensing device  100  may include mechanical blinders  92  (e.g., fixed opaque surfaces, stickers, wider or narrower apertures) on, over, and/or under the lens  210  to block light from reaching the PIR sensor  200 . In particular, a mechanical blinder  92  may be disposed to render one or more selected lens-lets  220  inoperative to direct light toward the PIR sensor  200 , e.g., such that the FoV  150  is partially blinded within a portion of the coverage area, as shown in the example of  FIG. 2D . Further examples of lenses  210  in accordance with embodiments of the present disclosure will be discussed in further detail below. 
     Many of the embodiments disclosed herein enable dynamic FoV control by software and/or firmware control over the detection sensitivity of the PIR sensor  200 , e.g., such that a common electrical, optical, and mechanical design may be used to detect motion within an appropriately sized coverage area up to some maximum FoV and/or down to some minimum FoV as may be permitted or possible in view of the motion sensing device&#39;s overall design. Such a motion sensing device  100  may be suitable for deployment to a wide variety of locations and/or support a wide variety of motion sensing applications. Such a motion sensing device  100  may additionally or alternatively simplify inventory management, customer experience, and/or technical support operations as businesses will only need to support a single motion sensing device  100  rather than numerous custom built devices of varying capabilities that may, e.g., be difficult to keep track of and support. 
     Particular embodiments of the present disclosure, for example, include a method  300  implemented in a motion sensing device  100 . The method  300  comprises adapting a field of view  150  around a primary sensing axis  450  of the motion sensing device  100  by electrically controlling a detection sensitivity of a passive infrared sensor  200  of the motion sensing device  100  (block  310 ). The method further comprises, responsive to adapting the field of view  150 , monitoring for motion within the field of view  150  using the passive infrared sensor  200  (block  320 ). 
     One particular example of a motion sensing device  100  that may be suitably adapted to implement embodiments of the present disclosure (e.g., the method  300 ) may be a Cree Lighting® SmartCast® Wireless Integration Module (WIM) as shown in  FIG. 4 . The example WIM  350  shown in  FIG. 4  is a modular system intended to be mounted into an existing light fixture or be mounted directly into the ceiling and leverage Cree Lighting® SmartCast® technology to automate setup. Embodiments of the present disclosure include a WIM  350  that offers dynamic software control over the FoV  150  of a PIR sensor  200 , thereby supporting a variety of FoV  150  configurations using a common electrical, mechanical and optical design. 
     As shown, this particular WIM  350  includes an ambient light sensor (not shown) configured to detect an amount of ambient light and a PIR sensor  200  (not shown in  FIG. 4 ) configured to detect infrared radiation. The WIM further comprises a light pipe  370  disposed over the ambient light sensor, and a lens  210  disposed over the PIR sensor  200 . In this example, the top surface of the light pipe  370  is substantially flat, whereas the lens  210  over the PIR sensor  200  is domed. 
     The WIM  350  also comprises a sensor housing  230  that retains the lenses  210   a ,  210   b  over their respective sensors. Tabs  360   a  in the sensor housing  230  permit the WIM  350  to be retained, e.g., by a standard junction box or retention bracket for mounting the WIM  350  in a wall or ceiling. Tabs  360   b  in the sensor housing  230  permit a faceplate (not shown) to be retained over the sensor housing  230 . The WIM  350  also includes a reset button  320  configured to reset a configuration of the WIM  350 , and interface circuitry  730  configured to exchange signals with a remote device. 
     In this particular example, the interface circuitry  730  of the WIM  350  is a Digital Addressable Lighting Interface (DALI) interface configured to be communicatively connected to a two-wire serial bus (not shown). The DALI interface is configured to draw power from the serial bus and to exchange signals bidirectionally with a remote device over the serial bus. The DALI interface is addressable by a configurable address, and signaling may be effectuated, e.g., using Manchester coding (i.e., encoding zeros and ones on the bus by dropping and raising voltage on the bus, respectively). The line may additionally or alternatively be set to idle by keeping voltage steady (e.g., for the full duration of a given clock cycle, without change). 
     Although the example motion sensing device  100  of  FIG. 4  includes interface circuitry  730  that is connected to a wired bus, as will be explained further below, the interface circuitry  730  may additionally or alternatively comprise wireless communication circuitry (e.g., radio circuitry compatible with one or more wireless communication standards, including but not limited to, Wi-Fi, Bluetooth®, Near Field Communication (NFC), and/or other wireless technologies). The motion sensing device  100  may also be powered by any appropriate power source (e.g., battery, main power). 
       FIG. 5  schematically illustrates an example motion sensing device  100 , as well as how light  430  (e.g., or portions thereof, such as Infra-Red (IR) light  440 ) may generally interact with particular components thereof. The motion sensing device  100  of  FIG. 5  comprises a lens  210 , a filter  420 , and a PIR sensor  200 . The PIR sensor  200  comprises a plurality of pyroelectric sensing elements  410   a - d . In this example, the PIR sensor  200  comprises two pairs of pyroelectric sensing elements  410   a - b ,  410   c - d  arranged in a two-by-two grid (hereinafter referred to as a quad arrangement). According to other particular embodiments, the PIR sensor  200  comprises a single pair of pyroelectric sensing elements  410   a - b  arranged side-by-side (hereinafter referred to as a dual arrangement). Yet other embodiments may include any number of pyroelectric sensing elements  410 , but most commonly includes an even number of pyroelectric sensing elements  410  configured in pairs. 
     Light  430  from within the FoV  150  is received by the motion sensing device  100  at the lens  210 , which passes the IR light  440  through the filter  420  and on to the PIR sensor  200 . The PIR sensor  200  receives the filtered light  430  at one or more of the pyroelectric sensing elements  410   a - d . In this regard, the filter  420  may filter the light  430  such that only the IR light  440  (and/or other wavelengths of the light  430 ) are passed to the PIR sensor. For example, the filter  420  may reduce or eliminate wavelengths outside of the particular IR spectrum that is detectable by the pyroelectric sensing elements  410   a - d . Although the filter  420  is illustrated in this example as being disposed between the lens  210  and the PIR sensor  200 , other embodiments may position the filter over the lens  210 , within the PIR sensor  200 , or lack a filter  420  entirely. More detail regarding how the motion sensing device  100  transfers IR light  440  to the pyroelectric sensing elements  410  of the PIR sensor  200  will be discussed in further detail below. 
     The lens  210  may take a variety of forms and come in a variety of complexities, according to various embodiments of the present disclosure. Among other things, the lens  210  may be substantially flat, domed, and/or ridged, in whole or in part. Many embodiments of the lens  210  comprise a plurality of lens-lets  220 , each of which is shaped to direct infrared radiation toward the pyroelectric sensing elements  410  of the PIR sensor  200 . 
     The pyroelectric sensing elements  410  of the PIR sensor  200  work based on pyroelectricity. Pyroelectricity is ability of certain crystals to generate a temporary voltage when they are heated or cooled. Heat sources (e.g., warm-blooded animals) generate Infrared (IR) radiation. When the pyroelectric sensing elements  410  inside the PIR sensor  200  are exposed to IR radiation (such as the IR radiation produced by a human body), they generate voltage that are a basis upon which the PIR sensor  200  functions. As discussed above, most embodiments of the PIR sensor  200  are expected to have pyroelectric sensing elements  410  configured in a dual or quad arrangement. According to most embodiments, the internal circuitry of the PIR sensor  200  is configured to use the pyroelectric sensing elements  410  in pairs. The motion sensing device  100  produces a differential voltage between a pair of pyroelectric sensing elements  410   a - b ,  410   c - d , and based on this differential voltage, output is or is not generated. 
     For example, in response to the differential voltage between a pair of pyroelectric sensing elements  410   a - b ,  410   c - d  being within (i.e., not in excess of) a threshold, the motion sensing device  100  may refrain from generating output. Correspondingly, in response to the differential voltage between the pair of pyroelectric sensing elements  410   a - b ,  410   c - d  being in excess of a threshold (e.g., the same or a different threshold), the motion sensing device  100  may generate output indicating that motion has been detected. 
     For purposes of this disclosure, the threshold with respect to a differential voltage defines a maximum voltage magnitude (i.e., regardless of whether positive or negative) or a range of voltage values comprising maximum and minimum values that the differential voltage is either within (i.e., under the maximum voltage magnitude regardless of sign or between the maximum and minimum values) or exceeds (i.e., over the maximum voltage magnitude regardless of sign or outside of the maximum and minimum values). By electrically controlling (e.g., configuring) the threshold amount of differential voltage that controls whether or not the PIR sensor  200  generates or does not generate output, embodiments of the present disclosure electrically control the detection sensitivity of the PIR sensor  200 , which may further be used to dynamically control the FoV  150  around a primary sensing axis of the motion sensing device  100 , as will be shown in greater detail below. 
       FIG. 6  illustrates an example of controlling an output signal (Vo) based on whether or not a differential voltage (Vi (ΔV)) is in excess of a voltage threshold. As discussed above, the differential voltage may be produced by a PIR sensor  200  of a motion sensing device  100  in response to the infrared radiation received from a heat source moving within an FoV  150  of a motion sensing device  100 . According to particular embodiments, the PIR sensor  200  may output the differential voltage to other circuitry comprised in the motion sensing device  100 , which uses the differential voltage to generate the output signal shown in  FIG. 6  (e.g., for transmission to a remote device). Alternatively, the PIR sensor  200  may generate the differential voltage, and based thereon, generate the output signal of  FIG. 6 , which other circuitry within the motion sensing device  100  may use to control an output signal of the motion sensing device. In either case, the output signal of the motion sensing device  100  is controlled based on whether or not a pair of pyroelectric sensing elements  410  in the PIR sensor  200  generates the differential voltage in excess of the voltage threshold. 
     In this example, one of the pyroelectric sensing elements  410   a  in the pair is configured to generate a first voltage (e.g., a positive voltage) responsive to the presence of a heat source within one or more zones within the FoV  150  of the motion sensing device  100 . The other pyroelectric sensing element  410   b  in the pair is configured to generate a second voltage (e.g., a negative voltage) responsive to the presence of a heat source within one or more other zones within the FoV  150  of the motion sensing device  100 . For purposes of concisely referring to these zones, a zone associated with a pyroelectric sensing element  410  that produces a positive voltage or a negative voltage in response to detecting infrared radiation will hereinafter be referred to as a positive or negative zone, respectively. 
