Abstract:
A computer-controlled laser etching probe etches a firearm-identifying indicia such as a barcode encoded serial number into the bore of a firearm. Owner registration data coupled with the serial number is stored in a central database. A computer-controlled scanner reads the barcode from a bullet fired from an etched firearm for comparison with registration data in the central database, thereby identifying the registered owner of the firearm from which the bullet was fired.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to a method and system for marking the inner surface of the barrel of a firearm with an identifying indicia for transfer to a bullet passing therethrough, reading the indicia from the bullet and identifying the firearm and, in particular, to the modification of the inner surface of a firearm barrel using a laser for the purpose of producing one or more areas of permanent grooves, which impart firearm data onto rounds passing through the barrel in contact with the inner surface of the barrel to form a barcode-like pattern which may be read by a barcode scanner and matched to the firearm. 
     In order to link a bullet with the firearm that fired it, it is known in the art to examine a bullet, usually comparatively with another bullet, each with small, irregular microscopically viewable markings imparted during firing to determine a similarity between such markings whereby to support a conclusion that both bullets were fired from the same firearm. 
     In order to facilitate ballistic identification procedures with only the fired bullet available, various systems have been proposed in which bullets are marked by placing a channeled ring containing a number of dye bars in a groove in the barrel, which impart markings to the bullets which pass over them. The dye bars are assembled in different combinations according to a preset code which corresponds to the firearm&#39;s serial number. Other systems have been proposed in which the identifying markings are an integral part of the barrel and bore surface so that they cannot be removed without damaging or disabling the firearm. Among the problems with such systems is that the identifying marking elements must be incorporated during manufacture of the firearm. Thus, identification of bullets fired by guns currently in use must be done the traditional way, which requires not only the bullet, but the gun to fire another bullet for comparison with the bullet in question. 
     SUMMARY OF THE INVENTION 
     It is therefore, the primary object of the present invention to provide a method and system for the placing identifying markings on the bore surface of a barrel of a firearm, transferring the markings to a bullet fired therefrom, scanning the markings on the bullet and identifying the registered owner of the firearm from which the bullet was fired. 
     Another important object of the present invention is to provide a method and system for etching the bore of a firearm barrel as aforesaid, which uses a laser probe inserted into the barrel. 
     Yet another important object of the present invention is to provide a method and system for etching the bore of a firearm barrel as aforesaid, with a barcode or other identifying indicia. 
     Still another important object of the present invention is to provide a method and system for etching the bore of a firearm barrel as aforesaid, which may be adapted for different firearm models. 
     Another important object of the present invention is to provide a method and system for etching the bore of a firearm barrel with an identifying indicia as aforesaid, and entering registration data into an associated computer indicative of the owner of the firearm corresponding to the identifying indicia. 
     Yet another important object of the present invention is to provide a method and system for etching the bore of a firearm barrel as aforesaid and transferring registration data entered into an associated computer to a central database for subsequent comparison with scanned data and retrieval. 
     Still another important object of the present invention is to provide a method and system for scanning a bullet marked with an identifying indicia from an etched firearm as aforesaid, which translates the indicia into a serial number or other corresponding alpha-numeric digits. 
     Another important object of the present invention is to provide a method and system for scanning a bullet marked with an identifying indicia from an etched firearm as aforesaid, and requesting registration data corresponding to the indicia from a central database for display and identification of the registered owner of the etched firearm. 
     These and other objects of the invention are achieved by a computer controlled laser system adapted to etch the bore of a firearm using an etching probe inserted into the firearm barrel. Firearm identifying data, such as a serial number, are etched in the bore of the firearm in the form of a barcode or other identifying indicia. Registration data corresponding to the owner of the firearm and the serial number or other firearm identifying data are entered into a computer and transferred to a central database. A bullet fired from an etched firearm is marked with the etched barcode. A computer controlled scanning system reads the barcode and translates it into a serial number or other firearm identifying data for comparison with serial number stored in the central database. 
