Abstract:
This document discloses a camera assembly and a method for driving an illumination assembly of the camera assembly. The camera assembly comprises a digital camera, a power source including a battery and a super capacitor, and an illumination element powered by the power source. A first converter (e.g., a DC/DC SEPIC converter) charges the super capacitor from the battery and a second converter (e.g., a DC/DC boost converter) has a voltage input connected to the power source and a voltage output connected to the illumination element. A controller is programmed to control whether the illumination element is powered by the battery, the super capacitor, or both. The super capacitor is used to drive the illumination assembly at a high power level (e.g., when taking a still image), and the battery is used to drive the illumination assembly at a low power level (e.g., when taking a video).

Description:
BACKGROUND 
     The present invention relates generally to scouting cameras, which are cameras used to capture activity in a remote location without the presence of a user. More specifically, the invention relates to flash electronics for such scouting cameras. 
     Scouting cameras are often used by hunters to determine the amount of animal activity at a remote location. In order to monitor activity in dark conditions, scouting cameras are often equipped with an illumination assembly having illumination elements (e.g., xenon bulbs or LEDs). These illumination elements can be used to provide a flash (e.g., when taking a picture) or sustained illumination (e.g., when taking a video). 
     Because they are commonly used in remote locations, scouting cameras typically utilize batteries to power the camera and illumination assembly. Commonly available batteries, such as lithium ion (Li-ion) or alkaline batteries, often used in such an application are limited in their voltage capacities and are often incapable of withstanding the high current requirements for driving the illumination assembly. In addition, the battery life is reduced when the batteries are subjected to large spikes in current drawn in order to provide a high power flash. 
     When using a motion-activated scouting camera, it is often necessary to provide an initial high power flash to achieve a quality photograph followed by a subsequent low power illumination for taking video. In these situations, the batteries frequently are not able to source the current needed for the initial high power flash, and the variations, or spikes, in the current drawn from the battery reduces the life of the battery. 
     SUMMARY 
     The present invention provides a camera assembly and a method for driving an illumination assembly of a camera. The camera assembly comprises a digital camera (e.g., a motion-activated scouting camera), a power source including a battery and a super capacitor, and an illumination element (e.g., an LED) powered by the power source. A first converter (e.g., a DC/DC SEPIC converter) is operable to charge the super capacitor from the battery and has a voltage input connected to the battery and a voltage output connected to the super capacitor. A second converter (e.g., a DC/DC boost converter) has a voltage input connected to the power source and a voltage output connected to the illumination element. The camera assembly further includes a controller programmed to control whether the illumination element is powered by the battery, the super capacitor, or both, and further programmed to control the first converter and the second converter. In one embodiment, the controller measures the voltage of the super capacitor as feedback to control the first converter. Preferably, the power source further includes a load switch controllable by the controller to selectively connect the battery or super capacitor to the second converter. 
     The method comprises providing a camera assembly as broadly described above, charging the super capacitor with the battery, driving the illumination assembly at a high power level using the super capacitor, and driving the illumination assembly at a low power level using the battery. In one embodiment, the camera is capable of taking photographs and video. In this embodiment, driving the illumination assembly at a high power level is performed substantially simultaneously with taking a still photograph by the camera, and driving the illumination assembly at a low power level is performed substantially simultaneously with taking a video by the camera. When both still images and video are desired, driving the illumination assembly at a high power level is performed immediately before driving the illumination assembly at a low power level. Preferably, charging the super capacitor includes passing a current from the battery through a DC/DC SEPIC converter (e.g., using the super capacitor voltage as feedback to control the DC/DC SEPIC converter). 
     Other aspects of the invention will become apparent by consideration of the detailed description and accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a front view of a scouting camera assembly including a camera and an illumination assembly and circuit assembly embodying the invention. 
         FIG. 2  is a rear view of the camera assembly of  FIG. 1 . 
         FIG. 3  is a side view of the camera assembly of  FIG. 1 . 
         FIG. 4  is a schematic view of an electric circuit utilized in the camera assembly of  FIG. 1 . 
     
    
    
     Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. 
     DETAILED DESCRIPTION 
       FIGS. 1-3  illustrate a wildlife surveillance system, or camera assembly  10  that can be attached to a mounting structure (e.g., a tree, a post, etc.). The camera assembly  10  includes a housing  15  that supports a camera  20 , a detector  25 , an illumination assembly  30 , a power module  35 , and a control unit  40  for taking pictures and/or video (described collectively as media) of subjects (e.g., wildlife). As shown in  FIG. 3 , the illustrated housing  15  is defined by split-housing portions  45   a ,  45   b , that are attached to each other (e.g., using fasteners  50  or adhesive) to enclose the camera  20 , the detector  25 , the illumination assembly  30 , the power module  35 , the control unit  40 , and other components of the camera assembly  10 . With reference to  FIG. 1 , the housing  15  has transparent windows  55  so that the camera  20 , the illumination assembly  30 , and the detector  25  are protected from the environment while also providing exposure (i.e., a clear line of sight) for the camera  20 , the illumination assembly  30 , and the detector  25 . 
