Electro-Optical Technologies, Inc.

License Plate Identification/Recognition (LPI/R) Technology
Definition of Terms

Most currently-issued North American license plates utilize a reflective aluminum blank (12 × 6 inch • 304.8 × 152.4 mm) from the 3M Company (Saint Paul, Minnesota US). Although proper display of license plates on all motor vehicles (passenger cars, municipal vehicles, police units, fire engines, ambulances, taxicabs, limousines, hearses, trucks, vans, apportioned vehicles, transporters, motor homes, and buses) is centrally mandated, the program typically is administered by an agency at the state, provincial, commonwealth, republic, or territorial level.

The major objective of any LPI/R system is to interpret license plate alphanumerics. Along with the letters and numbers, many applications require the jurisdiction which issued the plate to be included with that information. The latter task is an onerous one because not all US States, for example, have the complete state name on the plate. Even when the name is present, usually it is too small to be captured by the image acquisition subsystem and, therefore, cannot be identified automatically. (One innovative approach is shown below.)

Sometimes, its distinctive features can be employed to help ascertain a plate’s political origin. Those are: font, syntax, number of character cells, special characters, excluded characters, and fabrication process.


 
Font
Font refers to an alphanumeric character’s shape and style (typeface). All plates are not made with the same font set. There are hundreds of fonts; a standard text on typesetting (“Linotron 202 Type Specimen Book One”, Southern New England Typographic Service, Inc., Hamden, Connecticut US, 1983) illustrates most.
Syntax
Syntax is any consistent ordering of characters, defined by systematic placement of letters and/or numbers. Horizontal character spacing also is a component of syntax. When fewer than the maximum number of characters appears on the plate, justification (flush left, flush right, centered, or full) is another attribute that can designate a particular issuing authority. With a “custom-ordered” or “personalized” plate (sometimes termed a “vanity” or “prestige” plate), syntactic rules and regulations generally do not apply. Though, in a majority of such cases, the plate’s character allowance (number of cells) is unchanged.
Character Cells
Every letter or number occupies a single cell. A cell nominally is three inches (76.0 mm) high; that measurement can vary slightly depending on the cell’s vertical placement. Unusual “truncated” character cells are only two inches (51.0 mm) in height. Each cell’s width and syntax (whether restricted to a letter or a number) act to determine the maximum number of cells which -- on North American plates -- is 8½.

Blank spaces, short hyphens, periods, and bullets are narrower than most characters and occupy a half-cell. Half-height characters can be stacked (in the vertical) so two are accommodated within a single cell. On occasion, three may be stacked vertically as is done by the State of Maryland, or diagonally as on some US Federal Government-issued plates. Even four diagonal characters are found on some State of Nevada dealer plates.

Special Characters
Special characters form a superset of the typical ones. Those may be a true letter (Ñ), numeral (Ø), symbol (&), or icon (like the “keystone” used on Commonwealth of Pennsylvania plates).
Excluded Characters
An excluded character is absent from the set of standard letters and numbers (A through Z; zero through nine). On State of Wyoming plates, for example, the letters “I”, “O”, and “Q” are not used when all other characters are numbers. The number “1” may not be substituted for the letter “I” nor the number “0” for the letter “O”. A four-character plate cannot contain more than two letters “W” nor two letters “M”.
Fabrication
“Embossing” is the most commonly encountered means of plate manufacture. A metal blank is placed face-down on an anvil and the character die is struck into it. After righting the plate, the letters and numbers appear in relief and are roll-coated.

“Incusing” (also called debossing) is similar to embossing except the plate is face-up on the anvil. Viewed from the front, the characters seem to be pressed inward. Plates from Vermont are incused.

In a single-step technique used by Alabama, Alaska, Arizona, Arkansas, Colorado, Delaware, the District of Columbia, Georgia, Hawaii, Idaho, Indiana, Iowa, Kansas, Kentucky, Maryland, Minnesota, Mississippi, Missouri, Montana, Nebraska, Nevada, New Jersey, New York, North Carolina, North Dakota, Ohio, Oklahoma, Oregon, Rhode Island, South Carolina, South Dakota, Tennessee, Texas, Washington, West Virginia, Wisconsin, Wyoming, the US Federal Government, and the Department of State (on some older issues), the plate is not hammered at all. A graphic lamination process applies the materials so foreground characters remain flush with the background. Other locales are transitioning to the newer methodology.

E-Plates

Digital license plates (also know as electronic license plates) are begining to appear. Although “road-legal” in all fifty states, they currently only are offered for Arizona, California, and Michigan. The principle manufacturer, Reviver (Granite Bay, California US), has committed to expansion into Colorado, Florida, Georgia, Illinois, Pennsylvania, Texas, and others.