     Other objects and advantages of the invention will become apparent from the following description taken in connection with the accompanying drawings, wherein is set forth by way of illustration and example, an embodiment of this invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is diagrammatic view of the barrel-marking system of the present invention. 
     FIG. 2 is an front elevational view of a barrel-etching assembly. 
     FIG. 3 is a top plan view of the barrel-etching assembly shown in FIG.  2 . 
     FIG. 4 is a side view of a barrel clamping apparatus for proper positioning of a barrel to be marked, shown in an open position. 
     FIG. 5 is a side view of the barrel clamping apparatus of FIG. 4 shown in a closed position. 
     FIG. 6 is a side cutaway view of the clamp centering apparatus. 
     FIG. 7 is a top cutaway view of the clamp centering apparatus shown in FIG.  6 . 
     FIG. 8 is a schematic of the microprocessor controlled engraver circuit. 
     FIG. 9 is a diagrammatic illustration of a gun with the barrel cut away to show the barcode markings on the bore of the barrel. 
     FIG. 10 is a diagramatic illustration of barcode markings on the bore of the firearm barrel of FIG.  4 . 
     FIG. 11 is diagramatic illustration of barcode markings on a bullet. 
     FIG. 12 is diagramatic illustration of the barcode bullet scanning system for scanning and identifying a marked bullet. 
     FIG. 13 is a diagrammatic illustration of a scanner for reading the barcode on a marked bullet. 
     FIG. 14 is a schematic of the scanner circuit. 
     FIG. 15 is a functional block diagram of the engraver control software. 
     FIG. 16 is a functional block diagram of the scanner control software. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Turning more particularly to the drawings, FIG. 1 illustrates a firearm barrel-marking system of the present invention including a barrel etching assembly  20  shown mounted in cabinet  22 . One or more electronic controller boards  24  control the output of laser tube  26  which is connected through optical fiber  28  to etching assembly  20  and the positioning of laser tube  30  to etch the bore of gun  32  held in clamp  34 . It is to be understood that a mirror system may be used in place of optical fiber  28  to direct the output of laser tube  26  to etching assembly  20 . 
     Input and control data is transferred to boards  24  over parallel line  36  from computer  38 . Computer  38  may be a personal computer having a modem and an attached printer  40 . Serial number and registration data for gun  32  may be entered into computer  38  which are transferred over line  36  to control boards  24  to be used for input and control parameters. Registration data may be entered into computer  38  transferred from computer  38  through communications link  42  to computer system  44 . Computer system  44  may consist of a server  46  and one or more databases  48  to store the firearms registration data. Computer system  44  may be controlled and operated by a federal law enforcement agency such as the FBI for registration and identification of a firearm  32 . 
     Referring to FIGS. 2,  2   a  and  3 , laser etching assembly  20  includes frame  50  which supports laser tube assembly  52 . Laser tube assembly  52  is secured to upper  54  and lower  56  support cross members which slidably engage guide rods  58 . 
     Laser tube assembly  52  includes a threaded outer cylinder  60  which extends between and is secured to upper  54  and lower  56  support cross members. A reflector positioning tube  62  is rotatably secured within cylinder  60 . Reflector positioning tube  62  includes coolant tubing  64 , laser tube  66 , probe  30  and reflector  70 . Laser light  72  is injected into laser tube assembly  52  from fiber optic line  28  through connector  74  into tube  66 . 
     An upper vertical alignment gear  76 , which engages the threads of cylinder  60  is controlled by stepper motor  78 . Gear  78  is housed in center frame member  80 . Limit switches  82  and  84  limit the vertical displacement of laser tube assembly  52  between the center frame  80  and lower of member frame  50 . Stepper motor  78  precisely controls the placement of probe  30 . Limit switch  84  is also used to indicate when probe  30  is in the starting or default position. 