     The motion sensing device  100  generates a differential voltage by combining the voltages produced by the pair of pyroelectric sensing elements  410   a - b . For example, when both pyroelectric sensing elements  410   a - b  detect the same amount of ambient infrared radiation in the FoV  150 , they may each produce voltage having the same magnitude and opposite directionality, such that the difference between the voltages is zero. In this way, the effect of ambient infrared radiation in the FoV  150  may be effectively ignored. Thus, the differential voltage may be a mechanism that reflects the extent to which infrared radiation is disproportionately affecting the pyroelectric sensing elements  410   a - b  in the pair. As will be discussed further below, this disproportionate effect may be due to the infrared radiation being unevenly distributed within the FoV  150  (e.g., concentrated within a particular zone of the FoV  150 ). 
     In  FIG. 6 , the differential voltage produced by the pair of pyroelectric sensing elements  410   a - b  is shown over time. As shown, the infrared radiation detected by the pyroelectric sensing elements  410   a - b  causes the differential voltage to fluctuate from time T 0  to time T 1 . Because these fluctuations of differential voltage occur within the threshold (shown in  FIG. 6  as a range between positive and negative threshold values), no indication that something has been detected is output. 
     There are numerous potential causes for minor fluctuations in the differential voltage. For example, small amounts of infrared radiation emitted by a heat source outside of the FoV  150  may be reflecting off of particular surfaces within the FoV  150  that are more directly observable by one of the paired pyroelectric sensing elements  410   a  as compared to the other  410   b . Alternatively, the fluctuations may be caused by a relatively small heat source moving into the FoV  150  (e.g., a small cat) that the motion sensing device  100  has been calibrated or designed to ignore. Another cause for the fluctuations may be due to an uneven circulation of warm air within the room. Whatever the cause, the detection sensitivity prevents these minor fluctuations from triggering an output signal. In this regard, a properly calibrated detection sensitivity may prevent the generation of output signals that indicate the detection of motion in response to events that are not of concern to the user. 
     At time T 1 , a heat source enters a positive zone. In response, the pair of pyroelectric sensing elements  410   a - b  produces a differential voltage in excess of the threshold. In particular, the differential voltage is above the maximum voltage value of the threshold. Accordingly, an output signal is generated indicating that infrared radiation has been detected (in this example, by setting an output line carrying Vo high for a fixed duration). The motion sensing device  100  may send Vo (or another signal based thereon, such as a command signal) to a remote device, e.g., to notify the remote device that the motion has been detected, to trigger an alarm, to command a light fixture to flash, and/or produce other output signaling. 
     At time T 2 , the heat source leaves the positive zone. At time T 3 , the heat source moves into the negative zone. In response, the pair of pyroelectric sensing elements  410   a - b  produces a differential voltage that in excess of the threshold (i.e., a differential voltage below the negative threshold value). Accordingly, the output signal indicating that infrared radiation has been detected is again generated. As before, the motion sensing device  100  may send Vo to a remote device, or may generate and send another output signal based thereon in response to the PIR sensor  200  generating the Vo of  FIG. 6 , depending on the embodiment. 
     Of note, in this example, between the times T 2  and T 3  in which the heat source was in transit from the positive zone to the negative zone, the infrared radiation detected by the pyroelectric sensing elements  410   a - b  is shown to be relatively even, such that the differential voltage between the pyroelectric sensing elements  410   a - b  is within the threshold (e.g., as shown in  FIG. 6 ). Correspondingly, the output signal indicating the detection of infrared radiation is not generated during that period. 
     It may be further noted that, although the output signal is provided in response to the differential voltage being in excess of the threshold, in some embodiments, the output signal is produced for a limited (e.g., fixed) duration despite the differential voltage continuing to be in excess of the threshold for a longer period (e.g., from time T 1  to time T 2 ). Thus, in some embodiments, once the output signal has been generated, the PIR sensor  200  (or motion sensing device  100 ) may refrain from generating the output signal again until the differential voltage recovers from hysteresis to a value not in excess of the threshold. For example, consistent with  FIG. 6 , the PIR sensor  200  may generate the output signal for the first time at time T 1  (when the heat source enters the positive zone), and refrain from generating the output signal again until the differential voltage returns to values within the threshold at time T 2  and subsequently exceeds the threshold again at time T 3 . That said, other embodiments may continue to generate the output signal for as long as the differential voltage is in excess of the threshold (e.g., by generating a continuous output signal or repetitively generating the output signal). 
     An example of different zones  600 ,  610  within the FoV  150  that correspond to different ones of the pyroelectric sensing elements  410  of a PIR sensor  200  is illustrated in  FIG. 7 . The closer a heat source is to a given zone  600 ,  610 , the more the corresponding pyroelectric sensing element  410  of the PIR sensor  200  will receive infrared radiation from the heat source and produce voltage in response. Some of the zones  600 ,  610  are “positive zones”  600   a ,  600   b , which is the term herein used to refer to zones  600 ,  610  that are associated with a pyroelectric sensing element  410   a ,  410   d  configured to produce a positive voltage in response to infrared radiation. The other zones are “negative zones”  610   a ,  610   b , which is the term herein used to refer to zones  600 ,  610  associated with a pyroelectric sensing element  410   b ,  410   c  configured to produce a positive voltage in response to infrared radiation. 
     In this example, each of the positive zones  600   a ,  600   b  is associated with pyroelectric sensing element  410   d ,  410   a , respectively. Each of the negative zones  610   a ,  610   b  is associated with pyroelectric sensing element  410   c ,  410   b , respectively. This association between zones  600 ,  610  and pyroelectric sensing elements  410  relates to which of the pyroelectric sensing elements  410 , for a given zone  600 ,  610  will respond by producing voltage to the greatest extent relative to the other pyroelectric sensing elements  410 . In other words, a heat source emitting infrared radiation from within a given zone  600 ,  610  will tend to disproportionately affect the pyroelectric sensing element  410  associated with that zone  600 ,  610  as compared to the others. This association between the zones  600 ,  610  and the pyroelectric sensing elements  410  of the PIR sensor  200  may vary depending on the physical arrangement of the components of the motion sensing device  100  and the design of the lens  210 , as will be discussed in further detail below. 
     The zones within the FoV  150  are arranged into areas  620 ,  630 . Each area  620 ,  630  includes one zone  600 ,  610  per pyroelectric sensing element  410 . In this example, the PIR sensor  200  has four pyroelectric sensing elements  410   a - d  in a quad arrangement (i.e., arranged into two pairs). Accordingly, each area comprises four zones  600   a - b ,  610   a - b.    
     The primary sensing axis of the motion sensing device  100  is the axis from which a heat source emitting a given quantum of infrared radiation at a given distance from the motion sensing device  100  will be unable to pass more of that infrared radiation through the lens  210  and onto the pyroelectric sensing elements  410   a - d , collectively, by moving to any other axis. In this example, the primary sensing axis is normal to a plane extending through the pyroelectric sensing elements  410   a - d  and extends through the center of the FoV  150 . 
     The area  620 ,  630  that intersects the primary sensing axis is herein referred to as the “primary area”  620 . The primary area  620  is the area  620 ,  630  within the FoV  150  in which detection by the PIR sensor  200  is strongest. The other areas  620 ,  630  within the FoV  150  are herein referred to as secondary areas  630   a - h . The secondary areas  630   a - h  do not intersect with the primary sensing axis. Notwithstanding, each of the secondary areas  630   a - h  comprises zones  600 ,  610  that correspond to the pyroelectric sensing elements  410 , e.g., by operation of the lens  210  (to be discussed in further detail below). These secondary areas  630   a - h  are the areas  620 ,  630  within the FoV  150  in which detection by the PIR sensor  200  is relatively weaker than that of the primary area  620 . 
     Some of the zones  600 ,  610  depicted in  FIG. 7  are entirely outside of the FoV  150 . These zones  600 ,  610  represent zones that could be comprised in additional secondary areas  630  of detection within the FoV  150 , if the FoV  150  were to be widened. Just as detection is weaker in the secondary areas  630   a - h  relative to the primary area  620 , detection may be weaker in the additional secondary areas  630  added by increasing the size of the FoV  150  relative to the secondary areas  630   a - h  that are closer to the primary sensing axis  450 . This weakening effect on detection at further distances from the primary sensing axis  450  may, e.g., be due to a reduction in IR light  440  being received by the pyroelectric sensing elements  410 . This reduction may be due to some property of the lens  210  and/or one or more lens-lets  220  therein (e.g., differences between lens-lets  220  that are more central as compared to lens-lets  220  that are more peripheral), the angle at which the IR light  440  arrives. In particular, such factors may result in each pair of pyroelectric sensing elements  410   a - b ,  410   c - d  generating a monotonically decreasing amount of differential voltage as the given quantum of infrared radiation is positioned at increasing distances away from the primary sensing axis  450 . 
     Correspondingly, if the FoV  150  were to be narrowed, particular zones  600 ,  610  (and possibly entire secondary areas  630 ) would fall outside of the FoV  150 , such that a given quantum of infrared radiation from those zones  600 ,  610  would no longer be detected by their associated pyroelectric sensing elements. That is, while zones  600 ,  610  outside of the FoV may be able to pass infrared radiation to the pyroelectric sensing elements  410   a - d  to some extent, the passed infrared radiation would be received a such a high angle of incidence or such a degree of loss that, given the detection sensitivity of the PIR sensor  200 , positive detection would not occur. Although  FIG. 7  only illustrates zones  600 ,  610  outside of the FoV  150  to the left and the right for clarity of the illustration, it should be appreciated that such zones may surround the FoV  150  in any direction, such that sufficiently increasing the diameter  125  of the FoV  150  (e.g., by electrically control) would incorporate zones in each lateral direction into the FoV  150 . 
