Abstract:
A trigger system including a photosensor having a polarizing light filter n positioned in a light receiving end of a housing. A lens is disposed in the housing for focusing light onto a transducer. A switch is electronically coupled to the transducer for selecting either a passive or active mode. In the active mode, a light source is directed at the photosensor, whereby a trigger signal is generated when an object disrupts the received light. In the passive mode, an opaque screen is spaced from the photosensor and a source of light is directed at the opaque screen, whereby a trigger signal is generated from the light reflected from an object positioned between the screen and photosensor. The trigger system may be electronically linked to a photographic system for high speed or action photography.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    The present invention generally relates to trigger systems, such as those used in action and high speed photography and the like. More particularly, the present invention relates to a photo-voltaic trigger system operable in either a passive or active mode.  
           [0002]    Light-activated trigger systems are well-known in the prior art and often used in security applications in which a laser beam or infrared beam is sent between a transmitter and a receiver. Once an object disrupts the beam, the receiver detects the absence of light and generates a signal, typically in the form of an alarm or the like.  
           [0003]    Similar devices are used in the high speed and action photography industry. A light beam is sent between a transmitter and receiver, or the light beam is reflected between the transmitter/receiver and a reflector. Once an object, such as a flying bullet, running animal, skier, etc. passes through the beam, photographic equipment is activated to nearly instantaneously take a picture or video footage of the event. Similar results can be achieved using sensors to detect motion or sound.  
           [0004]    However, all of the currently offered trigger systems have drawbacks. Many such systems require an electronic receiver which must be aligned with the transmitter. Aside from the difficulty of alignment, the system can be expensive as the user must purchase both a transmitter and a receiver. Other systems use a reflector aligned with the transmitter, which also serves as a receiver of the reflected beam of light. However, such systems have been found to be very difficult to set up and operate. This is particularly the case in outdoor or other unconventional settings in which the reflector and transmitter must be attached to trees, tripods, etc. and aligned with one another. Such systems are not able to be used in certain settings due to the arrangement of transmitter and receiver or reflector. For example, when photographing a bicycle race taking place on a highway, such tripods bearing the receiver or reflector cannot be placed in the road as oncoming automobiles can hit such tripods or supporting structures. Placing the transmitter on one side of the highway with the receiver or reflector on the opposite side of the highway will generate photos activated by passing cars as well as bicyclists.  
           [0005]    Another disadvantage of such prior art systems is that many utilize a sharp, coherent light beam, such as a laser beam. It is well known that such intense beams of light can actually be harmful to the eyes of humans and animals.  
           [0006]    Another disadvantage of such prior art systems is that they are all in a continuously active state. That is, the sound or light beam is continuously sent between the transmitter and receiver or reflector. The beam of sound or light must be disrupted before the trigger system is activated. This can require a tremendous amount of power. When filming or photographing a prolonged event, such as a marathon or other such similar event, access to a power source such as a generator may be required. In the event an electrical outlet is unavailable, a generator is unavailable, or a generator is undesirable, such as when filming wildlife, the photographer must transport back-up batteries in the event the initial batteries are exhausted.  
           [0007]    Accordingly, there is a continuing need for a trigger system which overcomes the disadvantages of the prior art. Such a trigger system should be relatively easy to set up and operate. Such a system should be capable of operating in a passive, non-power consuming mode. In an active mode, such a trigger system should not utilize a light beam which is potentially harmful. The present invention fulfills these needs and provides other related advantages.  
         SUMMARY OF THE INVENTION  
         [0008]    The present invention resides in a photo-voltaic trigger system. The system generally comprises a photosensor having a light-impermeable housing. A polarizing light filter is positioned in a light-receiving end of the housing. A lens is disposed in the housing for focusing received light onto a transducer.  
           [0009]    In one preferred embodiment, the photosensor is directed towards an opaque screen. A source of light, which may comprise ambient light or an artificial light source in the visible or invisible spectrum, is at least partially directed at the screen. When an object enters the space between the screen and the photosensor, light is reflected off of the object and into the photosensor such that the transducer generates a trigger signal.  
           [0010]    The light source may comprise an array of light emitting diodes. The array includes a plurality of groups of light emitting diodes which are powered in a predetermined sequence. Preferably, each group of light emitting diodes is oriented to direct light at a different angle with respect to the photosensor so that objects at varying distances from the photosensor may be detected.  