     Rotation of laser tube assembly  52  is accomplished by a lower worm gear  86  secured to laser tube assembly  52  and engaged by step motor  88 . A limit switch  90  may be used to limit rotation of laser tube assembly  52  to prevent damage to optical fiber  28  and to indicate when laser tube assembly  52  is rotated to the starting or default position. 
     Referring to FIGS. 4 and 7, a centering clamp assembly  100  is shown which includes a barrel clamp  102  with front  104  and rear  106  clamping members which are pivotally secured together by hinge  108 . Clamping members  104  and  106  include channels  110  and  112  respectively, which are shaped to accept a gun barrel placed in clamping assembly  102 . An orienting key channel  114  for receiving a gun sight is located toward the upper end of channel  112 . When barrel clamp  102  is closed, channels  110  and  112  are in axial alignment and form a barrel-holding and aligning cylinder. Barrel clamp  102  may be locked in the closed position with latches  116  and  118  to secure a gun barrel  121  in place for etching. 
     Referring to FIGS. 6 and 7, alignment of clamping assembly  100  may be adjusted by alignment assembly  120  to axially align the bore of barrel  121  with etching probe  30  (See FIGS.  1  and  2 ). Mounting pegs  122  extending from the back of barrel clamp  102  are seated in apertures  124  on face plate  126  and are held in place by gravity. Other methods of holding barrel clamp  102  to face plate  126  may be used such as bolts or other fasteners. The barrel clamp  102  may be quickly changed and sized for specific weapons which may require different of barrel clamps if different gun models are to be etched. In a manufacturing facility, where the same or similar gun is made with the same size barrel and bore, the barrel clamp  102  may be more permanently installed. 
     Because different guns have different bores, alignment of barrel clamp  102  may require adjustment to bring barrel  121  into axial alignment with etching probe  30 . Face plate  126  of alignment assembly  120  is secured to a clamp adjustment slide  128  which may be adjusted along generally parallel rods  130  which are secured between end plates  132  and  134 . Stepper motor  136  drives screw  138  which interfaces with threaded insert  140  secured to clamp adjustment slide  128 . Limit switches  142  and  144  cut power to stepper motor  136  when either is engaged to limit movement of clamp adjustment slide  128 . 
     Referring to FIG. 8, a laser etching controller circuit is generally indicated by reference number  150 . Power supply  152  includes a center tapped transformer  154  which converts 120 volts AC to +5 volts DC and +12 volts DC using bridge rectifiers  156  and  158  respectively. 
     Microprocessor  160  controls stepper motors  78 ,  88  and  136 . In the preferred embodiment, a 16-bit Intel 8088 microprocessor may be used to control the stepper motors. Because of the relatively limited processing load on the microprocessor, processors with relatively limited processing capabilities and speed may be used. However microprocessors with greater capabilities may be used. 
     In the preferred embodiment, stepper motor  78 ,  88  and  136  are generally unipolar permanent magnet motors with center tapped windings, as shown in FIG. 8, with an angular resolution of 0.9 to 0.45 degrees or 400 steps per resolution to 800 steps per revolution respectively. Higher resolution motors may be used to encode more data into the bore of a gun. 
     Setup and control data is transferred from PC  38  over parallel line  36  to UART  162  which is transferred to microprocessor  160  over line  164 . Setup data for a specific gun model is stored in memory  166  in a look up table which is retrieved by microprocessor  160  over address line  168  in response to setup and control data transferred from PC  38 . 
     Stepper motor  78  may require up to 2 amps of current to move laser tube assembly  52 , thus, PNP transistors  172 ,  176 ,  180  and  184  may be power darlington transistors with a current gain of over 1,000 such as an SK3180 transistor. Using a 470 ohm resistor for bias resistors  170 ,  174 ,  178  and  182  permits a ten miliamp current to flow to the respective transistor  172 ,  176 ,  180  and  184  to allow the transistor to switch a few amps of current through the stepper motor  178  winding as controlled by microprocessor  160  on output lines 0-3. Because each winding of stepper motors  88  and  136  draw less than 500 milliamps, darlington transistors  188 ,  192 ,  196 ,  200 ,  204 ,  208 ,  212  and  216  and associated resistors  186 ,  190 ,  194 ,  198 ,  202 ,  206 ,  210  and  214  may be incorporated into an array such as the ULN200x family of darlington arrays from Allegro Microsystems which is also available as the DJ200x family of arrays from National Semiconductor. The UDN2547D Quadpower Driver from Allegro Microsystems will handle all four windings of common stepper motors such as stepper motors  88  and  136  for example. 