     As discussed above, each pair of pyroelectric sensing elements  410   a - b ,  410   c - d  may include one pyroelectric sensing element  410   a ,  410   d  that produces a positive voltage (respectively) and one pyroelectric sensing element  410   b ,  410   c  that produces a negative voltage (respectively) in response to receiving infrared radiation. As shown by the arrangement of zones in the example of  FIG. 7 , the pyroelectric sensing elements  410   a - d  may be arranged in a two-by-two grid (i.e., a quad arrangement). In such an arrangement, a top one of the pyroelectric sensing elements pairs  410   a - b  may be arranged horizontally such that the positive voltage producing pyroelectric sensing element  410   a  is disposed to the left of its paired negative voltage producing pyroelectric sensing element  410   b . Further, a bottom one of the pyroelectric sensing element pairs  410   c - d  may also be arranged horizontally such that the negative voltage producing pyroelectric sensing element  410   c  is disposed to the left of its paired positive voltage producing pyroelectric sensing element  410   d.    
     It should be noted that other embodiments of the PIR sensor  200  may include quad arrangements in which the positive-negative pair is below the negative-positive pair. In yet other embodiments, the positive voltage producing pyroelectric sensing elements  410   a ,  410   d  are aligned with each other (e.g., to the left or right), and the negative voltage producing pyroelectric sensing elements  410   b ,  410   c  are aligned with each other on the other side. In still yet other embodiments, rather than each pair being arranged horizontally as in this example, other examples may each arrange each pair vertically. Notwithstanding, the most typical arrangement of pyroelectric sensing elements  410  expected to be used in practical applications is represented by the corresponding arrangement of positive and negative zones  600 ,  610  shown in  FIG. 7 ; namely, evenly-spaced pyroelectric sensing elements  410  in which neighboring pairs reverse which pyroelectric sensing element  410  produces the positive voltage and which produces the negative voltage. 
       FIG. 8A  and  FIG. 8B  schematically illustrates a cut-away view through the center of an example lens  210  such that operation of the lens  210  to direct IR light  440  from respective directions onto pyroelectric sensing elements  410   a ,  410   b  of the PIR sensor  200  may be observed from the side. The lens  210 , according to this example, comprises a plurality of lens-lets  220   a - g  along a substantially flat plane. Lens-let  220   a  is a central lens-let of the lens  210 . The central lens-let  220   a  is aligned with the primary sensing axis  450 , such that infrared radiation received by the lens  210  from the primary sensing axis  450  is passed to the pyroelectric sensing elements  410   a - b  at an average angle of incidence that is closer to 0° than infrared radiation passing through any of the other lens-lets  220  to the pyroelectric sensing elements  410   a - b.    
     The other lens-lets  220   b - g  of this example lens  210  are not aligned to the primary sensing axis and are hereinafter referred to as “off-axis lens-lets”  220   b - g . As shown in  FIG. 8B , these off-axis lens-lets  220   b - g  are less effective at transferring infrared radiation to the pyroelectric sensing elements  410   a - b , because the receiving surfaces of the pyroelectric sensing elements  410   a - b  receive infrared radiation from these off-axis lens-lets  220   b - g  at a higher angle of incidence relative to the infrared radiation received from the central lens-let  220   a . This results in aberrated signal onto the pyroelectric sensing elements  410   a - b  and a reduction in IR energy transfer efficiency. 
     It should be further noted that the off-axis lens-lets  220   b - g  produce an astigmatism on the pyroelectric sensing elements  410   a - b , which may further aberrate signal. Astigmatism is the aberrated defect of imaged or collected signal on a sensor by the relatively tilted alignment with respect to a lens element, which in this example reduces the detection sensitivity of the pyroelectric sensing elements  410   a - b  with respect to the off-axis lens-lets  220   b - g . As the off-central axis angle increases, the astigmatism aberration worsens resulting in images getting increasingly blurry or IR energy being reduced on the pyroelectric sensing elements  410  as progressively peripheral off-axis lens-lets  220   b - g  are used. 
     As a result of one or more of the factors discussed above, the pyroelectric sensing elements  410   a - b  may generate a monotonically decreasing amount of differential voltage as a given quantum of infrared radiation is positioned at increasing distances away from the primary sensing axis  450 . Accordingly, in order for the PIR sensor  200  to detect infrared radiation received via an off-axis lens-let  220   b - g  to the same degree as the central lens-let  220   a , a higher detection sensitivity is required. According to various embodiments of the present disclosure, this higher detection sensitivity is accomplished by configuring the PIR sensor  200  with a lower detection threshold, which widens the effective FoV  150  of the PIR sensor about the primary sensing axis  450 . 
     Conversely, to configure the PIR sensor  200  to disregard infrared radiation received via the central lens-let  220   a  to the same degree as a given off-axis lens-let  220   b - g , a lower detection sensitivity is required. According to various embodiments of the present disclosure, this lower detection sensitivity is accomplished by configuring the PIR sensor  200  with a higher detection threshold, which narrows the effective FoV  150  of the PIR sensor about the primary sensing axis  450 . 
     Accordingly, by controlling detection sensitivity (which may, e.g., comprise controlling one or more detection thresholds) of the PIR sensor  200 , the pyroelectric sensing elements  410  can effectively be made blind beyond a certain tilt angle of the IR light  440  away from normal. In particular, in some embodiments, a voltage differential threshold may be configured for the PIR sensor  200  such that the pyroelectric sensing elements  410  are effectively unable to detect infrared radiation from one or more of the off-axis lens-lets  220   b - g.    
     Thus, it can be seen how the strength of detection of the primary area  620  relative to that of the secondary areas  630   a - h  (as shown in  FIG. 7 ) is consistent with the effect of a lens  210  comprising a plurality of lens-lets  220   a - g  as illustrated in  FIG. 8A  and  FIG. 8B . That is, the central lens-let (which intersects the primary sensing axis) delivers maximum IR energy at an angle of incidence that is closest to normal among the plurality of lens-lets  220  of the lens  210 . Accordingly, the primary area  620 , which also intersects the primary sensing axis, is the area within the FoV  150  in which detection is strongest. 
     In addition, the further away an off-axis lens-let is from the primary sensing axis, the more the angle of incidence of infrared radiation from that off-axis lens-let to the pyroelectric sensing elements  410 , the more the signal to be detected by the pyroelectric sensing elements  410  is aberrated, and the less IR energy there is to detect, thereby requiring a higher detection sensitivity (e.g., as configured by setting a lower detection threshold) to overcome the effect of the increased angle of incidence. Correspondingly, the secondary areas  630   a - h  within the FoV  150  are areas within the FoV  150  in which detection is relatively weaker as compared to the primary area  620 . 
     Similar principles apply to lenses  200  having other shapes.  FIG. 9A  and  FIG. 9B  illustrate how the off-axis lens-lets  220   b - g  of a domed lens  210  similarly provides infrared radiation to the pyroelectric sensing elements  410   a - b  at a higher angle of incidence (see  FIG. 9B ) as compared to the angle of incidence of infrared radiation received via the central lens-let  220   a  (see  FIG. 9A ). Indeed, this effect will be true for a wide variety of lens  210  shapes and PIR sensor  200  designs in which infrared radiation arrives from some portions of the lens  210  at the pyroelectric sensing elements  410  at an angle of incidence that is greater than that of other portions of the lens. 
     Particular examples of the lens  210  may be relatively more complex than those shown in  FIGS. 8A-B  and  FIGS. 9A-B . Indeed, particular embodiments of the lens  210  may comprise any number of portions, lens-lets  220 , ridges, curves, and/or flat surfaces. In particular, the lens  210  may comprise one or more sections, each of which has its own shape. 
     Moreover, particular embodiments of the lens  210  enable a uniform distribution of detecting zones  600 ,  610  of the coverage area over a constant FoV  150 . In some such examples, the lens comprises a plurality of lens-lets  220  of varying surfaces. These varying surfaces may adjust or control the transfer of IR onto the pyroelectric sensor elements  440  in different ways, and in some such examples, provide a substantially uniform transfer of IR light throughout the FoV. In at least some such examples, the sensor threshold may produce an identical effect on detection sensitivity using some or all the lens-lets  220  which enables the FoV to also be constant. 
     Depicted in  FIGS. 10A and 10B  is an example of a lens  210  that has a complex shape that, in some embodiments, may be used with one or more PIR sensors  200 . The lens  210  comprises a plurality of lens-lets  220   h - w  (sixteen in this example), each of which forms a Fresnel lens as can be seen from the view of rear surface  36  provided in  FIG. 10B . The lens  210  is symmetrical with respect to a plane of symmetry  490  passing through the center, bisecting the lens  210  into a first lateral portion  480   a  comprising lens-lets  220   h - j ,  220   t - u , and  220   n - p , and a second lateral portion  480   b  comprising lens-lets  220 - k - m ,  220   v - w , and  220   q - s . The lens  210  of  FIGS. 10A and 10B  is asymmetric with respect to all other planes. For example, lens-lets  220   i - 1  closer to peripheral side  470   a  of the lens  210  are larger than lens-lens  220   o - r  closer to opposing peripheral side  470   b  of the lens  210 . Notwithstanding, the individual lens-lets  220   h - w  contribute to the uniformity of detecting zones  600 ,  610  within a circular FoV. Such a lens  210  may be installed in one side of a circular housing to match the curve of a fixture, such as shown in  FIGS. 13A and 13B . 
     As can be seen from the side view of  FIG. 10A , the lens  210  comprises a substantially flat front surface  34  (i.e., facing away from the pyroelectric sensing elements  410 ). The lens  210  has raised ridges  42  on a side opposite the front surface  34  (i.e., facing toward the pyroelectric sensing elements  410 ). The lens-lets  220   h ,  220   n  adjacent to peripheral end  475   a  of lateral portion  480   a  and the lens-lets  220   m ,  220   s  adjacent to peripheral end  475   b  of lateral portion  480   b  have larger surface areas relative to the lens-lets  220   i - 1 ,  220   o - r , and  220   t - w  that are disposed away from the peripheral ends  475   a ,  475   b  (i.e., the more central lens-lets). Lens-lets  220   j - k ,  220   u - v , and  220   p - q  adjacent to the plane of symmetry  490  (i.e., closest to the center) have relatively smaller surface areas relative to the remaining lens-lets. Thus, each of the lens-lets  220   h - w  may have a shape that appropriately adjusts the amount of IR light  440  falling onto the pyroelectric sensing elements  410  to provide IR light transfer that is either more uniform over the FoV  150  or variable over the FoV  150  as may be desired. In such embodiments in which a constant FoV is provided, varying the detection threshold may affect detection sensitivity to substantially equivalent degree across the FoV  150 . 
