Patent Application
20220163377
The current invention takes place in the security alarms field; more precisely, in the development of methods and devices of physical, industrial, and civil security that work with optical fiber. Particularly, the disclosure refers to a method and device for detecting vibrations in the periphery of an optical fiber which includes a CMOS camera and a LED laser.
The optical fiber is a thin thread strand made of glass or fused/molten silicon that conducts light. The thickness of the filament is comparable to a single human hair, namely, 0.1 mm approximately. Three components are mandatory to establish communication with optical fiber: The light source which can be LED type or laser type, the transmitting medium which corresponds to the optical fiber, and the light detector that can be a photo-diode. The light transmission happens because the inner light beam inside the fiber, suffers an almost total reflection every time it tends to go out of the core.
The optical fibers are used in telecommunications since 1960 because they allow sending a big amount of data, covering large distances at the speed of light; therefore, its use in data transmission has become regular in the recent years. Nevertheless, the use of optical fiber as anti-intrusion sensor in perimeter security is less frequent. The implementation of the optical fiber as intrinsic sensor allows taking full advantage of the material features. Some of the advantages of using optical fiber in perimeter security comprehend immunity to electromagnetic disturbances, the great mechanical resistance which facilitates its installation, the weight is much lower than the weight of other metal cables, the non-production of interference, the heat, cold and rust resistance, the insensibility to parasites, the non-conductivity and the rust immunity.
The optical fiber works because occasionally, a light emitted by a laser is transmitted by optical fiber, and the light that emanates at the end of the fiber produces a patter known as speckled pattern. When a disturbance is presented on the fiber, even if it is small and related to changes in the environmental conditions, the speckled pattern changes and it is detected by the light receptor.
The CMOS sensors are built with Complementary Metal-Oxide-Semiconductor technology, they detect the light based on the photoelectric effect/principle and their sensibility in the spectrum range goes from 300 nm to 1000 nm approximately. When working with the CMOS sensors, the charge is transformed into an analogical voltage in every pixel within the same sensor, thus, each cell is independent. Subsequently, for every active line, the signal is amplified through the read circuit, the noise is minimized, then it is digitized and finally, it is transmitted in parallel.
The activated pixel sensors have advantages over other light detection sensors. Given that the conversion is done in each cell, when the CMOS sensors are used, an external chip for this function is not necessary, and this fact results in a reduction of the cost and size of the sensor. One of the huge advantages is that CMOS sensors are more sensitive to light, therefore, their behavior is better even when exposed to poor lightning conditions. In addition, the CMOS sensors offer higher speed because all the process is carried out inside each cell. Finally, another important advantage is related with the power consumption: they use less energy, mainly due to the signal amplifiers, which are located in the cell itself
The publication of the Korean patent KR20040105331 announce a method of speckled signal processing of an optical fiber sensor that allows monitoring intruders. The said method increases the accuracy of the monitoring system by allowing the system to filter a false signal coming from a natural phenomenon. The operation starts when the signal is photoelectrically converted into a receptor element, and then it is processed in multiple stages. Subsequently, a microprocessor compares the primary signal emitted from a comparator with reference pulse width data, unit time data, and a reference pulse number to generate an intrusion detection signal.
The publication of the patent MD2010S000037 release an intrusion alarm system with optical fiber that includes a coherent light source, alongside a multi-modal optical fiber segment, a photo-detector, and a warning alarm builder. The photo-detector corresponds to a CCD (Charge Coupled Device) to register the speckled patterns in the far field where the fiber is located. For processing, a computer is used, which contains a numerical matrix differentiator of two consecutive speckle patterns, an adder of the corresponding difference signals from every two consecutive speckle patterns, and a comparator, all connected in parallel to an alarm trigger threshold setting unit. In the system, the comparator sends the alarm signal when the addition of the difference signals of two consecutive speckle patterns exceeds the default warning alarm trigger threshold.
