Abstract:
A method to generate an optical signature of a coin is disclosed. A plurality of parameters are generated and recorded related to rotational positions around the circumference of a coin. The data from these parameters are combined to produce a searchable value.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority from provisional application Ser. No. 61/046,347, filed Apr. 18, 2008. 
    
    
     TECHNICAL FIELD 
     The present invention relates generally to coin collecting and valuation of coins, and more particularly, to a method and resulting file structure to uniquely identify data files associated with coin light scattering measurement. 
     BACKGROUND 
     The interest in the collection and conservation of coins and related objects has been historically considered a personal interest activity, with little formal standards or controls concerning the trading of coins. The recent rise in the value of coins compared to earlier levels has promoted the trading of coins to a higher degree of professional structure, most significantly by the advent of commercial third party coin grading services who have developed systems to apply a widely accepted quality grade (based on a numerical scale from 1 to 70 with 70 being the highest quality). After examining and determining the grade of a coin, the commercial services place the coin in a clear plastic holder in which a grade label with a reference barcode is affixed. The clear plastic holder is then ultrasonically welded around the coin, thus permanently linking the grade to the coin within the case. A barcode is linked to the database which can be searched to confirm that the referenced coin was graded by the commercial service, along with some additional transaction details such as the date, place, company grading the coin, etc. 
     The grading service charges a fee for the provided services and gives a warranty of grading accuracy as part of the transaction value. The result of this commercial service is to allow the plastic encapsulated coins to be more readily traded as their trade value is directly linked to the professional quality grade shown on the plastic holder. 
     However, the current commercial grading services can lack repeatability and consistency. Further, current services are unable to prevent “grader shopping” in which a coin owner may specifically hunt for the highest value for a given coin by removing the coin from the plastic holder and re-submitting it since there is currently not a mean to identify a specific coin outside of the labeled box or other rigorous objective means for identifying a specific coin. 
     Any such objective means for coin grading would require a method to compare coin specific physical data for the identification of coins. 
     SUMMARY 
     In various exemplary embodiments, a method to identify coins is disclosed, in which data from various sources is used to provide a data signature of a coin based on uniquely detectable physical properties. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The appended drawings illustrate exemplary embodiments of the present invention and must not be considered as limiting its scope. 
         FIG. 1A  is an exemplary embodiment of a simplified schematic of an optical light scattering apparatus for characterizing coins. 
         FIG. 1B  is an exemplary histogram obtained from a physical defect sensor used in conjunction with the light scattering apparatus of  FIG. 1A . 
         FIG. 2  is an exemplary color histogram obtained from a color sensor used in conjunction with the scattering apparatus of  FIG. 1A . 
         FIG. 3  is an exemplary coin thickness histogram obtained from a thickness monitor used in conjunction with the scattering apparatus of  FIG. 1A . 
     
    
    
