BACKGROUND ART There are a number of situations in which surveillance of a person or group of persons is necessary. A obvious example is use in law enforcement applications where the movements of an undercover agent must be monitored, or when low-risk criminals are sentenced to periods of home detention. there are also many applications for the monitoring of objects. For example, illicit drugs used by law enforcement officials in sting operations must be tracked to provide a chain of possession.

Another example is the tracking of baggage and passengers within the zone of responsibility of a given airport. More specifically, a system is needed for identifying a passenger early in the airport check in procedure, processing that passenger and his or her baggage, including carry-on items, and reconciling the person and items (baggage/packages) as they arrive at the destination. This system could be applied to any means of public transportation, including in train stations and bus stations. In the context of airport security, such a system could accomplis the total accountability desired by the airport, the airlines, and the federal entities that regulate both. The example of airport security will be used herein to facilitate disclosure of the present invention. The present invention is not limited to this specific application, however, and is contemplated for use with any application in which persons or objects are tracked for any purpose.

DISCLOSURE OF THE INVENTION The present invention utilizes a radio frequency identification (RFID) process based on an RFID tag to accomplis the tracking function. The tag has a base which may take the form of a plastic card, much like a credit card or identification badge, a heavy paper card, such as an airline ticket or baggage tag, or any other electrically non-conductive material. Small metal particles are distributed, preferably embedded, in the base. These small particles are preferably metal-coated glass rods, cut to size suitable for use as bipolar antennas matched to a predetermined frequency. The particles are distributed on the base in a random fashion. The physical dimensions of the finished RFID tag, combined with the unique random distribution of the metal particles, makes each RFID tag completely distinguishable from any other RFID tag. The tag can then be put into a field of RF energy, which will react with the randomly- distributed antennas in the tag to establish a characterization of the tag.

Because of the random distribution of the antennas on the tag, and the resulting unique nature of each individual tag, each tag will exhibit a unique signature when energized. Thus, each time the tag is illuminated by energy of a particular frequency, the signature of its associated reflected energy can be read to uniquely identify the tag. Such tags can be affixed to baggage, passenger tickets, and employee badges in order to track these entities within the airport.

BEST MODE FOR CARRYING OUT THE INVENTION The frequency for tag illumination may be chosen to suit the environment of the particular operation. For example, in an airport, where there is a significant amount of communications equipment already in operation, a frequency of 25 Ghz or higher would be preferable. At such a frequency, little or no interference with existing equipment is likely. Further, the nature of high frequency waveguide construction is such that the aperture of the horn device acts as its own cutoff for frequencies that are 18 Ghz or lower. A field may therefore be generated, flooding a predetermined area with the selected frequency. When each tag is fabricated, a percentage of energy generated and directed toward the tag is reflected by the particles in the tag to generate the

unique signature for the tag. This signature is recorded as a reference identification, which is stored and indexed as a known pattern and value. Later, when the tag is in use and is moved about the area of concern (for example, an airport), fields of RF illumination may be generated to produce a known constant reflected cone of energy. When a particular tag moves into the established cone of energy, the tag is illuminated and may be identified by its unique signature. Because the tag is physically stable and because the reflected energy is at a constant frequency, the signal reflection is also consistent. At frequencies in the Ghz range, the identification process is not hampered by any material in the line of sight. The high frequency,"flooding signal"is used as a gate to track the passage of a particular tag, and the resulting signature can be "seen"through clothing and through flesh. For example, a tag formed on an airline ticket in a shirt pocket is readable from a distance of approximately 10 meters. Thus, according to the system of the invention, RF energy is used to uniquely identify a passive tag.

The tag is given an index number associated with a travel ticket, which is also indexed to a sales or transaction number, for a corresponding passenger.

The tracking of the digital information in this manner is in itself a significant improvement over the bar code and hand written tagging process for baggage handling that is in practice today. To make the individual identification portion of the accountability loop more reliable, an analog function (preferably biometric) would positively identify the individual associated with the ticket and the baggage. The analog identification process will preferably be unobtrusive, and covert.

That is, passengers entering a federally-controlled enclave such as an airport are necessarily subject to scrutiny for a wide range of security reasons.

Overt technologies making use of palm prints, fingerprints, and the unnerving retinal eye scan, do not cover the need for interception and surveillance that are required by law enforcement and security personnel. Facial thermograms, however, provide reliable identification information without the requirement of an obtrusive data collection process. Each person has a vascular pattern in the facial area that is unique. Even twins have distinguishable facial vascular

patterns. vascular flow is primarily dependent on diet, metabolism, and a variety of other physical attributes particular to an individual. A facial thermogram process, coupled with the RFID process, provides a combination of identification and tracking capabilities that can easily be controlled within a specific physical environment such as an airport.

Thus, a passenger purchasing an airline ticket at a ticket counter, or checking in on arrival at an airport, will be issued an airline ticket that includes the antenna particles such that it also functions as an RFID tag. Alternatively, such a tag may be affixed to the ticket in some manner. The passenger's facial vascular pattern may be thermally scanned at the counter, and the information derived from the scan can be linked to the reference signature associated with the tag. Any baggage checked or carried by the passenger will receive a tag that is also linked to the thermogram information. Sensors that illuminate the tags and detect the tag's signature can be placed at exits to the airport. Thus, if a passenger checks baggage on a flight, or leaves a carry-on bag in the airport, and then leaves the airport and does not board the plane for the flight was booked, the luggage corresponding to that erstwhile passenger can be taken off the plane or removed from the airport as a potential security risk. The particular baggage can be easily found by searching for the unique signature of the tag associated with the baggage.

If the passenger is a legitimate traveler and actually completes the flight, the system of the present invention can also help prevent his or her baggage from being stolen. The linked tag signature (s) and thermograph information can be electronically provided to the destination airport. In the baggage claim area, this can be used to ensure that the person leaving with the baggage is the same person who checked in the baggage, providing personal security for the passenger.

INDUSTRIAL APPLICABILITY As stated previously, the present invention has myriad other applications to situations where the tracking of people and/or objects is useful. In all such applications, the linking of a person's identifying physical information with a reliable means of identifying and tracking an associated object adds a level of reconciliation that greatly improves the state of surveillance techniques.