Varieties
Diversity among US plates is dramatic. Frequently, different plate designs are furnished within the same jurisdiction. An elective plate style is referred to as a variety. (The phrases “special” or “special design” are synonymous.) Numerous varieties, for example, are offered by the State of Florida. The vehicle registrant may accept the “standard-issue” plate or select an alternate (such as local interest or Alma Mater commemoratives, bicentennial issues, etc.), customarily at extra cost. Most optional varieties retain the font from the standard issue; however, there are exceptions.
Applications
LPI/R technology is finding novel uses in an enormous yet continually growing number of scenarios; spanning the obvious in law enforcement to more pedestrian but nonetheless exciting applications. As the number of license plates on North American roadways reaches staggering proportions, it has become imperative to “read” each and every character on the plate. For most applications, no longer is there the luxury of ignoring half-cell or half-height characters. Indeed, difficult-to-image, small letters, numbers, and special characters are showing up with ever greater frequency. Here is one vendor’s impressive solution:


 
Optimizing License Plate Design for Intelligent Character Recognition
The graphic lamination process affords the opportunity to specify retro-reflectivity of foreground versus background, individually. A partially-reflective plate can be manufactured where the background -- made of 3M’s Scotchlite® Reflective Sheeting -- is retro-reflective, while the alphanumerics’ pigment is absorptive. Digital license plate technology supports custom background graphics and a rich palette of foreground colors. When illuminated for machine readability (in near-infrared, for example), the foreground becomes highly contrasted against a uniform background, shadows virtually are non-existent (because the plate is unembossed), and alphanumerics are crisp, clear, and well-defined.
Full-Color Image 
Monochrome Image 
Infrared Image (simulated) 
       Segmented Image 

Commercial Suppliers of Core LPI/R Technology

The following fifty-seven companies are manufacturers/vendors (versus system integrators or third party resellers) of software, hardware, and firmware-based recognition engines. They are listed at the sole discretion of E-OTEK. Application-specific product endorsements neither are expressed nor implied as each potential use is individual and unique in its requirements. (Click a plate icon for a high-resolution image.)
 

AZ license plate
 

  • Abstract Computing International BV (Weesp Netherlands)
  • A.R. Hungary, Inc. (Budapest Hungary)
  • Asia Vision Technology Ltd. (Hong Kong China)
  • Basir Technology (Tehran Iran)AL license plate
  • BIT Raèunalniški Inženiring DOO (Ljubljana Slovenia)
  • Carrida Technologies GmbH (Ettlinger Germany)
  • Cyclops Technologies, Inc. (Oldsmar, Florida US)
  • Digitek, DOO (Ljubljana Slovenia)
  • DTK Software (Riga Latvia)FL license plate
  • ekin Europe GmbH (Stuttgart Germany)
  • EngiNe Srl (Rapolano Terme Italy)
  • Gatekeeper, Inc. (Sterling, Virginia US)
  • Genetec Inc./AutoVu (Montréal, Québec Canada)
  • GeoVision Inc. (Neihu, Taipei Taiwan)NC license plate
  • Inex Technologies Inc. (Lyndhurst, New Jersey US)
  • InPeg Company, Ltd. (Busan Korea)
  • Intelligent Security Systems International, Inc. (Woodbridge, New Jersey US)
  • IntelliVision (San Jose, California US)
  • Intertraff Srl (Manduria Italy)MT license plate
  • Jenoptik Traffic Solutions UK Ltd (Frimley, Surrey  England)
  • Keon-A Information Technology Company, Ltd. (Seoul Korea)
  • Kria Srl (Desio Italy)
  • Lector Vision (Alcobendas Spain)
  • Leonardo Company (Brewster, New York US)FL license plate
  • Macq Électronique (Brussels Belgium)
  • Milestone Systems A/S (Brøndby Denmark)
  • Motorola Solutions Inc./Vigilant Video (Livermore, California US)
  • NDI Technologies, Inc. (Nantwich, Cheshire England • Winter Springs, Florida US)
  • Nedap NV (Groenlo Netherlands)FL license plate
  • Neology Inc./PIPS Technology (San Diego, California US)
  • Neural Labs SL (Cerdanyola del Valles Spain)
  • OmniQ Corporation (Salt Lake City, Utah US)
  • Optasia Systems Pte Ltd. (Singapore)
  • Parkingware BV (Gieterveen Netherlands)SD license plate
  • Perceptics, LLC (Knoxville, Tennessee US)
  • Planet Intelligent Systems Inc. (El Dorado Hills, California US)
  • Ponfac S/A (São Leopoldo, Rio Grande do Sul Brazil)
  • Q-Free ASA/Dacolian (Beilen Netherlands)
  • QRO Solutions Ltd (Islip, Northhamptonshire England)TN license plate
  • Quercus Technologies (Reus Spain)
  • Recogniform Technologies SpA (Rende Italy)
  • reCognitec GmbH (Kleinmachnow Germany)
  • Recognition Technologies Co. Ltd. (Moscow Russia)
  • Rekor Systems, Inc. (Columbia, Maryland US)WI license plate
  • RoboVu, LLC (Phoenix, Arizona US)
  • Sensebit AB (Tampere Finland)
  • Senstar Corporation (Waterloo, Ontario Canada)
  • Sodi Scientifica SpA (Settimello di Calenzano Italy)
  • Survision SAS (Nanterre France)VA license plate
  • TagMaster AB (Kista Sweden • Stevenage, Hertfordshire England)
  • Tomahawk Technologies, Inc. (Carleton Place, Ontario Canada)
  • Video-2-Data (Pty) Ltd. (Boksburg, Gauteng South Africa)
  • Videocom Security Ltd. (Waltham Abbey, Essex England)
  • Videofit Ltd. (Cheltenham, Gloucestershire England)WV license plate
  • Visec International (Cape Town South Africa)
  • Vitronic Machine Vision Ltd. (Louisville, Kentucky US)
  • 4Sight Imaging (Bolton, Lancashire England)
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    We hope the foregoing provides meaningful insight into the many complexities encountered when automating video-based LPI/R. It would be our sincere pleasure to discuss the details of your project. Please contact us for a copy of our complete statement of capabilities and qualifications.
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    Electro-Optical Technologies, Inc.
    1960 Gallows Road, Suite 220
    Vienna, Virginia 22182-3827-70
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