     While Fresnel lenses are often not of sufficient quality for use with imaging optics, they generally provide a large aperture and short focal lengths while remaining relatively compact, and can be very effective for non-imaging optics. Fresnel lenses may have a flat front surface  34 , with an opposite light-focusing surface including a number of ridges  42 . When such ridges  42  are comprised in a Fresnel lens, they may be referred to specifically as Fresnel ridges. Generally, the ridges  42  are used to focus light incident to a focal point. 
       FIG. 10A  and  FIG. 10B  show a number of Fresnel ridges  42  in each one of the lens-lets  220   h - w . The Fresnel ridges  42  are formed and arranged such that each one of the lens-lets  220   h - w  is configured to focus light  430 , which may be (or include) IR light  440 , from a different portion of an area of interest to one or more focal points. Generally, these focal points will correspond with the location of a pyroelectric sensing element  410  in a PIR sensor  200 . The Fresnel ridges  42  may each have a different angle, thereby producing a different refraction pattern. The overall refraction from a collection of the Fresnel ridges  42  in each lens-let  220   h - w  forms a desired aperture and focal length, thereby providing a desirable response. 
     Given that a lens  210  comprising a plurality of lens-lets  220   h - w  (such as the example lens  210  illustrated in  FIG. 10A  and  FIG. 10B ) may direct light  430  to a relatively large number of different focal points, such a lens  210  may be well suited for use with more than one light sensor (e.g., one or more PIR sensors  200  and/or one or more ambient light sensors). Moreover, the lens  210  may be well suited for receiving light  430  from a relatively large overall FoV  150  of the motion sensing device  100  based on the combined individual FoVs  150  of individual sensors. 
     The lens  210  may include one or more mounting clips  44 , e.g., as shown in  FIG. 10A . The mounting clips  44  are configured to interlock with a surface (e.g., a flange) of the motion sensing device  100  (e.g., at the sensor housing  230 ) in order to secure the lens  210  in place. While the front surface  34  of the lens  210  is discussed and shown being substantially flat, the front surface  34  of the lens  210  may include one or more peripheral ridges, or may be patterned or textured. 
     Although the lens  210  may be used with any light-based sensor, particular embodiments of the lens  210  discussed herein are particularly useful with PIR sensors  200  intended to detect human occupancy. Accordingly, in some embodiments, the lens  210  may be used with an ambient light sensor and/or a motion sensor. Moreover, the lens  210  may be formed by any suitable material. In one embodiment, the lens  210  is formed from high density poly-propylene (HDPP), high density poly-ethylene (HDPE), Zinc Selenide (ZnSe), Zinc Sulfide (ZnS), or other transparent polymetric materials over IR wavelengths of, e.g., eight to fourteen microns. 
     In some embodiments of the lens  210 , one or more sections of the lens  210  comprise light redirection features (e.g., lens-lets  220 , Fresnel ridges  42 ) whereas others do not comprise light redirection features. The sections lacking light redirection features may be configured to pass light  430  through unfocused, whereas sections  40  that do comprise light redirection features may be configured to focus light as discussed above. In one embodiment, a first sensor (e.g., a PIR sensor  200 ) is placed behind one or more lens lens-lets  220  comprising light redirection features, while a second sensor (e.g., an ambient light sensor) is placed behind a section that is transparent and does not have light redirection features. The first sensor may, for example, be one that requires access to light information within a relatively large area of interest, while the second sensor may be one that only requires access to light information directly below the lens  210 . Dividing the lens  210  into ridged and non-ridged sections, for example, may allow the lens  210  to service multiple sensors while providing a substantially uniform front surface  34 , which may improve the aesthetic appeal of the lens  210 . 
     The lens  210  may be manufactured by any number of processes. In one embodiment, the lens  210  is molded via an injection molding process. In another embodiment, the lens  210  is milled out of a piece of material, for example, via a computer numerical control (CNC) router or mill. In yet another embodiment, the lens  210  may be printed via a three-dimensional (3D) printer. 
     In contrast to the lenses  210  illustrated in  FIGS. 8A-B  and  FIGS. 9A-B  (each of which has an outer periphery that is circular in shape, other lenses may have an outer periphery  38  having other shapes. For example, the outer periphery  38  of the lens  210  illustrated in  FIG. 10A  and  FIG. 10B  has a relatively complex shape. Other lenses  210  according to other embodiments of the present disclosure may have yet other shapes, and may include one or more sections, and each section may comprise any light redirection feature described herein (e.g., lens-lets  220 , ridges  42 ). 
       FIG. 11A ,  FIG. 11B , and  FIG. 11C , for example, illustrate top views of lenses  210  comprising an outer periphery having circular, square, and rectangular shape, respectively. Each of the lenses  210  comprises a plurality of sections. In these examples, each of the sections forms a Fresnel lens  42 . The particular shape of the outer periphery  38  of the lens  210  may be chosen based on the particular needs of the application for which it is being used. For example, the motion sensing device  100  may be installed in, or integrated into, different types of environments, surfaces, and devices (e.g., lighting fixtures) having different areas, shapes, and visual appearances that lend themselves to using a differently shaped lens  210 . In general, it may be advantageous for the lens  210  to be shaped to minimize the visual impact of the lens  210  and therefore blend in with its environment. Despite the different peripheries, the FoV  150  can provide a circular coverage area and zone distributions substantially similar to those of other embodiments. Further, the FoV  150  may be formed in any shape, consistent with aspects described above. 
     Indeed, visually blending the lens  210  with the its surroundings (e.g., a lighting fixture into which it is integrated) may provide a desirable aesthetic appearance. One way to visually blend the lens  210  with its surroundings is to substantially match the perceived color of the lens  210  to an adjacent surface  130 . However, the lens  210  must be colored in such a way as to still remain functional. In particular, the lens  210  must permit energy within a desired wavelength or band of wavelengths to pass through such that the PIR sensor  200  receives energy in a frequency band that it can detect. The lens  210  is transparent typically over IR of eight to fourteen microns despite being opaque over visible wavelengths. 
     In some embodiments, the surface adjacent to the lens  210  may reflect visible light within a first wavelength or band of wavelengths. For example, if the adjacent surface  130  is that of a lighting fixture, the adjacent surface  130  is likely to be generally opaque. Accordingly, the adjacent surface  130  will generally reflect and/or absorb much of the visible and non-visible light incident thereto. The particular wavelength or wavelengths of visible light reflected by the adjacent surface  130  determines the perceived color of the exterior surface. The lens  210  may be colored in order to reflect a similar wavelength or wavelengths as the exterior surface of the lighting fixture such that the lens  210  appears to be the same or a similar color as the adjacent surface  130 . For example, if the adjacent surface  130  is grey, the lens  210  may be colored such that it is similarly grey. Further, the lens  210  may be colored in order to maintain a minimum average transmittance within a desired wavelength or band of wavelengths (e.g., some or all of the infrared spectrum), which are delivered to the PIR sensor  200  in order to provide the functionality thereof. In one embodiment, the desired wavelength or band of wavelengths include visible light between 380 nm and 780 nm. In another embodiment, the desired wavelength or band of wavelengths include infrared energy between 780 nm and 1000 nm. In yet another embodiment, the desired wavelength or band of wavelengths include thermal infrared energy between 1000 nm and 14 μm. Accordingly, the lens  210  may be used with many different sensors  46  such as ambient light sensors and/or PIR sensors  200 , among other things. 
     In some embodiments, the lens  210  is colored via one or more dyes introduced into the material of the lens  210  during manufacturing. In other embodiments, the lens  210  is colored via a film placed over the front surface  34  of the lens  210 , for example, the lens  210  may be colored via a multi-layer interference thin-film coating deposited on the front surface  34  of the lens  210 . In yet another embodiment, the lens  210  is colored via a paint or dye applied to the front surface  34  of the lens  210 . In general, the lens  210  may be colored via any suitable means without departing from the principles of the present disclosure. In certain embodiments, the particular dyes, pigments, paints, or the like may be specifically chosen to reflect certain wavelengths of light while absorbing others to achieve a desired filtration effect for light passing through the lens  210 . 
     In the example of  FIG. 12A , operation of a lens  210  comprising coloring as described above is shown. In particular,  FIG. 12A  illustrates a lens  210  in which dyes or other materials have been added during the manufacturing thereof such that the material of the lens  210  and/or a material placed thereon is configured to reflect visible light within a first wavelength or band of wavelengths λ 1  while passing light within a second wavelength or band of wavelengths λ 2 . Accordingly, visible light about the first wavelength or band of wavelengths λ 1  and incident to the front surface  34  of the lens  210  is shown reflecting off the front surface  34 . In some cases, only a portion of visible light about the first wavelength or band of wavelengths λ 1  is reflected by the lens  210 . Accordingly,  FIG. 12A  shows a portion of the incident visible light about the first wavelength or band of wavelengths λ 1  reflecting off the lens  210 . The portions of light about the first wavelength or band of wavelengths λ 1  reflected from the lens  210  determine the perceived color of the lens  210 . Light about the second wavelength or band of wavelengths λ 2 , which may be IR light or non-visible light in various embodiments, is shown passing through the lens  210  and to the PIR sensor  200 . In some cases, only a portion of light about the second wavelength or band of wavelengths λ 2  is passed by the lens  210 . Accordingly,  FIG. 11A  shows a portion of the incident light about the second wavelength or band of wavelengths λ 2  reflecting off the front surface  34  of the lens  210 . 