The U.S. Pat. No. 7,189,958 B2 announce a system, device and method to detect disturbances using an optical fiber sensor. The system comprehends a multi-modal optical fiber spatially distributed, a photo-detector configured to detect the signals coming from the said fiber, a wireless digital module coupled to the photo-detector that transmits a plurality of coded variables of the optical signals detected, a wireless receptor module, and a processing module coupled to the said receptor that decodes and interprets the signals.
According to the information above, it is clear from the technique status, that systems for vibrations detection in an optical fiber used for perimeter security already exist. Said systems use complex processing algorithms that allow triggering an alarm signal, and even several of them require the use of a computer to process calculations and further signal emission to the other systems. This requirement, besides from increasing the device size, it also increases the manufacturing and maintenance costs, and its use is limited to safe places where there is no risk of theft.
In addition, the use in the technique state of complex algorithms for processing, slow down the alarm generation process because it requires more time to finish the analysis of detected disturbances. Besides, the complex algorithms increase the energy consumption of the devices, making the maintenance more expensive for the user.
Additionally, the state-of-the-art devices use multiple conditioning stages to stabilize the reference signal and guarantee the system correct operation. The majority of the state-of-the-art systems require post-processing stages or conditioning of the analogical signal of the sensing element independently, whether it is done through operational amplifiers (op. Amp) or through other elements that are susceptible to the environmental electromagnetic noise, as it occurs with the patent U.S. Pat. No. 4,297,684.
Currently, other devices with similar features have the protection of big perimeters as their main focus. This is related to the techniques used, which are focused mainly to detect light losses by retro-dispersion or scattering. Those applied techniques require equipment that include stages or modules of optical and electronic conditioning of high accuracy, composed by electronic systems operating at a processing high-speed such as FPGAs, equipment with features similar to the ones of the OTDR systems (Optical Time Domain Relations), which are recognized for their high cost. While many of the existent systems that are available in the market have the capacity of detecting short perimeters, it is not possible to apply this type of techniques in short distance perimeters due to the investment that it requires.
Finally, the majority of the state-of-the-art systems require configuration of several parameters by the user for the operation to be possible, which makes the setup task complex for the security integrators and for the users too; the previous statement leads in many cases, to errors on the device configuration and possible failures when detecting alarms.
Accordingly, there is a need in the art, for new device models and methods for detecting vibrations in the periphery of an optical fiber; said devices and methods must be distinguished for i) working with both lightweight and low cost electronic cards so that a computer or a tablet is not a requirement for signal processing, ii) working with both recursive and low-processing algorithms to increase the device speed and reduce the energy consumption, iii) allowing the detection of disturbances in small perimeters, and iv) facilitate the device configuration through determining a few parameters to make easy its start of operation.
Hence; the presented invention release a method and a device for detecting vibrations in the periphery of an optical fiber, this devices is distinguished for using a low-complexity detection method which use recursive algorithms implemented within an electronic card which makes the device lightweight, low-cost, fast, with low index of false alarms, and with low energy consumption.
Additionally, the device and the method have the advantage of allowing the disturbances detection in small perimeters, making it suitable where the technologies of periphery detection with optical fiber cannot be used normally. The processing method allow decreasing stages of analogical conditioning by simplifying the development of this type of system. Another advantage of the device is its easy configuration because only a few parameters are require for its operation which is an advantage for the users and the security integrators.
The device operation mentioned here is based on the interferometer pattern of speckle type. The interferometry use cinematic techniques to describe light patterns caused by disturbance on the optical fiber, where said patterns are analyzed through a CMOS sensor and micro-controlled embedded systems.
Therefore, the device in this invention, which allows detecting vibrations in the periphery of an optical fiber, is divided mainly in five subsystems that are interconnected between to reach the complete device operation.
In general terms, the disturbances are detected through the optical fiber system (2). To detect there must be light transmitted through the optical fiber, said light is generated by the light source system (6); thus, it is possible to read the interference speckled patterns generated in the optical fiber, when it is disturbed by means of the CMOS micro camera system (5). Afterwards, the information sent digitally through the CMOS camera is analyzed through a processing system (7) giving an alarm signal as a result, which is notified abroad through a communications system (1). Next, each one of the devices of perimeter security is explained in detail.