     DETAILED DESCRIPTION 
     The use of one or more sensors capable of making automated quantitative measurements of various physical characteristics of coins are combined using one or more mathematical equations to distill, display, and store the quantitative measurements into a single digital file. The digital file represents the identification of the measured coin. Moreover, the digital file is structured allowing an efficient means of searching a high volume of files of other coin data to find the file of a particular coin should the coin be re-analyzed at a future date. 
     The coin identification algorithms described herein allows development of a complete coin identification system, thus adding value to the sale and ownership of coins for both personal and commercial uses. Coin identification, as noted herein, uses a system architecture configured to accurately and repeatably generate light scattering measures or/and surface profilometry measurements based upon physical properties of any given coin. Either manipulated or raw measurement data from these measurements are captured and stored into one or more digital files. 
     A mathematical algorithm, described below, is applied to reduce the data into a single identification template file. The template file is referred to as a “CoinPrint” herein. The CoinPrint file is then stored in any appropriate database (e.g., any number of digital, optical, or other storage systems known in the art including hard drives and hard drive arrays, CD-ROM or DVD discs, etc.) that allows subsequent searching and retrieval of CoinPrint templates. 
     A simple and intuitive user interface allows both capture of data from coins and searching and retrieval for conducting searches of previously scanned coins. A design for the user interface is known in the art and may be readily produced by applying principles and algorithms described herein. 
     With reference to  FIG. 1A , an exemplary embodiment of a simplified schematic of an optical scattering apparatus  100  includes a rotating sample platform  101  configured to accept coins undergoing measurement, a sample coin  103 , and a light source  105 . The light source  105  may be a laser, light-emitting diode (LED), a broadband light source, or a variety of light-producing sources (or other sources producing electromagnetic energy) known in the art. In a specific exemplary embodiment, the light source  105  includes a plurality of LEDs, at least one each to generate the primary spectrum of red, green, and blue (RGB). 
     The optical scattering apparatus  100  further includes beam forming optics (not shown but known in the art), allowing a line of light to form on a steering mirror  107 . The steering mirror  107  may be a vibrating front-surface mirror, a rotating polygonal mirror, or any number of beam-steering types of optics for producing a line of light. A telecentric scanning mirror  109  may optionally be used in conjunction with or in place of the steering mirror  107  and the beam forming optics directing a line of light  111  across the surface of the sample coin  103 . At a predefined point  113  on a surface of the sample coin  103 , an intensity measurement is taken by a sample imaging optic  115 . 
     The sample imaging optic  115  may be, for example, a lens or another light collection element optical train or single optical element placed in front of a CMOS sensor or CCD sensor array. In other embodiments, the sample imaging optic  115  may be either a single sensor or a group of sensors. In any case, the sample imaging optic  115  is configured to record a plurality of intensity measurements of either scattered or reflected light from the surface of the sample coin  103 , all in one or more colors or, alternatively, a grey-scale intensity. At least one “point” (e.g., a pixel) of light will be imaged from the predefined point  113 . As the sample coin  103  is rotated through a 360° arc, the predefined point  113  traces a circle on the surface of the sample coin  103 . 
     With continuing reference to  FIG. 1A , the optical scattering apparatus  100  further includes an automatic focusing element  117 . Although shown as a separate element, the automatic focusing element  117  may be incorporated as a portion of the light source  105 . Automatic focusing (AF) lenses and related systems are known in the art and may be employed to keep an output beam focused as the beam is directed over the topography of a typical coin. Automatic focusing is not required in many configurations, such as when using a laser light source. The abolute thickness and thickness variation measurements of the sample coin  103  could also be determined (e.g., as measured with reference to a height of the coin measured in reference to a height of the rotating sample platform  101 ) by noting electrical current present in AF coils. Thus, the automatic focusing element  117  serves as a type of optical profilometer. A spatial frequency (i.e., an inverse spatial wavelength) and a resulting spatial bandwidth may be determined based upon a focused beam diameter and a maximum scan length of the beam over the surface of the sample coin  103 . 
     With reference now to  FIG. 1B , an intensity plot  150  shows a recorded output  151  of intensity level from the sample imaging optic  115 . One parameter that may be extracted from the sample imaging optic  115  is a physical defect sensor (PDS) mapping of intensity mapping due to surface damage of the sample coin  103 . The surface damage may be caused by scratches, dents, or other random surface variations. The recorded PDS output may be sampled at a number of locations. In a specific exemplary embodiment, a maximum intensity level of the recorded output  151  is sampled each 10° of rotation. Thus, 36 independent values of intensity level are recorded by this scheme. One unique parameter used in the labeling and retrieval algorithm, discussed in more detail below, consecutively lists each of the 36 values from the PDS mapping as:
 
PDS=n p1 , n p2 , n p3 , . . . , np 36  
 
     With reference to  FIG. 2 , an exemplary surface color histogram  200  displays an intensity level for each of the three LEDs or other tri-color light sources as collected from the surface of the sample coin  103  ( FIG. 1A ). In this exemplary embodiment, the intensity level for each group of three colors  201  is recorded at 30° increments. 
     The intensity levels are collected in a similar fashion as the total intensity levels of  FIG. 1A . However, the exemplary surface color histogram  200  displays an intensity level for each RGB light source. Alternatively, if the optical scattering apparatus  100  uses a broadband or white light source, the exemplary color histogram  200  is displaying an intensity level for each RGB sensor on, for example, a color CMOS or CCD display. 
     Thus, taking one RGB measurement every 30° produces 12 independent values of three measurements each. Thus, a second unique parameter used in the labeling and retrieval algorithm lists each of the 12 values from the surface color histogram (SCH) as:
 
SCH=n s1 , n s2 , n s3 , . . . , n s12  
 
where each value, n sx , represents three separate values.
 
       FIG. 3  is a thickness graph  300  showing coin thickness as a function of rotational angle. The thickness graph in the exemplar shows a thickness value recorded every 30° of rotation. Values of thickness are measured using current readings from the automatic focusing element  117  ( FIG. 1A ). A skilled artisan will recognize how to calibrate and convert the current readings into thickness measurements. 
     Similar to the manner with which PDS and SCH are recorded, a coin thickness measurement (CTM) taken every 30° produces 12 independent values. A third unique parameter used in the labeling and retrieval algorithm lists each of the 12 values from CTM as:
 