     In one embodiment, the first wavelength or band of wavelengths λ 1  includes visible light between about 380 nm and 780 nm. The second wavelength or band of wavelengths λ 2  may include visible light between 380 nm and 780 nm, infrared energy between 780 nm and 1000 nm, and thermal infrared energy between 1000 nm and 14 μm. The average transmittance of the lens  210  may be greater than 10% and less than 90%, depending on wavelength. Average transmittance defines how much (on average) radiant energy received by a particular surface is passed through the surface. Accordingly, the average transmittance of the lens  210  determines how much visible light, infrared energy, and/or thermal infrared energy is received by the PIR sensor  200 . As discussed above, the PIR sensor  200  must receive a minimum amount of energy in order to remain functional. The particular coloring used for the lens  210  takes this into consideration, striking a balance between matching the hue of the adjacent surface  130  and providing a minimum amount of energy to the PIR sensor  200 . 
       FIG. 12B  shows the lens  210  according to other embodiments of the present disclosure. The lens  210  shown in  FIG. 12B  is substantially similar to that shown in  FIG. 12A , except that the coloring of the lens  210  is accomplished via a thin-film layer. The thin-film layer  58  may be a paint or dye that has been applied to the front surface  34  of the lens  210 , or may be a separate piece of material that is applied to the front surface  34  of the lens  210 , for example, via an adhesive. The lens  210  shown in  FIG. 12B  behaves similarly to that described above with respect to  FIG. 12A , wherein the lens  210  reflects visible light within a first wavelength or band of wavelengths λ 1  while passing light within a second wavelength or band of wavelengths λ 2  through the lens  210  and to the PIR sensor  200 . In some embodiments, the front surface  34  of the lens  210  may be slightly recessed from the adjacent surface  130  such that even with the thin-film layer  58  applied the lens  210  sits substantially flush with the adjacent surface  130 . 
     Another way to aesthetically blend the appearance of the lens  210  and an adjacent surface  130  is to provide a continuous visual pattern over the adjacent surface  130  and the lens  210 .  FIG. 13A  and  FIG. 13B  each illustrate a lighting fixture  10  that has a visual pattern  60  over an exterior surface that is adjacent to the front surface  34  of the lens  210 . Specifically,  FIG. 13A  shows the lighting fixture  10  in which a visual pattern  60  of lines is over the exterior surface and the lens  210 , whereas  FIG. 13B  shows the lighting fixture  10  in which a visual pattern  60  of dots or specs resembling those found on the surface of drop-ceiling tiles is over the exterior surface and the lens  210 . As described herein, a “continuous” visual pattern is one that is substantially uninterrupted by the border between the exterior surface and the lens  210 . 
     While only two visual patterns  60  are illustrated for reference, any number of different visual patterns  60  may be over the lens  210  and an adjacent surface  130  without departing from the principles of the present disclosure. For example, stripes of any orientation, decorative designs, noise/static, or any other pattern may be over the lens  210  and an adjacent surface  130  without departing from the principles of the present disclosure. The visual pattern  60  of the lens  210  may be chosen based on the type of surrounding in which the lens  210  is installed. For example, the visual pattern  60  may be chosen to match a pattern or texture present on the light fixture, which itself was chosen to match a pattern on a ceiling in which the lighting fixture  10  is installed. 
     As the size of the motion sensing device  100  and/or the lens  210  decreases, the visual pattern  60  may allow the lens  210  to essentially disappear within the visual pattern  60 . For example, a lens  210  having a radius of 5 mm, 3 mm, or even 1 mm may blend completely in with a visual pattern  60  including one or more shapes of about the same size. In other embodiments wherein the lens  210  cannot be made sufficiently small to blend in this way, the continuous nature of the visual pattern  60  between the exterior surface of the adjacent surface  130  and the lens  210  may create a visual appearance of continuity, which allows the lens  210  to aesthetically blend with adjacent surface  130 . 
     The visual pattern  60  may be applied in any suitable manner without departing from the principles of the present disclosure. For example, the visual pattern  60  may be painted on, applied via a decal, etched on, or applied via any other suitable process. In one embodiment, the visual pattern  60  is applied on the front surface  34  of the lens  210 . In an additional embodiment, the visual pattern  60  is embedded in the material of the lens  210 . 
     The visual pattern  60  may reduce the overall intensity of the light received by the PIR sensor  200 . In this regard a visual pattern  60  that is overly dense and/or opaque will diminish the average transmittance of the lens  210  to the point where the PIR sensor  200  no longer functions properly. Accordingly, embodiments of the present disclosure strike a balance between the density and/or opacity of the visual pattern  60  and a desired intensity of light to be received by the PIR sensor  200 , as given by Equation 3 below: 
       ( P   SCP   *T   P )+( P   SCNP   *T   SC )= T   AVE   (Eq. 3)
 
     where P SCP  is the percentage of the lens  210  covered by the visual pattern  60 , T P  is the average transmittance of the visual pattern  60 , P SCNP  is the percentage of the lens  210  not covered by the visual pattern  60 , T SC  is the average transmittance of the lens  210 , and T AVE  is the overall average transmittance of the lens  210 . In some embodiments, the lens  210  is designed such that the overall average transmittance T AVE  of the lens  210  is greater than about 10%. Generally, the overall average transmittance T AVE  of the lens  210  may be between about 10% and 90% while still providing adequate energy to the PIR sensor  200 . 
     Notably, the continuous pattern may be used along with the coloring described above to achieve further aesthetic blending of the lens  210  with an adjacent surface  130 . That is, in addition to providing the lens  210  with coloring such that the perceived color of the lens  210  matches that of an exterior surface of, e.g., a lighting fixture  10 , a continuous visual pattern may also be provided on the lens  210  and the adjacent surface  130 . 
     As suggested by the examples of  FIG. 13A  and  FIG. 13B , devices and techniques for motion sensing may be particularly advantageous to supplement the features of lighting devices. Accordingly, particular embodiments of the present disclosure include a motion sensing device  100  in which a lighting fixture  10  is integrated or is in communication. Example methods and structures additional to those explicitly described herein that may enhance the effective integration of the motion sensing device  100  into a light fixture  10  may be found in U.S. Pat. No. 10,234,121 issued Mar. 19, 2019 and U.S. Pat. No. 10,480,996 issued Nov. 19, 2019, the entire disclosure of each of which is hereby incorporated by reference. 
     Many of the aspects described above relate to effectively directing infrared radiation from within the FoV  150  to a PIR sensor  200 . To adapt the FoV  150  by electrically controlling the PIR sensor  200 , the PIR sensor  200  supports an electrical connection to other components within the motion sensing device  100 .  FIG. 14A  and  FIG. 14B  illustrate examples of the connectors  500  supported by respective PIR sensors  200  according to particular embodiments of the present disclosure. Each of the example PIR sensors  200  illustrated is a digital PIR sensor that comprises respective connections  500   b ,  500   c  for power and ground. The PIR sensors  200  of  FIG. 14A  and  FIG. 14B  differ, however, in that the PIR sensor  200  of  FIG. 14A  comprises connections  500   a ,  500   d  that are respectively dedicated for control input and output, whereas the PIR sensor  200  of  FIG. 14B  comprises a connection  500   e  that supports multiplexed input and output. 
     The PIR sensor  200  of various embodiments may support a wide variety of control inputs via the control input connection  500   a ,  500   e . Among other things, signaling to configure detection sensitivity, an operation mode of the PIR sensor  200 , blind time, filtering (e.g., to designate low-pass filtering or band-pass filtering), and/or window time may be electrically signaled to the PIR sensor  200  via the control input connection  500   a ,  500   e . This signaling may occur at a variety of appropriate times. For example, the detection sensitivity may be adjusted at power up and/or by issuing a special control command, signal, and/or string over the control input connection  500   a ,  500   e  as needed. 
     In particular, the detection sensitivity of the PIR sensor  200  may be electrically controlled using any of a plurality of sensitivity settings, depending on the embodiment. For example, the PIR sensor  200  may support a range of sensitivity settings from a highest sensitivity setting to a lowest sensitivity setting. These values, for example, may correspond to a sensitivity of an Analog-to-Digital Converter (ADC) of the PIR sensor (e.g., to increments of the smallest amount of change to the analog input that will produce a change in digital output from the ADC) and used to specify the threshold amount of differential voltage required to generate an output signal indicating that infrared radiation (or motion) has been detected. 
     In one such example, the PIR sensor  200  supports a range of sensitivity settings from 1 (i.e., the highest sensitivity) to 255 (i.e., the lowest sensitivity). One or more of these values may be associated with predefined sensitivity levels of the PIR sensor  200 . For example, the values 10, 38, and 62 may be designated as high, medium, and low sensitivity, which may (for example) simplify configuration of the PIR sensor  200  by limiting options or guiding users to appropriate settings for particular applications. 
     In some embodiments, electrical control of the detection sensitivity of the PIR sensor  200  is limited to a subset of the supported sensitivity settings, e.g., to prevent the PIR sensor from being configured with a sensitivity setting that is inappropriate for the application in which it will be used. For example, the motion sensing device  100  may avoid or prevent the PIR sensor  200  from being configured with a sensitivity setting that is too sensitive and/or too insensitive for the operating environment. As one example, the motion sensing device  100  may avoid or prevent configuring the PIR sensor  200  with values less than 10 (i.e., the high setting) and more than 62 (i.e., the low setting). Additional, fewer, and/or different settings, values, and/or ranges may be supported and/or used according to other embodiments. 
     The effect of particular sensitivity settings on the size of the FoV  150  for one or more mounting distances may be tabulated in advance and stored (e.g., programmed) in a memory of the motion sensing device  100 .  FIG. 15  is an example table  770  that indicates, for each of a plurality of mounting heights, a diameter  125  of the FoV  150  of the motion sensing device  100  at each of three sensitivity settings (i.e., high, medium, and low). As shown in  FIG. 15 , increasing and decreasing the mounting distance correspondingly increases and decreases the diameter  125  of the FoV  150 , respectively. Additionally, increasing and decreasing the sensitivity at a given mounting distance increases and decreases the diameter  125  of the FoV  150 , respectively. 