First, the optical fiber system (2) is composed by a sensor cable made of optical fiber (21) which length oscillates between the 1 m-5 Km interval, and two SMA-M connectors (22) coupled to each end side of the optical fiber cable to be further connected to the mechanical housing (11).
The sensor cable of the optical fiber is designed to be mounted on chain link mesh, fence, wall or even buried, attempting to detect invaders in restricted perimeters of big or medium length, corresponding to 1 m and onwards. When the optical fiber sensor is installed over a chain link mesh surface, the sensor cable must be hold and fasten with plastic ties. Before the installation of the optical fiber, it is verified that the mesh, wall or surface where the sensor is going to be installed, is well taut and free of obstacles or trees that could generate false alarms.
In a preferred embodiment of the invention, the optical fiber sensor cable/wire used is duplex type, that is to say, it is composed by two filaments together. When duplex wire is used, it is necessary to use a mechanical joint (23) to join the ends of the optical fiber cable.
In another invention embodiment, the optical fiber sensor cable used is simplex type, that is to say, it is composed by a unique filament. If simplex optical fiber is used, it is not necessary to use the mechanical junction, because it turns over itself connecting one end side to (4) and the other one to (5). Also, a laser can be connected at the end side of the fiber, taking the most of the maximum length of the fiber. The type of fiber to be used, whether it is simplex or duplex will depend on the setup/installation conditions.
The SMA-M connector (22) of the optical fiber system (2) allowing coupling the optical fiber cable in an aligned and accurate way, in one side with the light source system (6) which transmit the light and, in the other side, with the CMOS micro-camera system (5) which is acting as a receptor sensor of the light that crosses the optical fiber. A SMA-M connector is coupled with the SMA-F connector (3) of the CMOS micro-camera system (5) and the other one is coupled with the SMA-F connector (4) of the light source system (6). This coupling mechanism of the SMA connectors allows an easy connection and disconnection of the optical fiber cable/wire when it is required.
The second system is the light source (6). Said system is composed mainly by a light source, an activation control stage, and a stabilization stage of the light source voltage. Each stage plays an important role on the system operation, the general features that is accomplished by each stage is explained as it follows. The main function of the voltage stabilizer stage is to guarantee that the electric supply has the quality and characteristics of voltage required. The coherent light source stage corresponds finally to the light emitting source. The activation control stage of the electronics is the one that analyses that the system requirements needed, such as electric supply stability and activation configuration parameters, are being accomplished. Only after evaluating these conditions, the activation control stage will be able to send a valid activation signal to the coherent light source stage to start the operation.
In a preferred embodiment, the light source system (6) has a laser diode to emit coherent light. This diode emits a laser light with visible radiation in the 650 nm-660 nm wavelength interval. Due to its narrow bandwidth, allows focusing greater part of its energy within a specific area in comparison with a LED diode.
The high coherence that is presented by this laser light source helps the generation and identification of the speckled pattern in a more effective way by the CMOS system (5) A low-coherence light source could generate a speckled pattern too diffuse, leading to a hard detection of the speckled pattern. The light source system (6) is complemented with a stage in charge of stabilizing the voltage signal and an activation control stage that evaluates the necessary conditions to launch the operation of light emitting source.
The CMOS micro-camera system is the third system (5). The CMOS micro-camera system has a sensor of active pixels built with Complementary metal-oxide semiconductor (CMOS). The speckled pattern generated when illuminated by means of the light source traveling through the optical fiber, is detected with this sensor. The pattern is detected through the photosensitive array that the CMOS camera contains (51). The cells of the CMOS array are completely independent from their neighbors and the digitization is done pixel by pixel within the same sensor. Therefore, the displacement coordinates of each interference speckled pattern, generated when the optical fiber cable (21) is disturbed, can be obtained by means of the CMOS micro-camera.
In a preferred embodiment, the CMOS micro-camera has an operation voltage between 1.8 VDC and 5 VDC. In addition, the sensor has an operation frequency of 20 MHz and it works with temperatures between −10° C. and 60° C. The CMOS sensor has a dimension of 2 mm×2 mm.