CTM=n c1 , n c2 , n c3 , . . . , n c12  
 
     An exemplary algorithm for producing a CoinPrint template value thus uses the physical parameters (i.e., measurements) from a particular coin is used to derive a unique value for each and every coin scanned. The algorithm is thus designed to be scalable to take inputs from a plurality of different sensors (or different portions or values from a single sensor), each potentially having very diverse file structures, and reducing each of these values into a simple template file name. The template file name is therefore representative of several physical measurement values. 
     A CoinPrint template value is therefore a function of the three parameters selected and may take the form of:
 
 CPT=f [(α· PDS )+(β· SCH )+(φ· CTM )]
 
     An actual file name may be constructed in accordance with the functional relationship of three parameters as stated above. In a specific exemplary embodiment, after substituting the individual measurement values, the file name may take the form of: 
     
       
         
           
             
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     As will be immediately recognizable by a skilled artisan, values for each of the constants α,β, and φ may be selected in a variety of ways. Each of the constant values may be selected to be any real number, including integers and real values, both greater than or less than “1.” The number of significant figures is chosen such that at least one significant figure exists for each of an anticipated number of coins that are scanned, stored, and retrievable from a database. For example, if an anticipated number of coin templates to be stored is one billion (i.e., 1×10 8 ), then a value of CPTF is selected to have at least 8 significant figures. 
     In another specific exemplary embodiment, the CoinPrint template output file may optionally take the form of
 
CPTF (2) =PDSxxxxxxxx.SCHyyyyyyyy.CTMzzzzzzzz
 
thus retaining parseable, discrete values for each of the three measured parameters.
 
     One specific benefit of the CPTF value is creation of a file template structure, capable of being parsed, and allowing a flexible application of both contemporary and future sensor configurations in a scattering coin apparatus. The algorithm structure defined herein further allows backward compatibility in the future when correlating files with sensor measurements taken today. 
     The search algorithm may therefore parse the CoinPrint template database file to separate individual reduced sensor values allowing parallel and independent database searches of each parameter. The output file is then constructed from the best matches of the individual parameter factors by cross-matching to parallel parameter files. 
     An exemplary file structure may be maintained on either a local or remote database as shown in Table 1, below. 
     
       
         
               
               
               
               
               
             
           
               
                 TABLE 1 
               
               
                   
               
               
                   
                   
                 Coin 
                   
                   
               
               
                 Record 
                   
                 Grading 
                 Date 
                 Other 
               
               
                 No. 
                 CPTF (1)  Value 
                 Barcode 
                 Recorded 
                 Comments 
               
               
                   
               
             
             
               
                 0001 
                 12305243 
                 1257895 
                 Dec. 31, 2008 
                 note 1 
               
               
                 0002 
                 17585521 
                 1585934 
                 Nov. 11, 2008 
                 note 2 
               
               
                 0003 
                 99812220 
                 1998246 
                 Apr. 18, 2008 
                 note 3 
               
               
                   
               
             
          
         
       
     
     Alternative coin scanning systems exist, such as those shown in co-pending provisional patent application 61/046,336, hereby expressly incorporated by reference for all purposes herein. This system illustrates a device for detecting light scattering from a coin surface. This scattering is detected in eight channels by eight pairs of photo detectors in a linear detector array. An optical encoder correlates the detection data with the rotation of a coin on a turntable. 2500 readings are made during a single rotation. The resulting information may be stored in tabular form: columns 1-8 for each pair of detectors and rows 1-2500 storing the reading at each rotational increment. The rotation is effected by a precision motor and each reading is integration from the detector for an interval. This would produce about 80 kilobytes of data, 10 k for each channel. This table could then be stored. In this instance, each “parameter” could be each channel of the scan. 
     As above, the data from a channel could then be transformed using a mathematical formula. For example, in a channel for the detection of scattering, in the fluxuation of light scatting during a coin rotation, the high and low points and the spacing between these points could be used for comparison to other data sets in data storage. This provides a rapid means for comparison that would not be dependent on the initial orientation of the scan about the diameter of the coin. The scan of the same coin rotated 90 degrees should produce the same pattern of low and high scatting measurements the same distance apart. This pattern would form the “coinprint”. 
     The present invention is described above with reference to specific embodiments thereof. It will, however, be evident to a skilled artisan that various modifications and changes can be made thereto without departing from the broader spirit and scope of the present invention as set forth in the appended claims. For example, particular embodiments describe particular numbers recorded from particular rotational intervals. A skilled artisan will recognize that other measurement numbers may be used as well and combined in other ways. Further, the measurement values could be taken from values stepped over the coin in ways other than rotationally (e.g., on some defined grid or at defined locations spiraling outward or inward from a center or edge point of the coin, respectively). These and various other embodiments are all within a scope of the present invention. The specification and drawings are, accordingly, to be regarded in an illustrative rather than a restrictive sense.