Patent Publication Number: US-2012033082-A1

Title: System and Method for Spatial Division Multiplexing Detection

Description:
FIELD OF THE INVENTION 
     The present inventions generally relates to the field of electronic surveillance and, in particular, to a system and method for detecting and monitoring one or more targets. 
     BACKGROUND OF THE INVENTION 
     Electronic surveillance is extensively used by military, law enforcement, commercial, and private entities. Typically, the goals of electronic surveillance include detection and monitoring of one or more objects of interest (referred to herein as “targets”) in video data sequences produced by respective surveillance apparatus(es). In applications, electronic surveillance is often performed in a real time. 
     Main challenges in the field of electronic surveillance relate to detection of targets that change their characteristics due to motion, orientation in 3D space, or temporary occlusion by other objects.  FIG. 1  depicts a high-level, schematic diagram of a conventional system  100  for detecting and monitoring targets. The system  100  includes a low-resolution stationary video camera  110  having a large field of view  102  and a high-resolution video camera  120  having a small field of view  106 . 
     Video camera  120  is typically mounted on a gimbaled platform  104 , which provides panning the field of view of the high resolution camera  106  within the field of view of the lower resolution camera  102  (illustratively shown with arrows  108 ). However, in operation, insufficient resolution of camera  110  and a limited size and speed of panning the field of view of the high resolution camera  106  to acquire targets of interest detrimentally affect efficiency of the system  100 . 
     Therefore, despite the considerable effort in the art devoted to systems and methods for detecting and monitoring targets, further improvements would be desirable. 
     SUMMARY OF THE INVENTION 
     Embodiments of the present invention are generally directed to systems and methods for detecting and monitoring targets, including multiple moving targets. 
     One aspect of the invention provides a system for detecting and monitoring targets. The system comprises a plurality of surveillance monitors, which are selectively aligned in pre-determined directions to form an integrated field of view of the system. The integrated field of view is substantially equal to a sum of the fields of view of the component surveillance monitors and may represent, for example, an M×N matrix of the fields of view of these monitors, where M and N are integers and at least one M or N is greater than 1. To increase detectability of the targets, at least portions of the integrated field of view may be illuminated using a scanning laser beam. 
     Another aspect of the present invention provides a method for detecting and monitoring targets using the inventive system. 
     Various other aspects and embodiments of the invention are described in further detail below. 
     This summary is neither intended nor should it be construed as being representative of the full extent and scope of the present invention, which these and additional aspects will become more readily apparent from the detailed description, particularly when taken together with the appended drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a high-level, schematic diagram of a conventional system of the prior art for detecting and monitoring targets. 
         FIG. 2  is a high-level, schematic diagram of an exemplary system for detecting and monitoring targets in accordance with one embodiment of the present invention. 
         FIG. 3  is a flow diagram of a method for detecting and monitoring targets using the system of  FIG. 2  in accordance with one embodiment of the present invention. 
     
    
    
     To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. The images in the drawings are simplified for illustrative purposes and are not depicted to scale. 
     The figures of this application illustrate exemplary embodiments of the invention and, as such, should not be considered as limiting the scope of the invention that may admit to other equally effective embodiments. It is contemplated that features or steps of one embodiment may beneficially be incorporated in other embodiments without further recitation. 
     DETAILED DESCRIPTION 
     Referring to the figures,  FIG. 2  depicts a high-level, schematic diagram of an exemplary system  200  for detecting and monitoring targets in accordance with one embodiment of the present invention 
     Hereafter, aspects of the present invention are illustratively described within the context of targets. A target in this context can be any stationary or moving object, such as land vehicles, aircraft, missiles or their plumes (for example, rocket propelled grenades (RPGs), ballistic or cruise missiles, among other missiles), traces of laser beams, objects floating in air, free space, liquid or on a surface of liquid, and the like. The invention may also be utilized within the context of other types of targets (for example, humans, animals, or body parts thereof or various material objects), which presence and/or movements are monitored in the respective conventional habitats, conditions, or environment. It has been contemplated and is within the scope of the invention that the system  200  is utilized within the context of any of such targets or a combination thereof. 
     In one exemplary embodiment, the system  200  includes a controller  210 , a plurality  220  of stationary surveillance monitors  120   1 - 120   n  (surveillance monitors  120   1 - 120   4  are shown), an image data processor  230 , and, optionally, a laser  240  and a laser beam scanning apparatus  250 . In a preferred embodiment, stationary surveillance monitors  120   1 - 120   n  are high resolution video cameras of the type shown in the prior art system of  FIG. 1 . 
