LPRS

de Capvidia

License Plate Reader System (LPRS) is a software application for real-time car license plates recognition. The LPRS analyses in the real time a video stream from camera or media storage (analogue or digital). The LPRS supports the common media format (avi) and video stream from camera or VCR (VideoForWindows). Recognized car license plates are stored into a database and can be verified against number of user-defined criteria.

LPRS performs:

• Finding number license plate in the view field
• Checking recognized license plate against license plates stored in the database
• Visual and sound notification in case the recognized license plate belongs to a stolen vehicle
• Query license plates database by: date, time, license plate number, status, etc.

LPRS key functions are:

• Real time video stream grabbing
• Video stream playback
• Movement detection
• License plate region detection
• License plate region tracking
• Selection of the best frames from the frame sequence
• Character recognition (OCR) on the frame sequence with license plate
• Statistical analysis of the recognition results
• Storing results in a database
• Database queries

The video control window includes a toolbar emulating the front VCR panel with function buttons controlling play, stop and pause functions. All buttons are operated by a simple mouse click. Scrolling slider provides fast access to data in recorded video stream. The user can view/recognize video frame by frame, save the video stream to a file and work with various databases (editing, making queries etc.).

License plate verification
The recognized license plate is checked against a list of license plates stored in the database. The LPRS application is build on the Microsoft Access database. The license plates numbers can be entered manually or automatically. Automatic entry is possible after a new license plate has been recognised by the LPRS system.

The user can specify for each license plate time interval (starting date – expiry date) in which the vehicle will be allowed to enter the guarded area. The car presence (in/out) in the guarded area is continuously monitored. The status for each license plate is always available for the operator. License plates can be assigned an identification parameter e.g. stolen car, not valid insurance, etc.

The authority of access and other identification parameters linked to a given license plate number are automatically verified. Depending on the verification results the following messages will appear in the status window:

• "The car is allowed to enter"
• "The car is not allowed to enter"
• "The car is stolen"

The message is linked with the sound signal.

Database
When license plate is recognised the arrival time is automatically attached and saved together with the image in the database records containing the recognized license plates (numbers), date, time stamp and the image of the license plate. The user can make a query from the database using a plate number, starting/ending date and time or status parameter.

LPRS in action
LPRS can be used for access control parking, garages, highway tollgates, boarder crossing, traffic control, etc. LPRS allows:

• Automatic registration of ingoing/outgoing cars with time stamps and images.
• Automatic comparing of vehicles using images from database.
• Automatic gate opening for vehicles with valid access.
• Search for stolen or search by police vehicles.

The LPRS system is designed to recognise various types of license plate used in different countries. LPRS can be easily adapted to specific requirements. For example, access permission can be modified. User can make statistical analysis on all vehicles entering and leaving guarded area. The analysis could be extended to identification of vehicle color, type and mark.

Recognition Engine
The LPRS system is based on Capvidia’s proprietary CVision Library containing over 500 specialised recognition functions. The LPRS uses the following functions:

• Processing functions supporting various data formats and image types
• Real time algorithms for generation of vector models (binarization, colour segmentation etc.)
• Unique and classic algorithms for object shape and object feature recognition
• Unique OCR (Optical Character Recognition) algorithms for characters recognition

Basic functions:

• detection of moving area
• creation of object contours
• finding license plate regions
• tracking license plate regions
• finding the character sequence
• calculation cells positions for each character
• characters recognition on the sequence of licence plate frames