     Given a table  770  that maps FoV  150  sizes to sensitivity settings for each of a plurality of distinct mounting distances, the motion sensing device  100  may accept requests to adapt the FoV  150  to a desired FoV, e.g., via a communications network (e.g., via Wi-Fi). Responsive to receiving such a request, the motion sensing device  100  may obtain a sensitivity setting corresponding to the desired field of view from the table  770 , and adapt the FoV  150  by electrically controlling the detection sensitivity by applying the sensitivity setting to the detection sensitivity of the PIR sensor  200 . In this way, the FoV  150  may be adapted to the desired field of view. 
     In some embodiments, the motion sensing device  100  may support requests to adapt the FoV  150  to a desired FoV despite that desired FoV being absent from the table  770 . In some such embodiments, the motion sensing device  100  may select the sensitivity setting that maps most closely to the desired field of view from the sensitivity settings corresponding to the mounting distance of the motion sensing device  100 . Accordingly, the mounting distance of the motion sensing device  100  may be configured and stored in memory, e.g., so that the motion sensing device  100  may select an appropriate sensitivity from the table  770  to fulfill the request. That said, in some embodiments, the mounting height may be included in the request itself. 
     Moreover, in some embodiments, the motion sensing device  100  may set the detection sensitivity of the PIR sensor  200  to a detection sensitivity that has been preselected, e.g., to establish a default FoV  150  around the primary sensing axis of the motion sensing device  100 . For example, the motion sensing device  100  may set the PIR sensor  200  to a high sensitivity upon power up, which may provide the user with a generally useful and responsive product upon initial installation and/or after recovery from a power failure, for example. 
     In view of all of the above,  FIG. 16  is a flow diagram illustrating an example method  600  implemented by a motion sensing device  100 . The method  600  may begin, e.g., upon startup of the motion sensing device  100  (e.g., in response to receiving power, by receiving an activation signal) (block  605 ). The method  600  comprises obtaining an initial sensitivity setting (block  610 ), and adapting a FoV  150  around a primary sensing axis  450  of the motion sensing device  100  by electrically controlling a detection sensitivity of a PIR sensor  200  of the motion sensing device  100  (block  615 ). In this regard, the initial sensitivity setting may correspond to preselected detection sensitivity, and adapting the FoV  150 , in this case, may comprise setting the detection sensitivity of the PIR sensor  200  to the preselected detection sensitivity in order to establish a default FoV  150 . 
     The method  600  further comprises monitoring for motion within the FoV using the PIR sensor  200  (block  620 ), and if motion is detected within the FoV  150  (block  625 , yes path) generating an output signal indicating that the motion is detected (block  630 ). If the motion is not detected, the output signal is not generated (block  625 , no path). 
     In some embodiments, the PIR sensor  200  comprises at least one pair of pyroelectric sensing elements  410   a - b ,  410   c - d  for detecting the motion. Each of the pairs may be configured to generate an amount of differential voltage between its pyroelectric sensing elements based on an amount of exposure to infrared radiation. Accordingly, in some embodiments of the method  600 , the output signal of the motion sensing device  100  is controlled based on whether or not any pair of pyroelectric sensing elements generates the differential voltage in excess of the voltage threshold. This voltage threshold may correspond to the detection sensitivity of the PIR sensor  200 . 
     Thus, when the FoV  150  is adapted by electrically controlling the detection sensitivity of the PIR sensor  200 , the voltage threshold may, e.g., be configured such that at least one of the pairs of pyroelectric sensing elements  410   a - b ,  410   c - d  is configured to generate the differential voltage in excess of the voltage threshold when a given quantum of infrared radiation, external to the motion sensing device  100 , is within the FoV  150 . Correspondingly, the voltage threshold may be configured such that those pairs do not generate the differential voltage in excess of the voltage threshold when the given quantum of infrared radiation is outside of the FoV  150 . 
     Further, depending on the embodiment, the method may comprise, while monitoring for motion, receiving, at a pair of pyroelectric sensing elements, more or less of the given quantum of infrared radiation based respectively on whether the given quantum of infrared radiation is closer to or more distant from the primary sensing axis. The pyroelectric sensing elements  410  may receive the infrared radiation in this way, e.g., due to its arrangement of components, position, lens shape, and/or other factors. In particular, receiving more or less of the given quantum of infrared radiation may be based respectively on whether an angle of incidence of the given quantum of infrared radiation upon the at least one pyroelectric sensing element is lower or higher. 
     As an even further example, to generate the amount of differential voltage between its pyroelectric sensing elements  410   a - b ,  410   c - d  based on an amount of exposure to infrared radiation, each pair of pyroelectric sensing elements  410   a - b ,  410   c - d  may be configured to generate a monotonically decreasing amount of differential voltage as the given quantum of infrared radiation is positioned at increasing distances away from the primary sensing axis. Thus, configuring the voltage threshold such that at least one of the pairs of pyroelectric sensing elements  410   a - b ,  410   c - d  is configured to generate the differential voltage in excess of the voltage threshold when the given quantum of infrared radiation is within the FoV  150  and to not generate the differential voltage in excess of the voltage threshold when the given quantum of infrared radiation is outside of the FoV  150  may comprise configuring the voltage threshold such that the monotonically decreasing amount of differential voltage decreases below the voltage threshold at a peripheral end  160  of the FoV  150 . 
     The method  600  further comprises determining whether a request to adapt the FoV  150  to a desired FoV is received via a communication network (block  635 ). If not (block  635 , no path), then in accordance with the method  600 , the motion sensing device  100  may continue monitoring for motion in the existing FoV  150  as previously described (block  620 ). On the other hand, if such a request is received (block  635 , yes path), then in accordance with the method  600  and responsive to the request, the motion sensing device  100  obtains a sensitivity setting corresponding to the desired FoV from a table  770  mapping field of view sizes to sensitivity settings (block  640 ), and again adapts the FoV  150  around the primary sensing axis  450  of the motion sensing device  100  by electrically controlling the detection sensitivity (block  615 ). This time, adapting the FoV  150  by electrically controlling the detection sensitivity comprises applying the sensitivity setting from the table  770  to the detection sensitivity of the PIR sensor  200  such that the FoV  150  is adapted to the desired FoV. As previously discussed, the table  770  may further map FoV sizes to sensitivity settings for each of a plurality of distinct mounting distances. Accordingly, in some embodiments, obtaining the sensitivity setting corresponding to the desired FoV from the table  770  comprises selecting the sensitivity setting that maps most closely to the desired FoV from a plurality of sensitivity settings corresponding to a mounting distance of the motion sensing device  100 . 
       FIG. 17  schematically illustrates an example motion sensing device  100  comprising certain electrical components, according to particular embodiments of the present disclosure. For clarity of explanation,  FIG. 17  omits the mechanical features of the motion sensing device  100  previously discussed to more closely focus on computational aspects. Notwithstanding, it should be understood that the motion sensing device  100  of  FIG. 17  may further comprise any of the hardware aspects discussed above. 
     The motion sensing device  100  comprises a PIR sensor  200  and control circuitry that is communicatively coupled to the PIR sensor  200 . The control circuitry  710  may comprise one or more microprocessors, microcontrollers, hardware circuits, discrete logic circuits, hardware registers, digital signal processors (DSPs), field-programmable gate arrays (FPGAs), application-specific integrated circuits (ASICs), or a combination thereof. For example, the control circuitry  710  may comprise programmable hardware capable of executing software instructions  760  stored, e.g., as a machine-readable computer program in memory circuitry  720  that is communicatively coupled to the control circuitry  710 . 
     The memory circuitry  720  may comprise any non-transitory machine-readable media known in the art or that may be developed, whether volatile or non-volatile, including but not limited to solid state media (e.g., SRAM, DRAM, DDRAM, ROM, PROM, EPROM, flash memory, solid state drive, etc.), removable storage devices (e.g., microSD card), and/or hard disk drive. 
     The control circuitry  710  is configured to adapt an FoV  150  around a primary sensing axis  450  of the motion sensing device  100  by electrically controlling a detection sensitivity of the PIR sensor  200 . The control circuitry  710  is further configured to, responsive to adapting the FoV  150 , monitor for motion within the FoV  150  using the PIR sensor  200 . 
     In some embodiments, the motion sensing device  100  further comprises interface circuitry  730  communicatively coupled to the control circuitry  710 . The interface circuitry  730  may be a controller hub configured to control the input and output (I/O) data paths of the motion sensing device  100 . Such I/O data paths may include data paths for exchanging signals over a communications network and/or data paths for exchanging signals with a user. For example, the interface circuitry  730  may comprise a transceiver configured to send and receive communication signals over Wi-Fi, Ethernet, Bluetooth®, NFC, a serial bus (e.g., a 2-wire bus supporting DALI), and/or an optical network. 
     The interface circuitry  730  may be implemented as a unitary physical component, or as a plurality of physical components that are contiguously or separately arranged, any of which may be communicatively coupled to any other, or may communicate with any other via the control circuitry  710 . For example, the interface circuitry  730  may comprise output circuitry  740  (e.g., transmitter circuitry configured to send communication signals over a communications network  105 ) and input circuitry  750  (e.g., receiver circuitry configured to receive communication signals over a communications network). 
     According to some embodiments, the memory circuitry is configured to store a table  770  mapping FoV sizes to sensitivity settings, and the interface circuitry  730  is configured to receive, via a communication network, a request to adapt the FoV  150  to a desired FoV. The control circuitry  710  is configured to, responsive to the request, obtain a sensitivity setting corresponding to the desired FoV from the table  770 , and apply that sensitivity setting to the detection sensitivity of the PIR sensor  200  such that the FoV  150  is adapted to the desired FoV. 
     The PIR sensor  200  is configured to accept input from, and provide output to, the control circuitry  710 . In some embodiments, the PIR sensor  200  comprises at least one pair of pyroelectric sensing elements  410   a - b , each pair being configured to generate an amount of differential voltage between its pyroelectric sensing elements  410  based on an amount of exposure to infrared radiation. In such embodiments, the control circuitry may be further configured to control an output signal of the motion sensing device  100  based on whether or not any pair of pyroelectric sensing elements  410  generates the differential voltage in excess of a voltage threshold corresponding to the detection sensitivity. In some embodiments, the PIR sensor  200  may be digital and comprise one or more connectors  500   a ,  500   d ,  500   e  by which the PIR sensor  200  is communicatively coupled to the control circuitry  710 . 
