License Plate Recognition Will Track You Down


Have you ever seen an old movie where bank robbers escape in their “get-away” car? If that movie happened today, police could use License Plate Recognition technology to determine that the car belonged to Clyde Barrow and search DMV records for where he lived with Bonnie Parker; unless the car had been stolen. Then, detectives may contact the rightful owner in that case. The Interesting Info about Kennzeichen reservieren.

LPR solutions are gaining popularity not only in the United States but throughout the world. For example, every country and state requires cars to have at least one license plate, which is a big plus. As a result, no transponders or transmitters are required. Instead, cameras capture the plate, and the software converts its characters into digital form, which the computer can then organize for matching to whatever database the application requires.

The police department has implemented LPR on red light cameras.

In addition, speed enforcement zones are used to reinforce compliance.

The federal, state, and municipal governments use it to monitor and limit automobile entry into secure facilities.

LPR is used to collect tolls and parking fees by both highway toll authorities and private parking facilities.

Finally, have you seen those repo men attaching a boot-locking device to a car’s wheel? Do you know how they know it belongs to someone who has fallen behind on their loan payments? LPR, indeed.

Since we are all subject to LPR, we should learn how it works. The technology underlying Optical Character Recognition is used in License Plate Recognition. OCR employs optical scanners and specialized software to recognize and digitize printed or handwritten characters. The following components are required for LPR systems:

IP Camcorder

The image must be clear for LPR, especially when capturing fast-moving vehicles. IP cameras are the preferred camera because they provide high resolution and definition. Depending on the application, the camera may be mounted to capture either the front or rear license plate, and in some cases, an additional camera may be used to capture the driver’s face.


Infrared lighting is the most effective because the human eye cannot detect it. As a result, neither the driver nor any covert applications will be startled. Furthermore, infrared lighting is compatible with most states’ retro-reflective license plates. It is also equally effective at night and during the day.

Grabber of Frames

The Frame Grabber is the conduit between the IP camera and the computer. It converts the analog signal from the camera into a digital stream of 1’s and 0’s that the computer can understand.


Any LPR system’s coordinator is the computer. It is typically a Windows or Linux PC that runs the LPR application and interfaces with any other systems the application may require.

LPR software consists of two steps: accessing the characters displayed on the license plate to recognize and extract them. Then, it reads the text of scanned images using software based on Optical Character Recognition technology.

As previously stated, License Plate Recognition is a subset of Optical Character Recognition. OCR technology makes use of software to read the text from scanned images. LPR software, in particular, reads and manipulates the license plate image, extracting information and transforming it into a format the computer can manipulate and organize for whatever application is required.

Use License Plate Recognition

Let us imagine that LPR is used to control parking facility access.

When a vehicle approaches a lift gate, the system is activated by driving over a magnetic loop.

Infrared illumination illuminates the targeted area, which is usually the front or back of the vehicle, including the license plate.

The approaching illuminated car is captured by the camera.

The Frame Grabber converts the camera signal so that the computer can read it.

Let us take a moment to look at the Frame Grabbers’ actions. First, it isolates the area containing the license plate. It accomplishes this by first determining the portion of the image containing the license plate using an algorithmic localizing function. To accomplish this, the algorithm first looks for a rectangle. As a result, the first step is to disregard the headlights, grills, and mirrors. Then, because a vehicle may have other rectangular surfaces, additional algorithms are used to detect license plate characteristics such as specific dimensions and the presence of background color.

With the area containing the license plate isolated, the software enhances the image, locates the license plate, isolates the string of characters, and identifies the fonts using its own set of algorithms.

Let us take another look at these initial algorithms and how they prepare the image for processing:

One algorithm compensates for any angular skew, allowing for precise sampling, correction, and recalculation for optimal size.

Another algorithm controls brightness and contrast.

Another separates the alphanumeric characters for OCR algorithms to process.

The OCR algorithms now convert the isolated string of characters into an alphanumeric text entry.

Finally, another set of complex algorithms verifies the alphanumeric information prescribed by the software application’s specific rule set.

Doesn’t it sound like a long and complicated process? It may be challenging, but believe it or not, it is not time-consuming. Instead, the algorithms perform their operations in milliseconds, with each one dependent on the one before it.


The results can be compared and added to a local database or sent over a network. If the sequence of characters from the license plate matches an entry on a list of authorized vehicles, a signal is sent to the gate, and it opens just long enough for the car to be admitted. If there is no match, the gate will remain closed.

Other applications are designed to prevent movement. For example, suppose the license plate characters on a parked car match an entry on a list of delinquent car loans, stolen vehicles, or traffic ticket violators. In that case, the car will be either immobilized by a boot or loaded onto a flatbed truck. In either case, the driver cannot drive for some time.

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