           [0011]    In a particularly preferred embodiment, the trigger system includes a switch electronically coupled to the transducer for selecting either the aforementioned passive mode, or an active mode. Thus, a trigger signal is generated in the passive mode when light is reflected into the photosensor from the object. However, in the active mode, a light source is directed at the photosensor. The light source preferably comprises a non-coherent light source which may be on either the visible or invisible light spectrum. The trigger signal is generated when an object disrupts this received light.  
           [0012]    In either the passive or active mode, a plurality of photosensors may be spaced apart from one another, and in the passive mode positioned generally opposite one or more opaque screens, each photosensor being electronically linked to a device for determining a variable of the object, such as location, distance, speed, etc.  
           [0013]    A particularly preferred application of the trigger system of the present invention is electronically linking the photosensor to a photographic system. For example, the photosensor may be linked to a camera of a photographic system which is focused on the space between the photosensor and the screen. Once the object enters the space between the screen and the photosensor, a trigger signal is sent to the camera to activate it. Flash devices may be coupled with the camera and also activated by the trigger signal.  
           [0014]    For ease of alignment and use, an alignment device may be attached to the housing of the photosensor, and the photosensor housing is preferably configured for attachment to a tripod or the like.  
           [0015]    Other features and advantages of the present invention will become apparent from the following more detailed description, taken in conjunction with the accompanying drawings, which illustrate, by way of example, the principles of the invention. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0016]    The accompanying drawings illustrate the invention. In such drawings:  
         [0017]    [0017]FIG. 1 is a perspective view of a photosensor used in accordance with the present invention;  
         [0018]    [0018]FIG. 2 is a partial cross-sectional view taken generally along line  2 - 2  of FIG. 1, illustrating components of the photosensor;  
         [0019]    [0019]FIG. 3 is a fragmented cross-sectional view of the photosensor, illustrating key components thereof;  
         [0020]    [0020]FIG. 4 is an end view of the photosensor taken generally along line  4 - 4  of FIG. 2;  
         [0021]    [0021]FIG. 5 is a front end view of the photosensor taken generally along  5 - 5  of FIG. 2;  
         [0022]    [0022]FIG. 6 is an electronic schematic of a transducer/trigger circuit used in accordance with the present invention;  
         [0023]    [0023]FIG. 7 is a schematic view of a photosensor directed at an opaque screen in a passive mode in accordance with the present invention;  
         [0024]    [0024]FIG. 8 is another schematic view of a photosensor directed at an opaque screen placed on the ground;  
         [0025]    [0025]FIG. 9 is a schematic view illustrating the use of an array of light emitting diodes in a passive mode in accordance with the present invention;  
         [0026]    [0026]FIG. 10 is a schematic view of the invention in an active mode;  
         [0027]    [0027]FIG. 11 is a schematic view of the invention as used in a foot race;  
         [0028]    [0028]FIG. 12 is a schematic view of the invention in use in wildlife action photography;  
         [0029]    [0029]FIG. 13 is a schematic view of the invention in use with a bicycle race for seating along a highway; and  
         [0030]    [0030]FIG. 14 is another schematic view of the present invention incorporating multiple photosensors in use in a high-speed race. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0031]    As shown in the drawings for purposes of illustration, the present invention is directed to a photo-voltaic trigger system which is operable in either a passive or active mode, as will be more fully described herein. The system of the present invention is versatile in its use, relatively easy to set-up, and easily operable. As will be seen from the following description, the system of the present invention is uncomplicated in construction and relatively inexpensive. Although the system of the present invention will be described herein in a preferred application of action or speed photography, it should be understood by the reader that the system of the present invention can be used in other applications as well, such as security systems, garage door safety systems, etc.  
         [0032]    With reference now to FIGS.  1 - 5 , a photosensor  10  used in accordance with the present invention is illustrated. The photosensor  10  comprises an elongated tubular housing  12  which is comprised of a light impermeable material, or otherwise coated so as to be light impermeable. A first end  14  of the housing  12  is open for reception of a light polarizing filter  16 . As illustrated, the open end includes internal threads  18  for screw-on attachment of the polarizing filter  16 . The light polarizing filter  16  serves to filter incoming light and direct the light at a generally transverse access to the filter  16  such that the light travels generally in a straight line through the housing, as illustrated.  
