Abstract:
An interactive security screening system includes a main housing, a contact pad provided on the main housing and a sample sheet positioned upon the contact pad. A sensor is operatively connected to the contact pad to measure pressure applied to the contact pad during a sample collection process. A feedback system, operatively connected to the contact pad and the sensor, provides the subject or screener with at least one of a visual signal and an audio signal to indicate whether requisite pressure was applied to the contact pad. A sample processing system analyzes the sample collection sheet through series, parallel or image processing to determine whether the trace residue sample contains a threat residue. The screening system also employs a spatial recognition system that focuses the sample processing system on particular portions of the sample collection sheet to increase overall system accuracy.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present application claims the benefit of U.S. Provisional Patent Application Ser. No. 60/756,573 filed Jan. 6, 2006 entitled “System and Method For Optimization of Trace Chemical Sample Collection and Analysis in Personnel Screening and Security Systems.” 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention pertains to the art of security screening systems and, more particularly, to an interactive security screening system that focuses a sample processing system on particular portions of a collected sample and employs one or more processes to screen the collected sample for threat residue. 
     2. Discussion of the Prior Art 
     Since Sep. 11, 2001, protection against terrorist threats has become a national priority. This priority extends from the protection of government facilities inside the U.S. and abroad to the protection of private businesses and venues. Various types of threats have been postulated, including attacks using explosive, chemical and biological agents, as well as nuclear and radiological (dirty) bombs. The diversity of this threat has created complex security challenges for national, state, and local governments, the transportation industry, private businesses, and even individuals. Total expenditures related to Homeland Security topped $100B in one year and billions more have been allocated in Federal, Supplemental Appropriations, and State/Local spending. Increasingly, U.S. businesses are devoting more revenue to security systems, with expenditures reaching tens of billions. Growth in the homeland security industry is expected to be vigorous over the next decade. Motivated by the wide diversity of potential threats and by the inadequacy of currently available systems, government investments in research and development are strong. 
     Of the various threats postulated, explosives remain the number one choice of terrorists. Indeed, many experts and reports have noted that, in the case of terrorist activity, the statistical evidence is compelling, the primary threat is bombs. At present, two types of detection systems are in use to combat this threat, i.e., bulk detection systems and trace detection systems. Bulk detection systems identify the presence of a large or threat quantity of explosives. In contrast, trace detection systems identify the presence of residual contamination associated with explosives. That is, trace detection identifies whether an object or person has come into contact with or handled explosives. 
     Bulk systems can cost more than $1M per portal, while trace detection system generally run in the order of tens of thousands of dollars. Often times, installation and annual maintenance costs will exceed the original price of the system. In the case of trace explosive detection, currently deployed systems were developed primarily for the use of analytical chemists in laboratories and only later adapted for field use. Unfortunately, these systems suffer from long clearance times following a positive detection (15-30 minutes), have exceedingly high false alarm rates and require extensive training to ensure proper use and maintenance. Given the high price associated with the use of bulk detection systems and their lack of suitability for many screening tasks, such as the screening of people, trace detection systems are used with increased frequency and are most often selected for applications outside of aviation security. 
     The use of trace explosive detection systems is based on widely accepted scientific evidence indicating that handling or otherwise contacting explosives leaves trace residue on hands, clothes, and other materials or surfaces. The trace residue is of a high concentration and is difficult to eradicate. The entire justification for the Federal Aviation Administration&#39;s trace explosive detection program is based on this fact. Indeed, contamination is expected to be so extensive and difficult to eliminate that currently installed aviation trace explosive detection systems depend on secondary contamination, i.e., contamination transferred from an individual&#39;s hands and clothes to their baggage. Thus, the baggage is sampled for trace explosives and subjected to detection systems for analysis. While currently deployed trace detection systems have high sensitivity, the systems suffer from high operational burdens, poor sampling efficiencies, high false alarm rates and low throughput. 