     The camera  20  includes an image-capturing device  60  (e.g., a digital receiver) that has a still image mode, for obtaining still images of subjects, and a video image mode for obtaining video images of subjects. In some constructions, the camera  20  also can include a hybrid or multi-image mode for obtaining still and video images of subjects (e.g., consecutively or at timed intervals). Each of the still image mode, the video image mode, and the hybrid image mode defines an operating parameter of the camera  20  that impacts how the subject is illuminated, as described in detail below. 
     The illustrated detector  25  includes a sensor, such as a passive infrared (“PIR”) sensor  65 , and a lens  70  (e.g., a Fresnel lens). The sensor  65  detects a subject and outputs a signal to the control unit  40  in response to detection of the subject. The lens  70  defines a field of view of the detector  25  and focuses the subject in the field of view onto the sensor  65 . 
     The power module  35  is provided to power components of the camera assembly  10  and to facilitate downloading media stored in the camera  20 . With reference to  FIG. 4 , the power module  35  includes at least one battery  75  (e.g., a lithium-ion battery, an alkaline battery, etc.) provided in series or parallel when multiple batteries are present. Many configurations of batteries or battery packs are contemplated, including eight AA battery cells configured as two strings of four cells. The power module  35  further includes a least one electrical double-layer capacitor, or super-capacitor  80 . Super-capacitors, also known as ultra-capacitors or electric double layer capacitors (“EDLC”), have capacitance values that were previously unavailable in a single conventional capacitor, and super-capacitors are able to provide relatively high current pulses when compared to conventional capacitors or batteries. The illustrated super-capacitors  80  are provided and arranged in series. The stored energy in the batteries  75  can be transferred to the super-capacitors  80  by the use of a first DC/DC converter in the form of a single-ended primary inductance converter (“SEPIC”)  85 . The SEPIC converter  85  has a voltage input  90  and a voltage output  95 , although it will be appreciated that any DC/DC converter with a modulation index (i.e. the ratio of output voltage to input voltage) ranging from zero to greater than one can be utilized. The SEPIC converter  85  is operable to either decrease or increase the value of the input voltage  90  at the output  95 . The components of the SEPIC converter  85  are well known to one with ordinary skill in the art and include an input capacitor  100 , an output capacitor  105 , an input inductor  110 , an output inductor  115 , a first switch  120  (e.g., a MOSFET), a second switch  125  (e.g., a diode), and a middle capacitor  130 . The input capacitor  100  is coupled in parallel to the batteries  75  such that the SEPIC converter input  90  is substantially equivalent at steady state to the battery  75  voltage. The MOSFET  120  is controllable via a gate signal input  135  provided by the control unit  40 . The output capacitor  105  is coupled in parallel to the super-capacitors  80  such that the SEPIC converter output  95  is substantially equivalent at steady state to the super-capacitor  80  voltage. The power module  35  further includes load switches  140  separating the batteries  75  and the super-capacitors  80  from the illumination assembly  30 . The load switches  140  are controllable to selectively connect the batteries  75 , the super-capacitors  80 , both, or neither to the illumination assembly  30 . 
     The illumination assembly  30  is capable of illuminating a subject in at least two power levels of illuminating light when the camera  20  is capturing media. With reference to  FIG. 1 , the illustrated illumination assembly  30  includes a light source  145  that has illumination elements  150  (e.g., light emitting diodes “LEDs”). The light source  145  includes multiple LEDs  150  electrically connectable in a plurality of configurations. The illustrated light source  145  includes a plurality of LEDs coupled in series to form a string, with a plurality of strings coupled in parallel. The light source  145  is electrically connected to the power module  35  through the use of a second DC/DC converter in the form of a boost converter  155  having a voltage input  160  and a voltage output  165 , although it will be appreciated that other DC/DC converters with a modulation index (i.e. the ratio of output voltage to input voltage) greater than one can be utilized. The boost converter  155  is operable to increase the value of the input voltage  160  at the output  165 . The components of the boost converter  155  are well known to one with ordinary skill in the art and include an input capacitor  170 , an output capacitor  175 , an inductor  180 , a first switch  185  (e.g., a MOSFET), and a second switch  190  (e.g., a diode). By controlling the switch  185 , the voltage is controlled from input  160  to output  165 . The position of the load switches  140  can be changed in order to connect the input capacitor  170  in parallel with the batteries  75 , the super-capacitors  80 , both, or neither, as desired. The MOSFET  185  of the boost converter  155  is controllable via a gate signal input  195  provided by the control unit  40 . The output capacitor  175  is coupled in parallel to the light source  145  such that the boost converter output  165  provides a voltage to drive the LEDs  150 . 
