Patent Application
20170167923
This application relates to security systems and more particular to security systems.
Systems are known to protect people and assets within secured areas. Such systems are typically based upon the use of one more sensors that detect threats within the areas.
Threats to people and assets may originate from any of number of different sources. For example, a fire may kill or injure occupants who have become trapped by a fire in a home. Similarly, carbon monoxide from a fire may kill people in their sleep.
Alternatively, an unauthorized intruder, such as a burglar, may present a threat to assets within the area. Intruders have also been known to injure or kill people living within the area.
In the case of intruders, sensors may be placed in different areas based upon the respective uses of those areas. For example, if people are present during some portions of a normal day and not at other times, then sensors may be placed along a periphery of the space to provide protection while the space is occupied while additional sensors may be placed within an interior of the space and used when the space is not occupied.
In most cases, threat detectors are connected to a local control panel. In the event of a threat detected via one of the sensors, the control panel may sound a local audible alarm. The control panel may also send a signal to a central monitoring station.
While conventional security systems work well, it is sometimes difficult to detect intruders in open areas within a building or where a room has a low ceiling. Accordingly, a need exists for better methods and apparatus for passively detecting intruders.
While disclosed embodiments can take many different forms, specific embodiments thereof are shown in the drawings and will be described herein in detail with the understanding that the present disclosure is to be considered as an exemplification of the principles thereof as well as the best mode of practicing same, and is not intended to limit the application or claims to the specific embodiment illustrated.
The sensors may be embodied in any of a number of different forms. For example, at least some of the sensors may be switches placed on the doors and/or windows providing entrance into and egress from the secured area. Other sensors may be passive infrared (PIR) sensor placed within the area to detect intruder who have been able to circumvent the sensors placed along the periphery of the secured area.
Also included within the system is a control panel 18 that monitors the sensors. Upon detecting the activation of one of the sensors, the control panel sends an alarm signal to a central monitoring station 20. The central monitoring station may respond by summoning the police.
Included within the control panel and each of the sensors may be one or more processor apparatus (processors) 22, 24 operating under control of one or more computer programs 26, 28 loaded from a non-transitory computer readable medium (memory) 30. As used herein, reference to a step performed by computer program is also reference to the processor that executed that step.
For example, one of the processor may be an alarm processor that monitors the sensors. Upon activation of one of the sensors, the alarm processor may compose an alarm message to be sent to the central monitoring station. The message may include an identifier of the alarm system (e.g., address, account number, etc.), an identifier of the type of sensor, a location within the secured area and the time.
Included within the PIR assembly may be a differential PIR device 56 and a mirror assembly 58. As shown, infrared energy 51 from an intruder 62 is reflected by the mirror assembly into the PIR device. In this regard, the mirror assembly significantly increases the lateral range of the PIR sensor assembly over conventional PIR detectors.
As may also be noted from
In general, each of the rings generally has the shape of an annulus with the reflective surface of the mirrors on an inside of the annulus. In the example shown in
Under one illustrated embodiment, the widths of the mirrors in the direction around the annulus may be gradually adjusted to improve the signal response. For example, the mirrors along the weak axis on opposing ends of the horizontal line shown in
As may be observed, graph P1 shows that the PIR device provides a negative-going pulse in response to the person crossing the maximum range threshold. This negative-going pulse shows the response of the negative PIR element where the positive PIR element has been masked by the window. Graphs P7-P10 show positive and negative portions of the pulse where the PIR elements is only partially masked.
In general, conventional PIR sensors are widely used in ceiling mounted motion detection. However, the requirement for 360 degree operation is a serious challenge for reliable operation based upon conventional technology. Because the PIR detection elements are not rotationally symmetric, there are significant differences in performance based upon the direction from which an intruder approaches the detector. For example, where the detection range is greater than 12 meters, there is clearly a strong and a weak axis in the detection capabilities of such devices. Because of the differences between the strong and weak axis, missed intruders are inevitable.
Past efforts to solve the problem of differences in signal strength have involved the use of multiple pyro element designs (e.g., 3 pyros, 4 pyros, etc.), so that each pyro detects only 120 degrees (3 pyros) or 90 degrees (4 pyros) instead of the 360 degrees required. However, multiple pyros involve designs requiring multiple optical components, circuits and mechanical support and such designs increase the cost and exacerbate the difficulty of compressing the size of such devices.