     It is known that explosive contamination can vary widely over small spatial distances. Studies have shown that trace residue levels can differ by 10,000 fold over distances as small as a few centimeters. Unfortunately, currently available trace explosive detection systems sample only from limited spatial areas, retain no sample spatial information and recover samples from only a small section of the sample acquisition surface. By sampling from only a small area, often times trace residue is not detected even when present at detectable levels elsewhere on the sample acquisition surface. In addition, currently available sample acquisition methods are not optimized to collect particulates in the size and size range distribution most pertinent for explosives detection. In particular, most conventional trace detection systems, such as ion mobility spectrometers, require that the sample acquisition surface be clear of substances that could interfere with the measurement. Unfortunately, many substances that would improve the efficiency of sample recovery, such as adhesives, are not compatible with conventional systems and therefore cannot be utilized. 
     The need for a pristine sample acquisition surface or medium has resulted in two primary sample acquisition methods employed in existing trace detection systems such as swabbing (or swiping) an object and air jets that dislodge and test residue from an object. However, both of these methods are limited in sample recovery efficiency and, as stated above, fail to retain any of the spatial information of the sample or surface. Simple swabbing (or swiping) methods tend to leave large particles on the surface, typically recovering only smaller particles. Other methods, such as the above described air jet systems, often times dislodge larger particles, but leave smaller particles on the surface. Simply put, both of these techniques fail to recover a significant fraction of the existing trace contamination. 
     In addition to the above described shortcomings, problems exist with sample reproducibility when using swabbing techniques. Extensive operator training is required to achieve even moderately reproducible results. The required operator training not only significantly increases operational costs, but the intensity of operator involvement required to obtain a good and consistent sample significantly reduces throughput rates. In any case, additional information, particularly more detailed information regarding a likely spatial distribution of trace sample collection, would not only improve the probability of detection but, by eliminating areas that are not relevant and by permitting image analysis as a secondary level of processing, also improve the signal-to-noise ratio. Currently available systems do not permit such resolution. 
     Finally, existing systems do not to provide feedback to the operator or subject as to the reliability of contact or the force applied during contact (which can impact collection efficiency) and, as such, often fail to achieve adequate sample recovery. In addition to preserving some spatial information about the sample, there is also a need to determine where, on the sampling surface, the trace contamination is most likely to be present. In conventional swabbing systems and in novel systems that enable wider area analysis, such information would improve the signal-to-noise ratio of the analysis by focusing the detection and analysis on the area with the highest likelihood of contamination and by eliminating background signals that can cause unnecessary false alarms. 
     Therefore, despite the existence in the art of security screening systems, there still exists a need for an improved security screening system. More specifically, there exists a need for an interactive security screening system that provides feedback to test subjects and focuses detection on portions of a sample that are most likely to contain trace or threat residue. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to a interactive security screening system including a main housing, a contact pad provided in the main housing and a sample collection sheet positioned upon the contact pad. To initiate a screening process, a subject is asked to contact the sample collection sheet which then collects and retains a trace residue sample for analysis. A sensor is operatively connected to the contact pad and configured to measure a pressure applied to the contact pad during a sample collection process. In accordance with the invention, the screening system includes a feedback system operatively connected to the contact pad and the sensor. The feedback system provides the subject or screener with at least one of a visual signal and an audio signal indicating whether a proper sample has been collected. 
     Once a proper sample is collected, the sample is passed to a sample processing system which scans and analyzes the sample collection sheet to determine whether the trace residue sample contains a threat residue. The sample processing system includes an analyzing portion that employs series processing when maximum scanning accuracy is desired, parallel processing when maximum throughput is necessary or image processing when it is particularly advantageous to remove areas which are not of interest from the sample prior to screening or evaluation. Regardless, the screening system employs a spatial recognition system that focuses the analyzing portion on particular sections of the sample. In this manner, the overall accuracy of the screening system is increased, thereby resulting in fewer false positive results which tend to slow the scanning process, inconvenience individuals and place an unnecessary burden on security personnel. 