         [0033]    A lens  20 , such as the illustrated convex lens, is mounted within the housing  12  at a distance from the polarizing light filter  16 . The lens  20  serves to focus the incoming light  22  onto a transducer  24 . The transducer  24  comprises a photo transistor, such as a NPN Photo Transistor PN158, or the equivalent. As illustrated in FIGS. 2 and 3, the transducer  24  may be mounted on an interior wall  26  within the housing  12  to assure that the transducer  24  remains in a fixed location with respect to the lens  20  such that the light  22  entering the housing  12  will be focused upon the transducer  24 . The transducer  24  is electronically coupled with a circuit  28  which, in a preferred embodiment, can be moved into the active or passive mode utilizing a switch  30 .  
         [0034]    With reference now to FIG. 6, the circuit  28  is illustrated containing the photo transistor transducer  24 . The circuit  28  includes connection to a power source  32 , such as a battery supporting a three volt input. A resistor  34 , such as a 10 K Ohm resistor is in the electrical path between the power source  32  and the switch  30 . The switch  30  comprises a DPDT switch such that it can be moved between two positions to power or connect different portions of the circuit  28 . The circuit  28  is illustrated in the passive or “no light” operation. That is, as will be described more fully herein, light is not actively directed into the photosensor  10 . When light is reflected into the photosensor  10 , as will be described more fully herein, the photo transistor  24  activates. It will be noted that the photo transistor is directly connected to the trigger output, such as by electrical or radio frequency connection to a camera. In order to activate the trigger or switch of a camera, the camera must be brought to a very low voltage or grounded. The activation of the photo transistor transducer  24  causes the transducer  24  to ground, or substantially lower the voltage, of the camera, causing it to begin filming or open its shutter and expose film in order to take a still photograph.  
         [0035]    It will be noted by those skilled in the art that the photo transistor  24  in this mode is not powered by the power source  32 . Thus, while operating in this passive “no light” operation or mode, the photosensor  10  utilizes no external power. This can be extremely advantageous in applications where the photosensor  10  is used for a prolonged period of time, such as security applications, safety applications, and action and high-speed photography where pictures are taken over a prolonged time period, or a prolonged time period passes before the opportunity for a picture, such as an animal, is presented.  
         [0036]    With continuing reference to FIG. 6, in the active mode or “light” operation, light is directed through the filter  16  and onto the transducer  24  continuously. The contact points of the switch are moved so that the photo transistor  24  is connected to the power supply  32 . Due to the constant activation of the photo transistor  24 , its collector remains at ground, pulling the base of the now connected signal transistor  36  to ground. Thus, the output device, such as the camera, remains at the threshold voltage. Any disruption of the light source will cause the photo transistor  24  collector to elevate to three volts, the voltage supplied by the power supply  32 , causing the base of the signal transistor  36  to also elevate to 3 volts. So long as the base of the signal transistor illustrated rises above 0.7 volts, the collector of the signal transistor is pulled from 3 volts to ground. This causes the camera, or other attached device, to go to ground as well, thus triggering the camera or connected electronic device.  
         [0037]    The aforementioned events are collectively referred to in this application as the creation of a trigger signal. It will be appreciated by those skilled in the art that for different output electronic device applications, the circuit may be modified somewhat in order to trigger the electronic device. However, the circuit  28  should be movable between active and passive modes in order to generate a trigger signal either due to the detection of light in the passive mode, or the disruption of a light source in the active mode.  
         [0038]    Referring back to FIGS.  1 - 5 , in a particularly preferred embodiment, the photosensor housing  12  is attached to a mount  38  which includes an internally threaded recess  40  for attachment to a standard tripod or the like. The end of the housing  12  generally opposite the filter  16  includes a back wall  42  in which is positioned the switch  30  for easy access, as well as ports  44  and  46  for the insertion/connection of a power cord extending from the power source, and an electrical lead extending to either a radio frequency transmitter or the electrical lead attached to the end electronic device, such as the camera.  
         [0039]    The photosensor  10  preferably has an alignment device  48  associated therewith for properly aligning the filter  16 . The alignment device  48  can comprise any one of a number of alignment devices, such as rifle-type sights, a cross-hair sight, or the illustrated rifle-type scope. Such scopes  48  typically include cross-hairs  50 , as illustrated in FIGS. 4 and 5 which allow precise alignment of the photosensor  10 . The alignment device may be attached to the housing  12  of the photosensor  10  by mounting brackets or members  52 , tongue and groove connection, or any other connection suitable to securely attach the alignment device  48  to the housing  12 .  
