License Plate Recognition Camera also known as ANPR—captures and digitizes images of vehicle plates. It translates numbers and letters into digital data that can be analyzed during an incident investigation.
It’s a great way to fill in security gaps and bolster evidence when dealing with an incident. Ensure your cameras work well in different weather conditions by choosing waterproof devices.
License Plate Recognition Cameras are specialized security cameras engineered to capture high-quality images of license plates in a wide variety of environments. They use advanced imaging technology and OCR software to translate captured images into readable text, making them ideal for law enforcement, parking management, and property protection applications.
These cameras are designed to operate in challenging conditions such as varying lighting, vehicle speed, and angles of view. They also come with features that address the specific challenges of capturing license plates. They are able to overcome these challenges through advanced technology, high-resolution image quality, and the use of infrared illumination.
A key feature of these cameras is their ability to recognize a vehicle’s license plate even in low-light conditions. They can achieve this through the use of a wide range of image processing technologies, including wide dynamic range (WDR) and adjustable shutter speed. These features can be used to increase the accuracy of captures in low-light situations while also reducing blurring.
Another way that these cameras can improve their performance is through the use of advanced OCR algorithms. This helps them overcome challenges such as display distortion and glare. This can be especially useful when attempting to read license plates in a dark environment or when there is a lot of reflected light from other vehicles on the road.
Finally, these cameras can be configured to filter out specific characters or shapes that may interfere with the recognition of a license plate. This can prevent the camera from registering false positives and reduce the amount of time that it spends on a single vehicle.
A common application of this technology is at a choke point, where vehicles must slow down or stop to pass through. The cameras can be adjusted to focus on the area where the plate is expected to land for best results. These choke points can be traffic lights, parking lot entrances, or one-way roads.
Optical Character Recognition (OCR) Software
OCR software is designed to recognize text within images, converting them into searchable data. This allows businesses to create fully searchable knowledge archives, automate data entry and reduce human error. A number of different OCR software programs are available, some based on matrix matching and others utilizing neural networks. Some offer dictionary support, which simplifies further analysis of recognition results.
The first step in OCR involves image preprocessing, which normalizes lighting and optimizes a document for better text extraction. This process can also focus the software’s attention on specific features, reducing the number of variables to address in subsequent steps. Some OCR programs allow users to set “confidence rates” for recognition, indicating when a particular character has a high likelihood of being correct.
Next, a glyph is isolated from the rest of the image and compared to stored patterns in a database. The result is a list of possible matches, with a confidence rating for each match. This is called feature detection, and is a type of machine learning algorithm. Support vector machines are another popular class of algorithms for OCR, which use mathematical models to predict the probability of a particular pixel having a certain value.
Once the feature detection process is complete, the OCR program can convert a scanned image into an editable text file. Depending on the software suite, this may be in the form of HTML, XML or a dedicated text format like ALTO or hOCR. In some cases, a text file can be output to a printer for further processing, or sent to a cloud-based repository for future analysis and access.
A key benefit of OCR is the speed and ease with which it can be used. By removing manual data entry, it can significantly improve a business’s productivity. However, it is important to remember that no OCR system can guarantee 100% accuracy, and the resulting data will still require some human input in order to be fully useful. OCR can greatly reduce the amount of time and resources that would be required for a person to manually enter the same data, but it will not replace all manual labor.
Infrared Light Sources
Many ANPR and LPR systems use infrared illumination to provide additional lighting for the camera. Unlike visible light, the infrared light used by these illuminators is not reflected off of vehicles or their windows and is therefore much more effective for capturing images of license plates. This technology helps improve the ability of these systems to capture and read license plate numbers in low-light conditions, reducing the need for human intervention and increasing the accuracy and reliability of the results.
As the light from the illuminators passes through the lens of the camera, it is captured on the sensor and converted to usable digital data. This data is then processed by the software to identify the letters and numbers in the license plate image. The software then translates these characters into a searchable database entry that can be used for vehicle identification and tracking purposes. This process can be accelerated by using high-performance computing (HPC) to process the large volumes of data generated by these systems.
The quality of an image depends on a number of factors, including the camera resolution, angle of view, and lighting conditions. The ability of a system to capture clear and accurate images can also be impacted by dirt on the plates or glare caused by the sun or headlights. To ensure that the highest levels of accuracy are achieved, ANPR and LPR cameras should be positioned in an optimal location with adequate lighting, and with sufficient zoom capabilities to allow for a close-up of the plates.
Using advanced software and image processing techniques, modern ANPR and LPR systems can accurately read over 95% of the time, even in challenging conditions such as poor weather or dark lighting. This makes these systems a powerful tool for ensuring the safety and security of people, vehicles, and infrastructure.
In addition, integrating ANPR and LPR technology with other surveillance and monitoring systems can help authorities obtain a holistic view of security incidents and streamline their response. For example, combining this type of information with visual footage or biometrics can enable authorities to track and quickly respond to vehicles associated with stolen goods or wanted individuals.
Angle of View
The angle of view is critical to the performance of any ANPR system. The camera should be positioned so that the license plate is able to be seen at an angle less than 30 degrees. If the camera is mounted at an angle greater than this, it can be difficult to read the license plate text and will require specialized software to correct the image. It may also be necessary to use a varifocal lens camera, which allows the operator to adjust the field of view and zoom as needed.
The ideal location for an ANPR camera is a choke point where vehicles are forced to slow down or stop, such as parking lot entrances and toll booths. In addition to reducing the speed of traffic, choke points also improve image quality by forcing vehicles to approach the camera at a slower speed which makes it easier for the camera to capture a clear image.
Most LPR cameras are either high resolution bullet or PTZ (pan-tilt-zoom) cameras with a fixed view and powerful zoom capabilities to capture images of license plates from a distance. They are typically affixed to a pole or mounted to the ceiling of an area where they are to be used for ANPR purposes. The majority of these cameras are configured to record in 1080p HD.
Some cameras may be equipped with a special infrared light unit which is useful for capturing license plates at nighttime or in low-light conditions. This is especially helpful if the camera is located on a highway, where the plate numbers can be obscured by fog and dirt.
Another application for license plate recognition systems is to track a known suspect’s vehicle. Whether it’s a disgruntled former employee or a criminal who has been publicly identified as a threat, license plate recognition technology can help law enforcement agencies and businesses keep an eye on these vehicles and quickly identify them when they are spotted. This can help reduce crime and protect people and property. In many cases, these types of technologies can even prevent crimes before they happen.