     Additional objects, features and advantages of the present invention will become more readily apparent from the following detailed description of preferred embodiments when taken in conjunction with the drawings wherein like reference numerals refer to corresponding parts in the several views. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an upper left perspective view of a screening center including a dynamic user feedback and processing system constructed in accordance with the present invention; 
         FIG. 2  is a cross-sectional side view of the screening center of  FIG. 1 ; 
         FIG. 3  is a detailed view of a palm sensor portion of the screening center; 
         FIG. 4  is a representative view of a sample obtained during a screening process employing the screening center of  FIG. 1 ; 
         FIG. 5  is a block diagram outlining a screening process in accordance with one aspect of the present invention; 
         FIG. 6  is a block diagram outlining a screening process in accordance with another aspect of the present invention; and 
         FIG. 7  is a block diagram outlining a screening process in accordance with yet another aspect of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     As will become more fully evident below, the present invention can take various forms in connection with scanning for various potential threats. However, initial reference is made to  FIGS. 1 and 2  in describing a security screening center or kiosk  2  constructed in accordance with a preferred embodiment of the present invention. Screening center  2  includes a main housing  4  provided with a front wall  6 , a rear wall  7 , a top wall  8 , a bottom wall or base  9  and opposing side walls  10  and  11 . In addition, screening center  2  is provided with various accessories to enhance an overall aesthetic appearance of main housing  4  and help screening center  2  blend in or match a particular venue or location. For example, in the embodiment shown, screening center  2  is shown with a pair of columns  17  and  18 , that, in connection with various colored plaques or murals (not shown) attached to either rear wall  7  or side walls  10  and  11 , provide a readily adaptable enhanced aesthetic appearance to screening center  2  that matches or blends with the particular venue at which screening center  2  is deployed. 
     Screening center  2  includes a sample collecting portion  34  arranged within a housing  37  that retrieves trace residue samples and, in certain instances, demographic samples from a subject. As such, collecting portion  34  includes a residue sample collector  38 , a demographic sample collector (not shown) and an output portion  45  which, as will be described more fully below, outputs or issues an article to the subject upon completion of a screening process. 
     In accordance with the invention, residue sample collector  38  includes a sample collecting sheet  55  positioned upon a palm pad  56 . A pressure or pad sensor  57  is arranged below palm pad  56  and, as will be detailed more fully below, functions to provide feedback to the subject during a sample collection process. In order to protect sample collecting sheet  55  from various environmental factors, palm pad  56  is positioned below a cowl  58 . To ensure proper sample screening, fresh sampling media is provided for each screening process. Towards that end, sample collecting sheet  55  is provided on a continuous roll  59  including a first spool or new media portion  61  and a second spool or used media portion  62  which are separated by a shield  65  and a seal  67 . Tension is applied to collection sheet  55  by a pair of tensioning rollers  70  and  71 , while guide rollers (not separately labeled) are provided to ensure proper positioning upon palm pad  56 . Application details of the overall structure operation and application for security center  2  can be found in commonly assigned U.S. patent application Ser. No. 11/418,193 filed on May 5, 2006 incorporated herein by reference. 
     In a manner that will be discussed more fully below, after obtaining a sample, sample collecting sheet  55  is moved to a sample processing system  75  including an analyzer portion  78 . As shown, analyzer portion  78  includes a housing or light proof chamber  82  within which is positioned an applicator  87  and an image capturing unit or scanner  89 . Arranged below image scanner  89  is a clear shield  92 . Another shield  95  separates applicator  87  from image scanner  89 . A heater  100  is mounted to an underside of clear shield  92 . Heater  100  is activated when necessary to warm agents applied by applicator  87  or to warm the sample sheet to facilitate the screening process. In a manner that will be described more fully below, during the screening process, analyzer portion  78  performs one of several pre-programmed scanning processes on the sample. The particular process employed depends upon various circumstances, such as desired accuracy, throughput or the presence of contaminants. In any case, following analysis of the sample, a controller portion  101  determines whether the sample contains a threat residue. 