The PIR sensor assembly of
In general, the PIR assembly of
Model 2 (
Model 3 (
Model 1 has a strong zone (P1 to P4 and P13 to P16) and a weak zone (P7 to P11). Some walk points of model 1 provide almost no signal at all. The new design of model 3 improves the weak points, balances the maximum and minimums and provides the detector assembly with a more stable performance.
Model 3 provides 2 main benefits. By limiting the width of the window common mode effects are suppressed. The asymmetric mirror design eliminates the asymmetric signal response of the pyro element.
The pyro design of model 1 has a wide angle window. When wide angle windows are used in ceiling mounted PIR detector assemblies, the pyros' positive element and negative element in the weak zone will see an intruder at the same time. Because the pyro is a differential element, the output signal will be very low. To solve this problem, models 2 and 3 blind one element. Accordingly, a feature of the pyro of models 2 and 3 is that in the weak zone, the window will stop the energy that isn't wanted to improve overall performance.
To achieve the masking of one PIR element, the width of the window is reduced. The width of the window can have a significant effect on the ability of the new pyro to blind one element. If the window is too small, the pass-through energy is too low to generate an alarm. Otherwise, if the size is too large, it cannot suppress the common mode.
The width of the window is also considered in combination with the mirrors.
Next, the size of each mirror is considered. The width of the mirrors, in part, controls the pyro's performance in each zone. There are two features of the new mirror assembly. First, the size (width of the mirrors) in the strong zone is small and gradually increases from the strong zone to the weak zone. All the mirrors in the same tier have the same height, so they have different widths (using angle, in part, to describe the width). Second, the width of the largest one (width of the widest mirror) near the weak axis is three times the width of the smallest one near the strong axis (ignoring the beam's occupation of the length of the mirror).
In general, the system uses a pyroelectric sensor assembly having an enclosure, a positive pyroelectric sensing element located within the enclosure, a negative pyroelectric sensing element located adjacent the positive pyroelectric sensing element within the enclosure and a window disposed in the enclosure having an elongated shape with a width of the window parallel to a line joining the respective centers of the sensing elements and the length perpendicular to the line wherein the window is centered over the sensing elements to conduct infrared energy from an external source onto the sensing elements and wherein the width of the window is less than the combined widths of the sensing elements plus any space separating the sensing elements.
Alternatively, the system uses a pyroelectric sensor assembly having an enclosure, a first pyroelectric sensing element located within the enclosure, a second pyroelectric sensing element located adjacent the positive pyroelectric sensing element within the enclosure, a window disposed in the enclosure having an elongated shape with a width of the window parallel to a line joining the respective centers of the sensing elements and the length perpendicular to the line wherein the window is centered over the sensing elements to conduct infrared energy from an external source onto the sensing elements and wherein the width of the window is less than the combined widths of the sensing elements plus any space separating the sensing elements and a plurality of mirrors arranged outside the enclosure adjacent the window that reflects incident light onto the first and second pyroelectric elements.
Alternatively, the system includes a security system that protects a secured geographic area, a pyroelectric sensor assembly that detects threats within the secured area, the pyroelectric sensor assembly further including an enclosure, a first pyroelectric sensing element located within the enclosure, a second pyroelectric sensing element located adjacent the positive pyroelectric sensing element within the enclosure and a window disposed in the enclosure having an elongated shape with a width of the window parallel to a line joining the respective centers of the sensing elements and the length perpendicular to the line wherein the window is centered over the sensing elements to conduct infrared energy from an external source onto the sensing elements and wherein the width of the window is less than the combined widths of the sensing elements plus any space separating the sensing elements and a plurality of mirrors arranged outside the enclosure adjacent the window that reflects incident light onto the first and second pyroelectric elements.
From the foregoing, it will be observed that numerous variations and modifications may be effected without departing from the spirit and scope hereof. It is to be understood that no limitation with respect to the specific apparatus illustrated herein is intended or should be inferred. It is, of course, intended to cover by the appended claims all such modifications as fall within the scope of the claims. Further, logic flows depicted in the figures do not require the particular order shown, or sequential order, to achieve desirable results. Other steps may be provided, or steps may be eliminated, from the described flows, and other components may be add to, or removed from the described embodiments.