     In some embodiments, the motion sensing device  100  further comprises power circuitry  780 , which is communicatively coupled to the control circuitry  710 . The power circuitry  780  is configured to regulate power to one or more loads  790  and/or one or more of the components of the motion sensing device  100  illustrated in  FIG. 17 , e.g., based on control signaling from the control circuitry  710 . In some embodiments, the motion sensing device  100  further comprises at least one the loads  790 . Additionally or alternatively, one or more of the loads  790  may be external to the motion sensing device  100 , and coupled to the power circuitry  780  via one or more lines, wires, cables, and/or connectors. According to particular embodiments of the present disclosure, one or more of the loads  790  comprises a light source  795 , such as a lighting fixture  10 . 
     To regulate power, some embodiments of the power circuitry  780  comprise a driver  785  and/or a power supply  787 . For example, to regulate power, a driver  785  of the power circuitry  780  may be configured to drive constant current. Additionally or alternatively, to regulate power, a power supply  787  may be configured to supply a constant voltage. Particular embodiments comprise a driver  785  and a power supply  787  to regulate power to respective loads  790  and/or components of the motion sensing device  100 . 
     In one particular example, the driver  785  may be a Light Emitting Diode (LED) driver, and the load  790  may comprise a light source  795  that comprises one or more LEDs. In this regard, the LED driver may have outputs matched to the electrical characteristics of the LED(s) in order to provide constant current while compensating for changes in forward voltage. 
       FIG. 18  is a diagram of an example motion sensing device  1800  that includes an analog PIR sensor  1810  that may include a lens  1815  and may have three terminals: drain  1820 , ground  1830 , and raw output  1840 . The raw output  1840  may be an analog signal received by a conditioning circuit  1850  to generate a conditioned output  1855 . The conditioning circuit  1850  may include one or more filters, amplifiers, and/or comparators that are configured to transform the raw output  1840 . In some embodiments, the conditioning circuit  1850  may include one or more components for field of view and sensitivity control. 
     The analog PIR sensor  1810  may lack embedded intelligence that is typical of digital PIR sensors. With such an analog PIR sensor, FoV adjustment may be accomplished by circuitry external to the sensor  1810 . In some embodiments, sensitivity control may be provided by components in the conditioning circuit  1850  and/or by other external circuitry. 
     Similar sensing methods may be employed by or with both the analog PIR sensor  1810  and the digital PIR sensors described herein. For example, as described above with reference to  FIG. 6 , a motion sensing device utilizing an analog sensor may similarly detect motion by comparing a voltage of an output signal (e.g., conditioned output  1855 ) to a threshold voltage. The output signal may be produced by the analog PIR sensor in response to infrared radiation received from a heat source moving within an FoV of the motion sensing device. 
       FIG. 19  is a circuit and block diagram of an example motion sensing device  1900  that includes electrical sensitivity control for an analog PIR sensor  1910 . The device  1900  may include a digital potentiometer  1960  in communication with a conditioning circuit  1950 . The analog PIR sensor  1910  may generate a raw output  1940  that may be received by the conditioning circuit  1950 . The conditioning circuit  1950  may include a first amplifier and filter stage  1951 , a second amplifier and filter stage  1952 , and a comparator  1953 . First and second amplifier stages  1951 ,  1952  may include non-inverting or inverting amplifiers, in some embodiments. Components R 17  and C 16  and R 19  and C 19  may act as filters for the first amplifier and filter stage  1951 . Resistors R 17  and R 19 , along with op-amp U 11 C, may define the gain or amplification of the first amplifier stage  1951 . The second amplifier stage  1952  may similarly alter the output  1940 , with components R 18  and C 17  acting as one filter, R 20  and C 20  acting as another filter, and amplifier stage gain being defined by R 18  and R 20  with op-amp U 11 D. The second amplifier stage  1952  may be used for AC amplification, and may apply a greater amplification to the output  1940  relative to the first amplifier stage  1951 . An output of the second amplifier stage  1952  may be received by and input to the comparator  1953 , which may compare the received filtered and amplified output  1940  to one or more reference voltages. The reference voltages may be set by a resistor divider network, which uses multiple resistors to divide an applied voltage V DD  into multiple reference voltages. The output of this comparison (e.g., conditioned output  1955 ) may be received by a controller  1970  to detect motion, which, in turn, selectively activates a load  1972  (e.g., light, indicator, lock, etc.) via a load driver  1971 . 
     The resistor divider network may include one or more programmable resistors  1965   1 ,  1965   2  (which may be referred to individually as a programmable resistor  1965  or collectively as the programmable resistors  1965 ) that may provide a desired resistance responsive to electronic commands. The programmable resistors  1965  may be a part of or otherwise controlled by (e.g., have their resistances controlled by) the digital potentiometer  1960 . The digital potentiometer  1960  may receive a user command (e.g., directly or through the controller  1970 ) and, in response, set the resistances of one or both of the programmable resistors to set the upper and/or lower thresholds applied by the comparator  1953 . By either increasing (or decreasing) the resistance of the programmable resistors  1965 , the threshold voltage to which the raw output  1940  may be compared may be increased (or decreased). Because motion closer to a primary sensing axis of a sensor&#39;s FoV produces a higher voltage than motion farther from the primary sensing axis, increasing (or decreasing) the threshold voltage excludes (or includes) detected motion farther from the primary sensing axis, thereby reducing (or increasing) the effective FoV of the motion sensing device. 
     The digital potentiometer  1960  may include a single limb, two limbs, or multi-limb potentiometer, and may be in communication with the controller  1970 . The controller  1970  may receive and determine motion based on the conditioned output  1955 , as noted above, and may also provide input commands to the digital potentiometer  1960  to control one or more comparison thresholds to set the sensitivity of the device  1900 . For example, the potentiometer may receive, from the controller  1970 , data indicative of a desired resistance value for the programmable resistor(s), of a threshold voltage for the comparator that may be used to derive a resistance value, and/or of a desired FoV that may be used to derive a threshold voltage. These data may be received by the controller  1970  from a user. In response, the digital potentiometer  1960  may alter or otherwise adjust the resistance value(s) of the programmable resistor(s)  1965  based on the received data. As shown in  FIG. 19 , the digital potentiometer  1960  may include two programmable resistors  1965 , labelled as  1965   1 ,  1965   2 , as part of the resistor divider network that also includes resistors R 24  &amp; R 25 . 
       FIG. 20  is a circuit diagram of an example motion sensing device  2000  that includes a signal conditioning circuit  2050 . The conditioning circuit  2050  may be similar to the conditioning circuit  1850  except as described differently herein. In particular, amplifier and filtering stages  2051 ,  2052  may include one or more programmable resistors  2065  that may be included in or may be in communication with a digital potentiometer  1960  and may each have an adjustable resistance value. In turn, the digital potentiometer may be in communication with the controller  1970 . 
     The digital potentiometer  1960  may include a single limb, two-limb, or multi-limb potentiometer, and may be in communication with the controller  1970 . The controller  1970  may receive and determine motion based on the conditioned output  1955 , as noted above, and may also provide input commands to the digital potentiometer  1960  to control one or more resistance values to set the sensitivity of the device  1900 . For example, the potentiometer may receive, from the controller  1970 , data indicative of a desired resistance value for the programmable resistor(s), of a desired amount of filter gain for each of the amplifier and filtering stages  2051 ,  2052  that may be used to derive a resistance value, and/or of a desired FoV that may be used to derive a desired amount of gain. These data may be received by the controller  1970  from a user. The digital potentiometer  1960  may alter or otherwise adjust the resistance value(s) of the programmable resistor(s)  2065  based on the received data. 
     The programmable resistors  2065  may enable the gain and/or amplification applied to the raw output signal  1940  to be changed. As discussed above, when the sensor  1910  detects motion, the voltage output as part of the raw output signal  1940  may be directly correlated to the proximity of the detected motion to a primary sensing axis of the sensor  1910 . By increasing (or decreasing) the gain of the amplifier(s) that receive the raw output signal  1940  (e.g., by altering the resistance(s) of the programmable resistors  2065 ), the scale of the amplitude of the input signal to the comparator  1953  may be set, and the sensitivity and effective FoV of the sensor may correspondingly be set. For example, by increasing the gain of one or both amplifier stages  2051 ,  2052 , the changes to the raw output signal  1940  may correspondingly be greater, and the sensitivity of the device  2000  may be increased. 
       FIG. 21  is a circuit diagram of a motion sensing device  2100  that includes a converter  2180  that may provide a threshold voltage for the comparator  1953  based on a signal received from a controller  1970 . The converter  2180  may be a digital-to-analog converter (DAC), such that the signal received from the controller  1970  may be a digital signal, and the signal output by the converter  2180  and received by the comparator  1953  may be an analog signal. The digital signal from the controller  1970  may be or may include data indicative of a threshold voltage for the comparator and/or of a desired sensitivity or FoV that may be used to derive a threshold voltage. The converter  2180  converts this signal to an analog signal that may be input to the comparator  1953  as a threshold against which the output signal  1940  from the analog PIR sensor  1910  (following amplification by the amplifier  1954 ) may be compared. The output  1955  of this comparison may be output to the controller  1970 , which may be configured to analyze the output to determine if motion is detected. As discussed above with relation to  FIG. 19 , by altering the comparator  1953  threshold, the effective FoV of the motion sensing device  2100  can be controlled. 