     In order to ensure the collection of a proper sample, palm pad  56  includes pad sensor  57  having a pixel array  110  operatively coupled to controller  101 . More specifically, upon approaching screening center  2 , a test subject places his or her hand upon palm pad  56  and applies pressure to sample collection sheet  55 . Preferably, sample collection sheet  55  is provided with an adhesive coating selected for moderate tackiness and skin contact compatibility and in order to minimize background fluorescence or luminescence. In addition, sample collection sheet  55  may have embedded therein various catalysts or precursors to support subsequent analysis or processing steps. For instance, zinc particulates or powder can be employed. 
     To ensure that sufficient pressure has been applied over a wide enough area for efficient sample recovery and to improve reproducibility of sample acquisition, screening center  2  includes a dynamic feedback system  112 . If necessary, feedback system  112  provides visual and/or audible queues to the subject when additional pressure should be applied to palm pad  56 . That is, the pressure applied to palm pad  56  must be of a sufficient force so as to obtain a suitable sample. Visual cues can be provided on a screen portion  113  provided in housing  4  or, as stated above, audible cues, such as “apply more pressure,” can be signaled from screening center  2 . In any event, once the subject has applied sufficient pressure, a proper sample  114  is obtained. 
     In order to maximize sample analysis, screening center  2  also includes a spatial recognition system  115  (see  FIG. 3 ) that performs a spatial analysis on sample  114 . Spatial recognition system  115  utilizes pixel array  110  on pad sensor  57  to designate particular areas of interest on sample  114 , such as A 1 -A 8  (see  FIG. 4 ). More specifically, studies have shown that particular portions of a hand are more likely to include trace residue than others. Thus, spatial recognition system  115  enables analyzer portion  78  to focus on particular points of interest A 1 -A 8  of the obtained sample  114  in order to increase the reliability of the screening process. Once spatial analysis is complete, sample collection sheet  55  is shifted into analyzer portion  78  and the screening process continues. 
     In accordance with the invention, analyzer portion  78  employs one or more processes when screening sample  114 . The particular process employed depends upon a desired depth of analysis, a required level of throughput or other security demands. More specifically, if there is a to need to maximize a probability detection, series processing, such as illustrated in  FIG. 5 , is preferably employed by analyzer portion  78 . Alternatively, analyzer portion  78  can also be programmed to perform parallel processing ( FIG. 6 ) when high throughput is desired. Finally, image processing, illustrated in  FIG. 7 , which digitally removes potentially interfering substances (or areas unlikely to contain the desired sample) from the detection process to compensate for process inconsistencies or background imperfections, can be employed, either alone or in combination with another analysis process. In general, image processing both increases detection accuracy and reduces false alarm rates. 
     As best shown in  FIG. 5 , serial processing involves sequentially passing sample  114  through a chemical application and illumination process. That is, after designating areas of interest A 1 -A 8 , sample collection sheet  55  is moved into analyzer portion  78  where a first chemical application process  140  is initiated. Following application of one or more chemical agents, sample collection sheet  55  is illuminated in step  143 . Other processing steps, particularly the activation of heater  100  to activate a particular applied chemical agent or otherwise aid in analysis, are performed in step  146 . After processing step  146  is complete, an image is acquired by image scanner  89  and analyzed for threat residue in step  149 . This overall process can be repeated one or more times with different chemical applications, depending upon a desired level of accuracy and the particular trace residue of interest. Upon completion of series processing, analyzer portion  78  outputs a result  157  to controller  101 . Result  157  can be presented to the test subject on a keepsake (not shown) that is issued through output portion  45  or, alternatively, passed to a central security station (not shown) for review and further analysis. 