         [0040]    With reference now to FIGS.  7 - 9 , the schematic drawings illustrate operation of the trigger system of the present invention in a passive mode. With reference to FIG. 7, the photosensor  10  is directed to an opaque screen  54 . The opaque screen may comprise a black felt screen, or any screen or object which is light absorbing or which otherwise does not reflect an appreciable amount of light. Black felt fabric is easy to mount under various circumstances. A light source, such as the illustrated ambient light from the sun  56  is at least partially directed onto the opaque screen  54 . It should be understood that the light source can comprise an artificial light source, such as a flood light which may be in the visible or invisible light spectrum. The orientation of the photosensor  10  and screen  54  can vary so as to be horizontally disposed from one another, as illustrated in FIG. 7, disposed at an angle as shown in FIG. 8, or any other orientation. The alignment device  48  associated with the photosensor  10  allows the photosensor  10  to be directly aimed at the opaque screen  54 , even at a distance. As described above, the photosensor  10  in this passive or “no light” mode does not require power. Once an object enters the space between the screen  54  and the photosensor  10 , the object reflects light from the light source  56  into the photosensor  10  which then triggers the camera or other electronic device, as described above.  
         [0041]    The use of back lighting as the light source is preferred, and sometimes necessary, due to variable sun light conditions such as shadows forming from clouds, surrounding objects, etc. However, due to the opaque, non-reflective nature of the screen  54  even a relatively bright flood light does not reflect sufficient light into the photosensor  10  to trigger it.  
         [0042]    In a particularly preferred embodiment illustrated in FIG. 9, the light source comprises a light emitting diode array  58 . Ultra bright LED&#39;s are available to provide very bright, pin point light sources that can be individually pointed along the photosensors center line towards the opaque screen  54 . These LED&#39;s can also be fired sequentially at less than 100% duty cycle, allowing additional light power during short time intervals. In a particularly preferred embodiment, the array includes groups of LED&#39;s which are energized in sequence for a short duration, such as {fraction (1/10,000)} seconds. For example, there may be an array of 30 LED&#39;s surrounding the photosensor  10  and facing towards the screen  54 . Groups of 3 LED&#39;s would be energized in sequence. One cycle to energize all 30 LED&#39;s would take only {fraction (1/1,000)} seconds. Only one group of 3 LED&#39;s would be energized at a time. Each group of 3 LED&#39;s would operate at 10% duty cycle. Each LED or group of LED&#39;s could be pointed at a different distance along the center line path between the photosensor  10  and the opaque screen  54 . Any object now entering between the photosensor  10  and the screen  54  would reflect at least one or more LED&#39;s light energy into the photosensor  10 , thus triggering it. The LED&#39;s could be directed or pointed at specific locations along the center line of the photosensor  10  in order to selectively trigger the photosensor  10  only on objects where the LED&#39;s are pointing. Conversely, the photosensor  10  in conjunction with the LED&#39;s pointing at different locations along the photosensors axis could be used to determine at what location between the photosensor  10  and the screen  54  an object triggered the photosensor  10 . Knowing where the object passed in relation to the photosensor  10  could be very useful. For example, such information could assist in focusing the camera at the correct place to capture the object triggering the photosensor  10 .  
         [0043]    Using the 30 LED array, with 10 groups of 3 LED&#39;s, each group could point two feet farther away from the photosensor  10  than the previous group of 3 LED&#39;s. Thus, if the photosensor were triggered within the first {fraction (1/10,000)} seconds, the object triggering the photosensor  10  would be within two feet of the photosensor. However, if the photosensor was triggered at approximately {fraction (5/10,000)} seconds, then the object triggering the photosensor would be approximately ten feet from the photosensor  10 . Using groups of 3 LED&#39;s is advantageous as each LED has a voltage drop of approximately 2 volts. This allows convenient use of readily available 6 volt batteries. Also, the 3 LED&#39;s energize need not be located adjacent to one another in the cluster, but preferably are spaced from one another, such as 1200 apart.  
         [0044]    With reference now to FIG. 10, a schematic drawing is shown illustrating the trigger system of the present invention in an active mode. That is, light from a light source  60  is directed into the photosensor  10 . So as not to cause vision damage, the light source  60  preferably comprises a non-coherent non-laser light source, such as a flashlight or the like. Once again, the alignment device  48  associated with the photosensor housing  12  enables the photosensor  10  to be aligned with the light source  60 . As described above, once the light source is disrupted by an object entering the space between the photosensor  10  and the light source  60 , the photosensor  10 , with the switch in the “active” mode, triggers the pertinent electronic device, such as a camera, alarm, etc.  