The processing system is the fourth system (7). The processing system (7) uses a micro-controller where the resultant displacement of the speckle mots in a certain time over the CMOS array (51) is calculated. The information about the magnitudes of the specks displacement allows determining how strong the disturbance over the optical fiber cable was (21). Besides, in the processing system (7) the necessary thresholds are defined to be able to make a discrimination of the displacement levels that represent a real event and the ones which represent a false event, to further send the notification signals to the communications system (1).
Finally, the communications system is the fifth system (1). Said system includes a wired communication subsystem (10) that has a USB output and a dry contact output. In addition, in one embodiment of the invention, the communications system (1) also comprehends a WiFi communication subsystem (8), and a communication subsystem with multiple frequencies, such as 800 MHz-900 MHz (9), for instance.
In a preferred aspect, the USB communication (Universal Serial Bus) of the wired communication subsystem (10) follows a standard that defines cables, connectors, and protocols, used in a bus to connect, communicate and feed electrical supply between computers, peripherals, and electronic devices. The USB connector allows communicating with a computer to execute the configurations for the device operation, Said USB output has compatibility with USB 2.0, it has transmission Low Speed of 1.5 MB/s and a transmission Full Speed of 12 MB/s.
In another preferred aspect, the dry contact output of the wired communication system (10), work with an electromagnetic device that, when stimulated with a very weak electrical current, opens or closes a circuit in which a greater power than the one in the stimulating circuit, is then dissipated. For the dry contact output, a relay with an activation voltage between 3.3 VDC and 30 VDC is used. The relay connection voltage goes until 125 VAC and its operation current can reach 1 A. It is important to considerate that according to the application type required, this relay can be changed for custom applications that may have a greater operation current range or a greater operation voltage range, regarding the available models.
The main function of the dry contact output is allowing the connection of external elements for the alarms notification or, for the activation of any external device of greater power. Some of the possible external elements for connection are sound beacons or audible, conventional alarms panels, communication modems, ON/OFF-type inputs for capturing images through CCTV (Closed-circuit television) systems, among others.
In a preferred embodiment, the WiFi communication subsystem (8) has the task to establish both short-distance and long-distance communication via WiFi with a router or a mobile device for the system parameter configuration and to send the live report of alarms and events. The WiFi communication module operates with the IEEE 802.11 b/g/n standard/protocol. Besides, security WPA/WPA2 is supported, and it has an operation frequency of 2.4 GHz. The device can communicate (or allows communication) via Internet with remote systems, by making part of IoT Network, or with administration systems with protocols API-REST and chat bots which allow the interaction with the system through CHAT applications, direct connections to ERPs and CRMs, which perform an integral management of perimeters.
In another preferred embodiment, the 800 MHz-900 MHz communication subsystem (9) provides long-distance wireless communication for the system parameters configuration, alarms/events live report, and this is information is sent to remote central module which has the capacity to interpreting which exact module or system is sending the information. The used module is distinguished for 1) having a line-view communication range from 1 to 21 Km, 2) allowing firmware updates through the air, by means of other compatible modems, and 3) having a RF data performance that can reach the 200 KB/s.
In another aspect of this invention, the communication system (1) includes the integration of other subsystems, the integration of both wired and wireless communication technologies such as the Modem GSM/3G/4G, Sigfox modules or NBC communication systems (Narrow Band Communication).
The device of the present disclosure, also has a mechanical housing (11) which contains all the device components except from the optical fiber system (2) and it is made of aluminum. The mechanical housing is composed by a CMOS camera holder base (12), a laser coupling base and CMOS camera (13), a SMA-F connector (3) of the CMOS micro-camera system (5), and a SMA-F connector (4) of the light source system (6).
In a preferred embodiment, the CMOS camera holder base (12) mechanically holds the CMOS camera and has a rectangular slot in the center, where the CMOS camera is placed. This base is built in ABS or aluminum.