     As stated above, if higher throughput is required, for example in order to expeditiously accommodate larger crowds, analyzer portion  78  can be programmed to perform parallel processing on sample  114 . As best shown in  FIG. 6 , after designating areas of interest A 1 -A 8 , sample collection sheet  55  is passed to analyzer portion  78  for an initial chemical application process step  163 . During chemical application process step  163 , multiple chemical agents  165 - 167  are substantially simultaneously applied to sample collection sheet  55 , even as it passes. Following chemical application process step  163 , sample collection sheet  55  is illuminated in step  175  and subjected to various additional processing steps at  180 , such as the activation of heater  100  to activate the chemical agents. Illumination step  175  and processing steps  180  can be repeated one or more times depending upon the chemicals employed and desired level of accuracy. After illumination and processing steps  175  and  180  are complete, an image is acquired during an image acquisition step  184 . Once the image is obtained, analyzer portion  78  determines whether sample  114  contains a threat residue in step  188 . The result is passed to controller  101  and, in a manner similar to that described above, either imprinted upon a keepsake which is issued to the tested subject or passed to a central control center. 
     Reference will now be made to  FIG. 7  in describing an image processing detection method employed by analyzer portion  78 . In a manner similar to that described above, after designating areas of interest A 1 -A 8 , sample collection sheet  55  is passed to analyzer portion  78 . At this point, a first image capture of sample  114  is performed in step  198 . First image capture  198  is conducted employing white light. Preferably, image scanner  89  is configured to utilize a visible wavelength. The image obtained in step  198  is used to identify any physical contaminants that may be present on sample sheet  55  which might result in false alarms in the final result. Sample collection sheet  55  is then exposed to ultraviolet (UV) light in light proof chamber  82  in step  202 . At this point, it should be noted that all image capture steps could be performed in light proof chamber  82 , with only the particular type of illumination, i.e., white light, UV light, changing as necessary. In any case, while sample collection sheet is exposed to UV light, a second image is captured in step  205 . Preferably, image scanner  89  is sensitive in a wavelength range that is specific for potential interference, such as white light contaminants that may fluoresce when subjected to UV light and contaminates that may absorb UV light. These potential interferences are image captured prior to step  209 . 
     In step  209 , a detection image is captured under the UV light using image scanner  89  which is preferably set to the same wavelength employed when capturing image  205 . However, various other wavelengths can be chosen in order to optimize detecting optical changes consistent with trace explosive residues. In any event, once obtained, the three images are digitally analyzed in digital processing portion  212  for evidence of trace explosives. The images are correlated using one or more common reference points on all images. Preferably, the common reference points are registered in a calibration portion of internal hardware and software, but may also be registered using one or more of designated areas A 1 -A 8  or pre-made marks on sample collection sheet  55 . 
     The first images obtained in steps  198  and  205  are used to identify and remove any visible contaminants from the final image obtained in step  209 . More specifically, the image obtained in step  209  is used to identify and remove any fluorescent and/or UV absorbing contaminants from the final image such that the known and identified contaminants are digitally removed from the detection image. The resulting image is then analyzed for evidence of trace explosive content. Once complete, the result is passed to controller  101  and, in a manner similar to that described above, either signified on a keepsake or passed to a central processing portion. 
     It should be recognized that the security screening center constructed in accordance with the present invention is readily adaptable to various venues and/or security levels employing one or more processing steps in order to ensure a high level of reliability while, simultaneously, increasing throughput through screening center  2 . In addition, by providing feedback to test subjects to ensure proper sample recovery and employing a system that focuses on particular areas of a sample that are most likely to contain threat residue, the security system increases the likelihood of identifying potential threats. Furthermore, it should be realized that sample processing in accordance with the invention can be done on individual samples, such as with the various process steps described above being performed on a moving sample or in sample batches with multiple samples being concurrently processed. 
     Although described with reference to preferred embodiments of the invention, it should be readily understood that various changes and/or modifications can be made to the invention without departing from the spirit thereof. In general, the invention is only intended to be limited by the scope of the following claims.