     In operation, the controller  210  administers the functioning of components of the system  200  and implements a pre-determined target search/monitoring algorithm, which may be implemented by software or firmware stored in a memory of controller  210  or, alternatively, in a memory of image data processor  230 . 
     Controller  210  is generally an industrial or military specification computer processor adapted to control various computational and hardware resources. In the depicted embodiment, the controller  210  is coupled to the components of the system  200  via a common bus  204 . 
     Surveillance monitors  120   1 - 120   n  are generally sensors of particular targets or their respective identifiers, for example, digital video cameras, telescopes, detectors of visible, infra-red (IR) or ultra-violet (UV) light, X-rays or ionizing radiation, among other sensors. Information acquired by monitors  120   1 - 120   n  is processed by image data processor  230 , as discussed below in reference to  FIG. 3 . 
     Surveillance monitors  120   1 - 120   n  may be installed on either stationary or moving platforms, including ground, buildings, planes or helicopters, ships, balloons, unmanned aerial vehicles (UAVs), and the like, but in general are stationary with respect to each other. That is, unlike the prior art system shown in  FIG. 1 , surveillance monitors  120   1 - 120   n  are not gimbaled, such as to be able to move with respect to each other or with respect to the stationary or moving platform upon which system  200  of the present invention is mounted, but are stationary, such as to define integrated field of view (IFOV)  202 . In one exemplary embodiment, the surveillance monitors  120   1 - 120   n  are ground-mounted, high resolution digital video cameras. 
     The surveillance monitors  120  are selectively aligned and fixed in pre-determined directions in three dimensional space in a manner providing that, in the space, their respective fields of view, or apertures, form a pre-determined pattern. Although  FIG. 2 . shows a two dimensional pattern formed by aligning fields of view  106   1 - 106   n  of surveillance monitors  120   1 - 120   n  respectively, other arrangements may be used, such as forming a three dimensional IFOV by aligning the fields of view  106   1 - 106   n  of surveillance monitors  120   1 - 120   n  to the same area of space, but setting different depths of field on each individual monitor. In another embodiment, the fields of view  106   1 - 106   n  of surveillance monitors  120   1 - 120   n  may be disjoint. 
     A sum of the fields of view of the fixed surveillance monitors  120   1 - 120   n  represents integrated field of view  202  of the system  200 . In system  200 , the surveillance monitors  120   1 - 120   n  are high-resolution sensors that are operated simultaneously. As such, target resolution capabilities of a single surveillance monitor  120  are instantly provided over the entire IFOV of the system. 
     Typically, the surveillance monitors  120   1 - 120   n  have the same or substantially the same resolution and apertures, and the system  200  preferably comprises from about two to nine surveillance monitors, although any number may be used to form the IFOV, and, the cameras may differ in field of view and aperture. Preferably, the IFOV is contiguous. In one embodiment, the IFOV of the system  200  is an M×N matrix of the fields forming a rectangular or quadrate IFOV, wherein M and N are integers and at least one M or N is greater than 1. 
     For example, in the embodiment depicted in  FIG. 2 , fields of view  106   1 - 106   4  of the surveillance monitors  120   1 - 120   4  form a 2×2 matrix representing an IFOV  202  of the system  200  (boundaries of the apertures of the surveillance monitors  120   1 - 120   4  are shown with phantom lines  221 ). In some embodiments, the IFOV  202  and the field of view  102  (discussed in reference to  FIG. 1 ) may have the same or similar dimensions. 
     In 3D space, adjacent fields of view preferably overlap one another by pre-determined margins  224  and  226  (shown with broken lines for the field of view  106   4  only) and any overlap is taken into account by software in image data processor  230 . Generally, the margins  224  and  226  are selected in a range from 5 to 20% of the respective width of the field of view. 
     In the system  200 , a number K of the surveillance monitors is generally defined by areas of the required IFOV and the fields of view of component surveillance monitors  120 , and an amount of overhead A OV  caused by overlapping of the adjacent fields of view. In particular, if an area of a field of view of a component surveillance monitor  120  is equal to A SM , the system  200  having a rectangular IFOV with an area S may comprise K=S/(A SM +A OV ) surveillance monitors  120 . 