In another preferred embodiment, the laser coupling base and the CMOS camera (13) mechanically supports the CMOS camera holder base (12) and the laser diode. In addition, in its external face, it has the SMA-F connectors (3) (4) through which the optical fiber system will be coupled (2). This base is built in ABS or aluminum.
The method for detecting vibrations in the periphery of an optical fiber comprises multiple steps; first, disturbances are produced in the optical fiber sensor cable (21), then, the respective speckled pattern of disturbances is read by the CMOS micro-camera system (5), these disturbances are projected over the CMOS array (51), that sends signals indicating the coordinates within the CMOS array (51) in which the disturbance is reflected.
Therefore, in the method is important to consider that, when the system first starts, the variables reading the changes of the coordinates projected over the CMOS array (51), which are controlled by the processing system (7), they are set in the value=(0,0). When receiving the coordinates signals by the CMOS array (51), the processing system (7) calculates the displacement generated by the disturbance taking the coordinate value (0,0) as the reference point, where said displacement is represented by a coordinate inside the CMOS array (51).
The processing system (7) performs the summation of all the speckle displacement magnitudes, the final displacement (df) can be calculated from said summation, using the equations of the
Further, once the time to take the displacement is finished, the displacement system (7) start decreasing the variables containing the value of the speckle coordinates (14), which were obtained by the CMOS micro-camera system (5). This decrement continues until the variable that obtains the vector magnitude data reaching a point of coordinates (x, y), returns to its initial position (0,0). The speed for generating these decrements is directly related to the system sensibility.
Then, the processing system (7) compares the final displacement information obtained, with different thresholds, in a way a discrimination or discernment can be done, to determine which speckle displacement levels (14) could discern a real event or a false one.
Additionally, the system uses a monitoring technique of the image quality obtained by the CMOS array (51). Said quality is measured by calculating the average of the information of each pixel, sent by the CMOS array (51). This image information depends on how the light source system (6), when traversing the optical fiber (2), affects each pixel in the CMOS array (51), allowing to diagnose the implementation status regarding its initial status configuration.
Finally, once the processing system (7) had performed the analysis, it is able to send each event notification using the communication system (1), whether using an output medium through the wired communication subsystem (10), or via wireless through the WiFi communication subsystem (8), or the 800 MHz-900 MHz communication subsystem (9), or any transmission method.
In a preferred embodiment, the device announced has the advantage of allowing the user to configure three parameters of easy operation, adjustable with a software tool for each zone and installation type. Such parameters are: sensibility, analysis time and activation duration. The variation on the analysis time, allows having a sensibility adjust in the reference measure. Such analysis period can be adjusted in a range between 1 ms-40 ms.
The device for detecting vibrations in the periphery of an optical fiber has different purposes beyond the perimeter security; in an embodiment, the device can be used over the motor bases to determine when they are ON, or analyzing its vibration modes, with which its operation status or failures diagnose is determined. In another embodiment, it can be used with a blanket for critical patients to analyze the vital signs, or to alert for the patient excessive still time, also, in transport systems for detection and counting of vehicle axles, among others.
In one use the device can be used to delimit restricted areas by embedding it in the floor, determining when the person or the object crosses a specific line. In other use, the system can be used to create smart mats, which could announce when somebody steps on them. Finally, the device can also be used to determine when a mountain landslide would occur, a structure collapses or to detect earthquakes.
Aiming to facilitate the understanding of this invention, a detailed description of the here presented drawings will be made:
The following detailed description of the invention refers to the here attached figures. Although the description already includes feasible examples, others are also possible and changes of the performance can also be made. Changes to the invention are possible and should be considered by those who are well versed. However, many changes could lead to results that go beyond the scope of the invention.
In
In
In an embodiment form presented in the
In a preferred embodiment of the invention, shown in the
In an embodiment shown in the
The
The
The
The
The
| Number | Date | Country | Kind |
|---|---|---|---|
| NC2019/0002303 | Mar 2019 | CO | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/IB2020/052162 | 3/11/2020 | WO | 00 |