     Referring to  FIG. 2 , the housing  15  supports a user interface  200  for controlling the camera assembly  10  and determining the state of the camera assembly  10 . The user interface  200  is disposed along the rear side of the camera assembly  10  and has a selector switch  205 , button switches  210 , a rotary dial  215 , and a display  220 . The selector switch  205  is a three-position toggle that controls the camera mode (e.g., still image mode, video image mode, and hybrid image mode). The button switches  210  and the rotary dial  215  can be manipulated by the user to control the camera assembly  10 , and to obtain information regarding the state of the camera assembly  10  (e.g., adjusting the programmable settings of the camera assembly  10  such as the time interval between images, the time of day, etc.). The settings and the information associated with the camera assembly  10  can be viewed on the display  220 . The camera assembly  10  also includes electrical and/or electronic connections (e.g., a USB port  225 , a media storage port  230 , etc.) to facilitate storage and retrieval of media from the camera assembly  10 . As illustrated, a cover  235  is pivotally coupled to the housing  15  to enclose the user interface  200  and the electronic connections (e.g., to protect the user interface  200  from debris, water, sunlight, rain, etc.) when not in use. A fastener  240  secures the cover  235  to the housing  15 . As will be appreciated, the camera assembly  10  can include other components (e.g., additional sensors, not specifically discussed herein). 
     With reference to  FIGS. 1 ,  2  and  4 , the control unit  40  is disposed in the housing  15  and is in communication with the camera  20 , the detector  25 , the illumination assembly  30 , the power module  35 , and the user interface  200  to control the camera assembly  10 . In addition to the control unit  40  controlling the switches  120 ,  185  of the converters  85 ,  155  via the gate signals  135 ,  195 , respectively, the control unit  40  also takes voltage measurements  245  from both the illumination assembly  30  and the power module  35  to provide feedback. As shown in  FIG. 4 , the illustrated measurements can be taken at the SEPIC converter input  90  (which is the same as the battery  75  voltage), and the SEPIC converter output  95  (which is the same as the super-capacitor  80  voltage) in order to monitor the charging of the super-capacitors. It will be appreciated by one of ordinary skill in the art that the measurements  245  taken for feedback to control the SEPIC converter  85  eliminate the conventional current measurements typically needed to adequately control the charging of capacitors or batteries. It will also be appreciated by one of ordinary skill in the art that the SEPIC converter  85  can be controlled by the control unit  40  to operate in constant current mode (CCM) short durations or discontinuous current mode (DCM) when charging the super-capacitors  80 . In addition, a voltage measurement  245  is taken in the illumination assembly after the array of LEDs  150 . This voltage measurement can be utilized as a measure of the power, and subsequent illumination, being provided by the light source  145 . 
     In operation, the detector  25  triggers the camera  20  to take a picture, start a video, or both (e.g., consecutively or with staggered starts), when the sensor  65  detects and responds to infrared light (or a change in infrared light) or motion within the field of view of the detector  25 . 
     More specifically, the control unit  40  receives information from the sensor  65  and is programmed to actuate the camera  20  when the subject is within the field of view. In response to the signal from the sensor  65 , the control unit  40  automatically configures the illumination assembly  30  and power module  35  as needed to illuminate the subject. That is, the control unit  40  controls the illumination assembly  30  and power module  35  so that the light source  145  is providing enough illumination for a high quality picture or video without drastically draining the battery  75  or super-capacitor  80  power. 
     The control unit  40  determines the camera mode from the selector switch  205  and automatically configures the camera assembly  10  to use the super-capacitors  80 , the batteries  75 , or both based on the camera mode. In the still image mode, the subject is illuminated using the super-capacitors  80  to drive the light source  145  for a brief period of time (e.g., approximately 0.25 seconds) while the camera captures a still image of the subject. With the super-capacitors  80  charged, the LEDs  150  are driven at a high current provided by the super-capacitors  80 , thus producing a high quality image. If only a still photograph is taken by the camera  20 , the control unit  40  recharges the super capacitors  80  by utilizing the battery  75  voltage through the SEPIC converter  85 . In addition, by supplying the high power flash for the photograph with the super-capacitors  80 , the batteries  75  are saved from having to supply the damaging current pulses characteristic of a photograph flash. 
     In the video image mode, the subject must be illuminated over a longer timeframe to adequately capture a video image of the subject. In this mode, the control unit  40  uses the batteries  75  to provide a longer duration of illumination at a low power level. The control unit  40  allows the LEDs  150  to be driven at a lower current provided by the batteries  75  for the duration of the video (usually at least  10  seconds in length), drastically saving the life of the batteries  75  had they been driven at the high power level provided for the photograph flash. 
     In the hybrid image mode, the control unit  40  illuminates the subject using the super-capacitors  80  for capturing the still image, and subsequently illuminates the subject using the batteries  75  to capture the video image. The control unit  40  is able to dynamically communicate with the illumination assembly  30  and power module  35  in order to consecutively capture a still image with a high power flash and a video image with low power illumination by controlling the load switches  140 . 
     Various features and advantages of the invention are set forth in the following claims.