     Microprocessor  160  also controls laser tube  26  through transistor switch  218  which energize relay  220  to switch power from source  222  to power transformer  224  which provides three KVAC to laser tube  26 , and to incandescent heater  26 . Laser output from laser tube  226  is injected into fiber optic line  28 . 
     Referring to FIGS. 1-11 and  15 , to etch the bore of hand gun  32  for example, hand gun  32  is placed into clamp assembly  102  with the gun sight  250  on barrel  252  aligned with channel  114 . Then, clamp assembly  102  is closed and latched around gun barrel  252 . 
     The model number, make and serial number of gun  32  is entered into computer  38  and this data is transferred over line  36  to UART  162  and then to microprocessor  164 . The registration data is stored in RAM  350 . Microprocessor  160  reads the gun parameters from memory  166  and correlates the data and the barcode geometry  352 . Based on the set up parameters, if necessary, the location of clamp assembly  102  is adjusted by commanding stepper motor  136  to rotate in either direction to bring barrel bore  254  into axial alignment with laser etching probe  30 . After the hardware is calculated  354 , safety switches are checked  356  to ensure that the cabinet  22  door is closed for example. If the cabinet  22  door is not closed the engraver is reset  358  and processing returns to the start. 
     If the safety switches are set  356 , the engraver is moved into position  360 . Vertical positioner worm gear  76  powered by stepper motor  78  moves laser control tube assembly  52  into the start position under supervision of microprocessor  160  until closure of switch  84 . Additionally, laser tube  62  is rotated by stepper motor  88  again under supervision of microprocessor  160  until closure of switch  90 . Etching probe  30  is now in place in the bore  254  of barrel  252 . 
     Microprocessor  160  retrieves data concerning firearm configuration, if necessary and specific barcode instructions from RAM  66  or through UART  162  from PC  38 . Once laser etching probe  30  is in position, microprocessor  160  sends a signal to transistor  218  to close relay switch  220  and activate resistive heating element  226  used in laser tube  26  to activate the laser  362 . Microprocessor  160  also commands a coolant pump (not shown) to begin circulating coolant through passages  64  in order to maintain stability of laser reflector  70  while in contact with the laser beam  72 . 
     After laser tube  26  has reached operational temperatures, a one micron 30-watt carbon dioxide laser is output from laser tube  26  into fiber optic line  28 , which is injected into laser tube  66 , reflected from laser reflector  70  and transmitted as beam  72  into the bore  254  of gun  32 . Laser tube  26  is switched on and off while laser etching probe  30  is rotated lowered rotated again in the opposite direction and raised continuously forming grooved bar coding dyes  256  in the bore  254  of barrel  252 . The laser is activated  362  and microprocessor  160  controls the stepper motors  364  to form a groove in bore  254 . At the end of each groove or barcode strip  256  the laser is deactivated  366  and microprocessor  160  checks to determine if the barcode is complete  368 . If the barcode is not complete, the engraver is positioned  360  to the beginning of the next stripe and the process repeats. 
     The grooves of barcode  256  may be from 10 to 50 microns in depth. The serial number of 32 is encoded into the space and bars of various width of barcode  256 . The number of characters represented in a linear inch of a barcode is called the barcode density, which depends on the barcode symbology. For example, using Code  39 , 9.4 characters can fit in one inch. The resolution of a barcode is dependent on the narrowest element of a barcode. Because of the relatively small circumferential area available in bore  254 , barcode  256  is compressed or scanned from the standard barcodes known in the art. For example, interleaved 2 of 5 which is capable of encoding up to 30 digits may be scaled from 17.8 characters per inch to 17.8 characters per 0.125 inches or 142.2 characters per inch. Other codes could be used such as Code  128  which can encode the entire 128 ASCII character set. 
