Radiant energy – Photocells; circuits and apparatus – Photocell controlled circuit
Reexamination Certificate
2002-08-20
2004-07-27
Le, Que T. (Department: 2878)
Radiant energy
Photocells; circuits and apparatus
Photocell controlled circuit
C250S225000
Reexamination Certificate
active
06768094
ABSTRACT:
BACKGROUND OF THE INVENTION
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.
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.
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.
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.
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.
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.
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
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.
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.
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.
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.
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.
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.
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.
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.
REFERENCES:
patent: 3676671 (1972-07-01), Sheldon
Kelly Lowry & Kelley LLP
Le Que T.
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