       FIG. 22  is a circuit diagram of a motion sensing device  2200  in which a fixed voltage chip  2291  is fixed to a reference voltage generator  2290  that may set a threshold for a comparator  1953 . As such, a different threshold may be set depending on a desired FoV, similar to the first embodiment of  FIG. 19 . However, in contrast to the first embodiment, the threshold is not dynamically adjustable (e.g., not adjustable based on inputs from a controller) because the threshold is set by a fixed voltage chip  2291 . The voltage value of the voltage chip  2291  may be determined using a reference or lookup table that correlates a particular sensor (e.g., based on the sensor&#39;s commercial identifier) with a desired FoV for the sensor. The voltage value of the determined voltage chip  2291  is such that, when coupled to the reference voltage generator  2290 , sets a threshold for the comparator  1953  that would achieve an effective FoV for the motion sensing device  2200  substantially equivalent to the desired FoV. The determined voltage chip  2291  may be a single voltage chip, or may be multiple voltage chips. A particular advantage of the fourth embodiment is that the FoV of the motion sensing device  2200  may be controlled without use of software or firmware, which may be preferred for especially simple motion sensing devices. 
       FIG. 23  is a flow chart illustrating an example method  2300  of controlling a field of view of a motion sensing device. In some embodiments, the method  2300  may be performed by any of motion sensing devices  1800 ,  1900 ,  2000 ,  2100 , or  2200 . 
     The method  2300  may include, at block  2310 , adapting a field of view of a motion sensing device about a primary sensing axis of the motion sensing device. The motion sensing device may include a passive infrared (PIR) sensor, and adapting the field of view may include controlling a detection sensitivity of the PIR sensor. Controlling the detection sensitivity may mean that some motion that would not be registered as detected motion by a motion sensing device with standard (or fixed) detection sensitivity may be registered based on the controlled sensitivity, or that some motion that would be registered as detected motion by a motion sensing device with standard (or fixed) detection sensitivity may not be registered based on the controlled sensitivity. 
     In a first embodiment, the sensitivity may be controlled by setting a threshold of a comparator to which the output from the PIR sensor is compared. Because motion is registered as detected motion based on the threshold, by setting a different threshold, the set of motions that are registered as detected may be changed. The threshold may be set by adjusting a resistance value of one or more programmable resistors in a digital potentiometer that is communicatively coupled the comparator, or may be set based on a signal received from an external controller. In a second embodiment, the detection sensitivity may be controlled by altering a gain or amplification applied to the output of the PIR sensor. By affecting the signal that is compared against the comparator&#39;s threshold, the set of motions that are registered as detected may similarly be changed. Altering the gain or amplification may be accomplished via the inclusion of one or more programmable resistors in the amplifier stage of existing control circuitry. 
     The method  2300  may further include, at block  2320 , monitoring for motion within the field of view. When the PIR sensor receives infrared radiation from a heat source moving through a FoV of the PIR sensor, the PIR sensor may produce an output signal with a voltage indicative of the received radiation. This signal may be processed and filtered through one or more amplifier stages, and may be received by a comparator. As discussed above with reference to block  2310 , the amplifier stage(s) may be altered by the inclusion of one or more programmable resistors. 
     The method  2300  may further include, at block  2330 , generating an output signal, from the comparator, based on a comparison of the filtered output signal to a threshold voltage value. The output signal here may be received by and selectively acted upon by a controller. As discussed above with reference to block  2310 , this process may be altered or affected to, essentially, change which output signals from the PIR sensor are acted upon by the controller (e.g., which signals are treated by the controller as detected motion). For example, the threshold voltage used in the comparison may be affected through the inclusion of one or more programmable resistors in a resistor divider network coupled to the comparator, may be set through one or more programmable resistors in the amplifier stage that alter a gain or amplification applied to the output of the PIR sensor, or may be set through the use of one or more fixed voltage chips. 
       FIG. 24  is a flow chart illustrating an example method  2400  of manufacturing a motion sensing device. In some embodiments, the method  2400  may be performed in connection with any of motion sensing devices  1800 ,  1900 ,  2000 ,  2100 , or  2200 . 
     The method  2400  may include, at block  2410 , providing a passive infrared (PIR) sensor for the motion sensing device. This PIR sensor may be an analog PIR sensor, such that an output signal from the PIR sensor is an analog signal. 
     The method  2400  may further include, at block  2420 , selecting a reference voltage generator based on a desired voltage. The reference voltage generator may include one or more voltage chips that provide a fixed amount of voltage, and may operate as a threshold voltage source for a comparator. The desired voltage may be based on a desired FoV for the motion sensing device, as different voltage values for the threshold voltage result in different detection sensitivities (and therefore FoV) for the motion sensing device. For each model or brand of PIR sensor, a desired FoV may be associated with a voltage value, such that the desired voltage for the reference voltage generator may be determined from a lookup table or reference table that associates a model of PIR sensor with various FoV. The model of sensor may be identified using a stock-keeping unit (SKU) associated with the product. 
     In some alternative embodiments, the threshold voltage source may include a resistor divider network with one or more programmable resistors that may be configured to change or have variable resistance in response to input from a controller. By changing the resistance value of the programmable resistor(s), the voltage provided by the resistor divider network may be increased or decreased. 
     The method may further include, at block  2430 , coupling the comparator to the PIR sensor and to the threshold voltage source. A first input of the comparator may be coupled to the PIR sensor to receive the output signal from the PIR sensor, and a second input of the comparator may be coupled to the threshold voltage source to receive the amount of voltage that sets the threshold value to which the output signal may be compared. Based on a comparison of the output signal to the threshold value, the comparator may be configured to output a comparison signal indicative of motion detected. 
     Embodiments of the present disclosure are directed to enabling electrical control over the field of view of a passive infrared sensor. Such embodiments may provide for motion sensing devices that can be deployed and adapted to a wider variety of locations and/or used in a wider variety of roles than traditional motion sensing devices having a static field of view. 
     Particular embodiments of the present disclosure include a method implemented in a motion sensing device. The method comprises adapting a field of view around a primary sensing axis of the motion sensing device by electrically controlling a detection sensitivity of a passive infrared sensor of the motion sensing device. The method further comprises, responsive to adapting the field of view, monitoring for motion within the field of view using the passive infrared sensor. 
     In some embodiments, electrically controlling the detection sensitivity may comprise setting a threshold for comparison to an electrical output of the passive infrared sensor. In some such embodiments, setting a threshold may comprise setting a resistance of a programmable resistor in a digital potentiometer that is communicatively coupled to the comparator. In some such embodiments, setting the threshold may comprise sending a digital signal indicative of a desired threshold, converting the digital signal to an analog signal, and inputting the analog signal to a comparator for comparison with the output of the passive infrared sensor. 
     In some embodiments, electrically controlling the detection sensitivity may comprise altering a gain of a circuit portion coupled to an output of the passive infrared sensor. In some such embodiments, altering the gain of the circuit portion may comprise setting a resistance of a programmable resistor within the circuit portion. 
     In some embodiments, the method may further comprise detecting motion within the field of view and generating an output signal indicating that the motion is detected. In some such embodiments, the output signal may be an analog signal. Other embodiments of the present disclosure include a motion sensing device. The motion sensing device may comprise a passive infrared sensor, and control circuitry communicatively coupled to the passive infrared sensor. The control circuitry is configured to adapt a field of view around a primary sensing axis of the motion sensing device by electrically controlling a detection sensitivity of the passive infrared sensor. The control circuitry may be further configured to, responsive to adapting the field of view, monitor for motion within the field of view using the passive infrared sensor. In some embodiments, the passive infrared sensor may be an analog sensor, and an output of the passive infrared sensor may be an analog signal. 
     In some embodiments, the control circuitry further may comprise a programmable resistor and a controller communicatively coupled to the programmable resistor. 
     In some such embodiments, the control circuitry may further comprise a comparator coupled to an output of the passive infrared sensor, and an output of the comparator may be indicative of motion within the field of view. The programmable resistor may be electrically coupled with the comparator to set a comparison threshold of the comparator. In some such embodiments, the programmable resistor may be in a resistor network electrically coupled to the comparator. 
     In some such embodiments, the control circuitry may further comprise an amplifier circuit portion configured to receive an output of the passive infrared sensor. A resistance of the programmable resistor may set a gain of the amplifier circuit portion. In some such embodiments, the amplifier circuit portion may comprise a first amplifier stage and a second amplifier stage. The programmable resistor may comprise two programmable resistors, and each of the first amplifier stage and the second amplifier stage may comprise one of these programmable resistors. 
     In some embodiments, the control circuitry may further comprise a controller, a comparator coupled to an output of the passive infrared sensor, and a digital-to-analog convertor. The convertor may be configured to receive, from the controller, a signal indicative of a desired threshold for the comparator and to output, to the comparator, a converted signal based on the received signal. An output of the comparator may be indicative of motion within the field of view. 
     In some embodiments, the control circuitry may further comprise a digital potentiometer electrically coupled to the controller. One or more programmable resistors may be located in the digital potentiometer. 
     Other embodiments of the present disclosure include a method of manufacturing a motion sensing device. In particular, the method may comprise providing a passive infrared sensor, and electrically coupling a first input of a comparator to an output of the passive infrared sensor and a second input of the comparator to a threshold voltage source. An output of the comparator may be indicative of motion within a field of view of the passive infrared sensor. 
     In some embodiments, the threshold voltage source may comprise a circuit portion comprising a programmable resistor and a controller electrically coupled to the programmable resistor to set the resistance of the programmable resistor. 
     In some embodiments, the method may further comprise selecting a reference voltage generator of a desired voltage from among a plurality of reference voltage generators of different voltages. The threshold voltage source may comprise the reference voltage generator. 
     Of course, those skilled in the art will appreciate that the present embodiments are not limited to the above contexts or examples, and will recognize additional features and advantages upon reading the following detailed description and upon viewing the accompanying drawings. 
     Aspects of the present disclosure may, of course, be carried out in other ways than those specifically set forth herein without departing from the spirit and scope of the disclosure. The present embodiments are to be considered in all respects as illustrative and not restrictive, and all changes that are within the meaning, or equivalent to, that which is recited in the appended claims are intended to be embraced therein. Although steps of various processes or methods described herein may be shown and described as being in a particular sequence or temporal order, the steps of any such processes or methods are not limited to being carried out in any particular sequence or order, absent an indication otherwise. Indeed, the steps in such processes or methods generally may be carried out in various different sequences and orders while still falling within the spirit and scope of the present disclosure.