     By way of example, a 38-caliber head gun has a bore circumference of approximately 1.2 inches. Using an 800 steps/revolution stepper motor, the angular distance is 0.45 degrees/step or approximately 0.0015 inches/step. For a barcode 0.125 inch wide and using interleaved 2 of 5 scaled by eight, 17 characters can be encoded. There are approximately 83 steps in 0.125 inch. Using a stepper motor with an angular resolution of 3200 step/revolution, 71 characters can be encoded a 0.125 inch barcode using interleaved 2 of 5 with a step spacing of 0.000375 inch. 
     Once barcode  252  is completed  368 , microprocessor  160  commands stepper motor  78  to withdraw the etching probe from the barrel  370  by raising laser tube assembly  52  until switch  82  is engaged. Firearm  32  may now be removed from clamp assembly  102 . Information regarding the serial number make and model of gun  32  may now be transferred from computer  38  to law enforcement system  44  over communication link  42  to be stored in databases  48  connected to computer  46 . It should be understood that data from more than one gun may be transmitted together to computer system  44 . 
     Referring to FIGS. 9-11, barcode  256  in bore  254  is etched parallel to the rifling in bore  254 . A bullet  258  fired from gun  32  marked with barcode  256  will have the barcode transferred to the bullet as indicated by  260 . Thus, any bullet  258  fired from gun  32  may be traced by barcode  260  without access to gun  32 . 
     Referring to FIGS. 11-14 and  16 , to read barcode  260  on bullet  258 , bullet  258  is placed in scan bed  274  in barcode bullet scanner  272 , which is linked to computer  270 . 
     Microprocessor  312  activates the scanner and detector current  380 . Laser diode  278  outputs a 5 milliwatt laser  280 , which is reflected from mirror assembly  282  rotated by motor  284  through beam focusing lens  286  and reflected from bullet  258  through light condensing lens  288  onto phototransistor  290 . The diameter of the beam incident on bullet  258  should be at least one half the spacing of the individual bars of barcode  260 , which may be approximately 20 to 50 microns. 
     Scanner circuit  300  as shown in FIG. 14, includes transformer  302  and full wave rectifier  304  which provides 5 volts DC for circuit  300 . UART  308  provides an interface between 8088 microprocessor  312 , and computer  70  over lines  306  and  310 . Microprocessor  312  controls scanner bed stepper motor  314  and mirror assembly motor  248 . Upon command from control buttons  273  on the front of scanner  272  or from computer  270 , microprocessor  312  activates transistor  316  to enable laser diode  278 . Bullet  258  is rotated in scanner bed  274  so that the entire width of barcode  260  may be scanned. Light reflected from barcode  260  on bullet  258  is received by phototransistor  290 . The signal from phototransistor  290  is input to amp  318  and fed through A/D converter  320  and stored in RAM  382 . Microprocessor  312  converts the encoded signal into digits  384 , by a method known in the art. If valid data is not detected  386 , bullet  258  is scanned again. Scanning may be attempted two or more times before scanning is abandoned and an error message displayed. 
     If valid data is detected, the data is output on line  322  to UART  324  and transferred on line  326  to display  328  on the front panel of scanner console  272 . The digits is also transferred via UART  308  over line  306  to computer  270 , which are assembled into a serial number. The serial number may now be transmitted over communication link  330  to law enforcement computer system  44 , which includes computer  46  and databases  48  and the file corresponding to the data is requested  388 . The serial number is matched with data in databases  48  and the associated registration information is transmitted back to computer  270  and displayed  390 . This information may then be printed on laser printer  276 . Accordingly, the bullet may be traced to the firing gun and the registered owner of the gun.