     Optionally, a laser may be provided as a component of the system. Laser  240  irradiates a beam  241  adapted to illuminate the one or more targets to increase their detectability by the surveillance monitors  120 . Targets may be selected by the target search/monitoring software, running on either controller  210  or image data processor  230 . In operation, the laser beam scanning apparatus  250  scans (illustrated using arrows  206 ) the beam  241  in the IFOV of the system  200  (e.g., IFOV  202 ) or portions thereof, as discussed below in reference to  FIG. 3 . 
     Laser beam scanning apparatus  250  generally comprises a substantially reflective concave minor  252  disposed on a gimbaled platform  254  and a sensor  256 . In operation, the gimbaled platform  254  engages the minor  252  in a cyclical motion, which results in scanning of the laser beam  243  reflected from the minor  252  in the entire IFOV or a pre-determined portion of the IFOV, as determined by the target search/monitoring software. 
     In one embodiment, the mirror  252  has a calibrated value of a leak of incident laser radiation (i.e., beam  241 ) through the material of the minor, and a leaked portion  251  of the beam  241  is acquired by the sensor  256 . Orientation of the laser beam  243  in the space and spatial characteristics of the leaked portion  251  are inter-related and are defined by an instant position of the minor  252 . 
     Sensor  256  (for example, a charged-coupled device (CCD) sensor) analyzes the portion  251  of the beam  241  to determine the direction, in the 3D space, of the reflected laser beam  243 . In particular, the sensor  256  identifies the surveillance monitor  120 , which field of view or a portion thereof is currently illuminated by the laser beam  243 , and provides this information to the image data processor  230  (shown in phantom with a link  258 ). 
       FIG. 3  is a flow diagram of a method  300  for detecting and monitoring targets using the system  200  of  FIG. 2  in accordance with one embodiment of the present invention. To best understand the invention, the reader should refer to  FIGS. 2-3  simultaneously. 
     The method  300  is illustratively discussed herein in reference to the system  200  having four surveillance monitors  120   1 - 120   4 . In other embodiments, the system  200  may comprise a different number of the surveillance monitors or surveillance monitors aligned to form an IFOV having a different form factor. 
     In various embodiments, method steps of the method  300  are performed in the depicted order or at least two of these steps or portions thereof may be performed contemporaneously, in parallel, or in a different order. For example, portions of steps  330  and  340  may be performed contemporaneously or in parallel. Those skilled in the art will readily appreciate that the order of executing at least a portion of other discussed below processes or routines may also be modified. 
     At step  310 , a plurality of surveillance monitors (for example, surveillance monitors  120   1 - 120   4 ) are aligned in pre-determined directions to form, in 3D space, an IFOV having a pre-selected form factor (for example, IFOV  202  having a 2×2 quadrate form factor). 
     At step  320 , the surveillance monitors of system  200  are simultaneously engaged (i.e., activated), thereby forming the IFOV of system  200 . Within the IFOV, a plurality of targets may be detected and/or monitored using target search/monitoring software, with the high resolution of the component surveillance monitors (i.e., surveillance monitors  120   1 - 120   4 ). 
     At step  330 , the IFOV or one or more pre-determined fields of view of particular surveillance monitors may optionally be scanned by a beam of a laser (for example, laser  240 ) that is adapted to illuminate at least portions of the IFOV, preferably portions of IFOV containing the target(s) and, as such, increase detectability of the target(s). In one embodiment, the laser beam may continuously scan the entire IFOV of the system  200 . In alternate embodiments, after particular targets have been detected, the laser beam may selectively illuminate these targets. 
     At step  340 , information provided by the surveillance monitors is processed by a respective data processor (e.g., image data processor  230 ). In one embodiment, the data processor processes information provided by each of the surveillance monitors in an order that is determined based on a target search/monitoring algorithm. For example, information provided by each of the surveillance monitors may be processed sequentially. 
     In an alternate embodiment, when a specific target is expected to be present in the field of view of a particular surveillance monitor, information provided by that monitor may be processed more frequently. Optionally, laser beam  243  may scan the field of view of that surveillance monitor more frequently or with a smaller pitch. In yet another embodiment, a combination of these or other search/monitoring algorithms may be used in system  200 . 
     Although the invention herein has been described with reference to particular illustrative embodiments, it is to be understood that these embodiments are merely illustrative of the principles and applications of the present invention. Therefore numerous modifications may be made to the illustrative embodiments and other arrangements may be devised without departing from the spirit and scope of the present invention, which is defined by the appended claims.