         [0045]    With reference now to FIGS.  11 - 14 , schematic drawings are provided illustrating the trigger system of the present invention in action or high-speed photography applications. With reference to FIG. 11, the photosensor  10  and screen  54  may be positioned opposite one another at a finish line  62  of a race. As runners  64  pass between the photosensor  10  and screen  54 , light from the light source  56  is reflected from the runner  64  into the photosensor  10 , thus triggering the passive photosensor and activating a camera  66  and flash device  68 . The camera  66  can be positioned at some distance from the photosensor  10  and controlled using radio frequency or hard wired electrical leads. The camera  66  can be placed at an angle so as to focus along the finish line  62  without actually being immediately in front of the finish line  62 . Utilizing the LED array  58 , as described above, allows the camera  66  to be automatically focused at the proper point of the finish line  62  where the runner  64  passes so that the photograph is in focus. Of course, the camera  66  can also comprise a video camera or the like so as to film video.  
         [0046]    With reference now to FIG. 12, the same set-up may be implemented in order to photograph an animal or the like, such as an animal traversing a path  72 . The light source  56  can comprise a flood light. In the event that the flood light is determined to frighten the animal, such as during night conditions, the flood light  56  may emit a non-visible stream of light, such as infrared light. Thus, the photograph or video may be taken of the animal  70  while the animal is in its natural habitat and under non-artificial circumstances. Simultaneously illustrated in FIG. 12 is the use of a light source  60  such as flashlight or the like directly aimed at what would be the active mode photosensor  10 . Once again, the light source  60  could be of a type which is invisible to the eye. Of course, either the screen  54  or light source  60  would be used, but not both simultaneously.  
         [0047]    With reference now to FIG. 13, utilization of the opaque screen  54  allows the screen to be placed upon the ground and the photosensor  10  to be directed downwardly onto the screen  54 , as shown in FIG. 8. This allows the screen  54  to be placed on the side of a highway. Thus, a bike race, for example, can be easily photographed automatically without fear of damaging equipment as the opaque screens  54  can be placed outside of the area of vehicle travel, or even if an automobile runs over the black felt screen  54 , no damage will be done. An additional benefit of the present invention is that in a bicycle race wherein participating bicyclists ride a loop, a bicyclist can be photographed on both sides of the highway with the set-up illustrated in FIG. 13. For example, bicyclists beginning to ascend a hill can be photographed using the trigger system of the present invention on one side of the street, and photographed on the opposite side of the street coming down the hill. The camera  66  may be positioned adjacent to one another so that the photographer can have access to both cameras for the replacement of film and the like. The camera  66  positioned across the highway can have a telephoto lens or the like focused upon the space between the screen  54  and the photosensor  10 . Flash devices  68  can be positioned closer to the photosensor  10  to provide the necessary light.  
         [0048]    With reference now to FIG. 14, multiple photosensors  10  can be used and spaced apart from one another in order to determine location of the objects, speed of the objects, etc. There is typically a delay of a fraction of a second upon triggering a camera to expose film and take a photograph. There is also a delay in video in order to bring the camera up to speed. Such time delays can be critical in high-speed situations such as motorcycle or automobile races. Using these examples, if an automobile or motorcycle  74  passes between a first photosensor  10  and screen  54 , the camera  66  can be activated so that it takes a proper picture or video footage at the finish line  62 . The speed of the bicycle  74  or auto  76  or motorcycle  78  can also be determined by measuring the time delay between the two triggered photosensors  10 .  
         [0049]    The trigger system of the present invention provides many benefits over the prior art. The photosensor  10  does not require any battery power when operated in the passive or “no light” mode. The system is simple and uncomplicated in construction and set-up. The system does not require harmful laser light, or a reflective surface or active light beam. The photosensor  10  can sense action selectively on a roadway so as to trigger only on bicycles and not passing cars. The system, due to its simplicity, is also relatively inexpensive.  
         [0050]    Although several embodiments have been described in detail for purposes of illustration, various modifications may be made without departing from the scope and spirit of the invention. Accordingly, the invention is not to be limited, except as by the appended claims.